EP1205704B1 - Process for filling a vehicle tank with gas - Google Patents

Description

The invention relates to a method for filling a vehicle tank with gas according to the preamble of the independent claim.

Such a method is from the document US-A-5,628,349 known.

Gas-powered automobiles as an alternative to conventional motor vehicles powered by liquid fuels such as gasoline or diesel fuel are becoming increasingly important. Nowadays compressed natural gas is typically used as fuel for gas powered vehicles. However, more modern developments are also using gaseous hydrogen as fuel.

In order to allow the gas-powered vehicles a satisfactory range while keeping the dimensions of the vehicle tank within reasonable limits, the vehicle tanks are usually filled to high pressures. In the case of natural gas, for example, the vehicle tank is filled to a final pressure of about 200 bar based on a reference temperature of 15 ° C. In the case of gaseous hydrogen even higher ultimate pressures, for example, 600 bar, sought, which is primarily due to the lower energy density of hydrogen (compared to natural gas).

For safe gas refueling, the outside temperature is taken into account during filling. If one assumes that the final pressure at a reference temperature of 15 ° C for natural gas should be about 200 bar, then at an outside temperature of less than 15 ° C the refueling be terminated at a pressure of less than 200 bar, to ensure that with an increase in the outside temperature in the vehicle tank no unacceptably high pressure. Conversely, at an outside temperature of more than 15 ° C can be refueled up to a final pressure of more than 200 bar. The vehicle tanks are thus designed so that even with fluctuations in the outside temperature no unacceptably high pressure in the tank arises, provided that the maximum final pressure at the refueling endsprechend a pressure of 200 bar at the reference temperature of 15 ° C.

From the EP-A-0 653 585 For example, a gas refueling process and a corresponding plant is known, which allow a very simple and especially very fast refueling - comparable to the refueling of gasoline. According to the method proposed there, the vehicle tank is connected with a pressure-resistant line to a dispenser and filled the pressurized gas by means of the dispenser from a storage unit in the vehicle tank. First, the final pressure allowed for the currently prevailing temperature is calculated. Then, a small amount of gas is introduced into the vehicle tank to effect pressure equalization between the vehicle tank and the dispenser. The pressure prevailing in the vehicle tank initial pressure is measured after the pressure equalization in the dispenser and then filled a certain mass of gas in the vehicle tank. Thereafter, the mass flow of the gas is interrupted and in turn measured the pressure prevailing in the vehicle tank pressure in the dispenser. From these pressure values, a relationship between the mass of the discharged gas and the pressure in the vehicle tank is determined. Based on this relationship, a mass of gas is calculated such that at least one more mass of gas must be supplied to fill the vehicle tank to the final pressure. After the calculated mass of gas has been supplied to the vehicle tank, the mass flow is interrupted again and determines the pressure prevailing in the vehicle tank pressure in the dispenser. The operations of calculating an additional mass of gas, supplying this mass of gas, and interrupting the mass flow for pressure determination become repeated several times until the temperature-corrected final pressure is reached in the vehicle tank.

Based on this prior art, it is an object of the invention to propose another method for filling a vehicle tank with a gas, which allows an even faster and more accurate refueling, without concessions to the safety are needed. The method should also be applicable to very high ultimate pressures, as they are aimed at filling with gaseous hydrogen.

The problem solving method for filling a vehicle tank with a gas is characterized by the features of the independent claim.

• mit Hilfe einer Sensoreinrichtung, welche in dem Fahrzeugtank angeordnet ist, wird während der Befüllung der momentane Wert einer Kenngrösse bestimmt, welche repräsentativ für den momentanen Füllstand des Fahrzeugtanks ist,
• die Befüllung wird beendet, wenn die Kenngrösse einen vorgebbaren Endwert erreicht hat.

Thus, according to the invention, a method is proposed for filling a vehicle tank with a gas, in which the vehicle tank is connected to a discharge device with a pressure-resistant line and the gas under pressure is filled from the storage unit into the vehicle tank by means of the delivery device. The method comprises the following steps:

• with the aid of a sensor device, which is arranged in the vehicle tank, the momentary value of a parameter is determined during the filling, which is representative of the current fill level of the vehicle tank,
• the filling is terminated when the parameter has reached a definable final value.

Since the parameter, which is representative of the current fill level of the tank, is determined by means of a sensor arrangement which is arranged in the vehicle tank itself, the filling process can be carried out without interruption. The interruptions of the mass flow as in the EP-A-0-653 585 are proposed in each case to determine the current pressure prevailing in the vehicle tank pressure in the dispensing device are no longer necessary in the inventive method, because the measurement data required for the parameter online during the current filling in the vehicle tank are determined. As a result, the inventive method is particularly fast and accurate, without concessions to the security are necessary. The safety increases even more, because the level is determined based on measured data obtained in the vehicle tank. The collection of data in the vehicle tank allows an even more accurate determination of the filling level, so that the permitted limits for the filling can be optimally exploited because they can be fully exploited without the danger of exceeding the safety limits.

Preferably, the end value of the parameter, at which the filling is terminated, independent of the temperature, that is, a characteristic is selected, which represents the level of the vehicle tank, regardless of the temperature. Particularly preferably, the characteristic of the density of the gas in the vehicle tank is determined. For the density of the gas in the vehicle tank, a final value can be specified, namely the maximum permissible density or operating density, which is independent of the prevailing outside temperature during the filling. The temperature-independent end value for the parameter has the advantage that it is no longer necessary to calculate a temperature-corrected value for the final pressure of the refueling.

A further advantageous measure is that the parameter is first determined before the vehicle tank is filled with gas, so that the current level of the vehicle tank is known as the initial value before the start of the filling. This initial value is used during refueling to compare the current fill level determined in the vehicle tank with the data determined in the dispenser. If there are discrepancies in this comparison, this indicates an error and appropriate countermeasures can be taken. As is generally customary, the mass of the released gas is detected by measurement in the dispensing device. Taking into account the initial value, a control variable corresponding to the parameter is then determined from the emitted gas mass, the control variable is compared with the characteristic variable, and an error message or the cancellation of the filling takes place if the deviation between the parameter and the control variable exceeds a predefinable limit.

By this measure, the reliability of gas refueling can be significantly increased, because there are two different determinations of the current level of the vehicle tank. On the one hand, the characteristic variable representative of the current filling level is determined with the aid of the sensor device arranged in the vehicle tank, and on the other hand, the control variable corresponding to the characteristic variable is determined in the dispensing device on the basis of the mass of the discharged gas measured there. Due to the respective comparison of these two variables, errors in the filling, for example leaks, can be detected early and reliably.

According to a particularly preferred embodiment, the sensor device arranged in the vehicle tank comprises a temperature sensor and a pressure sensor with which the temperature and the pressure of the gas in the tank are measured. From this, the density of the gas is then determined as the parameter.

The inventive method is suitable for a variety of gas filling plants and in particular for those with which compressed natural gas or gaseous hydrogen is filled in a tank.

Further advantageous measures and preferred embodiments of the invention will become apparent from the dependent claims.

Fig. 1:

die wesentlichen Teile einer Gasbetankungsanlage zur Durchführung eines Ausführungsbeispiels des erfindungsgemässen Verfahren sowie einen zu befüllenden Fahrzeugtank in schematischer Darstellung, und

Fig. 2:

ein Flussdiagramm zur Veranschaulichung des Ausführungsbeispiels des erfindungsgemässen Verfahrens.

In the following the invention will be explained in more detail with reference to an embodiment and with reference to the drawing. In the schematic, not to scale drawing show:

Fig. 1:

the essential parts of a gas refueling system for carrying out an embodiment of the inventive method and a vehicle tank to be filled in a schematic representation, and

Fig. 2:

a flowchart illustrating the embodiment of the inventive method.

Fig. 1 shows a schematic representation of the essential parts of a gas filling plant for carrying out an embodiment of the inventive method, which is generally designated by the reference numeral 1. Furthermore, a gas-powered motor vehicle 30 is indicated, which has a vehicle tank 31, which is designed as a pressure vessel. The vehicle tank 31 serves as a storage container for a gaseous fuel, for example compressed natural gas or gaseous hydrogen, which is required for the operation of the motor vehicle 30. It is understood that the vehicle tank 31 is designed so that it easily withstands the ultimate pressure and the usual safety reserves. With the final pressure while the pressure is meant, to which the vehicle tank 31 is filled in the refueling. In the case of natural gas, for example, it is customary to choose the final pressure so that it corresponds to a pressure of about 200 bar at a reference temperature of 15 ° C. In the case of hydrogen, the final pressure is normally chosen higher, for example 600 bar based on the reference temperature 15 ° C.

The vehicle tank 31 is connected via a pressure-resistant connection line 36 with a filler neck 37 accessible from the outside, which is arranged here on the outside of the motor vehicle 30.

In the vehicle tank 31, a sensor device is provided, which in the exemplary embodiment described here comprises a pressure sensor 32 and a temperature sensor 33 with which the current pressure and the current temperature in the vehicle tank 31 can be detected metrologically. The sensors 32, 33 are connected via lines 35 to an electronics module 34 provided outside the vehicle tank 31, but in the motor vehicle 30. The electronic module 34 receives the measured values acquired by the sensors 32, 33 and processes them. Furthermore, the electronic module 34 serves to transmit data to the gas refueling installation 1.

In a memory 38, the volume of the vehicle tank 31 is stored, which is a constant size. The volume can be over one Signal line are transmitted to the electronic module 34. Of course, it is also possible to store the volume of the vehicle tank 31 directly in the electronic module 34.

The gas refueling system 1 shown only with its essential parts comprises a dispenser 2 and a stationary storage unit 3, in which the gas for refueling, so for example natural gas or gaseous hydrogen, is stored. Furthermore, a compression device, not shown, is provided which refills the storage unit 3 with gas again if necessary. Typically, the storage unit comprises a plurality of storage tanks, here three storage tanks, each of which is connected via a separate pressure-resistant connection line 4a, 4b and 4c to the dispenser 2.

The dispensing device 2 comprises a switching device 5, to which the three connecting lines 4a, 4b and 4c are connected. From the switching device 5, a pressure-resistant line 7 extends through a valve, which is preferably designed as a solenoid valve 6, and via a solenoid valve 6 downstream mass flow meter 8 to the output 9 of the dispenser 2. At the output 9, a pressure-resistant line 10 is connected is provided at its other end with a coupling 11 which is connectable to the filler neck 37 of the motor vehicle 30.

The dispensing device further comprises a communication module 13, an evaluation and control unit 12 and an operating module 14. About the operating module 14, the gas refueling system can be set by appropriate inputs in operation or operated. The operating module 14 further comprises a display unit on which z. B. the mass of the gas tanked or the price of the gas are displayed.

The communication module 13 receives data from the electronics module 34 of the motor vehicle 30 and forwards them via a signal line to the evaluation and control unit 12. The evaluation and control unit 12 is further connected via signal lines to the mass flow meter 8 and to the solenoid valve 6.

The solenoid valve 6 is an electromagnetically actuated valve, which is controlled by signals coming from the evaluation and control unit 12. By means of the solenoid valve 6, the flow connection for the gas between the switching device 5 and the output 9 can be opened or closed, so that by actuation of the solenoid valve 6 of the filling process can be started or ended.

The mass flow meter 8 is preferably a measuring device based on the Coriolis principle. Such Coriolis mass flow meters per se are well known. With them, the mass of the gas is measured, which is discharged during refueling.

The switching device 5 serves in each case to connect one of the connecting lines 4a or 4b or 4c to the line 7. If, for example, the connection line 4a is connected to the line 7 and the pressure in the storage tank 4a belonging to the storage tank of the storage unit 3 drops so far during refueling that the mass flow of the gas becomes too low, then with the changeover device 5 to another storage tank be switched by the line 7 is connected to the connecting line 4b or 4c.

For further details and embodiments, reference is here already made to the already cited EP-A-0 653 585 reference, where such gas filling plants are described in detail with the exception of the communication module.

The communication module 13 receives data, for example measured values or the volume of the vehicle tank 31, from the electronic module 34 of the motor vehicle 30. For this purpose, the communication module 13 is signal-connected to the electronic module 34. This can be done for example via a signal line 23. It is also possible to integrate the signal line 23 in the pressure-resistant line 10, for example, to arrange the signal line 23 on the outside of the line 10. Furthermore, it is possible to configure the signal connection between the electronic module 34 and the communication module 13 wirelessly, for example by means of radio or optical methods such as infrared signals.

The inventive method is based on using the sensor device which is arranged in the vehicle tank 31 to determine the current value of a parameter during filling, which is representative of the current level of the vehicle tank 31, that is, the current level of the vehicle tank 31st is determined by measurements in the vehicle tank 31 itself.

An exemplary embodiment of the method according to the invention will now be described with reference to FIG Fig. 2 illustrated flowchart explained in more detail. In this embodiment, the density ρ of the gas in the vehicle tank 31 is used as a characteristic. This parameter, which is also referred to as the operating density, has the advantage that a maximum permissible final value can be specified for it, which is independent of the respective prevailing temperature. Thus, it is no longer necessary to calculate a pressure dependent on the outside temperature prevailing at the refueling, at which the refueling is terminated. In previously known methods, the temperature-dependent final pressure for filling z. B. calculated from the isochoric behavior of the gas. In the method proposed here, a maximum allowable final value for the density of the gas can be specified, and the filling can then - regardless of the prevailing outside temperature - continue until this final value for the density in the vehicle tank 31 is reached.

When filling the currently prevailing in the vehicle tank density of the gas is constantly determined. With regard to operational safety, it is particularly advantageous to determine this density in two different ways, namely, on the one hand with the aid of the measured values of the sensors 32, 33 arranged in the vehicle tank 31 and, on the other hand, with the aid of the gas mass emitted by the delivery device 2 Mass flow meter 8 is measured in the dispenser 2. If these two values for the density deviate more than a predefinable limit from each other, this indicates an error. For example, a leak may have occurred or one of the sensors 32, 33 is not operating properly. By means of these two times each Determining the density can thus also dangerous states, such as overfilling of the vehicle tank 31 can be avoided.

wobei m_T die Masse des Gases im Fahrzeugtank 31 bezeichnet und V das Volumen des Fahrzeugtanks 31, das eine konstante Grösse ist.For the density ρ _{T of} the gas in the vehicle tank 31, the following applies: $${\mathrm{\rho }}_{\mathrm{T}}\mathrm{=}{\mathrm{m}}_{\mathrm{T}}\mathrm{/}\mathrm{V}$$

where m _T denotes the mass of the gas in the vehicle tank 31 and V the volume of the vehicle tank 31, which is a constant size.

wobei p_T den Druck im Tank bezeichnet, z den Realgasfaktor, der eine gasspezifische, von Druck und Temperatur abhängige Grösse ist, R die allgemeine Gaskonstante und T_T die Temperatur des Gases im Tank. Durch Messung der Temperatur T_T und des Drucks p_T im Fahrzeugtank 31 mittels des Temperatursensors 33 bzw. des Drucksensors 32 lässt sich dann also die momentane Dichte ρ_T im Fahrzeugtank 31 bestimmen. Der jeweilige Wert für den Realgasfaktor z kann beispielsweise aus einer gespeicherten Tabelle als Funktion des Drucks und der Temperatur entnommen werden.On the other hand, it follows from the gas equation $${\mathrm{m}}_{\mathrm{T}}\mathrm{/}\mathrm{V}\mathrm{=}{\mathrm{p}}_{\mathrm{T}}\mathrm{/}\left(\mathrm{z}\mathrm{\cdot }\mathrm{R}\mathrm{\cdot }{\mathrm{T}}_{\mathrm{T}}\right)$$

where p _T denotes the pressure in the tank, z the real gas factor, which is a gas-specific variable dependent on pressure and temperature, R the general gas constant and T _T the temperature of the gas in the tank. By measuring the temperature T _T and the pressure p _T in the vehicle tank 31 by means of the temperature sensor 33 and the pressure sensor 32, the instantaneous density ρ _T in the vehicle tank 31 can then be determined. The respective value for the real gas factor z can, for example, be taken from a stored table as a function of the pressure and the temperature.

For the refueling of the motor vehicle 30, the pressure-resistant line 10 of the dispensing device 2 is connected by means of the coupling 11 to the filler neck 37 of the motor vehicle 30. Furthermore, if appropriate, the signal line 23 is connected, on the one hand, to the electronic module 34 and, on the other hand, to the communication module 13. Before the vehicle tank 31 is filled with gas, the pressure sensor 32 or the temperature sensor 33 initially measures the initial pressure p ₀ or the initial temperature T ₀ , which prevail in the vehicle tank 31 before the start of filling (step 101 in FIG Fig. 2 ). From p ₀ , T ₀ and the corresponding value for the real gas factor z, the density ρ ₀ is then determined in step 102 as the initial value. ρ ₀ indicates the actual density of the gas in the vehicle tank 31 before the start of the filling. The electronic module 34 transmits the Value of ρ ₀ and the volume V of the vehicle tank 31 to be filled to the communication module 13 of the dispenser 2.

bestimmt. Der Anfangswert m₀ gibt also die Masse des Gases an, das vor dem Beginn der Befüllung im Fahrzeugtank 31 vorhanden ist.In the dispensing device 2, preferably in the evaluation and control unit 12, from the volume V of the vehicle tank 31 and the initial value ρ _0, the initial mass m _{0 of} the gas in the vehicle tank 31 according to the relationship $${\mathrm{m}}_{\mathrm{0}}\mathrm{=}{\mathrm{\rho }}_{\mathrm{0}}\mathrm{,}\mathrm{V}$$

certainly. The initial value m ₀ thus indicates the mass of the gas which is present in the vehicle tank 31 before the start of the filling.

In step 103 ( Fig. 2 ) now begins the process of filling. The evaluation and control unit 12 opens the solenoid valve 6 and the gas can flow from the storage unit 3 through the mass flow meter 8, the pressure-resistant line 10 and the connecting line 36 into the vehicle tank 31. During the filling process, the pressure sensor 32 and the temperature sensor 33 continuously or at short intervals measure the respective current pressure p _T or the respective current temperature T _T in the vehicle tank 31 (step 104). From these two values, in step 105, the current value ρ _T for the density of the gas in the vehicle tank 31 is determined according to the relationship given above and transmitted to the dispensing device 2.

During the filling process, in the dispensing device 2, the mass m _{G of} the released gas is constantly measured by means of the mass flow meter 8 (step 106). This is done, for example, at a rate of about one hundred pulses (measurements) per kilogram of gas delivered. The evaluation and control unit 12 of the dispensing device 2 determined in step 107 using the volume V of the vehicle tank 31, the initial mass m _{0 of} the gas in the vehicle tank and the current value of the mass m _{G of} the gas dispensed a comparison value ρ _m as a control variable for the Density of the gas in the vehicle tank according to the relationship $${\mathrm{\rho }}_{\mathrm{m}}\mathrm{=}\left({\mathrm{m}}_{\mathrm{0}}\mathrm{+}{\mathrm{m}}_{\mathrm{G}}\right)\mathrm{/}\mathrm{V}$$

In step 108, the control variable ρ _m is then compared with the density ρ _T determined in the vehicle tank 31. If the deviation between the control variable ρ _m and the density ρ _T determined in the vehicle tank exceeds a specifiable limit value D, the filling is ended (step 110) and / or an error warning is given. Otherwise, it is checked in step 109 whether the density p of the gas in the vehicle tank 31 has reached a predefinable end value ρ _E. Since it is already ensured on reaching step 109 that ρ _T and ρ _m differ by no more than D, it does not matter in principle whether ρ _T or ρ _{m are used} for the comparison with the final value ρ _E. Of course, the mean or a weighted average of ρ _T and ρ _{m may also be used} for the comparison with ρ _E. If the density p has reached the end value ρ _E , the filling is ended in step 110, otherwise the filling is continued.

An advantage of the method described is that the maximum permissible density or operating density ρ _E for a given gas is independent of the outside temperature at which the refueling takes place.

A further advantage, in particular with regard to the safety, is that the density of the gas in the vehicle tank is determined in two different ways.

In principle, it is possible that z. B. one of the two sensors 32,33, which are arranged in the vehicle tank, is already subject to error at the beginning of refueling. Among other things, this then leads to the fact that the initial mass m _{0 of} the gas is calculated wrongly and consequently also the control variable ρ _m determined in the delivery device is faulty. However, since the initial values p ₀ for the pressure and T ₀ for the temperature in the vehicle tank 31 recorded by means of the sensors 32, 33 enter the respective determination of the control variable ρ _m only as an initial condition, the values for the density determined in the tank are ρ _T On the one hand and the values for the control variable ρ _m diverge more and more with the progress of filling, so that such errors are detected before it comes to a dangerous overfilling of the vehicle tank 31.

It is understood that the respective calculation of the density ρ _T does not have to be carried out in the motor vehicle. It is also possible that the electronic module 34, the measured values or data of the temperature sensor 33 and the pressure sensor 32, so z. B. p ₀ , T ₀ , p _T , T _T , transmitted to the dispenser 2 and then there each determination of ρ ₀ and ρ _T occurs.

Claims (9)

1. A method for filling a vehicle fuel tank with a gas wherein the vehicle fuel tank (31) is connected to a delivery device (2) by a pressure-tight line (10) and the gas stored under pressure is filled into the vehicle fuel tank (31) from a storage unit (3) by means of the delivery device (2), having the following steps:

   - the instantaneous value of a parameter (ρ_T), which is representative of the instantaneous state of filling of the vehicle fuel tank (31), is determined during filling with the aid of a sensor device (32, 33) arranged in the vehicle fuel tank (31);

   - the filling is ended when the parameter (ρ_T) has reached a pre-settable end value (ρ_E), characterised in that the mass (m_G) of the gas supplied is detected by measurement in the delivery device (2), a control value (ρ_m) corresponding to the parameter (ρ_T) is determined therefrom, the control value (ρ_m) is compared in each case with the parameter (ρ_T), and an error message is output or filling aborted when then deviation between the parameter (ρ_T) and the control value (ρ_m) exceeds a pre-settable limit value (D).
2. A method in accordance with claim 1 wherein the end value (ρ_E) of the parameter is independent of the temperature.
3. A method in accordance with claim 1 or claim 2 wherein the parameter is determined first, before the vehicle fuel tank (31) is filled with gas, so that the instantaneous state of filling of the vehicle fuel tank is known as a starting value (ρ₀) before filling begins.
4. A method in accordance with any one of the preceding claims wherein the density (ρ_T) of the gas in the vehicle fuel tank (31) is determined as the parameter.
5. A method in accordance with any one of the preceding claims wherein the sensor apparatus arranged in the vehicle fuel tank comprises a temperature sensor (33) and a pressure sensor (32) with which the temperature and the pressure of the gas in the fuel tank is measured and the density (ρ_T) of the gas is determined therefrom as the characteristic parameter.
6. A method in accordance with claim 4 or claim 5 wherein:

   - the density (po) is first determined, before the vehicle fuel tank (31) is filled with gas, so that the instantaneous density of the gas in the vehicle fuel tank is known as a starting value before filling begins;

   - the volume (V) of the vehicle fuel tank (31) to be filled is transmitted to the delivery device (2);

   - the starting mass (m₀) of the gas in the vehicle tank prior to the start of filling is determined from the volume (V) and the starting density (po).
7. A method in accordance with claim 6 wherein a comparison value for the density of the gas in the vehicle fuel tank is determined as a control parameter (ρ_m) in the delivery device (2) with the aid of the volume (V) of the vehicle fuel tank (31), with the aid of the starting mass (m₀) of the gas in the vehicle fuel tank and with the aid of the mass (m_G) determined by measurement of the gas supplied, and is compared in each case with the density (ρ_T) determined in the vehicle fuel tank (31).
8. A method in accordance with claim 7 wherein filling is ended when the density reaches a pre-settable end value (ρ_E) or when the deviation between the control value (ρ_m) and the density (ρ_T) determined in the vehicle fuel tank exceeds a pre-settable limit value (D).
9. A gas refuelling plant operated in accordance with a method in accordance with one of the preceding claims.

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