SE542908C2 - Method for determining filter clogging in a fuel system, control device, vehicle, computer program and computer-readable medium - Google Patents

Abstract

A method and a control device (100) for determining filter clogging in a fuel system (7) associated with a combustion engine (2) of a vehicle (1) is provided. The determination of filter clogging is performed on the basis of a detected increase of pressure in the accumulator (12) of the injection system (11) during an engine braking mode. Moreover, a vehicle comprising such a control device, as well as a computer program and a computer-readable medium are provided.

Description

METHOD FOR DETERMINING FILTER CLOGGING IN A FUEL SYSTEM, CONTROL DEVICE, VEHICLE,COMPUTER PROGRAM AND COMPUTER-READABLE MEDIUM TECHNICAL FIELD The present disclosure relates in general to a method for determining filter clogging in a fuel systemassociated with a combustion engine of a vehicle. The present disclosure further relates in general toa control device configured to determine filter clogging in a fuel system associated with a combustionengine of a vehicle. The present disclosure also relates to a vehicle comprising such a control device, as well as a computer program and a computer-readable medium.

BACKGROUND An internal combustion engine of a vehicle is associated with a fuel system adapted to transport fuelfrom one or more fuel tanks to via an injection system of the fuel system to the internal combustionengine. The fuel system comprises one or more fuel pumps, which may be driven mechanically bythe internal combustion engine, or be driven by other means, such as by an electric motor. The fuelpumps create a fuel flow and pressure to transport the fuel to the injection system. The injection system then supplies fuel to the internal combustion engine.

The fuel system also comprises one or more filters for filtering of the fuel before it reaches theinjection system of the internal combustion engine to thereby remove contaminations.

Contaminations may be solid particles, gas or liquid.

The filter or filters of the fuel system are periodically changed in dependence of the expected lifetime of the filter/filters. However, a filter may become clogged before the end of the expected lifetime which may seriously affect the operation of the fuel system and in worst case lead to a vehicle-off-road-situation.

SUMMARY The object of the present invention is to enable an early indication of clogging of a filter in a fuel system associated with a combustion engine of a vehicle.

The object is achieved by the subject-matter of the appended independent claims. ln accordance with the present disclosure, a method for determining filter clogging in a fuel system isprovided. The fuel system is associated with a combustion engine of a vehicle. The fuel systemcomprises a fuel tank and an injection system for injecting fuel into the combustion engine. Theinjection system comprises an accumulator and one or more fuel injectors. The fuel system furthercomprises a first pump adapted to pump fuel to the accumulator, the first pump being driven by thecombustion engine. The fuel system also comprises an inlet metering valve configured to control theamount of fuel introduced into the first pump, a first fuel filter arranged upstream of the first pump,and a second pump arranged upstream of the first fuel filter. The second pump is adapted to transferfuel from the fuel tank to the first pump. The fuel system further comprises a venturi driven bypressure provided by the second pump, the venturi configured to withdraw fuel accumulateddownstream of the inlet metering valve when the inlet metering valve is closed. The fuel system mayoptionally also comprise a second fuel filter arranged between the fuel tank and the second pump.The method comprises a step of, when the vehicle is in an engine braking mode, monitoring thepressure in the accumulator. The method further comprises a step of, if an increase of pressure inthe accumulator is detected during said monitoring of the pressure in the accumulator, determining filter clogging in the fuel system.

By means of the present method, it is possible to get an early indication of filter clogging duringoperation of the vehicle. An increase in the pressure in the accumulator occurs before the pressureprovided by the second pump becomes so low that it may affect the control of the pressure in theaccumulator, which in turn could negatively affect the operation of the injection system. Therefore, itis possible to avoid a situation where filter clogging may risk causing disturbance in the operation ofthe vehicle when utilising the above described method. The method may determine filter cloggingirrespectively of whether it is the first fuel filter and/or the second fuel filter (if present) that is affected.

The increase in pressure in the accumulator during engine braking mode indicates that the first pumphas started to self-pump. Since the first pump is driven by the combustion engine and thecombustion engine is running in engine braking mode, the first pump will pump any fuel that reachesthe pumping elements of the first pump. Thus, the fact that the first pump has started to self-pumpindicates that there is a leakage of fuel into the first pump. This in turn indicates that the venturi isnot functioning as intended, which may be caused by the second pump not being able to deliver a sufficient pressure for operation of the venturi. The reason for the second pump not being able to deliver a sufficient pressure may be that there is an undesirable pressure drop over a fuel filter, which in turn may be due to clogging.

The step of determining filter clogging in the fuel system may comprise detecting an increase ofpressure in the accumulator over at least a preselected period of time. Thereby, it is avoided that thedetermination of filter clogging is based on an unexpected peak increase in pressure which may becaused by other factors than the first pump being in a self-pumping state. Thus, by detecting an increase of pressure over time, the accuracy in determining filter clogging may be improved.

The step of determining filter clogging may comprise detecting an increase of pressure in theaccumulator after a first predetermined time has lapsed since initiation of engine braking modeand/or since closure of the inlet metering valve. Closure of the inlet metering valve may be executedat the start of engine braking mode. By allowing a first predetermined time to lapse before detectingan increase of pressure, it may be ensured that the fuel present in the first pump when enginebraking mode is initiated has been transferred to the accumulator. This in turn results in a reliableindication of initial pressure before the pressure increase in the accumulator is to be detected, saidpressure increase being caused by the first pump self-pumping. This in turn may increase the accuracy in the determination of filter clogging.

The step of determining filter clogging may comprise detecting an increase of pressure in theaccumulator, wherein the increase of pressure is equal to or more than a threshold value. ln otherwords, filter clogging is determined only if the increase in pressure is equal to or more than athreshold value. Thereby, it may for example be ensured that normally occurring fluctuations inpressure are not used when determining filter clogging. Thus, the accuracy in the determination of filter clogging may be improved.

The method may further comprise a step of generating a warning signal if filter clogging has beendetermined. The warning signal may for example be generated to inform a driver, a controlarrangement of the vehicle, and/or a remote control centre of the need for replacement of fuel filter(s).

Furthermore, a control device configured to determine filter clogging in a fuel system associated witha combustion engine of a vehicle is provided. The fuel system comprises a fuel tank and an injectionsystem for injecting fuel into the combustion engine. The injection system comprises an accumulator and one or more fuel injectors. The fuel system further comprises a first pump adapted to pump fuel to the accumulator, the first pump being driven by the combustion engine. The fuel system alsocomprises an in|et metering valve configured to control the amount of fuel introduced into the firstpump, a first fuel filter arranged upstream of the first pump, and a second pump arranged upstreamof the first fuel filter. The second pump is adapted to transfer fuel from the fuel tank to the firstpump. The fuel system further comprises a venturi driven by pressure provided by the second pump,the venturi configured to withdraw fuel accumulated downstream of the in|et metering valve whenthe in|et metering valve is closed. The fuel system may optionally also comprise a second fuel filterarranged between the fuel tank and the second pump. The control device is configured to determinefilter clogging on the basis of a detection of an increase of pressure in the accumulator when thevehicle is in an engine braking mode. The control device may be configured to monitor and detect apressure and/or pressure change in the accumulator by means of a pressure sensor arranged in the accumulator.

By means of the control configured to determine filter clogging in a fuel system associated with acombustion engine of a vehicle, it is possible to get an early indication of filter clogging in the fuelsystem. The control device has the corresponding advantages as described above with regard to themethod for determining filter clogging in a fuel system associated with a combustion engine of a vehicle.

The control device may be configured to detect said increase of pressure in the accumulator over at least a preselected period of time.

The control device may further be configured to detect the increase of pressure in the accumulatorafter a first predetermined time has lapsed since initiation of engine braking mode and/or since closure of the in|et metering valve.

The control device may further be configured to determine filter clogging on the basis of a detectionon an increase of pressure in the accumulator, wherein the increase of pressure is equal to or more than a threshold value.

The present disclosure further relates to a vehicle comprising a combustion engine and a fuel systemassociated with the combustion engine. The vehicle further comprises a control device configured to determine filter clogging as described above.

The present disclosure further relates to a computer program, wherein said computer programcomprises program code for causing a control device to perform the method for determining filter clogging as described above.

The present disclosure further relates to a computer-readable medium comprising instructions, which when executed by a control device, cause the control device to perform the method for determining filter clogging as described above.

BREIF DESCRIPTION OF DRAWINGS Fig. 1 schematically illustrates a side view of an example of a vehicle, Fig. 2 schematically illustrates one exemplifying embodiment of fuel system, Fig. 3 schematically illustrates the ability of the venturi to create a negative pressure as a functionof feed pressure provided by a second pump of a fuel system illustrated in Fig. 2, Fig. 4 schematically illustrates change in accumulator pressure and feed pressure, respectively,over time during engine braking when the first pump of a fuel system, such as a fuel systemas shown in Fig. 2, starts to self-pump, Fig. 5 represents a flowchart schematically illustrating a method for determining filter clogging inaccordance with the present disclosure, Fig. 6 schematically illustrates a device that may constitute, comprise or be a part of a control device configured to control a steering system of a vehicle.

DETAILED DESCRIPTION The invention will be described in more detail below with reference to exemplifying embodimentsand the accompanying drawings. The invention is however not limited to the exemplifying embodiments discussed and/or shown in the drawings, but may be varied within the scope of the appended claims. Furthermore, the drawings shall not be considered drawn to scale as some features may be exaggerated in order to more clearly illustrate the invention or features thereof. ln the present disclosure, the term ”filter clogging" shall be interpreted broadly. Thus, ”filterclogging" encompasses a complete clogging of a filter as well as a partial clogging of a filter, unlessexplicitly disclosed otherwise. lt is common general knowledge that filter clogging leads to an increase of the pressure drop over the filter.

Furthermore, in the present disclosure, the term "determining filter clogging" shall be consideredbroadly. lt shall thus be considered to encompass for example deciding that filter clogging isconsidered to have occurred (on the basis of one or more parameters on which the "determination" is made). ln the present disclosure, an ”engine braking mode” shall be considered to constitute an operatingcondition of a vehicle in which the vehicle powertrain is closed, i.e. the combustion engine isconnected to the driving wheel(s) of the vehicle, but there is no fuel injection to the combustionengine. During engine braking mode, the vehicle is travelling. Since the powertrain is closed duringthe engine braking mode, the crankshaft of the combustion engine will be rotating and thus has arotational speed. Thus, a component or device which in the present disclosure is described as beingdriven by the combustion engine may also be operational during an engine braking mode, unless explicitly disclosed otherwise.

Furthermore, in the present disclosure, the term "powertrain" shall be considered to mean the combustion engine and the driveline of the vehicle.

Moreover, when the term "self-pumping" or similar expressions are used in the present disclosure, itis intended to mean an unintentional pumping which inherently occurs due to certain factors. These factors are explained in more detail in the following.

The present disclosure pertains to a fuel system, the fuel system being associated with a combustionengine of a vehicle. The vehicle may for example be a heavy vehicle, such as a truck or a bus, but is not limited thereto.

The fuel system comprises at least one fuel tank. The fuel system also comprises an injection system for injecting fuel into the combustion engine. The injection system comprises an accumulator and one or more fuel injectors. The fuel system further comprises a first pump adapted to pump fuel tothe accumulator, the first pump being driven by the combustion engine. For the purpose ofmonitoring the pressure in the accumulator, a pressure sensor may be arranged in the accumulator.The fuel system also comprises an inlet metering valve configured to control the amount of fuelintroduced into the first pump, a first fuel filter arranged upstream of the first pump, and a secondpump arranged upstream of the first fuel filter. The second pump is adapted to transfer fuel from thefuel tank to the first pump. The fuel system further comprises a venturi driven by pressure providedby the second pump. The venturi is configured to withdraw fuel accumulated downstream of theinlet metering valve, at least when the inlet metering valve is closed. The inlet metering valve and theventuri may optionally constitute constituent components of the first pump. The fuel system mayoptionally also comprise a second fuel filter arranged between the fuel tank and the second pump.

The second fuel filter may for example be a water drainage fuel filter.

The fuel system may comprise further constituent components if desired. For example, the fuelsystem may comprise more than one fuel tank. Furthermore, the fuel system may comprise a thirdpump, for example a transfer pump configured to transfer fuel between a first fuel tank and a secondfuel tank. The fuel system may also comprise additional fuel filters, for example a fuel filter arranged in the fuel tank and adapted to filter coarse particulate matter from the fuel. ln accordance with the present disclosure, a method for determining filter clogging in the abovedescribed fuel system is provided. The method comprises a step of, when the vehicle is in an enginebraking mode, monitoring the pressure in the accumulator. The method further comprises a step of,if an increase of pressure in the accumulator is detected during said monitoring of the pressure in the accumulator, determining filter clogging in the fuel system.

During engine braking mode, no fuel is injected into the combustion engine and therefore no fuel isleaving the accumulator. ln general, it is in such a situation desirable that no fuel is transferred to theaccumulator by the first fuel pump. Therefore, the inlet metering valve is in general closed duringengine braking mode. However, a small leakage may occur over the inlet metering valve due to thedesign of the inlet metering valve and/or wear thereof. ln order to avoid that fuel being leakedpassed the inlet metering valve reaches the pumping element(s) of the first fuel pump, and thusinherently being pumped to the accumulator, the venturi is configured to provide a negativepressure so as to suck out the leaked fuel before it reaches the pumping element(s) of the first fuelpump. Thereby, it is avoided that the first pump starts to self-pump under normal operation of the fuel system.

However, if the venturi does not work as intended, the first pump will start to self-pump. This in turnresults in an unintended increase of the pressure in the accumulator of the injection system. lf thisoccurs during engine braking mode, it constitutes a clear indication that the venturi does not operateas intended. This may in turn be due to the feed pressure provided by the second pump not beingsufficiently high to enable the venturi to create the intended negative pressure for sucking out theleaked fuel accumulated downstream of the inlet metering valve. The reason for the second pumpnot being able to provide a sufficient pressure for the intended operation of the venturi may be clogging of filter(s) of the fuel system, leading to a too high pressure drop over said filter(s).

Thus, by means of the present method it is possible to get an early indication of filter clogging in thefuel system. By said early indication, it is possible to replace the fuel filter(s) before it/they becomeso clogged that said clogging may risk negatively affecting the operation of the fuel system during normal operation thereof, and thus the operation of the vehicle as such.

The increase of pressure in the accumulator may be detected over a preselected period of time. Forexample, it may be detected that the pressure in the accumulator increases gradually over saidpreselected period of time. lf the pressure increases over a period of time, and not simply momentarily, it is a clear indication that the first pump is self-pumping.

Moreover, it may be advantageous not to base a determination of filter clogging on a pressureincrease occurring at the start of engine braking mode for example because there may be a delay inthe stopping of the first pump pumping fuel to the accumulator. Therefore, the detection of apressure increase may be slightly delayed from the point in time at which it is determined that anengine braking mode is initiated and/or the point in time at which the inlet metering valve is closed.Thereby, it may be ensured that a detected increase of pressure in the accumulator is in fact due to the first pump self-pumping.

Moreover, it may be desirous to determine filter clogging on the basis of an increase of pressurewhich is equal to or more than a threshold value. The reason is to avoid the risk of incorrectlydetermining filter clogging due to normally occurring fluctuations in the pressure or in the accuracyof the detection provided by the pressure sensor in the accumulator. By way of example only, thethreshold value may for example be 20 bar. ln such a case, if a pressure increase of less than 20 bar is detected, if will be ignored but if a pressure increase of 20 bar or more is detected, it is concluded that filter clogging has occurred. The threshold value may instead of 20 bar be for example 50 bar or even higher, if desired. lf it is determined that filter clogging has occurred, a warning signal may be generated. The warningsignal may for example be addressed to a driver of the vehicle such that the driver is informed thatthe fuel filter(s) should be replaced. The warning signal may be transmitted to the driver by anypreviously known means for transmitting a warning to the driver, including a visible or tacticalwarning and/or a sound alarm. Alternatively, or additionally, the warning signal may be addressed toa control system of the vehicle, for example for the purpose of planning of service or for the controlof any constituent component of the vehicle or the vehicle as such. The warning signal may also beaddressed to a remote control centre, i.e. a control centre external of the vehicle. Such a remotecontrol centre may for example be a workshop or another control centre capable of planning service of the vehicle.

The method for determining filter clogging as described above may be performed by a controldevice. The control device may be configured to determine filter clogging on the basis of a detectingof an increase of pressure in the accumulator when the vehicle is in an engine braking mode. Thecontrol device may be configured to detect the increase of pressure in the accumulator by means ofa pressure sensor arranged to monitor the pressure in the accumulator, for example the pressuresensor normally arranged to detect the pressure in the accumulator for the purpose of controllingthe operation of the injection system. The control device may further be configured to perform each of the steps of the method described above.

The control device may constitute a control device of the fuel system as such. Alternatively, it mayconstitute any other control device of the vehicle. For example, it may constitute a control deviceconfigured to control the operation of the combustion engine or the powertrain of the vehicle as a whole.

Figure 1 shows a schematic side view of an example of a vehicle 1. The vehicle 1 comprises apowertrain 3 comprising an internal combustion engine 2. The powertrain 3 further comprises agearbox 4 adapted to transmit a driving torque at different gear ratios, from the internal combustionengine 2 to the driving wheels 5. The gearbox 4 is connected to the driving wheels 5 of the vehicle viaan output shaft 6 of the gearbox 4. The vehicle further comprises a fuel system 7 arranged toprovide fuel to the internal combustion engine 2 of the vehicle 1. The vehicle 1 may be a heavy vehicle, e.g. a truck or a bus. The vehicle may also be a marine vessel or a terrain vehicle.

Furthermore, the vehicle may be a hybrid vehicle in which case the vehicle comprises an electric machine (not shown) in addition to the combustion engine 2.

Figure 2 schematically illustrates a first exemplifying embodiment of a fuel system 7 of a combustionengine, such as the combustion engine 2 of the vehicle 1 illustrated in Figure 1. The method fordetermining filter clogging as described herein may be performed in the fuel system 7 illustrated in Figure 2.

The fuel system 7 comprises a first pump 10 and an injection system 11. The first pump 10 is knownin the art as a high pressure pump (HHP) and is driven by the combustion engine. The injectionsystem 11 comprises an accumulator 12, which is illustrated in the form of a common rail, and atleast one injector 13. ln general, the injection system comprises a plurality of injectors 13 (sixinjectors shown in Figure 2). Each injector is configured to inject fuel into the combustion engine. lnthe fuel system 7, fuel is transferred from the first pump 10, via a first fuel conduit 14, to theinjection system 11. The accumulator 12 is furthermore connected to a safety valve 15, such as amechanical dump valve, arranged to allow fuel to escape from the accumulator in case ofundesirable high pressures inside the accumulator. ln such cases, the pressure in the accumulatormay be decreased by allowing fuel to escape via the safety valve 15 and then being transferred backvia a first fuel return conduit 16 to a fuel tank 9. The fuel system 7 may further comprise a secondfuel return conduit 17 allowing fuel to be transferred from the first pump 10 back to the fuel tank 9 if needed.

The fuel system 7 further comprises a fuel filter 20 arranged upstream of the first pump 10. The fuelfilter 20 is sometimes referred to in the art as a main fuel filter. The fuel filter 20 is configured tofilter contaminations from the fuel before the fuel reaches the first pump 10, primarily to ensure thatsuch contaminations do not reach the combustion engine but also that such contaminations do notreach the injection system or even the first pump. The fuel filter 20 is typically arranged inside a filter housing protecting the fuel filter from the surroundings.

Moreover, the fuel system 7 shown in Figure 2 further comprises an inlet metering valve 18configured to control the amount of fuel being let into the first pump 10. The inlet metering valve 18may be arranged outside the first pump 10 as shown in Figure 2. More specifically, the inlet meteringvalve 18 may arranged in a second fuel conduit 21 connecting the first fuel filter 20 with the firstpump 10. Alternatively, the inlet metering valve 18 may be arranged inside a housing of the first pump 10 and may thus be considered to constitute a constituent component of the first pump 10. 11 The first pump 10 and the injection system 11 constitute constituent components of a high pressure system of the fuel system 7.

The fuel system 7 further comprises a second pump 22. The second pump 22 is sometimes referredto in the art as a low pressure pump. The second pump 22 is configured to supply fuel from the fueltank 9 to the first fuel filter 20, via a third fuel conduit 25 connecting the fuel tank 9 with the secondpump 22 and a fourth fuel conduit 23 connecting the second pump 22 with the first fuel filter 20. Thesecond pump 22 may thus be described as a feed pump. The second pump 22 may be driven by thecombustion engine or be operated independently of the combustion engine, for example by being driven by an electrical motor.

Furthermore, a second fuel filter 24 may arranged between the fuel tank 9 and the second pump 22,i.e. upstream of the second pump 22. As shown in Figure 2, the second fuel filter 24 may be arrangedin the third fuel conduit 25 connecting the fuel tank 9 with the second pump 22. The second fuel filter 24 may for example comprise a fine-mesh, water separating filter.

During operation, the second pump 22 pumps fuel from the fuel tank 9 (via the second fuel filter 24 ifpresent), through the fuel filter 20 arranged downstream of the second pump 22 and further to the first pump 10.

The fuel system further comprises a venturi 19 driven by the feed pressure of the second pump 22.The venturi 19 is arranged downstream of the first fuel filter 20. The venturi 19 is adapted to suck outfuel accumulated after the inlet metering valve 18, via a conduit 29. The venturi 19 may for examplebe connected to the second fuel return conduit 17 as shown in Figure 2. Alternatively, it may forexample be connected to a separate fuel return line connecting the venturi 19 to the fuel tank 9. Theventuri 19 may be arranged outside of the first pump 10 as shown in Figure 2. Alternatively, it may bearranged inside a housing of the first pump 10 and may thus be considered to constitute a constituent component of the first pump 10.

Although not illustrated in Figure 2, the fuel system 7 may comprise more than one fuel tank 9. Thefuel system may also comprise a third pump. For example, the fuel system 7 may comprise a thirdpump configured to transfer fuel from a second fuel tank to the first fuel tank 9. Alternatively, in caseof a plurality of fuel tanks, these may have a self-regulating flow between each other via a connection conduit connecting the fuel tanks. Moreover, the fuel system may comprise further 12 filters, for example a pre-filter arrangement 26 arranged inside the fuel tank 9. Such a pre-filterarrangement 26 may comprise a coarse mesh sieve for the purpose of filtering out particulate matter above a certain pre-determined size from the fuel.

The fuel filter 20, the first pump 10 and the injection system 11 are typically arranged on the combustion engine, whereas the fuel tank 9 may typically be arranged on the chassis of the vehicle.

The fuel system 7 may further comprise a control device 100. The control device 100 may beconfigured to control the fuel system 7 by controlling one or more constituent components of thefuel system. The control device may for example be configured to control the first pump 10 and/orthe second pump 22. The control device may also be configured to control the inlet metering valve18. The control device may further be configured to monitor and/or detect the pressure in the accumulator 12, for example by means of a pressure sensor 30.

The control device 100 may comprise one or more control units. The responsibility for a specificfunction or control may be divided between two or more of the control units. One or more of thecontrol units may be implemented in the form of a processing unit or computer. The control ofconstituent components in the fuel system 7 may be governed by programmed instructions/routines.These programmed instructions/routines typically take the forms of a computer program which,when executed in a computer or control unit, causes the computer or control unit to effect desiredforms of action, for example the steps of the method disclosed herein. As described above, such a computer or control unit may be or constitute a part of the control device 100.

During engine braking mode, no fuel is injected into the combustion engine. ln other words, no fuel isinjected into the combustion engine by the fuel injectors and therefore remains in the accumulator12. ln order to avoid an increase of the pressure in the accumulator 12, the first pump 10 shouldtherefore not transfer any fuel to the accumulator 12. However, since the first pump 10 is driven bythe combustion engine, it will automatically self-pump any fuel present in the first pump to theaccumulator. Therefore, in order to avoid fuel being present in the first pump, the inlet meteringvalve 18 is closed. However, there is generally a small leakage of fuel occurring in the inlet meteringvalve 18 leading to an accumulation of fuel after the inlet metering valve 18. This accumulatedamount of fuel is sucked out by means of the venturi 19 such that it will not reach the pumping element of the first pump 10. 13 ln case the first and/or the second fuel filter is clogged, the second pump 22 may be unable toprovide sufficient pressure for the intended operation of the venturi 19. This will in turn lead to theleakage of fuel reaching the pumping element of the first pump 10 and the first pump 10 willtherefore start self-pumping. Such an unintended self-pumping of the first pump 10 will lead to anincreased pressure in the accumulator 12. lf the pressure becomes too high, the safety valve 15 will automatically open to avoid any risk of damage to the constituent components of the fuel system 7. ln accordance with the present method, the above described situation of the first pump 10 startingto self-pump is utilised for identifying filter clogging in the fuel system. More specifically, this isachieved by monitoring the pressure in the accumulator 12 when the vehicle is in engine brakingmode. ln case there is an increase in the pressure in the accumulator 12 in this situation, it can beconcluded that the first pump 10 is unintentionally self-pumping. This in turn indicates that thepressure supplied by the second pump is insufficient. An insufficient pressure provided by the secondpump 22 is an indication that the first and/or the second fuel filter is at least partly clogged and should be replaced.

Figure 3 schematically illustrates the ability of the venturi 19 of the fuel system as shown in Figure 2to create a negative pressure PV, in the space downstream of the inlet metering valve 18, as afunction of the feed pressure Pfeed provided by the second pump 22. ln the pressure interval P1 of thefeed pressure provided by the second pump 22, the feed pressure into the first pump 10 is so lowthat there is a risk for too low pressure in the accumulator 12. ln other words, the pressure providedby the second pump 22 may be insufficient to transfer enough fuel to the first pump 10 to provide anecessary pressure in the accumulator 12 to accurately operate the injection system 11 to inject anintended amount of fuel into the combustion engine. This may in turn lead to a situation where the vehicle can no longer be operated as intended. ln the pressure interval P2, self-pumping of the first pump 10 may start to happen. However, thefeed pressure is sufficiently high in order not to risk that the pressure in the accumulator 12 becomestoo low. Therefore, there is no risk for not being able to operate the injection system 11 as intendedfor injection of fuel into the combustion engine, if desired. ln other words, the feed pressuresupplied by the second pump is sufficient for enabling the first pump to achieve a desired minimumpressure in the accumulator 12. However, if an engine braking mode is activated, no fuel will leavethe accumulator and the pressure in the accumulator will thus increase as will be further explainedbelow with reference to Figure 4 if the first pump starts to self-pump. The cause of the decreased feed pressure as shown by the pressure interval P1 and P2 in Figure 3 may be one or more of the fuel 14 filters becoming clogged. ln the pressure interval P3, the feed pressure is however at the normal levelwith only a small pressure drop over the fuel filter(s). ln this pressure interval, the risk for self-pumping of the first pump 10 is very low since the venturi 19 is able to create a sufficient negative pfeSSUfe.

Figure 4 schematically illustrates the change in pressure Pa in the accumulator and the feed pressurePfaad, in a fuel system such as the one shown in Figure 2, over time t during engine braking. At thepoint in time t1, the feed pressure Pfaad is so low that the first pump 10 starts to self-pump and thepressure Pa in the accumulator thus starts to increase. The self-pumping stops when the feedpressure Pfaad provided by the second pump 22 has reached a sufficient value. This point in time isillustrated in the figure as tz. Thereafter, the pressure Pa in the accumulator is maintained as long asthere is no fuel leaving the accumulator 12. Still, the feed pressure continues to increase. The point intime tg represents a point in time where injection of fuel into the combustion engine is initiated and thus both the pressure Pa in the accumulator 12 and the feed pressure Pfaad decreases.

Figure 5 represents a flowchart schematically illustrating one exemplifying embodiment of themethod for determining filter clogging according to the present disclosure. The method maycomprise a first step, S110, of determining that the vehicle is in an engine braking mode. The methodcomprises a step, S120, of, when the vehicle is in an engine braking mode, monitoring of pressure inthe accumulator. The method further comprises a step, S130, of determining of filter clogging if anincrease of pressure in the accumulator is detected during step S120, i.e. during the monitoring of pressure in the accumulator when the vehicle is in an engine braking mode.

Figure 6 schematically illustrates an exemplifying embodiment of a device 500. The control device100 described above may in a version comprise the device 500 or constitute the device 500.

Alternatively, the control device 100 may be comprised in the device 500.

The device 500 comprises a non-volatile memory 520, a data processing unit 510 and a read/writememory 550. The non-volatile memory 520 has a first memory element 530 in which a computerprogram, e.g. an operating system, may be stored for controlling the function of the device 500. Thenon-volatile memory 520 may also have a second memory element 540. According to an alternative embodiment, the non-volatile memory 520 may be replaced by a volatile memory (not depicted).

The device 500 further comprises a bus controller, a serial communication port, I/O means, an A/Dconverter, a time and date input and transfer unit, an event counter and an interruption controller (not depicted).

There is provided a computer program P which comprises routines for determining filter clogging in afuel system associated with a combustion engine of a vehicle. The fuel system comprises a fuel tank;an injection system for injecting fuel into the combustion engine, the injection system comprising anaccumulator and at least one fuel injector; a first pump adapted to pump fuel to the accumulator,the first pump being driven by the combustion engine; an inlet metering valve configured to controlthe amount of fuel introduced into the first pump; a first fuel filter arranged upstream of the firstpump; a second pump arranged upstream of the first fuel filter, the second pump adapted to transferfuel from the fuel tank to the first pump; and a venturi driven by pressure provided by the secondpump, the venturi configured to withdraw fuel accumulated downstream of the inlet metering valvewhen the inlet metering valve is closed. The fuel system may further comprise a second fuel filterarranged between the fuel tank and the second pump. The computer program comprises routinesfor, when the vehicle is in an engine braking mode, monitoring of pressure in the accumulator. Thecomputer program further comprises routines for, if an increase of pressure in the accumulator isdetected during said monitoring of pressure in the accumulator, determining filter clogging in the fuel system.

The program P may be stored in an executable form or in a compressed form in a memory 560 and/or in a read/write memory 550.

The data processing unit 510 may perform one or more functions, i.e. the data processing unit 510may effects a certain part of the program P stored in the memory 560 or a certain part of the program P stored in the read/write memory 550.

The data processing device 510 can communicate with a data port 599 via a data bus 515. The non-volatile memory 520 is intended for communication with the data processing unit 510 via a data bus512. The separate memory 560 is intended to communicate with the data processing unit 510 via adata bus 511. The read/write memory 550 is adapted to communicate with the data processing unit510 via a data bus 514. The communication between the constituent components may beimplemented by a communication link. A communication link may be a physical connection such asan optoelectronic communication line, or a non-physical connection such as a wireless connection, e.g. a radio link or microwave link. 16 When data are received on the data port 599, they may be stored temporarily in the second memoryelement 540. When input data received have been temporarily stored, the data processing unit 510 is prepared to effect code execution as described above.

Parts of the methods herein described may be effected by the device 500 by means of the dataprocessing 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 herein described are executed.

Claims (5)

1. 7 A method for determining filter clogging in a fuel system (7) associated with a combustionengine (2) of a vehicle,the fuel system (7) comprising: a fuel tank (9); an injection system (11) for injecting fuel into the combustion engine (2), theinjection system comprising an accumulator (12) and at least one fuel injector (13); a first pump (10) adapted to pump fuel to the accumulator (12), the first pump (10)being driven by the combustion engine (2); an inlet metering valve (18) configured to control the amount of fuel introduced intothe first pump (10); a first fuel filter (20) arranged upstream of the first pump (10); a second pump (22) arranged upstream of the first fuel filter (20), the second pump(22) adapted to transfer fuel from the fuel tank (9) to the first pump (10); a venturi (19) driven by pressure provided by the second pump, the venturiconfigured to withdraw fuel accumulated downstream of the inlet metering valve (18) whenthe inlet metering valve (18) is closed; and optionally a second fuel filter (24) arranged between the fuel tank (9) and the secondpump (22);the method comprising the steps of: when the vehicle is in an engine braking mode, monitoring of pressure in theaccumulator (12); and if an increase of pressure in the accumulator (12) is detected during said monitoring of pressure in the accumulator (12), determining filter clogging in the fuel system.

2. The method according to claim 1, wherein the step of determining filter clogging in the fuelsystem comprises detecting an increase of pressure in the accumulator over at least a preselected period of time.

3. The method according to any one of claims 1 or 2, wherein the step of determining filterclogging comprises detecting an increase of pressure in the accumulator after a firstpredetermined time has lapsed since initiation of engine braking mode and/or since closure of the inlet metering valve.

4. 7. 8. 18 The method according to any one of the preceding claims, wherein the step of determiningfilter clogging comprises detecting an increase of pressure in the accumulator, wherein the increase of pressure is equal to or more than a threshold value. The method according to any one of the preceding claims, further comprising a step of generating a warning signal if filter clogging has been determined. A control device (100) configured to determine filter clogging in a fuel system associated witha combustion engine of a vehicle,the fuel system (7) comprising: a fuel tank (9);an injection system (11) for injecting fuel into the combustion engine (2), the injectionsystem comprising an accumulator (12) and at least one fuel injector (13); a first pump (10) adapted to pump fuel to the accumulator (12), the first pump (10)being driven by the combustion engine (2); an inlet metering valve (18) configured to control the amount of fuel introduced intothe first pump (10); a first fuel filter (20) arranged upstream of the first pump (10); a second pump (22) arranged upstream of the first fuel filter (20), the second pump(22) adapted to transfer fuel from the fuel tank (9) to the first pump (10);a venturi (19) driven by pressure provided by the second pump, the venturi configured towithdraw fuel accumulated downstream of the inlet metering valve (18) when the inletmetering valve (18) is closed; and optionally a second fuel filter (24) arranged between the fuel tank (9) and the secondpump (22); wherein the control device is configured to determine filter clogging on the basis of adetection of an increase of pressure in the accumulator when the vehicle is in an engine braking mode. The control device (100) according to claim 6, wherein the control device is configured todetect said increase of pressure in the accumulator (12) over at least a preselected period of time. The control device (100) according to any one of claims 6 or 7, wherein the control device is configured to detect the increase of pressure in the accumulator (12) after a first 10. 11. 12. 13. 19 predetermined time has lapsed since initiation of engine braking mode and/or since closure of the inlet metering valve. The control device (100) according to any one of claims 6 to 8, wherein the control device isconfigured to determine filter clogging on the basis of a detection of an increase of pressure in the accumulator (12) equal to or more than a threshold value. The control device (100) according to any one of claims 6 to 9, further configured to generate a warning signal if determining filter clogging. A vehicle comprising a combustion engine (2) and a fuel system (7) associated with thecombustion engine (2), the vehicle further comprising a control device (100) according to any one of claims 6 to 10. A computer program (P), wherein said computer program comprises program code for causing a control device to perform the method according to any one of claims 1 to

5. A computer-readable medium comprising instructions, which when executed by a controldevice, cause the control device to perform the method according to any one of claims 1 to