Patent Publication Number: US-7725271-B2

Title: Nozzle snap flow compensation

Description:
FIELD OF THE INVENTION 
   The present invention generally relates to accurately measuring a volume of fuel dispensed through a fuel dispenser. More particularly, the present invention relates to compensating the total volume of fuel dispensed, as measured by the fuel dispenser, for events that occur during fueling that can adversely effect the accuracy of the total volume measured. 
   BACKGROUND OF THE INVENTION 
   In a typical fuel dispensing transaction, a customer arranges for payment, either by paying at the fuel dispenser with a credit card or debit card, or by paying a cashier. Next, a fuel nozzle is inserted into the fill neck of the vehicle, or other selected container, and fuel is dispensed. Displays on the fuel dispenser indicate how much fuel has been dispensed as well as a dollar value of the purchase. Dependent upon the timing and manner of payment for the fuel, either the customer terminates the flow of fuel into the vehicle by manually releasing the fuel nozzle, or the fuel dispenser automatically terminates the flow of fuel either at a pre-selected dollar amount or when the tank of the vehicle is full. In either case, the closing of the fuel valve within the fuel nozzle is herein referred to as a “nozzle snap event.” 
   During such operations, a series of valves are opened and closed along the fuel flow path within the fuel dispenser. Referring now to  FIG. 1 , a schematic of a typical prior art fuel dispenser  100  is shown. As shown, fuel is pumped from an underground storage tank  102  through a fuel pipe  104  to a flexible fuel hose  105  which terminates with a fuel nozzle  106  including a fuel valve  108 . To initiate fuel flow, the customer manually activates a trigger on fuel nozzle  106  which opens fuel valve  108  so that fuel is dispensed into the vehicle. Fuel flow through fuel valve  108  is detected by a flow switch  116  which, as shown, is a one-way check valve that prevents rearward flow through fuel dispenser  100 . Once fuel flow is detected, flow switch  116  sends a signal on communication line  124  to a control system  120 . Control system  120  is typically a microprocessor, a microcontroller, or other electronics with associated memory and software programs. Upon receiving the flow initiation signal from flow switch  116 , control system  120  starts counting the pulses from a pulser  118 . The pulses are generated by the rotation of a fuel meter  114  and are directly proportional to the fuel rate being measured. 
   As is known, fuel dispensers keep track of the amount of fuel dispensed so that it may be displayed to the customer along with a running total of how much the customer will have to pay to purchase the dispensed fuel. This is typically achieved with fuel meter  114  and a pulser  118 . When fuel passes through fuel meter  114 , it rotates and pulser  118  generates a pulse signal, with a known number of pulses being generated per gallon of fuel dispensed. The number of pulse signals generated and sent to control system  120  on communication line  126  are processed to arrive at an amount of fuel dispensed and an associated cost to the customer. These numbers are displayed to the customer to aid in making fuel dispensing decisions. As well, control system  120  uses the information provided by fuel meter  114  to regulate the operation of valve  112  during fueling operations. 
   As shown, fuel dispenser  100  includes a turbine style fuel meter  114 , such as that disclosed in U.S. Pat. No. 7,028,561, which is hereby incorporated by reference in its entirety. Flow switch  116  is used in conjunction with turbine fuel meter  114  since the possibility exists that the rotors (not shown) of fuel meter  114  can bind during use, yet still allow fuel to pass through the meter. As such, pulser  118  does not create pulses, and the flow of fuel can go undetected. However, fuel switch  116  detects fuel flow and sends a signal to control system  120 , allowing control system  120  to detect the flow error. Other designs of non-positive displacement type fuel meters can be prone to this same issue. 
   Fuel flow through fuel nozzle  106  is terminated by a nozzle snap event, that event being caused either manually by the customer or automatically by fuel dispenser  100 . As fuel valve  108  snaps shut, fuel flow through flow switch  116  begins to decrease and flow switch  116  begins to shut. As flow switch  116  shuts, it generates a signal that indicates to control system  120  that fuel flow is being terminated. In response, control system  120  disregards any additional pulse signals that are generated by pulser  118 . 
   Potential inaccuracies may exist when attempting to determine the total volume of fuel dispensed from the typical fuel dispenser discussed above when nozzle snaps occur. A typical fuel supply pressure for fuel dispenser  100  is 30 pounds per square inch (psi) upstream of valve  112 . As fuel is dispensed at increasing flow rates, the pressure differential between the fuel supply pressure and the fuel pressure at flow valve  108  increases. As shown in  FIG. 2 , a pressure differential of approximately 3 psi exists at a steady state flow rate of 2 gallons per minute (gpm), whereas at a flow rate of 10 gpm, the pressure differential is approximately 15 psi. When flow is terminated by a nozzle snap event, system pressure is equalized until fuel pressure along the entire fuel flow path is approximately equal to the supply pressure, in this case 30 psi. This occurs as fuel is added to the fuel flow path downstream of fuel meter  114  through flow switch  116 . 
   The additional volume of fuel added downstream of fuel meter  114  as pressure is equalized within the system is not added to the total volume of fuel dispensed, as measured by the fuel meter, since flow switch  116  sends a signal to control system  120  at the occurrence of the nozzle snap event indicating that further pulses from the fuel meter should be ignored. The additional, undetected volume of fuel is then dispensed to the tank of the vehicle when fuel flow is reinitiated. As seen in  FIG. 2 , the volume of fuel required for system pressure equalization increases along with the increase in the pressure differential between the fuel supply pressure and the fuel pressure at fuel valve  108 . Because the noted pressure differential increases as the flow rate at which fuel is dispensed increases, inaccuracies in measuring the total volume of fuel dispensed typically increase as the flow rate at which the fuel is being dispensed increases with nozzle snaps. 
   SUMMARY OF THE INVENTION 
   The present invention recognizes and addresses considerations of prior art constructions and methods. In one embodiment of the present invention, a fuel dispenser is configured to compensate a total dispensed fuel volume for an event that occurs during a fueling process. The fuel dispenser includes a fuel delivery path configured to deliver fuel to a vehicle, a display configured to display the total dispensed fuel volume, and a fuel meter configured to measure a fuel delivery rate at which fuel is being dispensed through the fuel delivery path to the vehicle. A data set has a plurality of fuel volume compensation values corresponding to a plurality of fuel delivery rate values, and a microprocessor is configured to calculate a volume of fuel dispensed to the vehicle based on the fuel delivery rate and retrieve a fuel volume compensation value from the data set. The fuel meter measures the fuel delivery rate at the time of the event, the microprocessor determines which fuel delivery rate value corresponds to the fuel delivery rate, retrieves the corresponding fuel volume compensation value, and adds the retrieved fuel volume compensation value to the volume of fuel dispensed as calculated by the microprocessor to obtain the total dispensed fuel volume. 
   In another embodiment, a method of compensating a volume of fuel measured by a fuel meter to obtain a total dispensed fuel volume for a fuel dispenser including a fuel flow path for dispensing fuel, includes detecting an event that occurs during a fueling operation, measuring a flow parameter value of the fuel within the fuel flow path at the time of the event, retrieving a fuel volume compensation value from a data set including a plurality of fuel volume compensation values that correspond to a plurality of flow parameter values, and adding the retrieved fuel volume compensation value to the volume of fuel measured by the fuel meter to obtain a total dispensed fuel volume. The retrieved fuel volume compensation value is selected by comparing the measured flow parameter value to the plurality of flow parameter values in the data set. 
   Other objects, features and aspects for the present invention are discussed in greater detail below. The accompanying drawings are incorporated in and constitute a part of this specification, and illustrate one or more embodiments of the invention. These drawings, together with the description, serve to explain the principals of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A full and enabling disclosure of the present invention, including the best mode thereof, to one of ordinary skill in the art, is set forth more particularly in the remainder of this specification, including reference to the accompanying drawings, in which; 
       FIG. 1  is a schematic diagram of a prior art fuel dispenser; 
       FIG. 2  is a graph depicting the relationship between the flow rates at which the fuel dispenser as shown in  FIG. 1  dispenses fuel, the pressure differentials that develop within the fuel dispenser and the resulting differences with regard to the amount of fuel actually dispensed as compared to the measured value of fuel dispensed; 
       FIG. 3  illustrates a fuel dispenser in accordance with an embodiment of the present invention; 
       FIG. 4  illustrates a fueling environment including the fuel dispenser as shown in  FIG. 3 ; 
       FIG. 5  is a graph showing flow compensation values corresponding to the operating fluid flow rates for the fuel dispenser as shown in  FIG. 3 ; 
       FIG. 6  is a flow chart depicting a method of creating the graph as shown in  FIG. 5 ; 
       FIG. 7  is a graph showing flow compensation values corresponding to the operating fluid flow rates for the fuel dispenser as shown in  FIG. 3 ; and 
       FIG. 8  is a flow chart depicting a method of accounting for fuel measurement inaccuracies in accordance with an embodiment of the present invention. 
   

   Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now be made in detail to presently preferred embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation, not limitation, of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope and spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     FIGS. 3 and 4  illustrate a fueling environment  60  including a central fuel station building  62  with a fuel station computer  66  in communication with a plurality of fuel dispensers  14   a  through  14   d , with a vehicle  12  being fueled by fuel dispenser  14   a . Fuel dispenser  14   a  includes a housing  16  with a flexible fuel hose  18  extending therefrom. Fuel hose  18  terminates in a manually operated nozzle  20  adapted to be inserted into a fill neck  22  of vehicle  12 . Fuel flows from an underground storage tank  26  through fuel dispenser  14   a , out through flexible fuel hose  18 , down fill neck  22  to a fuel tank  24  of vehicle  12 , as is well understood. Fuel dispenser  14   a  may be the ECLIPSE® or ENCORE® sold by the assignee of the present invention, or other fuel dispenser, such as that disclosed in U.S. Pat. No. 4,978,029, which is hereby incorporated by reference in its entirety. 
   The internal fuel flow components of one example of the present invention are illustrated in  FIG. 3 . As shown, fuel travels from one or more underground storage tanks  26   a  and  26   b  ( FIG. 4 ) by way of fuel pipes  70   a  and  70   b  associated with their respective underground storage tank. Fuel pipes  70   a  and  70   b  may be double-walled pipes having secondary containment, as is well known. An exemplary underground fuel delivery system is illustrated in U.S. Pat. No. 6,435,204, which is hereby incorporated by reference in its entirety. As shown, a submersible turbine pump  25  associated with underground storage tank  26   a  is used to pump fuel to fuel dispenser  14   a  through fuel pipe  70   a . Similarly, a submersible turbine pump (not shown) pumps fuel to fuel dispenser  14   a  through fuel pipe  70   b . Alternately, some fuel dispensers may be self-contained, meaning fuel is drawn to the fuel dispenser by a pump controlled by a motor (not shown) positioned within the housing. 
   Fuel pipes  70   a  and  70   b  pass into housing  16  through shear valves  72   a  and  72   b , respectively. Shear valves  72   a  and  72   b  are designed to cut off fuel flowing through their respective fuel pipes  70   a  and  70   b  if fuel dispenser  14   a  is impacted, as is commonly known in the industry. An exemplary embodiment of a shear valve is disclosed in U.S. Pat. No. 6,575,206, which is hereby incorporated by reference in its entirety. The dual fuel flow paths from underground storage tanks  26   a  and  26   b  to fuel nozzle  20  are substantially similar, and as such, for ease of description, only the flow path from underground storage tank  26   a  is discussed now. A fuel filter  75   a  and a proportional valve  78   a  are positioned along fuel line  70   a  upstream of fuel meter  40   a . Alternatively, proportional valve  78   a  may be positioned downstream of fuel meter  40 . Fuel meter  40   a  and proportional valve  78   a  are positioned in a fuel handling compartment  82  of housing  16 . Fuel handling compartment  82  is isolated from an electronics compartment  85  located above a vapor barrier  80 . Fuel handling compartment  82  is isolated from sparks or other events that may cause combustion of fuel vapors, as is well understood and as is described in U.S. Pat. No. 5,717,564, which is hereby incorporated by reference in its entirety. 
   Fuel meter  40   a  communicates through vapor barrier  80  via a pulser signal line  89   a  to a control system  86  that is typically positioned within electronics compartment  85  of fuel dispenser  14 . Control system  86  may be a microcontroller, a microprocessor, or other electronics with associated memory and software programs running thereon. Control system  86  typically controls aspects of fuel dispenser  14 , such as gallons display  30 , price display  32 , receipt of payment transactions, and the like, based on fuel flow information received from fuel meter  40   a.    
   Control system  86  regulates proportional valve  78   a , via a valve communication line  88   a , to open and close during fueling operations. Proportional valve  78   a  may be a proportional solenoid controlled valve, such as described in U.S. Pat. No. 5,954,080, which is incorporated herein by reference in its entirety. As control system  86  directs proportional valve  78   a  to open to allow increased fuel flow, the fuel enters proportional valve  78   a  and exists into fuel meter  40   a . The flow rate of the displaced volume of the fuel is measured by fuel meter  40   a  which communicates the flow rate of the displaced volume of fuel to control system  86  via pulser signal line  89   a . A pulse signal is generated on pulser signal line  89   a  in the example illustrated, such as by a Hall-effect sensor as described in U.S. Pat. No. 7,028,561, which is incorporated herein by reference in its entirety. In this manner, control system  86  uses the pulser signal from pulser signal line  89   a  to determine the flow rate of fuel flowing through fuel dispenser  14   a  and being delivered to vehicle  12 . Control system  86  updates the total gallons dispensed on gallons display  30  via a gallons display communication line  92 , as well as the price of fuel dispensed on price display  32  via a price display communication line  94 . 
   Rather than incorporating a physical sensor as a pulser, additional embodiments of the present invention may have a fuel meter included in application software of an associated microcontroller, microprocessor or electronics, that functions as the pulser. In these embodiments, a pulse signal is generated by the software that mimics the output of the physical sensor described above. As well, the software in these additional embodiments can be used to calculate the volume of fuel flowing through the fuel meter and provide this information to the control system. 
   As fuel leaves fuel meter  40   a , the fuel enters a flow switch  96   a . Flow switch  96   a  generates a flow switch communication signal via a flow switch signal line  98   a  to control system  86  to communicate when fuel is flowing through fuel meter  40   a . The flow switch communication signal indicates to control system  86  that fuel is actually flowing in the fuel delivery path and that subsequent pulser signals from fuel meter  40   a  are due to actual fuel flow. For those embodiments where application software of a microcontroller or microprocessor associated with the fuel meter functions as the pulser, the flow switch sends the flow switch communication signal indicating that flow has been initiated to the fuel meter rather than the control system. The signal indicates to the fuel meter software that it should begin producing output signals to the control system that mimic those of the previously discussed mechanical pursers. 
   After the fuel enters flow switch  96   a , it exits through fuel conduit  90   a  to be delivered to a blend manifold  91 . Blend manifold  91  receives fuels of varying octane values from the various underground storage tanks and ensures that fuel of the octane level selected by the consumer is delivered to the consumer&#39;s vehicle  12 . After flowing through blend manifold  91 , the fuel passes through fuel hose  18  and nozzle  20  for delivery into fuel tank  24  of vehicle  12 . Flexible fuel hose  18  includes a product delivery line  36  and a vapor return line  34 . Both lines  34  and  36  are fluidly connected to underground storage tank  26   a  through fuel dispenser  14   a . Once in fuel dispenser  14   a , lines  34  and  36  separate. 
   During delivery of fuel into the vehicle fuel tank, the incoming fuel displaces air in the fuel tank containing fuel vapors. Vapor is recovered from fuel tank  24  of vehicle  12  through vapor return line  34  with the assistance of a vapor pump  52 . A motor  53  powers vapor pump  52 . As discussed above, control system  86  receives information from fuel meter  40   a  and pulser  44   a  regarding the amount of fuel being dispensed. Fuel meter  40   a  measures the fuel being dispensed while pulser  44   a  generates a pulse per count of fuel meter  40   a . As shown, pulser  44   a  generates one thousand and twenty-four (1024) pulses per gallon of fuel dispensed. Control system  86  controls a drive pulse source  55  that in turn controls motor  53 . As previously noted, control system  86  may be a microprocessor, microcontroller, etc. with an associated memory that operates to control the various functions of the fuel dispenser including, but not limited: fuel transaction authorization, fuel grade selection, display and/or audio control. Vapor recovery pump  52  may be a variable speed pump or a constant speed pump with or without a controlled valve (not shown), as is well known in the art. 
   In addition to measuring the volume of fuel dispensed, fuel meter  40   a  of the preferred embodiment of the present invention also provides the function of compensating the total dispensed fuel volume, as measured by the fuel meter, in order to offset any inaccuracies caused by nozzle snap events. As previously discussed, nozzle snap events that occur when the flow of fuel through the dispenser&#39;s fuel nozzle  20  is terminated tend to allow an unmeasured volume of fuel to pass through fuel meters  40   a  and  40   b  as pressure is equalized within the fuel flow paths of the fuel dispenser. To compensate the total measured volume of fuel that has been dispensed for the unmeasured volume of fuel due to the nozzle snap event, fuel meters  40   a  and  40   b  measure various flow parameters within their respective fuel flow paths when the nozzle snap event occurs and retrieve a fuel volume compensation value (ΔV) that corresponds to the measured flow parameters. The fuel volume compensation values (ΔV) are retrieved from experimental data that is compiled through testing and then embedded in software of the fuel meters  40   a  and  40   b . The fuel volume compensation values (ΔV) are then added to the volume of fuel dispensed that was measured by fuel meters  40   a  and  40   b  up until the occurrence of the nozzle snap event. The fuel meters perform this function for each nozzle snap event. 
     FIG. 5  provides a graphical representation of fuel volume compensation value (ΔV) data as would be embedded in the software of the fuel meter of an exemplary embodiment of the present invention. Referring also to the flow chart shown in  FIG. 7 , one method of creating the fuel volume compensation value (ΔV) table as shown in  FIG. 5 , the fuel volume compensation value (ΔV) data table is created by first selecting a desired number of meters of the same type and model, for testing, as shown at step  200 , each fuel meter falling within acceptable calibration standards for that model. Next, as shown at step  202 , each fuel meter is installed in a test fuel dispensing system and data points are collected for individual nozzle snap events at various fuel flow rates for that meter. For example, as seen in  FIG. 5 , data points (represented by “x”) are collected for a first fuel meter at intervals of one gallon per minute flow rate from between one gallon per minute to 10 gallons per minute. As shown at step  204 , for each data point, fuel is dispensed into a measuring device, such as a graduated container, at different flow rates with no or minimum nozzle snap events. At step  206 , volume of fuel dispensed as measured by the fuel meter will be compared to the actual volume of fuel dispensed into the measuring device. 
   As previously discussed, occurrence of the nozzle snap event will typically lead to an unmeasured volume of fuel passing through the fuel meter as pressure within the fuel flow path is equalized after the flow of fuel is terminated. At step  208 , for each data point, fuel is dispensed into the same size graduated measuring device that was used at step  204 , at the different flow rates with multiple, for example 10, nozzle snaps. At step  210 , volume of fuel dispensed, as measured by the fuel meter, is compared to the actual volume of fuel dispensed into the measuring device. To determine the unmeasured volume of fuel that was caused by the nozzle snap events, the volume of fuel dispensed, as measured by the fuel meter, is subtracted from the actual volume of fuel that was delivered to the graduated measuring device for both tests without (steps  204  and  206 ), and with (steps  208  and  210 ), nozzle snaps, as shown in step  212 . This volume is then divided by the number of nozzle snap events from step  208  to determine a fuel volume compensation value per nozzle snap event. As shown in  FIG. 5 , this process is repeated at the selected interval of fuel flow rates, over the operating range of the fuel dispenser, as shown in step  214 . 
   The process of collecting data points discussed above is repeated for each of the selected fuel meters (in the instant case, second fuel meter and third fuel meter), as shown at step  216 . As would be expected, minor variations from meter to meter can occur for given fuel flow rates, resulting in a spread of data points, as shown in  FIG. 5 . As such, as shown at step  216 , a curve is fit to the spread of data points so that fuel flow compensation values (ΔV) are available across the continuous range of fuel flow rates in which the fuel meters and their associated dispensers operate. As shown in  FIGS. 5 and 7 , fuel flow compensation values (ΔV) can be recorded in different units of measure, such as cubic inches (in 3 ) or gallons (gal). 
   Note,  FIGS. 5 and 7  are merely graphical representations of an exemplary embodiment of a fuel flow compensation data table in accordance with the present invention. Fuel flow compensation data tables can be compiled for any number of fuel meters, including a single fluid fuel meter. As well, data points can be compiled for various flow rate intervals, such as at each half gallon per minute. 
   Referring now to the flow chart shown in  FIG. 8 , the method by which the fuel meters of the disclosed fuel dispenser compensate the total volume of fuel dispensed, as measured by the fuel meter, in order to offset any inaccuracies caused by nozzle snap events is discussed. As previously noted, nozzle snap events that occur when the flow of fuel through the dispenser fuel nozzle is secured may lead to an unmeasured volume of fuel passing through the fuel meter. To account for these potential inaccuracies, the fuel dispenser detects when a nozzle snap event occurs during the dispensing of fuel, as shown at step  300 . In the disclosed embodiments, the nozzle snap event is detected by flow switch  116  which detects the decrease in the flow of fuel as flow is terminated by fuel valve  108 , and a signal is sent to a respective fuel meter  40   a  or  40   b  or, control system  86 . Next, as shown in step  302 , the respective fuel meter  40   a  or  40   b  measures at least one flow parameter within the fuel flow path at the time of the nozzle snap event. In the preferred embodiment discussed herein, the fuel meter determines the flow rate at which fuel is being dispensed at the instant fuel valve  108  undergoes the nozzle snap event. 
   Next, as shown at step  304 , the microprocessor, microcontroller or electronics associated with the fuel meter enters the fuel volume compensation value data set discussed above and graphically shown in  FIGS. 5 and 7 , and retrieves a fuel volume compensation value (ΔV) that corresponds to the value of the measured flow parameter. For example, from the data set as shown in  FIG. 7 , for a flow rate of 8 gpm, the control system would retrieve a fuel volume compensation value (ΔV) of 0.610 in 3 , which is readily convertible into gallon units. Preferably, the flow compensation value data set is embedded in software, firmware, etc., within the fuel meter. As shown at step  306 , the retrieved fuel volume compensation value (ΔV) is added to the volume of fuel dispensed, as measured by the fuel meter, the next time flow is initiated. The fuel meter performs the discussed sequence of steps for each nozzle snap event that occurs during each fueling operation of the fuel dispenser. 
   Referring back to  FIG. 4 , rather than being embedded in the software of each individual fuel meter, it is also possible that the discussed flow compensation value data set be embedded in software that is in the control system or that is remote from the fuel dispensers, such as the software that is contained within fuel station computer  66 . As shown, fuel station computer  66  is in communication with individual fuel dispensers  14   a ,  14   b ,  14   c  and  14   d  via communication line  67 . 
   As well, embodiments of the present invention are envisioned that include multiple flow compensation value data sets for a given fuel dispenser. An alternate embodiment of the present invention can include multiple data tables that are compiled in the manner previously discussed with regard to  FIG. 6 , with the exception that alternate data tables are compiled as a second fuel flow parameter is incrementally varied. For example, multiple tables an be created over a given range of flow rate, each table corresponding to a difference fuel temperature. As such, in addition to entering the flow compensation value table with the measured fuel flow rate at the time of the nozzle snap event, the fuel meter microprocessor, microcontroller or electronics may also select which one of the fuel volume compensation value data sets should be entered based on the second measured parameter. For example, multiple tables can be compiled for various fuel temperatures, wherein the fuel meter determines which table to enter with the measured flow rate based on the temperature of the fuel at the instant of the nozzle snap event. 
   While preferred embodiments of the invention have been shown and described, modifications and variations thereto may be practiced by those of ordinary skill in the art without departing from the spirit and scope of the present invention, which is more particularly set forth in the appended claims. In addition, it should be understood the aspects of the various embodiments may be interchanged without departing from the scope of the present invention. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention as further described in such appended claims.