Internal-combustion engines – Charge forming device – Combined liquid and gaseous fuel
Reexamination Certificate
1999-10-13
2001-11-13
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Combined liquid and gaseous fuel
C123S527000, C123S497000
Reexamination Certificate
active
06314947
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to vehicle fuel systems and more particularly, to a fuel delivery system utilizing two pressure sources for the delivery of fuel.
BACKGROUND OF THE INVENTION
Vehicles in use today may be powered by a wide-range of fuels such as leaded and unleaded gasoline, diesel fuel, methane and propane, to name a few. Whatever fuel is used to power a vehicle, the vehicle fuel system is specifically designed to continually supply fuel for the satisfactory operation of the engine. The fuel systems for the different fuels may vary from one another to account for the different properties of the various fuels.
For instance, some gasoline fuel systems, such as those used to supply fuel to marine engines, utilize a low pressure fuel pump disposed within the fuel tank to deliver fuel to a high pressure fuel pump downstream of the fuel tank which further increases the pressure of the fuel before delivery to the engine. Indeed, in some fuel delivery systems more than two fuel pumps may be used to provide fuel to the engine. Typically, at least one of the fuel pumps is electrically powered and thus, increases the power demand on the vehicle electrical system. Further, under at least some vehicle operating conditions, fewer than all of the fuel pumps in the fuel system may be needed to supply the engine fuel demand, and thus, operating all of the fuel pumps provides an unnecessary, excess fuel supply.
In propane fuel systems, the in-tank pressure of the propane is sufficient, at most operating temperatures, to discharge a pressurized propane supply from the tank into the engine for the satisfactory operation of the engine. However, the pressure of propane decreases dramatically at low temperatures and at about −40° F. for some grades of propane, the pressure will be about 0 PSI. Thus, during these very low pressure conditions within the propane tank the supply of propane to the engine may be severely reduced if not terminated thereby adversely affecting the performance of the engine.
SUMMARY OF THE INVENTION
A fuel delivery system is provided which selectively controls two pressure sources to deliver fuel from a tank to the engine for consumption by the engine. The fuel system has a pair of fuel supply passages through which fuel is discharged from the fuel tank to a main fuel supply line for delivery to the engine. One fuel passage communicates with an outlet of a fuel pump disposed within the fuel tank. The second fuel passage permits fuel to flow out of the fuel tank into the main fuel supply line independently of the fuel pump within the tank. Preferably, a valve is disposed in the second fuel passage to selectively permit fuel flow through the second fuel passage. The fuel system also has a controller which selectively provides power to the fuel pump so that the fuel pump in the fuel tank operates only when it is needed to discharge fuel from the tank.
In one embodiment, a propane fuel system utilizes a pump within a propane tank to discharge propane under pressure to the engine when the pressure within the tank is insufficient to provide an adequate supply of propane to the engine. Desirably, a temperature sensor in the propane tank communicates with the controller so that when the temperature within the tank is below a predetermined threshold temperature, which corresponds to a threshold pressure within the tank, the controller may activate the pump to supplement or provide entirely the flow of propane out of the tank for delivery to the engine. Conversely, when the propane tank temperature is above the threshold temperature, the pressure within the tank is sufficient to supply propane at an adequate rate and pressure to the engine independently of the pump. Thus, the power supplied to the pump is terminated by the controller to turn the pump off. This reduces the electrical power demand of the fuel system and extends the in-service life of the pump.
In another embodiment, a high pressure fuel pump downstream of the fuel tank discharges pressurized fuel for use by the engine and is the primary source of fuel to the engine. A second pump disposed within the vehicle fuel tank may be used to provide fuel from the fuel tank to the high pressure fuel pump, and is preferably only used during initial start-up of the engine to reduce the time required to prime the fuel system with fuel. Thereafter, the fuel pump may be deactivated with the primary fuel pump drawing fuel directly from the fuel tank for delivery to the engine. The primary fuel pump may be of substantially any kind including mechanical or electrical fuel pumps. The secondary, priming fuel pump is preferably electrical and is selectively activated by a controller which selectively provides electrical power to the pump. Desirably, the secondary fuel pump may be used to facilitate starting, warming up and initial operation of the engine and thereafter deactivated to reduce the electrical draw of the fuel system and to extend the in-service life of the secondary fuel pump.
Objects, features and advantages of this invention include providing a fuel system which efficiently supplies fuel to an engine through two pressure sources, reduces the electrical demand of the fuel system, extends the life of an in-tank fuel pump, efficiently and selectively operates the in-tank fuel pump, ensures an adequate fuel supply to the engine, improves the priming and initial operation of a vehicle fuel system, may be used with substantially any type of fuel including, but not limited to propane, diesel and gasoline fuels, is of relatively simple design and economical manufacture and assembly, is reliable, durable and has a long and useful in-service life.
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Miller Carl S.
Reising Ethington, Barnes, Kisselle, Learman & McCulloch, P.C.
Walbro Corporation
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