WO2014200425A1 - Fuel system for combustion engine and a method for reducing the risk of operational disturbance caused by paraffined fuel in the fuel system - Google Patents

Fuel system for combustion engine and a method for reducing the risk of operational disturbance caused by paraffined fuel in the fuel system Download PDF

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Publication number
WO2014200425A1
WO2014200425A1 PCT/SE2014/050697 SE2014050697W WO2014200425A1 WO 2014200425 A1 WO2014200425 A1 WO 2014200425A1 SE 2014050697 W SE2014050697 W SE 2014050697W WO 2014200425 A1 WO2014200425 A1 WO 2014200425A1
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WO
WIPO (PCT)
Prior art keywords
fuel
fuel tank
conduit
transfer pump
filter
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/SE2014/050697
Other languages
French (fr)
Inventor
Dan CEDFORS
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Scania CV AB
Original Assignee
Scania CV AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Scania CV AB filed Critical Scania CV AB
Priority to DE112014002283.7T priority Critical patent/DE112014002283T5/en
Publication of WO2014200425A1 publication Critical patent/WO2014200425A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/62—Regenerating the filter material in the filter
    • B01D29/66—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M37/00—Apparatus or systems for feeding liquid fuel from storage containers to carburettors or fuel-injection apparatus; Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines
    • F02M37/04—Feeding by means of driven pumps
    • F02M37/08—Feeding by means of driven pumps electrically driven
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D33/00—Controlling delivery of fuel or combustion-air, not otherwise provided for
    • F02D33/003—Controlling the feeding of liquid fuel from storage containers to carburettors or fuel-injection apparatus ; Failure or leakage prevention; Diagnosis or detection of failure; Arrangement of sensors in the fuel system; Electric wiring; Electrostatic discharge
    • F02D33/006—Controlling the feeding of liquid fuel from storage containers to carburettors or fuel-injection apparatus ; Failure or leakage prevention; Diagnosis or detection of failure; Arrangement of sensors in the fuel system; Electric wiring; Electrostatic discharge depending on engine operating conditions, e.g. start, stop or ambient conditions
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/04—Introducing corrections for particular operating conditions
    • F02D41/042—Introducing corrections for particular operating conditions for stopping the engine
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/3082—Control of electrical fuel pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M37/00—Apparatus or systems for feeding liquid fuel from storage containers to carburettors or fuel-injection apparatus; Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines
    • F02M37/0076—Details of the fuel feeding system related to the fuel tank
    • F02M37/0088—Multiple separate fuel tanks or tanks being at least partially partitioned
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M37/00—Apparatus or systems for feeding liquid fuel from storage containers to carburettors or fuel-injection apparatus; Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines
    • F02M37/04—Feeding by means of driven pumps
    • F02M37/18—Feeding by means of driven pumps characterised by provision of main and auxiliary pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M37/00—Apparatus or systems for feeding liquid fuel from storage containers to carburettors or fuel-injection apparatus; Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines
    • F02M37/22—Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines, e.g. arrangements in the feeding system
    • F02M37/32—Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines, e.g. arrangements in the feeding system characterised by filters or filter arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M37/00—Apparatus or systems for feeding liquid fuel from storage containers to carburettors or fuel-injection apparatus; Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines
    • F02M37/22—Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines, e.g. arrangements in the feeding system
    • F02M37/32—Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines, e.g. arrangements in the feeding system characterised by filters or filter arrangements
    • F02M37/40—Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines, e.g. arrangements in the feeding system characterised by filters or filter arrangements with means for detection of clogging
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K15/00—Arrangement in connection with fuel supply of combustion engines or other fuel consuming energy converters, e.g. fuel cells; Mounting or construction of fuel tanks
    • B60K15/03—Fuel tanks
    • B60K2015/03118—Multiple tanks, i.e. two or more separate tanks
    • B60K2015/03138—Pumping means between the compartments
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/021—Engine temperature

Definitions

  • the present invention pertains to a fuel system for a combustion engine, according to the preamble of claim 1.
  • the invention also pertains to a combustion engine with such a fuel system according to claim 11, a vehicle with such a fuel system according to claim 12 and a method to reduce the risk of operational disturbances caused by paraf- finated fuel in a fuel system according to claim 13.
  • a combustion engine such as a piston engine, which is driven by diesel or petrol, is equipped with a fuel system to transport fuel from one or several fuel tanks to the combustion engine's injection system.
  • the fuel system comprises one or several fuel pumps which may be driven mechanically by the combustion engine or be driven by an electrical engine.
  • the fuel pumps create a fuel flow and pressure to transport the fuel to an accumulator which may be in the form of a so-called common rail, and fur- ther to the combustion engine's injection system, which supplies the fuel to the combustion engine's combustion chamber.
  • Common rail may be excluded, and the fuel system may instead comprise another form of an injection system, for example a piezo or a unit injection system.
  • Fuel systems also comprise fuel filters for filtration of the fuel before it reaches the combustion engine's injection system.
  • the combustion engine and its injection system are sensitive to contaminations and may be negatively affected if the fuel is too polluted. Contaminations may relate to solid particles, gas or liquid. Even if the fuel only comprises a small amount of contaminations, the consequence may be that the com- bustion engine may not be driven by the fuel.
  • Fuel systems therefore comprise a fuel filter, which both filters away particles and separates water occurring in the fuel.
  • the fuel filter may be a so-called insert fuel filter, which comprises a replaceable filter element arranged inside a filter housing. When the outdoor temperature decreases, the fuel inside the fuel system, such as diesel or bio-diesel, may become paraffinated.
  • the temperature at which the fuel is paraffinated depends on the composition of the fuel and may vary between plus 10 degrees to minus 50 degrees for a number of different fuel compositions.
  • the paraffination may lead to the fuel filter becoming clogged, which means that the fuel may be unable to reach the combustion engine in case of a cold start.
  • the fuel which is inside the fuel conduits may become paraffinated as well and cause a stop in the fuel conduits. It is therefore desirable to minimise the risk of fuel in the filter housing and fuel conduits becoming paraffinated in cold weather.
  • a reversible fuel pump may be arranged, to change the direction of the flow in a fuel system, thus emptying fuel conduits of fuel.
  • a fuel system for a combustion engine comprising a fuel pump and a two-part fuel tank.
  • the fuel pump's direction is changed, so that the fuel conduits are emptied of fuel.
  • a smaller part of the fuel tank comprises a heater, and when the vehicle is started the smaller part is filled first, so that the fuel may be heated up before it is pumped out into the fuel conduits.
  • the document US-2010/0031930 shows a fuel system for a combustion engine, comprising an electrically driven fuel pump, which supplies the fuel system's injection system with fuel.
  • the electrically operated fuel pump in a first position supplies fuel from a fuel tank to the engine, and in a second position the fuel pump supplies fuel from the fuel tank to a device for regeneration of the particulate filter.
  • the first and the second positions correspond to different rotational directions in the electrically operated fuel pump.
  • the objective of the present invention is to achieve a fuel system for a combustion engine which reduces the risk of operational disturbances caused by paraffinated fuel.
  • Another objective of the invention is to achieve a fuel system for a combustion engine, which reduces the risk of fuel staying in the fuel filter in cold weather.
  • Another objective of the invention is to achieve a fuel system for a combustion engine, which is flexible and has a broad control interval.
  • Another objective of the invention is to achieve a fuel system for a combustion engine, which is non-bulky.
  • Another objective of the invention is to achieve a fuel system for a combustion engine, which facilitates a cold start. These objectives are achieved with a fuel system of the type specified at the beginning, which is characterised by the features specified in the characterising portion of claim 1.
  • the pre-filter comprises a replaceable filter element, which is arranged inside a filter housing.
  • the transfer pump is a low pressure pump.
  • the transfer pump's direction is changed when the combustion engine is shut down and there is a risk of paraffination of fuel.
  • the risk of paraffinated fuel clogging the transfer filter or causing a stop in the first fuel conduit is reduced.
  • a clogged transfer filter and/or a stop in the fuel conduit entails that fuel is not fed to the first fuel tank, which in turn entails that the combustion engine may not be supplied with fuel.
  • the transfer pump's direction is changed when the combustion engine is in operation and there is a risk of paraffination of fuel.
  • the transfer pump is reversible by changing the rotational direction of the electrical engine connected to the transfer pump.
  • the transfer pump By connecting the transfer pump to a control device via a CAN-bus, the transfer pump may be steered toward different parameters, such as pressure in the fuel conduits, pressure fall over the fuel filter, temperatures etc. In this manner a fuel system is achieved, which is flexible, which has a broader control interval than prior art and which in this manner allows for a correct fuel supply to the first fuel tank.
  • a coarse mesh sieve is arranged at one end of the first fuel conduit, located at the bottom of the second fuel tank. The coarse mesh sieve is thus arranged upstream of the transfer pump and the pre-filter.
  • the coarse mesh sieve filters away particles above a predetermined size and is a filtering element which is often subjected to paraf- finated fuel.
  • a first temperature sensor is connected to the control device, to determine the outdoor temperature of the environment where the vehicle is located.
  • the transfer pump may thus preferably be controlled so that its direction is changed when the outdoor temperature is below a certain temperature threshold, corresponding to the temperature at which the fuel becomes paraffinated, and thus indicat- ing that there is a risk of fuel paraffination.
  • a risk of fuel paraffination is identified by measuring the temperature of the combustion engine.
  • a second temperature sensor is connected to the control device to determine the temperature of the combustion engine.
  • this is determined by measuring the temperature of the combustion engine's coolant.
  • the temperature of the combustion engine/coolant may indicate whether there is a risk of fuel paraffination.
  • the transfer pump may thus preferably be controlled so that its direction is changed when the combustion engine's temperature is below a certain temperature threshold, corresponding to the temperature at which the fuel becomes paraf- finated, and thus indicating that there is a risk of fuel paraffination.
  • a risk of fuel paraffination is identified by determining the pressure fall over the pre-filter.
  • a first pressure sensor is arranged upstream of the pre- filter and a second pressure sensor is arranged downstream of the pre-filter. With these pressure sensors the pressure fall over the pre-filter may be determined, which may indicate when the pre-filter begins to be clogged. Clogging of the pre-filter may depend on wholly or partly paraffinated fuel, and thus the pressure fall over the pre-filter may indicate whether there is a risk of paraffination.
  • the transfer pump may suitably be controlled so that its direction changes when the pressure fall over the pre-filter exceeds a certain pressure fall threshold and thus indicates that there is a risk of fuel paraffination.
  • the pressure sensors are suitably differential pressure sensors and are connected to the control device. The pressure sensors are preferably read when the combustion engine is in operation.
  • Clogging of the pre-filter may be caused by paraffination, but may also be due to con- taminants in the fuel.
  • the identified pressure fall is combined with the outdoor temperature and/or the combustion engine's temperature.
  • the transfer pump may thus preferably be controlled so that its direction changes when the pressure fall over the pre-filter exceeds a certain pressure fall threshold, at the same time as the outdoor temperature and/or the combustion engine's temperature falls below a certain temperature threshold value and thus indicates that there is a risk of fuel paraffination.
  • a risk of paraffination is identified by determining the relationship between the transfer pump's operation and the fuel flow in the first fuel conduit.
  • a flow meter is arranged in the first fuel conduit, which flow meter is connected to the control device via the CAN-bus.
  • the power consumption of the electrical engine operating the transfer pump is measured with the help of the control device, which indicates how hard the transfer pump is working.
  • the power output of the electrical engine operating the transfer pump is measured with the help of the con- trol device.
  • a certain power consumption by, or a certain power output from, the electrical engine normally corresponds to a certain fuel flow in the first fuel conduit.
  • an increased power consumption or an increased power output entails that the fuel flow in the first fuel conduit increases.
  • the control device identify an increased power consumption or an increased power output at the same time as the fuel flow in the first fuel conduit remains unchanged, the conclusion may be drawn that the pre-filter and/or the coarse mesh sieve are probably clogged, and that the fuel flow through the first fuel conduit is therefore reduced.
  • the clogging may be due to wholly or partly paraffinated fuel, and thus the relationship between the transfer pump's operation and the fuel flow in the first fuel conduit may indicate that there is a risk of fuel paraffination.
  • the transfer pump may suitably be controlled in such a way, that its direction is changed when the relationship between the transfer pump's operation and the fuel flow in the first fuel conduit indicate that the pre-filter and/or the coarse mesh sieve are clogged.
  • Power consumption and/or power output and fuel flow in the first fuel conduit are preferably read when the combustion engine is in operation.
  • the flow meter is arranged upstream of the transfer pump and downstream of the coarse mesh sieve.
  • the flow meter is arranged downstream of the pre- filter.
  • Clogging of the pre-filter and/or the coarse mesh sieve may be caused by paraffinated fuel, but may also be due to contaminants in the fuel.
  • the identified relationship between the trans- fer pump's operation and the fuel flow in the first fuel conduit is compared with the outdoor temperature and/or the combustion engine's temperature.
  • the transfer pump may preferably be controlled so that its direction is changed when the relationship between the transfer pump's operation and the fuel flow in the first fuel conduit indicate that the pre-filter and/or the coarse mesh sieve are clogged, at the same time as the outdoor temperature and/or the combustion engine's temperature fall below a certain temperature threshold value.
  • a risk of fuel paraffination is identified by combining some or all of the above ways. For example, both the outdoor temperature, the temperature of the com- bustion engine, the pressure fall over the pre-filter and the relationship between the transfer pump's operation and the fuel flow in the first fuel conduit may be used to determine whether there is a risk of fuel paraffination.
  • the first and/or the second temperature sensor are read when the combustion engine is in operation in order to determine whether there is a risk of fuel paraffination.
  • the reading is carried out during operation, specifically when there is a change of temperature zone.
  • the first and/or the second temperature sensor are read when the com- bustion engine is shut down and the vehicle is at a standstill.
  • the first and/or the second temperature sensor are read both when the combustion engine is in operation and when the combustion engine is shut down and the vehicle is at a standstill.
  • a valve is arranged in the first fuel conduit downstream of the pre-filter. The valve is normally steered to a first position, entailing that the first fuel conduit is connected with the first fuel tank. The valve may also be steered to a second position, entailing that the first fuel conduit is connected with the air surrounding the fuel system.
  • the first fuel conduit is connected with the surrounding air via an air filter.
  • the valve is preferably connected to the control device via the CAN-bus.
  • the valve is steered to its second position when a risk of fuel paraffination has been identified.
  • the transfer pump When the transfer pump's direction is then changed, the transfer pump thus sucks air through the first fuel conduit, and fuel in the first fuel conduit as well as in the pre-filter is supplied to the second fuel tank. The fuel is thus fed through the coarse mesh sieve, which is thus freed of clogging particles. Thus the risk of operational disturbances caused by paraffinated fuel is reduced.
  • valve's first position is maintained when it has been identified that there is a risk of fuel paraffination.
  • the transfer pump sucks fuel from the first fuel tank, further through the pre- filter, and then feeds the fuel through the coarse mesh sieve into the second fuel tank.
  • a fuel return conduit is arranged in connection with the first fuel tank and the fuel system's high pressure system. Pressurised warm fuel may in this manner be re- turned back to the first fuel tank, instead of being transported to the combustion engine' s combustion chamber. The fuel in the first fuel tank is thus warmer than the fuel in the second fuel tank when the combustion engine is in operation.
  • the warm fuel may thus dissolve any potential paraffinated fuel occurring in the first fuel conduit, in the pre-filter and the coarse mesh sieve when the transfer pump's direction is changed.
  • the valve is then steered to its second position, so that the first fuel conduit and the pre-filter are emptied of fuel, and the first fuel tank maintains a predetermined fuel level.
  • the first fuel conduit is arranged so that it opens out, at one end, into the first fuel tank's upper part, above the fuel surface. In this manner the first fuel conduit is connected with air existing in the first fuel tank.
  • the transfer pump When it has been identified that there is a risk of fuel paraffination, and the transfer pump's direction is changed, the transfer pump sucks out air from the first fuel tank through the first fuel conduit, and in this manner the first fuel conduit and the pre-filter are emptied of fuel. The fuel occurring inside the first fuel conduit and the pre-filter is pressed through the coarse mesh, which in this manner is freed of clogging particles. Thus the risk of operational distur- sayes caused by paraffinated fuel is reduced.
  • the transfer pump's direction is changed when a risk of fuel paraffination has been identified and the combustion engine is shut down.
  • the transfer pump's direction is changed when there is a risk of paraffination of fuel and the com- bustion engine is in operation.
  • the first fuel tank is adapted to hold a smaller volume than the second fuel tank.
  • This design entails a less bulky first fuel tank, which is easier to arrange inside a chassis with limited space.
  • a non-bulky fuel system is achieved.
  • a smaller first fuel tank entails that the fuel system may supply fuel to the combustion engine at a lower fuel level, than if the same fuel volume had been supplied to the larger second fuel tank.
  • a fuel system for a combustion engine is achieved, which entails a flexible regulation of fuel supply and thus avoids operational disturbances with a low fuel level in the fuel tank.
  • the first fuel tank holds 20-50 litres and the second fuel tank holds 300-1,000 litres.
  • the main feeding pump is a low pressure pump, which is operated by a second electrical engine.
  • the main feeding pump is also reversible. In this manner a more efficient and flexible regulation of fuel supply to the combustion engine is achieved.
  • the main feeding pump is arranged in the first fuel tank. In this manner, the main feeding pump is protected from the environment and a natural cooling of the fuel in the first fuel tank is obtained.
  • the transfer pump and the pre-filter are also arranged inside the first fuel tank. With the main feeding pump, the transfer pump, the pre-filter and the valve arranged inside the first fuel tank, a non-bulky fuel system is achieved.
  • the first fuel tank comprises a level sensor to determine the fuel level in the first fuel tank.
  • an overflow line is arranged in connection with the first fuel tank and the second fuel tank.
  • the overflow line is arranged in connection with the first fuel tank's upper side and the second fuel tank's upper side.
  • the overflow line may be arranged in connection with the first fuel tank' s bottom.
  • the transfer pump is controlled to feed fuel from the second fuel tank to the first fuel tank when the fuel level in the first fuel tank, determined with the level sensor, falls below a predetermined value.
  • Fig. 1 shows a schematic side view of a vehicle, comprising a fuel system for a combustion engine according to the present invention
  • Fig. 2 shows a coupling diagram for a fuel system according to a first embodiment of the present invention
  • Fig. 3 shows a coupling diagram for a fuel system according to a second embodiment of the present invention
  • Fig. 4a-4b show flow charts of methods to reduce the risk of operational disturbances caused by paraffinated fuel in a fuel system according to the present invention.
  • Fig. 1 shows a schematic side view of a vehicle 1, which vehicle which comprises a fuel system 4 for a combustion engine 2 according to the present invention.
  • the combustion engine 2 is connected to a gearbox 6, which is further connected to the driving wheels 8 of the vehicle 1 via a transmission.
  • the vehicle also comprises a chassis 10.
  • Fig. 2 shows a coupling diagram for a fuel system 4 in a combustion engine 2 according to the present invention.
  • the fuel system 4 comprises several components, whereof a main fuel filter 12, a high pressure pump 14, an accumulator in the form of a so- called common rail 16, and an injection system 18, schematically displayed in the form of a fuel injector, are arranged in the combustion engine 2 (the combustion engine 2 is displayed in Fig. 1).
  • the common rail 16 may be replaced by another form of an injection system 18, e.g. a piezo or a unit injection system.
  • the high pressure pump 14, the common rail 16 and the injection system 18 constitute components in the high pressure system 19 of the fuel system 4.
  • the fuel system 4 also comprises a first fuel tank 20, a second fuel tank 22, a third fuel tank 24, a main feeding pump 26, a transfer pump 28, and a pre-filter 30. These components may be arranged in the vehicle's chassis 10 (the chassis 10 is displayed in Fig. 1).
  • the main fuel filter 12 is arranged downstream of the main feeding pump 26 and upstream of the high pressure pump 14 in the fuel system 4.
  • the fuel system 4 comprises a fuel return conduit 13, through which pressurised warm fuel is returned from the high pressure system 19 of the fuel system 4, back to the first fuel tank 20. All three tanks 20, 22, 24 are connected in their respective upper parts, with a valve device 50, which communicates via an air filter 51 with the surrounding environment.
  • the ventilation conduit 50 ensures that the pressure in the respective tanks 20, 22, 24 is and remains substantially the same, and equal to the ambient air pressure, regardless of how much fuel is in the respective tanks.
  • the air filter 51 prevents contaminants in the surrounding air from penetrating into the ventilation conduit 50 in connection with ventilation of the tanks.
  • the first fuel tank 20 is adapted to hold a smaller volume than the second fuel tank 22 and the third fuel tank 24.
  • the second fuel tank 22 and the third fuel tank 24 correspond to main fuel tanks and hold substantially the same volume, and have a self- regulating flow between each other via a connection conduit 34, arranged between the lower part of the second fuel tank 22 and the third fuel tank 24.
  • the transfer pump 28 is reversible, and according to Fig. 2, arranged between the first fuel tank 20 and the second fuel tank 22.
  • the transfer pump 28 is operated by a first electrical engine Ml and its main task is to supply fuel from the second fuel tank 22 to the first fuel tank 20 via a first fuel pipe 36.
  • the main feeding pump 26 is operated by a second electrical engine M2 and is arranged inside the first fuel tank 20, and is thus protected from the environment and cooled by the fuel. Between the first fuel tank 20 and the second fuel tank 22 an overflow conduit 38 is arranged, so that fuel may be transported across from the first fuel tank 20 to the second fuel tank 22, if the first fuel tank 20 becomes overfilled.
  • the main task of the main feeding pump 26 is to feed the fuel from the first fuel tank 20 via a second fuel conduit 40 through the main fuel filter 12 and further to the high pressure system 19. The fuel is then fed, at a high pressure, to the common rail 16 and further along to the injection system 18.
  • the main feeding pump 26 and the transfer pump 28 are controlled by a control device 42 via a CAN bus 44.
  • the pre-filter 30 is arranged downstream of the transfer pump 28 and is preferably a fine mesh, water separating filter.
  • a coarse mesh sieve 52 is arranged at one end of the first fuel conduit 36, located at the second fuel tank 22 .
  • the coarse mesh sieve 52 is thus arranged upstream of the transfer pump 28, entailing that the transfer pump 28 sucks fuel through the coarse mesh sieve 52.
  • the coarse mesh sieve 52 filters away particles above a certain predetermined size.
  • the transfer pump 28 then pressurises the fuel, and then feeds it through the pre-filter 30, via the first fuel pipe 36, further along to the first fuel tank 20.
  • the fuel in the first fuel tank 20 has thus passed both a coarse mesh sieve 52 and a fine mesh pre-filter 30, entailing that the main feeding pump 26, which is arranged in the first fuel tank 20, is protected against impurities.
  • the pre-filter 30 downstream of the transfer pump 28, the fuel is pressed through the pre-filter 30, entailing that the fuel passes through the pre-filter 30 more easily, and the risk that the pre-filter 30 may become clogged is thus reduced.
  • a first level sensor 46 is arranged to identify the fuel level in the first fuel tank 20.
  • the transfer pump 28 is controlled to feed fuel from the second fuel tank 22 to the first fuel tank 20.
  • a second level sensor 48 is arranged in the second fuel tank 22 to identify the fuel level in the second fuel tank 22.
  • the first level sensor 46 and the second level sensor 48 are connected to the CAN bus 44 and the control device 42, which controls the transfer pump 28 and the main feeding pump 26.
  • a first temperature sensor 60 is connected to the control device 42. The first temperature sensor 60 provides the control device 42 with the outdoor temperature of the environment where the vehicle 1 (displayed in Fig. 1) is located.
  • a low outdoor temperature may indicate that there is a risk of fuel paraffination.
  • a second temperature sensor 62 is also connected to the control device 42, in order to provide the control device 42 with the temperature of the combustion engine 2 (displayed in Fig. 1).
  • a low temperature of the combustion engine 2 may indicate that there is a risk of fuel paraffination.
  • a valve 70 is arranged downstream of the pre-filter 30 in connection with the first fuel conduit 36. The valve 70 is normally steered to a first position, entailing that the first fuel conduit 36 is connected with the first fuel tank 20. In the valve's 70 second posi- tion, the first fuel conduit 36 is connected with air surrounding the fuel system, via an air filter 71. The air filter 71 prevents contaminants in the surrounding air from penetrating into the first fuel conduit 36 in connection with steering of the valve 70 into its second position.
  • the valve is connected to the control device 42 via the CAN-bus 44.
  • a flow meter 72 connected to the control device 42, is arranged in the first fuel conduit, upstream of the transfer pump 28, in order to determine the relationship between the work of the transfer pump 28 and the fuel flow in the first fuel conduit 36.
  • the power consumption of the electrical engine Ml oper- ating the transfer pump 28 may be determined.
  • the power output from the electrical engine Ml operating the transfer pump 28 is determined with the help of the control device 42.
  • the power consumption and/or the power output indicates how hard the transfer pump 26 is working.
  • a certain power consumption or a certain power output corresponds to a certain fuel flow in the first fuel conduit 36.
  • control device 42 identify an increased power consumption, or an increased power output, at the same time as the flow meter 72 identifies a substantially unchanged fuel flow, alternatively a reduced fuel flow, this indicates that the pre-filter 30 and/or the coarse mesh sieve 52 is clogged.
  • the clogging may be due to paraffinated fuel, and thus information about the relationship between the operation of the transfer pump 28 and the fuel flow in the first fuel conduit 36 may be used to indicate whether there is a risk of fuel paraffination.
  • a first pressure sensor 74 is arranged upstream of the pre-filter 30, and a second pressure sensor 76 is arranged downstream of the pre-filter 30.
  • the so- called pressure fall over the pre-filter 30 may be calculated.
  • a high pressure fall entails that the pressure of the fuel flow after the pre-filter 30 is significantly lower than the pressure before the pre-filter 30. Such a high pressure fall may indicate that the pre-filter 30 is clogged, and thus hampers the supply of fuel through the pre-filter 30. Clogging may be caused by paraffinated fuel, and thus information about pressure fall may be used to identify whether there is a risk of fuel paraffination.
  • the first and the second pressure sensor 74, 76 are connected to the control device 42 via the CAN-bus 44.
  • the transfer pump 28 is reversible since its electrical engine Ml may change its rota- tional direction.
  • the transfer pump 28 is controlled via the control device 42 to change direction, when a risk of fuel paraffination has been identified.
  • the valve 70 is steered into its second position, and when the transfer pump's 28 direction changes, air is thus sucked via the air filter 71 through the first fuel conduit 36.
  • the pre-filter 30 and the first fuel pipe 36 are emptied of fuel, which fuel is led to the second fuel tank 22.
  • the fuel from the first fuel conduit 36 and the pre-filter 30 is pressed through the coarse mesh sieve 52 of the second fuel tank 22 by the transfer pump 28, which removes any clogging particles.
  • the first original position if the valve 70 is main- tained, so that fuel is sucked from the first fuel tank 20 through the first fuel conduit 36 and the pre-filter 30, and pressed through the coarse mesh sieve 52 when the transfer pump's 28 direction is changed.
  • the warm fuel in the first fuel tank 20 may thus dissolve any potential paraffinated fuel occurring in the first fuel conduit 36, in the pre- filter 30 and in the coarse mesh sieve 52 when the transfer pump's 28 direction is changed.
  • the valve 70 is then steered to its second position, so that the first fuel conduit 36 and the pre-filter 30 are emptied of fuel, while a predetermined fuel level is maintained in the first fuel tank 20.
  • the degree of clogging of the coarse mesh sieve 52 is obtained by determining the relationship between the operation of the transfer pump 28 and the fuel flow in the first fuel conduit 36, according to the description above.
  • the control device 42 determines whether there is a risk of paraffination and controls the transfer pump 28 accordingly.
  • Fig. 3 shows a coupling diagram for a fuel system 4 for a combustion engine 2 according to a second embodiment of the present invention.
  • the fuel system 4 is identical to the fuel system 4 described in Fig. 2, except that the valve 70 and the air filter 71 are missing, and that the first fuel conduit 36 is arranged so that it opens out, at one end, into the first fuel tank's 20 upper part. In this manner the first fuel conduit 36 is connected with air existing in the first fuel tank 20.
  • the transfer pump 28 is controlled via the control device 42 to change direction when a risk of fuel paraffination has been identified. When the transfer pump's 28 direction is changed, air is thus sucked from the first fuel tank 20 through the first fuel conduit 36.
  • the pre-filter 30 and the first fuel pipe 36 are emptied of fuel, which fuel is led to the second fuel tank 22.
  • the fuel from the first fuel conduit 36 and the pre-filter 30 is pressed by the transfer pump 28 through the coarse mesh sieve 52 of the second fuel tank 22, which removes any clogging particles from the coarse mesh sieve 52. In this way, the risk of paraffinated fuel causing stops in the first fuel conduit 36 or causing clogging of the pre-filter 30, and/or the coarse mesh sieve 52, is reduced.
  • Fig. 4a shows a flow chart of a method to reduce the risk of operational disturbances caused by paraffinated fuel in the fuel system 4 according to one embodiment of the present invention.
  • the fuel system 4 comprises a first fuel tank 20, a second fuel tank 22, a first fuel conduit 36 arranged in connection with the first fuel tank 20 and the second fuel tank 22, a second fuel conduit 40 arranged in connection with the first fuel tank 20, a main feeding pump 26, arranged to feed fuel from the first fuel tank 20 through the second fuel conduit 40 to a high pressure system 19, a transfer pump 28, arranged to feed fuel from the second fuel tank 22 to the first fuel tank 20 via the first fuel conduit 36, and a pre-filter 30 arranged downstream of the transfer pump 28.
  • the method according to the invention comprises the step SlOl to decide whether there is a risk of fuel paraffination. Further, the method comprises the step SI 02 to change the direction of the transfer pump 28 in case of a risk of paraffination, so that the flow direction through a pre-filter 30 and the first fuel conduit 36 is reversed.
  • the transfer pump's 28 direction is changed by changing the rotational direction of an electrical engine Ml, operating the transfer pump 28.
  • Fig. 4b shows a flow chart of a method to reduce the risk of operational disturbances caused by paraffinated fuel in the fuel system 4 according to another embodiment of the present invention.
  • the fuel system 4 comprises a first fuel tank 20, a second fuel tank 22, a first fuel conduit 36 arranged in connection with the first fuel tank 20 and the second fuel tank 22, a second fuel conduit 40 arranged in connection with the first fuel tank 20, a main feeding pump 26, arranged to feed fuel from the first fuel tank 20 through the second fuel conduit 40 to a high pressure system 19, a transfer pump 28, arranged to feed fuel from the second fuel tank 22 to the first fuel tank 20 via the first fuel conduit 36, and a pre-filter 30 arranged downstream of the transfer pump 28.
  • the method comprises the step S201 to identify the outdoor temperature of the environment in which the vehicle 1 (displayed in Fig. 1) is located, by reading a first temperature sensor 60 connected to a control device 42. Further, in step S202 the pressure fall over the pre-filter 30 is identified, by reading a first and a second pressure sensor 74, 76 arranged on both sides of the pre-filter 30. The first and the second pressure sensor 74, 76 are connected to the control device 42. By identifying the pressure fall over the pre-filter 30, an indication of whether the pre-filter 30 is clogged is provided. Clogging may be caused by paraffinated fuel. The method also comprises the step S203 to decide whether there is a risk of fuel paraffination, based on the identified values of out- door temperature and pressure fall.
  • the transfer pump 28 is in step S204 controlled by the control device 42 to change direction.
  • the transfer pump's 28 direction is changed by changing the rotational direction of an electrical engine Ml, operating the transfer pump 28.
  • fuel which is in the pre-filter 30 and the first fuel conduit 36 is fed with the transfer pump 28 to the second fuel tank 22.
  • the transfer pump 28 With the transfer pump 28, the fuel which is fed back to the second fuel tank 22 is pressed through a coarse mesh sieve 52, arranged at one end of the first fuel conduit 36 in the second fuel tank 22.
  • the step S201 comprises identifying the temperature of the combustion engine 2 instead of the outdoor temperature.
  • the temperature of the combustion engine 2 is suitably obtained by reading a second temperature sensor 62 connected to the control device 42.
  • the step S201 comprises identifying the outdoor temperature with the temperature sensor 60, and identifying the temperature of the combustion engine 2 with the temperature sensor 62. Both the outdoor temperature and the temperature of the combustion engine 2 should fall below their respective temperature threshold values, in order for decisions to be taken about the existence of a risk of fuel paraffina- tion.
  • the step S202 comprises identifying the relationship between the operation of the transfer pump 28 and the fuel flow in the first fuel conduit 36. This is achieved by a flow meter 72 connected to the control device 42, and by values of power consumption by, and/or power output from, the electrical engine Ml operating the transfer pump 28 by the control device 42. By determining the power consumption by/power output from the electrical engine Ml and the fuel flow in the first fuel conduit 36, an indication may be obtained as to clogging of the pre-filter 30 and/or the coarse mesh sieve 52.
  • the step S204 comprises, in connection with the change of direction of the transfer pump 28, controlling a valve 70, arranged downstream of the pre-filter 30, to a second position, so that the first fuel conduit 36 is connected with air surrounding the fuel system 4.
  • the transfer pump 28 sucks air through the first fuel conduit 36 when the transfer pump's 28 direction is changed, and fuel which is in the first fuel conduit 36 and in the pre-filter 28 is fed to the second fuel tank 22, and through the coarse mesh sieve 52.
  • the temperature sensors 60, 62 may be read both during operation and when the combustion engine 2 is shut down.
  • the pressure sensors 74, 76, the flow meter 72 and the power consumption/power output are suitably read during operation.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Cooling, Air Intake And Gas Exhaust, And Fuel Tank Arrangements In Propulsion Units (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Abstract

The invention pertains to a fuel system for a combustion engine (2), which fuel system (4) comprises a first fuel tank (20), a second fuel tank (22), a first fuel conduit (36) arranged in connection with the first fuel tank (20) and the second fuel tank (22), a second fuel conduit (40) arranged in connection with the first fuel tank (20), a main feeding pump (26), arranged to feed fuel from the first fuel tank (20) through the second fuel conduit (40) to a high pressure system (19), a transfer pump (28), arranged to feed fuel from the second fuel tank (22) to the first fuel tank (20) via the first fuel conduit (36), and a pre-filter (30) arranged downstream of the transfer pump (28). A first electrical engine (Ml) is arranged to operate the transfer pump (28), wherein the transfer pump (28) is reversible, so that the flow direction through the pre-filter (30) and the first fuel conduit (36) may be reversed when a risk of fuel paraffination has been identified. The invention also pertains to a method to reduce the risk of operational disturbances caused by paraffinated fuel in a fuel system.

Description

Fuel system for combustion engine and a method for reducing the risk of operational disturbance caused by paraffined fuel in the fuel system
BACKGROUND OF THE INVENTION AND PRIOR ART
The present invention pertains to a fuel system for a combustion engine, according to the preamble of claim 1. The invention also pertains to a combustion engine with such a fuel system according to claim 11, a vehicle with such a fuel system according to claim 12 and a method to reduce the risk of operational disturbances caused by paraf- finated fuel in a fuel system according to claim 13.
A combustion engine, such as a piston engine, which is driven by diesel or petrol, is equipped with a fuel system to transport fuel from one or several fuel tanks to the combustion engine's injection system. The fuel system comprises one or several fuel pumps which may be driven mechanically by the combustion engine or be driven by an electrical engine. The fuel pumps create a fuel flow and pressure to transport the fuel to an accumulator which may be in the form of a so-called common rail, and fur- ther to the combustion engine's injection system, which supplies the fuel to the combustion engine's combustion chamber. Common rail may be excluded, and the fuel system may instead comprise another form of an injection system, for example a piezo or a unit injection system. Fuel systems also comprise fuel filters for filtration of the fuel before it reaches the combustion engine's injection system. The combustion engine and its injection system are sensitive to contaminations and may be negatively affected if the fuel is too polluted. Contaminations may relate to solid particles, gas or liquid. Even if the fuel only comprises a small amount of contaminations, the consequence may be that the com- bustion engine may not be driven by the fuel. Fuel systems therefore comprise a fuel filter, which both filters away particles and separates water occurring in the fuel. The fuel filter may be a so-called insert fuel filter, which comprises a replaceable filter element arranged inside a filter housing. When the outdoor temperature decreases, the fuel inside the fuel system, such as diesel or bio-diesel, may become paraffinated. The temperature at which the fuel is paraffinated depends on the composition of the fuel and may vary between plus 10 degrees to minus 50 degrees for a number of different fuel compositions. In cases where the fuel is inside the fuel filter's filter housing, the paraffination may lead to the fuel filter becoming clogged, which means that the fuel may be unable to reach the combustion engine in case of a cold start. The fuel which is inside the fuel conduits may become paraffinated as well and cause a stop in the fuel conduits. It is therefore desirable to minimise the risk of fuel in the filter housing and fuel conduits becoming paraffinated in cold weather.
According to prior art, a reversible fuel pump may be arranged, to change the direction of the flow in a fuel system, thus emptying fuel conduits of fuel. In the document EP-0186262, a fuel system for a combustion engine is shown, comprising a fuel pump and a two-part fuel tank. When the combustion engine has been shut down, the fuel pump's direction is changed, so that the fuel conduits are emptied of fuel. In this manner, the risk of paraffinated fuel causing a stop in the fuel conduits is reduced. A smaller part of the fuel tank comprises a heater, and when the vehicle is started the smaller part is filled first, so that the fuel may be heated up before it is pumped out into the fuel conduits. The fuel pump in document EP-0186262 thus always changes direction when the combustion engine has been shut down, regardless of whether or not there is a risk of paraffination. Prior art also provides for arranging an electrically controlled reversible fuel pump in order to be able to change the flow direction in a fuel system.
The document US-2010/0031930 shows a fuel system for a combustion engine, comprising an electrically driven fuel pump, which supplies the fuel system's injection system with fuel. The electrically operated fuel pump in a first position supplies fuel from a fuel tank to the engine, and in a second position the fuel pump supplies fuel from the fuel tank to a device for regeneration of the particulate filter. The first and the second positions correspond to different rotational directions in the electrically operated fuel pump.
Despite prior art solutions in the area, there is a need to further develop a fuel system, which reduces the risk of complications and operational disturbances in connection with cold weather.
SUMMARY OF THE INVENTION The objective of the present invention is to achieve a fuel system for a combustion engine which reduces the risk of operational disturbances caused by paraffinated fuel.
Another objective of the invention is to achieve a fuel system for a combustion engine, which reduces the risk of fuel staying in the fuel filter in cold weather.
Another objective of the invention is to achieve a fuel system for a combustion engine, which is flexible and has a broad control interval.
Another objective of the invention is to achieve a fuel system for a combustion engine, which is non-bulky.
Another objective of the invention is to achieve a fuel system for a combustion engine, which facilitates a cold start. These objectives are achieved with a fuel system of the type specified at the beginning, which is characterised by the features specified in the characterising portion of claim 1.
These objectives are also achieved with a combustion engine with such a fuel system according to the characterising portion of claim 11, a vehicle with such a fuel system according to the characterising portion of claim 12 and a method to reduce the risk of operational disturbances caused by paraffinated fuel in a fuel system according to the characterising portion of claim 13. By arranging an electrically controlled reversible transfer pump in a low pressure circuit in the fuel system for a combustion engine, so that the fuel flow through the pre- filter and the first fuel conduit may be reversed when a risk of paraffination of fuel has been identified, a fuel system is achieved, reducing the risk of complications and operational disturbances caused by paraffinated fuel. Suitably, the pre-filter comprises a replaceable filter element, which is arranged inside a filter housing. Preferably, the transfer pump is a low pressure pump. Suitably, the transfer pump's direction is changed when the combustion engine is shut down and there is a risk of paraffination of fuel. In this manner the risk of paraffinated fuel clogging the transfer filter or causing a stop in the first fuel conduit is reduced. A clogged transfer filter and/or a stop in the fuel conduit entails that fuel is not fed to the first fuel tank, which in turn entails that the combustion engine may not be supplied with fuel. By emptying the filter housing and the fuel conduit only when there is a risk of paraffination of the fuel, unnecessary emptying of the filter housing and the fuel conduit is avoided in those cases where there is no risk of paraffination. Alternatively the transfer pump's direction is changed when the combustion engine is in operation and there is a risk of paraffination of fuel.
Suitably, the transfer pump is reversible by changing the rotational direction of the electrical engine connected to the transfer pump.
By connecting the transfer pump to a control device via a CAN-bus, the transfer pump may be steered toward different parameters, such as pressure in the fuel conduits, pressure fall over the fuel filter, temperatures etc. In this manner a fuel system is achieved, which is flexible, which has a broader control interval than prior art and which in this manner allows for a correct fuel supply to the first fuel tank. Preferably a coarse mesh sieve is arranged at one end of the first fuel conduit, located at the bottom of the second fuel tank. The coarse mesh sieve is thus arranged upstream of the transfer pump and the pre-filter. The coarse mesh sieve filters away particles above a predetermined size and is a filtering element which is often subjected to paraf- finated fuel.
Suitably, it is identified whether there is a risk of paraffination by measuring the out- door temperature. Preferably, a first temperature sensor is connected to the control device, to determine the outdoor temperature of the environment where the vehicle is located. The transfer pump may thus preferably be controlled so that its direction is changed when the outdoor temperature is below a certain temperature threshold, corresponding to the temperature at which the fuel becomes paraffinated, and thus indicat- ing that there is a risk of fuel paraffination.
Alternatively, a risk of fuel paraffination is identified by measuring the temperature of the combustion engine. Preferably, a second temperature sensor is connected to the control device to determine the temperature of the combustion engine. Suitably, this is determined by measuring the temperature of the combustion engine's coolant. The temperature of the combustion engine/coolant may indicate whether there is a risk of fuel paraffination. The transfer pump may thus preferably be controlled so that its direction is changed when the combustion engine's temperature is below a certain temperature threshold, corresponding to the temperature at which the fuel becomes paraf- finated, and thus indicating that there is a risk of fuel paraffination.
Alternatively, a risk of fuel paraffination is identified by determining the pressure fall over the pre-filter. Preferably a first pressure sensor is arranged upstream of the pre- filter and a second pressure sensor is arranged downstream of the pre-filter. With these pressure sensors the pressure fall over the pre-filter may be determined, which may indicate when the pre-filter begins to be clogged. Clogging of the pre-filter may depend on wholly or partly paraffinated fuel, and thus the pressure fall over the pre-filter may indicate whether there is a risk of paraffination. The transfer pump may suitably be controlled so that its direction changes when the pressure fall over the pre-filter exceeds a certain pressure fall threshold and thus indicates that there is a risk of fuel paraffination. The pressure sensors are suitably differential pressure sensors and are connected to the control device. The pressure sensors are preferably read when the combustion engine is in operation.
Clogging of the pre-filter may be caused by paraffination, but may also be due to con- taminants in the fuel. In order to determine whether there is a risk of paraffination, preferably the identified pressure fall is combined with the outdoor temperature and/or the combustion engine's temperature. The transfer pump may thus preferably be controlled so that its direction changes when the pressure fall over the pre-filter exceeds a certain pressure fall threshold, at the same time as the outdoor temperature and/or the combustion engine's temperature falls below a certain temperature threshold value and thus indicates that there is a risk of fuel paraffination.
Alternatively a risk of paraffination is identified by determining the relationship between the transfer pump's operation and the fuel flow in the first fuel conduit. Suita- bly, a flow meter is arranged in the first fuel conduit, which flow meter is connected to the control device via the CAN-bus. The power consumption of the electrical engine operating the transfer pump is measured with the help of the control device, which indicates how hard the transfer pump is working. Alternatively, the power output of the electrical engine operating the transfer pump is measured with the help of the con- trol device. A certain power consumption by, or a certain power output from, the electrical engine normally corresponds to a certain fuel flow in the first fuel conduit. Thus, an increased power consumption or an increased power output entails that the fuel flow in the first fuel conduit increases. Should, however, the control device identify an increased power consumption or an increased power output at the same time as the fuel flow in the first fuel conduit remains unchanged, the conclusion may be drawn that the pre-filter and/or the coarse mesh sieve are probably clogged, and that the fuel flow through the first fuel conduit is therefore reduced. The clogging may be due to wholly or partly paraffinated fuel, and thus the relationship between the transfer pump's operation and the fuel flow in the first fuel conduit may indicate that there is a risk of fuel paraffination. The transfer pump may suitably be controlled in such a way, that its direction is changed when the relationship between the transfer pump's operation and the fuel flow in the first fuel conduit indicate that the pre-filter and/or the coarse mesh sieve are clogged. Power consumption and/or power output and fuel flow in the first fuel conduit are preferably read when the combustion engine is in operation. Preferably the flow meter is arranged upstream of the transfer pump and downstream of the coarse mesh sieve. Alternatively the flow meter is arranged downstream of the pre- filter.
Clogging of the pre-filter and/or the coarse mesh sieve may be caused by paraffinated fuel, but may also be due to contaminants in the fuel. In order to determine whether there is a risk of paraffination, preferably the identified relationship between the trans- fer pump's operation and the fuel flow in the first fuel conduit is compared with the outdoor temperature and/or the combustion engine's temperature. The transfer pump may preferably be controlled so that its direction is changed when the relationship between the transfer pump's operation and the fuel flow in the first fuel conduit indicate that the pre-filter and/or the coarse mesh sieve are clogged, at the same time as the outdoor temperature and/or the combustion engine's temperature fall below a certain temperature threshold value.
Alternatively, a risk of fuel paraffination is identified by combining some or all of the above ways. For example, both the outdoor temperature, the temperature of the com- bustion engine, the pressure fall over the pre-filter and the relationship between the transfer pump's operation and the fuel flow in the first fuel conduit may be used to determine whether there is a risk of fuel paraffination.
Preferably the first and/or the second temperature sensor are read when the combustion engine is in operation in order to determine whether there is a risk of fuel paraffination. Suitably, the reading is carried out during operation, specifically when there is a change of temperature zone.
Alternatively, the first and/or the second temperature sensor are read when the com- bustion engine is shut down and the vehicle is at a standstill. Alternatively, the first and/or the second temperature sensor are read both when the combustion engine is in operation and when the combustion engine is shut down and the vehicle is at a standstill. Preferably a valve is arranged in the first fuel conduit downstream of the pre-filter. The valve is normally steered to a first position, entailing that the first fuel conduit is connected with the first fuel tank. The valve may also be steered to a second position, entailing that the first fuel conduit is connected with the air surrounding the fuel system. Suitably, the first fuel conduit is connected with the surrounding air via an air filter. The valve is preferably connected to the control device via the CAN-bus.
Suitably, the valve is steered to its second position when a risk of fuel paraffination has been identified. When the transfer pump's direction is then changed, the transfer pump thus sucks air through the first fuel conduit, and fuel in the first fuel conduit as well as in the pre-filter is supplied to the second fuel tank. The fuel is thus fed through the coarse mesh sieve, which is thus freed of clogging particles. Thus the risk of operational disturbances caused by paraffinated fuel is reduced.
Alternatively, the valve's first position is maintained when it has been identified that there is a risk of fuel paraffination. When the transfer pump's direction is then changed, the transfer pump sucks fuel from the first fuel tank, further through the pre- filter, and then feeds the fuel through the coarse mesh sieve into the second fuel tank. Suitably, a fuel return conduit is arranged in connection with the first fuel tank and the fuel system's high pressure system. Pressurised warm fuel may in this manner be re- turned back to the first fuel tank, instead of being transported to the combustion engine' s combustion chamber. The fuel in the first fuel tank is thus warmer than the fuel in the second fuel tank when the combustion engine is in operation. The warm fuel may thus dissolve any potential paraffinated fuel occurring in the first fuel conduit, in the pre-filter and the coarse mesh sieve when the transfer pump's direction is changed. Preferably, the valve is then steered to its second position, so that the first fuel conduit and the pre-filter are emptied of fuel, and the first fuel tank maintains a predetermined fuel level. Alternatively, the first fuel conduit is arranged so that it opens out, at one end, into the first fuel tank's upper part, above the fuel surface. In this manner the first fuel conduit is connected with air existing in the first fuel tank. When it has been identified that there is a risk of fuel paraffination, and the transfer pump's direction is changed, the transfer pump sucks out air from the first fuel tank through the first fuel conduit, and in this manner the first fuel conduit and the pre-filter are emptied of fuel. The fuel occurring inside the first fuel conduit and the pre-filter is pressed through the coarse mesh, which in this manner is freed of clogging particles. Thus the risk of operational distur- bances caused by paraffinated fuel is reduced.
Preferably, the transfer pump's direction is changed when a risk of fuel paraffination has been identified and the combustion engine is shut down. Alternatively, the transfer pump's direction is changed when there is a risk of paraffination of fuel and the com- bustion engine is in operation.
Suitably, the first fuel tank is adapted to hold a smaller volume than the second fuel tank. This design entails a less bulky first fuel tank, which is easier to arrange inside a chassis with limited space. Thus, a non-bulky fuel system is achieved. Further, a smaller first fuel tank entails that the fuel system may supply fuel to the combustion engine at a lower fuel level, than if the same fuel volume had been supplied to the larger second fuel tank. In this manner a fuel system for a combustion engine is achieved, which entails a flexible regulation of fuel supply and thus avoids operational disturbances with a low fuel level in the fuel tank. Preferably, the first fuel tank holds 20-50 litres and the second fuel tank holds 300-1,000 litres.
Preferably, the main feeding pump is a low pressure pump, which is operated by a second electrical engine. Suitably, the main feeding pump is also reversible. In this manner a more efficient and flexible regulation of fuel supply to the combustion engine is achieved. Suitably, the main feeding pump is arranged in the first fuel tank. In this manner, the main feeding pump is protected from the environment and a natural cooling of the fuel in the first fuel tank is obtained. Alternatively, the transfer pump and the pre-filter are also arranged inside the first fuel tank. With the main feeding pump, the transfer pump, the pre-filter and the valve arranged inside the first fuel tank, a non-bulky fuel system is achieved.
Preferably, the first fuel tank comprises a level sensor to determine the fuel level in the first fuel tank. Suitably, an overflow line is arranged in connection with the first fuel tank and the second fuel tank. When the fuel level in the first fuel tank, determined with the level sensor, exceeds a predetermined level threshold, fuel from the first fuel tank is led via an overflow line to the second fuel tank. Suitably, the overflow line is arranged in connection with the first fuel tank's upper side and the second fuel tank's upper side. Alternatively, the overflow line may be arranged in connection with the first fuel tank' s bottom.
Suitably, the transfer pump is controlled to feed fuel from the second fuel tank to the first fuel tank when the fuel level in the first fuel tank, determined with the level sensor, falls below a predetermined value.
Other advantages of the invention are set out in the detailed description below.
BRIEF DESCRIPTION OF THE DRAWINGS
Below is a description of, as examples, preferred embodiments of the invention with reference to the enclosed drawings, in which:
Fig. 1 shows a schematic side view of a vehicle, comprising a fuel system for a combustion engine according to the present invention,
Fig. 2 shows a coupling diagram for a fuel system according to a first embodiment of the present invention, Fig. 3 shows a coupling diagram for a fuel system according to a second embodiment of the present invention, and
Fig. 4a-4b show flow charts of methods to reduce the risk of operational disturbances caused by paraffinated fuel in a fuel system according to the present invention.
DETAILED DESCRIPTION OF ONE EMBODIMENT ACCORDING TO THE INVENTION
Fig. 1 shows a schematic side view of a vehicle 1, which vehicle which comprises a fuel system 4 for a combustion engine 2 according to the present invention. The combustion engine 2 is connected to a gearbox 6, which is further connected to the driving wheels 8 of the vehicle 1 via a transmission. The vehicle also comprises a chassis 10.
Fig. 2 shows a coupling diagram for a fuel system 4 in a combustion engine 2 according to the present invention. The fuel system 4 comprises several components, whereof a main fuel filter 12, a high pressure pump 14, an accumulator in the form of a so- called common rail 16, and an injection system 18, schematically displayed in the form of a fuel injector, are arranged in the combustion engine 2 (the combustion engine 2 is displayed in Fig. 1). Alternatively, the common rail 16 may be replaced by another form of an injection system 18, e.g. a piezo or a unit injection system. The high pressure pump 14, the common rail 16 and the injection system 18 constitute components in the high pressure system 19 of the fuel system 4. The fuel system 4 also comprises a first fuel tank 20, a second fuel tank 22, a third fuel tank 24, a main feeding pump 26, a transfer pump 28, and a pre-filter 30. These components may be arranged in the vehicle's chassis 10 (the chassis 10 is displayed in Fig. 1). The main fuel filter 12 is arranged downstream of the main feeding pump 26 and upstream of the high pressure pump 14 in the fuel system 4. Further, the fuel system 4 comprises a fuel return conduit 13, through which pressurised warm fuel is returned from the high pressure system 19 of the fuel system 4, back to the first fuel tank 20. All three tanks 20, 22, 24 are connected in their respective upper parts, with a valve device 50, which communicates via an air filter 51 with the surrounding environment. The ventilation conduit 50 ensures that the pressure in the respective tanks 20, 22, 24 is and remains substantially the same, and equal to the ambient air pressure, regardless of how much fuel is in the respective tanks. The air filter 51 prevents contaminants in the surrounding air from penetrating into the ventilation conduit 50 in connection with ventilation of the tanks. The first fuel tank 20 is adapted to hold a smaller volume than the second fuel tank 22 and the third fuel tank 24. The second fuel tank 22 and the third fuel tank 24 correspond to main fuel tanks and hold substantially the same volume, and have a self- regulating flow between each other via a connection conduit 34, arranged between the lower part of the second fuel tank 22 and the third fuel tank 24. The transfer pump 28 is reversible, and according to Fig. 2, arranged between the first fuel tank 20 and the second fuel tank 22. The transfer pump 28 is operated by a first electrical engine Ml and its main task is to supply fuel from the second fuel tank 22 to the first fuel tank 20 via a first fuel pipe 36. The main feeding pump 26 is operated by a second electrical engine M2 and is arranged inside the first fuel tank 20, and is thus protected from the environment and cooled by the fuel. Between the first fuel tank 20 and the second fuel tank 22 an overflow conduit 38 is arranged, so that fuel may be transported across from the first fuel tank 20 to the second fuel tank 22, if the first fuel tank 20 becomes overfilled. The main task of the main feeding pump 26 is to feed the fuel from the first fuel tank 20 via a second fuel conduit 40 through the main fuel filter 12 and further to the high pressure system 19. The fuel is then fed, at a high pressure, to the common rail 16 and further along to the injection system 18. The main feeding pump 26 and the transfer pump 28 are controlled by a control device 42 via a CAN bus 44.
The pre-filter 30 is arranged downstream of the transfer pump 28 and is preferably a fine mesh, water separating filter. At one end of the first fuel conduit 36, located at the second fuel tank 22, a coarse mesh sieve 52 is arranged. The coarse mesh sieve 52 is thus arranged upstream of the transfer pump 28, entailing that the transfer pump 28 sucks fuel through the coarse mesh sieve 52. The coarse mesh sieve 52 filters away particles above a certain predetermined size. The transfer pump 28 then pressurises the fuel, and then feeds it through the pre-filter 30, via the first fuel pipe 36, further along to the first fuel tank 20. The fuel in the first fuel tank 20 has thus passed both a coarse mesh sieve 52 and a fine mesh pre-filter 30, entailing that the main feeding pump 26, which is arranged in the first fuel tank 20, is protected against impurities. By arranging the pre-filter 30 downstream of the transfer pump 28, the fuel is pressed through the pre-filter 30, entailing that the fuel passes through the pre-filter 30 more easily, and the risk that the pre-filter 30 may become clogged is thus reduced.
In the first fuel tank 20, a first level sensor 46 is arranged to identify the fuel level in the first fuel tank 20. When the fuel level in the first fuel tank 20, determined with the level sensor 46, falls below a predetermined level threshold, the transfer pump 28 is controlled to feed fuel from the second fuel tank 22 to the first fuel tank 20. A second level sensor 48 is arranged in the second fuel tank 22 to identify the fuel level in the second fuel tank 22. The first level sensor 46 and the second level sensor 48 are connected to the CAN bus 44 and the control device 42, which controls the transfer pump 28 and the main feeding pump 26. Further, a first temperature sensor 60 is connected to the control device 42. The first temperature sensor 60 provides the control device 42 with the outdoor temperature of the environment where the vehicle 1 (displayed in Fig. 1) is located. A low outdoor temperature may indicate that there is a risk of fuel paraffination. A second temperature sensor 62 is also connected to the control device 42, in order to provide the control device 42 with the temperature of the combustion engine 2 (displayed in Fig. 1). A low temperature of the combustion engine 2 may indicate that there is a risk of fuel paraffination. A valve 70 is arranged downstream of the pre-filter 30 in connection with the first fuel conduit 36. The valve 70 is normally steered to a first position, entailing that the first fuel conduit 36 is connected with the first fuel tank 20. In the valve's 70 second posi- tion, the first fuel conduit 36 is connected with air surrounding the fuel system, via an air filter 71. The air filter 71 prevents contaminants in the surrounding air from penetrating into the first fuel conduit 36 in connection with steering of the valve 70 into its second position. The valve is connected to the control device 42 via the CAN-bus 44.
A flow meter 72, connected to the control device 42, is arranged in the first fuel conduit, upstream of the transfer pump 28, in order to determine the relationship between the work of the transfer pump 28 and the fuel flow in the first fuel conduit 36. With the help of the control device 42, the power consumption of the electrical engine Ml oper- ating the transfer pump 28 may be determined. Alternatively, the power output from the electrical engine Ml operating the transfer pump 28 is determined with the help of the control device 42. The power consumption and/or the power output indicates how hard the transfer pump 26 is working. A certain power consumption or a certain power output corresponds to a certain fuel flow in the first fuel conduit 36. Should the control device 42 identify an increased power consumption, or an increased power output, at the same time as the flow meter 72 identifies a substantially unchanged fuel flow, alternatively a reduced fuel flow, this indicates that the pre-filter 30 and/or the coarse mesh sieve 52 is clogged. The clogging may be due to paraffinated fuel, and thus information about the relationship between the operation of the transfer pump 28 and the fuel flow in the first fuel conduit 36 may be used to indicate whether there is a risk of fuel paraffination.
A first pressure sensor 74 is arranged upstream of the pre-filter 30, and a second pressure sensor 76 is arranged downstream of the pre-filter 30. By measuring the pressure of the fuel flow before and after the pre-filter 30, the difference in pressure, the so- called pressure fall over the pre-filter 30, may be calculated. A high pressure fall entails that the pressure of the fuel flow after the pre-filter 30 is significantly lower than the pressure before the pre-filter 30. Such a high pressure fall may indicate that the pre-filter 30 is clogged, and thus hampers the supply of fuel through the pre-filter 30. Clogging may be caused by paraffinated fuel, and thus information about pressure fall may be used to identify whether there is a risk of fuel paraffination. The first and the second pressure sensor 74, 76 are connected to the control device 42 via the CAN-bus 44.
The transfer pump 28 is reversible since its electrical engine Ml may change its rota- tional direction. The transfer pump 28 is controlled via the control device 42 to change direction, when a risk of fuel paraffination has been identified. The valve 70 is steered into its second position, and when the transfer pump's 28 direction changes, air is thus sucked via the air filter 71 through the first fuel conduit 36. Thus, the pre-filter 30 and the first fuel pipe 36 are emptied of fuel, which fuel is led to the second fuel tank 22. The fuel from the first fuel conduit 36 and the pre-filter 30 is pressed through the coarse mesh sieve 52 of the second fuel tank 22 by the transfer pump 28, which removes any clogging particles. In this way, the risk of paraffinated fuel causing stops in the first fuel pipe 36 or causing clogging of the pre-filter 30 and/or the coarse mesh sieve 52 is reduced. Alternatively, the first original position if the valve 70 is main- tained, so that fuel is sucked from the first fuel tank 20 through the first fuel conduit 36 and the pre-filter 30, and pressed through the coarse mesh sieve 52 when the transfer pump's 28 direction is changed. The warm fuel in the first fuel tank 20 may thus dissolve any potential paraffinated fuel occurring in the first fuel conduit 36, in the pre- filter 30 and in the coarse mesh sieve 52 when the transfer pump's 28 direction is changed. The valve 70 is then steered to its second position, so that the first fuel conduit 36 and the pre-filter 30 are emptied of fuel, while a predetermined fuel level is maintained in the first fuel tank 20.
Since different compositions of fuel (diesel or bio-diesel) become paraffinated at dif- ferent temperatures, it is difficult to determine whether there is a risk of paraffination solely by measuring the outdoor temperature. By combining information about the outdoor temperature and/or the temperature of the combustion engine 2 with information about the degree of clogging in the pre-filter 30 and/or the coarse mesh sieve 52, a better basis for determining whether there is a risk of paraffination is achieved. Infor- mation about the pre-filter' s 30 degree of clogging is obtained by reading the first and the second pressure sensors 74, 76 and/or by determining the relationship between the operation of the transfer pump 28 and the fuel flow in the first fuel conduit 36, accord- ing to the description above. The degree of clogging of the coarse mesh sieve 52 is obtained by determining the relationship between the operation of the transfer pump 28 and the fuel flow in the first fuel conduit 36, according to the description above. The control device 42 determines whether there is a risk of paraffination and controls the transfer pump 28 accordingly.
Fig. 3 shows a coupling diagram for a fuel system 4 for a combustion engine 2 according to a second embodiment of the present invention. The fuel system 4 is identical to the fuel system 4 described in Fig. 2, except that the valve 70 and the air filter 71 are missing, and that the first fuel conduit 36 is arranged so that it opens out, at one end, into the first fuel tank's 20 upper part. In this manner the first fuel conduit 36 is connected with air existing in the first fuel tank 20. The transfer pump 28 is controlled via the control device 42 to change direction when a risk of fuel paraffination has been identified. When the transfer pump's 28 direction is changed, air is thus sucked from the first fuel tank 20 through the first fuel conduit 36. Thus, the pre-filter 30 and the first fuel pipe 36 are emptied of fuel, which fuel is led to the second fuel tank 22. The fuel from the first fuel conduit 36 and the pre-filter 30 is pressed by the transfer pump 28 through the coarse mesh sieve 52 of the second fuel tank 22, which removes any clogging particles from the coarse mesh sieve 52. In this way, the risk of paraffinated fuel causing stops in the first fuel conduit 36 or causing clogging of the pre-filter 30, and/or the coarse mesh sieve 52, is reduced.
Fig. 4a shows a flow chart of a method to reduce the risk of operational disturbances caused by paraffinated fuel in the fuel system 4 according to one embodiment of the present invention. The fuel system 4 comprises a first fuel tank 20, a second fuel tank 22, a first fuel conduit 36 arranged in connection with the first fuel tank 20 and the second fuel tank 22, a second fuel conduit 40 arranged in connection with the first fuel tank 20, a main feeding pump 26, arranged to feed fuel from the first fuel tank 20 through the second fuel conduit 40 to a high pressure system 19, a transfer pump 28, arranged to feed fuel from the second fuel tank 22 to the first fuel tank 20 via the first fuel conduit 36, and a pre-filter 30 arranged downstream of the transfer pump 28. The method according to the invention comprises the step SlOl to decide whether there is a risk of fuel paraffination. Further, the method comprises the step SI 02 to change the direction of the transfer pump 28 in case of a risk of paraffination, so that the flow direction through a pre-filter 30 and the first fuel conduit 36 is reversed. The transfer pump's 28 direction is changed by changing the rotational direction of an electrical engine Ml, operating the transfer pump 28.
Fig. 4b shows a flow chart of a method to reduce the risk of operational disturbances caused by paraffinated fuel in the fuel system 4 according to another embodiment of the present invention. The fuel system 4 comprises a first fuel tank 20, a second fuel tank 22, a first fuel conduit 36 arranged in connection with the first fuel tank 20 and the second fuel tank 22, a second fuel conduit 40 arranged in connection with the first fuel tank 20, a main feeding pump 26, arranged to feed fuel from the first fuel tank 20 through the second fuel conduit 40 to a high pressure system 19, a transfer pump 28, arranged to feed fuel from the second fuel tank 22 to the first fuel tank 20 via the first fuel conduit 36, and a pre-filter 30 arranged downstream of the transfer pump 28. The method comprises the step S201 to identify the outdoor temperature of the environment in which the vehicle 1 (displayed in Fig. 1) is located, by reading a first temperature sensor 60 connected to a control device 42. Further, in step S202 the pressure fall over the pre-filter 30 is identified, by reading a first and a second pressure sensor 74, 76 arranged on both sides of the pre-filter 30. The first and the second pressure sensor 74, 76 are connected to the control device 42. By identifying the pressure fall over the pre-filter 30, an indication of whether the pre-filter 30 is clogged is provided. Clogging may be caused by paraffinated fuel. The method also comprises the step S203 to decide whether there is a risk of fuel paraffination, based on the identified values of out- door temperature and pressure fall. If the pressure fall indicates that the pre-filter 30 is clogged at the same time as the outdoor temperature is below a temperature threshold value, there is deemed to be a risk of paraffination and the transfer pump 28 is in step S204 controlled by the control device 42 to change direction. The transfer pump's 28 direction is changed by changing the rotational direction of an electrical engine Ml, operating the transfer pump 28. In this manner, fuel which is in the pre-filter 30 and the first fuel conduit 36 is fed with the transfer pump 28 to the second fuel tank 22. With the transfer pump 28, the fuel which is fed back to the second fuel tank 22 is pressed through a coarse mesh sieve 52, arranged at one end of the first fuel conduit 36 in the second fuel tank 22. In this manner any clogging particles, such as paraffinated fuel, are removed from the coarse mesh sieve 52. Alternatively, the step S201 comprises identifying the temperature of the combustion engine 2 instead of the outdoor temperature. The temperature of the combustion engine 2 is suitably obtained by reading a second temperature sensor 62 connected to the control device 42. Alternatively, the step S201 comprises identifying the outdoor temperature with the temperature sensor 60, and identifying the temperature of the combustion engine 2 with the temperature sensor 62. Both the outdoor temperature and the temperature of the combustion engine 2 should fall below their respective temperature threshold values, in order for decisions to be taken about the existence of a risk of fuel paraffina- tion.
Alternatively, the step S202 comprises identifying the relationship between the operation of the transfer pump 28 and the fuel flow in the first fuel conduit 36. This is achieved by a flow meter 72 connected to the control device 42, and by values of power consumption by, and/or power output from, the electrical engine Ml operating the transfer pump 28 by the control device 42. By determining the power consumption by/power output from the electrical engine Ml and the fuel flow in the first fuel conduit 36, an indication may be obtained as to clogging of the pre-filter 30 and/or the coarse mesh sieve 52.
Alternatively the step S204 comprises, in connection with the change of direction of the transfer pump 28, controlling a valve 70, arranged downstream of the pre-filter 30, to a second position, so that the first fuel conduit 36 is connected with air surrounding the fuel system 4. In this manner, the transfer pump 28 sucks air through the first fuel conduit 36 when the transfer pump's 28 direction is changed, and fuel which is in the first fuel conduit 36 and in the pre-filter 28 is fed to the second fuel tank 22, and through the coarse mesh sieve 52. The temperature sensors 60, 62 may be read both during operation and when the combustion engine 2 is shut down. The pressure sensors 74, 76, the flow meter 72 and the power consumption/power output are suitably read during operation.
The components and features specified above may within the framework of the invention be combined between different embodiments specified.

Claims

Claims
1. Fuel system for a combustion engine (2), which fuel system (4) comprises a first fuel tank (20), a second fuel tank (22), a first fuel pipe (36) arranged in connection with the first fuel tank (20) and the second fuel tank (22), a second fuel conduit (40) arranged in connection with the first fuel tank (20), a main feeding pump (26), arranged to feed fuel from the first fuel tank (20) through the second fuel conduit (40) to a high pressure system (19), and a transfer pump (28), arranged to feed fuel from the second fuel tank (22) to the first fuel tank (20) via the first fuel conduit (36), charac- terised in that a pre-filter (30) is arranged downstream of the transfer pump (28) and that a first electrical engine (Ml) is arranged to drive the transfer pump (28), wherein the transfer pump (28) is reversible, so that the flow direction through the pre-filter (30) and the first fuel conduit (36) may be reversed when a risk of fuel paraffination has been identified.
2. Fuel system according to claim 1, characterised in that the transfer pump (28) is reversible by changing the rotational direction of its electrical engine (Ml).
3. Fuel system according to any of the previous claims, characterised in that the transfer pump (28) is connected to a control device (42).
4. Fuel system according to any of the previous claims, characterised in that the fuel system (4) comprises a first and a second temperature sensor (60, 62) for the determination of the outdoor temperature and the temperature of the combustion engine (2), respectively.
5. Fuel system according to any of the previous claims, characterised in that a coarse mesh sieve (52) is arranged in the first fuel conduit (36), upstream of the transfer pump (28).
6. Fuel system according to any of the previous claims, characterised in that a flow meter (72) is arranged in the first fuel conduit (36).
7. Fuel system according to any of the previous claims, characterised in that a first and a second pressure sensor (74, 76) are arranged on each side of the pre-filter (30).
8. Fuel system according to any of the previous claims, characterised in that a valve (70) is arranged in the first fuel conduit (36), downstream of the pre-filter (30), wherein the valve (70) in a first position entails that the first fuel conduit (36) is connected with the first fuel tank (20) and in a second position entails that the first fuel conduit (36) is connected with the air surrounding the fuel system.
9. Fuel system according to any of claims 1-7, characterised in that the first fuel conduit (36) is arranged so that it opens out at one end in the upper part of the first fuel tank (20), so that the first fuel conduit (36) is connected with the air in the first fuel tank (20).
10. Fuel system according to any of the previous claims, characterised in that the first fuel tank (20) is adapted to hold a smaller volume than the second fuel tank (22).
11. Combustion engine (2) characterised in that it comprises a fuel system (4) ac- cording to any of the claims 1-10.
12. Vehicle (1) characterised in that it comprises a fuel system (4) according to one of the claims 1-10.
13. Method to reduce the risk of operational disturbances caused by paraffinated fuel in a fuel system (4) for a combustion engine (2), which fuel system (4) comprises a first fuel tank (20), a second fuel tank (22), a first fuel conduit (36) arranged in connection with the first fuel tank (20) and the second fuel tank (22), a second fuel conduit (40) arranged in connection with the first fuel tank (20), a main feeding pump (26), arranged to feed fuel from the first fuel tank (20) through the second fuel conduit (40) to a high pressure system (19), and a transfer pump (28), arranged to feed fuel from the second fuel tank (22) to the first fuel tank (20) via the first fuel conduit (36), characterised by the steps of:
- deciding whether there is a risk of fuel paraffination,
- changing the direction of the transfer pump (28) in case of risk of paraffination, so that the flow direction through the first fuel conduit (36) and a pre-filter (30) arranged downstream of the transfer pump (28) is reversed.
14. Method according to claim 13, characterised in that the method, before the step of deciding whether there is a risk of fuel paraffination, further comprises the step of:
- identifying an outdoor temperature,
15. Method according to any of claims 13 and 14, characterised in that the method, before the step of deciding whether there is a risk of fuel paraffination, further comprises the step of:
- identifying the temperature of the combustion engine (2).
16. Method according to any of claims 13-15, characterised in that the method, before the step of deciding whether there is a risk of fuel paraffination, also comprises the step, when the combustion engine (2) is in operation, of:
- identifying the pressure fall over the pre-filter (30).
17. Method according to any of claims 13-16, characterised in that the method, before the step to decide whether there is a risk of fuel paraffination, also comprises the step, when the combustion engine (2) is in operation, of:
- identifying the relationship between the transfer pump's (28) operation and the fuel flow in the first fuel conduit (36).
18. Method according to any of claims 13-17, characterised in that the method, in connection with the step of changing the direction of the transfer pump (28), also comprises:
- to steer a valve (70) arranged downstream of the pre-filter (30) to a second position, so that the first fuel conduit (36) is connected with the air surrounding the fuel system (4).
PCT/SE2014/050697 2013-06-13 2014-06-10 Fuel system for combustion engine and a method for reducing the risk of operational disturbance caused by paraffined fuel in the fuel system Ceased WO2014200425A1 (en)

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SE1350721A SE537172C2 (en) 2013-06-13 2013-06-13 Combustion engine fuel system, internal combustion engine with such a fuel system, vehicles with such a fuel system and a method for reducing the risk of malfunctioning fuel caused by paraffin fuel in a fuel system

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EP1148233A2 (en) * 2000-04-17 2001-10-24 Volvo Personvagnar AB Method and arrangement for cleaning filters
WO2004037595A1 (en) * 2002-10-18 2004-05-06 Federal-Mogul Corporation Fuel transfer pump and control
US20100024770A1 (en) * 2008-07-31 2010-02-04 Ford Global Technologies, Llc Fuel delivery system for a multi-fuel engine
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EP0186262A1 (en) * 1984-12-06 1986-07-02 Davco Manufacturing Corporation Purge and prime fuel delivery system and method
EP1148233A2 (en) * 2000-04-17 2001-10-24 Volvo Personvagnar AB Method and arrangement for cleaning filters
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US20100024770A1 (en) * 2008-07-31 2010-02-04 Ford Global Technologies, Llc Fuel delivery system for a multi-fuel engine
US20110099983A1 (en) * 2009-10-30 2011-05-05 Shigehiro Ohno Reducing agent injection valve abnormality detection device and abnormality detection method, and internal combustion engine exhaust gas purification system

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