Abstract:
A system for supplying fuel under pressure to an internal combustion engine, and to control fuel delivery to a fuel injection system in an internal combustion engine having a low pressure pump formed integrally as at least part of a main housing of a vapor separator assembly. The low pressure pump lifts fuel into a cavity of a reservoir, which is drawn from a high pressure pump into the internal combustion engine. Due to the integrated nature of the low pressure pump, leak paths and assembly costs are reduced.

Description:
CLAIM FOR PRIORITY 
       [0001]    This application claims the benefit of priority to U.S. Ser. No. 61/293,363, filed Jan. 8, 2010, the contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The subject invention relates to a system for supplying fuel under pressure to an internal combustion engine, and, more specifically, to controlling fuel delivery to a fuel injection system in an internal combustion engine having a low pressure pump formed integrally as at least part of a main housing of a vapor separator assembly. 
         [0004]    2. Description of the Prior Art 
         [0005]    In fuel supply systems, and in particular for a marine engine having in-board and stern drive type engines, it is often challenging to supply an uninterrupted flow of fuel under all operating conditions. The operating environment is frequently very hot, causing the fuel to vaporize if not carefully controlled. And fuel delivery must be compatible with marine engine run cycles which are characterized by long periods of operation at a steady RPM, punctuated by abrupt instances of rapid acceleration or deceleration. Throughout these cycles and conditions, fuel is expected to be delivered to the engine without interruption. 
         [0006]    Furthermore, marine applications are often subject to harsh vibrations and jarring. The fuel delivery system must be heartily designed and fortified to prevent fuel leakage even under violent operating conditions. Leaked fuel on a marine vessel can, in extreme instances, result in fire which may require immediate human evacuation regardless of the vessel location or weather conditions. 
         [0007]    Thus, meeting the fuel demands of a marine engine under these operating conditions and in consideration of these safety issues can be a challenge. A prior art technique to provide fuel to a marine engine is shown in applicant&#39;s own U.S. Pat. No. 6,257,208, the contents of which are hereby incorporated by reference. According to this technique, a high pressure fuel pump delivers a continual supply of fuel to the engine injector system in sufficient quantities to meet engine demands at so-called ‘full throttle.’ When the engine fuel demands are less than ‘full throttle,’ a return line is employed to return unneeded fuel from the engine injector system to the vapor separator. 
         [0008]    One disadvantage of this technique resides in the requirement to design and fabricate the return line and associated fittings with extremely high quality and durable components to avert the possibility of fuel leakage over the foreseeable service interval of the fuel supply system. This increases both the cost of the fuel supply system and the risk of leakage, particularly where operating conditions are harsh and service intervals extend beyond manufacturer recommendations. 
         [0009]    Another prior art owned by applicant is U.S. Pat. No. 7,168,414, the contents of which are hereby incorporated by reference. The system eliminates the recirculation of unused fuel through the engine injector system, as described above. In turn, this also eliminates the added design and fabrication costs of the return line, and reduces the risk of fuel leakage. As illustrated in  FIG. 1 , the system is characterized by a bypass line  40  which extends between the fuel delivery line  34  and the vapor separator  20  for returning excess fuel to the vapor separator prior to its reaching the engine injector system. In this manner, fuel in excess of the demands of the engine injector system is returned directly to the vapor separator thus eliminating the need to recirculate unneeded fuel through the engine injector system. 
         [0010]    In additional to the disadvantages describe above, this system suffers from having a low pressure lift pump  18  located outside of the vapor separator  40 . This requires additional mounting hardware and fuel hose routings, which increase the costs and leakage points of fuel. 
         [0011]    Another prior art system is U.S. Pat. No. 6,390,871, which discloses a fuel reservoir mounted to a driveshaft housing of an outboard motor. As illustrated in  FIG. 2 , a first fuel pump  20  is a lift pump which draws fuel from a fuel tank and pumps the fuel into the cavity  12  of the reservoir  10 . A second fuel pump  30  is a high pressure pump which draws fuel from the cavity and pumps the fuel at a higher pressure to a fuel rail of an engine. Both the first and second pumps are disposed within a volume of fuel stored in the fuel reservoir. Although providing less leakage points than the aforementioned prior art, this system still suffers from leakage points and costs associated with assembly and mounting. 
       SUMMARY OF THE INVENTION 
       [0012]    The subject invention overcomes the disadvantages of the prior art by eliminating leakage points and increased costs associated with assembly. Rather, a low pressure lift pump, such as a pulse pump, is integrally formed at least in part with the vapor separator. The pump, for example, may be located internally, externally or partly internally and partly externally to the vapor separator. This, in turn, eliminates the added design and fabrication costs of a prior art, and reduces the risk of fuel leakage. 
         [0013]    In one embodiment of the invention, there is a fuel vapor separator, including a housing, a low pressure pump delivering fuel from to the vapor separator and a high pressure pump delivering fuel to an engine, wherein the low pressure pump is formed at least in part as a single piece of material with the housing. In one aspect, the low pressure pump may be internal or external to the housing. A reservoir in the housing has a cavity to contain liquid fuel for use by an engine, wherein the high pressure pump draws fuel from the cavity and pumps fuel to the engine, and the low and high pressure pumps are disposed in thermal communication with the fuel when the fuel is within the cavity. A hollow tube is configured into a coil having a plurality of loops, the coil dimensions to fit within the interior of the housing, the tube having first and second ends extending through the housing for connection to respective coolant supply and discharge members. A decoupled float valve vents vapor from the vapor separator when the fuel in the cavity falls below a predetermined level. A pressure relief valve opens when a predetermined pressure is reached within the cavity to vent fuel vapor from the cavity. 
         [0014]    In another embodiment of the invention, there is a fuel supply system for a marine engine, including a vapor separator receiving liquid fuel from a fuel tank and collecting vapors given off from the fuel, the vapor separator including a housing having an interior and an exterior; a high pressure pump received in a main body of the vapor separator, and having an inlet in communication with a reservoir in the main body and an outlet through which pressurized fuel is delivered to the engine; and a low pressure pump integrally formed as at least part of the vapor separator main body, and delivering fuel to the vapor separator. In one aspect, the low pressure pump may be internal or external to the housing. A reservoir has a cavity to contain liquid fuel for use by an engine, wherein the high pressure pump draws fuel from the cavity and pumps fuel to the engine, and the low and high pressure pumps are disposed in thermal communication with the fuel when the fuel is within the cavity. A hollow tube is configured into a coil having a plurality of loops, the coil dimensions to fit within the interior of the housing, the tube having first and second ends extending through the housing for connection to respective coolant supply and discharge members. A decoupled float valve vents vapor from the vapor separator when the fuel in the cavity falls below a predetermined level. A pressure relief valve opens when a predetermined pressure is reached within the cavity to vent fuel vapor from the cavity. 
         [0015]    In still another embodiment of the invention, there is a vapor separator for a fuel pump assembly of an internal combustion engine, including a reservoir having a cavity for containing fuel for use by the engine; and a low pressure pump providing the fuel to the reservoir, wherein the low pressure pump is integrally formed as at least part of a main body of the vapor separator. In one aspect, a high pressure pump draws the fuel from the cavity and pumping the fuel to the engine, and being disposed within the cavity of the reservoir and in thermal communication with the fuel when the fuel is within the cavity. A hollow tube is configured into a coil having a plurality of loops, the coil dimensions to fit within the interior of the main body, the tube having first and second ends extending through the main body for connection to respective coolant supply and discharge members. The low pressure pump may be disposed in a location external or internal to the reservoir. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
           [0017]      FIG. 1  is a schematic diagram of a marine vapor separator with a bypass line in accordance with the prior art. 
           [0018]      FIG. 2  is a schematic representation of a fuel system for a marine propulsion system in accordance with the prior art. 
           [0019]      FIG. 3  is a schematic diagram according to the invention where the low pressure pump is formed integrally with the vapor separator. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0020]    Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a fuel supply system for a marine internal combustion engine in is illustrated schematically in  FIG. 3 . 
         [0021]      FIG. 3  illustrates a fuel vapor separator  50  having a main body  52  formed of polymeric materials that is adapted to received a supply of liquid fuel and provide a substantially vapor free supply of liquid fuel to fuel pump  54 . The fuel pump  54  is preferably carried by the fuel vapor separator  50  and may be an electric motor driven fuel pump having an inlet in communication with the supply of liquid fuel in the main body  52  and an outlet  56  through which pressurized fuel is discharged for delivery to an engine. Fuel is pumped from a tank using a low pressure lift pump  60  into a reservoir of the vapor separator  50 . The low pressure lift pump  60  is formed integrally with the vapor separator  50 . That is, at least part of the low pressure lift pump is formed from the same material and integral with the vapor separator body  50 . This provides fewer leakage paths and helps to reduce costs associated with assembly. The low pressure pump may reside external to the vapor separator  50 , as illustrated in  FIG. 3 , or it may reside internal to the vapor separator (not illustrated), as well known in the art. For example, the low pressure pump and vapor separator may be formed from the same material to create a single continuous unit. In a preferred embodiment, the low pressure pump  60  is a pulse type pump. A pulse fuel pump typically has four tubes connected to it. One tube connects the fuel tank. Two tubes connect to the crankcase of the engine and one tube connects to the inlet of the fuel vapor separator. When the engine revolves, the tube connecting the engine delivers fuel with a pulse of pressure at each revolution. The diaphragm pulsates with the pressure. At the top of the pump are two chambers, which are separated by a pair of one way valves. These valves ensure that the fuel that passes through does not come back. Fuel flows from one chamber to the other at one pulse and at the next pulse, fuel moves to the engine. 
         [0022]    In more detail, fuel is routed from a tank (not illustrated) via a low-pressure type lift pump  60 , such as a pulse pump, which urges fuel into a vapor separator, generally indicated at  50 . The vapor separator  50  thus receives liquid fuel from a fuel tank through a direct distribution system. The primary purpose of the vapor separator  50  is to collect and discharge vapors given off from the fuel. In this embodiment, the low pressure pump  60  is integrally formed as at least part of the vapor separator  50  and continually adds more liquid fuel to a reservoir of vapor separator  50 . The vapor vent  58  allows vapors to bleed off. The vapor vent  58  is controlled by a float valve, preferably decoupled  64 , which is responsive to the level of liquid fuel in the reservoir of vapor separator  50 . Whenever liquid fuel threatens to escape through the vapor vent  58 , the float valve automatically closes. In all non-threatening conditions, the vapor vent  58  remains open to exhaust fuel vapors. 
         [0023]    The high pressure pump  54  has a fuel inlet for withdrawing liquid fuel from the reservoir region of the vapor separator  50 . The high pressure pump  54  also has a fuel outlet  56  for delivering fuel under pressure to an engine injector system. The engine injector system can be of any type suited to vaporize fuel for a marine engine (not shown). In the typical case, the engine injector system includes a plurality of injectors. 
         [0024]    The high-pressure pump  54  is designed to run continuously whenever the engine is in operation. The pump  54  is also rated to provide maximum fuel delivery and pressure for engine ‘full throttle’ conditions. However, because an engine is not run at full throttle condition at all times, the pump  54  will attempt to deliver more fuel than is needed during other (non ‘full throttle’) conditions. 
         [0025]    To alleviate excess pressure build-up in the fuel delivery line and the associated fittings, as well as in the engine injector system, a bypass or return line may extend between the fuel delivery line and the vapor separator  50  (not shown). The bypass or return line returns excess fuel to the vapor separator  50  prior to the fuel reaching the engine injector system and thereby eliminates the need to recirculate unused fuel through the engine injector system. 
         [0026]    In operation, fuel is supplied to the engine by first moving liquid fuel from a fuel tank (not shown) to the vapor separator  50  by use of the low pressure pump  60 . Water is separated from the fuel prior to reaching the low pressure pump. In the vapor separator  50 , vapors given off from the fuel are collected and vented, or bled, to the atmosphere or other suitable collection system. The float valve automatically interrupts the vapor bleeding in response to the level of liquid fuel in the vapor separator  50  reaching a predetermined height to prevent the escape of liquid fuel through the vapor vent  58 . 
         [0027]    The high pressure pump  54  withdraws liquid fuel from the vapor separator  50  and delivers it under pressure to the engine injector system via a fuel delivery line (fuel out  56 ). However, the fuel pressure between the high pressure pump  54  and the engine injector system is monitored to determine whether the engine injector system is being presented with more fuel than is required for efficient engine operation. If more fuel than needed is being supplied by the high pressure pump  54 , the extra, unneeded fuel may be automatically returned to the vapor separator  50  through a bypass or return line. Thus, fuel in excess of engine demand is returned to the vapor separator  50  prior to its reaching the engine injector system. 
         [0028]    In addition, positioned internally within main body  52  of vapor separator assembly  50  is a hollow cylindrical tube  62  which is bent and configured into a coil having multiple circular loops. An intake end is connected to a source of liquid coolant (not shown) which in the case of a Marine engine is typically a pump that pumps water from the lake or ocean water environment in which the engine is operating into the engine for cooling purposes. The coolant water typically is used to cool the combustion chambers of the engine as well as the vapor separator assembly  50 . The lake or ocean water or other liquid coolant is pumped through tube coil  62  from the first end to a second outlet end thereby removing heat from the interior of main body  52  of vapor separator assembly  20 . 
         [0029]    The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. 
         [0030]    Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, wherein that which is prior art is antecedent to the characterized novelty and reference numerals are merely for convenience and are not to be in any way limiting, the invention may be practiced otherwise than as specifically described.