Abstract:
A system and method for fuel balancing is disclosed. The system and method measures the difference in fuel levels between two fuel tanks. In one case, when the difference in the two fuel levels exceeds a predetermined amount, an indicator is activated. In another case, when the difference in the two fuel levels exceeds a predetermined amount, the fuel is only drawn from the fuel tank containing the most fuel.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention is related to the field of fuel systems, and in particular, to balancing fuel usage between multiple fuel tanks.  
         [0003]     2. Description of the Prior Art  
         [0004]     Large trucks typically have multiple fuel tanks. In many cases these tanks are distributed on each side of the trucks. The fuel tanks may hold large amounts of fuel in each tank. Due to the large amount of fuel held in each fuel tank, the weight of the fuel may be substantial. If the truck uses all the fuel from one fuel tank on one side of the truck before using any fuel from a corresponding fuel tank on the other side of the truck, the truck may become unbalanced due to the uneven distribution of fuel between the two tanks. Currently this problem is solved by connecting the fuel tanks on either side of the truck with a pipe attached to the bottoms of the two fuel tanks. Connecting the fuel tanks with a pipe effectively creates one large fuel tank. As fuel is drawn from either tank, gravity keeps the level of fuel in both fuel tanks equal. Unfortunately, this system has problems. If a leak occurs in either fuel tank, or in the pipe connecting the fuel tanks, all the fuel from both fuel tanks may be lost. In addition, the pipe connecting the two fuel tanks must be connected at the bottom of the fuel tanks. This may create a low clearance area that extends from one side of the truck to the other side of the truck. In many cases, due to the low clearance, the pipe becomes damaged with a resultant loss of fuel.  
         [0005]     Another solution used today is a pump system that can transfer fuel back and forth between the two fuel tanks. This system works well but is costly to implement.  
         [0006]     Therefore there is a need for a different system and method for fuel balancing.  
       SUMMARY OF THE INVENTION  
       [0007]     A system and method for fuel balancing is disclosed. The system and method measures the difference in fuel levels between two fuel tanks. In one case, when the difference in the two fuel levels exceeds a predetermined amount, an indicator is activated. In another case, when the difference in the two fuel levels exceeds a predetermined amount, the fuel is only drawn from the fuel tank containing the most fuel.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a block diagram of fuel system  100  in an example embodiment of the invention.  
         [0009]      FIG. 2   a  is an isometric view of one example implementation of a switching device using two solenoids.  
         [0010]      FIG. 2   b  is an isometric view of one example implementation of a switching device using two solenoids connected in a fuel system.  
         [0011]      FIG. 3  is a flow chart showing one example embodiment of the invention.  
         [0012]      FIG. 4  is a flow chart showing another example embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]      FIGS. 1-4  and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of the invention. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. As a result, the invention is not limited to the specific examples described below, but only by the claims and their equivalents.  
         [0014]      FIG. 1  is a block diagram of fuel system  100  in an example embodiment of the invention. Fuel system  100  comprises fuel tanks  102  and  104 , switching device  106 , fuel lines  108 ,  110 , and  112 , fuel pump  114 , fuel gages  118  and  120 , comparator  122 , and indicator  124 . Fuel tank  102  is connected to switching device  106  by fuel line  108 . Fuel tank  104  is connected to switching device  106  by fuel line  110 . Switching device  106  is connected to fuel pump  114  by fuel line  112 . Switching device is configured to switch the connection from fuel pump  114  to one of the two fuel tanks. Fuel gage  118  is attached to fuel tank  102  and configured to measure the amount of fuel in fuel tank  102 . Fuel gage  120  is attached to fuel tank  104  and configured to measure the amount of fuel in fuel tank  104 . Comparator  122  is connected to fuel gage  118  and to fuel gage  120  and configured to determine a difference between the amount of fuel in fuel tank  102  and the amount of fuel in fuel tank  104 . Comparator  122  is connected to indicator  124  and to switching device  106 .  
         [0015]     In one example embodiment of the invention, comparator  124  determines the difference between the amount of fuel in the two fuel tanks ( 102  and  104 ) by using the signals from fuel gages  118  and  120 . When the difference exceeds a predetermined amount, comparator will activate indicator  124  to indicate that a fuel imbalance has occurred. A user can then activate switching device  106  and change which fuel tank is currently being used.  
         [0016]     In another example embodiment of the invention, comparator  124  determines the difference between the amount of fuel in the two fuel tanks ( 102  and  104 ) by using the signals from fuel gages  118  and  120 . When the difference exceeds a predetermined amount, comparator will activate switching device  122  and change which fuel tank is currently being used.  
         [0017]     Comparator  122  may be implemented in hardware as a simple differential circuit, as firmware running on a processor, or the like. Fuel gages  118  and  120  may be implemented as level detectors that measure the fluid level inside the fuel tanks (for example float gages), as strain gages that measure the weight of the fuel tanks, or the like.  
         [0018]     Switching device  106  may be implemented in any number of ways. In one example embodiment of the invention, switching device may be implemented as a 3-way valve. In another example embodiment of the invention, switching device  106  may be implemented as two 2-way solenoids feeding into a common manifold that is connected with the fuel pump.  FIG. 2   a  is an isometric view of one example implementation of a switching device  206  using two solenoids. Solenoids  232  and  234  have input ports  240  and  242  respectively. Solenoids  232  and  234  switchably connect their respective input ports to common output manifold  248 .  FIG. 2   b  is the switching device from  FIG. 2   a  in a fuel system. A fuel line from a first fuel  202  tank attaches to the input port of solenoid  232 . A fuel line from a second fuel tank  204  attaches to the input port of solenoid  234 . A fuel line attached at the common manifold leads to a fuel pump  214 . In operation, when fuel is to be drawn from the first fuel tank by the fuel pump, solenoid  232  would be open and solenoid  234  would be closed. When fuel is to be drawn from the second fuel tank by the fuel pump, solenoid  232  would be closed and solenoid  234  would be open. By switching which solenoid is open and which solenoid is closed, switching device  206  can determine which fuel tank is being used. In one example embodiment, fuel would only be drawn from one tank at a time.  
         [0019]     In another example embodiment, both solenoids may be open and allow fuel to be drawn from both fuel tanks simultaneously. When comparator  122  detects an imbalance in the fuel amount between the two tanks that exceeds a predetermined amount, the solenoid corresponding to the fuel tank with the least amount of fuel would be closed. In this way fuel would be drawn from the fuel tank that had the most fuel. Once the fuel imbalance has been reduced or eliminated, the closed solenoid could be reopened such that once again the fuel would be drawn from both fuel tanks.  
         [0020]      FIG. 3  is a flow chart showing an example embodiment of the invention. At step  302  the difference in the amount of fuel in two fuel tanks is monitored. At step  304  the difference in the fuel levels is compared against a limit. When the difference is smaller than the limit, flow returns to step  302 . When the difference is larger than the limit, a fuel imbalance is indicated in step  306 . Any type of indicator may be used at step  306 . The indicator may be a visual indicator, for example a flashing light, a change in color, or the like. The indicator may be an audio indicator, for example a buzzer. The indicator could also be a combination audio/visual indicator.  
         [0021]      FIG. 4  is a flow chart showing another example embodiment of the invention. At step  402  the difference in the amount of fuel in two fuel tanks is monitored. At step  404  the difference in the fuel levels is compared against a limit. When the difference is smaller than the limit, flow returns to step  402 . When the difference is larger than the limit, the flow of fuel from the fuel tank with the least amount of fuel is stopped at step  406 . In one example embodiment where fuel is drawn from only one fuel tank at a time, the fuel flow is stopped in step  406  by switching the flow of fuel from one fuel tank to the other fuel tank. In another example embodiment where the fuel may be drawn from both fuel tanks simultaneously, the flow of fuel is stopped in step  406  by disabling the connection to the fuel tank that contains the least amount of fuel.  
         [0022]     The invention described above is not limited to implementations where the fuel pump is external to the fuel tanks. There could be multiple fuel pumps, one inside each fuel tank. There could also be more than 2 fuel tanks, for example 2 side fuel tanks and one center tank, or 2 fuel tanks on each side for a total of 4 fuel tanks. This invention applies to fuel systems for any type of fuel, for example diesel, gasoline, natural gas, and the like.