Abstract:
A lubricant supply system for a marine engine is provided with a lubricant conduit that is formed within an engine block in close proximity to a coolant conduit. The coolant conduit is extended, by a bulge, in a direction toward the lubricant conduit in order to reduce the distance through which heat must travel through the base material of the engine block to cool the lubricant flowing through the lubricant conduit by the water flowing through the coolant conduit.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is generally related to an oil supply system for a marine engine and, more particularly, to a marine engine with a main lubricant conduit, or gallery, which is cooled by its proximity to a water conduit of the engine. 
     2. Description of the Related Art 
     Many different techniques have been used to reduce the operating temperature of lubricating oil used in a marine engine. Typically, these cooling techniques relate to the use of cooling water to reduce the temperature of an oil sump. 
     U.S. Pat. No. 6,619,274, which issued to Miyashita et al. on Sep. 16, 2003, describes an outboard engine intake air cooling system. An air intake cooling system for an outboard motor is equipped with a V-type engine is described. In one embodiment, the air intake cooling system has an air intake manifold and a water-cooling passageway positioned in the air intake manifold for cooling air in the air intake manifold. This system further has a water sleeve for cooling a main oil reservoir located inside the V-type engine, the water sleeve being positioned next to the main oil reservoir and connected to the water cooling passageway. 
     U.S. Pat. No. 6,868,819, which issued to Saiga et al. on Mar. 22, 2005, describes a lubricating system for an outboard motor. In one embodiment, the lubricating system has an oil pump positioned near the bottom of the engine, the oil pump driven by an oil pump rotor that is positioned at a connection between the crankshaft and an engine driven shaft. The oil pump is linked to the crankshaft. The system further includes a cam shaft driving mechanism for transmitting the rotation of the crankshaft to a propulsion device. The cam shaft driving mechanism is also positioned at the connection between the crankshaft and the driveshaft and is also linked to the crankshaft. The lubrication system also has a main oil tank for storing lubricating oil circulated by the oil pump and an engine cooling water passageway positioned next to the main oil tank. Another element of this embodiment of the lubricating system is a filter mounting base positioned on an outer wall of the cylinder blocks. The system also has oil passageways positioned at the bottom of the cylinder blocks for distributing the oil. 
     U.S. Pat. No. 6,834,635, which issued to Yomo et al. on Dec. 28, 2004, describes an outboard motor which includes an engine, an engine holder disposed below the engine, a driveshaft housing which is disposed below the engine holder, an intake device including an intake manifold disposed to a side surface of the engine, a lubricant supply device for supplying lubricant oil to the engine, an oil filter disposed below the intake manifold, and an oil cooler arranged below the intake manifold and between the engine and the oil filter. The oil cooler includes a casing and a cooler body disposed inside the casing and the casing is formed with a cooling water flowing-in union and a cooling water flowing-out union disposed in correspondence with the cooling water flowing-in union. 
     U.S. Pat. No. 6,358,108, which issued to Murata et al. on Mar. 19, 2002, describes an outboard motor which includes a first case and a second case disposed below the first case. The first case houses therein an oil pan and an upper part of a driveshaft. Within the oil pan, engine oil is held. The second case has its upper edge portion coupled to a lower edge portion of the first case. The arrangement prevents the oil pan from being affected by heat of the exhaust gas. Thus it becomes possible to prevent the engine oil held within the oil pan from increasing in temperature. 
     U.S. Pat. No. 6,067,951, which issued to Kitajima on May 30, 2000, describes an engine for an outboard motor. The cooling and exhaust systems for the engine are formed with a minimum number of components and ceiling joints. The flow of cooling the water to and from the engine is controlled so that the exhaust gas interchange area between the powerhead and the driveshaft housing will be well cooled, as will the oil reservoir for the engine and the oil returned to it. 
     U.S. Pat. No. 6,305,999, which issued to Toyama et al. on Oct. 23, 2001, describes an outboard motor that includes an engine holder, an engine which is disposed above the engine holder in a state of the outboard motor mounted to a hull in which a crankshaft extends substantially perpendicularly, and an oil pan disposed below the engine holder. A cooling water passage is formed in the oil pan and a driveshaft housing to guide the cooling water pumped up by the water pump to the engine. A relief valve is disposed on the way of the cooling water passage so as to discharge the cooling water into the exhaust chamber. 
     U.S. Pat. No. 6,416,372, which issued to Nozue on Jul. 9, 2002, describes an outboard motor cooling system. It includes an improved construction for enhancing cooling of the lubrication system. An oil pan depends from an engine of the outboard motor and into a driveshaft housing. A periphery coolant jacket is provided around the oil pan. A water pool is defined between the oil pan and the driveshaft housing. An exhaust manifold passes through in a hollow of the oil pan and a water curtain is defined between the hollow wall and the exhaust manifold. An upstanding water passage is also disposed through the oil pan. The oil pan therefore is sufficiently cooled. 
     The patents described above are hereby expressly incorporated by reference in the description of the present invention. 
     It would be beneficial if a system could be provided that provides additional cooling to the lubricating oil of an outboard motor engine by other than the traditional methods which utilize oil coolers or cooling systems which cool the oil while it is within the oil sump of the outboard motor. 
     SUMMARY OF THE INVENTION 
     A marine engine, made in accordance with a preferred embodiment of the present invention, comprises a lubricant conduit and a coolant conduit. The lubricant conduit is formed within the engine and configured to conduct a flow of lubricant between an oil sump and at least one lubricated surface of the engine. Typically, the lubricant conduit conducts lubricating oil from the oil sump to the bearings which support a crankshaft of the engine. The lubricant conduit has an internal dimension extending from a first point on an internal surface of the lubricant conduit to a second point on an opposite internal surface of the lubricant conduit. The coolant conduit is formed within the engine and configured to conduct a flow of coolant through the engine and in thermal communication with heat producing portions of the engine. The lubricant conduit is spaced apart from the coolant conduit by a distance which is less than the magnitude of the internal dimension of the coolant conduit. In a particularly preferred embodiment of the present invention, the lubricant conduit is spaced apart from the coolant conduit by a distance which is less than the magnitude of the internal dimension. 
     A preferred embodiment of the present invention can further comprise an internal bulge formed in the coolant conduit at a region of the engine which the bulge reduces the distance by which the lubricant and coolant conduits are spaced apart. The bulge extends, in a direction generally parallel to a central axis of the lubricant conduit, a distance which is at least five times the magnitude of the internal dimension of the lubricant conduit. In a particularly preferred embodiment of the present invention, the bulge extends a distance which is at least ten times the magnitude of the internal dimension of the lubricant conduit. 
     In a preferred embodiment of the present invention, it further comprises a lubricant sump and a lubricant pump. The lubricant pump is connected in fluid communication between the lubricant conduit and the lubricant sump to cause the lubricant to flow from the lubricant sump into and through the lubricant conduit. 
     In a particularly preferred embodiment of the present invention, the coolant is water and the lubricant conduit has a generally circular cross section. In an alternative embodiment of the present invention, the lubricant conduit can have a cross section defined by a major axis and a minor axis. In such an embodiment, the internal dimension of the lubricant conduit is the major axis in a preferred embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be more fully and completely understood from a reading of the description of the preferred embodiment in conjunction with the drawings, in which: 
         FIG. 1  is a sectional view of a marine engine; 
         FIG. 2  is a side sectional view of the marine engine; 
         FIG. 3  is an enlarged view of a region of the marine engine where a coolant conduit is most proximate to a lubricant; and 
         FIG. 4  is a geometric representation of a hypothetical cross section of a lubricant conduit. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Throughout the description of the preferred embodiment of the present invention, like components will be identified by like reference numerals. 
       FIG. 1  shows a section view taken through an engine block  10  of a marine engine. For purposes of reference, the opening identified by reference numeral  12  is the location where a crankshaft is supported for rotation, by a plurality of bearings, about an axis  14 . Reference numeral  16  identifies a cylinder opening of the engine. A cylinder head, which is not shown in  FIG. 1 , is attachable to surface  18 . In addition, a crank case cover, or bed plate, is attachable to surface  19 . Reference numeral  20  identifies an exhaust passage which extends in a generally vertical direction along one side of the engine  10 . A coolant jacket  24  surrounds the exhaust passage  20  in order to remove heat from the exhaust conduit. A main oil gallery  26  extends in a generally vertical direction through the body of the engine  10  to conduct a flow of liquid lubricant to various lubricated surfaces, such as bearings, within the structure of the engine  10 . 
     The water jacket  24  is extended, as shown in  FIG. 1 , to provide a bulge  27 . The bulge  27  extends from the water jacket  24  in a direction toward the main oil gallery  26 . As will be described in greater detail below, the lubricant conduit, or oil gallery  26 , is spaced apart from the coolant conduit, or water jacket  24 , by a distance D which is less than the magnitude of an internal dimension X of the lubricant conduit  26 . 
     With continued reference to  FIG. 1 , the lubricant conduit  26 , or main oil gallery, is shown as being generally circular in cross section. As a result, internal dimension X is the diameter of that cross section. However, it should be clearly understood that the cross section of the lubricant conduit  26  need not be circular. 
     The bulge  27  is provided to decrease the magnitude of the distance D in order to improve the heat transfer characteristics of the arrangement. With a reduced magnitude of the distance D, heat from the oil flowing through the lubricant conduit  26  can be absorbed more effectively by coolant flowing through the coolant conduit  24 . 
       FIG. 2  shows a side view of the engine  10 . The lubricant conduit  26  is shown extending vertically through the body of the engine block. The coolant conduit  24  is shown with its bulge  27  extending from the coolant conduit  24  in a direction toward the lubricant conduit  26 . For purposes of reference, the bulge  27  is illustrated in  FIG. 2  as extending for a distance Y in a direction that is generally parallel to a central axis  30  of the lubricant conduit  26 . The wall  34  between the lubricant conduit  26 , or main oil gallery, and the coolant conduit  24 , or water jacket, is thinner in the region of the bulge  27  for the distance identified by reference letter Y in  FIG. 2 . In this region, heat transfer between the oil flowing through the lubricant conduit  26  and the water flowing through the coolant conduit  24  is significantly improved. 
     With continued reference to  FIG. 2 , a lubricant pump  40 , a lubricant sump  42 , and a lubricant filter  44  are shown schematically in relation to the engine  10 . These components are illustrated schematically in  FIG. 2  because the section view of the engine  10  in  FIG. 2  would not otherwise show them. It should be understood that the lubricant pump  40  would normally be located within the cavity identified by reference numeral  48 . The lubricant pump  40  draws liquid lubricant  50  from the lubricant sump  42  and causes the liquid lubricant to flow through the filter  44  and into a location within the lubricant conduit  26  as shown in  FIG. 2 . The lubricant  50 , such as lubricating oil, then flows through the lubricant conduit  26  to various regions of the engine where lubricated surfaces exist, such as the bearings associated with the crankshaft in region  12 , as described above in conjunction with  FIG. 1 . 
       FIG. 3  is an enlarged view of the region of an engine  10  where the lubricant conduit  26  and the coolant conduit  24  are nearest to each other. The distance between the bulge  27  and the lubricant conduit  26  is identified by reference letter D in  FIG. 3 . It should be noted that the lubricant conduit  26 , or main oil gallery, is illustrated as having an oval cross section in  FIG. 3 . This is different than the generally circular cross section shown in  FIG. 1 . The cross sectional shape of the lubricant conduit  26  is not limiting to the present invention. 
     With continued reference to  FIG. 3 , the oval shape of the lubricant conduit  26  is shown having a major axis Z and a minor axis N. When reference is made to the relative magnitudes of the internal dimension of the lubricant conduit  26  and the distance D between the lubricant conduit  26  and the coolant conduit  24 , that internal dimension is the major axis Z. 
       FIG. 4  is a schematic representation of an oval shape that is used herein for purposes of discussing the various dimensions used to describe the present invention. As described above, the lubricant conduit  26  is used to direct a flow of liquid lubricant through the structure of an engine block. Reference numeral  50  in  FIG. 4  identifies an internal surface of the lubricant conduit  26 . With reference to the major axis Z, it extends from a first point  51  on the internal surface  50  to a second point  52  on an opposite internal surface of the lubricant conduit  26 . The internal dimension Z is described in terms of these first and second points,  51  and  52 , on opposite portions of the internal surface  50 . This is intended to convey the concept that the internal dimension Z can represent the maximum distance represented by the various dimensions of the cross sectional shape. Alternately, the internal dimension can be the dimension identified by reference letter N in  FIG. 4 . This extends between a first point  61  and a second  62 . It should be understood that the lubricant conduit  26 , in alternate embodiments of the present invention, can be virtually any shape. These include circular cross sections, oval-shaped cross sections, rectangular cross sections, or any other shape that is suitable to convey liquid lubricant through the body of an engine block and distribute that liquid lubricant to various lubricated surfaces. 
     With continued reference to  FIGS. 1–4 , it should be noted that the lubricant conduit  26  is a cavity formed through the body or structure of the engine block itself. It is not a conduit that is attached to or added to the engine  10 . Instead, it is formed directly through the structure of the engine block. In a typical application of the present invention, the lubricant conduit  26  is formed during the casting process that forms the engine block. This casting process, in a typical application of the present invention, is a lost foam casting process. However, it should be understood that the internal cavity of the lubricant conduit  26  can be formed through the structure of the engine block in alternate ways. The manufacturing technique used to produce the lubricant conduit  26  within the structure of the engine block is not limiting to the present invention. 
     With continued reference to  FIGS. 1–4 , it can be seen that a preferred embodiment of the present invention provides a marine engine that comprises a lubricant conduit  26  that is formed within the engine  10  and configured to conduct a flow of lubricant  50  through the engine  10 . The lubricant conduit  26  has an internal dimension, such as major axis Z, which extends between two points on the internal surface  50  of the lubricant conduit. In a particularly preferred embodiment of the present invention, the internal dimension is the maximum dimension extending across the lubricant conduit. A coolant conduit  24  is formed within the engine  10  and configured to conduct a flow of coolant through the engine and in thermal communication with heat producing portions such as cylinders  16 , of the engine  10 . The lubricant conduit  26  is spaced apart from the coolant conduit  24  by a distance D which is less than the magnitude of the internal dimension X, as illustrated in  FIG. 1 . 
     The lubricant conduit  26  can be spaced apart from the coolant conduit  24  by a distance D which is less than the magnitude of the internal dimension X in certain embodiments in which particularly improved heat transfer is required between the water flowing through the coolant conduit  24  and the oil flowing through the lubricant conduit  26 . An internal bulge  27  is formed in the coolant conduit  24  at a region of the engine  10  at which the bulge reduces the distance D by which the lubricant and coolant conduits,  26  and  24 , are spaced apart. The bulge  27  extends, in a direction generally parallel to a central axis  30  of the lubricant conduit  26 , a distance Y which is at least five times the magnitude of the internal dimension X of the lubricant conduit  26  in a preferred embodiment of the present invention. In a particularly preferred embodiment, in which significant heat transfer improvement is required, the distance Y can be at least ten times the magnitude of the internal dimension X. In a particularly preferred embodiment of the present invention, it further comprises a lubricant sump  42  and a lubricant pump  40 . The lubricant pump  40  is connected in fluid communication between the lubricant conduit  26  and the lubricant sump  42  to cause the lubricant  50  to flow from the lubricant sump  42  into and through the lubricant conduit  26 . In a typical application of the present invention, the coolant flowing through the coolant conduit  24  is water. The lubricant conduit  26  typically has a generally circular cross section. However, the lubricant conduit  26  can have a cross section defined by a major axis Z and a minor axis N. The internal dimension, identified by reference letter X in  FIG. 1 , can be the major axis Z. 
     Although the present invention has been described in particular detail and illustrated to show a preferred embodiment, it should be understood that alternative embodiments are also within its scope.