EP4306841A1 - Fluid tank - Google Patents

Abstract

The invention relates to a fluid tank for vehicles, with an inner container for a fluid, in particular liquid gas, and a housing surrounding the inner container, wherein between the inner container and the housing there is a volume in which an insulation vacuum can be produced, in particular a high vacuum with a pressure in the range from 10^-3 to 10^-8 mbar or a fine vacuum in the range from 1 to 10^-3 mbar, and wherein in order to maintain an insulation vacuum that has been produced, the fluid tank is provided with at least one of its own vacuum pumps installed on the fluid tank, in particular a turbomolecular vacuum pump, and a connection for the vacuum pump and/or has a connection for an external vacuum pump device.

Description

The invention relates to a fluid tank for vehicles, with an inner container for a fluid, in particular a liquid gas, and with a housing surrounding the inner container, a volume being present between the inner container and the housing in which an isolation vacuum can be created. The isolation vacuum can be, for example, a high vacuum with a pressure in the range of 10 ^-3 to 10 ^-8 mbar or a fine vacuum in the range of 1 to 10 ^-3 mbar.

Due to the climate damage and limited availability of fossil fuels, alternative fuels are becoming increasingly important. Alternative fuels, in particular liquid gas such as liquid hydrogen, can be used, among other things, to power all types of vehicles (cars, trucks, vehicles used in agriculture such as tractors, construction machinery such as excavators, ships, aircraft). Even if they are not used for vehicle propulsion, it may be necessary to transport the alternative fuels in liquid form or gas - generally as fluid - using vehicles. In both cases, fluid tanks are used, which must meet certain requirements depending on the respective fluid.

Some fluids, especially liquid gases, need to be cooled, sometimes requiring extremely strong cooling to a temperature well below -200°C. Due to the large temperature difference between the fluid and the environment, effective thermal insulation is crucial so that heat input into the cooled fluid can be reduced to a minimum. The worse the thermal insulation, the greater it is so-called boil-off problem, i.e. problems due to losses of liquid gas due to the conversion of part of the cooled liquid into the gaseous phase.

A known option for thermally insulating containers for liquid gases is to provide an insulation vacuum surrounding the respective container. The vacuum in the volume between the container and a surrounding enclosure reduces heat transfer by convection. Heat transport through thermal radiation can be minimized by additional measures, for example by wrapping the container with a thermal insulation material, for example in the form of a so-called multilayer insulation (MLI), which is also referred to as super insulation.

In practice, there is no way to prevent the insulation vacuum from deteriorating over time. For example, the aim is to achieve an isolation vacuum of around 10 ^-5 mbar, which according to the common definition is a high vacuum. In other applications, for example, an isolation vacuum of around 10 ^-2 mbar can be aimed for, i.e. a fine vacuum according to the common definition. The deterioration of the insulation vacuum observed in practice, i.e. an increase in pressure in the volume between the inner container and the housing, can have various causes. Permeation through the walls of the surrounding housing and the inner container can contribute to increasing the pressure in the isolation vacuum. Desorption can also play an important role, for example from the inner wall of the housing, from the outer layers of any multilayer insulation or from cables and cable bushings passing through the insulation vacuum, if these are made of appropriate materials. Pipe penetrations of any kind can also be a source of permeation. Most of the effects mentioned above are often summarized under the term “outgassing”.

Especially in mobile applications, i.e. when fluid tanks have to be transported, it is difficult to control a deterioration in the insulation vacuum, which increases the heat input into the fluid, consequently favoring the conversion of the liquid phase into the gaseous phase, thus increasing the loss rate and so on overall reduces the efficiency of the alternative energy source in question.

The object of the invention is therefore to further reduce the heat input into the inner container in a fluid tank of the type mentioned above.

This problem is solved by the features of the independent claims.

In a fluid tank according to the invention, it is accordingly provided that in order to maintain an established isolation vacuum, the fluid tank is provided with at least one vacuum pump installed on the fluid tank and a connection for this vacuum pump and/or with a connection for an external vacuum pump device.

The invention creates a possibility of actively maintaining the insulation vacuum on the fluid tank by evacuating the volume between the inner container and the housing. With a dedicated vacuum pump installed on the fluid tank, this can be done more advantageously while the vehicle in question is moving on land, in water or in the air. An external vacuum pump device can be used when the vehicle is temporarily stationary, although in principle it is also possible to provide a mobile external vacuum pump device on one's own vehicle and thus carry out evacuation from vehicle to vehicle when vehicles are moving, such as when refueling in the air of airplanes.

The invention means that one does not have to rely exclusively on passive measures intended to counteract a deterioration in the insulation vacuum, such as thermal insulation of the inner container, or on measures to reduce outgassing.

The respective connection is preferably a flange connection, i.e. a connection that has a flange which is connected to a flange of the vacuum pump or can be connected to a flange of the external vacuum pump device.

Your own vacuum pump or the external vacuum pump device can also be used to create the isolation vacuum for the first time or to restore the isolation vacuum, for example after intentional or unintentional ventilation of the volume.

Known fluid tanks generally already have a connection that is used as part of the production of the fluid tank and therefore during the initial evacuation to create the isolation vacuum and is then closed, for example by means of a gate valve. A connection provided according to the invention for an external vacuum pump device can be provided in addition to such a connection only used during production. This allows the fluid tank to be made compatible with one or more specific external vacuum pumping devices that are not compatible with the port intended for manufacture. This may be the case, for example, due to non-existent standardization or due to different standards for the production of the fluid tank on the one hand and the operation of the fluid tank on the other.

In this way, for example, a vehicle fleet and a service network can be realized that are compatible with each other, with each vehicle in the fleet having each service station of the network in order to improve the isolation vacuum in the fluid tank and, if necessary, to fill up with new fluid.

Preferably, a connection provided according to the invention for an external vacuum pump device is provided with a closure device which is designed such that the connection can be opened and closed repeatedly in order to be able to repeatedly carry out pumping processes with the connection being closed in the meantime.

According to some developments of the invention, the own vacuum pump can have at least one suction opening and can be connected directly to an outside of the housing with the suction opening. This means that your own vacuum pump is installed directly on the fluid tank. A particularly good suction effect can be achieved in this way.

The own vacuum pump installed on the fluid tank can be installed on the fluid tank in such a way that when the fluid tank is arranged correctly on the vehicle and when the vehicle is used as intended, the influences of accelerations of the vehicle on moving parts of the vacuum pump are avoided or minimized. A movable part of a vacuum pump, in particular a turbomolecular vacuum pump, is, for example, a rotor that rotates about an axis of rotation during operation. The vacuum pump is preferably installed on the fluid tank in such a way that the rotor, i.e. its axis of rotation, is oriented perpendicular to the direction of travel of the vehicle when the fluid tank is arranged as intended on the vehicle and when the vehicle is used as intended. In this case, there are no gyroscopic forces acting on the rotor when the vehicle corners.

In some embodiments, the vacuum pump may have a rotor rotating about an axis of rotation during pumping operation, wherein the rotor is rotatably supported by at least two bearings spaced apart along the axis of rotation, and each bearing is a rolling bearing, in particular a ball bearing. Unlike vacuum pumps, in which one or every bearing for the rotor is a magnetic bearing, rolling bearings ensure that the rotor is supported particularly rigidly, which is particularly advantageous for pumping on a moving vehicle.

Furthermore, in some embodiments it can be provided that the own vacuum pump installed on the fluid tank has a pumping speed of less than 15 I/s and is designed in particular as a turbomolecular vacuum pump.

Since there is generally a comparatively large amount of time available to maintain the insulation vacuum created, meaning that in the application according to the invention, at least in most cases, a relatively high pumping speed of the vacuum pump is not important, it is sufficient to use a vacuum pump with a comparatively low pumping speed . Such vacuum pumps are characterized by a relatively low weight and therefore only slightly increase the overall weight of the vehicle. In practice, for example, turbomolecular vacuum pumps are known which have a pumping speed of around 10 l/s (for nitrogen) with a weight of less than 2 kg.

According to some embodiments of the invention, the connection for the own vacuum pump or for the external vacuum pump device can be arranged in a central region of a housing side away from curves or bends of the housing. This makes it possible to achieve comparatively large cross sections in the area of a suction opening of the vacuum pump, so that the effective suction speed, which is dependent in particular on the suction speed of the vacuum pump and on the respective conductance, is at least essentially the same everywhere.

Furthermore, it can be provided that the connection for the own vacuum pump or for the external vacuum pump device is arranged at a point where a comparatively high level of outgassing is expected. This can be the case, for example, in the area of open edges of a multilayer insulation that may be present.

According to further possible embodiments of the invention, the inner container can be surrounded by thermal insulation. As already mentioned, such thermal insulation can be a multilayer insulation. Such thermal insulation, which is also referred to as super insulation, is generally known and can consist of a large number of individual layers, for example plastic films coated with metal. The individual layers can be closed or perforated.

According to some possible embodiments, in a multilayer insulation provided as thermal insulation for the inner container, at least one of the outer layers can be perforated and at least one of the inner layers can be closed. It was found that with such a design of a multilayer insulation an effect can arise whereby particles can be pumped out of the outer, perforated layer or layers, whereas particles can be captured in the area of the inner layer or layers and thus bound there.

The fluid tank can be provided with a control device which is designed to control or regulate the operation of the vacuum pump according to a fixed program or depending on one or more parameters, in particular measured values. For this purpose, the fluid tank can be provided with one or more measuring devices, for example a pressure sensor and/or a temperature sensor. Alternatively or additionally, the fluid tank, in particular a control device of the fluid tank, can be designed to receive signals from Receive and evaluate measuring devices. Furthermore, alternatively or additionally, the fluid tank, in particular a control device of the fluid tank, can be designed to receive or evaluate one or more signals that represent a measure of the boil-off rate of the fluid.

The invention also relates to a vehicle with at least one fluid tank according to the invention. As already mentioned at the beginning, the vehicle can be a car, a truck, a vehicle used in agriculture such as a tractor or combine harvester, a construction machine such as an excavator, a ship or an aircraft.

In particular, it can be provided that the vehicle has a drive for moving the vehicle and that the fluid contained in the inner container of the fluid tank serves as fuel for the drive. However, this is not mandatory. The fluid tank can also only be used to transport the fluid by means of the vehicle, without the fluid being used to operate the vehicle. Alternatively, the fluid can not be used for the drive, but rather for other purposes to operate the vehicle.

Furthermore, it can be provided in the vehicle that the vacuum pump installed on the fluid tank is installed on the fluid tank in such a way that when the fluid tank is arranged on the vehicle as intended and when the vehicle is used as intended, a rotor of the vacuum pump, i.e. its axis of rotation, is perpendicular to the direction of travel of the vehicle is oriented.

As already mentioned elsewhere, this allows the influence of vehicle accelerations on the rotor to be avoided. In particular, no gyroscopic forces act on the rotor when the vehicle is cornering.

The invention further relates to a service station with at least one vacuum pump device for vehicles according to the invention.

The service station can be stationary and, for example, part of a service network that includes a large number of such service stations, which can be approached by the vehicles if necessary in order to carry out a pumping process to improve the insulation vacuum on the fluid tank of a respective vehicle by means of a vacuum pump device belonging to the respective service station to carry out. A service station can simultaneously be designed as a gas station and thus serve to fill the inner container of the fluid tank with the respective fluid, for example liquid hydrogen.

Alternatively, it is possible for the service station to be mobile and, for example, to form part of a tanker truck, so that when refueling a vehicle, for example with liquid gas - or shortly before or shortly after a refueling process - a pumping process can be carried out by means of the vacuum pump device in order to maintain the insulation vacuum of the Improve fluid tanks. Regardless of whether the mobile service station belongs to a tank truck or not, the mobile service station can be part of a service network made up of many individual mobile stations, each of which includes, for example, a service vehicle with one or more vacuum pump devices. Such a fleet can, for example, specifically target private or non-private companies that maintain a fleet of vehicles with many vehicles, each of which has one or more fluid tanks according to the invention.

The - stationary or mobile - vacuum pump device can have a suction head which is connected to a base part of the service station via a flexible connection, the suction head being designed as a vacuum pump or having a vacuum pump, or the suction head being connected to a vacuum pump of the service station via the flexible connection connected.

The invention further relates to a system with one or more vehicles, each as disclosed herein, and with one or more service stations, each as disclosed herein. In particular, it can be provided that each vacuum pump device of a respective service station is compatible with every connection of a respective fluid tank of a respective vehicle provided for an external vacuum pump device.

The invention also relates to a method for maintaining an insulation vacuum of a fluid tank according to the invention on a vehicle. In the process, the isolation vacuum is maintained by a pumping process. The pumping process can take place permanently or temporarily, in particular according to a regulation. Regardless of whether the pumping process takes place permanently or temporarily, the pumping process can only take place when the vehicle is at a standstill, when the vehicle is in any state of motion, or only when the vehicle is in one or more specific motion states.

To carry out the pumping process, the vehicle or the fluid tank can be provided with a control device which is designed to control or regulate the operation of the vacuum pump according to a fixed program or depending on one or more parameters, in particular measured values.

If the vehicle is, for example, an aircraft, it can be provided that no pumping process takes place during a take-off process or a landing process, but rather that the vacuum pump is only active when the aircraft is in normal flight operation, for example at a designated flight altitude. located.

A temporary pumping process can include a plurality of individual pumping processes that take place at regular or irregular time intervals. The time intervals can be fixed, for example. Alternatively, pumping processes can be triggered as part of a control system.

For example, it can be provided that an environmental parameter is used for a temporary pumping process, for example the outside temperature, whereby the number of pumping processes per unit of time increases with the outside temperature, i.e. at a higher outside temperature the vacuum pump is active more often than at a lower outside temperature.

It is preferably provided that the pumping process is carried out with a vacuum pump installed on the fluid tank. Alternatively, it is also possible to carry out the pumping process with an external vacuum pump device.

In order to carry out a controlled pumping process, it can be provided that a measure of the quality of the insulation vacuum is determined and a pumping process is started whenever the quality of the insulation vacuum falls below a predetermined level. A pumping process can therefore comprise a plurality of individual pumping processes that take place at intervals.

A measure of the quality of the insulation vacuum can be determined in different ways.

For example, the pressure in the volume can be measured and used as a measure of the quality of the insulation vacuum.

Alternatively or additionally, a boil-off rate of the fluid can be measured and used as a measure of the quality of the insulation vacuum.

Alternatively or additionally, it can be provided that an operating parameter of the fluid tank is used as a measure of the quality of the insulation vacuum. This operating parameter can be, for example, the performance of a device for cooling the fluid in the inner container.

Alternatively or additionally, an environmental parameter can be used as a measure of the quality of the insulation vacuum. The environmental parameter can be, for example, an expected or a measured increase in the outside temperature.

The invention also relates to the use of a vacuum pump, in particular a turbomolecular vacuum pump, for maintaining an isolation vacuum of a fluid tank for vehicles, the fluid tank having an inner container for a fluid, in particular liquid gas, and a housing surrounding the inner container, and between the inner container and the housing there is a volume in which the insulation vacuum can be created. The isolation vacuum can, for example, be a high vacuum with a pressure in the range of 10 ^-3 to 10 ^-8 mbar or a fine vacuum in the range of 1 to 10 ^-3 mbar.

For the own vacuum pump installed on the fluid tank and / or for the vacuum pump device of a service station, as disclosed herein, an additional backing pump can be provided, which generates a backing vacuum that may be required for the vacuum pump or the vacuum pump device, as is generally the case in vacuum technology is known.

Fig. 1

schematisch ein Fahrzeug, das mit einem erfindungsgemäßen Fluidtank versehen ist, und

Fig. 2

ein mit einem erfindungsgemäßen Fluidtank versehenes Fahrzeug an einer erfindungsgemäßen Servicestation, die eine Betankungsvorrichtung und eine Vakuumpumpeinrichtung umfasst.

The invention is described below by way of example with reference to the drawing. Show it:

Fig. 1

schematically a vehicle that is provided with a fluid tank according to the invention, and

Fig. 2

a vehicle provided with a fluid tank according to the invention at a service station according to the invention, which comprises a refueling device and a vacuum pump device.

Fig. 1 shows schematically the use of a fluid tank 11 according to the invention on a land vehicle 13, such as a car or a truck. As already mentioned elsewhere, other vehicles can also be equipped with one or more fluid tanks 11 according to the invention, for example aircraft or ships.

The fluid tank 11 comprises an inner container 15 and a housing 19 surrounding it. When the fluid tank 11 is filled, there is a fluid in its inner container 15, for example a liquid gas such as liquid hydrogen 17, which serves as fuel for a vehicle engine 35, with which the vehicle 13 is driven.

The liquid gas 17 within the container 15 is kept at a low temperature of, for example, -240 ° C by a cooling device, not shown. In order to avoid heating due to radiation, the inner container 15 is surrounded by thermal insulation in the form of a multilayer insulation (MLI) 33. Heat input through convection is minimized by the fact that there is an insulation vacuum in the volume 21 between the inner container 15 and the surrounding housing 19, which is already created during the production of the fluid tank 11. The isolation vacuum is, for example, a high vacuum in the range from 10 ^-3 to 10 ^-8 mbar or a fine vacuum in the range from 1 to 10 ^-3 mbar.

As explained in the introductory part, the insulation vacuum in volume 21 deteriorates over time, which is due to the large Temperature difference between the cooled liquid gas 17 on the one hand and the environment on the other hand results in increased heat input into the liquid gas 17 with the disadvantages already explained.

In order to be able to maintain the isolation vacuum within the volume 21 during operation of the vehicle 13, the fluid tank 11 is provided with its own vacuum pump 23, for example a turbomolecular vacuum pump. For this purpose, the housing 19 has a connecting flange 25 for the vacuum pump 23 in a central region of one side of the housing. In this way, the vacuum pump 23 is connected directly with its suction opening 31 to the opening of the housing 19 defined by the connecting flange 25.

The vacuum pump 23 includes, among other things - shown here purely schematically - a rotor 51 for one or more turbomolecular pump stages and one or more Holweck pump stages. The structure and functionality of vacuum pumps of this type are known, so there is no need to go into this in more detail. The vacuum pump 23 is installed in such a way that the rotor 51 is oriented vertically and thus perpendicular to the direction of travel of the vehicle 13.

For the rotational bearing of the rotor 51, which rotates around an axis of rotation 53 shown here in dashed lines during pumping operation, two bearings 55, which are spaced apart from one another along the axis of rotation 53 and are shown here purely schematically, are provided, each of which is a ball bearing, which means a comparatively rigid bearing for the rotor 51 is realized.

In the exemplary embodiment shown, the fluid tank 11 is additionally provided with a further connecting flange 27 on one of the other housing sides, which makes it possible to evacuate the volume 21 between the inner container 15 and the housing 19 by means of an external vacuum pump device, which will be discussed below in connection with Fig. 2 is received.

As already mentioned in the introductory part, the isolation vacuum in the volume 21 can be maintained by continuous operation of the vacuum pump 23 or by regulating the operation of the vacuum pump 23. As part of such a control, it can be provided, for example, to measure the pressure within the volume 21 using a pressure sensor (not shown) and to initiate a pumping process by activating the vacuum pump 23 when the measured pressure exceeds a predetermined value.

Alternatively, the control of the operation of the vacuum pump 23 could be based on a measurement of the so-called boil-off rate, which represents a measure of the evaporation of the liquid gas 17 within the container 15, i.e. the conversion from the liquid phase 17a into the gaseous phase 17b and can therefore be used as a measure of the quality of the insulation vacuum in volume 21.

It was found that a pressure increase within the volume 21 occurs more slowly than before if, after an initial pumping process to produce the isolation vacuum, at least one further pumping process takes place after a certain period of time. Permanent operation of the vacuum pump 23 is therefore not intended in all cases. Rather, such temporary operation of the vacuum pump 23 can suffice. Alternatively, in other applications it can be provided to operate the vacuum pump 23 permanently.

Control of the operation of the vacuum pump 23 can also depend on other conditions, for example on the movement behavior of the vehicle 13. For example, it can be provided that the vacuum pump 23 is controlled in such a way that pumping processes only take place when the vehicle 13 is stationary or is moving uniformly . In this way you can Influences of accelerations of the vehicle 13 on moving parts of the vacuum pump 23, in particular on its rotor 51, can be avoided.

In Fig. 1 Not shown are lines running within the volume 21, which lead, for example, from outside the housing 19 to the inner container 15 or to bushings formed on the inner container 15, or to devices arranged within the volume 21 but outside the inner container 15. As mentioned in the introductory part, such lines and bushings, for example as sources of outgassing, can lead to an increase in pressure in the volume 21 and thus to a deterioration in the insulation vacuum. The connection flange 25 for the own vacuum pump 23 or the connection flange 27 for an external vacuum pump device can be arranged taking this circumstance into account in such a way that the suction opening of the vacuum pump 23 or the external vacuum pump device is located at a point where a comparatively high level of outgassing is to be expected.

As in Fig. 1 shown, the connection flange 25 for the own vacuum pump 23 can be arranged in an area that is opposite a connection point 49, at which the individual layers of the multilayer insulation 33 are brought together and connected to one another.

A further optimization can be achieved in that - as already mentioned in the introductory part - not only closed or perforated layers are used for the multilayer insulation 33, but rather one or more inner layers located closer to the inner container 15 are closed and one or more outer layers are perforated are.

The inner container 15 is also provided with a connection 47, not shown here, for filling with the liquid gas 17.

Fig. 2 shows a vehicle 13 with a fluid tank 11 according to the invention at a stationary service station 37. For simplicity, the fluid tank 11 is shown here without thermal insulation, for example in the form of a multilayer insulation for the inner container 15. However, such thermal insulation is also provided in this exemplary embodiment.

The fluid tank 11 has in the exemplary embodiment Fig. 2 does not have its own vacuum pump 23 and is therefore not provided with a corresponding connection flange. Instead, a connection flange 27 is provided for an external vacuum pump device 29. This includes a suction hose 41 with a suction head 39 at the free end, which includes a vacuum pump 40, for example a turbomolecular pump.

The flexible connection formed by the suction hose 41 between the suction head 39, which is designed in this way as a vacuum pump, and a base 43 of the service station 37 makes it possible to connect the vacuum pump 40 directly to the connecting flange 27 of the fluid tank 11 of the vehicle 13 standing at the service station 37 in order to to evacuate volume 21.

The stay of the vehicle 13 at the service station 37 can also be used to refuel the vehicle 13, ie to fill the inner container 15 with liquid gas 17, for example liquid hydrogen. A refueling device 45 of the service station 37 is used for this purpose, the output end of which can be connected to a refueling connection 47 of the fluid tank 11.

Reference symbol list

11

Fluid tank

13

vehicle

15

inner container

17

Fluid

17a

liquid phase

17b

gaseous phase

19

Housing

21

volume

23

own vacuum pump

25

Connection for your own vacuum pump

27

Connection for external vacuum pump device

29

external vacuum pump device

31

Suction opening

33

Thermal insulation, MLI (Multilayer Insulation)

35

Vehicle drive, engine

37

Service station

39

suction head

40

Suction head vacuum pump

41

flexible connection, suction hose

43

Base

45

Refueling facility

47

Connection for refueling device

49

connection point

51

rotor

53

Axis of rotation

55

camp

Claims (15)

Fluid tank (11) for vehicles (13), with an inner container (15) for a fluid (17), in particular liquid gas, and a housing (19) surrounding the inner container (15), wherein between the inner container (15) and the housing (19) there is a volume (21) in which an isolation vacuum can be produced, in particular a high vacuum with a pressure in the range of 10 ^-3 to 10 ^-8 mbar or a fine vacuum in the range from 1 to 10 ^-3 mbar, and wherein, in order to maintain an established isolation vacuum, the fluid tank (11) is provided with at least one of its own vacuum pump (23), in particular a turbomolecular vacuum pump, installed on the fluid tank (11), and a connection (25) for the vacuum pump (23) and/or a connection ( 27) for an external vacuum pump device (29). Fluid tank (11) according to claim 1, wherein the own vacuum pump (23) has at least one suction opening (31) and is connected directly to an outside of the housing (19) with the suction opening (31). Fluid tank (11) according to claim 1 or 2, wherein the own vacuum pump (23) installed on the fluid tank (11) is installed on the fluid tank (11) in such a way that when the fluid tank (11) is arranged as intended on the vehicle (13) and when as intended When using the vehicle (13), a rotor (51) of the vacuum pump (23), which rotates about an axis of rotation (53) during pumping operation, is oriented with its axis of rotation (53) perpendicular to the direction of travel of the vehicle (13). Fluid tank (11) according to one of the preceding claims, wherein the vacuum pump (23) has a rotor (51) which rotates about an axis of rotation (53) during pumping operation, the rotor (51) being spaced apart from one another by at least two spaced apart along the axis of rotation (53). Bearing (55) is rotatably mounted, and each bearing (55) is a rolling bearing, in particular a ball bearing. Fluid tank (11) according to one of the preceding claims, wherein the own vacuum pump (23) installed on the fluid tank (11) has a pumping speed of less than 15 l/s. Fluid tank according to one of the preceding claims, wherein the connection (25, 27) for the own vacuum pump (23) or for the external vacuum pump device (29) is arranged in a central region of a housing side away from curves or bends of the housing (19). Fluid tank (11) according to one of the preceding claims, wherein the inner container (15) is surrounded by thermal insulation (33), in particular a multilayer insulation, in particular wherein at least one of the outer layers of the multilayer insulation is perforated and at least one of the inner layers of the Multilayer insulation is closed. Vehicle (13) with at least one fluid tank (11) according to one of the preceding claims, in particular wherein the vehicle (13) has a drive (35) for moving the vehicle (13) and that in the inner container (15) of the fluid tank (11) contained fluid (17) serves as fuel for the drive (35). Service station (37) with at least one vacuum pump device (29) for vehicles (13) according to claim 8,
in particular, wherein the vacuum pump device (29) has a suction head (39) which is connected to a base (43) of the service station (37) via a flexible connection (41), and wherein the suction head (39) is designed as a vacuum pump (23). or comprises a vacuum pump (40), or wherein the suction head (39) is connected to a vacuum pump of the service station (37) via the flexible connection (41). System with one or more vehicles (13) each according to claim 8 and with one or more service stations (37) each according to claim 9, in particular wherein each vacuum pump device (29) of a respective service station to each connection (27) provided for an external vacuum pump device of a respective Fluid tanks (11) of a respective vehicle (13) is compatible. Method for maintaining an insulation vacuum of a fluid tank (11) according to one of claims 1 to 7 on a vehicle (13),
in which the isolation vacuum is maintained by a pumping process, wherein the pumping process takes place permanently or temporarily, in particular according to a control, and/or wherein the pumping process only occurs when the vehicle (13) is at a standstill or only when the vehicle (13) is in one or more specific motion states ) takes place. Method according to claim 11, wherein the pumping process comprises a plurality of individual pumping processes taking place at regular or irregular time intervals,
and/or wherein the pumping process is carried out with a vacuum pump (23) installed on the fluid tank (11). Method according to claim 11 or 12, wherein in order to carry out a controlled pumping process, a measure of the quality of the insulation vacuum is determined and a pumping process is started each time the quality of the insulation vacuum falls below a predetermined level. Method according to claim 13, wherein the pressure in the volume (21) is measured and used as a measure of the quality of the insulation vacuum, and / or wherein a boil-off rate of the fluid (17) is measured and used as a measure of the quality of the insulation vacuum is used, and/or wherein an operating parameter of the fluid tank (11) is used as a measure of the quality of the insulation vacuum, in particular the performance of a device for cooling the fluid (17) in the inner container (15), and/or wherein as a measure for the An environmental parameter is used to determine the quality of the insulation vacuum, in particular an expected or measured increase in the outside temperature. Use of a vacuum pump (23, 40), in particular a turbomolecular vacuum pump, for maintaining an insulation vacuum of a fluid tank (11) for vehicles (13), the fluid tank (11) having an inner container (15) for a fluid (17), in particular liquid gas, and has a housing (19) surrounding the inner container (15), and wherein between the inner container (15) and the housing (19) there is a volume (21) in which the isolation vacuum can be produced, in particular wherein the isolation vacuum is a high vacuum with a Pressure in the range from 10 ^-3 to 10 ^-8 mbar or a fine vacuum in the range from 1 to 10 ^-3 mbar.

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