Abstract:
A fuel sensing system and method of measuring and monitoring an amount of fuel in a storage tank for power operated equipment. The method comprises the steps of positioning a fuel sensor assembly within a storage tank that supports fuel provided to the power operated equipment during operation and generating a pulse width modulated output signal with a pulse width modulation generating circuit. The pulse width modulated output signal provides a signal width proportional to the fuel level in the storage tank. The method also comprises processing the pulse with modulated output signal with non-transient computer readable medium by one or more processors internal to a microcontroller to form an output value indicating the amount of fuel in the storage tank and displaying the output value on an indicator display mounted on the power equipment.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    The following application is a Nonprovisional patent application that claims priority to co-pending U.S. Provisional Patent Application Ser. No. 61/707,149 filed Sep. 28, 2012 entitled FUEL SENSING SYSTEM AND METHOD OF OPERATION. The above-identified application is incorporated herein by reference in its entirety for all purposes. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to a fuel sensing system and method of operation, and more particularly, a fuel sensing system and process for monitoring fuel levels in outdoor power equipment. 
       BACKGROUND 
       [0003]    Fuel sensors coupled to indicator displays or fuel gauges are frequently used in outdoor power equipment. Outdoor power equipment includes, but is not limited to, riding lawn mowers, lawn and agricultural tractors, snowmobiles, snowblowers, jet skis, boats, all terrain vehicles, bulldozers, generators, and the like. Fuel sensors indicate to the operator of the power equipment how much fuel remains in the fuel supply or tank. 
         [0004]    The fuel sensors indicator displays in a riding mower or tractor is frequently mounted to the dash panel, typically in view with the operator while operating the lawn mower. Further discussion relating to developments in indicator displays are discussed in U.S. Pat. No. 7,777,639 that issued on Aug. 17, 2010. The &#39;639 patent is owned by the assignee of the present application and is incorporated herein by reference in their entirety. 
       SUMMARY 
       [0005]    One example embodiment of the present disclosure includes a fuel sensing system and method of measuring and monitoring an amount of fuel in a storage tank for power operated equipment. The method comprises the steps of positioning a fuel sensor assembly within a storage tank that supports fuel provided to the power operated equipment during operation and generating a pulse width modulated output signal with a pulse width modulation generating circuit. The pulse width modulated output signal provides a signal width proportional to the fuel level in the storage tank. The method also comprises processing the pulse with modulated output signal with non-transient computer readable medium by one or more processors internal to a microcontroller to form an output value indicating the amount of fuel in the storage tank and displaying the output value on an indicator display mounted on the power equipment. 
         [0006]    Another example embodiment of the present disclosure includes a system measuring and monitoring an amount of fuel in a storage tank for power operated equipment comprising a control circuit having a non-transitory computer readable medium storing machine executable instructions executable by a processor coupled to and in communication with the control circuit for reading and processing a pulse width modulated signal to form a non-transitory output value indicating the amount of fuel in a storage tank. The system further comprises a display for displaying the non-transitory output value for viewing by a user of the system. 
         [0007]    While another example embodiment of the present disclosure includes an apparatus for measuring and monitoring an amount of fuel in a storage tank comprising a fuel sensor assembly to be positioned during use within a storage tank that supports fuel provided to power operated equipment during operation, the fuel sensor assembly having a pulse width modulation circuit for generating a pulse width modulated signal wherein the pulse width modulated signal has a signal width proportional to the fuel level in a storage tank and a control circuit remotely located from fuel sensor assembly, the control circuit having a non-transitory computer readable medium storing machine executable instructions executable by a processor coupled to and in communication with said control circuit for reading said pulse width modulated signal to form a non-transitory output value indicating the amount of fuel in a storage tank. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The foregoing and other features and advantages of the present disclosure will become apparent to one skilled in the art to which the present invention relates upon consideration of the following description of the invention with reference to the accompanying drawings, wherein like reference numerals refer to like parts unless described otherwise throughout the drawings and in which: 
           [0009]      FIG. 1  illustrates one form of power equipment using a fuel sensing system in accordance with one example embodiment of the present disclosure; 
           [0010]      FIG. 2  illustrates a fuel sensing gauge used with the fuel sensing system in accordance with one example embodiment of the present disclosure; 
           [0011]      FIG. 3  illustrates a fuel sensor assembly constructed in accordance with one example embodiment of the present disclosure; 
           [0012]      FIG. 4  illustrates a signal profile analyzed in a fuel sensing system in accordance with one example embodiment of the present disclosure; 
           [0013]      FIG. 5  is a first portion of an electrical schematic of a fuel sensing system in accordance with one example embodiment of the present disclosure; 
           [0014]      FIG. 6  is a second portion of the electrical schematic of  FIG. 5 ; 
           [0015]      FIG. 7  is a block diagram illustrating the operation of a fuel sensing system in accordance with one example embodiment of the present disclosure; and 
           [0016]      FIG. 8  is a block diagram illustrating the operation of an anti-slosh process of a fuel sensing system in accordance with one example embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Referring now to the figures generally wherein like numbered features shown therein refer to like elements throughout unless otherwise noted. The present disclosure relates to a fuel sensing system and method of operation, and more particularly, a fuel sensing system and process for monitoring fuel level in outdoor power equipment with heightened accuracy. 
         [0018]      FIG. 1  illustrates power equipment  10  in the form of a riding mower. The power equipment  10  employs a fuel sensing system  12  constructed in accordance with one example embodiment of the present disclosure. It should be appreciated by those skilled in the art, that the power equipment  10  in addition to being a riding mower, could also be lawn and agricultural tractors, snowmobiles, snowblowers, jet skis, boats, all terrain vehicles, bulldozers, generators, and the like without departing from the spirit and scope of the present disclosure. 
         [0019]    As stated above, the power equipment  10  uses a fuel sensing system  12  that comprises an indicator display  20 , located typically on the dash  14  of the riding mower as illustrated in  FIG. 1 . The fuel sensing system  12  further comprises a control circuit  16  (see  FIGS. 5 and 6 ), and fuel sensor assembly  18  (see  FIG. 3 ). The fuel sensor assembly IS8 is in communication with the control circuit  16  either directly by hard wire  22  or by wireless communication  24  such as Wi-Fi, Bluetooth, or other known over-the-air protocols. 
         [0020]    As illustrated in  FIG. 1 , the fuel sensor assembly  18  is located in a fuel tank  26  that stores liquid fuel such as gasoline or diesel for powering an internal combustion engine  28  of the power equipment  10 . The fuel sensor assembly  18  is further shown in more detail in  FIG. 3 , and comprises a sensor  30  having a body  32  and a cylindrical stem portion  34  that is partially surrounded by a float  38 . Internal to the stem portion  34  is a detector  36  that includes a magnetic relationship with the float  38 . That is, either the detector  36  or float  38  includes a magnetic component that communicates a level sensing signal  42  to the control circuit  16  that can be located in the body  32  or as in the illustrated example embodiment, on the indicator display  20 , or both. 
         [0021]    The float  38  moves up and down the stem  34  in the directions of arrows A as the level of the fuel (F) moves up and down in the tank  26 , indicated by arrows B. As the float  38  moves up and down the stem  34 , supply power  40  from, for example, a battery passing through a voltage regulator (not shown) provides a direct current DC signal  42 A, in which the signal&#39;s magnitude is altered magnetically based on the location of the float corresponding to the fuel level within the tank. Thus, the magnitude of the DC signal  42 A is proportional to the level of the fuel in the tank  26  of the power equipment  10 . 
         [0022]    While  FIG. 3  illustrates a single fuel sensor assembly  18 , it should be appreciated by those skilled in the art that any number of fuel sensor assemblies could be used in the fuel sensing system  12 . In fact, the control circuit  16  in the illustrated example embodiments of  FIGS. 5 and 6  is constructed to receive and supply power to two separate fuel sensor assemblies  18 , for left and right tanks as indicated in the display  20  of  FIG. 2 . 
         [0023]    Unlike conventional fuel sensors that use an analog signal from a rotary potentiometer to generate a signal as an indication the fuel level in the tank, the fuel sensor assembly  18  includes a pulse width modulator circuit  44 . The PWM circuit  44 , in one example embodiment includes a PWM signal generator constructed from an analog circuit, a digital circuit, a discrete integrated circuit IC, microcontroller, or any combination thereof as would be appreciated by those skilled in the art. 
         [0024]    The PWM circuit  44  alters the DC signal  42 A to a PWM signal  42 B shown in  FIG. 4 . The PWM signal  42 B forming the sensing signal  42 , which because the signal is pulse width modulated, has superior noise immunity over conventional analog signals. Thus, noise generated by the power equipment  10  is minimized, increasing the accuracy of the fuel sensing system  12 . For example, a conventional analog signal used in interfacing a fuel sensor to a fuel gauge uses an analog signal that may vary from 0.5 VDC to 4.5 VDC. When the sensor signal is 0.5 VDC, this indicates that the tank fuel level is out empty. When the sensor signal is 4.5 VDC, this indicates that fuel tank is full. A typical method of reading this conventional DC signal is via a microcontroller with an A/D converter. The A/D converter would typically be an 8-bit converter and as such, possess a resolution of 5V/256 counts, which equals 0.0195V/count. Therefore, an 8-bit A/D converter in the microcontroller requires only 0.0195V of signal change before it changes the output value. 
         [0025]    If noise or wiring in the power equipment  10  induces in this conventional system 0.0195V of signal onto an existing half full tank signal of 2.5 VDC, a new signal of 2.5195V is received. This error by the count amount of 0.0195V represents a different and inaccurate fuel level to the sensing and display system of the power equipment. 
         [0026]    Advantageously, the PWM signal  42 B of the present disclosure generated by PWM circuit  44  as part of the fuel sensor assembly  18  and shown in  FIG. 4  provides a more accurate signal representative of fuel levels as it is communicated to the control circuit  16 . In the illustrated example PWM signals  42 B embodiments of  FIG. 4 , the PWM signal  42 B employs the varying low pulse width from 0.1 mS low for empty to 0.9 mS low for a full tank. In order for noise to affect this 5V PWM signal, it must be approximately 5V in amplitude, or 5V/0.0195V, which equals 256 times larger amplitude noise than what would erroneously influence a conventional analog signal. Advantageously, the PWM signal  42 B allows for increased distances between the fuel sensor assembly  18  and the control circuit  16  because of the reduced influence of noise on the fuel level being measured. 
         [0027]    Referring now to  FIGS. 5 and 6  are schematics forming the control circuit  16  constructed in accordance with one example embodiment of the present disclosure. The control circuit  16  receives and processes the PWM signal  42 B communicated via wiring harness or over-the-air from the PWM generator circuit  44 . 
         [0028]    Input power to the control circuit  16  is supplied by connector pin  46  and ground by connector pin  48 . Capacitor  50  filters power from any noise or transients exposed to the circuit  16 . The control circuit  16  employs a rectifier  52  that provides reverse polarity protection for the incoming power supply. In one example embodiment, the power supply is a 12V DC battery. 
         [0029]    The control circuit  16  further comprises a voltage regulator circuit  54  consisting of resistors  54 A and  54 B, transistor  54 C, zener diode  54 D and capacitor  54 E. The voltage regulator circuit  54  provides power to integrated circuits  56 ,  58 . Resistor  54 A is a current limiting resistor that protects transistor  54 C in case of a short to ground occurs. Resistor  54 B supplies zener current to zener diode  54 D. The zener diode  54 D supplies 5.6V to transistor  54 C. In the voltage regulator circuit  54 , the emitter lead of transistor  54 C is regulated at approximately 5 VDC. A capacitor  54 E acts as an output filter for 5V load transients. 
         [0030]    An additional voltage regulator circuit  62  consists of resistors  62 A and  62 B, transistor  62 C, zener diode  62 D, and capacitor  62 E. The voltage regulator circuit  62  provides power to two remote fuel sensor assemblies  18 . Resistor  62 A is a current limiting resistor that protects transistor  62 C in case of a short to ground occurs. Resistor  62 B supplies zener current to zener diode  62 D. The zener diode  62 D supplies 6.2V to the transistor  62 C. In the voltage regulator circuit  62 , the emitter lead of transistor  62 C is regulated at approximately 5 VDC. The capacitor  62 E acts as an output filter for 5V load transients of the fuel sensor assemblies  18 . 
         [0031]    A diode  66  provides reverse polarity protection for the output 5 VDC at connector  68 . A capacitor  70  provides a high frequency filter for output  68 . 
         [0032]    The fuel sensor assembly  18  and particularly the PWM circuit  44 , for a left “L” and right “R” fuel tank receive their respective supply power from output  68  as illustrated in the example embodiment of  FIG. 2 . Of course, it should be appreciated that one or more fuel tanks  26  or divisions within a single tank requiring one or more fuel sensor assemblies  18  is intended to be within the scope of the claims of the present disclosure. 
         [0033]    The PWM signal  42 B of  FIG. 4  from each fuel sensor assembly  18  is communicated from respective fuel sensor assembly to input  72 A for the right fuel tank and input  72 B for the left fuel tank. As illustrated in the example embodiment of  FIG. 4 , the width of the pulse from the fuel tank sensor assembly  18  is proportional to the level of the fuel in the tank. In the illustrated example embodiment, the empty tank signal is low for 0.1 mS and high for 0.9 mS as illustrated in  FIG. 4 . A full tank signal in  FIG. 4  is low for 0.9 mS and high for 0.1 mS. 
         [0034]    A low-pass filter is formed with resistor  74  and capacitor  76  for the PWM signal  42 B. Diode  78  provides a clamp to 5 VDC for the PWM signal  42 B. Diode  80  provides a clamp to ground for the PWM signal  42 B. Resistor  82  is a pull-up resister for the PWM generator  44  and provides current to an internal output transistor of the generator. A Schmitt trigger inverter  84  reduces the noise influence on the measurement of the PWM  42 B signal at pins  1  and  2  in the right fuel tank circuit at pins  3  and  4  in the left fuel tank. Capacitor  86  is a noise decoupling capacitor for the Schmitt trigger inverter  84 A. Output pin  2  of Schmitt trigger  84 A is the input into microcontroller  56  at pin  22  for measurement and averaging of the PWM signal  42 B. Output pin  3  of the Schmitt trigger  84 B is the input to the microcontroller  56  at pin  23  for measurement and averaging of the PWM signal  42 B. 
         [0035]    In the illustrated example embodiment, microcontroller  56  is a PIC chip. In particular, the PIC chip is identified under part number 16F1933T, which the specification data sheet is incorporated herein by reference. The microcontroller  56  measures the pulse width and period of the pulse width modulated signal  42 B at input pins  22  and  23  for respective left L and right R tanks having respective fuel sensor assemblies  18 . The measurement by the microcontroller  56  of the PWM signal  42 B of both the width and period are then translated to percent duty cycle via a formula represented by percentage duty cycle is equal to the pulse width divided by the period. The percentage duty cycle that is then translated for display by illuminating the corresponding bars of the LCD in the gage  20  for respective tanks as illustrated in  FIG. 2 . 
         [0036]    The microcontroller  56  includes one or more processors, such as one or more microprocessors, digital signal processors (DSPs), combinations thereof or such other devices known to those having ordinary skill in the art. Each processor is coupled to an at least one memory device (also referred to herein as “a memory”), such as random access memory (RAM), dynamic random access memory (DRAM), and/or read only memory (ROM) or equivalents thereof, that maintains data and programs/instructions that may be executed by the one or more processors. Unless otherwise specified herein, all functions described as being performed herein by the microcontroller  56  is performed by their respective one or more processors, which are configured to perform such functionality based on the data and programs/instructions maintained in the corresponding memory. 
         [0037]    Illustrated in  FIG. 7  is a block diagram illustrating an operation  100  of a fuel sensing system  12  in accordance with one example embodiment of the present disclosure. The operation  100  is initiated at  110 , typically by the actuation of the power equipment motor or starter by engaging, for example a push button or turning of a key in an ignition. At  112 , the operation  100  is powered up by a power supply such as a 12 VDC battery. At  114  and  116 , right and left tank sensors are read by microcontroller  56 . It should be appreciated that only one or multiple fuel sensor assemblies  18  can be used in multiple or single fuel tanks  26 . At  118 , a sloshing algorithm is executed by processors internal to microcontroller  56 . The sloshing algorithm  118  uses the PWM signal  42 B as an input from which an output  120  is calculated relating to the level of fuel in the tank. At  122 , a display provided for example in LCD of gage  20  as to the fuel levels in the tank or tanks. At  124 , the operation  100  is repeated after power up so that the fuel levels are monitored continuously during operation of the power equipment  10 . 
         [0038]    Illustrated in  FIG. 8  is a block diagram illustrating the operation  200  of an anti-slosh process for a fuel sensing system  12  in accordance with one example embodiment of the present disclosure. The operation  200  in one example embodiment is in the form of software or firmware having executable non-transient readable media instructions executed by the processors located within microcontroller  56 . 
         [0039]    The main loop of the operation  200  shown in  FIG. 8  identifies three blocks of execution, namely executed operations  210 ,  212 , and  214 . The operation  200 , and specifically operations  210 ,  212 ,  214  and interrupts  218 ,  220 , and  222  in one example embodiment continuously ping and/or analyze PWM signal  42 B during the loop  124  of the fuel sensing operation of  FIG. 7 . 
         [0040]    At  210 , a master timer used to count time and/or store time associated with the PWM signal  42 B in EEPROM and RAM. At  212 , the time from the PWM signal  42  is decoded, by for example an A/D converter internal to the microcontroller  56  stored in RAM. 
         [0041]    At  214 , the microcontroller  56  reads eight (8) separate signals from the PWM generator from the fuel sensor assemblies  18 . Each reading is collected by the microcontroller  56  at an average rate of 1 reading or PWM  42 B signal every 18 seconds. These eight (8) readings are then averaged by processors internal to the microcontroller  56  to create a final value  230 A/ 230 B, relating to fuel level for each fuel sensor assembly  18  for display on the liquid crystal display (LCD) as shown in  FIG. 2  on gage  20 . At  216 , a loop continues by returning to the operation  200  at  210 . 
         [0042]    The fuel tank  26  level readings used by the main loop  210 - 216  are generated by two separate interrupt routines,  218  and  220 . Each interrupt routine waits for the sensor  18  value to go high in the PWM signal  42 B, and then processors within the microcontroller  56  measure the amount of time it is high for the width measurement. Then the interrupts  218  and  220  wait until the sensor  18  value of the PWM signal  42 B goes high again to generate the period measurement. With these two measurements, relating to time and period, the operation  200  computes the pulse width value based on the following formula PWM value=pulse width/pulse period written as instructions from software or firmware forming the operation  200  internal to the microcontroller  56 . 
         [0043]    This operation  200  also indicates to the operator that a fuel sensor assembly  18  is not connected by detecting the loss of the PWM signal  42 B. Upon loss of signal  42 B, blinking occurs in corresponding left or right tank bars. This is useful for troubleshooting and for the operator to ensure the system is working properly. 
         [0044]    When the fuel gauge  20  powers up, a power up routine, which measures each fuel tank eight (8) times to fill up the running average buffer, as indicated by the timing interrupt  222 . The timing interrupt permits the operator to fill up the tank and not have to wait for 8×18 seconds, or 144 seconds before indicating the value of the fuel level. 
         [0045]    What have been described above are examples of the present disclosure. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present disclosure, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present disclosure are possible. Accordingly, the present disclosure is intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims.