Patent Publication Number: US-7213580-B1

Title: Vehicle fuel supply system

Description:
TECHNICAL FIELD 
   The present invention relates to vehicle fuel systems, and more particularly to a fuel supply system for a vehicle equipped with a generator. 
   BACKGROUND OF THE INVENTION 
   Generator-equipped vehicles are known, examples of which include tractor-trailers, tour buses and recreational vehicles or “RVs”. These types of vehicles have many of the comforts of home such as interior lighting, stoves, microwaves, refrigerators, bathrooms and televisions, each of which require a source of electricity usually provided by a gasoline powered generator. The vehicle&#39;s main fuel tank may be tapped to supply fuel to a fuel reservoir that in turn supplies fuel to the generator even when the vehicle engine is not running. Prior to the present invention, preventing overfill of the fuel reservoir has been accomplished through a return line to the vehicle fuel tank or with a fuel level sensor and associated electronics that connect to the vehicle&#39;s ECM (electronic control module) to turn the pump on and off, and which therefore add to the vehicle cost. 
   It would therefore be desirable to have a fuel supply system for a generator-equipped vehicle that does not require a fuel return line to the vehicle fuel tank, or a fuel level sensor and associated electronics of the prior art. 
   SUMMARY OF THE INVENTION 
   The present invention successfully addresses the above need by providing a fuel system for powering both the engine and a generator of any generator-equipped vehicle and which controls, without a fuel level sensor or associated fuel level control electronics, the fuel level in the fuel reservoir which supplies fuel to the generator. 
   More particularly, in an embodiment of the invention, a fuel system is provided having a primary fuel tank with a first fuel line for supplying fuel to the engine of the vehicle. A second fuel line extends from the primary fuel tank and delivers fuel to a fuel reservoir which in turn supplies fuel to a generator. A solenoid fuel pump is provided along the second fuel line to pump fuel from the primary tank to the fuel reservoir. To prevent overfill of the reservoir, a fuel shut-off valve is provided at the appropriate height in the reservoir. The valve is normally open and will close when the fuel level reaches the closing height of the valve. 
   The valve includes a valve body having a movable component that has a predetermined buoyancy in fuel. A spring surrounds the component and has a predetermined spring force which, when combined with the buoyancy force of the component, closes the valve when the fuel level reaches the closing height of the valve. The combined component buoyancy and spring force is greater than the force of fuel flow from the solenoid pump. As such, when the valve closes, the pump stops pumping fuel into the reservoir without the need for electronic control thereof. 
   With the valve closed and the pump not pumping fuel into the reservoir, fuel still flows from the reservoir to the generator which will thus continue to operate. As the generator uses fuel from the reservoir, the fuel level in the reservoir continues to fall. Once the fuel level has dipped below the valve closing height in the reservoir, the buoyancy force is no longer present and the force of fuel at the valve inlet overcomes the spring force to open the valve and thereby allowing the pump to again pump fuel from the primary fuel tank into the reservoir. This cycle is continuously repeated to permit continuous running of the generator. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
       FIG. 1  is a block diagram in accordance with a preferred embodiment of the invention; 
       FIG. 2  is a block diagram in accordance with an alternate embodiment of the invention; 
       FIG. 3  is a simplified cross-sectional view of an embodiment of a fuel shut-off valve of the present invention with the valve shown in the open position; and 
       FIG. 4  is the view of  FIG. 3  showing the valve in the closed position. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the drawing, there is seen in  FIG. 1  a simplified block diagram of a preferred embodiment of the invention. In the embodiment of  FIG. 1 , fuel supply system  10  is provided for supplying fuel to a vehicle&#39;s engine  12  and also to a generator  14 . Such generators  14  are used to power various electrical systems and appliances found in certain vehicles such as RVs and tour buses as explained above. Such electrical systems and appliances may include interior lighting, stoves and microwaves, refrigerators, televisions, bathrooms and heating and air-conditioning, for example, as indicated at  16 . 
   Fuel supply system  10  includes the main vehicle fuel tank  18  including a first fuel line  20  leading to the vehicle engine  12 . A second fuel line  22  extends from fuel tank  18  to supply fuel to a fuel reservoir  26  which in turn pumps fuel via a reservoir pump  27  to the generator  14  via third fuel line  29 . A solenoid fuel pump  24  is provided along the second fuel line  22  to pump fuel from the primary tank  18  to the fuel reservoir  26 . To prevent overfill of the reservoir  26 , a fuel shut-off valve  28  is provided at the appropriate height in reservoir  26 . Valve  28  opens under the force of fuel entering valve inlet  38  but will close when the fuel level in reservoir  26  reaches the closing height of valve  28 . 
   In the preferred embodiment of  FIG. 1 , a fuel vapor vent valve  11  is provided in reservoir  26  and leads via line  15  to an air cleaner  13  which also connects to generator  14  via line  15 ′. A fuel vapor vent valve  17  is also provided in main vehicle tank  18  which leads via line  19  to canister  21  having a fresh air intake  23 . Canister  21  connects to a purge valve  25  which also connects to the vehicle engine  12 . 
   In the alternate embodiment of  FIG. 2 , reservoir fuel vapor vent valve  11  leads via line  31  to a canister  40  which also connects to generator  14 . 
   Referring to  FIGS. 3 and 4 , valve  28  includes a valve body having upper and lower parts  30 ,  32  which snap-fit together, although other valve types and configurations are of course possible. Valve  28  includes a suitably shaped, movable valve component  34  that has a predetermined buoyancy in liquid fuel indicated at  50 . A spring  36  surrounds valve component  34  and has a predetermined spring force. When the fuel level in the reservoir  26  is below the closing height of valve  28 , component  34  exerts essentially no upward buoyancy force. The force of spring  36  alone is less than the force of fuel entering inlet  38  by pump  24 . As such, when the fuel level in reservoir  26  is below the closing height of the valve, component  34  is forced downward to the open position seen in  FIG. 3 . One or more fuel outlets  33  are provided at the valve body lower part  32  wherethrough fuel flows from the inlet  38  and into the reservoir  26 . Thus, when the valve is open, fuel enters the valve through inlet  38 , passes over component  34  and spring  36 , and exits at fuel outlets  33 . 
   When the fuel level in reservoir  26  reaches the closing height of valve  28 , enough fuel is present about component  34  inside valve body  30  that component  34  exerts an upward buoyancy force. The buoyancy force of component  34  and the spring force of spring  36  when combined is greater than the force of fuel flow entering inlet  38  from the solenoid pump  24 . As such, when the fuel level reaches the closing height of the valve, the component  34  moves upward to the closed position seen in  FIG. 4 . In this position, valve seal  35  presses against valve seat  37 , closing inlet  38 . When the valve  28  closes, the pump  24  is unable to pump fuel into the reservoir  26  and pump  24  will therefore idle when valve  34  is closed. It will therefore be appreciated that the solenoid pump  24  is controlled through the action of valve  28 , and therefore does not require any external electronic control logic to switch between pumping and not pumping. 
   With the valve  28  closed and the solenoid pump  24  not pumping, fuel is still pumped by the reservoir pump  27  from the reservoir  26  through third fuel line  29  to the generator  14  which will thus continue to operate. As the generator  14  uses fuel from the reservoir  26 , the fuel level in the reservoir  26  continues to fall. Once the fuel level has dipped below the valve closing height in the reservoir  26 , the valve  34  opens due to the lack of a buoyancy force such that the force of the fuel at inlet  38  overcomes the force of spring  36  and moves component  34  to the open position seen in  FIG. 3 . 
   Although the specific valve configuration, valve component buoyancy and spring force may vary depending on the specific fuel system design being employed, the following provides an example of acceptable force values: 
   EXAMPLE 1 
   Solenoid pump: About 6 PSI. acting on a 1 mm (0.040″) valve inlet orifice. Combined component buoyancy and spring force: About 0.07 Newtons. 
   While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.