Abstract:
A fuel supply system for use with an engine having four vertically-arranged cylinders and multiple charge formers prevents air or vapor pockets from accumulating within the fuel pump or fuel lines. A pair of fuel pumps are mounted vertically one above the other. A fuel inlet port of each pump is formed at the lower-most portion of the pump. A fuel discharge port is formed at the upper-most portion of each port. A conduit attached to the top fuel pump&#39;s discharge port supplies fuel to an uppermost and lowermost carburetor. A conduit from the lowermost fuel pump supplies fuel to the middle two carburetors. The uppermost carburetor&#39;s fuel inlet port is positioned vertically higher than the top fuel pump&#39;s discharge port. The second carburetor&#39;s fuel inlet port is positioned vertically higher than the second fuel pump&#39;s discharge port. Air or vapor pockets within the fuel lines naturally migrates through the fuel pump and through the fuel conduits into the carburetors without becoming trapped in the fuel supply system.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a fuel supply system for an engine, and more particularly to an improved fuel supply system for an engine having multiple charge formers. 
     2. Description of the Related Art 
     Many internal combustion engines are provided with a plurality of charge formers. With such an arrangement, it is desirable to ensure that the fuel supply system delivers fuel uniformly and equally to all of the charge formers. Although this is generally not a problem, with certain types of applications for internal combustion engines, it can become a problem. 
     For example, with some applications for internal combustion engines, the charge formers are disposed so that they are positioned vertically above each other. This is typical, for example, in outboard motor practice. In outboard motors, the engine is disposed so that its output shaft rotates about a vertically extending axis. As a result, the individual cylinders extend generally horizontally and are arranged in a vertically spaced relationship. The charge formers, therefore, adopt a similar attitude and disposition. 
     Fuel supply systems for engines with vertically-arranged charge formers frequently include a single conduit or manifold that extends from the fuel pump to all charge formers. The conduit may be configured in such a way that it forms areas where fuel or vapor can become trapped. Additionally, the fuel pump itself may be configured in such a way that it forms areas where fuel vapor can be trapped. If a fuel vapor pocket forms, then the charge formers downstream of the vapor pocket will not receive fuel, or at least not receive a desired amount of fuel, thereby affecting proper engine operation. 
     In an attempt to alleviate these problems, it has been proposed to provide the fuel pump at a lower location than the charge formers. Also, the fuel pump may be provided with a plurality of fuel outlets and conduits that feed respective carburetors of the system. With this type of arrangement, however, the fuel pump is normally positioned below the lowest carburetor. In this position, the relatively high head between the fuel pump and the highest carburetor restricts the fuel pump&#39;s ability to deliver fuel. Also, vapor venting is not assured. Furthermore, a fuel pump mounted below the lowest carburetor may not be capable of being powered by an engine camshaft. 
     Accordingly, a need exists for a fuel supply system for an engine having multiple charge formers, wherein the system ensures against vapor blockage in fuel supply lines. There is a further need for a fuel system having a fuel pump which is powered by a camshaft, the fuel pump being arranged to prevent vapor interference with fuel flow. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention involves an internal combustion engine having at least one variable volume combustion chamber. The combustion chamber is defined by at least a pair of components that move relative to each other. A charge former supplies a fuel/air charge to the combustion chamber, and a fuel supply system provides fuel to the charge former. The fuel supply system includes a fuel pump having a discharge port communicating through a conduit with the charge former. The discharge port is positioned at an uppermost portion of the fuel pump, and a discharge check valve is positioned adjacent the discharge port. This orientation of the fuel pump inhibits vapor from becoming trapped within the fuel pump. 
     Further aspects, features and advantages of the present invention will become apparent from the detailed description of the preferred embodiment which follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features of the invention will now be described with reference to the drawings of a preferred embodiment of the present engine and fuel supply system. The illustrated embodiment is intended to illustrate but not limit the invention. The drawings contain the following figures: 
     FIG. 1 is a side elevational view of an outboard motor in which the present fuel supply system can be employed. 
     FIG. 2 is a top view of the outboard motor of FIG. 1, illustrating the engine and the fuel supply system, which is configured in accordance with a preferred embodiment of the present invention, with the cowling and selected components of the engine shown in phantom. 
     FIG. 3 is a side view of the outboard motor of FIG. 1 with the cowling shown in section. 
     FIG. 4A is a rear end view of the power head of the outboard motor of FIG. 1 with the cowling shown in section. 
     FIG. 4B is an enlarged, sectional view of a fuel pump of the fuel supply system shown in FIGS. 2 and 4A. 
     FIG. 5 is a view of a bank of carburetors and a portion of the fuel supply system of FIG. 2 as viewed in the direction of line  5 — 5  of FIG. 2, with the fuel delivery lines unattached to the engine. 
     FIG. 6A is a side cross-sectional view of one of the carburetors of the engine taken along lines  6 A— 6 A of FIG.  2 . 
     FIG. 6B is a cross-sectional view of one of the carburetors taken along lines  6 B— 6 B of FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates an outboard drive  10  which incorporates a fuel supply system configured in accordance with the preferred embodiment of the present invention. Because the present fuel supply system has particular utility with an outboard motor, the fuel supply system is described below in connection with the outboard motor. However, the description of the invention in conjunction with the illustrated outboard motor is merely exemplary. 
     The outboard motor  10  has a power head  12  which includes an internal combustion engine  14 . A protective cowling assembly  16  surrounds the engine  14 . The cowling assembly  16  includes a lower tray  16   a  and a main cowling member  16   b.    
     As is typical with outboard motor practice, the engine  14  is supported within the power head  12  so that its output shaft  17  (i.e., a crankshaft as illustrated in FIG. 2) rotates about a vertical axis. The crankshaft  17  is coupled to a drive shaft  19  that depends through and is journalled within a drive shaft housing  18 . 
     The drive shaft housing  18  extends downward from the cowling  16  and terminates in a lower unit  20 . The drive shaft  19  extends into the lower unit  20  to drive a transmission housed within the lower unit  20 . The transmission selectively establishes a driving condition of a propulsion device  22 . In the illustrated embodiment, the propulsion device  22  is a propeller. The transmission desirably is a forward/neutral/reverse-type transmission so as to drive the watercraft in any of these operational states. 
     A steering shaft extends through a steering bracket  24  and rotates about a vertically extending axis. The steering bracket  24  is affixed to the drive shaft housing  18  by upper and lower brackets  26 ,  28 . Steering movement occurs about a generally vertical steering axis which extends through the steering shaft. A steering arm  30  is connected to an upper end of the steering shaft  26  and extends in a forward direction for manual steering of the outboard motor  10 , as known in the art. 
     The swivel bracket  26  also is pivotally connected to a clamping bracket  32  by a pin  34 . The clamping bracket  32 , in turn, includes a transmission adapted to attach to a transom  36  of an associated watercraft  37 . The clamping bracket  32  is arranged on the transom  36  at a location which supports the outboard motor  10  in a generally upright position and at a location where the blades of the propeller  22  lie at least partially beneath the surface level S of the body of water in which the watercraft  37  is operated. 
     The conventional coupling between the swivel bracket  26  and the clamping bracket  32  permits adjustment of the trim position of the outboard motor  10 , as well as allows the outboard motor  10  to be tilted up for transportation or storage. For this purpose, a conventional tilt and trim cylinder assembly desirably operates between the clamping bracket  32  and the swivel bracket  26 . This conventional mounting thus permits the outboard motor  10  to move within a normal or designed range of positions relative to the transom between a generally upright position (or slightly tilted away from the transom) to a full tilt-up position. This results in about an 80 degree range of movement when installed on the transom (i.e., between normal operating positions). 
     The drive shaft  19  drives a water pump which preferably is disposed at the lower end of the drive shaft housing  18 . The pump draws water through an inlet port  35  and delivers the water to the engine  14 . At least a portion of the cooling water is discharged from the outboard motor  10  through an exhaust system (described later) with the exhaust gasses from the engine in order to cool and silence the exhaust gasses, as known in the art. 
     The construction of the outboard motor  10  as thus far described is considered to be conventional, and for that reason further details of the construction are not believed necessary to permit those skilled in the art to understand and practice the invention. 
     In order to facilitate the description of the present invention, the terms “front” and “rear” or “aft” are used to indicate the relative sides of the components of the engine and the fuel supply system. As used herein, “front” refers to the side closest to the transom  36 , while “rear” or “aft” refer to the side farthest from the transom  36 . 
     With reference to FIGS. 2 and 3, the engine  14  preferably operates on a four-cycle combustion principle and includes a cylinder block  38  having four cylinders  40  formed therein in a vertically spaced arrangement. FIG. 2 illustrates a top cylinder  40  in phantom lines. A piston  42  is positioned within the cylinder  40  and is adapted for reciprocating movement therein. The piston  42  is connected to a first end of a connecting rod  44 . A second end of the rod  44  is rotatably connected to a throw of the crankshaft  17 . The crankshaft  17  rotates about a substantially vertical axis and is enclosed within a crankcase  46 , which in the illustrated embodiment is formed between an aft end of the cylinder block  38  and a crankcase member  48 . 
     A cylinder head  50  is attached to the cylinder block  38 . A combustion chamber is formed by the cylinder head  50 , and corresponding cylinder  40  and piston  42 . An intake port  52  is formed through the cylinder head  50 , providing a passageway for an air/fuel charge to enter the combustion chamber. An intake valve  54  is supported by the cylinder head  50  and is adapted to regulate flow through the intake port  52  into the combustion chamber. An intake valve camshaft  56  is journalled within the cylinder head  50 . The intake valve camshaft  56  actuates the intake valve  54  in a reciprocating manner as known in the art. Each cylinder of the engine has associated with it an intake port and intake valve which is actuated by the camshaft. 
     An exhaust port  58  is also formed in the cylinder head  50 . The exhaust port  58  provides a passage for exhausts product to exit the combustion chamber. An exhaust valve  60  is supported by the cylinder head  50  and regulates flow through the exhaust port  58 . An exhaust valve camshaft  62  is journalled within the cylinder head  50  and is adapted to actuate the exhaust valve  60  in a reciprocating manner similar to that of the intake valve and intake valve camshaft. Again, each cylinder of the engine has associated with it an exhaust port and an exhaust valve which is actuated by the corresponding camshaft. While the illustrated embodiment employs one intake valve and one exhaust valve per cylinder, other numbers of exhaust and intake valves can also be used. 
     A cylinder cover  64  is fit over the cylinder head  50  and encloses a camshaft chamber  66  therein. The camshafts  56 ,  62  and valves  54 ,  60  are enclosed within the camshaft chamber  66 . 
     A drive pulley  68  is connected to the crankshaft  17 . A pair of camshaft driven pulleys  70  are also provided and are connected to respective camshafts  56 ,  62 . A belt  72  extends around the pulleys  68 ,  70 . In this manner, the drive pulley  68  drives the camshaft pulleys  70 . To ensure proper valve timing, the camshaft drive pulleys are preferably twice the diameter of the crankshaft drive pulley. 
     As best shown in FIG. 3, a flywheel  74  is positioned above the crankshaft drive pulley  68  and is adapted to rotate with the crankshaft  17 . It is to be understood that although the flywheel  74  and the pulleys  68 ,  70  are illustrated as disposed at the top of the engine, these components can be appropriately rearranged. For example, the drive shaft and flywheel may be positioned at the bottom of the engine. 
     An air inlet device  76  is positioned near the front of the engine  14  and is adapted to intake air from within the cowling  16 . As best shown in FIG. 3, the air inlet device  76  splits into four intake pipes  78 , each intake pipe  78  being adapted to deliver an air charge to a corresponding combustion chamber. A carburetor  80  communicates with an each intake pipe opposite of the intake device  76  and is adapted to introduce a fuel charge into the air charge. Each of the carburetors  80  are connected to an intake manifold  82 . The intake manifold  82  includes a plurality of passages  84 . The manifold passages  84  communicate with the intake ports  52  formed in the cylinder head  50 . For each cylinder, the air/fuel charge is delivered from the corresponding intake passage  84  to the intake port  52 , as regulated by the intake valve  54 , to the corresponding combustion chamber. After combustion, the exhaust products flow through the exhaust valve  60 , out of the exhaust port  58 , and to an exhaust manifold  86 . 
     With reference also to FIG. 4A, an oil fill port  88  is located on the cylinder head cover  64 . The fill port  88  extends through the cylinder head cover  64 , allowing addition of lubricant into the camshaft chamber  66 . Oil galleries are formed in the cylinder block  38  and are adapted to communicate lubricant from the camshaft chamber  66  to various engine components, such as the pistons  42 , crankshaft  17  and connecting rods  44 . An oil pan (not shown) desirably collects oil that has circulated through the galleries and the crankcase  66 . In one mode, the oil pan can be mounted to an underside of an exhaust guide  90  (which is shown in FIG.  3 ). 
     As seen in FIG. 2, an oil pump  90  is provided for transferring oil from the oil pan to the camshaft chamber  66  and for recirculation through the engine. An oil conduit  92  communicates lubricant from the oil pump  90  to the camshaft chamber  66 . 
     A blow-by gas vapor separator  94  is mounted on the cylinder head cover  64  and communicates with the camshaft chamber  66 . A return pipe  96  extends from the vapor separator  94  to the air inlet device  76 . Blow-by gasses separated from oil within the vapor separator  94  are delivered through the return pipe to the air inlet device  76  for eventual delivery to one of the combustion chambers for burning. 
     A pair of fuel pumps  98  are mounted on the cylinder head cover  64 , one above the other. A fuel supply conduit  100  extends from a source of fuel, such as a fuel tank, through a fuel filter  99  (FIG.  2 ), to a T-fitting  101  (FIG.  4 ). Upper and lower supply conduits extend from the T-fitting  101  to inlet ports  102  of the respective upper and lower fuel pumps  98 . The T-fitting  101  is preferably positioned vertically lower than the inlet port  102  of the lower fuel pump  98 . Thus, the fuel supply conduits preferably follow a generally upwardly-directed path to the fuel pumps  98 . 
     As shown in FIG. 4B, each fuel pump  98  comprises a housing  104  enclosing a pump chamber  106 . The inlet port  102  is provided at a lower portion of the housing  104 . The inlet port  102  is preferably oriented to extend at least partially downward. A discharge port  108  is provided at an upper portion of each fuel pump  98 . The discharge port  108  is preferably oriented to extend at least partially upward. 
     An inlet valve  110  is positioned adjacent the inlet port  102 . The valve  110  includes a valve seat  112  that is positioned at least partially to the side of the inlet port  102 . A valve element  114  cooperates with the valve seat  112  and is biased to a closed position. The valve element  114  is also arranged to provide one-way flow through the valve  110  in a direction into, but not out of, the pump chamber  106 . 
     A discharge valve  116  valve is positioned adjacent the discharge port  108  in an upper portion of the fuel pump  98 . The discharge valve  116  includes a valve seat  118  that is positioned immediately adjacent to, but at least partially to the side of, the discharge port  108 . The discharge valve  116  is preferably a one-way valve adapted to allow flow out of, but not into, the pump chamber  106 . A valve element  120  cooperates with the valve seat  118  and is arranged to permit the valve to function in this manner. The valve element  120  desirably is biased toward a closed position. 
     A diaphragm (not shown) encloses the pump chamber  106 . The diaphragm preferably is actuated by with the intake valve camshaft  56  to alternatively pressurize and depressurize the pump chamber  106  in order to effect flow therethrough. Although the illustrated fuel pumps  98  are powered by rotation of the intake valve camshaft  56 , it is to be understood that fuel pumps  98  having various operating principles may appropriately be used in accordance with the present invention. 
     A conduit  122  is attached to the top fuel pump discharge port  108  and extends around the side of the engine to a T-fitting  124 , as illustrated in FIG.  5 . The T-fitting  124  is positioned vertically higher than the discharge port  108 . From the T-fitting  124 , a first delivery conduit  126  extends to an uppermost carburetor fuel inlet  128 . The uppermost carburetor fuel inlet  128  is preferably positioned vertically higher than the T-fitting  124 . A second delivery conduit  130  extends from the T-fitting  124  to a lowermost carburetor fuel inlet port  132 . The conduits  122 ,  126  from the discharge port  108  to the uppermost carburetor fuel inlet port  128  follow a generally upwardly-directed path. Although portions of the path may extend substantially horizontally, there are preferably no downwardly-extending sections within these lines. 
     The discharge port  108  of the lower fuel pump  98  also communicates with a conduit  134  which extends around the engine to a T-fitting  136 . A third delivery conduit  138  extends from the T-fitting  136  to a second carburetor fuel inlet  140 . The second carburetor  80  is preferably positioned immediately below the uppermost carburetor  80 . The second carburetor fuel inlet  140  is preferably positioned vertically above the T-fitting  136 , which is positioned vertically above the second fuel pump discharge port  108 . As above, the conduits  134 ,  138  follow a generally upwardly-directed path from the lower pump discharge port  108  to the second carburetor fuel inlet  140 . A fourth delivery conduit  142  extends from the T-fitting  136  to a third carburetor fuel inlet port  144 . The third carburetor  80  is preferably positioned below the second carburetor  80  and above the lowermost carburetor  80 . 
     As best seen in FIG. 4A, a bracket  146  secures each T-fitting  124 ,  136  onto the cylinder head  50 . Each bracket  146  desirably is attached to a lower branch of the respective T-fitting  124 ,  136  and supports a portion of corresponding delivery conduit  130 ,  142  attached to the lower branch of the fitting. 
     The above-described arrangement of fuel pumps  98  and conduits provides advantages in fuel delivery. When air or fuel vapor becomes present in the fuel supply system, the vapor will naturally tend to migrate upwardly with the conduit paths. Vapor that flows into the fuel pumps  98  will naturally move to the top of the fuel pumps  98 . Because the discharge port  108  is oriented towards the top of the fuel pump  98  and because of the orientation of the discharge pump port  108 , the vapor will not accumulate to form a vapor pocket, but will instead naturally migrate out of the pump  98 . Thus, operation of the pump  98  will not be significantly interrupted by the presence of a vapor pocket within the pump  98 . 
     After the vapor has passed through the pump into the delivery conduits, the vapor will continue to naturally migrate to the uppermost portion of the conduits. In the case of the upper fuel pump  98 , the first conduit  126  proceeds generally upwardly to the uppermost carburetor fuel inlet port  128 . Accordingly, vapor will naturally migrate to the carburetor inlet port  128 , enter the carburetor&#39;s fuel bowl, and be vented in a known manner. In the case of the lower fuel pump  98 , an air pocket within the associated fuel delivery conduits will naturally migrate through the third conduit  138  to the second carburetor fuel inlet port  140 , where it enters the carburetor fuel bowl and is vented. In this manner, air or vapor that may be found within the fuel supply system will not create blockages within the system and will not significantly interrupt the fuel supply to the carburetors  80 . 
     With reference to FIGS. 6A and 6B, a cross-sectional view of one of the carburetors  80  is shown. A fuel bowl  147  defines a chamber  148  within the carburetor  80  in which fuel is stored. A wall  150  separates the fuel bowl chamber  148  from a throttle passage  152 . The throttle passage  152  is formed within a throttle body  154 . Air flowing through the intake passage  152  is regulated by a throttle valve  156 . A venturi  158  is formed downstream of the throttle valve  156  to lower the air pressure within the intake passage  152 . A suction port  160  extends into the venturi section  158  and provides a passageway between the intake pipe and the fuel bowl  148 . As air flows through the venturi  158 , fuel from the fuel bowl  148  is drawn through the suction port  160  and into the intake passage  160 , as known in the art. 
     A float  162  within the fuel bowl  148  actuates a nee valve  164  when the fuel level drops below a predetermined level. Actuation of the needle valve  164  enables fuel from the carburetor fuel inlet port to flow into the fuel bowl  148 , filling the fuel bowl to the predetermined level. 
     The carburetor preferably includes a pressure relief valve (not shown). Air or vapor that flows into the carburetor from the fuel supply system accumulates within the carburetor. When pressure within the carburetor exceeds a defined limit, the vapor is vented from the carburetor into the intake pipe through the pressure relief valve. 
     A fuel increasing mechanism is also employed with the carburetors  80  of the engine  14 , as best appreciated from FIGS. 3 and 5. In the illustrated embodiment, the fuel increasing mechanism includes a first dash-pot  166  linked to a throttle linkage  168 . The throttle linkage  168  actuates the throttle valves  156  of the carburetors  80  so as to move the valves  156  generally in unison. The linkage  168  also actuates the dash-pot  166 , as described below. 
     The dash pot  166  includes an air chamber that communicates with each of the fuel bowl chambers  148  through a plurality of air lines. In the illustrated embodiment, as best seen in FIG. 5, a first delivery line  170  extends from the dash pot  166  to a T-fitting  172  located on the opposite side of the carburetor bank. One branch of the T-fitting  172  communicates with an air line manifold  174 . The manifold  174  is formed by a plurality of fittings and conduits. Some of the conduits extend between the fittings, and other conduits connect the fittings to air ports  176  on the carburetor bodies  154  that communicate with the corresponding fuel bowl chambers  148 . 
     The other side of the T-fitting  172  is connected to a second dash pot  178 . The second dash pot  178  is also linked to the throttle valves  156  and is actuated by movement of the throttle valves  156  (i.e., by the corresponding linkage, levers or shafts). 
     Upon rapid acceleration or deceleration, the throttle valves  156  are opened or closed rapidly. The dash pot produces an air pulse with such quick movement. In the illustrated embodiment, the first dash pot  166  produces such a pulse upon rapid opening of the throttle valves  156 , while the second dash pot  168  produces such a pulse upon rapid closing of the throttle valves  156 . These pulses are delivered to the fuel bowl chambers  148  of the carburetors  80  through the air line manifold  174 . The pulses of air increase the pressure within the fuel bowl chamber  148  and cause an increased amount of fuel to squirt through the suction port  160 . In this manner, an enriched air/fuel charge is delivered to the combustion chambers during periods of rapid acceleration and deceleration in order to improve engine performance and operation. 
     Although this invention has been described in terms of a certain preferred embodiment, other embodiments apparent to those of ordinary skill in the art are also within the scope of this invention. Accordingly, the scope of the invention is intended to be defined only by the claims that follow.