SE542542C2

SE542542C2 - Method and system for controlling a state of fuel provided to an engine

Info

Publication number: SE542542C2
Application number: SE1850672A
Authority: SE
Inventors: Erik Sunnegårdh; Magnus Johansson
Original assignee: Scania Cv Ab
Priority date: 2018-06-04
Filing date: 2018-06-04
Publication date: 2020-06-02
Also published as: WO2019235992A1; SE1850672A1

Abstract

A method and control unit for controlling a state of fuel provided from a fuel tank to an engine are presented. The fuel tank stores fuel in gaseous and liquid state, and includes at least one gaseous fuel output conduit and at least one liquid fuel output conduit. The method includes:- determining a maximal liquid torque Tbeing providable by the engine if fuel in the liquid state is provided to the engine;- determining a requested engine torque T;- comparing the requested engine torque Twith the maximal liquid torque T; and- controlling, if the requested engine torque Tis higher than the maximal liquid torque T; T> T; fuel flows through one or more of the at least one gaseous fuel output conduit and the at least one liquid fuel output conduit such that only fuel in the gaseous state is provided to the engine.

Description

METHOD AND SYSTEM FOR CONTROLLING A STATE OF FUEL PROVIDED TOAN ENGINE Field of invention The present invention relates to a method for controlling astate of fuel provided from a fuel tank to an engine, asdefined in the preamble of claim 1. The present invention alsorelates to a control unit arranged for controlling a state offuel provided from a fuel tank to an engine, as defined in thepreamble of claim 15. The present invention also relates to acomputer program and a computer-readable medium comprisinginstructions for carrying out the method according to the invention.

Background of invention The following background information is a description of thebackground of the present invention, which thus not necessarily has to be a description of prior art.

Vehicles, such as for example cars, buses and trucks, aredriven forward by an engine torque produced by an engine inthe vehicle. This engine torque is provided to the drivingwheels of the vehicle through a powertrain. The torque may becreated at least partly in a combustion engine by combustionof fuel being injected into the engine, i.e. injected into the cylinders of the engine.

The fuel used for the combustion in the engine may for exampleinclude liquified natural gas (LNG). Such liquified naturalgas (LNG) is often stored in at least one pressurized fueltank. In the tank, fuel in gaseous and liquid state is stored.The pressurized fuel tank includes a gaseous fuel outputconduit in contact with the gaseous state fuel, and a liquidfuel output conduit in contact with the liquid state fuel.

Thus, liquid state fuel may be provided to the engine through lO the liquid fuel output conduit, and gaseous state fuel may beprovided to the engine through the gaseous fuel output conduit.

The pressure Pgæ of the gaseous state fuel is used as, or isat least related to, a drive pressure Pmiw utilized forpushing the fuel out from the pressurized tank, i.e. utilizedfor driving the fuel out through the liquid or gaseous fueloutput conduits. Therefore, the pressure Pgæ of the gaseousstate fuel has to be high enough, i.e. above a minimum gaspressure threshold Pgæ¿mn, in order to be able to push the fuelout from tank. However, in order to prevent the pressurizedtank from exploding, the pressure Pgæ of the gaseous fuel maynot be allowed to increase above a maximal gas pressurethreshold Pgæ¿wX, which for example may have a value in theregion of 20 bar. A safety valve may be arranged for openingthe valve when the gaseous pressure Pgæ reaches the maximalgas pressure threshold Pgæ¿wX, thereby letting gaseous statefuel pass out to the ambient air, in order to reduce the gaseous pressure Pgæ.

Generally, the gaseous state fuel has a higher octanenumber/rating than the liquid state fuel has, since thelighter hydrocarbons are evaporated from the liquid state fuelwhen the gaseous state fuel is created. The liquid state fuelincludes a mixture of various hydrocarbons providing a loweroctane number/rating than the evaporated lighter hydrocarbons in the gaseous state fuel result in.

However, gaseous state fuel takes up a much greater volumethan liquid state fuel due to its much lower density.Therefore, the pressurized fuel tank should at least partlyinclude fuel in liquid form in order to provide an acceptable reach/range for a vehicle comprising the tank and the engine.

The differing octane numbers/ratings for the gaseous andliquid states of the fuel may be used such that the liquidstate fuel is used under some conditions and that the gaseousstate fuel is used under other conditions. For example, thegaseous state fuel may be used when a higher torque isrequested, e.g. for accelerations or for driving uphill. Toachieve this, a mechanical economizer has in conventionalsolutions been arranged to switch between supplying liquidstate fuel and gaseous state fuel to the engine. Such amechanical economizer has e.g. been arranged as a mechanicalswitch, which is able to switch between connecting the gaseousfuel output conduit of the tank to the engine and connecting the liquid fuel output conduit to the engine.SUMMARY OF INVENTION The mechanical economizer used in conventional solutions isarranged to switch between providing liquid and gaseous statefuel to the engine at a gas pressure Pgæ corresponding to apredetermined switch threshold Pgæ*W¿m of the gaseous statefuel, often having a value corresponding to a gas pressure Pgæof 12 bar; Pgæ = 12 bar. For example, if the gas pressure Pgæof the gaseous state fuel is increased above the switchthreshold Pgæ_W¿m, the economizer switches to provide onlygaseous state fuel to the engine. Correspondingly, if the gaspressure Pgæ of the gaseous state fuel is decreased below the switch threshold Pgæ_W¿m, the economizer switches to provide only liquid state fuel to the engine.

However, due to component individual variations, differentmechanical economizer individuals may switch at differentgaseous pressures Pgæ, although they are all designed toswitch at the threshold Pgæ_W¿m. Thus, different mechanicaleconomizer individuals may provide different states (gaseous/fluid) of the fuel to its respective engines at the lO same gaseous Pgæ. These component individual variationsresults in an unreliable control of the state of fuel beingprovided to the engine. Therefore, the torque being providableby the engine is also uncertain, since the octane number/rate of the fuel provided to the engine is not reliably controlled.

Also, the state of the fuel being provided to the engine hasan influence on the pressure Pgæ of the gaseous fuel, andtherefore has an influence on the drive pressure Pmiw used forpushing the fuel to the engine. Generally, if gaseous statefuel is provided to the engine, the pressure Pgæ of thegaseous fuel is decreased. The uncertainty of the mechanicaleconomizer may therefore cause drive pressure Pmiw problems.For example, if gaseous state fuel is provided to the enginealthough liquid state fuel should have been provided to theengine, the gaseous pressure Pgæ, and thus the drive pressurePmiæ, may be unnecessarily decreased, possibly to a point whenthe efficiency of the engine is affected since the fuel is notproperly provided to the engine. On the other hand, if liquidstate fuel is provided to the engine although gaseous statefuel should have been provided to the engine, the gaseouspressure Pgæ, may be unnecessarily increased, possibly to alevel at which the above-mentioned safety valve opens and letsgaseous state fuel pass out to the ambient air, whereby valuable fuel is wasted.

Thus, the uncertainty of the conventionally used mechanicaleconomizer may cause engine control difficulties, and may also unnecessary increase the fuel consumption.

It is therefore an object to solve at least some of the above- mentioned disadvantages.

The object is achieved by the above mentioned method forcontrolling a state of fuel provided from a fuel tank to an engine, the fuel tank storing fuel in gaseous and liquid lO state, and including at least one gaseous fuel output conduitand at least one liquid fuel output conduit according to thecharacterizing portion of claim l, the method including: - determining a maximal liquid torque Tmw_hq being providableby the engine if fuel in the liquid state is provided to theengine; - determining a requested engine torque Tæq; - comparing the requested engine torque Tnﬂ with the maximalliquid torque TMm¿uq; and - controlling, if the requested engine torque Tæq is higherthan the maximal liquid torque Tmﬂ¿uq; Tæq > Tmß¿Mq; fuel flowsthrough one or more of the at least one gaseous fuel outputconduit and the at least one liquid fuel output conduit such that only the fuel in the gaseous state is provided to the engine. lO Hereby, the gaseous state fuel, having a higher octanenumber/rate, may be saved for usage in situations when it isreally needed, i.e. in situations when a requested enginetorque Tæq is so high that it cannot be provided by combustionof liquid state fuel. This is a great improvement over theconventional mechanical economizer, which switches only based on the gas pressure Pgæ.

Thus, by usage of the present invention, it is possible tooptimize the state of the fuel and/or the ratio betweengaseous and liquid states of the fuel being provided to theengine, in order to match the needs of the engine, i.e. inorder to match the requested torque Tan. Hereby, the torquebeing providable by the engine may also be adapted to theusage of the vehicle, since fuel having an adapted octanenumber/rate may always be provided to the engine. Theconventional mechanical economizer, however, does not take theusage of the vehicle into consideration when performing the switching between gaseous and liquid state fuel.

Thus, the present invention facilitates a reliable andaccurate control of the controllable electronic economizer,which enables that higher torques may be provided by theengine when needed, since more gaseous state fuel (havinghigher octane number/rate) will be available for being provided to the engine when needed.

Also, the fuel consumption is reduced by usage of the present invention, since the safety valve needs to be opened more seldom.

According to an embodiment of the present invention, themethod further includes: - controlling fuel flows through one or more of the at leastone gaseous fuel output conduit and the at least one liquidfuel output conduit such that the fuel provided to the engineincludes a majority of the fuel in the liquid state if therequested engine torque Tæq is lower than or equal to the maximal liquid torque TMm¿uq; Tnﬂ S Tmmíhq.

Hereby, the higher octane number/rate gaseous state fuel issaved for usage in situations when it is really needed, i.e.in situations when a requested engine torque Tæq is so high that it cannot be provided by combustion of liquid state fuel.

According to an embodiment of the present invention, the fuelprovided to the engine includes one in the group of: - 100% fuel in the gaseous state; - a mixture of the fuel in the gaseous state and in the liquidstate; and - 100% fuel in the liquid state.

Hereby, an adaption of the ratios between gaseous and liquidstate fuel being provided to the engine is adapted in relationto the requested torque Tæq. The engine is then provided withthe fuel it needs to provide the requested torque Tnﬂ, at thesame time as no valuable gaseous state fuel is wasted.Instead, the higher octane number/rate gaseous state fuel is saved for usage in situations when it is really needed. lO L .i __.. » L L_ rä L L L k. LL. v L _ L. ._ 1_ _. _ L _.. _ .L. _ _ _ _ -LL _ _ I _ ._ _, _ w* ._ _ \_ _ L L _ ,_ ._ _ _ L_ L __. ___ L L 31 L ß __ _ L _ L L. _>~=1_« - . _ L “i . L L L~ ~ L s ~ »nx :s s ~~ ~ s ~~ s ~- s ~ ~ s ~ s . LL_ LL _ “e _ ._ _ \ C L LL .__ _ L _ _ _ ___ L_L LLM _. LL__ _ _ _ ___» L __ L_L _. L LL __ _L LL __ L _ LL L.L. L: _ _ L '- 1. Lt _.L ._ ' »L .»L I _. x »L__ - “L “L .L .L - __. _ __ _ _ L -L _ .L. _ _. _ _ _. _ . .__ _ L.L __ __ » _ L _ L L* L _ _ L 1 _ _ _ _ _ _ _ L __ L _,_L __ L_L , _ ___ _ L __ __ _ _LLL__ L.L LL __ LL __ __ L.LL L_ _____L L_ _ .C “. . L W L _ ._ “. _L __ _L _. L , L ___ L L__L L .LL _L ___ ___ L L__. _ » _ »LL L_»L_-L.LL L L L L__ L _ L. . _ _ t _. 1, ._ __ 1 4: _ ___ _. ._ .- .L. _._, ; _. -_. f ._ -_. L_L __. __. L. _. .L_. .L. .- »L __. __ L. L L _. L L .. .L. .L. ._ .L_. _._ __ _ _ __ _ _ ._ _ -_ I. ._ ._ I. _ “L .1 'W F» 1* . __: _ _ _ '- L? 'I _ _ ._ ___ 1L_ __ . _ -,_ _ _i.. __ _ _ L _ L L_ L.. _ __ _ _ __ _L _ _L _. _- __. _.. -_. ___ __ ___ ._L . » -__ _. ___ ___ «_. ___ j ___. ._L L L _. ._L ___ »_ _._ _ f. ___ 1.. .__ _ "- _ _. :_ L- L ._. ._ ._ _ ._ .C . _. _ 'I .___ _ ___ _ :_ ._ .__ _. Li. . _. ._ . *» 1- ___ LL, __ _.. L __ L. L.L LL __ .L L_- L_L L L L _ L L .L »_ _L .L _.. ___ _ L L L L.L _L L_L .L_L_L _.L .L_L _.-1 . . LT. 1 1 L -L. 1. L L_ L L .LL L.L _ _ L L »_ L L L. L L L LL. 1. _, L L'_ . _ .JL » _ L_. .L. _ _ _ _. _ _ _ . _ _ __'L 't _\ 1 W \. 'L _ v\ L.k Lt L»L _ L LLL __ g L _ LLx »L __ i'š'-'*.L L ._39 _, L _ L LL »_ L _ . _ L L 1 L. _ __ 1 __ 1, » _ L_ L _ _ »_ _ _ _ _ _. L _ _ L » L _ _ _ __ _L_ _ _ ^ L l. ._ L _" _ _ _ _ _,LLL_. __ _ L ___ L LL__ ,LL _. LL _ ___ __ , __ _ _ ___ ___,- ^ L L . _ A L - __ _ L .L ~ ^ _ _ ^ L v LL _.L___ LL __ L L __ ___ LL _ , LLL L_L __ L ,» L L L L L___L L_L _L L _ _LL_L ,_ _ _ __. _ O. .SI _ _ “ _ _ _ ï'_ . » _* L L __. a L_ L, __ _ L n, L __ _ LL__ L _ __ _ , _ :_ L_L _L L ,».» L L L .L __» 1 _ _' . _ 1. L* 1 -LT L L _ __ _ L* 11 __ L r., _ L r~ ____ _ . _ ,-: L __ . _ _ J, __ 1,. L L LL_ _ _ _ -:-. L _ L. L L.L *.L. _ _ _ L _ L _ _ _ L _»_ _ L __ __. _ “ _L L ___ _. _.. L. kr. L _ L __. L According to an embodiment of the present invention, the firstpressure threshold P¿¿h is determined based at least on one ormore in the group of: - at least one feature of the fuel tank; and - at least one feature of a fuel providing system arranged for providing the fuel from the tank to the engine.

Since the first pressure threshold P¿¿h is adapted to thefeatures of the fuel tank and/or of the fuel providing system of the vehicle, is it secured that the gas pressure Pgæ is lO high enough for being able to push the fuel out from precisely the fuel tank arranged in the system/vehicle.

According to an embodiment of the present invention, themethod further includes: - determining a pressure Pgæ of the fuel in the gaseous state;- comparing the pressure Pgæ of the fuel in the gaseous statewith a second pressure threshold P¿¿h, the second pressurethreshold P¿¿h being related to a maximally allowed pressurePgæ¿wX for the tank; and - controlling, if the pressure Pgæ is higher than the secondpressure threshold P¿¿h; Pgæ > P¿¿h; fuel flows through one ormore of the at least one gaseous fuel output conduit and theat least one liquid fuel output conduit such that only the fuel in the gaseous state is provided to the engine.

Hereby, the risk for wasting fuel due to opening of the safetyvalve is reduced, since the second pressure threshold P¿¿h isdetermined related to a maximally allowed pressure Pgæ¿wX forthe tank. For example, the herein described second pressurethreshold P¿¿h may, according to an embodiment, be equal to themaximally allowed pressure Pgæ¿wX for the tank minus a safety offset Pgas_offsetr' P2_th I Pgas_offsetr' WhGJfG the Safety Pgas_max _offset Pgæ_Mf¶¶ has a value providing reliable protection against a tank explosion.

Also, a pressure region P¿¿h - P¿¿h between the first pressurethreshold P¿¿h and the second pressure threshold P¿¿h isdefined by some embodiments of the present invention. Thispressure region P¿¿h - P¿¿h does not even exist for aconventional mechanical economizer, since the conventionalmechanical economizer switches only based on the pressure. Thepressure region P¿¿h - P¿¿h created by the embodiments of the present invention may be utilized for controlling the electronic controllable economizer in relation to therequested engine torque Tum. Hereby, a more efficient usage ofthe gaseous state fuel, and thereby also a more powerful engine, may be achieved.

According to an embodiment of the present invention, thesecond pressure threshold P¿¿h is determined based at least onone or more in the group of: - a required volume of the fuel in the gaseous state in thetank; - a type of vehicle including the fuel tank and the engine; - a usage of a vehicle including the fuel tank and the engine;- at least one feature of the fuel tank; - a level of fuel in the fuel tank; - a relation between amounts of the fuel in the gaseous stateand the fuel in the liquid state in the fuel tank; - a temperature in the fuel tank; - an ambient temperature outside the fuel tank; and - at least one requirement related to a full tank parking time period for a vehicle including the fuel tank and the engine.

Since the second pressure threshold P¿¿h is adapted to thefeatures of the fuel providing system of the vehicle, the riskfor having to open the safety valve is reduced, whereby also a reduction of the fuel consumption is achieved over time.

According to an embodiment of the present invention, themaximal liquid torque Tmm¿uq is determined adaptively when the engine runs, and is based on a performance of the engine.

Hereby, the maximal liquid torque Tmﬂínq may adaptively be very accurately determined.

According to an embodiment of the present invention, information related to the controlling of the fluid flows is lO ll stored and utilized together with the performance of theengine resulting from the controlling in/for the adaptive determination of the maximal liquid torque Tmw_nq.

Hereby, the maximal liquid torque Tmﬂínq may be accurately determined.

According to an embodiment of the present invention, a valueof the maximal liquid torque TMX¿uq is actively adjusted, andthe adaptive determination of the maximal liquid torque TMﬂ_nqis based on the active adjustment and on a performance of theengine resulting from the active adjustment of the maximal liquid torque Tmwínq.

Hereby, the maximal liquid torque Tmﬂínq may be accurately determined by the active adaptive determination.

According to an embodiment of the present invention, themaximal liquid torque Tmm¿uq is determined by running a testengine corresponding to the engine on the fuel in the liquid state in a test cell and measuring a resulting torque Tnq¿e¶.

Hereby, the maximal liquid torque Tmﬂínq may be easily determined, with no addition to the complexity of the vehicle.

According to an embodiment of the present invention, themaximal liquid torque Tmm¿uq is determined by: - determining a tendency for engine knocking when the fuel inthe liquid state is provided to the engine; and - determining the maximal liquid torque Tmw_hq based on the determined tendency for engine knocking.

Hereby, the maximal liquid torque Tmﬂínq may be easily andaccurately determined. The maximal liquid torque Tmw_hq may bedetermined in the vehicle. The value for the maximal liquid torque Tmﬂínq may be updated continuously. 12 The object is also achieved by the above-mentioned controlunit arranged for controlling a state of fuel provided from afuel tank to an engine, the fuel tank storing fuel in gaseousand liquid state, and including at least one gaseous fueloutput conduit and at least one liquid fuel output conduit,according to the characterizing portion of claim 15. Thecontrol unit includes: - first means arranged for determining a maximal liquid torqueTMﬂ_Uq being providable by the engine if fuel in the liquidstate is provided to the engine; - second means arranged for determining a requested enginetorque Tæq; - means arranged for comparing the requested engine torque Tæqwith the maximal liquid torque TMm¿mq; and - means arranged for controlling, if the requested enginetorque Tnﬂ is higher than the maximal liquid torque TmM¿uq; Tæq> TMm¿mq; fuel flows through one or more of the at least onegaseous fuel output conduit and the at least one liquid fueloutput conduit such that only the fuel in the gaseous state is provided to the engine.

The control unit has the same advantages as stated above for the method.

According to an embodiment of the present invention, the meansarranged for controlling the fuel flows is further arrangedfor: - controlling fuel flows through one or more of the at leastone gaseous fuel output conduit and the at least one liquidfuel output conduit such that the fuel provided to the engineincludes a majority of the fuel in the liquid state if therequested engine torque Tæq is lower than or equal to the maximal liquid torque TMm¿uq; Tan S TMm_Uq. 13 According to an embodiment of the present invention, the fuelprovided to the engine includes one in the group of: - 100% fuel in the gaseous state; - a mixture of the fuel in the gaseous state and in the liquidstate; and - 100% fuel in the liquid state.

According to an embodiment of the present invention, thecontrol unit further includes: - means arranged for determining a pressure Pgæ of the fuel inthe gaseous state; - means arranged for comparing the pressure Pgæ of the fuel inthe gaseous state with a first pressure threshold P¿¿h, thefirst pressure threshold P¿¿h being related to a pressurePgæ¿mn needed for providing the fuel flows through one or moreof the at least one gaseous fuel output conduit and the atleast one liquid fuel output conduit; and - means arranged for controlling, if the pressure Pgæ is lowerthan the first pressure threshold P¿¿h; Pgæ < P¿¿h ; fuel flowsthrough one or more of the at least one gaseous fuel outputconduit and the at least one liquid fuel output conduit suchthat only the fuel in the liquid state is provided to the engine.

According to an embodiment of the present invention, thecontrol unit further includes means arranged for determiningthe first pressure threshold P¿¿h based at least on one or morein the group of: - at least one feature of the fuel tank; and - at least one feature of a fuel providing system arranged for providing the fuel from the tank to the engine.

According to an embodiment of the present invention, the control unit further includes: 14 - means arranged for determining a pressure Pgæ of the fuel inthe gaseous state; - means arranged for comparing the pressure Pgæ of the fuel inthe gaseous state with a second pressure threshold P¿¿h, thesecond pressure threshold P¿¿h being related to a maximallyallowed pressure Pgæ¿wX for the tank; and - means arranged for controlling, if the pressure Pgæ ishigher than the second pressure threshold P¿¿h; Pgæ > P¿¿h;fuel flows through one or more of the at least one gaseousfuel output conduit and the at least one liquid fuel outputconduit such that only the fuel in the gaseous state is provided to the engine.

According to an embodiment of the present invention, thecontrol unit further includes means for determining the secondpressure threshold P¿¿h based at least on one or more in thegroup of: - a required volume of the fuel in the gaseous state in thetank; - a type of vehicle including the fuel tank and the engine; - a usage of a vehicle including the fuel tank and the engine;- at least one feature of the fuel tank; - a level of fuel in the fuel tank; - a relation between amounts of the fuel in the gaseous stateand the fuel in the liquid state in the fuel tank; - a temperature in the fuel tank; - an ambient temperature outside the fuel tank; and - at least one requirement related to a full tank parking time period for a vehicle including the fuel tank and the engine.

According to an embodiment of the present invention, thecontrol unit further includes means arranged for determiningthe maximal liquid torque Tmﬂ_Uq when the engine runs, based on a performance of the engine.

According to an embodiment of the present invention, thecontrol unit further includes means arranged for storinginformation related to the controlling of the fluid flows, andmeans arranged for utilizing the information together with theperformance of the engine resulting from the controlling in the adaptive determination of the maximal liquid torque Tmﬂínq.

According to an embodiment of the present invention, thecontrol unit includes means arranged for actively adjusting avalue of the maximal liquid torque Tmm¿uq, and means arrangedfor adaptive determining the maximal liquid torque Tmﬂínq basedon the active adjustment and on a performance of the engineresulting from the active adjustment of the maximal liquid torque Tmax_liq .

According to an embodiment of the present invention, thecontrol unit further includes means arranged for determiningthe maximal liquid torque TmM_hq by running a test enginecorresponding to the engine on the fuel in the liquid state in a test cell and measuring a resulting torque Tnq¿e¶.

According to an embodiment of the present invention, thecontrol unit further includes means arranged for determiningthe maximal liquid torque TMﬂ_Uq by: - determining a tendency for engine knocking when the fuel inthe liquid state is provided to the engine; and - determining the maximal liquid torque Tmw_hq based on the determined tendency for engine knocking.

The object is also achieved by the above-mentioned computer program and computer-readable medium.

Detailed exemplary embodiments and advantages of the method,control unit, computer program and computer-readable medium according to the invention will below be described with 16 reference to the appended drawings illustrating some preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention are described in more detail withreference to attached drawings illustrating examples of embodi- ments of the invention in which: Figure 1 is a schematic illustration of a non-limiting exampleof a vehicle in which the embodiments of the present invention may be implemented, Figure 2 is a schematic illustration of a fuel providingsystem, in which the embodiments of the present invention may be implemented, Figures 3a-b show a conventional economizer and valves thatmay be used according to some embodiments of the present invention, respectively, Figure 4 shows a flow chart diagram for some embodiments of the present invention, Figure 5 schematically illustrates various pressures andactions made according to some embodiments of the present invention, and Figure 6 is a schematic illustration of a control unit according to some embodiments of the present invention.

DETAILED DESCRIPTION OF INVENTION Figure 1 schematically shows an example vehicle 100, such as atruck, a bus, a car, or another suitable vehicle, which willbe used to explain the present invention. The presentinvention is, however, not limited to use in heavy goods vehicles as the one shown in figure 1, but may also be used in 17 essentially any vehicle, such as lighter vehicles, e.g. pâSSGngGI CäIS .

The vehicle 100, shown schematically in figure 1, comprises anengine 101, which may comprise a combustion engine, forexample an engine consuming liquified natural gas (LNG), inorder to create a torque being provided for driving thevehicle, e.g. an engine working according to the diesel cycle,or an engine working according to the Otto cycle for which anelectric spark ignites a fuel and air mixture in the enginecylinders. Essentially, the engine 101 may in this documentcomprise any device which transforms chemical energy tomechanical energy, and uses gaseous and liquid state fuel forits combustion. The engine then provides energy in form of atorque to the powertrain. Exhaust gases produced by the engine101 are purified by an exhaust treatment system 150. Thevehicle may also comprise one or more other power sources,such as e.g. an electrical machine, as is understood by a skilled person.

The engine 101 may, for example, in a customary fashion, viaan output shaft 102 of the engine 101, be connected with agearbox 103, via a clutch 106 and an input shaft 109 connectedto the gearbox 103. An output shaft 107 from the gearbox 103,also known as a propeller shaft, drives the driving wheels110, 111 via a final gear 108, such as e.g. a customarydifferential, and drive shafts 104, 105 connected with the final gear 108.

A fuel providing system 120, including at least onepressurized fuel tank 121, is arranged for providing theengine 101 with fuel. The fuel providing system 120 is described more in detail below. 18 A control unit 140 is in figure 1 schematically illustrated asreceiving signals and/or providing control signals from and/orto the engine 101 and/or the pressurized fuel tank 121. Thecontrol unit 140 may also receive and/or provide controlsignals to and/or from other devices in the vehicle 100.According to some embodiments of the present invention, asdescribed in this document, the control unit 140 may alsocomprise first determining means 141, e.g. a firstdetermination unit 141, second determining means 142, e.g. asecond determination unit 142, comparison means 143, e.g. acomparison unit 143, and control means 144, e.g. a controlunit 144. These control means/units/devices 141, 142, 143, 144are described more in detail below, and may be dividedphysically into more than the herein described controlmeans/systems/units 140, or may be arranged in less control systems/units than herein described.

As mentioned above, and as schematically illustrated in figure2, the fuel used for the combustion in the engine 101 may forexample include gaseous 125 and liquid 126 state fuel, such ase.g. states of a liquified natural gas (LNG). Such gaseous andliquid state fuel is stored in a fuel tank 121, which often isa pressurized fuel tank. The fuel tank includes a gaseous fueloutput conduit 122 in contact with the gaseous state fuel 125,and a liquid fuel output conduit 123 in contact with theliquid state fuel 126. Liquid state fuel 126 may therefore beprovided to the engine through the liquid fuel output conduit123, and gaseous state fuel 125 may be provided to the enginethrough the gaseous fuel output conduit 122. The tank 121 mayinclude the above-mentioned safety valve 124 arranged foropening the valve 124 if the gaseous pressures Pgæ reaches themaximal gas pressure threshold Pgæ¿wX. Hereby, the gaseous state fuel is allowed to pass out into the ambient air outside 19 of the system/vehicle, which efficiently limits/reduces the gaseous pressure Pgæ.

Conventional fuel providing systems 120 have been equippedwith a mechanical economizer, schematically illustrated infigure 3a, arranged to switch between connecting either thegaseous fuel output conduit 122 or the liquid fuel outputconduit 123 to the engine, e.g. via a fuel arrangement 128,such as pipe and/or a tube. The conventional mechanical economizer has the above-mentioned drawbacks/disadvantages.

The present invention, and its embodiments, may insteadutilize an electronically controlled economizer 127schematically illustrated in figure 3b. The electronicallycontrolled economizer 127 includes at least one controllablevalve 129 arranged in at least one of the gaseous fuel outputconduit 122 and the liquid fuel output conduit 123. Forexample, one such electronically controllable valve 129 may bearranged at each one of the the gaseous fuel output conduit122 and the liquid fuel output conduit 123. By usage of theelectronically controlled economizer 127, the portions/ratiosof gaseous 125 and liquid 126 state fuel to be provide to theengine, e.g. via a fuel arrangement 128, may easily beachieved. Thus, by usage of the electronically controlledeconomizer 127, it is not only possible to choose to provideeither gaseous or liquid state fuel to the engine (as for theconventional mechanical economizer in figure 3a). Instead, itis possible to control the controllable at least one valve 129of the electronically controlled economizer 127 such thatessentially any combination/mixture of gaseous 125 and liquid126 state fuel is provided to the engine. Thus, essentiallyany ratio of gaseous 125 and liquid 126 fuel, and therefore also any variety of octane numbers/rates, may hereby be provided to the engine by the control of the at least one controllable valve 129.

Figure 4 shows a flow chart diagram for a method 400 accordingto an embodiment of the present invention, i.e. a method forcontrolling a state of fuel provided from a fuel tank 121 toan engine 101, wherein the fuel tank 121 is storing fuel ingaseous 125 and liquid 126 state. The tank 121 includes atleast one gaseous fuel output conduit 122 and at least one liquid fuel output conduit 123.

The method steps of figure 4 may be performed in another orderthan the order illustrated in figure 4, as long as theinformation needed for performing a step is available when the step is to be performed.

In a first step 410 of the method, e.g. performed by use of abelow described first determination unit/means 141, a maximalliquid torque Tmﬂínq being providable by the engine 101 if fuelin the liquid state 125 is provided to the engine 101 is determined.

In a second step 420 of the method, performed e.g. by use of abelow described second determination unit/means 142, arequested engine torque Tæq is determined. The requestedengine torque is a well-known parameter commonly used invehicle control systems, such as e.g. in an engine controlsystem. The requested engine torque may be determined in a number of ways known by a skilled person.

In a third step 430 of the method, performed e.g. by use of abelow described comparison unit/means 143, the requestedengine torque Tﬂﬂ is compared with the maximal liquid torque Tmm¿uq determined in the first step 410. 21 In a fourth step 440 of the method, e.g. performed by use of abelow described controlling unit/means 144, if the in thesecond step 420 determined requested engine torque Tæq ishigher than the in the first step 410 determined maximalliquid torque TMm¿uq; Tnﬂ > TMm¿uq; then fuel flows through oneor more of the at least one gaseous fuel output conduit 122and the at least one liquid fuel output conduit 123 arecontrolled such that only the fuel in the gaseous state 125 isprovided to the engine 101.

By usage of the present invention, the valuable gaseous statefuel 125, having a higher octane number/rate, may be saved forsituations when it is really needed, i.e. for intelligentusage in situations when a requested engine torque Tæq is sohigh that it cannot be provided by usage of liquid state fuel.Thus, the higher octane number gaseous state fuel 125 may besaved for usage in e.g. uphill and/or acceleration situationswhen the present invention is used. This is a greatimprovement over the conventional mechanical economizer, which performed switching only based on the gas pressure Pgæ.

Thus, the choice of the state of the fuel to be provided tothe engine may, by usage of the present invention, be coupledto the usage of the vehicle, e.g. to an operational point ofthe vehicle and/or to a driving situation, which makes itpossible to optimize the state of the fuel and/or the ratiobetween gaseous and liquid states of the fuel being providedto the engine. Hereby, the torque being providable by the engine may also be adapted to the usage of the vehicle.

Also, the present invention facilitates a reliable andaccurate control of the controllable electronic economizer,such that gas pressures Pgæ closer to the maximal gas pressure threshold Pgæ¿wX may safely be utilized, which enables that 22 higher torques may be provided by the engine, since moregaseous state fuel (having higher octane number/rate) will be available for being provided to the engine 101.

Figure 5 illustrates some pressures and actions taken undercertain conditions in various pressure regions. According toan embodiment, the above mentioned fourth step 440 includes afurther step 245 of controlling the fuel flows through one ormore of the at least one gaseous fuel output conduit 122 andthe at least one liquid fuel output conduit 123 such that thefuel provided to the engine 101 includes a majority, i.e. >50%, of the fuel in the liquid state 126 if the requestedengine torque Tæq is lower than or equal to the maximal liquid tO-'fque Tmaxíliqr' Treq í Tmax_liq- In the middle of figure 5, the method steps 440 and 445 areillustrated as taken within a gas pressure Pgæ intervalbetween a first pressure threshold P¿¿h and a second pressurethreshold P¿¿h. The first pressure threshold P¿¿h is hererelated to, may e.g. be corresponding/equal to the abovementioned minimum gas pressure Pgæ¿mn needed for pushing thefuel out from the tank 121; P¿¿h= Pgæ¿mn; and may as a non-limiting example have a value corresponding to a gas pressurePgæ of 10 bar; P¿¿h = 10 bar. The second pressure thresholdP¿ﬂ1may indicate a pressure over which an amount of thegaseous state fuel 125 in the tank 121 needs to be reduced inorder to avoid that the pressure Pgæ of the gaseous state fuel125 reaches the maximally allowed pressure Pgæ¿wX for the tank,which would trigger an opening of the safety valve 124. Thus,the second pressure threshold P¿¿h is related to the maximallyallowed gas pressure Pgæ¿wX for the tank 121, and may as a non-limiting example correspond to a gas pressure Pgæ of 18 bar;P¿¿h = 18 bar. The maximally allowed pressure Pgæ¿wX may as a non-limiting example correspond to a gas pressure Pgæ of 20 23 bar; Pgæ¿mX = 20 bar. Thus, there may be a safety margin/offsetPgæ_üfæt; of e.g. 2 bar between the maximally allowed pressureP¶ß¿wX and the second pressure threshold P¿¿h; Pgæ_Mfæt = P¶ß¿mX - Pgíth = 2 bar.

According to an embodiment of the present invention, when thegas pressure Pgæ is within the above-mentioned pressureinterval P¿¿h - P¿¿h, various levels of requested torque resultin various fuel state mixtures, such as 100% fuel in thegaseous state, a mixture of the fuel in the gaseous state and in the liquid state, or 100% fuel in the liquid state.

A couple of non-limiting examples of fuel state ratios aregiven in the following. One or more of such examples ratiosmay, according to an embodiment of the present invention, beutilized as initial values for one or more of the embodiments of fuel state control described in this document.

According to a control algorithm, if the requested enginetorque Tnﬂ is higher than the maximal liquid torque TMm¿uq; Tæq> TMm¿mq; then 100% fuel in gaseous state 125, i.e. 0% fuel in liquid state 126, may be provided to the engine 101.

According to a control algorithm, if the requested enginetorque Tæq is lower than or equal to the maximal liquid torqueTMm¿uq; Tnﬂ S TMm¿Mq; then 100% fuel in liquid state 126, i.e.0% fuel in gaseous state 125, may be provided to the engine 101.

According to a control algorithm, if the requested enginetorque Tæq is higher than 110% of the maximal liquid torqueTMm¿uq; Tnﬂ > 1.1*TMm¿uq; then 100% fuel in gaseous state 125,i.e. 0% fuel in liquid state 126, may be provided to the engine 101. 24 According to a control algorithm, if the requested enginetorque Tæq is in an interval between 80% and 110% of themaximal liquid torque Tmax_liq; 0.8*Tmaxíliq < Treq < 1.1*TmaX_liq;then a mixture of fuel in gaseous state 125 and liquid state 126 may be provided to the engine.

According to a control algorithm, if the requested enginetorque Tæq is higher than 90% of the maximal liquid torqueTMM¿uq; Tnﬂ > 0.9*Tmm¿uq; then 100% fuel in gaseous state 125,i.e. 0% fuel in liquid state 126, may be provided to the engine 101.

According to a control algorithm, if the requested enginetorque Tæq is in an interval between 80% and 90% of themaximal liquid torque Tmax_liq; 0.8*Tmaxíliq < Treq < 0.9*Tmax_liq;then a mixture of fuel in gaseous state 125 and liquid state 126 may be provided to the engine.

According to a control algorithm, if the requested enginetorque Tæq iS lower than or equal to 80% of the maximal liquidtorque TMm¿Mq; Tnﬂ S 0.8*TMﬂ¿uq; then 100% fuel in liquid state 126 may be provided to the engine 101.

According to an embodiment of the present invention, themethod 400 illustrated in figure 4 further includes a fifthstep 450 of determining a pressure Pgæ of the fuel in thegaseous state 125. The gas pressure P%w may e.g. be determinedby usage of one or more sensors. The one or more sensors maybe arranged at/within the tank 121 and/or at/within the at least one gaseous state fuel output conduit 122.

The method 400 may also include a sixth step 460 of comparingthe determined pressure Pgæ of the fuel in the gaseous state125 with the first pressure threshold P¿¿h. As mentioned above, the first pressure threshold P¿¿h may here indicate a pressure needed for providing the fuel flows through one or more of theat least one gaseous fuel output conduit 122 and the at leastone liquid fuel output conduit 123, i.e. for providing the fuel to the engine.

The method may also include a seventh step 470 of controlling,if the determined pressure Pgæ is lower than the firstpressure threshold P¿¿h; Pgæ < P¿¿h; fuel flows through one ormore of the at least one gaseous fuel output conduit 122 andthe at least one liquid fuel output conduit 123 such that onlyfuel in liquid state 125 is provided to the engine 101. Asmentioned above, the control 470 may be achieved by use of oneor more flow controlling arrangements, including e.g. one ormore valves mounted in and/or at one or more of the at leastone gaseous fuel output conduit 122 and the at least oneliquid fuel output conduit 123, i.e. by the use of theelectrically controlled economizer 127. According to anembodiment, for which P¿¿h = Pgæ¿mn, the control step 470 isthus performed if Pgæ < Pgæ¿mn. The control step 470 is illustrated at the bottom of figure 5.

As is illustrated in figure 4, the method 400 may according toan embodiment, any time after the fifth step 450 ofdetermining the gas pressure Pgæ, include an eighth step 480of comparing the determined pressure Pgæ of the gaseous statefuel 125 with the second pressure threshold P¿¿h. As mentionedabove, the second pressure threshold P¿¿h is related to amaximally allowed pressure Pgæ¿wX for the tank 121, at which the safety valve 124 opens.

The method 400 may, according to an embodiment, also include aninth step 490 of controlling, if the determined gas pressurePgæ is higher than the pressure threshold P¿¿h; Pgæ > P¿¿h; fuel flows through one or more of the at least one gaseous 26 fuel output conduit 122 and the at least one liquid fueloutput conduit 123 such that only gaseous state fuel 125 isprovided to the engine 101. As mentioned above, the control490 may be achieved by use of one or more flow controllingarrangements, including e.g. one or more valves mounted inand/or at one or more of the at least one gaseous fuel outputconduit 122 and the at least one liquid fuel output conduit123, i.e. by the use of the electrically controlled economizer 127. The control 490 is illustrated at the top of figure 5.

Thus, as is illustrated in figure 5, according to variousembodiments of the present invention, depending on thevalue/level of the gas pressure Pgæ and/or depending on therequested torque, the electrically controlled economizer 127is controlled for providing liquid state fuel 126, gaseousstate fuel 125 or a mixture of gaseous and liquid state fuelto the engine. Hereby, a very exact control of the fuel beingprovided to the engine is achieved for a large variety ofvehicle uses and/or engine operational modes. A very exact andreliable control of the engine and its provided torque mayhereby be achieved. Also, the fuel consumption is reduced since the safety valve may be opened less often.

As illustrated in figure 5, according to the embodiments ofthe present invention, a pressure region P¿¿h - P¿¿h betweenthe first pressure threshold P¿¿h and the second pressurethreshold P¿¿h is defined, in which the electronic controllableeconomizer 127 may be controlled in relation to the requestedengine torque TBH. This pressure region P¿¿h - P¿¿h does noteven exist for a conventional mechanical economizer, since theconventional mechanical economizer switches only based on the pressure. 27 The pressure region P¿¿h - P¿¿h created by the embodiments ofthe present invention may, as is mentioned above, be utilizedfor a more accurately control the state of fuel being providedto the engine. Hereby, a more efficient usage of the gaseousstate fuel, and thereby also a more powerful engine whenneeded, may be achieved. Also, the more exact and reliablecontrol of the state of fuel being provided to the enginereduces the need for opening the safety valve 124, which lowers the fuel consumption over time.

The first pressure threshold P¿¿h, which is utilized in variousembodiments of the present invention, may be determined in anumber of ways. According to an embodiment, the first pressurethreshold P¿¿h is determined based on at least one feature ofthe fuel tank 121, such as for example a size, a geometricaldesign and/or an output conduit design for the fuel tank 121.According to an embodiment, the first pressure threshold P¿¿his determined based on at least one feature of a fuelproviding system 120 arranged for providing the fuel from thetank 121 to the engine 101, wherein such system features mayinclude geometrical forms and/or dimensions for piping betweenthe tank 121 and the engine 101 and/or for a (common) fuelrail providing pressurized fuel to the injectors arranged for injecting fuel into the engine.

The second pressure threshold P2¿m, which is also utilized invarious embodiments of the present invention, may bedetermined in a number of ways. According to an embodiment, the second pressure threshold P¿¿h may be determined based on arequired volume of the gaseous state fuel 125 in the tank 121and/or on the type and/or usage of the vehicle 100. Forexample, a bus or a garbage truck, i.e. vehicles oftenmoving/driving short distances between its stops, may have a lower/smaller value for the second pressure threshold P2¿m, 28 whereas e.g. long haulage trucks, i.e. vehicles driving/movinglonger distances between its stops, may have a higher/greatervalue for the second pressure threshold P2¿m. Further,according to an embodiment, the second pressure threshold P¿¿hmay be determined based on at least one feature of the fueltank 121, a level of fuel in the fuel tank 121, a relationbetween amounts of the gaseous state 125 and liquid state 126fuel in the fuel tank 121, a temperature in the fuel tank 121,an ambient temperature outside the fuel tank/system/vehicle,and/or at least one requirement related to a full tank parkingtime period for the vehicle 100 including the fuel tank 121.Generally, the gas pressure Pgæ in the fuel tank 121 slowlyincreases over time if the vehicle is standing still with theengine off/not running. If the gaseous state fuel is notconsumed, the gas pressure Pgæ will after some time reachdangerous gas pressure Pgæ levels, e.g. at 20 bar, whereforethe safety valve 124 is arranged to open, in order to mitigatefurther increase of the gas pressure Pgæ in the fuel tank. Invarious regions, there is legislation and/or rules definedthat specify a time period during which a full tanked vehicleshould manage to stand still, i.e. to be parked, without having to open the safety valve 124.

As is mentioned above, the maximal liquid torque TMm¿uq is usedin various embodiments of the present invention. The maximalliquid torque Tmüínq may, according to an embodiment, bedetermined 410 adaptively during normal operation of thevehicle, i.e. when the engine 101 runs. The determination 410of the maximal liquid torque TMm¿uq is then based on aperformance of the engine 101. For example, informationrelated to the controlling 440 of the fluid flows, i.e. control of the electrically controlled economizer 127, is stored and is utilized, together with the determined 29 performance of the engine 101 resulting from the controlledflows, i.e. resulting from the control of the economizer, forthe adaptive determination 410 of the maximal liquid torqueTMM¿uq. A value of the maximal liquid torque TMﬂ_hq may herefor example be actively adjusted, and thereafter the maximalliquid torque TMX¿uq is adaptively determined 410 based on thatmade active adjustment and on a determined performance of theengine 101 resulting from the active adjustment of the maximalliquid torque TMm¿uq. In other words, a change/adjustment ofthe maximal liquid torque Tmm¿uq is here first activelyeffected, and thereafter the effect of this change/adjustmentis analyzed. The analysis is then possibly followed by another adjustment/change of the maximal liquid torque Tmw_nq.

According to an embodiment, the maximal liquid torque TMm¿uq isdetermined 410 by first determining a tendency for engineknocking when the fuel in the liquid state is provided to theengine, e.g. based on information provided by one or moreknocking sensors, which may be acoustic sensors arranged atthe engine 101, and/or based on a knowledge of the octanenumber of the fuel provided to the engine. When the tendencyfor engine knocking has been determined, the maximal liquidtorque Tmwínq may be determined based on the determinedtendency, e.g. by, if knocking is detected, adjusting theignition, and thereby also adjusting the providable torque,until the knocking stops. The maximal liquid torque TMM¿Mq isthen determined as the torque providable without engine knocking occurring.

Correspondingly, the maximal gaseous torque Tmm¿WS is,according to an embodiment, determined 410 by firstdetermining a tendency for engine knocking when the fuel inthe gaseous state is provided to the engine, e.g. by usage of the above mentioned one or more knocking sensors and/or based on the octane number of the fuel provided to the engine. Whenthe tendency for engine knocking has been determined, thegaseous torque Tmﬂ¿%S may be determined based on the determinedtendency, by adjusting the ignition until the knocking stops,as mentioned above. The gaseous torque Tmw¿%S is thendetermined as the torque providable without engine knocking occurring.

The determination of the maximal gaseous torque Tmw¿%S and/orthe maximal liquid torque Tmﬂínq providable by the engine 101may, according to an embodiment, be performed by running atest engine corresponding to the engine 101 in the vehicle 100e.g. in a test cell/laboratory environment, and measuringresulting gaseous and/or liquid test torques Tgæ_U%t, Thq¿æSt.The maximal gaseous and/or liquid torques TMﬂ¿mS, TMX¿uq arethen determined based on the respective gaseous and/or liquid test torques Tgas_testr Tliq_test- A person skilled in the art will appreciate that theembodiments of the method for controlling a state of fuelprovided from a fuel tank 121 to an engine 101, according tothe present invention, may also be implemented in a computerprogram, which, when it is executed in a computer, instructsthe computer to execute the method. The computer may beincluded in the herein described system and/or may becoupled/connected to the herein described system. The computerprogram is usually constituted by a computer program product603 stored on a non-transitory/non-volatile digital storagemedium, in which the computer program is incorporated in thecomputer-readable medium of the computer program product. Thecomputer-readable medium comprises a suitable memory, such as,for example: ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), Flash memory, EEPROM(Electrically Erasable PROM), a hard disk unit, etc. 31 Figure 6 shows in schematic representation a controlunit/system/means 600/140. The control unit/system/means600/140 comprises a computing unit 601, which may beconstituted by essentially any suitable type of processor ormicrocomputer, for example a circuit for digital signalprocessing (Digital Signal Processor, DSP), or a circuithaving a predetermined specific function (Application SpecificIntegrated Circuit, ASIC). The computing unit 601 is connectedto a memory unit 602 arranged in the control unit/system/means600/140, which memory unit provides the computing unit 601with, for example, the stored program code and/or the storeddata which the computing unit 601 requires to be able toperform computations. The computing unit 601 is also arrangedto store partial or final results of computations in the memory unit 602.

In addition, the control unit/system/means 600/140 is providedwith devices 611, 612, 613, 614 for receiving and transmittinginput and output signals. These input and output signals maycomprise waveforms, impulses, or other attributes which, bythe devices 611, 613 for the reception of input signals, canbe detected as information and can be converted into signalswhich can be processed by the computing unit 601. Thesesignals are then made available to the computing unit 601. Thedevices 612, 614 for the transmission of output signals arearranged to convert signals received from the computing unit601 in order to create output signals by, for example,modulating the signals, which can be transmitted to other parts of and/or systems within or outside the vehicle.

Each of the connections to the devices for receiving andtransmitting input and output signals can be comprise one ormore of a cable; a data bus, such as a CAN bus (Controller Area Network bus), a MOST bus (Media Orientated 32 Systems Transport bus), or some other bus configuration; or bya wireless connection. A person skilled in the art willappreciate that the above-stated computer can be constitutedby the computing unit 601 and that the above- stated memorymay be constituted by the memory unit 602.

Control systems in modern vehicles commonly comprisecommunication bus systems including one or more communication buses for linking a number of electronic controlunits (ECU's), or controllers, and various components locatedon the vehicle. Such a control system may comprise a largenumber of control units/means and the responsibility for aspecific function can be divided amongst more than one controlunit/means. Vehicles of the shown type thus often comprisesignificantly more control units/means than are shown infigures 1, 2 and 6, which is well known to the person skilled in the art within this technical field.

In the shown embodiment, the present invention is implementedin the control unit/system/means 600/140. The invention canalso, however, be implemented wholly or partially in one ormore other control units/systems/means already present in thevehicle, or in some control unit/system/means dedicated to the present invention.

According to an aspect of the invention, a control unit 140arranged for controlling a state of fuel provided from a fueltank 121 to an engine 101 of a vehicle 100 is presented. Asmentioned above, the fuel tank 121 stores fuel in gaseous 125and liquid 126 state, and includes at least one gaseous fueloutput conduit 122 and at least one liquid fuel output conduit 123.

The control unit 140 includes a first determination unit/means 141, arranged for determining 410 a maximal liquid torque 33 Tmﬂíhq being providable by the engine 101 if fuel in the liquid state 126 is provided to the engine 101, as described above.

The control unit 140 further includes a second determinationunit/means 142, arranged for determining 420 a requested engine torque Tum, as described above.

The control unit 140 also includes a comparison unit/means143, arranged for comparing 430 the requested engine torque Tæq with the maximal liquid torque Tmm¿uq, as described above.

The control unit 140 also includes a controlling unit/means144, arranged for controlling 440, if the requested enginetorque Tnﬂ is higher than the maximal liquid torque TmM¿uq; Tæq> TMm¿mq; fuel flows through one or more of the at least onegaseous fuel output conduit 122 and the at least one liquidfuel output conduit 123 such that only gaseous state fuel 125 is provided to the engine 101, as described above.

By activation of the above described first determinationunit/means 141, the second determination unit/means 142, thecomparison unit/means 143, and the controlling unit/means 144,the above described method is performed, which has the above- mentioned advantages.

Here and in this document, units/means are often described asbeing arranged for performing steps of the method according tothe invention. This also includes that the units/means are designed to and/or configured to perform these method steps.

The at least one control unit 140 is in figures 1 and 2illustrated as including separately illustrated units/means141, 142, 143, 144. Also, the control system/means 140 mayinclude or be coupled to other control means/units, such ase.g. an engine control device/means, a clutch control unit, an exhaust treatment system control unit, and/or a gearbox 34 control unit. These means/units/devices 141, 142, 143, 144,140 may, however, be at least to some extent logicallyseparated but implemented in the same physical unit/device.These means/units/devices 141, 142, 143, 144, 140 may also bepart of a single logic unit which is implemented in at leasttwo different physical units/devices. Thesemeans/units/devices 141, 142, 143, 144, 140 may also be atleast to some extent logically separated and implemented in atleast two different physical means/units/devices. Further,these means/units/devices 141, 142, 143, 144, 140 may be bothlogically and physically arranged together, i.e. be part of asingle logic unit which is implemented in a single physicalmeans/unit/device. These means/units/devices 141, 142, 143,144, 140 may for example correspond to groups of instructions,which can be in the form of programming code, that are inputinto, and are utilized by at least one processor when theunits/means are active and/or are utilized for performing itsmethod step, respectively. It should be noted that the controlunit/means 140 may be implemented at least partly within thevehicle 100 and/or at least partly outside of the vehicle 100,e.g. in a server, computer, processor or the like located separately from the vehicle 100.

As mentioned above, the units 141, 142, 143, 144 describedabove correspond to the claimed means 141, 142, 143, 144arranged for performing the embodiments of the present invention, and the present invention as such.

The control unit 140 according to the present invention can bearranged for performing all of the above, in the claims, andin the herein described embodiments method steps. The controlunit is hereby provided with the above described advantages for each respective embodiment.

A skilled person also realizes that the above describedcontrol unit may be modified according to the differentembodiments of the method of the present invention. Thepresent invention is also related to a vehicle 100, such as atruck, a bus or a car, including the herein described control unit 140.

The inventive method, and embodiments thereof, as describedabove, may at least in part be performed with/using/by atleast one device. The inventive method, and embodimentsthereof, as described above, may be performed at least in partwith/using/by at least one device that is suitable and/oradapted for performing at least parts of the inventive methodand/or embodiments thereof. A device that is suitable and/oradapted for performing at least parts of the inventive methodand/or embodiments thereof may be one, or several, of acontrol unit, an electronic control unit (ECU), an electroniccircuit, a computer, a computing unit and/or a processing unit.

With reference to the above, the inventive method, andembodiments thereof, as described above, may be referred to asan, at least in part, computerized method. The method being,at least in part, computerized meaning that it is performed atleast in part with/using/by the at least one device that issuitable and/or adapted for performing at least parts of the inventive method and/or embodiments thereof.

With reference to the above, the inventive method, andembodiments thereof, as described above, may be referred to asan, at least in part, automated method. The method being, atleast in part, automated meaning that it is performed with/using/by the at least one device that is suitable and/or 36 adapted for performing at least parts of the inventive method and/or embodiments thereof.

The present invention is not limited to the above describedembodiments. Instead, the present invention relates to, andencompasses all different embodiments being included within the scope of the independent claims.

Claims

1. A method (400) for controlling a state of fuelprovided from a fuel tank (121) to an engine (101), said fueltank (121) storing fuel in gaseous (125) and liquid (126)state, and including at least one gaseous fuel output conduit(122) and at least one liquid fuel output conduit (123); themethod comprising - determining (410) a maximal liquid torque Tmw_Uq beingprovidable by said engine (101) if fuel in said liquid state(125) is provided to said engine (101); - determining (420) a requested engine torque Tæq; - comparing (430) said requested engine torque Tnﬂ with saidmaximal liquid torque Tmm¿uq; and - controlling (440), if said requested engine torque Tæq ishigher than said maximal liquid torque Tmﬂ¿mq; Tæq > TMM¿mq;fuel flows through one or more of said at least one gaseousfuel output conduit (122) and said at least one liquid fueloutput conduit (123) such that only said fuel in said gaseous state (125) is provided to said engine (101) characterized by - determining (450) a pressure Pgæ of said fuel in saidgaseous state (125); - comparing (460) said pressure Pgæ of said fuel in saidgaseous state (125) with a first pressure threshold P¿¿h, saidfirst pressure threshold P¿¿h being related to a pressurePgæ¿mn needed for providing said fuel flows through one or moreof said at least one gaseous fuel output conduit (122) andsaid at least one liquid fuel output conduit (123); and - controlling (470), if said pressure Pgæ is lower than saidfirst pressure threshold P¿¿h; Pgæ < P¿¿h ; fuel flows throughone or more of said at least one gaseous fuel output conduit (122) and said at least one liquid fuel output conduit (123) such that only said fuel in said liquid state (125) is provided to said engine (101).T

2. The method (400) as claimed in claim 1, furtherincluding: - controlling (445) fuel flows through one or more of said atleast one gaseous fuel output conduit (122) and said at leastone liquid fuel output conduit (123) such that said fuelprovided to said engine (101) includes a majority of said fuelin said liquid state (126) if said requested engine torque Tæqis lower than or equal to said maximal liquid torque Tmm_nq; Treq í Tmax_liq-

3. The method (400) as claimed in any one of claims 1-2,wherein said fuel provided to said engine (101) includes onein the group of: - 100% fuel in said gaseous state (125); - a mixture of said fuel in said gaseous state (125) and insaid liquid state (126); and - 100% fuel in said liquid state (126).

4. The method (400) as claimed in claim 3, wherein saidfirst pressure threshold P¿¿h is determined based at least onone or more in the group of: - at least one feature of said fuel tank (121); and - at least one feature of a fuel providing system (120)arranged for providing said fuel from said tank (121) to said engine (101).

5. The method (400) as claimed in any one of claims 1-4,further including: - determining (450) a pressure Pgæ of said fuel in saidgaseous state (125); - comparing (480) said pressure Pgæ of said fuel in said gaseous state (125) with a second pressure threshold P¿¿h, said second pressure threshold P¿¿h being related to a maximallyallowed pressure Pgæ¿mX for said tank (121); and - controlling (490), if said pressure Pgæ is higher than saidsecond pressure threshold P¿¿h; Pgæ > P¿¿h; fuel flows throughone or more of said at least one gaseous fuel output conduit(122) and said at least one liquid fuel output conduit (123)such that only said fuel in said gaseous state (125) is provided to said engine (101).

6. The method (400) as claimed in claim 5, wherein saidsecond pressure threshold P¿¿h is determined based at least onone or more in the group of: - a required volume of said fuel in said gaseous state (125)in said tank (121); - a type of vehicle (100) including said fuel tank (121) andsaid engine (101); - a usage of a vehicle (100) including said fuel tank (121)and said engine (101); - at least one feature of said fuel tank (121); - a level of fuel in said fuel tank (121); - a relation between amounts of said fuel in said gaseousstate (125) and said fuel in said liquid state (126) in saidfuel tank (121); - a temperature in said fuel tank (121); - an ambient temperature outside said fuel tank (121); and - at least one requirement related to a full tank parking timeperiod for a vehicle (100) including said fuel tank (121) and said engine (101).

7. The method (400) as claimed in any one of claims 1-6,wherein said maximal liquid torque TMm¿uq is determined (410)adaptively when said engine (101) runs, and is based on a performance of said engine (101).

8. The method (400) as claimed in claim 7, whereininformation related to said controlling (440) of said fluidflows is stored and utilized together with said performance ofsaid engine (101) resulting from said controlling (440) for the adaptive determination (410) of said maximal liquid torque Tmax_liq -

9. The method (400) as claimed in claim 7, wherein avalue of said maximal liquid torque Tmﬂ¿uq is activelyadjusted, and said adaptive determination (410) of saidmaximal liquid torque Tmm¿uq is based on the active adjustmentand on a performance of said engine (101) resulting from the active adjustment of said maximal liquid torque Tmﬂínq.

10. The method (400) as claimed in any one of claims 1-6,wherein said maximal liquid torque TMX¿uq is determined (410)by running a test engine corresponding to said engine (101) onsaid fuel in said liquid state (126) in a test cell and measuring a resulting torque Tnq¿e¶.

11. The method (400) as claimed in any one of claims 1-6,wherein said maximal liquid torque Tmm¿mq is determined (410)by: - determining a tendency for engine knocking when said fuel insaid liquid state (126) is provided to said engine (101); and- determining said maximal liquid torque TMM_Uq based on said determined tendency for engine knocking.

12. A computer program comprising instructions which, whenthe program is executed by a computer, cause the computer to carry out the method according to any one of claims 1-11.

13. A computer-readable medium comprising instructions which,when the program is executed by a computer, cause the computer to carry out the method according to any one of claims 1-11.

14. A control unit (140) arranged for controlling a stateof fuel provided from a fuel tank (121) to an engine (101),said fuel tank (121) storing fuel in gaseous (125) and liquid(126) state, and including at least one gaseous fuel outputconduit (122) and at least one liquid fuel output conduit(l23); eheæaeeeeæeeáeey - first means (141) arranged for determining (410) a maximalliquid torque Tmﬂ_Uq being providable by said engine (101) iffuel in said liquid state (126) is provided to said engine(101); - second means (142) arranged for determining (420) arequested engine torque Tæq; - means (143) arranged for comparing (430) said requestedengine torque Tﬂﬂ with said maximal liquid torque TMm¿uq; and- means (144) arranged for controlling (440), if saidrequested engine torque Tæq is higher than said maximal liquidtorque TMm¿uq; Tnﬂ > TMm¿Mq; fuel flows through one or more ofsaid at least one gaseous fuel output conduit (122) and saidat least one liquid fuel output conduit (123) such that onlysaid fuel in said gaseous state (125) is provided to said engine (lOl); charaoterized by ~ means arranged for determining (450) a pressure Pmß of said fuel in said gaseous state (125;; means arranged for comparing (460) said pressure fuel in said gaseous state (125) with a first W threshoid Plih, said first .ure threshold related to a pressure Pﬁaïwm needed for providino said fuelflows through one or more of said at least one gaseous fuel output conduit (122) and said at least one liquid fuel output conduit (123): and ~ means arranged for controlling (4?0), if said pressure Pqﬂis lower than said first pressure threshold P ,@; ag-< P1 ; fuel flows through one or more of said at least one gaseous output conduít ä., u) C\ and said at Û ll .:. jr said engine least Um said fuel (lOl}. fl "id fuel