Method for controlling a filling operation of a vehicular liquid storage system

Abstract

A method for controlling a filling operation of a vehicular liquid storage system including a tank including a fill level limiting valve. The method includes: detecting start of a first filling event; measuring a first fill level of the tank; verifying whether the measured first fill level has reached a predetermined fill level; if the verifying is positive, starting a first timer for a first amount of time; upon expiry of the first timer, closing the fill level limiting valve.

Claims

1. A method for controlling an automatic filling operation of a vehicular liquid storage system including a tank including a fill level limiting valve, the method comprising: detecting start of a first filling event; measuring a first fill level of the tank; verifying whether the measured first fill level has reached a predetermined fill level, the predetermined fill level being a maximum liquid level that can be gauged by a level gauge within the tank; when the verifying is positive, starting a timer for a first amount of time based on an estimate of an unused capacity of the tank; upon expiry of the first amount of time of the timer, closing the fill level limiting valve.

2. The method according to claim 1, further comprising: obtaining an estimate of an amount of fuel consumed between the first filling event and a previous filling event; and determining the first amount of time on the basis of the estimated amount of consumed fuel.

3. The method according to claim 1, further comprising: detecting an end of the first filling event occurring during the first amount of time; and estimating a remaining unused capacity of the tank at the end of the first filling event.

4. The method according to claim 3, further comprising: detecting start of a subsequent filling event; measuring a subsequent fill level of the tank; verifying whether the measured subsequent fill level has reached the predetermined fill level; and when the verifying is positive: obtaining an estimate of an amount of fuel consumed between the subsequent filling event and the first filling event; determining a subsequent amount of time on the basis of the estimated amount of consumed fuel, increased by an amount proportional to the estimated remaining unused capacity of the tank; starting the timer for the subsequent amount of time; and upon expiry of the subsequent amount of time of the timer, closing the fill level limiting valve.

5. The method according to claim 1, wherein the first amount of time is increased by an amount proportional to an estimate of an unused capacity of the tank at an end of a previous filling operation.

6. The method according to claim 1, further comprising: when the verifying is negative, delaying for a second amount of time; upon expiry of the second amount of time, measuring a second fill level of the tank; determining the first amount of time on the basis of the first fill level, the second fill level, and the second amount of time.

7. The method according to claim 6, wherein the verifying, the delaying, the measuring of the second fill level, and the determining of the first amount of time are carried out iteratively, and wherein a minimum value of the first amount of time as obtained over a plurality of iterations is used in the starting the timer.

8. The method according to claim 6, wherein the verifying, the delaying, the measuring of the second fill level, and the determining of the first amount of time are carried out iteratively, and wherein an average value of the first amount of time as obtained over a plurality of iterations is used in the starting the timer.

9. The method according to claim 6, further comprising: determining a reference pressure level during the second amount of time; determining an end stage pressure level upon finding that the second verifying is positive; and adjusting the determined first amount of time in function of a ratio between the end stage pressure level and the reference pressure level.

10. The method according to claim 1, wherein the vehicular liquid storage system is a fuel storage system.

11. The method according to claim 1, wherein the vehicular liquid storage system is a system for storing an aqueous urea solution.

12. A non-transitory computer readable medium comprising computer code means configured to cause a processor to carry out the method of claim 1.

13. A vehicular liquid storage system comprising: a tank including a fill level limiting valve; a level gauge; and a controller configured to obtain fill levels from the level gauge and to control the fill level limiting valve, the controller being configured to carry out the method of claim 1.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) These and other technical aspects and advantages of embodiments of the present invention will now be described in more detail with reference to the accompanying drawings, in which:

(2) FIG. 1 presents a schematic overview of a vehicular liquid storage system in which the present invention can be used;

(3) FIG. 2 provides a flow chart of an embodiment of the method according to the present invention;

(4) FIG. 3 provides a flow chart of an embodiment of the method according to the present invention; and

(5) FIG. 4 provides a flow chart of an embodiment of the method according to the present invention.

DESCRIPTION OF EMBODIMENTS

(6) FIG. 1 presents a schematic overview of a vehicular liquid storage system, preferably a fuel storage system, in a vehicle 10 in which the present invention can be used. The system comprises a tank 100, in which a level gauge 120 is arranged. Without loss of generality, a tank 100 of a very simple geometry is shown; in reality, the tank may comprise multiple compartments, as is the case for a so-called saddle tank. In that case, several level gauges would be present for the respective compartments, and the method according to the invention could be applied mutatis mutandis on the basis of the level readings from the compartments with the highest fill level.

(7) Due to the physical limitations of the level gauge 120, such a gauge is usually unable to measure the level of liquid inside the tank all the way up to the top of the tank 100. The maximum liquid level up to which the level gauge 120 is able to function correctly is designated as L.sub.max. When, during a filling operation (i.e., when liquid is added to the tank via filler pipe 110), the liquid level reaches L.sub.max, a controller 140, which receives the level signal from the level gauge 120, causes a fill level limiting valve 130 to close, which causes the filling operation to stop (generally, because a sensor in the filling nozzle detects a rise of pressure inside the tank 100 and the filler pipe 110, triggering the nozzle's shut-off mechanism). The valve 130 is generally in fluid communication with the atmosphere via a venting line, optionally via a vapor absorbing canister (not shown).

(8) FIG. 2 provides a flow chart of an embodiment of the method according to the present invention. The depicted process takes place when a refueling event is detected 210. This may consist of detecting the removal of a cap of a filler neck, the insertion of a nozzle, or a sudden rise of the general liquid level inside the tank.

(9) The fuel level L is continuously or intermittently monitored 220 in order to be able to determine 230 whether a predetermined fill level L.sub.max has been reached. L.sub.max is preferably the maximum level that can be gauged by the level gauge provided in the tank.

(10) If the valve 130 is closed upon reaching L.sub.max, a non-negligible portion of the tank (designated by the range L.sub.top) is never used.

(11) Likewise, if a filling operation is attempted when the fill level is still above L.sub.max, as may be the case when only a very small amount of fuel has been consumed after the previous complete fill-up, it would not be desirable to keep the valve 130 closed, because it would prevent the unused portion of the tank to be filled.

(12) It is an object of embodiments of the present invention, to increase the useful volume of the tank by allowing an amount of liquid to be added to the tank after reaching L.sub.max. Ideally, the entire gap L.sub.top should be allowed to be used.

(13) To this end, when it is detected 230 that the point L=L.sub.max is reached, a timer y is started 240. The timer allows the valve to remain open for an additional amount of time t.sub.max. When the timer expires 250, the valve is closed 260, and the refueling sequence is ended. As the valve is closed 260, a sensor in the filling nozzle detects a rise of pressure inside the tank and the filler pipe, triggering the nozzle's shut-off mechanism. This takes the assumption that the operator allows the pistol to fuel at a constant flow rate i.e. using the predefined latching mechanism on the nozzle until the refueling is complete. As the pressure settles down, the nozzle may allow a brief additional filling (topping off), until a new pressure peak re-triggers the shut-off mechanism.

(14) In this embodiment, t.sub.max is a fixed, predetermined amount of time, which is determined in advance in function of the geometry of the tank and the expected maximum filling rate so as to give the filling process enough extra time to fill the volume represented by L.sub.top. To be on the safe side, the time t.sub.max to be used in practice is preferably slightly less than the time needed to completely fill the tank at the maximum filling flow. Preferably, t.sub.max is a function of an estimate of an unused capacity of the tank (e.g. capacity that was not used due to an incomplete filling in a previous filling operation, or unused capacity that cannot be detected by the level gauge because a small amount of fuel has been consumed since a previous complete filling).

(15) FIG. 3 provides a flow chart of another embodiment of the method according to the present invention. The depicted process takes place when a refueling event is detected 310, as described above in the context of FIG. 2. An initial fuel level L.sub.0 is determined 320 in order to be able to determine 330 whether a predetermined fill level L.sub.max has been reached. L.sub.max is preferably the maximum level that can be gauged by the level gauge provided in the tank.

(16) When it is detected 330 that the point L=L.sub.max is reached, a timer y is started 340. The timer allows the valve to remain open for an additional amount of time t.sub.max. When the timer expires 350, the valve is closed 360, and the refueling sequence is ended. As the valve is closed 360, a sensor in the filling nozzle detects a rise of pressure inside the tank and the filler pipe, triggering the nozzle's shut-off mechanism. As the pressure settles down, the nozzle may allow a brief additional filling (topping off), until a new pressure peak re-triggers the shut-off mechanism.

(17) In this embodiment, t.sub.max is determined on the fly, for the filling operation in question. This is achieved by measuring the amount of liquid added to the tank in a fixed time interval T. Thus, upon determining L.sub.0L.sub.max 330, a delay of time x is allowed to pass 331, before a new level measurement L.sub.1 is carried out 332. The estimated instantaneous filling rate R.sub.x can then be determined 333 by calculating R.sub.x=(L.sub.1L.sub.0)/T.

(18) In the illustrated case, if the instantaneous filling rate R.sub.x determined in the specific iteration is greater than the previous highest recorded filling rate R.sub.max 334, R.sub.max is updated 335 to R.sub.x. Alternatively (not illustrated), the consecutive measurements R.sub.x may be used to update a running average filling rate R.sub.avg.

(19) The highest recorded filling rate R.sub.max or the average filling rate R.sub.avg is used (along with known information about the geometry of the tank) to calculate 336 the maximum allowable additional filling time t.sub.max. To be on the safe side, the time t.sub.max to be used in practice is preferably slightly less than the time needed to completely fill the tank at the maximum filling flow.

(20) Where reference is made to the highest recorded filling rate R.sub.max, it could be stated in an equivalent way that the smallest calculated value of t.sub.max over the iterations is used. While the calculation of R.sub.max and t.sub.max is described as two distinct steps, the actual calculations may skip the output of R.sub.max as a separately intermediate result.

(21) The present invention also pertains to a vehicular liquid storage system (see also FIG. 1) comprising a controller 130 configured to carry out the methods described above. The controller 130 may be implemented in dedicated hardware (e.g., ASIC), configurable hardware (e.g., FPGA), programmable components (e.g., a DSP or general purpose processor with appropriate software), or any combination thereof. The same component(s) may also include other functions.

(22) The vehicular liquid storage system may further comprise a pressure sensor (not illustrated). The estimation of the constant flow can be derived from the evolution of the fuel level sensor reading combined with an evaluation of the internal tank pressure. If, during the last portion of the refueling operation, the pressure level is similar (within a given tolerance) to the pressure level during the stabilized refueling flow, the flow can be considered constant. If, during the last portion of the refueling operation, the pressure level is not within a given tolerance to the pressure level during the stabilized refueling flow, the flow cannot be considered constant. The pressure level is then an indication of the flow rate and by interpolation the required additional refueling time can be calculated.

(23) Furthermore if it is deemed during the first reading 330 that L is already at or above L.sub.max, it must be concluded that the tank was already (nearly) full on arrival, and the refueling will merely serve to top up the tank for the relatively small quantity of fuel that was consumed since the last filling operation. To correctly account for such situations, a boolean variable FOA is set prior to the first reading 330, and cleared only if the first reading 330 indicates a fuel level below L.sub.max.

(24) Accordingly, when the fuel level verification 330 is indicative of a nearly full tank (the YES branch of the selection 330 is taken), the system verifies 371 whether FOA is set, in which case an estimation of the fuel consumption between refueling instances 372 is used to define T.sub.max 373. This step ensures a proper refueling in the case that the operator used only a small amount of fuel during a drive event, and then refueled again. Without this estimation, the T.sub.max previously stored would produce an over-fill condition. If the verification 371 reveals that FOA is not set, the process proceeds as described abovethe fact that FOA is not set at this point implies that it was cleared upon the initial verification of the fuel level 330, which in turn implies that the tank was not nearly full on arrival.

(25) As a means to provide further accuracy, the steps 381-387 may be used to estimate the amount of fuel in the tank in the event that the operator stops the refueling process prematurely during the time interval T.sub.max. To this end, pressure is measured in the tank and if it deemed it has fallen below a level indicative of fuel flowing into the tank 381 then the time at which this pressure level drops is stored 382 and compared to the previously determined T.sub.max 383. The new T value is then multiplied by the flow rate R.sub.x 384 to calculate the amount of under-fill that occurred and this value is stored as a base consumption level 385 to add to the consumption of fuel during the next refueling interval 386. The refueling operation is finally terminated by closing the valve 387.

(26) FIG. 4 provides a flow chart of the steps that may be performed in embodiments of the present invention in order to implement the flow rate estimation described above. The sequence starts with the detection 410 of a refueling event, in a manner analogous to the corresponding step 310 of FIG. 3. An initial fuel level L.sub.0 is determined 420 in order to be able to determine 430 whether a predetermined fill level L.sub.max has been reached. L.sub.max is preferably the maximum level that can be gauged by the level gauge provided in the tank. Also at the start of the refueling vent, the initial pressure P.sub.0 is captured 421.

(27) When it is detected 430 that the point L=L.sub.max is reached, a timer y is started 450. The timer allows the valve to remain open for an additional amount of time t.sub.max. When the timer expires 454, the valve is closed 455, and the refueling sequence is ended. As the valve is closed 455, a sensor in the filling nozzle detects a rise of pressure inside the tank and the filler pipe, triggering the nozzle's shut-off mechanism. As the pressure settles down, the nozzle may allow a brief additional filling (topping off), until a new pressure peak re-triggers the shut-off mechanism.

(28) A difference with the embodiment illustrated in FIG. 3, is that the end stage pressure value is captured 451 upon starting timer y 450. If this end stage pressure is equal to p.sub.max, which has been determined during the first part of the refueling operation (i.e., before reaching L.sub.max), as will be described below, the fuel flow rate is assumed to be substantially equal to the flow rate that was present when the value of t.sub.max was determined, and the timer is allowed to run out as described above. If the captured pressure is not equal to p.sub.max, the time t.sub.max for which the timer y is allowed to run is adjusted accordingly, because the changed pressure condition is indicative of a change in flow rate, which will cause the tank to fill up more slowly or more speedily than originally assumed. In a particular embodiment, the topping-up time is scaled up or down by a factor p/p.sub.max, which is a first order approximation of the instantaneous fuel flow rate, because a higher flow rate will lead to a greater pressure build-up in the tank.

(29) In this embodiment, as before, t.sub.max is determined on the fly, for the filling operation in question. This is achieved by measuring the amount of liquid added to the tank in a fixed time interval T. Thus, upon determining L.sub.0L.sub.max 430, a delay of time x is allowed to pass 431, before a new level measurement L.sub.1 is carried out 432. The estimated instantaneous filling rate R.sub.x can then be determined 435 by calculating R.sub.x=(L.sub.1L.sub.0)/T. At the same stage, a new pressure measurement p.sub.1 is carried out 433, and the average pressure for the present refueling operation is updated 434 by calculating p.sub.avg=(p.sub.1+p.sub.0)/2.

(30) In the illustrated case, if the instantaneous filling rate R.sub.x determined in the specific iteration is greater than the previous highest recorded filling rate R.sub.max 436, R.sub.max is updated 439 to R.sub.x. Alternatively (not illustrated), the consecutive measurements R.sub.x may be used to update a running average filling rate R.sub.avg.

(31) At the same stage, if the updated average pressure value p.sub.avg determined in the specific iteration is greater than the previous highest recorded average pressure p.sub.max 437, p.sub.max is updated 438 to p.sub.avg.

(32) The highest recorded filling rate R.sub.max or the average filling rate R.sub.avg is used (along with known information about the geometry of the tank) to calculate 440 the maximum allowable additional filling time t.sub.max. To be on the safe side, the time t.sub.max to be used in practice is preferably slightly less than the time needed to completely fill the tank at the maximum filling flow.

(33) Where reference is made to the highest recorded filling rate R.sub.max, it could be stated in an equivalent way that the smallest calculated value of t.sub.max over the iterations is used. While the calculation of R.sub.max and t.sub.max is described as two distinct steps, the actual calculations may skip the output of R.sub.max as a separately intermediate result.

(34) As already described in the context of FIG. 3, if it is deemed during the first reading 430 that L is already at or above L.sub.max, it must be concluded that the tank was already (nearly) full on arrival, and the refueling will merely serve to top up the tank for the relatively small quantity of fuel that was consumed since the last filling operation. To correctly account for such situations, a boolean variable FOA is set prior to the first reading 430, and cleared only if the first reading 430 indicates a fuel level below L.sub.max.

(35) Accordingly, when the fuel level verification 430 is indicative of a nearly full tank (the YES branch of the selection 430 is taken), the system verifies 461 whether FOA is set, in which case an estimation of the fuel consumption between refueling instances 462 is used to define T.sub.max 463. This step ensures a proper refueling in the case that the operator used only a small amount of fuel during a drive event, and then refueled again. Without this estimation, the T.sub.max previously stored would produce an over-fill condition. If the verification 461 reveals that FOA is not set, the process proceeds as described abovethe fact that FOA is not set at this point implies that it was cleared upon the initial verification of the fuel level 430, which in turn implies that the tank was not nearly full on arrival.

(36) As a means to provide further accuracy, the steps 470-476 may be used to estimate the amount of fuel in the tank in the event that the operator stops the refueling process prematurely during the time interval T.sub.max. To this end, pressure is measured in the tank and if it deemed it has fallen below a level indicative of fuel flowing into the tank 470 then the time at which this pressure level drops is stored 471 and compared to the previously determined T.sub.max 472. The new T value is then multiplied by the flow rate R.sub.x 473 to calculate the amount of under-fill that occurred and this value is stored as a base consumption level 474 to add to the consumption of fuel 475 during the next refueling interval. The refueling operation is finally terminated by closing the valve 476.

(37) The present invention also pertains to a computer program product configured to cause a controller of a vehicular liquid storage system to carry out the methods described above.

(38) The implementation of the present invention in software allows a refueling operation that can be calibrated by software, with the possibility of filling the tank above the maximum readable level of a level sensor. The result is a huge decrease in development time as well as commoditization of components as the venting system only needs to provide venting of the vapor space in the tank and rollover protection. This means that it can be designed to have a shutoff height as close to the top of the tank as possible.

(39) While the invention has been described hereinabove with reference to specific embodiments, this was done to clarify and not to limit the invention. The skilled person will appreciate that various modifications and different combinations of disclosed features are possible without departing from the scope of the invention.