EP1506937B1 - Method for controlling the vapour recovery system of a filling station - Google Patents

Abstract

Method for corrective controlling of a gas return system in a petrol station in which during a filling process, a fuel volume flow signal (13), a gas volume flow signal (14) and optional other signal are transmitted to a control unit (15). The control unit calculates a corrective control signal to use in the next filling process based on the measurement signals. The invention also relates to a corresponding device for implementing the inventive method.

Description

The invention relates to a method for the corrective control of a gas recirculation system at a gas station.

When fueling a motor vehicle at a gas station is filled with the help of a dispensing valve from the pump fuel into the tank of the motor vehicle. At the same time, the gas mixture, which is located above the liquid level of the fuel in the tank of the motor vehicle, is sucked off via a separate line and returned to the fuel storage tank. The vapor recovery system used for this purpose must be controlled so that the volume of gas mixture extracted per unit time is equal to the volume of fuel charged per unit time into the tank of the motor vehicle.

According to the prior art, a calibration procedure is carried out for this, in which air is pumped through the gas recirculation system as reference gas. A gas flow meter is connected to the gas inlet opening of the dispensing valve and a control parameter is determined such that the recirculated gas volume corresponds to the assumed fuel volume. This control parameter is determined for various assumed fuel flows, and the resulting calibration data is stored in the operating electronics of the vapor recovery system. In tank operation, the delivery rate of the vapor recovery system is set using the calibration data.

Changes in the gas recirculation system, eg due to aging, can cause significant deviations of the gas volume flow from the fuel volume flow, which leads to an increased environmental impact. These deviations were in the past in the Usually discovered only at the annual routine checks. As a result, automatic monitoring devices are already mandated or will be forthcoming in several countries. Such automatic monitoring devices measure the gas volume flow during each refueling process and compare this with the fuel volume flow. In the event of a deviation beyond the respectively prescribed limits, an alarm signal is generated. Such monitoring devices are described, for example in DE 100 31 813 A1 . DE 100 35 645 A1 . EP 1 077 197 A1 such as WO 98/31628 , In the described configuration, the vapor recovery system and the automatic monitoring device operate independently of each other.

Since degradation occurs, in which the gas recirculation rate changes only moderately and slowly, but nevertheless the previously defined limits are exceeded, the measured value of the gas recirculation rate for correcting the gas recirculation system is utilized in further developed systems. Such devices are in WO 96/06038 . DE 295 21 160 A1 and DE 199 18 926 A1 described.

In WO 96/06038 and DE 295 21 160 A1 a scheme is presented, but has the disadvantage that the gas flow meter and the control system must have short time constants to ensure timely control.

This disadvantage is removed by the device according to DE 199 18 926 A1 , Here, after each refueling operation, a new set of calibration data is calculated from the gas flow rate readings, which is then stored and used in the vapor recirculation system. In the respective subsequent refueling process, a new calibration data record is then available which compensates for any deviation of the gas recirculation rate from the setpoint rate of 100%. However, the comparison with the fuel flow rate is still carried out independently by this gas recirculation system; the gas volume flow meter is practically only for selecting the appropriate calibration data. The disadvantage of this in the DE 199 18 926 A1 The solution described is that only a small portion of the installed vapor recirculation systems is set up to allow a constant reloading of the changed calibration data. There are several manufacturer-specific calibration data formats that are not disclosed.

It is an object of the present invention to provide a reliable method of controlling a gas recirculation system at a gas station that can be accomplished by inexpensively retrofitting existing equipment without requiring manufacturer-specific changes to existing gas recirculation systems.

This object is achieved by a method for the corrective control of a gas recirculation system at a gas station with the features of claim 1. Advantageous embodiments of the invention will become apparent from the other claims.

In the method according to the invention, in a fueling operation by means of the fuel volume flow signal and the gas volumetric flow signal generated via the existing gas volumetric flow meter and optionally further signals in a control device, a corrective control signal to be used for the next refueling operation is generated, with which the gas recirculation system for controlling the gas recirculation system Gas volume flow is controlled. Unlike in the prior art ( DE 199 18 926 A1 ) the gas volumetric flow meter is therefore not used to select a suitable set of calibration data (relationship between gas volumetric flow as a function of directly measured fuel volumetric flow), via which the gas pump is then driven, but the gas volumetric flow signal is used directly, almost like in a regulation. Control fluctuations, as in the prior art according to WO 96/06038 and DE 295 21 160 A1 can be avoided, however, since the generated corrective Control signal is applied until the next refueling process. The method is therefore a control, but a corrective control.

If the corrective control signal to be used for the next refueling operation is calculated by averaging deviation signals in several refueling operations, particularly stable conditions result and short-term fluctuations can not cause problems.

The method according to the invention is well suited for inexpensively retrofitting existing gas recirculation systems. Depending on the existing circumstances, in a retrofit kit, e.g. the control device or replacement parts for an existing control device (plug-in cards, program modules) or a gas flow meter may be included.

Figur 1

eine schematische Ansicht eines Gasrückführungssystems an einer Tankstelle mit den zum Ausführen des erfindungsgemäßen Verfahrens verwendeten Komponenten.

In the following the invention will be further explained by means of embodiments. The drawing shows in

FIG. 1

a schematic view of a gas recirculation system at a gas station with the components used to carry out the method according to the invention.

In a refueling system, as known from the prior art, fuel from a fuel storage tank 1 through a line 2 by means of a fuel pump 3 by a fuel flow meter 4, a nozzle 5 and a nozzle 6 promoted until it exits through an opening 7 and in the storage tank of the vehicle to be refueled (not shown) is running. The gas mixture above the fuel in the tank to be filled is displaced by the fuel from the storage tank and sucked in via a suction opening 8 of the dispensing valve 6. The strength of the gas volume flow is determined by the flow rate of the gas pump 10 used. This flow rate is set, for example, via the speed of the electric Drive motor 12 of the gas pump 10. The gas mixture flows through a line within the dispensing hose 5 via a return line 11 into the fuel storage tank 1 back. It is also customary to adjust the delivery rate through a throttle valve that is installed in the gas recirculation line in front of the gas pump 10 (not shown). In this case, the drive motor 12 of the gas pump 10 operates at a constant speed. The drive of the drive motor 12 is effected by an operating electronics 20.

According to the prior art, a fuel volume flow signal 13 is given to this operating electronics 20. This is shown in the figure 1 by the dashed line 17 connection. The operating electronics 20 controls the drive motor 12 of the gas pump 10 via a control line 22 so that, ideally, the speed of the drive motor 12 with the gas pump 10 generates a gas flow rate equal to the fuel flow rate.

In the prior art, this is achieved by a calibration procedure in which a gas flow meter is connected to the suction port 8 by means of an adapter (not shown). This gas flow meter is connected to a control unit, which is connected via an electrical connection to a calibration terminal 21 of the operating electronics 20. The control unit sets various gas flow rates of the vapor recovery system, which are measured with the connected gas flow meter. With these measured values, the control unit generates the calibration data which establish a relationship between the control signal 22 and the gas flow (gas volume flow) determined by the gas flow meter. At the end of the calibration process, these calibration data are transmitted via the connection 21 to the operating electronics 20 and stored there non-volatile. The controller and the gas flow meter will be removed from the assembly after this process.

Thus, the operating electronics 20 is able to set the required gas volume flow during a refueling operation. This is done according to the prior art via the dashed line 17. The connection 19 explained below is not present in the prior art. The structure according to the prior art is not as reliable as it is necessary, since with changes, e.g. due to aging, the required gas volume flow is no longer generated.

In the structure according to the invention is an automatic monitoring device with a control unit 15 and a gas flow meter 9 in the gas recirculation line 11. The gas flow signal 14 is guided together with the fuel flow signal 13 to the control unit 15. This generates a corrective control signal 19, which drives the operating electronics 20 for the gas recirculation. The dashed line 17 is not present in this case. The corrective control signal 19 may be a pulse train or a sequence of data words and is adapted to the type of input of the operating electronics 20; it has a shape like the fuel volume flow signal 13.

In the case of a difference between the fuel volume flow signal 13 and the gas volume flow signal 14 after a refueling operation, the corrective control signal 19 is generated for the following refueling operations in such a way that the operating electronics 20 generates a modified gas volumetric flow 14, which is then again more exactly the fuel Volume flow 13 corresponds. The corrective control signal 19 thus corresponds to a pseudo volume flow.

There occur in the sequence of refueling different fuel flow rates, since the nozzle 6 has different notches. The correction may be different for the different fuel flow rates. Therefore, as a further improvement, a fuel volume flow dependent correction characteristic can be determined.

The gas volume flow is tracked from tank operation to refueling the fuel flow, which avoids extensive maintenance over a longer period. It may be the case that e.g. in a total failure of the gas pump 10 no more agreement can be reached. In this case, the control unit 15 to an alarm output 16 an alarm signal and after the expiry of a configurable tolerance period to resolve the error output a signal that can be used for automatic shutdown of the affected dispensing point.

To reduce the differences that may occur in a statistical error in the measurement of a single refueling operation, the control unit 15 is preferably designed so that not only the difference between the fuel flow 13 and the gas flow rate 14 of the immediately preceding refueling Calculation of the correction is used, but that an appropriate averaging of several refueling operations is used as a basis. In particular, this may be a moving averaging according to the following approach: $${\mathrm{A}}_{\mathrm{N}\mathrm{+}\mathrm{1}}\mathrm{=}\left(\left(\mathrm{M}\mathrm{-}\mathrm{1}\right)\mathrm{/}\mathrm{M}\right){\mathrm{A}}_{\mathrm{N}\mathrm{-}\mathrm{1}}\mathrm{+}\left(\mathrm{1}\mathrm{/}\mathrm{M}\right){\mathrm{A}}_{\mathrm{N}}$$

Here, M is the number of values to be averaged over (eg, M = 10), A _{N + 1} is the deviation signal for the subsequent refueling process, A _N is the deviation signal determined for the given refueling operation, and A _N-1 is the last one Refueling process used deviation signal.

This averaging can be further improved to a dynamic moving averaging by a sliding variance is formed from the sequence of the individual deviation signals A _N , which determines the averaging parameter M in a suitable manner. In particular, with a greater variance, the averaging parameter M must be chosen to be larger.

Another possibility for minimizing the differences between the fuel volume flow signal 13 and the gas volume flow signal 14 as far as possible is the use of fuzzy logic (fuzzy logic). Here, the adjustment criteria for the deviation signal are given by the linguistic variables approximately representing the system. In particular, further criteria may be specified and evaluated, e.g. how far had to be readjusted. This parameter can be used to provide a maintenance warning in advance of a possible failure.

Another advantage offered by the method of corrective control is that of utilizing the above-described flow dependent correction feature to eliminate the need for calibration by an external gas flow meter and an external controller. In this case, a basic calibration is performed only at the factory. After installation in the dispenser, the electronics, following a corresponding command, perform a complete calibration by adjusting various gas flow rates and storing the values of the measured gas volumetric flow (gas volumetric flow signal 14). The control unit 15 can then adjust the gas volume flow 14 in accordance with the fuel volume flow 13 in a subsequent refueling operation. Thus, the usual calibration procedure can be dispensed with. The degradations of the gas recirculation system possibly occurring in the further tank operation are corrected as already described above.

Claims (10)

1. Method for correctively controlling a gas recirculating system at a filling station, at which, during a refuelling process of a motor vehicle, liquid fuel is fed by means of a fuel pump (3) from a storage tank (1) into the tank of the motor vehicle to be filled and the gas mixture which is located above the fuel in the tank to be filled is returned into the storage tank (1) by means of a gas pump (10), wherein the gas recirculating system is controlled according to the conveyed fuel by means of calibration data, having the steps

   - the fuel volume flow is measured using a fuel volume flow meter (4) and a fuel volume flow signal (13) characteristic of the fuel volume flow is generated and applied to a control device (15),

   - the gas volume is measured using a gas volume flow meter (9) and a gas volume flow signal (14) characteristic of the gas volume flow is generated and applied to a control device (15),

   - a corrective control signal (19) to be used for the next refuelling process is generated in the control device (15) by means of the fuel volume flow signal (13) and the gas volume flow signal (14) as well as optionally further signals,

   characterised in that
   the corrective control signal (19) has the same form as the fuel volume flow signal and the gas recirculating system is actuated for controlling the gas volume flow by using the unchanged calibration data by means of the corrective control signal (19) generated during the previous refuelling process.
2. Method according to claim 1, characterised in that the corrective control signal (19) is generated as a function of the absolute value of the fuel volume flow.
3. Method according to claim 1 or 2, characterised in that the corrective control signal (19) to be used for the next refuelling process is calculated in the control device (15), the corrective control signal (19) of at least one preceding refuelling process being taken into account as further signals.
4. Method according to claim 3, characterised in that the corrective control signal (19) to be used for the next refuelling process is calculated by forming mean values of deviation signals over a plurality of refuelling processes, a deviation signal characteristic of an individual refuelling process being preferably formed from the difference between the respective fuel volume flow signal (13) and the gas volume flow signal (14).
5. Method according to claim 4, characterised in that a deviation signal characteristic of an individual refuelling process is formed as a chronological mean value over this refuelling process.
6. Method according to claim 4 or 5, characterised in that the formation of mean values is a sliding formation of mean values according to the formulation $${\mathrm{A}}_{\mathrm{N}\mathrm{+}\mathrm{1}}\mathrm{=}\left(\left(\mathrm{M}\mathrm{-}\mathrm{1}\right)\mathrm{/}\mathrm{M}\right){\mathrm{A}}_{\mathrm{N}\mathrm{-}\mathrm{1}}\mathrm{+}\left(\mathrm{1}\mathrm{/}\mathrm{M}\right){\mathrm{A}}_{\mathrm{N}}$$

   

   
   where A_N+1 is the deviation signal to be used for the next refuelling process, A_N is the deviation signal determined for the given refuelling process, A_N-1 is the deviation signal used during the last refuelling process and M is the number of values used for the sliding formation of mean values.
7. Method according to claim 6, characterised in that a sliding variance is formed from a sequence of individual deviation signals A_N and is used to calculate a value for M.
8. Method according to one of claims 1 to 7, characterised in that the gas volume flow is controlled by means of the rotational speed of the gas pump (10, 12) and/or a throttle valve in a gas recirculation line.
9. Method according to one of claims 1 to 8, characterised in an alarm signal is generated when the corrective control signal (19) lies outside a predefined tolerance range.
10. Device for carrying out the method according to one of claims 1 to 9.

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