Priming fuel system method and apparatus for marine engines

This application claims the benefit of U.S. Provisional Patent Application Serial No. 60/215,603, filed Jun. 30, 2000.

The present invention relates generally to fuel systems, and, more particularly, to an apparatus and method for priming fuel systems of marine engines.

Many fuel systems, such as those found on electronically fuel-injected motors for use with marine vehicles, include a low-pressure fuel circuit and a high-pressure fuel circuit. The low-pressure fuel circuit typically includes an engine driven suction or lift pump that pulls fuel through a low-pressure fuel line connecting the vehicle fuel tank to an engine-mounted vapor separator. The vapor separator includes a float-activated needle and seat to control fuel depth within the vapor separator, and an electric fuel pump to increase the fuel pressure to the operating pressure of the high-pressure system, i.e., the electronic fuel injection system.

One of the purposes of such a dual-pressure system is to minimize the amount or length of on-board fuel line containing fuel at high pressure. A leak in the low-pressure line pulls air into the fuel line. In contrast, a leak in the high-pressure fuel line forces or leaks fuel out of the fuel line. Thus, by limiting the amount or length of high-pressure fuel line, the potential for undesirable accumulation of leaked fuel is reduced. Therefore, attempts are made to limit the length and position of the high-pressure fuel line. On outboard engines, the high-pressure fuel lines are typically restricted to the engine itself. Thus, any leaks from the high-pressure fuel line are likely to be contained under the cover or cowl of the engine. The leaked fuel will eventually drain into the body of water, a condition that, although perhaps undesirable, is far less dangerous than the leaked fuel accumulating in the marine vehicle itself. Similarly, on marine vehicles with inboard engines the use of high-pressure fuel lines is restricted to the engine compartment thereby limiting the accumulation of leaked fuel to the engine compartment.

A drawback to such dual-pressure systems is that heat rejection from the high-pressure fuel pump and the engine itself can cause the boiling and/or vaporization of the liquid fuel in the vapor separator, low-pressure lift pump and low-pressure fuel lines. This impedes fuel delivery to the high-pressure fuel pump, and can thereby cause rough engine operation and/or stalling. Therefore, dual-pressure systems generally require an additional cooling system that cools the vapor separator and/or high-pressure return fuel line, typically with cooling water drawn from the body of water.

The additional cooling system must draw power from either the engine or battery in order to operate, and is thus typically operated only during engine operation. Such a cooling system does not prevent the fuel from vaporizing during a hot soak condition, i.e., the time following engine shut-off and before the engine and high-pressure fuel pump have cooled down. During a hot soak, at least some of the heat dissipating from the engine and high-pressure fuel pump is absorbed by the low-pressure fuel remaining in the vapor separator, low-pressure lift pump and low-pressure fuel lines. This absorbed heat can cause vaporization of the low-pressure fuel. The vaporized fuel, in turn, pushes any liquid fuel remaining in the vapor separator and low-pressure fuel lines back into the fuel tank.

Restarting the engine from a hot soak condition, i.e., a hot restart, can result in stalling or rough engine operation if the liquid fuel remaining in the high-pressure fuel line is consumed before the low-pressure lift pump is able to refill the low-pressure fuel line and the vapor separator with liquid fuel. Some fuel systems incorporate a check valve between the lift pump and the fuel tank to reduce the amount of fuel that is pushed back to the fuel tank. However, vaporization of the fuel remaining in the low-pressure fuel line may still occur, and fuel between the check valve and fuel tank may run back to the fuel tank. In order to avoid stalling and/or rough engine operation upon hot restart, the lift pump must replace the volume lost due to the hot soak condition before the liquid fuel remaining in the high-pressure fuel line and vapor separator is consumed.

Therefore, what is needed in the art is an apparatus that reduces the need for a cooling system for the vapor separator and/or high-pressure return fuel line.

Furthermore, what is needed in the art is an apparatus that reduces stalling and/or rough engine operation on hot restart.

The present invention provides a fuel system for fluidly connecting a fuel tank with an engine.

The invention comprises, in one form thereof, a low-pressure fuel circuit fluidly connected to the fuel tank. A high-pressure fuel circuit is supplied with fuel by the low-pressure fuel circuit, and is fluidly connected to the engine. A priming fuel circuit includes a priming fuel conduit and a priming valve. The priming fuel conduit has a first segment and a second segment. The priming valve has an inlet and an outlet. The first segment of the priming fuel circuit fluidly interconnects the low-pressure fuel circuit and the outlet of the priming valve. The second segment of the priming fuel circuit fluidly interconnects the high-pressure fuel circuit and the inlet of the priming valve. The priming valve is operable to control a flow of fluid through the priming fuel conduit to thereby selectively fluidly connect and disconnect the high-pressure fuel circuit and the low-pressure fuel circuit.

An advantage of the present invention is that the cooling system for the vapor separator and/or high-pressure return fuel line can be of a reduced capacity or be completely eliminated.

Another advantage of the present invention is that stalling and/or rough engine operation during hot restart is reduced.

The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become apparent and be better understood by reference to the following description of one embodiment of the invention in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic diagram of one embodiment of a priming fuel system of the present invention;

FIG. 2 is a flow chart of the method of the present invention; and

FIG. 3 is a schematic diagram of a second embodiment of a priming fuel system of the present invention incorporating a flow control device and accumulating device.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.

Referring now to the drawings, and particularly to FIG. 1, there is shown one embodiment of a priming fuel system of the present invention. Fuel system 10 is for use in a dual-pressure fuel system, such as, for example, those typically used in conjunction with marine engines. Fuel system 10 includes fuel tank 12 , low-pressure fuel circuit 14 , high-pressure fuel circuit 16 , priming fuel circuit 18 , and vapor separator 20 .

Low-pressure fuel circuit 14 includes low-pressure fuel line 22 , check valve 24 and lift pump 26 . Low-pressure fuel circuit 14 fluidly connects fuel tank 12 to vapor separator 20 . More particularly, first segment 22 a of low-pressure fuel line 22 fluidly connects fuel tank 12 to check valve 24 , second segment 22 b of low-pressure fuel line 22 fluidly connects check valve 24 to lift pump 26 , and third segment 22 c of low-pressure fuel line 22 fluidly connects lift pump 26 to vapor separator 20 . Check valve 24 , such as, for example, a conventional check valve preferably having a low flow restriction, is disposed intermediate fuel tank 12 and lift pump 26 , and is operable to control the flow of fuel through low-pressure fuel line 22 .

High-pressure fuel circuit 16 includes high-pressure fuel pump 30 , high-pressure fuel line 32 , pressure regulator 34 , fuel filter 36 and fuel rail 38 . High-pressure fuel circuit 16 fluidly interconnects vapor separator 20 with fuel rail 38 , which, in turn, is fluidly connected with and supplies fuel to one or more fuel injectors (not shown) of engine 40 , such as, for example, a marine inboard or outboard motor. Pressure regulator 34 controls the flow of fluid from high-pressure fuel pump 30 to high-pressure fuel line 32 dependent at least in part upon the fuel pressure within high-pressure fuel line 32 . Pressure regulator 34 is, for example, a conventional bypass regulator that diverts fuel in excess of the mass required to maintain fuel pressure back into vapor separator 20 . A first segment 32 a of high-pressure fuel line 32 fluidly connects pressure regulator 34 with fuel filter 36 , and a second segment 32 b fluidly connects fuel filter 36 with fuel rail 38 .

Priming fuel circuit 18 includes priming fuel conduit 52 and priming valve 54 . Priming valve 54 is, for example, a conventional electronically/solenoid controlled check valve, and includes first/outlet side 54 a , second/inlet side 54 b and input 54 c . As will be more particularly described hereinafter, priming valve 54 selectively controls the flow of fluid through priming fuel circuit 18 from high-pressure fuel circuit 16 into low-pressure fuel circuit 14 . A first segment 52 a of priming fuel conduit 52 fluidly connects low-pressure fuel circuit 14 with first/outlet side 54 a of priming valve 54 . Second segment 52 b of priming fuel conduit 52 fluidly connects a second/inlet side 54 b of priming valve 54 with high-pressure fuel circuit 16 . More particularly, first segment 52 a of priming fuel conduit 52 is fluidly connected to second segment 22 b of low-pressure fuel line 22 , i.e., between check valve 24 and lift pump 26 . Second segment 52 b of priming fuel conduit 52 is fluidly connected to first segment 32 a of high-pressure fuel conduit 32 , i.e., between pressure regulator 34 and fuel filter 36 . As will be described more particularly hereinafter, priming valve 54 is operable to selectively control the flow of fluid from inlet 54 b to outlet 54 a thereof, and, thus, controls the flow of fluid through priming fuel circuit 18 from high-pressure circuit 16 to low-pressure fuel circuit 14 .

Vapor separator 20 is a conventional vapor separator that includes a float-activated needle and seat (not shown) that control the liquid level of the fuel contained therein. An inlet (not referenced) of vapor separator 20 is fluidly connected to third segment 22 c of low-pressure fuel line 22 , and an outlet (not referenced) of vapor separator 20 is fluidly connected to first segment 32 a of high-pressure fuel line 32 . In the embodiment shown, pressure regulator 34 and high-pressure pump 30 are integral with and/or contained within vapor separator 20 . Thus, the outlet of vapor separator 20 is functionally equivalent to the outlet of high-pressure fuel pump 30 and/or pressure regulator 34 .

When a hot restart is attempted in a conventional dual-pressure fuel system without the benefit of sufficient cool down time, the engine may be difficult to start, may stall and/or operate roughly. This is due to heat dissipating from the engine and being absorbed into the low-pressure liquid fuel remaining within the low-pressure fuel circuit. The heat may cause vaporization of the liquid fuel within the low-pressure fuel circuit. The fuel vapor displaces any liquid fuel remaining in the low-pressure fuel circuit back into the fuel tank. Upon restart, the low-pressure lift fuel pump must refill the low-pressure fuel circuit with liquid fuel. The low-pressure fuel circuit, however, remains hot. Thus fuel being drawn into the low-pressure fuel circuit can flash from liquid fuel to fuel vapor, expand in volume, and may push the liquid fuel entering the low-pressure fuel circuit back toward the fuel tank. The conversion of the liquid fuel entering the low-pressure fuel circuit into vapor removes some of the heat. This vaporization-heat removal process continues until the low-pressure fuel circuit and the fuel contained therein are sufficiently cooled to stop the vapor generation, or until the fuel within the vapor separator is consumed by the engine. If the engine consumes the fuel within the vapor separator before the low-pressure circuit is sufficiently cooled, rough engine operation, stalling and/or difficulty in starting the engine may result.

In use, and as more particularly described hereinafter, fuel system 10 compares certain parameters of engine 40 against predetermined thresholds and determines whether priming of low-pressure fuel circuit 14 is necessary at start-up of engine 40 . If priming is necessary, priming valve 54 is activated to fluidly connect high-pressure fuel circuit 16 via priming circuit 18 to low-pressure circuit 14 at a point between check valve 24 and lift pump 26 . Liquid fuel is pumped from high-pressure fuel circuit 16 through priming fuel circuit 18 and delivered to the inlet side of lift pump 26 of low-pressure fuel circuit 14 , i.e., second segment 22 b of low-pressure fuel line 22 . As a result, lift pump 26 pumps more efficiently, i.e., pumps a higher mass of fuel with each stroke. Further, the additional mass of liquid fuel increases the heat capacity of low-pressure circuit 14 , which is therefore able to absorb heat at a faster rate. Even further, the additional mass of liquid fuel increases the fuel pressure thereby suppressing vapor within low-pressure circuit 14 . Moreover, the fuel that remains in vapor separator 20 weathers during the hot soak, and therefore has a higher boiling point than the fuel in fuel tank 12 and, thus, vaporizes less readily.

The priming of low-pressure fuel circuit 14 is controlled by priming valve 54 , which, in turn, is controlled by Engine Control Unit (ECU) 60 . ECU 60 is a conventional engine control unit that includes, for example, a 32-bit microprocessor, random access memory, read only memory, and input/output interface circuitry. ECU 60 includes priming valve control output 60 a , coolant temperature input 60 b and manifold air temperature input 60 c . Priming valve control output 60 a is electrically connected with priming valve 54 . Priming valve control output 60 a controls priming valve 54 , i.e., opens and closes priming valve 54 , to connect and disconnect low-pressure fuel circuit 14 and high-pressure fuel circuit 16 , respectively. Coolant temperature input 60 b is electrically connected to coolant temperature sensor 62 , which is in fluid communication with the coolant of engine 50 and which senses the temperature of the coolant of engine 50 . Manifold air temperature input 60 c is electrically connected to manifold air temperature sensor 64 , which senses the manifold air temperature. Each of coolant temperature sensor 62 and manifold air temperature sensor 64 is, for example, a conventional electronic or electro-mechanical sensor that issues an electrical signal indicative of coolant temperature (T c ) and manifold air temperature (T l ), respectively.

Referring now to FIG. 2, ECU 60 is programmed to execute priming method 100 . Priming method 100 executes initialization step 102 at engine key-up or start-up. ECU 60 initializes itself and various systems of engine 50 , such as, for example, fuel system 10 , during initialization step 102 . ECU 60 then executes reading step 104 , where at least one of coolant temperature sensor 62 and manifold air temperature sensor 64 is read by a respective one of coolant temperature input 60 b and manifold air temperature input 60 c . More particularly, ECU 60 reads the electrical signal issued by temperature sensor 62 and/or manifold air temperature sensor 64 indicative of T c and T l , respectively. Comparing step 106 is then performed by ECU 60 .

Comparing step 106 compares the sensed values of T c and/or T l with corresponding predetermined threshold values for T c and/or T l . If the sensed values of T c and/or T l exceed the corresponding threshold values priming valve 54 is activated. The threshold value for T c and T l are, for example, greater than from approximately 40 degrees Celsius to greater than approximately 100 degrees for T c , and greater than approximately 40 degrees Celsius to greater than approximately 75 degrees Celsius for T l .

Priming step 108 activates priming valve 54 . Input 54 c of priming valve 54 is electrically connected to priming valve control output 60 a of ECU 60 . Thus, the electrical signal on valve control output 60 a controls the flow of fluid through priming valve 54 . Priming valve 54 is closed when a corresponding electrical signal, such as, for example, a signal at approximately ground potential or a conventional logic-low voltage level, is issued by ECU 60 on priming valve control output 60 a . Similarly, priming valve 54 is opened when a corresponding electrical signal, such as, for example, a conventional logic-high voltage level, is issued by ECU 60 on priming valve control output 60 a . During priming step 108 , ECU 60 issues on priming valve control output 60 a a predetermined number of appropriate pulses to thereby activate, i.e., open, priming valve 54 . Thus, a predetermined amount of fuel passes from high-pressure fuel circuit 16 , through priming fuel circuit 18 , and into low-pressure fuel circuit 14 . More particularly, liquid fuel is supplied to or injected by priming valve 54 into first segment 52 a of priming fuel conduit 52 and into second segment 22 b of low-pressure fuel conduit 22 .

The fuel supplied to second segment 22 b of low-pressure fuel conduit 22 within low-pressure fuel circuit 14 supplies lift pump 26 with liquid fuel, thereby enabling lift pump 26 to pump more efficiently, i.e., pump a higher mass of fuel with each stroke. Further, the additional mass of liquid fuel increases the heat capacity of low-pressure circuit 14 , which is therefore able to absorb heat at a faster rate. Even further, the additional mass of liquid fuel increases the fuel pressure thereby suppressing vapor within low-pressure circuit 14 .

Referring now to FIG. 3, flow control device 120 is optionally fluidly connected to second segment 52 b of priming fuel conduit 52 , and includes flow-restricting orifice 122 , low-pressure orifice 124 , accumulator orifice 126 , armature 128 , spring 130 , and solenoid 132 . Flow control device 120 is especially suited for use in relatively “stiff” fuel systems, such as, for example, a fuel system having fuel conduits constructed of relatively rigid or stiff material, such as, for example, aluminum or steel tubing.

Generally, flow control device 120 selectively fluidly connects and disconnects accumulating device 140 with each of flow-restricting orifice 122 and low-pressure orifice 124 . More particularly, with armature 128 in a first or open position, flow control device 120 fluidly connects accumulating orifice 126 with low-pressure orifice 124 thereby connecting accumulating device 140 with second segment 52 b of priming fuel conduit 52 and, thus, with low-pressure fuel circuit 14 . In the first position, flow control device 120 via armature 128 fluidly disconnects flow-restricting orifice 122 from accumulating device 140 . With armature 128 in a second or closed position, flow control device 120 fluidly connects accumulating device 140 with flow-restricting orifice 122 , and contemporaneously fluidly disconnects accumulating device 140 from low-pressure orifice 124 . Thus, with armature 128 in the second position, accumulating device 140 fills with pressurized fuel though flow-restricting orifice 122 .

Flow control device 120 is disposed in series with second segment 52 b of priming fuel conduit 52 . More particularly, flow-restricting orifice 122 is fluidly connected to second segment 52 b of priming fuel conduit 52 , and low-pressure orifice 124 is fluidly connected to second segment 52 b of priming fuel conduit 52 at a point downstream from flow-restricting orifice 122 . Accumulating orifice 126 is fluidly connected to accumulating device 140 .

Flow-restricting orifice 122 restricts the rate of fuel flow into accumulating device 140 . Thus, accumulating device 140 fills with high-pressure fuel at a relatively slow, or reduced, rate relative to the rate at which accumulating device 140 would fill if fed by an unrestricted high-pressure fuel flow. Flow-restricting orifice 122 restricts flow by, for example, having a reduced diameter, such as, for example, ten-thousandths (0.010) of an inch.

Armature 128 is selectively placed into one of the first and second positions, as described above, through the selective energizing and de-energizing of solenoid 132 by ECU 60 . Solenoid 132 is electrically connected to ECU 60 by wires 134 . Armature 128 carries sealing member 142 . With armature 128 in the second or closed position, sealing member 142 is disposed in sealing engagement with low-pressure orifice 124 , to thereby fluidly isolate low-pressure orifice 124 from accumulating device 140 and fluidly connect accumulating device 140 with high-pressure orifice 122 . Thus, accumulating device 140 is allowed to fill with pressurized fuel. With armature 128 in the first or open position, sealing member 142 is disposed in sealing engagement with high-pressure orifice 122 , thereby fluidly isolating high-pressure orifice 122 from accumulating device 140 and fluidly connecting accumulating device 140 with low-pressure orifice 124 . Thus, pressurized fuel is permitted to flow from accumulating device 140 through fuel priming conduit 52 and into second segment 22 b of low pressure fuel circuit 14 .

The operation of flow control device 120 is controlled by ECU 60 , or an ignition switch (not shown) to which it is electrically interconnected. ECU 60 selectively energizes and de-energizes coil 144 which is associated with armature 128 , and, in turn, carries sealing member 142 into and/or out of engagement with one of high-pressure orifice 122 and low-pressure orifice 124 . Alternatively, actuation of the ignition switch energizes coil 144 for a fixed period of time during each engine start cycle.

In the embodiment shown, coolant temperature sensor 62 and manifold air temperature sensor 64 are each read by ECU 60 , and priming valve 54 is activated dependent at least in part upon the indications of T c and T l obtained therefrom. However, it is to be understood that the operation of the priming valve can be dependent at least in part upon a single sensor used to sense one of manifold air temperature and coolant temperature.

Further, the present invention can be alternately configured to activate the priming valve automatically, regardless of manifold air and coolant temperature. In such an embodiment, the addition of a fuel accumulation device or means 140 , such as, for example, a spring diaphragm or a canister, may be required. Further, such an embodiment is compatible for engines and/or marine vehicles that do not include an ECU.

In the embodiment shown, high-pressure fuel pump 30 and pressure regulator 34 are disposed within, or integrated with, vapor separator 20 . However, it is to be understood that the high-pressure fuel pump and the pressure regulator can be alternately configured, such as, for example, separate components disposed externally of the vapor separator.

In the embodiment shown, ECU 60 compares, in comparing step 100 , T c and/or T l with predetermined threshold values. If priming is required, ECU 60 issues a predetermined number of pulses on priming valve control output 60 a . However, it is to be understood that the method of the present invention can be alternately configured, such as, for example, conducting the added step of determining the amount of fuel to route from the high-pressure circuit to the low-pressure circuit. In such an embodiment, ECU 60 references a look-up table or other cross-reference table stored in random access or read-only memory of ECU 60 . The look-up table provides the number of electrical pulses to be output on priming valve control output 60 a for a range of values of T c and/or T l .

While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the present invention using the general principles disclosed herein. Further, this application is intended to cover such departures from the present disclosure as come within the known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.