Abstract:
A fuel storage and distribution system for heavy and medium duty trucks which include dual fuel tanks ( 24, 26 ). An electric transfer pump ( 22 ) transfers fluid from the tank with the greatest volume to the tank with the lowest volume. Fuel level sensors ( 18, 20 ) measure the fluid levels in the fuel tanks ( 24, 26 ) and provide inputs to the electric transfer pump ( 22 ). Fuel may be transferred in either direction between the two fuel tanks.

Description:
This appln is a 371 of PCT/US00/25017 filed Sep. 13, 2000 which claims benefit of Prov. No. 60/155,051 filed Sep. 21, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to fuel transfer from a plurality of fuel tanks to the engine of a vehicle, and more particularly, to a method and apparatus for maintaining substantially equivalent fuel levels within the plurality of fuel tanks. 
     2. Description of the Related Art 
     Vehicles such as, for example, heavy and medium duty trucks commonly employ a dual tank configuration providing a large fuel capacity. The two tanks are positioned on opposing sides of the truck. Such dual tank configurations are troublesome to fill. Either two fuel dispensers must be used (one on either side of the truck), or the truck must be turned around so that both fuel tanks may be filled using a single fuel dispenser. 
     As is known in the art of internal combustion powered vehicles, fuel pumps remove more fuel from fuel tanks than is utilized in the engine so as to cool the fuel injector pump. The surplus fuel which is not used by the engine is constantly returned to the fuel tank. In the dual tank configurations currently utilized with heavy and medium duty trucks, fuel is drawn from and returned to both fuel tanks simultaneously. These systems do not draw fuel evenly from both tanks nor do they return fuel evenly to both tanks. Uneven fuel draw and return can be attributed to many factors affecting fluid flow, including pressure differentials and physical attributes of the fluid distribution system including, but not limited to partial blockage of distribution piping. Spillage may occur if fuel is drawn primarily from one of the two tanks and fuel is returned primarily to the other of the two tanks. 
     Roads and parking areas are generally formed with a crowned configuration leading to one of the two fuel tanks being lower relative to the other. Fuel is more easily drawn from the higher tank and consequently the lower tank has less fuel drawn from it. This exacerbates the problem of uneven fuel draw and the consequent spillage which can occur. 
     Uneven fuel draw and return additionally causes balance problems when one of the two fuel tanks contains significantly more fuel than the other. Hydrocarbon fuel typically weighs approximately 6 lbs. per gallon and the fuel tanks in question generally have a capacity of approximately 100 gallons. The substantial weight differential caused by an uneven amount of fuel in the two tanks can cause maintenance and other problems for the truck operator including, for example, uneven tire wear. An additional problem associated with the dual tank configuration occurs when one of the two tanks is emptied and air is drawn into the engine from the fuel supply line connected to the empty tank. When air is drawn into the engine, engine stall is experienced and restarting the engine is problematic. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to improve upon the aforementioned fuel storage and distribution systems for heavy and medium duty trucks wherein it is desired to utilize a dual tank configuration in which the fuel levels in both tanks remain substantially equal. The present invention provides an electric transfer pump configured to be in fluid communication with both fuel tanks. Fluid level sensors measure the fluid level in both fuel tanks and are communicatively connected to the electric transfer pump. When the fluid level in one of the tanks reaches a predetermined lower level than in the other tank, the electric transfer pump distributes fuel from the tank having the greater fuel volume to the other tank. The electric transfer pump may be configured so that fuel can be transferred in either direction between the two fuel tanks. 
     In one form of the current invention, the first of the two fuel tanks is in direct fluid communication with the engine whereby fuel is supplied to the engine from the first tank and excess fuel returning from the engine is returned to the first tank. Fuel level sensors are operatively connected to both fuel tanks. Fluid level measurements from the two fuel level sensors are communicated to an electric transfer pump. The electric transfer pump includes a computational/control device such as a microprocessor or a programmable logic controller which evaluates the two fuel level signals and determines whether fuel should be transferred from the second fuel tank to the first fuel tank. Fuel is transferred when the fuel level in the first fuel tank reaches a predetermined lower level than the fuel level in the second fuel tank. 
     The computational/control device can be contained within the electric transfer pump as described above or may be placed in the standard truck circuit board which controls other truck electric operations. The electric transfer pump may, for example, take the form of a pulse width modulated solenoid pump or a DC motor driven positive displacement pump. 
     An advantage of the present invention is the ability to prevent fuel spillage in a dual fuel tank configuration by eliminating the possibility that more fuel is returned to a fuel tank than is taken from the fuel tank. 
     Another advantage of the present invention is the ability to maintain substantially equal fuel volumes within a dual tank configuration and thus eliminate balance problems associated with unequal fuel volumes. 
     A further advantage of the present invention is the ability to eliminate engine stall occurring as a result of air being drawn from an empty fuel tank. 
     Yet another advantage of the present invention is the ability to utilize the electric transfer pump to transfer fuel provided to one fuel tank to the other fuel tank while fueling so that the problems associated with filling a pair of fuel tanks on opposing sides of a vehicle are not experienced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a schematic representation of an embodiment of the fuel distribution system of the present invention; 
     FIG. 2 is a schematic representation of another embodiment of the fuel distribution system of the present invention; and 
     FIG. 3 is a schematic representation of yet another embodiment of the fuel distribution system of the present invention. 
    
    
     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. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings and particularly to FIG. 1, there is shown fuel transfer system  10  including first tank  24 , second tank  26  and pump  22 . Pump  22  is in fluid communication with both first tank  24  and second tank  26  and is operative to transfer fuel from second tank  26  to first tank  24 . 
     As depicted in FIG. 1, engine  12  is in direct fluid communication with first tank  24 . Pump  42  is located within first tank  24  and is in direct fluid communication with supply line  14 . Supply line  14  is in direct fluid communication with engine  12  and is operable to supply fuel from first tank  24  to engine  12  at the required rate. Return line  16  is in fluid communication with both engine  12  and first tank  24  and is operative to return excess fuel from engine  12  to first tank  24 . 
     First fuel level sensor  18  is located within first tank  24  and includes float  32 . Float  32  remains above the fuel surface in first tank  24  and provides a resistance value to first fuel level sensor  18 . First fuel level sensor  18  is operable to utilize the resistance value from float  32  to determine the amount of fuel in first tank  24 . First fuel level sensor  18  is communicatively connected to fuel gauge  44  and to transfer pump  22 . Fuel gauge  44  is positioned on the truck dash or other convenient location where the driver may monitor fuel gauge  44 . 
     Second fuel level sensor  20  is similarly located within second tank  26  and includes float  32 . Second fuel level sensor  20  operates to determine the amount of fuel in second tank  26  as described above with reference to first fuel level sensor  18 . Second fuel level sensor  20  is communicatively connected to transfer pump  22 . First and second fuel level sensors  18 ,  20  can be float-type sensors as depicted in FIGS. 1 and 2 or can be any of the many pressure sensors known in the art. 
     First and second fuel level sensors  18 ,  20  are communicatively connected to pump  22  via first communication line  34  and second communication line  36 , respectively. Pump  22  is in fluid communication with first tank  24  and second tank  26  by way of first transfer line  28  and second transfer line  30 , respectively. FIG. 2 depicts an embodiment of the current invention wherein transfer pump  22  is further communicatively connected to controller  40  wherein controller  40  is located remotely from transfer pump  22 . Controller  40  may comprise an output driver added to the existing circuit board. Controller  40  is communicatively connected to first and second fuel level sensors  18 ,  20 . This communicative connectivity may be achieved through pump  22 , or through direct connection of controller  40  to both first and second fuel level sensors  18 ,  20  (not shown). 
     Additionally an electrical connection  46  can be made between the engine and controller  40  to provide an input to controller  40  indicating that the engine is either running or not running. The signal provided on line  46  could be an indication of the rpms of the engine, oil pressure or the like. Thus a signal provided on line  46  from the engine to controller  40  could cause controller  40  to either enable or disable pump  22  depending on the transmitted signal. For instance, pump  22  should not operate when the engine is not running to avoid pumping fuel on the ground in a worst case scenario such as in case of a crash of the vehicle. 
     FIG. 3 depicts an embodiment of the current invention wherein pump  22  is directly communicatively connected to stepper motor  50  via fourth communication line  48 . Stepper motor  50  is further mechanically coupled to fuel gauge  44  via step connection  50 . In this embodiment, fuel gauge  44  is not connected to first fuel level sensor  18 . Stepper motor  50  actuates fuel gauge  44  in response to fuel transfer via pump  22 . Stepper motor  50  may be integral with fuel gauge  44 . 
     First tank  24  and second tank  26  can contain baffles (not shown) which are operative to reduce the sloshing of fuel while the vehicle is in motion. However, baffles do not completely eliminate fuel slosh and therefore electronic dampening is provided. Electronic dampening is provided in the current invention by utilizing average fuel level measurements from first and second fuel level sensors  18 ,  20 . A preset time frame over which fuel level values are averaged is entered into the controller. Average fuel levels over this preset time frame are then compared and utilized to control pump  22 . In this way excessively high or excessively low fuel values due to slosh will not cause actuation of pump  22  and lead to unnecessary transfer of fuel. 
     In operation, the controller of the current invention works to maintain a substantially equivalent fuel level in first tank  24  and second tank  26 . As the engine uses fuel, the fuel level in first tank  24  decreases. As the fuel level in first tank  24  drops below the fuel level in second tank  26  by a predetermined amount, the controller signals transfer pump  22  to transfer a predetermined amount of fuel from second tank  26  to first tank  24 . In one embodiment, the controller does not deliver a predetermined amount of fuel from second tank  26  to first tank  24 , but rather actuates transfer pump  22  until the fuel levels in first tank  24  and second tank  26  are substantially equal. The fuel level in first tank  24  is sensed by first fuel sensor  18  and is thereafter communicated to a controller located within transfer pump  22  or to a remotely located controller  40 . The fuel level of second tank  26  is similarly sensed by second fuel level sensor  20  and communicated to the controller. The controller evaluates the thusly communicated fuel level values and actuates pump  22  as necessary. Pump  22  has sufficient flow resistance to prohibit siphoning from second tank  26  to first tank  24 . An internal check valve (not shown) prevents siphoning from first tank  24  to second tank  26 . 
     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 invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.