Description:Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[0001] This invention is related to a method of diagnosing a fuel tank level in a vehicle and a device thereof.

Background of the invention

[0002] Fuel tank level or amount of fuel present in the tank in motor vehicles is measured with the help of a float mechanism. A potentiometer is linked with the float arm whose resistance indicates the tank level. This mechanism is usually hinged and is a part of the low-pressure fuel pump system placed inside the tank of the vehicle. Engine management system (EMS) software takes the input of Fuel Level sensor via an Analog to Digital Convertor (ADC) input . This signal is received as voltage and later a software algorithm is used to condition this signal in order to provide the status of fuel level. This is indicated on the dashboard of the vehicle as information to the vehicle user.

[0003] A US9932944 patent discloses Systems and method for an integrated fuel level and pressure sensor of a fuel tank. Methods and systems are provided for the integration of a fuel level sensor and a fuel pressure sensor in a fuel tank within a fuel system. In one example, an integrated fuel pressure and fuel level sensor for a fuel tank may include a float arm of the fuel sensor coupled to a floating body and a pressure sensor (e.g., a fuel tank pressure transducer) coupled to the floating body, the integrated fuel pressure and fuel level sensor adapted to simultaneously measure fuel level and fuel vapor pressure of the fuel tank.

Brief description of the accompanying drawings
[0004] Figure 1 illustrates a device for diagnosing a fuel tank level in a vehicle in accordance with an embodiment of the invention; and
[0005] Figure 2 illustrates a flowchart of a method of diagnosing a fuel tank level in a vehicle in accordance to the present invention.

Detailed description of the embodiments
[0006] Figure 1 illustrates a device for diagnosing a fuel tank level in a vehicle in accordance with an embodiment of the invention. The vehicle 10 comprises a sensor 18 for determining a level of fuel in the fuel tank 11. The vehicle 10 further comprises a control unit 14 adapted to control at least one operation related to the fuel tank 11. The control unit 14 is activated upon detecting an open state of a fuel cap 12 and a counter 16 of the control unit 14 is incremented based on an activation event of the control unit 14. The device 10 determines a count of the counter 16 in a next key-on event and calculates the number of activation events of the control unit. The device 10 further detects a non-functioning state of the sensor 18, when the number of activation events of the control unit 14 is more than a predefined threshold value and the diagnosis process will be reset in the control unit 14 by erasing fuel consumption values during each of the activation events of the control unit 14 , when the non-functioning state of the sensor 18 is detected.

[0007] The device 10 further comprises a memory 20 that is used to store the number of activation events of the control unit, the count of the counter 16 and the like. The control unit 14 is chosen from a group of control units like a microprocessor, a microcontroller, a digital circuit and an integrated chip. The counter 16 is used to mark the number of activation events of the control unit 14 and also a time-stamp module 22 present in the control unit 14 helps in recording the first time-stamp and the second time-stamp. A conventional gasoline fuel tank comprises two zones, one is an upper dead volume zone and a lower dead volume zone. The float is present in the upper dead volume and provides the information regarding the fuel level in the fuel tank.

[0008] The area that is referred as dead volume of the sensor 18 is a place in the fuel tank 11, where change in fuel level does not cause any change in the position of the float and subsequently no change in voltage. The upper dead volume is the volume above which the float cannot move hence no voltage change and lower dead volume is the float limit at near tank 11 empty condition. Dead volumes contribute to a significant volume of fuel. This is a physical limitation caused by the lack of extension of the float arm over this area.

[0009] In a situation where a driver tops up the tank 12 ,while the fuel level is still above the upper dead volume repeatedly, a misdetection of fuel level sensor stuck /non-functioning state of the sensor 18 by the control unit 14 will occur. This misdetection is caused because the sensor level (voltage) does not show any change over such events and the plausibility diagnosis thresholds are exceeded. This further leads to unintended alert in the dashboard or a false indication of the failure of sensor 18. As required by emission legislation standards, the device 10 is expected to detect if the sensor 18 level is plausible.

[0010] The device 10 also expect to diagnose if the sensor 18 shows no change in volume which could be due to the float arm being stuck at some point. The diagnosis is based on the comparison of the fuel level decrease with the calculated fuel consumption. If it is detected that there is huge difference between the two, a plausibility error is detected. In case sensor is really stuck in the dead volume area there is no mechanism to detect this. In order to overcome this problem, the present invention provides a solution by checking the fuel level plausibility based on the following conditions like change in fuel level is greater than or equal to predefined threshold or change in fuel consumption is greater than or equal to calibratable threshold and a difference between the fuel consumed and change in the fuel level lies within the calibratable interval.

[0011] Figure 2 illustrates a flowchart of a method of diagnosing a fuel tank level in a vehicle in accordance with the present invention. The vehicle comprises a sensor 18 for determining a level of fuel in the fuel tank 12 . The vehicle 10 further comprises a device 15 having a control unit 14 adapted to control at least one operation related to the fuel tank 11. In step S1,the control unit 14 is activated upon detecting an open state of a fuel cap 12. In step S2, a counter 16 in the control unit 14 is incremented based on an activation event of the control unit 14. In step S3, a count of the counter 16 is determined in a next key-on event and number of activation events of the control unit 14 is calculated.
[0012] In step S4, a non-functioning state of the sensor 18 is detected , when the number of activation events of the control unit 14 is more than a predefined threshold value. In step S5, the diagnosis process in the control unit 14 is reset by erasing fuel consumption values during each of the activation events of the control unit 14, when the non-functioning state of the sensor 18 is detected.

[0013] In addition to the above conditions , the control unit 14 triggers a first timestamp upon detecting the open state of the fuel cap 12 and records a second timestamp upon detecting a close state of the fuel cap 12. The control unit 14 calculates a time difference between the first timestamp and the second timestamp and is compared against a predefined threshold time-stamp value. The time difference is evaluated for determining an amount of time of the open state of the fuel -cap 12 and an occurrence of a re-filling event. The diagnosis process has been reset, by erasing fuel consumption values from a memory 20 of the control unit 14 based on the evaluated time difference.

[0014] The method is explained in detail. In a scenario, where the driver of the vehicle goes to a fuel station for re-filling, while there is fuel available above the upper dead volume of the tank 11 . A regular refueling condition is detected when user switches off the key and then opens the fuel tank cap 12. A switch (not shown) is available at the fuel tank cap 12 to detect open/close state. The status of the fuel cap 12 can be determined by the working state of the switch which is connected to the control unit 14. The device 15 detects when the driver opens the fuel cap 12 using the control unit 14 capability to wake up i.e, the control unit will be activated whenever the fuel tank cap 12 is opened.

[0015] When the user opens the fuel tank cap 12 to refuel it triggers the control unit 14 to wake up or gets activates. During the wake-up event the counter 16 is incremented. This counter 16 is written into the memory 20 of the control unit 14. On the next key-on event the counter 16 is checked against a predefined threshold value, to evaluate the number of times refueling events might have occurred. If the number of activation events is more than the predefined threshold and the control unit 14 detects the possible sensor stuck case, then the diagnosis process will be reset by erasing/ clearing the contents of the memory 20 associated with accumulating the consumed fuel over previous driving cycles.

[0016] In another scenario, the driver opens and closes the fuel tank cap 12 using the control unit’s 14 capability to get into activation state. When the user opens the fuel tank cap 12 to refuel, it triggers the control unit 14 to get into activation state. During the wake-up event a time stamp is recorded. When the user closes the fuel tank cap 12, after refueling , the control unit 14 is once again triggered. During the second wake up event another time stamp is recorded. These timestamps are stored into the memory 20 of the control unit 14. On the next key-on event, the difference in timestamps is calculated and compared against a predefined threshold time-stamp value.

[0017] The device 15 evaluates if the fuel tank cap 12 was open for a sufficiently long enough time duration to ensure refueling has actually happened. Further to this, if refueling has been detected, the device 15 resets the diagnosis process by erasing the consumed fuel level values. With the above disclosed process/method, the device 15 is capable of detecting a refuel in key off condition. This would ensure the diagnosis does not falsely detect multiple refueling conditions as a sensor 18 stuck case. It provides a low-cost effective solution.

[0018] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.
, Claims:We Claim:

1. A method of diagnosing a fuel tank (11) level in a vehicle (10), said vehicle (10) comprising a sensor (18) for determining a level of fuel in said fuel tank (11) ; a control unit (14) adapted to control at least one operation related to said fuel tank (11);
Said method comprising :
- activating said control unit (14) upon detecting an open state of a fuel cap (12) ;
- incrementing a counter (16) in said control unit (14) based on an activation event of said control unit (14);
- determining a count of said counter (16) in a next key-on event and number of activation events of said control unit (14) is calculated;
- detecting a non-functioning state of said sensor (18) when said number of activation events of said control unit (14) is more than a predefined threshold value;
- resetting said diagnosis process in said control unit (14) by erasing fuel consumption values during each of said activation events of said control unit (14), when said non-functioning state of said sensor (18) is detected.

2. The method as claimed in claim 1, wherein triggering a first time-stamp upon detecting said open state of said fuel cap (12) and recording a second time-stamp upon detecting a close state of said fuel cap (12).

3. The method as claimed in claim 2, wherein calculating a time difference between said first time-stamp and said second time-stamp and is compared against a predefined threshold time-stamp value.

4. The method as claimed in claim 3, wherein evaluating said time difference for determining an amount of time of said open state of said fuel -cap (12) and an occurrence of a re-filling event .

5. The method as claimed in claim 4, wherein resetting said diagnosis process by erasing fuel consumption values from a memory (20) of said control unit (14) based on said evaluated time difference.

6. A device (15) for diagnosing a fuel tank (11) level in a vehicle (10), said vehicle (10) comprising a sensor (18) for determining a level of fuel in said fuel tank (11) ; a control unit (14) adapted to control at least one operation related to said fuel tank (11);
said device (10) adapted to :
- activate said control unit (14) upon detecting an open state of a fuel cap (12) ;
- increment a counter (16) of said control unit (14) based on an activation event of said control unit (14);
- determine a count of said counter (16) in a next key-on event and calculate number of activation events of said control unit (14) ;
- detect a non-functioning state of said sensor (18), when said number of activation events of said control unit (14) is more than a predefined threshold value;
- resetting said diagnosis process in said control unit (14) by erasing fuel consumption values during each of said activation events of said control unit (14) , when said non-functioning state of said sensor (18) is detected.

7. The device (10) as claimed in claim 6, wherein said number of activation units of said control unit (14) and said fuel consumption values are stored in a memory (20) of said control unit (14) .
8. The device(10) as claimed in claim 6, wherein said control unit (14) detects said non-functioning state of said sensor (18) if a difference between said fuel consumed and a change in level of said fuel is more than said predefined threshold value.

9. The device (10) as claimed in claim 6, wherein said control unit (14) triggers a first time-stamp upon detecting said open state of said fuel cap (12) and records a second time-stamp upon detecting a close state of said fuel cap (12) for calculating a time-difference/an event of re-filling of said fuel.