BR102017011047A2 - METHOD AND SYSTEM FOR AUTOMATIC DIAGNOSTICS OF A VEHICLE TANK UNDERSTANDING LIQUID GAS - Google Patents

Abstract

method and system for automatic diagnosis of a vehicle tank comprising liquefied gas. The present invention relates to a method for the automatic diagnosis of a vehicle tank comprising liquefied gas. The method comprises the steps of automatically determining a first pressure value in the vehicle tank. The method further comprises automatically, after at least the passage of at least a first predetermined period of time, determining a second pressure value in the vehicle tank. The method nonetheless comprises automatically determining the performance of the vehicle tank with respect to thermal insulation based on said first and second determined pressure values. The present invention further relates to a system for automatically diagnosing a vehicle tank comprising liquefied gas, for a vehicle, for a computer program, and for a program product.

Description

The present invention relates to a method for automatically diagnosing a vehicle tank comprising liquefied gas. The method comprises the steps of automatically determining a first pressure value in the vehicle's tank. The method also comprises automatically, after at least the passage of at least a first predetermined period of time, determining a second pressure value in the vehicle tank. The method still comprises automatically determining the performance of the vehicle's tank with respect to thermal insulation based on said first and second determined pressure values. The present invention also relates to a system for the automatic diagnosis of a vehicle tank comprising liquefied gas, for a vehicle, for a computer program, and for a program product.

299

Method and system for automaticdiagnosisof a vehicle tank comprising üquefíed gas

TECHNICAL FIELD

The present disclosure reports to a method and a system for automatic diagnosis of a vehicle 5 tank comprising liquefied gas. The present disclosure further reports to a vehicle, a Computer program and a Computer program product.

BACKGROUND ART

Vehicles comprising gas engine usuaily require gas tanks for storing the gas whích is needed to operate the gas engine. There are at least two main principies when storing the gas. According to one principie, the gas is stored under high pressure in the gas tank of the vehicle. One kind of gas which can be used in connexion with this principle is compressed natural gas, CNG. By compressing the gas heavily a low volume is achieved.

According to another principle, the gas is stored at least partly in its liquid phase. One kind of gas which can be used in connexion with this principle is liquefied natural gas, LNG. By transforming the gas into its liquid phase, a reduction in volume is achieved. However, for transforming the gas into its liquid phase usuaily quite low temperatures are needed. The temperatures which are needed to keep the gas in its liquid phase are often below -110 degrees Celsius. This can be achieved by active cooling or by a good thermal isolation of the gas from its environment. For gas tanks in vehicles, often the latter is chosen since this requires no energy for active cooling at the vehicle. The good thermai isolation is usuaily provided by a vacuum layer around a Container comprising the gas. It is crucial that the vacuum does not deteriorate too much. Otherwise, too much heat will transferfrom the environment to the gas inside the tank and the gas will heat and evaporate. The evaporation will increase the pressure inside the tank, and usuaily a so-called boil-off valve is provided at the tank which will open when the pressure inside the tank will reach a certain threshold value for preventing damage on the gas tank due to high pressure. When the boil-off valve opens, the gas is usuaily released into the atmosphere and can thus no longer be used for propeiling

Petition 870170034936, of 05/25/2017, p. 9/77 the vehicle. It is thus important to assure that the vacuum is good enough for not transporting too much heat to the gas in the tank. There are also law reguiations requiring that the gas tank has to be able to store the iiquefied gas for a pre-determined amount of time when the gas tank is filied to a certain degree with gas having a certain pressure before the boil-off valve opens ,

Assuring that the vacuum has not deteriorated too much is today usuaily performed in the foliowing way: The vehicle is transported to a Service center where the gas tank is filied to a certain filling degree with iiquefied gas of a certain pressure. The gas pressure is then manually measured a first time, a longertime period is waited without turning on the gas engine, for example 8 hours, the gas measure is manually measured a second time, and the pressure change between the first and the second measurement is determined. This is compared to a pre-determined threshold of the specific tank in use. In case the pressure change is above the threshold, the gas tank is not operating according to law reguiations and needs maintenance. In case the pressure change is below the threshold the gas tank is operating properly regarding heat transition and can be used without further Service.

Such a procedure is quite time-consuming. Further, transporting the vehicle to and from the Service center, filling the gas tank so that a specific condition is achieved in the gas tank and manually measuring at least twice the pressure inside the gas tank requires quite some working time. There is thus a need for an improved method of performing a diagnosis of the vehicle tank.

SUMMARY OFTHE INVENTION

It is thus an objective of the disclosure to provide a method and a system for automatic diagnosis of a vehicle tank comprising Iiquefied gas. it is further an objective of the disclosure to provide an improved method and system for diagnosis of a vehicle tank comprising

Iiquefied gas. it is a further objective of the disclosure to provide an alternative method and system for diagnosis of a vehicle tank comprising Iiquefied gas. it is yet a further objective of the present disclosure to provide a vehicle comprising the system according to the present

Petition 870170034936, of 05/25/2017, p. 10/77 disclosure and to provide a Computer program and a Computer program product for performing the method according to the present disclosure.

At least parts of the objectives are achieved by a method for automatic diagnosis of a vehicle tank comprising liquefied gas. The method comprises the step of automatically determining a first pressure value in the vehicle tank. The method further comprises the step of automaticaíly, after at least a first pre-determined time-period has passed, determining a second pressure vatue in the vehicle tank. The method even further comprises the step of automaticaíly determining the performance of the vehicle tank regarding heat insulation based on said determined first and second pressure values.

This has the advantage that no human working time has to be spent on making a diagnosis of the vehicle tank. The method further can be performed without the need to visit a workshop.

In one example, the method further comprises the step of automaticaíly determining a filiing degree of the vehicle tank, Said automaticaíly determining of the performance of the vehicle tank regarding heat insulation is also based on said determined filiing degree. This allows to performing the automatic diagnosis of the vehicle under given conditions. It dispenses with the need to first provide a pre-determined filiing degree at the vehicle tank before a diagnosis can be performed. This further increases the flexibility of the method.

In one example, the method further comprises the step of determining whether the vehicle tank requires maintenance work based on said determined performance of the vehicle tank regarding heat insulation. This gives the possibility to move the vehicle only to a service center when needed. The number of visits to a service center for only realisíng that everything works fine with the vehicle can be reduced. Further, possible problems with the vehicle tank can be detected even when not visiting a service center, thusallowing performing a service center visit immediately when needed and not only at a certain time intervai.

in one example of the method said automatically determining of a first pressure value in the vehicle tank is performed during a second pre-determined time period after an indication that the vehicle is parked and the engine of the vehicle is turned off. This allows to perform the method while the main power system of the vehicle still provides power to most of the vehicle components.

Petition 870170034936, of 05/25/2017, p. 11/77

In one example of the method said indication that the vehicle is parked and the engine of the vehicle is turned off is a detected key-off event. This alíows a practica! implementation of the method.

In one example of the method the engine of the vehicle is kept turned off between said 5 determining of the first and second pressure values in the vehicle tank. This greatly simplifies calculations when implementing the method.

in one exampíe, the method further comprises the step of presenting a result regarding said determlned performance of the vehicle tank regarding heat insulation and / or whether the vehicle tank requires maintenance work to the driver of the vehicle. This allows the driver to perform measures immediately when needed.

At least parts of the objectives are also achieved by a system for automatic diagnosis of a vehicle tank comprising liquefied gas. The system comprises a sensor arrangement. The sensor arrangement is arranged for automatically determining a first pressure value in the vehicle tank and, after at least a first pre-determined time-period has passed, automatically determining a second pressure value in the vehicle tank. The system further comprises a control unit. The control unit is arranged for automatically determining the performance of the vehicle tank regarding heat insulation based on said determined first and second pressure values.

in one embodiment the system further comprises means for automatically determining a filling degree of the vehicle tank. Said control unit is then further arranged for basing said automatically determining of the performance of the vehicle tank regarding heat insulation also on said determined filling degree.

In one embodiment said system further comprises means for determining whether the vehicle tank requires maintenance work based on said determined performance of the vehicle tank regarding heat insulation.

In one embodiment said system further comprises means for determining that the vehicle is parked and the engine of the vehicle is turned off. Said sensor arrangement is arranged to perform said determining of said first pressure value in the vehicle tank during a second prePetition 870170034936, 05/25/2017, p. 12/77 determined time period after it is determined that the vehicle is parked and the engine of the vehicle is turned off,

In one embodiment of the system said means for determining that the vehicle is parked and the engine of the vehicle is turned off are arranged to base said determining on a detected key-off event.

In one embodiment the system is arranged to automatically determine the performance of the vehicle tank regarding heat insulation when the engine of the vehicle is kept turned off between said determining of the first and second pressure values in the vehicie tank.

In one embodiment the system further comprises means for presenting a result regarding said 10 determined performance of the vehicle tank regarding heat insulation and / or whether the vehicle tank requires maintenance work to the driver of the vehicle.

At least parts of the objectives are achieved by a vehicle. The vehicle comprises the system according to the present disclosure.

According to one aspect, the present disclosure reports to a Computer program for automatic 15 diagnosis of a vehicle tank comprising liquefied gas. The Computer program comprises program code for causing an electronic control unit or a Computer connected to the electronic control unit to perform the steps according to the method according to the present disclosure.

According to an aspect, the present disclosure reports to a Computer program product containing a program code stored on a computer-readabfe medium for performing method steps according to the method of the current disclosure, when said Computer program is run on an electronic control unit or a Computer connected to the electronic control unit

The system, the vehicle, the Computer program and the Computer program product have corresponding advantages as have been described in connection with the corresponding examples of the method according to this disclosure.

Further advantages of the present invention are described in the foliowing detailed description and / or wil! aríse to a person skiiied in the art when performing the invention.

Petition 870170034936, of 05/25/2017, p. 13/77

BRIEF DESCRIPTION OF THE DRAWINGS

For a more detailed understanding of the present invention and its objects and advantages, reference is made to the following detailed description which should be read together with the accompanying drawings. Same reference numbers refer to same components in the different figures. In the following,

Fig. 1 shows, in a schematic way, a vehicle according to one embodiment of the present invention;

Fig. 2a shows, in a schematic way, a system according to one embodiment of the present invention;

Fig. 2b shows, in a schematic way, a gas tank which can be used in connexion with the present disclosure;

Fig. 3a-c show, in a schematic way, relations for iliustrating the principle of the present invention;

Fig. 4 shows, in a schematic way, a flow chart over an exampie of a method according to the present invention; and

Fig. 5 shows, in a schematic way, a device which can be used in connection with the present invention

DETAILED DESCRIPTION

Fig. 1 shows a side view of a vehicle 100. In the shown exampie, the vehicle comprises a tractor unit 110 and a trailer unit 112. The vehicle 100 can be a heavy vehicle such as a truck. In one exampie, the trailer unit is connected to the vehicle 100. The vehicle 100 can comprise a gas engine. The vehicle comprises a gas tank. The vehicle comprises a system 299 for automatic diagnosis of a vehicle tank comprising liquefied gas. This is described in more detail in relation to Fig. 2a. The system 299 can be arranged in the tractor unit 110.

Petition 870170034936, of 05/25/2017, p. 14/77

In one example, the vehide 100 is a bus. The vehicle 100 can be any kind of vehicie comprising a gas tank. Other examptes of vehicfes comprising a gas tank are boats, passenger cars, construction vehicles, and iocomotives.

Although in the fotíowing mainly described in connexion with gas engines, it should be 5 emphasized that there is no requirement to have a gas engine connected to the gas tank for performing the idea of the present disciosure.

The term link refers hereín to a communication link which may be a physical connection such as an opto-electronic communication tine, or a non-physícal connection such as a wireless connection, e.g. a radio link or microwave link.

Fig. 2 shows schematicaliy an embodiment system 299 for automatic diagnosis of a vehicle tank comprising Líquefied gas. Not ali components of the shown embodiment are necessary for a system for automatic diagnosis of a vehicle tank comprising iiquefied gas. The shown embodiment has mainly been chosen to present a specia! usefui implementation of the idea of the present disciosure. The necessary components, however, are oniy those denoted in the independem claims.

System 299 comprlses a gas tank 210. The terms gas tank and vehicle tank are used interchangeably throughout the description. No different meaning is intended. A possible embodiment of a gas tank is described in more detail in relation to Fig. 2b. The gas tank 210 is arranged to store Iiquefied gas, such as LNG.

The system further comprises a gas engine 240. Said gas engine 240 is connected via a gas transport arrangement 260 to the gas tank 210. Said gas transport arrangement 260 can comprise pipes or the like. When the gas engine 240 is operated, gas wili be transported from the gas tank 210 through the gas transport arrangement 260 to the gas engine 240.

The system 299 comprises a sensor arrangement 220. The sensor arrangement comprises in one example a pressure sensor. The sensor arrangement is arranged to automaticaliy determine a first pressure value in the vehicle tank 210. The sensor arrangement 220 is arranged for, after at this a first pre-determined time-period has passed, automaticaliy determine a second pressure value in the vehicle tank 210. In one example, the sensor

Petition 870170034936, of 05/25/2017, p. 15/77 arrangement 220 is arranged to perform pressure measurements inside the gas tank. Said determining of the first and / or second pressure value can then be based on a first and / or a second pressure measurement, respectiveiy. In one example, the sensor arrangement 220 is arranged to measure pressure inside the vehicle tank 210 in the liquid phase of the gas. in one example, the sensor arrangement 220 is arranged to measure pressure inside the vehicle tank 210 in the gaseous phase of the gas. It should be understood that, although the gas is mainly stored in its liquid phase, the gas wili generally also always be partly in its gaseous phase in the gas tank 210. In a preferred example the gas inside the gas tank 210 is in its thermal equilibrium. A determining of the pressure in the gaseous phase of the gas wili then give the same result as a determining of the pressure in the liquid phase of the gas.

Some heat transfer wili always occurfrom the environment to the gas in the gas tank 210. This is explained in relation to Fig. 2b. A minimum heat transfer can always be assumed, at least due to dístance keeping elements described in relation to Fig. 2b. Assuming no gas is leaving the gas tank 210 to the gas engine 240, said minimum heat transfer wili thus inevitably result in a certain evaporation of parts of the liquid gas and thus in an increase of the pressure inside the gas tank.

A determined first and / or second pressure value by the sensor arrangement 220 wili have a certain uncertainty. This uncertainty can originate from a measurement uncertainty of the sensor arrangement 220. The measurement uncertainty is usually a design parameter of a sensor arrangement and can be pre-determined. The first pre-determined time period is preferably pre-determined in such a way that said minimum heat transfer from the environment to the gas inside the gas tank during that pre-determined time-period is so high that it wil! result in a change of the pressure inside the gas tank which is higher than the uncertainty of the determined first pressure value and / or which is so high that it can be determined by the sensor arrangement 220.

The system 299 further comprises a first control unit 200. Said first contro! unit 200 can be arranged to control operation of said sensor arrangement 220. Said first control unit 200 is arranged for communication with said sensor arrangement 220 via a link L220. Said first control unit 200 is arranged to receive Information from said sensor arrangement 220. Said sensor arrangement 220 can be arranged to transmit the determined first and / or second

Petition 870170034936, of 05/25/2017, p. 16/77 pressure value to the first control unit 200. in one example, the ftrst controí unit 200 is arranged at the sensor arrangement 220. In one example the first control unit 200 is arranged at a distance from the sensor arrangement 220. Said first control unit 200 could be an existing controí unit of a vehicle.

The first control unit 200 is arranged for automatically determining the performance of the vehicle tank 210 regarding heat insulation based on said determined first and second pressure values. This can be performed by determining the pressure change inside the gas tank 210 per time unit. This is further explained in relation to Fig. 3 and 4.

The system 299 comprises means 230 for automatically determining a filling degree of the 10 vehicle tank 210. Said means 230 can comprise a led sensor. I took sensors are known in the art and in principie any I took sensors can be used. In one example, said took sensor is a floating sensor, in one example, said took sensor is an optical sensor. It is known in the art how to determine the filling degree of a tank and what means can be used for achieving this. In one example, I didn't take a sensor is needed. In one example, said means 230 comprise a flow sensor.

IS Said flow sensor could be arranged at the gas tank 210 or the gas transport arrangement 260 for measuring the output flow of the gas out of the gas tank 210. When knowing the filling I took the gas tank 210 after a refining process and measuring the output flow of gas from the gas tank this ailows determining the filling degree of the gas tank 210, In one example, the sensor is an electrical sensor, for example a sensor adapted to measure the conductivity.

The first control unit 200 is arranged to control operation of said means 230. Said first control unit 200 is arranged for communication with said means 230 via a link L230. Said first control unit 200 is arranged to receive Information from said means 230. Said means 230 can be arranged to transmit the determined filling degree of the vehicle tank 210 to the first controi unit 200,

The first control unit 200 can be arranged for basing said automatically determining of the performance of the vehicle tank regarding heat insulation on said determined filling degree. This is described in further detail in relation to Fig. 3 and 4.

The system 299 can comprise means for determining whether the vehicle tank requires maintenance work based on said determined performance of the vehicle tank regarding heat

Petition 870170034936, of 05/25/2017, p. 17/77 insulation. Said first control unit 200 can be arranged fordetermining whether the vehicle tank requires maintenance work based on said determined performance of the vehicle tank regarding heat insulation. This is described in further detail in relation to Fig. 3 and 4.

The system 299 can comprise means 250 for determining that the vehicle is parked and the 5 engine of the vehicle is turned off. In one example said means 250 are detection means for detecting whether an ignition key has been removed from an ignition lock of the vehicle.

Removing the ignition key from the ignition lock is also referred to as a key-off event. In one example turning the key to a position for turning off the engine is referred to as a key-off event. In one example, turning the key to a position for turning off the engine and detecting an activated parking brake is referred to as a key-off event. Removing the ignition key from the ignition lock guarantees that the engine of the vehicle is turned off and is in general a strong sign that the vehicle is parked. Means for detecting whether an ignition key has been removed from an ignition lock of the vehicle are well known in the art. However, even keyless systems for starting vehicles are known in the art. Even these kinds of systems are usualíy equlpped with means for determining that the vehicle is parked and the engine of the vehicle is turned off.

The first control unit 200 is arranged to control operation of satd means 250. Said first control unit 200 is arranged for communication with said means 250 via a link L250. Said first control unit 200 is arranged to receive Information from said means 250. Said means 250 can be arranged to transmit Information regarding that the vehicle is parked and the engine of the vehicle is turned off to the first control unit 200.

The sensor arrangement 220 can be arranged to perform said determining of said first pressure value in the vehicle tank during a second pre-determined time period after it is determined that the vehicle is parked and the engine of the vehicle is turned off. The first control unit 200 can be arranged to send a control signal to the sensor arrangement 220 after the first control unit 200 receives Information that the vehicle is parked and the engine of the vehicle is turned off. Said second pre-determined time period is preferably less than one minute, preferably less than thirty seconds. After it is determined that the vehicle is parked and the engine of the vehicle turned off, most of the electronic systems of the vehicle are usually shut down after a third pre-determined time-period for saving energy. Said second

Petition 870170034936, of 05/25/2017, p. 18/77 pre-determined time period is preferabiy shorterthan said third pre-determined time period. This assures that the first pressure value is determined while the relevant electronic systems of the vehicle are not shut down yet.

The system 299 can comprise means 280 for determining that a turning on of the engine of 5 the vehicle is unlikely to happen in the near future. In one exampie, said means 299 comprise means for detecting that the ignition key is inserted in the ignition iock, Putting an ignition key in an ignition Iock is a sign of that it is unlikely to turn on the engine of the vehicle in the near future . Said means 280 are known in the art and it should be understood that corresponding means also exist for keyless systems.

The first control unit 200 is arranged to control operation of said means 280. Said first control unit 200 is arranged for communication with said means 280 via a link L280. Said first control unit 200 Is arranged to receive Information from said means 280. Said means 280 can be arranged to transmit Information regarding that a turning on of the engine of the vehicle is Iikely to happen in the near future to the first control unit 200.

The first control unit 200 can be arranged to send a control signal to the sensor arrangement 220 after the first control unit 200 recelves that a turning on of the engine of the vehicle is unlikely to happen in the near future. Said second sensor arrangement 220 can be arranged to determine said second pressure value after receiving of such a control signal. This assures that the second pressure value is determined before the vehicle engine is turned on.

The system 299 can comprise means 270 for presenting a result regarding said determined performance of the vehicle tank regarding heat insulation and / or whether the vehicle tank requires maintenance work to the driver of the vehicle.

In one exampie, said means 270 comprise visual means 271 for presenting a result regarding said determined performance of the vehicle tank regarding heat insulation and / or whether the vehicle tank requires maintenance work to the driver of the vehicle. Exampíes of such visual means 271 are screens, displays, lamps, LEDs, or the like.

In one exampie, said means 270 comprise audio means 272 for presenting a result regarding said determined performance of the vehicle tank regarding heat insulation and / or whether

Petition 870170034936, of 05/25/2017, p. 19/77 the vehicle tank requires maintenance work to the driver of the vehicle. Exampies of such audio means 272 are speakers orthe like.

In one example, said means 270 comprise tactíle means 273 for presenting a resuít regarding said determined performance of the vehicle tank regarding heat insulation and / or whether the vehicle tank requires maintenance work to the driver of the vehicle. Exampies of such tactiie means are vibrating means or the like,

The first control unit 200 is arranged to control operation of said means 270. Said first control unit 200 is arranged for communication with said means 270 via a link L270. Said first control unit 200 can be arranged to receive Information from said means 270.

The System 299 can comprise means {not shown) for communicating a result regarding said determined performance of the vehicle tank regarding heat insuiation and / or whether the vehicle tank requires maintenance work to an operator of the vehicle, such as a logistics company, a haulier , or the like, and / or to a Service provider of the vehicle. This can for exampie be achieved via means for wíreiess communication, such as module for communication with a mobile telephone network.

A second contro! unit 205 is arranged for communication with the first control unit 200 via a link L205 and may be detachably connected to it. It may be a control unit externai to the vehicie 100, it may be adapted to conducting the innovative method steps according to the invention. The second control unit 205 may be arranged to perform the inventive method steps according to the invention. It may be used to cross-ioad software to the first control unit 200, particufariy software for conducting the innovative method. It may alternativeiy be arranged for communication with the first control unit 200 via an internai network on board the vehicle. It may be adapted to performing substantiaily the same functions as the first control unit 200, such as performing an automatic diagnosis of a vehicle tank comprising liquefied gas. The innovative method may be conducted by the first control unit 200 or the second contro! unit 205, or by both of them.

The system 299 can perform any of the method steps described later in reiation to Fig. 4.

Petition 870170034936, of 05/25/2017, p. 20/77

Fig. 2b shows, in 3 schematic way, a view of an example of a gas tank 210 which can be used in connection with the present invention. The tank 210 comprises an inner vesse! 211. tn the inner vesse! the liquefied gas such as LNG can be stored. An insufflation arrangement 212 is arranged around the inner vessel 211. This insulation arrangement 212 can comprise insulation material. This insulation arrangement can comprise aluminum foils or any other reflective shield material. The tank 210 comprises an outerjacket 213. Preferably, there is a vacuum between the inner vessel 211 and the outer jacket 213. In one example, the vacuum is between the insulation arrangement 212 and the outer jacket 213, One side of the tank comprises a connection arrangement 214. The connection arrangement can be arranged to provide a connection to the combustion engine 240. The tank can further comprise a boil-off arrangement, such as a boil-off valve. The boil-off arrangement can be arranged to automatically open when a pre-determined pressure is reached inside the tank. Thus, the boiloff arrangement can provide a protection for the tank 210 to not be exposed to too high pressures.

The inner vessel 211 has to be kept at a distance from the outer jacket 213 to keep the vacuum as heat insulation layer between the inner vessel 211 and the outer jacket 213. This is usually performed by installing distance keeping elements (not shown) between the inner vessel 211 and the outer jacket 213. The distance keeping elements are adapted to prevent that the inner vessel 211 is in direct contact to the outer jacket 213. The distance keeping elements can consist of a material for minimisrng heat transfer between the inner vesse! 211 and the outer jacket 213 through the distance keeping eiement. In one example, said material is a ceramic materiai. However, aithough the distance keeping elements are arranged to reduce the heat transfer, there is always at ieast some heat transfer through these elements.

Fig. 3a-c show, in a schematic way, relations for illustrating the principle of the present invention. in Fig. 3a-c pressure values p inside a vehicle tank for liquefied gas are depicted as a function of time t. In the Fig. 3a-c it is assumed that the amount of gas in the tank is constant during the depicted time period. This can for example be achieved by turning off a gas engine so that no gas is leaving the gas tank. A first dashed line 310 depicts a possible behavior of how the pressure tn the gas tank can evolve. As can be seen from line 310, the pressure increases with increasing time t. This is due to the fact that heat is transferred from the environment to the gas in the gas tank. It should be observed that the curve usually does not

Petition 870170034936, of 05/25/2017, p. 21/77 start at a pressure of zero. Instead, the starting point can be any possible starting value for the pressure.

Turning to Fig. 3a, the possible behavior at a first given fiiling degree of the gas tank is depicted. A first pressure value pi can be determined at a first time ti. A second pressure value p2 can be determined at a first time t2. It is in general enough to determine two pressure values since the evolution of the pressure is linear up to a good approximation as long as the amount of gas in the gas tank is constant. In general, the heat transfer per time unit is not exactly constant. For example, a higber temperature of the environment will increase the heat transfer to the gas tank. As an example, the amount of heat is approximately proportional to the temperature difference between the environment and the inner of the gas tank. However, sync the interior of the gas tank in general is below -110 degrees Celsius, a change of the temperature of the environment by a few degrees will not significantly change the temperature difference between the inside and the outside of the gas tank, From the two determined pressure values a pressure difference âp = p2-pi can be determined. Further, a time difference Át = t2-ti can be determined between the second time and the first time. From these two values a pressure difference per time unit ρ '= Δρ / Δΐ can be determined. It should be noted that the pressure difference per time unit does not necessarily depend on the exact value of the first and the second pressure values, This is indlcated by the second dashed line 310a. The first pressure value of the second dashed line is denoted by pi _a and the second pressure value of the second dashed line is denoted by p2 _a . However, p 'will remain the same even for the pressure values of the second dashed line 310a. This is due to the fact that the pressure in the gas tank increases basically linearly over time. In another example, however, it is possible to inciude for example temperature and / or cloudiness as parameters in a model. In one example the temperature while determining the first pressure value and / or the temperature while determining the second pressure value are included in the model. In one example it is included in the model whether the sun was shining or whether it was clouded while determining the first and / or second pressure value. Even data relating to weather forecasts or measured weather data from a weather data Service provider can be included in the model. This is especially useful for the time in between determining the first and the second pressure value, since this dispensed the need to measure that kind of data at the vehicle while the engine is turned off.

Petition 870170034936, of 05/25/2017, p. 22/77

The first continuous line 320a depicts the behavior for a gas tank which is on the limit of fulfilling the iegal requirements regarding hold-time of the gas tank, ie how long time the gas tank can keep the gas before the gas ís released to the environment . A pressure difference per time unit p ' _c can be determined for the continuous line. This can in principle be done when the gas tank is designed as p ' _c wiil not change over time, as long as the legal requirements are not changing.

It is then possibie to compare p ' _c and p _c and to determine the performance of the vehicle tank regarding heat insulation based on this comparison. In one example, in case p _c is below p ' _c it can be concluded that the gas tank still fulfills the legal requirements. In one example, in case p _c equals or is higher than p ' _c it can be conciuded that the gas tank does not fulfill the legal requirements or wiil soon not fulfill them, in this case it can be concluded that the vehicle tank requires maintenance work. This is, for example, the case for the dotted curve 330. Thus, in case the determined pressure values of the vehicle correspond to pressure values on curve 330 instead of curve 310 or curve 310a it can be concluded that the vehicle tank requires maintenance.

It should be noted that p ' _c not necessarily need to be on the border between fulfilling the legal requirements or not. instead p ' _c can be slightíy lower than the legal requirements, This wiil add some security margin, and maintenance work can be recommended some time before the tank actually does not fulfill the legal requirements any longer.

In Fig. 3b, the possibie behavior at a second given ftlling degree of the gas tank is depicted. The dashed line 310 and the dotted line 330 correspond to what have been described in relation to Fig. 3a. The pressure difference per time unit at a given gas tank and a given temperature of the environment wiil depend on the filling degree of the gas tank. Generally, the higher the filling degree of the gas tank, the siower wiil the pressure increase per time unit. This is due to the fact that more mass of the gas is available at a higher filling degree and that the added heat energy thus can be distributed along a more mass of gases, which lowers the total temperature increase and thus the evaporation rate. Since the legal requirements usually are defined for a specific filling degree, this implies that a iarger filling degree allows a smalier pressure difference per time unit and a lower filling degree oniy allows a higher pressure difference per time unit before breaking the legal requirements. The second

Petition 870170034936, of 05/25/2017, p. 23/77 continuous line 320b indicates the behavior for a gas tank which is on the limit of fulfilling the tegal requirements regarding hold-time of the gas tank. Said second filling degree in Fig. 3b is higher than said First filling degree of Fig. 3a and as a consequence the value of p ' _c for the second continuous line 320b of Fig. 3b is lower than the value of p'c for the first continuous line 320a of Fig. 3a. Consequently, if a pressure values corresponding to the values of the first dashed line 310 for the second filling degree would be measured, it can be conciuded that maintenance Service is needed for the vehicle tank, aithough these values would require no maintenance Service in the case of Fig. 3a.

lt should be emphasized that the absolute values of the pressure in Fig. 3b do in general not 10 matter as has been described in relation to Fig. 3a. The lines in Fig. 3b only coincide at the origin for making them easier comparable. In practice, however, the depicted lines might be shifted upwards / downwards or sideward.

lt should also be noted that Fig. 3a and Fig. 3b only depict two different filling degrees. In general, however, the method according to the present disclosure can be generalized to any filling degree. This might result in a matrix where an alfowed value of p ' _c depends on the filling degree. In principle, for every different filling degree a corresponding graph to Fig. 3b could be provided.

lt should be noted that p ' _c so far mainly has been described in relation to iaw requirements. However, even other ways of determining the performance of the vehicle tank regarding heat insulatíon than the question whether maintenance work is required are possible. For example, a heat transfer per time unit could be determined. From this it can be determined how much the vacuum has degraded and / or a prediction could be made regarding how long time can pass before a maintenance Service wiil be required or recommended.

Fig. 3c depicts the situation at said first filling degree of the vehicle tank. In other words, the situation in Fig. 3c corresponds to the situation in Fig. 3a and what has been said regarding the first dashed line 310, the first continuous line 320a and the dotted line 330 correspond to what has said in relation to Fig, 3a. A third continuous line 320c is depicted. Said third continuous line 320c depicts a situation where the pressure difference per time unit is considerably higher than for the line 320a. Such a relation might for example happen in case one of the distance keeping elements gets damaged and the inner vessel and the outer jacket

Petition 870170034936, of 05/25/2017, p. 24/77 will touch each other directly or will be put very close to each other. This might for exampie happert in case the gas tank was exposed by a big hit. This can, for example, happen at an accident or in case the vehicle traveis over very uneven terrain so that objects on the ground or other objects hit the gas tank.

Said third continuous line 320c can correspond to an alarming threshold p ' _a of pressure difference per time unit. In case it is determined that the current pressure difference per time unit in the gas tank exceeds the alarming threshold, the driver could be informed to immediateiy perform maintenance to the vehicle tank or at least to transport the vehicle to a workshop for performing maintenance to the vehicle tank. In one example a service provider could be informed if an alarming threshold is exceeded. This aiiows the service provider to prepare measures for providing maintenance service to the vehicie. In one example authorities are informed in case an alarming threshold is exceeded. This might especialiy be useful in case other data provided by the vehicie indicates an accident. This data may for example be data indicating that an airbag has deployed, that a pipe in the vehicle broke, or the like. in Fig. 3c two thresholds p ' _c and p' _a are depicted. In general any number of thresholds can be provided. Any of the thresholds, such as p ' _a , can in general also depend on the filling degree as has been described in relation to p' _c in relation to Fig. 3b.

Fig. 4 shows, in a schematic way, a flow chart over an example of a method 400 according to the present invention. The method 400 for automatic diagnosis of a vehicle tank comprising liquefied gas starts by the optionai step 405.

In the optionai step 405 it is determined whether the vehicle is parked and the engine of the vehicle is turned off. This can be performed by detecting whether the ignition key has been removed from the ignition iock. This can be performed by a detecting a corresponding action in a keyiess system. As an example, it can be detected whether a certain button has been pressed which indicates that the vehicle is parked and the engine turned off. As an exampie, it can be detected whether the engine is actívely turned off and the parking brake has been activated. The method continues with step 410.

Petition 870170034936, of 05/25/2017, p. 25/77

In step 410 a first pressure value in the vehicle tank is automatically determined. This can be performed by a sensor arrangement as described in relation to Fig. 2a. In one example, step 410 is performed during a second pre-determined time period after step 405 has been performed. In one example step 410 is performed when step 405 is finished. Preferably step

410 is performed as long as the main power functionsof the vehicle are not turned off.

Preferably step 410 is performed when the engine is turned off. After step 410 an optionai step 415 is performed.

In the optionai step 415 it is determined whether the vehicle a turning on of the engine of the vehicle is likely to happen in the near future. In one example this comprises detecting that the ignition key is inserted in the ignition lock. Inserting the ignition key in the ignition lock is a sign that it is likely to soon start turn on the engine of the vehicle. This can be performed by a detecting a corresponding action in a keyless system. As an example, it can be detected whether a certain button has been pressed which indicates an intention to start, i.e. to turn on the engine. The method continues with step 420.

In step 420, after at least a first pre * determined time-period has passed sync step 410, a second pressure value in the vehicle tank is automatically determined. This can be performed by a sensor arrangement as described in relation to Fig. 2a. Said first pre-determined timeperiod is preferably chosen as described in relation to Fig. 2. The method continues with optionai step 430.

In the optionai step 430 a filling degree of the vehicle tank is automatically detected. This can be performed by element 230 as described in relation to Fig. 2a. The method continues with step 440.

In step 440 the performance of the vehicle tank regarding heat insulation is automatically determined based on said determined first and second pressure values. This can be performed as described in relation to Fig. 3a-c. in one example step 440 comprises determining a difference between said first pressure vaiue and said second pressure value. In one example step 440 comprises determining the time between determining the first pressure value and the second pressure value. in one example step 440 comprises determining the pressure change per time unit. Here, and in the whole document, the time when a pressure value is determined reports to the moment in time to which the pressure vaiue reports. In a common

Petition 870170034936, of 05/25/2017, p. 26/77 implementation the pressure value can be determined basically immediately, However, when performing a measurement relating to the pressure value and delaying the time to determine the pressure value out of the measurement results, for the scope of this disciosure the time of determining a pressure value shouid report to the moment in time to which the determined pressure value reports, for example the time when the measurement was performed.

In a preferred example the engine of the vehicle is kept turned off between performing step 410 and step 420. This assures that the amount of gas in the gas tank in general remains the same. Other measures for assuring that the amount of gas remains the same can be performed. As an example, it can be detected whether a boil-off valve opened or whether a refueiling occurred. In that case the method 400 can be aborted. It shouid, however, be emphasized that it is not a requirement that the engine is turned off during the method and the amount of gas in the gas tank is kept constant. Aiternatively, it could be determined how the amount of gas changes inside the gas tank. This can for example be performed with the help of flow sensors. Determining the performance of the vehicle tank regarding heat insulation can then be based on that determined change of the amount of gas inside the tank. This will generally make calculations more complex.

Step 440 can comprise basing said determining of the performance of the vehicle tank regarding heat insulation on said determined filling degree. This is explained in more details in relation to Fig. 2 and Fig. 3a-c. The method continues with the optional step 450.

In the optional step 450 it is determined whether the vehicle tank requires maintenance work. This is based on said determined performance of the vehicle tank regarding heat insulation. This has been explained in more details in relation to Fig. 3a-c. In one example step 450 comprises comparing a determined pressure difference per time unit to a pre-determined threshold pressure difference per time unit. In one example step 450 comprises determining that maintenance work is required when the determined pressure difference per time unit is above / below said pre-determined threshold difference per time unit. In one example step 450 comprises determining that maintenance work is not required when the determined pressure difference per time unit is below / above said pre-determined threshold difference per time unit. Step 450 can comprise determining whether urgent maintenance service is required. This

Petition 870170034936, of 05/25/2017, p. 27/77 has been explaíned in more detail in relation to Fig. 3c, especraliy in relation to curve 320c of Fig. 3c. The method continues with the optional step 460.

In the optional step 460 a result regarding said determined performance of the vehicle tank regarding heat insulation and / orwhetherthe vehicle tank requires maintenance work is presented to the driver of the vehicle. This can be performed with the heip of any of the elements 270-273 as described in relation to Fig. 2. In one exampie, a warning sound can be outputted by a speaker. In one exampie, a warning lamp can be lighted. in one exampie, a warning message can be displayed on a screen or a display. In one exampie, a warning icon can be lighted. Any of these actions can be performed alone or in combination in case it is determined that the vehicle tank requires maintenance work. In one exampie a general State regarding performance of the heat insulation of the vehicle tank can be presented to the driver, such as that said performance is according to the specifications. in one exampie said result is transmitted to a Service provider, to an operator of the vehicle, or to authorities. In one exampie, said result and / or said determined first and / or second pressure vatue and / or other data, such as weather / temperature data can be transmitted to a manufacturer of the vehicle and / or the vehicle tank. This alíows for improving models and / or detecting deviations from specifications. This also allows for detecting possibie problems during a manufacturing process.

The method 400 ends after step 460. It should be understood that the steps of the method do not necessarily have to be performed in the present order. Instead, the steps can also be performed in another order orin parallel.

The method can be repeated continuously or intermittently. It shouid also be understood that the method can be aborted at any time. This can for exampie be performed in case it is determined that said first pre-determined time cannot be reached without turning on the engine of the vehicle. In general, gas tanks of vehicles are designed to only require maintenance regarding the vacuum after some years. It is thus not a requirement that the method needs to be performed once per day. If the method succeeds performing once per week or once per month this might in general be well enough.

Petition 870170034936, of 05/25/2017, p. 28/77

In one example, the method 400 comprises the step of saving a status Information regarding the heat insulation performance of the vehicle tank in a memory. This status Information might then be read or analyzed by Service personal and / or a Computer at a workshop.

Figure 5 is a diagram of one version of a device 500. The control units 200 and 205 described with reference to Figure 2a may in one version comprise the device 500. The device 500 comprises a non-volatile memory 520, a data processing unit 510 and a read / write memory 550. The non-volatile memory 520 has a first memory element 530 in which a Computer program, eg, an operating system, is stored for controlling the function of the device 500. The device 500 further comprises a bus controller, a serial communication port, i / O means, an A / D converter, a time and date input and transfer unit, an event counter and an interruption controller (not depicted). The non-volatile memory 520 has also a second memory element 540.

The Computer program comprises routines for automatic diagnosis of a vehicle tank comprising liquefied gas.

The Computer program P may comprise routines for automatically determining a first pressure value in the vehicle tank. This may at least partly be performed by means of said first control unit 200 controlling operation of the sensor arrangement 220. The Computer program P may comprise routines for automatically, after at least a first pre-determined time-period has passed, determining a second pressure vaiue in the vehicle tank. This may at least partly be performed by means of said first control unit 200 controlling operation of the sensor arrangement 220. Said first and / or second pressure value can be stored in said non-volatile memory 520.

Claims (1)

The Computer program P may comprise routines for automatically determining a filling degree of the vehicle tank. This may at least partly be performed by means of said means 230. Said filling degree can be stored in said non-voiatile memory 520. The Computer program P may comprise routines automatically for determining the performance of the vehicle tank regarding heat insulation based on said determined first and second pressure values. This may at least partly be performed by means of said first control Petition 870170034936, of 05/25/2017, p. 29/77 unit 200, for example based on accessing stored pressure values from said non-volatile memory 520. The Computer program P may comprise routines for determining an indication that the vehicle is parked and the engine of the vehicle is turned off. This may at least partly be performed by means of said means 250. The Computer program may comprise routines for determining whether the vehicle tank requires maintenance work based on said determined performance of the vehicle tank regarding heat insulation. This might be based on whether a determined pressure difference per time unit is above or below a pre-determined threshold. The Computer program P may comprise routines for presenting a result regarding said determined performance of the vehicle tank regarding heat insulation and / or whether the vehicle tank requires maintenance work to the driver of the vehicle. This may at least partly be performed by means of said first control unit 200 controlling operation of any of the elements 270-273. The program P may be stored in an executable form or in compressed form in a memory 560 and / or in a read / write memory 550. Where it is stated that the data processing unit 510 performs a certain function, it means that it conducts a certain part of the program which is stored in the memory 560 or a certain part of the program which is stored in the read / write memory 550 . The data processing device 510 can communicate with data port 599 via data bus 515. The non-volatile memory 520 is intended for communication with the data processing unit 510 via data bus 512. The separate memory 560 is intended to communicate with the data processing unit via data bus 511. The read / write memory 550 is arranged to communicate with the data processing unit 510 via data bus 514. The links L205, L220, L230, L250, L270, and L280, for example, may be connected to the data port 599 (see Figure 2a). When data are received on the data port 599, they can be stored temporarily in the second memory element 540. When input data received have been temporarily stored, the data Processing unit 510 can be prepared to conduct code execution as described above. Petition 870170034936, of 05/25/2017, p. 30/77 Parts of the methods herein described may be conducted by the device 500 by means of the data Processing unit 510 which runs the program stored in the memory 560 or the read / write memory 550. When the device 500 runs the program, methods here described are executed. The foregoing description of the preferred embodiments of the present invention is provided for iliustrative and descriptive purposes. It is neither intended to be exhaustive, norto limit the invention to the variants described. Many modifications and variations wiII obviously suggest themselves to one skilled in the art, The embodiments have been chosen and described in order to best expiain the principies of the invention and their practical applications and thus make it possible for one skilled in the art to understand the invention for different embodiments and with the various modifications appropriate to the intended use. It should especially be noted that the system according to the present disclosure can be arranged to perform any of the steps or actions described in relation to the method 400. It should also be understood that the method according to the present disclosure can further comprise any of the actions attributed to an element of the system 299 described in relation to Fig. 2a. The same applies to the Computer program and the Computer program product. Petition 870170034936, of 05/25/2017, p. 31/77 CLAIMS 1. A method (400) for automatic diagnosis of a vehicle tank comprising iiquefied gas, the method comprising the steps of: - automatically determining (410) a first pressure value in the vehicle tank; - automatically, after at least a first pre-determined tlme-period has passed, determining (420) a second pressure value in the vehicle tank; and - automatically determining (440) the performance of the vehicle tank regarding heat insulation based on said determined first and second pressure values. 2. The method according to the previous claim, further comprising the step of: - automatically determining (430) a filling degree of the vehicle tank; and wherein said automatically determining of the performance of the vehicle tank regarding heat insulation is also based on said determined filling degree. 3. The method according to anyone of the previous claíms, further comprising the step of: - determining (450) whether the vehicle tank requires maintenance work based on said determined performance of the vehicle tank regarding heat insulation. 4. The method according to anyone of the previous claíms, wherein said automatically determining of a first pressure value in the vehicle tank is performed during a second pre-determined time period after an indication that the vehicle is parked and the engine of the vehicle is turned off. 5. The method according to the previous claim, wherein said indication that the vehicle is parked and the engine of the vehicle is turned off is a detected key-off event. 6. The method according to anyone of the previous claims, wherein the engine of the vehicle is kept turned off between said determining of the first and second pressure values in the vehicle tank. 7. The method according to anyone of the previous claims, further comprising the step of presenting (460) a result regarding said determined performance of the vehicle tank regarding heat insulation and / or whether the vehicle tank requires maintenance work to the driver of the vehicle . 8. A system (299) for automatic diagnosis of a vehicle tank (210) comprising Iiquefied gas, the system comprising: Petition 870170034936, of 05/25/2017, p. 32/77 - a sensor arrangement (220), being arranged for automatically determining a first pressure value in the vehicle tank (210) and, after at least a first predetermined time-period has passed, automatically determining a second pressure value in the vehicle tank (210 ); and - a control unit (200; 205), being arranged for automatically determining the performance of the vehicle tank (210) regarding heat insulation based on said determined first and second pressure values. 9. The system according to the previous claim, further comprising: - means (230) for automatically determining a filling degree of the vehicle tank; wherein said control unit (200; 205) further is arranged for basing said automatically determining of the performance of the vehicle tank (210) regarding heat insulation also on said determined filling degree. 10. The system according to anyone of the claims 8-9, further comprising means (200; 205) for determining whether the vehicle tank requires maintenance work based on said determined performance of the vehicle tank regarding heat insulation. 11. The system according to anyone of the claims 8-10, further comprising: - means (250) for determining that the vehicle is parked and the engine (240) of the vehicle is turned off; wherein said sensor arrangement (220) is arranged to perform said determining of said 20 first pressure value in the vehicle tank (210) during a second pre-determined time period after it is determined that the vehicle is parked and the engine of the vehicle is turned off. 12. The system according to the previous claim, wherein said means (250) for determining that the vehicle is parked and the engine of the vehicle is turned off are arranged to base said determining on a detected key-off event. 13. The system according to anyone of the claims 8-12, wherein the system is arranged to automatically determine the performance of the vehicle tank (210) regarding heat insulation when the engine of the vehicle is kept turned off between said determining of the first and second pressure values in the vehicle tank (210). 14. The system according to anyone of the claims 8-13, further comprising means (270273) for presenting a result regarding said determined performance of the vehicle tank Petition 870170034936, of 05/25/2017, p. 33/77 regarding heat insulation and / or whether the vehicle tank requires maintenance work to the driver of the vehicle. 15. A vehicle (100), comprising the system (299) according to anyone of the ciaims 8-14. 16. A Computer program (P) for automatic diagnosis of a vehicle tank comprising iiquefied gas, wherein said Computer program (P) comprises program code for causing an electronic controi unit (200; 500) now Computer (205; 500) connected to the electronic controi unit (200; 500) to perform the steps according to any of the ciaims 1-7. 17. A Computer program product containing a program code stored on a computerreadafaie medium for performing method steps according to any of ciaims 1-7, when said Computer program is run on an electronic controi unit (200; 500) or a Computer (205; 500) connected to the electronic controi unit (200; 500). Petition 870170034936, of 05/25/2017, p. 34/77 1/4 299 Fig. 1 299 270 Fig. 2a Petition 870170034936, of 05/25/2017, p. 36/77 2/4 211 240 212, Α ^ Α ------------- \ · ' ^A ' ** \ s '' S. ' ^S \ .v''Χ.'\ ·, Y \ Y. '· .. , x · X x \ Wl LM ' X 213 Fig. 2b 210 tl Ϊ2 Fig. 3a Fig. 3b Petition 870170034936, of 05/25/2017, p. 37/77 3/4 Fig. 4 Petition 870170034936, of 05/25/2017, p. 38/77 4/4 Fig. 5 514 512 550 530 540 520 τ 500 Petition 870170034936, of 05/25/2017, p. 39/77 ABSTRACT The present invention relates to a method for automatic diagnosis of a vehicle tank comprising Iiquefied gas. The method comprises the steps of automaticaliy determining a first pressure vaiue in the vehicle tank. The method further comprises automaticaliy, after at least a first pre-determined time-period has passed, determining a second pressure value in the vehicle tank. The method even further comprises automaticaliy determining the performance of the vehicle tank regarding heat insuffation based on said determined first and second pressure vaiues. The present invention further reports to a system for automatic diagnosis of a vehicle tank comprising Iiquefied gas, to a vehicle, to a Computer program, and to a Computer program product. (Fig. 2a) Petition 870170034936, of 05/25/2017, p. 35/77