Abstract:
An outboard motor is provided with an air duct located within the cavity of a cowl of an outboard motor. The air duct defines a chamber within it in association with first and second openings that allow heated air to flow, through the creation of convection currents, out of the engine compartment under a cowl. This convection flow removes heat from fuel system components and reduces the likelihood that “vapor lock” will occur subsequent to the use of an internal combustion engine that is followed by turning the engine off.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is generally related to an air ventilation system for an outboard motor and, more particularly, to a ventilation system that utilizes an air duct to conduct air in thermal communication with selected fuel supply system components, particularly when the engine is turned off following operation for a period of time sufficient to raise the temperature of portions of the engine. 
     2. Description of the Prior Art 
     Air ventilation systems for outboard motors of various types are well known to those skilled in the art. 
     U.S. Pat. No. 4,326,600, which issued to Okazaki et al on Apr. 27, 1982, describes an intake silencer for an outboard motor. The outboard motor includes a cowling with a cavity that receives a carburetor that supplies the engine with an air/fuel mixture. The carburetor has an air intake port. An air intake passage connects to this port and bends partway around the carburetor. A resonance chamber communicates with the air intake passage and faces the carburetor to attenuate the noise from the carburetor intake port. 
     U.S. Pat. No. 4,952,180, which issued to Watanabe et al on Aug. 28, 1990, describes a cowling for an outboard motor. Two embodiments of the protective cowlings for the power head of an outboard motor that form both forwardly and inwardly facing air inlet passages are described. The forwardly and rearwardly facing air inlet passages are configures to ensure adequate air induction to the engine. The forwardly facing air inlet opening is located so as to avoid water being able to enter into the interior of the protective cowling and into the engine induction system. 
     U.S. Pat. No. 5,176,551, which issued to Blanchard et al on Jan. 5, 1993, describes an arrangement for supplying combustion air to an outboard motor. The marine apparatus comprises a boat including a wall extending generally in the fore and aft direction and having therein an air outlet opening. It further comprises a propulsion unit mounted on the boat and including a propeller shaft and an engine drivingly connected to the propeller shaft. A cover surrounds the engine and has therein an air inlet opening with a duct communicating between the air outlet opening and the air inlet opening. 
     U.S. Pat. No. 5,181,871, which issued to Hiraoka et al at Jan. 26, 1993, describes a suctioned air introducing system for an outboard motor. The device provides an improved cowling and air inlet arrangement for the powerhead of an outboard motor, having an internal combustion engine including an induction system, which prevents water from splashing upon the outer surface of the engine contained therein. Damage to the engine due to corrosion, or other phenomena is avoided, since the arrangement of the invention does not permit water to impinge upon the engine. 
     U.S. Pat. No. 5,445,547, which issued to Furukawa on Aug. 29, 1995, describes an outboard motor which has an engine compartment covered by an engine cover at its top portion and has an engine disposed within the engine compartment with its crankshaft directed in the vertical direction. The charging efficiency of the engine is improved with a simple structure and an shielding property of the entire surrounding of the engine is also enhanced. A suction chamber communicating with an intake section of the engine is disposed on a surface other than the top surface of the engine and on one side of the inside of the engine compartment, an air intake portion is provided in the engine cover at a position close to the other side of the inside of the engine compartment, an air exhaust port is provided in the engine cover, and a duct is provided within the engine compartment for leading air from the air intake port towards the suction chamber while making a detour to avoid a route above the engine. 
     U.S. Pat. No. 5,899,778, which issued to Hiraoka et al on May 4, 1999, describes an outboard motor induction system. An induction system is of the type having a water propulsion device powered by an internal combustion engine positioned within an engine compartment defined by a cowling. The induction system includes a cover extending over a top end of the engine. The cover defines an air duct leading from an intake chamber defined by the cowling to an intake pipe of the air intake system of the engine. The cover also defines an air duct in communication with the engine compartment and leading to an exhaust chamber defined by the cowling. A pair of intake ports lead through a cover of the cowling form the intake chamber, and an exhaust port leads through the cover from the exhaust chamber. The intake ports are positioned forward of the exhaust port when considering the forward movement of a watercraft which is powered by the motor. 
     U.S. Pat. No. 5,937,818, which issued to Kawai et al on Aug. 17, 1999, describes a ventilation system for an outboard motor. The ventilating system has a water propulsion device and an internal combustion engine positioned in a cowling, the engine having an output shaft arranged to drive the water propulsion device. The ventilating system includes an air inlet in the cowling which permits air to flow into the engine compartment in which the engine is positioned, and an exhaust port positioned in the cowling. The system also includes a mechanism for drawing air through the inlet into the compartment and expelling air out of the compartment through the exhaust port after the engine has stopped. 
     U.S. Pat. No. 5,938,491, which issued to Kawai et al on Aug. 17, 1999, describes a cowling air inlet for an outboard motor. The protective cowling arrangement defines an air inlet opening for an outboard motor that facilitates the ingestion of large amounts of air at low velocity. This aids in the assurance that water is not ingested into the engine. The configuration of the inlet opening is such that the water that is separated by the inlet system can easily flow away from the inlet opening and also the water that collects on the housing surfaces can be easily separated and will drain away from the actual inlet openings into the interior of the cowling. 
     U.S. Pat. No. 5,996,546, which issued to Kollmann et al on Dec. 7, 1999, discloses an integrated flywheel cover and air conduit passages. A cover for an outboard motor is provided to protect an operator from a flywheel. The cover is disposed under the cowl of the outboard motor. The cover is made of a generally rigid material, such as plastic, with first and second sheets being associated together to form conduits with openings extending therefrom. In one particular embodiment, one of the openings is shaped to receive an inlet of a compressor and this provides a positioning aid in attaching the cover to the engine. This device eliminates the need for flexible hoses and accomplishes two tasks with one component. It provides air conduits for the air passing through the cover and it provides a generally rigid means for locating the proper location of the cover. 
     U.S. Pat. No. 6,024,616, which issued to Takayanagi on Feb. 15, 2000, describes an engine cover for an outboard motor. The outboard motor includes an engine which is covered by an engine cover which is formed with a cylindrical air suction port having an opening open to an upper surface of the engine cover in a state of the outboard motor mounted to a hull, and a portion of an opening area of the opening is covered by a lid member which is formed to a rear edge portion of the opening. 
     Many different types of cowls, for covering the engine of an outboard motor, are well known to those skilled in the art. Typically, the cowls are provided with one or more openings that allow air to flow into the engine compartment of the outboard motor from the ambient air surrounding the outboard motor. This air is used during the combustion processes of the engine and also provides a cooling effect. Some cowls that are known to those skilled in the art also provide for ventilation openings that facilitate the removal of heat from the internal portions under the cowl, particularly after the engine is turned off. 
     When outboard motors are operated and then turned off, the natural characteristics of most outboard motors cause heat from the internal combustion engine to flow by convection and conduction toward components of the fuel delivery system of the engine. This heat transfer process, after the flow of internal cooling water stops, raises the temperature of the fuel system components and can lead to the deleterious situation referred to as “vapor lock” that is caused by the boiling or vaporization of liquid fuel within the components and conduits of the fuel system. This problem can continue to exist long after the engine is turned off and it can adversely affect the ability of the engine to start. Typically, this condition referred to as “vapor lock” is only alleviated after the engine is cooled to a temperature low enough to condense the gaseous fuel back into a liquid state. 
     It would therefore be significantly beneficial if an inexpensive and simple method could be provided for facilitating the cooling of an internal combustion engine subsequent to the engine being turned off. In addition, it would be significantly beneficial if an outboard motor could be provided in which natural ventilation is available to quickly remove heat from the fuel system components of the engine of an outboard motor. 
     SUMMARY OF THE INVENTION 
     An outboard motor ventilation system made in accordance with the present invention comprises an engine and a cowl having a cavity therein, with the engine being disposed within the cavity. It further comprises a fuel system component that is connected in fluid communication with the engine in order to supply fuel to one or more combustion chambers of the engine. The fuel system component is external from the engine block itself and is disposed under the cowl. The present invention further comprises an air duct disposed within the cavity of the cowl. The air duct has a first opening and a second opening. The walls of the air duct define a chamber, within the body of the air duct, and the chamber is disposed in fluid communication between the first and second openings. The fuel system component is disposed at least partially within the chamber of the air duct. The first and second openings connect the chamber in fluid communication with air which is outside of the cowl. As a result of the structure of the present invention, a stream of air, supported by convection flow of heated air, is directed through the chamber and between the first and second openings. This stream of air flows through the chamber and in thermal communication with the fuel system component to remove heat by convection as cooler air passes over the fuel system component. 
     In a particularly preferred embodiment of the present invention, the air duct is formed to inhibit air flow between the cavity under the cowl and the chamber within the air duct. The first opening is disposed at a lower location than the second opening in order to facilitate the natural conduction flow of heated air through the chamber from the first opening to the second opening. This convection flow does not require operation of the engine and, therefore, provides a cooling flow of air past the fuel system component after the engine is turned off. 
     In one embodiment of the present invention, the first opening is disposed at a front portion of the outboard motor and the second opening is disposed at a back portion of the outboard motor. The fuel system component can be a fuel pump, a fuel conduit, a fuel rail of a fuel injection system, a carburetor of a carbureted system, or a compressor of a fuel injected system. The air duct can be formed to prevent air flow between the cavity and the chamber, but this is not a requirement in all embodiments of the present invention. 
    
    
     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 of the present invention in conjunction with the drawing; in which: 
     FIGS. 1 and 2 show a preferred embodiment of the present invention; 
     FIG. 3 shows an alternative embodiment of the present invention with the first opening extending in a rearward direction; 
     FIG. 4 shows a first opening of the present invention which is reduced in size to limit noise emanating from the outboard motor; 
     FIG. 5 has a first opening directed downward; and 
     FIG. 6 shows the present invention used in conjunction with a fuel injected system. 
    
    
     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 an outboard motor  10  with a cowl  12  disposed over an engine cavity  16  in which an engine  14  is disposed. The engine  14  is located within the cavity  16  defined by the cowl  12 . Fuel system components, such as the carburetor  20  and fuel pump  24 , are connected in fluid communication with the engine  14  in order to supply fuel to one or more combustion chambers of the engine  14 . The fuel system components are external from the engine  14  and disposed under the cowl  12 . An air duct  30  is disposed within the cavity  16  of the cowl  12 . The air duct  30  has a first opening  32  and a second opening  34 . The air duct  30  defines a chamber  38  within its structure with the chamber  38  being disposed in fluid communication between the first and second openings,  32  and  34 . The first and second openings connect the chamber  38  in fluid communication with air which is outside the cowl  12 . 
     The arrows in FIG. 1 illustrate the flow of air within the air duct  30  when the engine  14  is operating. The carburetor  20  or, alternatively, the throttle body of the engine, draws air into the engine for use in the combustion process. This air is provided to the carburetor  20  from two directions. Air can flow to the carburetor  20  from the first opening  32  that is located in a front portion  40  of the cowl  12 . Air also flows into the second opening  34  which is disposed in fluid communication with an air inlet  44  formed in the cowl  12 . The air inlet  44  and its surrounding baffle structure  46  is generally conventional in nature and known to those skilled in the art. Normally, air flowing through the air inlet  44  communicates with air in the cavity  16  of the cowl  12  and is able to flow throughout the space of the engine  14  and the cowl  12 . The air duct  30  of the present invention directs incoming air from the air inlet  44  into the second opening  34  of the air duct  30  of the present invention and then toward the carburetor  20 . 
     In FIG. 1, a fuel line  60  is shown providing fuel from a fuel tank of a marine vessel to the fuel pump  24 . However, it should be understood that the routing of the fuel line  60 , along with the use of a fuel pump  24  with the carburetor  20  and their respective locations, are not limiting to the present invention. 
     FIG. 2 shows the outboard motor  10  with the engine  14  disposed within the cavity  16  defined by the cowl  12 . The illustration in FIG. 2 is intended to show the operation of the present invention during the period of time after the engine  14  is turned off. Since heat is conducted from the heat transmitting portions of the engine  14  to the components of the fuel system, represented by the fuel pump  24  and the carburetor  20  or throttle body, in FIG. 2, the heat from these fuel components will tend to travel upward by convection. Since heat rises, the heat from the fuel components will be conducted from the main chamber  38  of the air duct  30  toward the second opening  34 . From the second opening  34 , the warmed air will pass out of the cowl  12  through the air inlet  44 . Cooler air will therefore be drawn into the first opening  32  from the front portion  40  of the outboard motor  10 . Since the second opening  34  is located at a higher position than the first opening  32 , a natural convection stream of air will be induced through the chamber  38 , removing heat from the fuel system components subsequent to the engine being turned off. As long as the fuel system components, such as the fuel pump  24  and the carburetor  20 , with its intermediate conduit  70 , are receiving heat conducted to them from the engine  14 , the emitted heat will tend to rise within the chamber  38  of the air duct  30  and flow upward toward the second opening  34 . This, in turn, will draw cooler air from the outside of the cowl  12  and through the first opening  32 . 
     In FIGS. 3-6, the engine  14  is not specifically shown under the cowl  12 . However, it should be understood that the fuel system components located within the chamber  38  of the air duct  30  are physically connected in fluid communication with an engine and, after the engine is turned off, receives heat through conduction as a result of their proximity to the engine. The engine  14  is not shown in FIGS. 3-6 for reasons of simplifying those illustrations. 
     The embodiment shown in FIG. 3 is similar to that illustrated in FIG. 2, but with the first opening  32  located at a rear portion  80  of the outboard motor  10 . The operation of the air duct  30  is the same as that described above in conjunction with FIGS. 1 and 2. When the engine is turned off, warm air flows from the fuel system components,  20  and  24 , and from the chamber  38  toward the second opening  34  of the air duct  30 . The warm air then flows out of the air inlet  44  formed in the cowl  12 . This convection flow draws cool air into the first opening  32 . The flow of cool air over the fuel system components removes heat from them and decreases the likelihood that vapor lock will occur. 
     FIG. 4 shows a representation of an outboard motor with the air duct  30  of the present invention located within the cavity  16  defined by the cowl  12 . The fuel system components are simplified and illustrated as a dashed box  80  in FIG.  4 . The difference between the arrangements shown in FIG.  4  and that illustrated in FIG. 2 is that the first opening  32  is significantly smaller in diameter than the version shown in FIG.  2 . This is done in order to attenuate the sound that can be transmitted from the fuel system components, such as a carburetor, in a direction toward the operator of the marine vessel. The reduced size of the first opening  32  attenuates this sound that could otherwise emanate from the carburetor or throttle body through the first opening  32  toward the operator. 
     FIG. 5 is an alternative embodiment of the present invention in which the first opening  32  of the air duct  30  is directed downward and receives air through an opening at the bottom portion of the cowl  12  rather than through the front portion  40 . Other than this downwardly directed first opening  32 , the embodiment of the present invention shown in FIG. 5 operates similarly to that described above in conjunction with FIGS. 1-4 in order to create a convection flow of air from the first opening  32  to the second opening  34  and thereby out of the cowl  12  in order to conduct heat away from the fuel system components  80 . 
     The embodiment of the present invention shown in FIG. 6 is generally similar to that shown in FIG. 2, except that the fuel system components or those that are typically used in a fuel injected engine. For example, FIG. 6 illustrates a fuel rail  90  and an air compressor  92  that are representative of fuel system components associated with a fuel injected engine. These components are disposed within the chamber  38  and receive the benefits of convection cooling from the air that flows into the first opening  32  through the chamber  38 , and out of the second opening  34 . 
     All of the embodiments of the present invention exhibit certain common characteristics. First, they comprise an air duct  30  which has a first opening  32  and a second opening  34  that are arranged relative to each other to encourage the creation of convection currents of air flow that take heat from the fuel system components  80  and remove them from the outboard motor  10 . The second opening  34  is typically arranged above the first opening  32  to encourage the convection flow of air that results from the natural tendency of warm air to rise. This convection flow then draws cooler air from outside of the outboard motor into the first opening  32  to replenish the air within the chamber  38  that is in thermal communication with the components of the fuel system. The first opening  32  need not intersect the front portion  40  of the cowl  12 . Instead, it can intersect the rear portion  80  of the cowl  12 , as shown in FIG. 3, or the bottom portion of the cowl  12  as shown in FIG.  5 . The fuel system components need not be for a carbureted engine. Alternatively, the fuel system components can be used in conjunction with a fuel injected engine. Although the second opening  34  is illustrated as being located at the rearward portion of the outboard motor  10 , it should be understood that this location is not limiting to the present invention. 
     Although the present invention has been described to specifically illustrate several alternative embodiments of the present invention, it should be understood that alternative embodiments are also within its scope.