SE540260C2

SE540260C2 - Fuel system and method for indicating water in fuel by use of a conductivity sensor

Info

Publication number: SE540260C2
Application number: SE1550187A
Authority: SE
Inventors: Lind Christoffer; Jonsson Anders
Original assignee: Scania Cv Ab
Priority date: 2015-02-19
Filing date: 2015-02-19
Publication date: 2018-05-15
Also published as: DE102016001599A1; SE1550187A1

Abstract

The present invention relates to a fuel system (4) for an internal combustion engine (2), the fuel system (4) comprising a first fuel pump (16) in fluid connection with a main fuel tank (10) and being arranged to feed fuel from the main fuel tank (10) to a high pressure system (19) arranged to inject fuel to the internal combustion engine (2), and a first fuel filter (18) which is arranged to filter particles and water from the fuel before the fuel enters the high pressure system (19). At least a first sensor (22) for measuring conductivity of the fuel is arranged downstream of the first fuel filter (18) and upstream of the high pressure system (19) to indicate a water content of the fuel after filtration. In this way it is possible to get an indication of too high water content and insufficient filtration capacity of the first fuel filter (18). The invention also relates to an internal combustion engine (2) with such a fuel system, a vehicle (1) with such internal combustion engine (2) and a method to reduce the risk of operational disturbances caused by excess of water in a fuel in the fuel system.

Description

Fuel system and method for indicating water in fuel by use of a conductivity sensor TECHNICAL FIELD The present invention relates to a fuel system for an internal combustion engine and to a internal combustion engine with such a fuel system, a vehicle with such internal combustion engine and a method to reduce the risk of operational disturbances caused by excess of water in a fuel.

BACKGROUND ART An internal 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 internal combustion engine's injection system. The fuel system comprises one or several fuel pumps which may be driven mechanically by the internal 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 further to the internal combustion engine's injection system, which supplies the fuel to the internal 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 at least one or more fuel filters for filtration of the fuel before it reaches the internal combustion engine's injection system.

The internal combustion engine and its injection system are sensitive to contaminations and may be negatively affected if the fuel contains a large amount of contaminations. 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 internal combustion engine may not be driven satisfactorily by the fuel. Further, an excessive amount of water may cause undesired wear and corrosion of components in fuel systems. Fuel systems therefore comprise a fuel filter, which both filters away particles and separates water occurring in the fuel. In today's fuel systems, water separation is a requirement in the low pressure circuit in connection with filtration to enable disturbance free function of for example fuel pumps.

For example WO 2012/023638 A1 shows a device to protect an engine against inflow of water by dropping the engine RPM if water drain does not occur. Water drain is detected by means of a water-in-fuel (WIF)-sensor adapted to detect whether water drain occurs or not, the sensor being installed in a water separator. However, the disclosed system is directed to detect if water drain occurs but does not indicate how well the water drain functions or whether the fuel fed to the fuel system actually contains water or not.

Thus, 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 due to insufficient water separation.

SUMMARY OF THE INVENTION The requirements are increasing both in relation to long service intervals of fuel filters and high efficiency of water separation, but it has been difficult to fulfil both of these requirements. Today, it is common to drive a vehicle until the fuel filter is clogged or nearly clogged, at which point the water separation has long been at an unacceptable level due to the degradation of the filter. This entails driving with aqueous fuel in the injection system, which may cause damages as a consequence. Thus, there is a need for more accurate systems to detect and indicate to the driver whether the fuel in the fuel system contains water or not.

The object of the present invention is thus to improve the current fuel systems by obtaining an earlier indication of the fuel filter's function in respect of water separation.

It is also an object of the present invention to improve the current fuel systems by obtaining an indication of the actual water content of a fuel to be fed into a fuel system and whether the content is acceptable or not.

Another object of the invention is to achieve a fuel system for an internal combustion engine, which reduces the risk of disturbances in fuel systems due to high water content in fuel.

These objectives are achieved with a fuel system of the present invention defined in the appended claims. Especially, the present invention relates to a fuel system for an internal combustion engine, the fuel system comprising a first fuel pump in fluid connection with a main fuel tank and being arranged to feed fuel from the main fuel tank to a high pressure system, which is arranged to inject fuel to the internal combustion engine. The system further comprises a first fuel filter which is arranged to filter particles and water from the fuel before the fuel enters the high pressure system. At least a first sensor for measuring conductivity of the fuel is arranged downstream of the first fuel filter and upstream of the high pressure system to indicate a water content of the fuel after filtration. By using a conductivity sensor, a simple control of the water content can be provided since the conductivity of the fuel increases with increased water content.

Preferably, a second sensor for measuring conductivity of the fuel is arranged upstream of the first fuel filter to indicate a water content of the fuel before filtration. In this way it will be possible to compare the measured conductivity values and get an indication of the performance of the fuel filter.

The fuel system may comprise two or more fuel filters. The first sensor for measuring the conductivity of the fuel is arranged downstream of the first fuel filter and upstream of a second fuel filter. This makes it possible to detect water early in the fuel system, before the water-containing fuel will be in contact with many components in the fuel system.

In one embodiment of the invention, the values measured for the conductivity can be submitted to a control device for further analysis. Thus, the first sensor preferably comprises, or the first and second sensors comprise, means arranged to generate a measuring signal comprising data relating to a measured conductivity value. Also, the first sensor may be, or the first and second sensors may be, connected to a control device, wherein the control device comprises means for receiving the measuring signal from each of the first sensor and/or second sensor, respectively. In this way, it is possible for the control device to use the information from the measurements and thus make calculations usable for control of the fuel system and/or the vehicle.

According to one embodiment, the control device comprises means arranged to compare the received measuring signal from the first sensor with a predetermined conductivity value and create an error code if the measured conductivity value exceeds the predetermined value. In this way the operator of the vehicle may be warned in case of malfunction of the fuel filter. Also, it is possible to store an error code for example in the control device of the vehicle. In this way the error code will be detected by personnel at service of the vehicle. The fuel filter can then be replaced before the water filtration grade has become too low.

According to another embodiment, the fuel system comprises a second sensor for measuring conductivity of the fuel arranged upstream of the first fuel filter to indicate a water content of the fuel before filtration, and wherein the control device comprises means arranged to calculate a water filtration grade of the first fuel filter from the received measuring signal from the first sensor and the received measuring signal from the second sensor and to compare the calculated water filtration grade with a predetermined value for water filtration grade and create an error code if the calculated water filtration grade is lower than the predetermined water filtration grade. In this way a relative performance of the first fuel filter may be detected, i.e. it can be seen if the reduction of water content in the fuel is achieved through filtration.

The control device may be arranged to control the performance of the first fuel pump, wherein the performance is arranged to be dependent on the measured conductivity value and/or the measured water filtration grade. In this way, the operator of the vehicle can be forced to take the vehicle to service and change the fuel filter.

The control device may be adapted to receive the measuring signals continuously. It is also possible that the control device is adapted to receive the measuring signals periodically, i.e. for example at certain intervals or in case of manually controlled random intervals. An example of a random interval is for example at start of the vehicle or for example after filling of fuel.

Preferably, the first sensor and/or second sensor are connected to the control unit via a communication bus. Thus, the conductivity measurements may be made a part of the total control system of the vehicle.

The invention also relates to an internal combustion engine comprising the fuel system as defined above. Further, the invention relates to a vehicle comprising the internal combustion engine as defined above.

Also, the present invention relates to a method to detect the conductivity of the fuel and thus get an indication of the water content of the fuel. Therefore, the method reduces the risk for operational disturbances caused by excessive water content in fuel. Thus, the present invention relates to a method to reduce the risk for operational disturbances caused by excessive water content in fuel in a fuel system for an internal combustion engine, which fuel system comprises a first fuel pump in fluid connection with a main fuel tank containing fuel, the first fuel pump being arranged to feed fuel from the fuel tank to a high pressure system, the high pressure system being arranged to inject fuel to an internal combustion engine, and a first fuel filter being arranged to filter particles and water from the fuel before the fuel is fed to the high pressure system. The method comprises the steps of: a. to carry out conductivity measurement of the fuel downstream of the first fuel filter by means of a first sensor; b. to generate a measuring signal comprising a measured conductivity value to indicate a water content of the fuel downstream of the first fuel filter.

The method may further comprise a step of: c. to carry out conductivity measurements additionally with a second sensor upstream of the first fuel filter and to generate a measuring signal comprising measured conductivity values to indicate a water content of the fuel upstream of the first fuel filter.

Additionally the method may further comprise steps of: d. to communicate the measuring signal or signals to a control device comprising a processing unit, and e. to compare the measuring signal from the first sensor, or the measuring signals from the first and the second sensors with predetermined conductivity values stored in a memory unit of the processing unit, and/or f. to compare the received measuring signals from the first sensor with the received measuring signals from the second sensor to indicate a measured water filtration grade of the first fuel filter and compare the measured water filtration grade with a predetermined water filtration grade stored in a memory unit of the processing unit.

Preferably, the method further comprises steps of: g. to create an error code if the measured conductivity values exceed the predetermined values, and/or h. to create an error code if the measured water filtration grade is lower than the predetermined water filtration grade.

The present invention also relates to a computer program comprising a program code which, when the program code is executed in a computer, achieves that said computer carries out the method as defined above. Further, according to the present invention a computer program product comprising a data storage medium which is readable by a computer is achieved, the computer program code of a computer program according to above being stored on the data storage medium.

The invention and the advantages thereof will be further defined in the following detailed description with reference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a schematic side view of a vehicle, comprising a fuel system for an internal 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. 4 shows a coupling diagram for a fuel system according to a third embodiment of the present invention, Fig. 5 shows a flow chart of a method according to the present invention, and Fig. 6 shows a control device according to the present invention.

DETAILED DESCRIPTION In the fuel systems a fuel pump is arranged in fluid connection with the internal combustion engine and a fuel tank containing fuel. The fuel pump feeds the fuel from the tank to the internal combustion engine and can be driven mechanically. In this case the fuel pump is connected to the internal combustion engine and operated by the engine's driving shaft. In another type of fuel system for internal combustion engines, the fuel pump is instead arranged in connection with the fuel tank and pressurises the fuel via fuel pipes to the engine. In this type of fuel system, the fuel pump is often electrically, pneumatically or hydraulically driven, and is operated independently of the internal combustion engine's driving shaft.

The present invention is suitable for use in connection with both types of fuel pumps and fuel systems, i.e. where the fuel pump is mechanically driven by the engine's driving shaft and the revolutions thereof and where the fuel pump is arranged in connection with the fuel tank and pushes the fuel to the engine. The fuel pump can be e.g. electrically, pneumatically or hydraulically operated, independently of the internal combustion engine's driving shaft.

According to one variant, the fuel system may comprise more than one electrically driven fuel pump. For example, the system comprises a first fuel pump arranged to feed fuel from one or several main tanks (large tanks) further in the fuel system and suitably to a smaller tank, often called a transfer tank. A second pump can then be arranged downstream of the smaller tank to feed fuel from the smaller tank to the engine, via e.g. a high pressure system including a high pressure pump and which is often arranged in connection with the engine. One reason for arranging a smaller tank and for feeding the fuel via this tank is that the fuel may gather in large tanks when driving in an uneven terrain comprising many hills and valleys, so that the fuel armature (the pipe that sucks up the fuel in the tank) may not be able to suck up the fuel if there is relatively little fuel left in the tank.

A first fuel filter, which is arranged to filter particles and water from the fuel before the fuel enters the high pressure system, is arranged downstream of the first fuel pump, which is arranged to feed fuel from the one or several main tanks. In connection with a fuel system comprising only one fuel pump, the filter is arranged downstream of this fuel pump. Also in connection with a fuel system comprising two or more fuel pumps, a fuel filter is arranged at least downstream of the first fuel pump, which is arranged to feed fuel from the one or several main tanks. Alternatively, a fuel filter may be arranged downstream of each pump.

A fuel filter suitable for use in the present fuel system is preferably a filter which comprises a water-separating layer or a membrane with a water-repelling effect, i.e. a membrane through which the smaller fuel molecules may pass, while the water molecules are stopped. Water exists in the fuel partly as "free water", which is easily separated from the fuel, and partly as an emulsion in the fuel, which is harder to separate from the fuel since the water is more finely divided in the emulsion. In the filter water is separated from the fuel. The fuel filter also has a particle collecting layer with the objective of stopping particles in the fuel. The separated water is usually collected in a water container in connection with the filter, and contains in the range of 0.05-1.5 litres. Often the container is placed below the filter and the separated water trickles down into the container due to gravitation. The container is then emptied manually. The water-separating layer or membrane gradually degrades, i.e. the water-repelling effect is impaired, with the consequence that more and more water molecules pass through the membrane. The fuel system may comprise more than one fuel filter, and preferably each of the fuel filters have a capability of separating water.

In Europe and the USA, fuel contains very small amounts of water, in the range of 200 ppm, i.e. 200 x 10<-6>litres per litre of fuel. In countries with high air humidity, the water content may be as high as 2-3%, i.e. representing 20,000-30,000 ppm.

The fuel is pumped with the fuel pump towards and through the fuel filter. In case the fuel pump is electrically driven, the fuel pump has a controllable pump capacity, i.e. the fuel flow may be altered depending on an electrical fuel control signal. The fuel flow naturally varies depending on how much fuel the engine requires, and is normally within the range 0.5-5 litres per minute.

Conductivity is a measure of the ability of a substance to conduct electricity. By conductivity measurements the electrolytes in a solution are measured and thus the ability of the solution to conduct electric current. The conductivity of the fuel increases when water is present in the fuel. Thus, conductivity of the fuel gives an indication of the water content in the fuel. Conductivity may be measured by means of different kinds of conductivity sensors which determine the ionic content of a solution by measuring its conductivity. For example, the conductivity sensor can be a conductivity meter including a probe which is suitable for use in applications including organic compounds. Conductivity sensors are available on the market for example by a company Cole-Parmer<®>, and the sensor may be adapted to be used within a conductivity range of 0 ?S to 200 mS and within a temperature range of -20 to 110°C.

The fuel system of the present invention reduces the risk for water entering the fuel system and the injection system due to the system comprising means for evaluating the water content of the fuel after the filtration. Thus it is possible to indicate an insufficient filter capacity and warn the operator. The means comprises a first sensor for measuring conductivity of the fuel arranged downstream of the first fuel filter and upstream of the high pressure system to indicate a water content of the fuel after filtration. The conductivity of the fuel correlates with the water content: basically, the more water is present in the fuel the higher is the conductivity. The invention will now be described more in detail with reference to the appended drawings.

Fig. 1 shows a schematic side view of a vehicle 1, which vehicle comprises a fuel system 4 for an internal combustion engine 2 according to the present invention. The internal 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 according to one variant of the present invention. The fuel system 4 comprises a first fuel pump 16 in fluid connection with fuel 11 in a main fuel tank 10 via a first fuel conduit 14. The first fuel pump 16 is arranged to feed fuel from the main fuel tank 10 to a high pressure system 19 and can be mechanically or electrically driven. The fuel system may comprise several fuel tanks.

The fuel system comprises a first fuel filter 18 arranged downstream of the first fuel pump 16 arranged to feed fuel from the main tank 10, and upstream of the high pressure system 19, also called an injection system 19. The first fuel filter 18 is arranged downstream of the first fuel pump 16 and is a fine mesh, water separating filter. At one end of the first fuel conduit 14, located in the main fuel tank 10, a coarse mesh sieve 52 is arranged. The coarse mesh sieve 52 is thus arranged upstream of the first fuel pump 16, entailing that the first fuel pump 16 sucks fuel through the coarse mesh sieve 52. The coarse mesh sieve 52 filters away particles above a certain predetermined size. The first fuel pump 16 then pressurizes the fuel and feeds it through the first fuel filter 18, via the first fuel pipe 14, further to the high pressure system 19. The fuel in the fuel tank 10 has thus passed both a coarse mesh sieve 52 and a fine mesh fuel filter 18, entailing that the high pressure system 19 is protected against water and other impurities. By arranging the first fuel filter 18 downstream of the first fuel pump 16, the fuel is pressed through the first fuel filter 18, entailing that the fuel passes through the first fuel filter 18 more easily, and the risk that the first filter 18 becomes clogged is thus reduced.

A container 20 for collecting the separated water from the filter is arranged below the first fuel filter 18. The high pressure system 19 is arranged in the internal combustion engine 2 (illustrated in Fig. 1) or in direct connection with the internal combustion engine 2. The high pressure system 19 comprises a plurality of components including a high pressure pump 30, an accumulator 32 in the form of a so-called common rail and an injection device 34 which are shown more in detail in Fig. 4 of the drawings. Alternatively, the common rail may be replaced by another form of an injection device, e.g. a piezo or a unit injection device.

A first sensor 22 for measuring conductivity is arranged downstream of the first fuel filter 18 and upstream of the high pressure system 19. As shown in more detail in Fig. 2, the first sensor, i.e. a conductivity measurement device, is connected to a communication bus 44, such as CAN-bus, via a connection 41, and preferably, the CAN-bus 44 communicates with a control device 42 of the vehicle. The first sensor 22 is arranged to generate a measuring signal comprising data relating to a measured conductivity value. The control device 42 comprises means for receiving the measuring signal from the first sensor 22. The control device 42 may comprise means arranged to compare the received measuring signal from the first sensor 22 with a predetermined conductivity value and create an error code if the measured conductivity value exceeds the predetermined value. In this way, the operator of the vehicle will get an indication that the fuel filter needs to be changed.

In another variant of the invention as shown in Fig. 3 it is alternatively or additionally to the first variant described in Fig. 2 possible to evaluate the water filtration grade of the first fuel filter. The system in Fig. 3 corresponds to the system in Fig. 2 except that a second sensor 24 for measuring conductivity of the fuel is arranged upstream of the first fuel filter 18 to indicate a water content of the fuel before filtration. The second sensor is also connected to the communication bus 44, such as CAN-bus, via a connection 43, and the CAN-bus 44 communicates with the control device 42 of the vehicle. In this embodiment of the invention, the control device 42 comprises means arranged to calculate a water filtration grade of the first fuel filter 18 from the received measuring signal from the first sensor 22 and the received measuring signal from the second sensor 24. Then the control device 42 is arranged to compare the calculated water filtration grade with a predetermined value for water filtration grade and create an error code if the calculated water filtration grade is lower than the predetermined water filtration grade. In this way it can be controlled that the water filtration level is acceptable, and a relative value for the water filtration capacity of the fuel filter can be obtained. Thus, the accuracy of the system can be further improved. Therefore, it is possible to warn the operator of the vehicle that the filter has an insufficient filtering capacity, whereby the operator is advised to change the filter as soon as possible.

The fuel system may according to one further embodiment of the invention comprise two fuel pumps and two fuel filters and an example of such a fuel system 4 is illustrated in Fig. 4. The fuel system 4 comprises a first fuel pump 16 which is an electrically driven pump by an electrical motor Ml and arranged to feed fuel from a first main fuel tank 10. The system comprises also a second fuel tank 12 and a third fuel tank 13 and a second fuel pump 26. A first fuel filter 18 is arranged downstream of the first fuel pump 16 and upstream of the second fuel pump 26 and the high pressure system 19. A container 20 for collecting the separated water from the filter is arranged below the first fuel filter 18. A second fuel filter 28 is arranged downstream of the second fuel pump 26 and upstream of the high pressure system 19. These components may be arranged in the vehicle's chassis 10 (the chassis 10 is shown in Fig. 1).

The third fuel tank 13 is adapted to hold a smaller volume than the fuel tank 10 and the second fuel tank 12. The fuel tank 10 and the second fuel tank 12 correspond to main fuel tanks and hold substantially the same volume, and have a self-regulating flow between each other via a connection conduit 54, arranged between the lower part of the fuel tank 10 and the second fuel tank 12.

The first fuel pump 16 is arranged between the fuel tank 10 and the third fuel tank 13. The first fuel pump 16 is operated by a first electrical engine Ml and its main task is to feed or supply fuel from the fuel tank 10 to the third fuel tank 13 via a first fuel conduit 14. The second fuel pump 26 is operated by a second electrical engine M2 and is arranged inside the third fuel tank 13, and is thus protected from the environment and cooled by the fuel. The main task of the second fuel pump 26 is to feed the fuel from the third fuel tank 13 via a second fuel conduit 40 through the second fuel filter 28 and further to the high pressure system 19. The fuel is then fed, at a high pressure, to the common rail 32 and further along to the injection device 34.

In a similar manner as in connection with the embodiments shown in Fig. 2 and 3, a first sensor 22 for measuring conductivity is arranged downstream of the first fuel filter 18 and upstream of the high pressure system 19.

The first sensor 22, i.e. a conductivity measurement device, is connected to a communication bus 44, such as CAN-bus, via a connection 41, and preferably, the CAN-bus 44 communicates with a control device 42 of the vehicle. The first sensor 22 is arranged to generate a measuring signal comprising data relating to the measured conductivity value. The control device 42 comprises means for receiving the measuring signal from the first sensor 22. A second sensor 24 for measuring conductivity of the fuel is optionally arranged upstream of the first fuel filter 18 to indicate a water content of the fuel before filtration. The second sensor is also connected to the communication bus 44, such as CAN-bus, via a connection 43, and the CAN-bus 44 communicates with the control device 42 of the vehicle, and the measurement data can be handled in a similar manner as explained above in connection with Fig. 2 and 3. Thus, also in this embodiment of the invention, the control device 42 comprises means arranged to calculate a water filtration grade of the first fuel filter 18 from the received measuring signal from the first sensor 22 and the received measuring signal from the second sensor 24. Then the control device 42 is arranged to compare the calculated water filtration grade with a predetermined value for the water filtration grade and create an error code if the calculated water filtration grade is lower than the predetermined water filtration grade. In this way it can be controlled that the water filtration level is acceptable, and a relative value for the water filtration capacity of the fuel filter can be obtained. Thus, the accuracy of the system may be improved. Therefore, it is possible to warn the operator of the vehicle that the filter has an insufficient filtering capacity, whereby the operator is advised to change the filter as soon as possible.

The second fuel pump 26 and the first fuel pump 16 can also be controlled by the control device 42 via the CAN bus 44. Thus, the control device 42 can be arranged to control the performance of the electrical first fuel pump 16 and/or the second fuel pump 26. Thus, the performance of the first fuel pump 16 and/or the second fuel pump 26 can be arranged to be dependent on the measured conductivity value and/or the measured water filtration grade. This means that if the fuel has conductivity more than a predetermined value and thus contains more water than a desired, the pumping rate of the first fuel pump 16 and/or the second fuel pump 26 may be arranged to be lower than required by the internal combustion engine 2, whereby the rate of the internal combustion engine needs to be lowered and the filter changed as soon as possible.

It is possible that the control device 42 is adapted to receive the measuring signals continuously. Alternatively, the control device 42 is adapted to receive measuring signals periodically at a pre-determined time interval.

It is also possible that additionally the conductivity of the fuel is measured upstream and/or downstream of the second fuel filter 28 by means of a third and/or a fourth sensor (not shown in the drawings). The sensors function in a similar manner as the first and/or the second sensors, and in this way it is also possible to collect information about the filtration capacity of the additional second fuel filter.

Fig. 5 shows a flow chart of a method to reduce the risk of operational disturbances caused by excessive water content in fuel in a fuel system 4 for an internal combustion engine 2. The fuel system 4 comprises a first fuel pump 16 in fluid connection with a main fuel tank 10 containing fuel 11, the first fuel pump 16 being arranged to feed fuel from the main fuel tank 10 to a high pressure system 19, the high pressure system 19 being arranged to inject fuel to an internal combustion engine 2. A first fuel filter 18 is arranged to filter particles and water from the fuel before the fuel is fed to the high pressure system. The method comprises the steps of: a. to carry out a conductivity measurement of the fuel downstream of the first fuel filter 18 by means of a first sensor; b. to generate a measuring signal comprising a measured conductivity value to indicate a water content of the fuel downstream of the first fuel filter 18.

The method further may further comprise a step of: c. to carry out conductivity measurements additionally with a second sensor 24 upstream of the first fuel filter 18 and to generate a measuring signal comprising measured conductivity values to indicate a water content of the fuel upstream of the first fuel filter 18.

Further, the method may comprise steps of: d. to communicate the measuring signal or signals to a control device 42 comprising a processing unit 120, and e. to compare the measuring signal from the first sensor 22, or the measuring signals from the first and the second sensors 22, 24 with predetermined conductivity values stored in a memory unit 121 of the processing unit 120, and/or f. to compare the received measuring signals from the first sensor with the received measuring signals from the second sensor to indicate a measured water filtration grade of the first fuel filter 18 and compare the measured water filtration grade with a predetermined water filtration grade stored in a memory unit 121 of the processing unit 120.

Further, the method may comprise a step of: g. to create an error code if the measured conductivity values exceed the predetermined values, and/or h. to create an error code if the measured water filtration grade is lower than the predetermined water filtration grade.

Overall, the present invention provides a method that reduces the risk for water entering the fuel system. The method of the invention can be arranged to be carried out by any applicable control unit in the vehicle control device, and may e.g. be arranged to be performed by the control device 42. The control device 42 may comprise any relevant control unit 120 in the vehicle control device. The invention can also be implemented by a dedicated controller for conductivity measurement sensors 22, 24.

Generally the control device 42 comprises or is connected to a CAN bus 44, as shown in Fig. 2-4, comprising one or more communication busses to interconnect a number of electronic control units (ECUs), or controllers, and various components of the vehicle 1. Such a control device 42 may comprise a large number of control units. The control device 42 function may be arranged to receive signals from various sensors in the vehicle and thus control the vehicle accordingly. Further, the control of the vehicle can be performed by programmed instructions. These programmed instructions typically include a computer program, which when the program code is executed in a computer, achieves that said computer carries out the desired action such as the method steps of the present invention described above.

The invention further relates to a computer program product comprising a data storage medium which is readable by a computer, the computer program code of a computer program as described above being stored on the data storage medium. The computer program typically forms part of a computer program product. The computer program product comprises an appropriate storage medium with the computer program stored on said storage medium. The digital storage medium may e.g. be any of the group: ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically Erasable PROM), hard disk drive, etc., and may be provided in or in connection with the control device 42, and wherein the computer program is executed by the control device 42. By changing the computer program instructions the vehicle behaviour may thus be adapted to a specific situation.

An example control device 42 is shown schematically in Fig. 6, the control device 42 can in turn comprise a processing unit 120 which may comprise e.g. any suitable type of processor or microprocessor, e.g. a circuit for digital signal processing digital signal processor (DSP), or a circuit with a predetermined specific function (Application Specific Integrated Circuit, ASIC). The processing unit 120 is connected to a memory unit 121 which provides the processing unit 120 e.g. the stored program code and / or the stored data the processing unit 120 needs to perform calculations, such as to determine whether an error code is to be activated. The processing unit 120 is also adapted to store interim or final results of the measurements and/or calculations in the memory unit 121.

Further, the control unit is equipped with devices 122, 123, 124, 125 for receiving and transmitting of in- and output signals. These input and output signals may contain measured data signals as waveforms, pulse, or other attributes, which of the devices 122, 125 for receiving input signals can be detected as information for the use in the processing device. The devices 123, 124 for transmitting output signals are provided to convert the calculation results from the processing unit 120 to output signals for transmission to other parts of the vehicle control device 42 and / or the / the components for which the signals are intended. Each of the connections to the devices for receiving and transmitting of in- and output signals can be one or more of a cable, a data bus such as a CAN bus (Controller Area Network bus), a MOST bus (Media Oriented Systems Transport), or any other bus configuration, or a wireless connection.

The components and features specified above may within the framework of the invention be combined between different embodiments specified.

Claims

1. Fuel system (4) for an internal combustion engine (2), the fuel system (4) comprising a first fuel pump (16) in fluid connection with a main fuel tank (10) and being arranged to feed fuel from the main fuel tank (10) to a high pressure system (19) arranged to inject fuel to the internal combustion engine (2), and a first fuel filter (18) which is arranged to filter particles and water from the fuel before the fuel enters the high pressure system (19), characterized in that at least a first sensor (22) for measuring conductivity of the fuel is arranged downstream of the first fuel filter (18) and upstream of the high pressure system (19) to indicate a water content of the fuel after filtration.

2. Fuel system (4) according to claim 1, characterized in that a second sensor (24) for measuring conductivity of the fuel is arranged upstream of the fuel filter (18) to indicate a water content of the fuel before filtration.

3. Fuel system (4) according to claim 1 or 2, characterized in that the fuel system (4) comprises two or more fuel filters (18, 28), and wherein the first sensor (22) for measuring conductivity of the fuel is arranged downstream of the first fuel filter (18) and upstream of a second fuel filter (28).

4. Fuel system (4) according to any one of claims 1 to 3, characterized in that the first sensor (22) comprises, or the first and second sensors (22, 24) comprise, means arranged to generate a measuring signal comprising data relating to a measured conductivity value.

5. Fuel system (4) according to claim 4, characterized in that the first sensor (22) is, or the first and second sensors (22, 24) are, connected to a control device (42), wherein the control device (42) comprises means for receiving the measuring signal from each of the first sensor (22) and/or second sensor (24), respectively.

6. Fuel system (4) according to claim 5, characterized in that the control device (42) comprises means arranged to compare the received measuring signal from the first sensor (22) with a predetermined conductivity value and create an error code if the measured conductivity value exceeds the predetermined value.

7. Fuel system (4) according to claim 5 or 6, characterized in that the fuel system (4) comprises a second sensor (24) for measuring conductivity of the fuel arranged upstream of the first fuel filter (18) to indicate a water content of the fuel before filtration, and wherein the control device (42) comprises means arranged to calculate a water filtration grade of the first fuel filter (18) from the received measuring signal from the first sensor (22) and the received measuring signal from the second sensor (24) and to compare the calculated water filtration grade with a predetermined value for water filtration grade and create an error code if the calculated water filtration grade is lower than the predetermined water filtration grade.

8. Fuel system (4) according to any one of claims 5 to 7, characterized in that the control device (42) is arranged to control the performance of the first fuel pump (16), wherein the performance is arranged to be dependent on the measured conductivity value and/or the measured water filtration grade.

9. Fuel system (4) according to any one of claims 5 to 8, characterized in that the control device (42) is adapted to receive the measuring signals continuously.

10. Fuel system (4) according to any one of the preceding claims 5 to 9, characterized in that the first sensor (22) and/or second sensor (24) are connected to the control unit (42) via a communication bus (44).

11. Internal combustion engine (2), characterized in that it comprises the fuel system (4) according to any one of the claims 1-10.

12. Vehicle (1), characterized in that it comprises the internal combustion engine (2) according to claim 11.

13. Method to reduce the risk for operational disturbances caused by excessive water content in fuel in a fuel system (4) for an internal combustion engine (2), which fuel system (4) comprises a first fuel pump (16) in fluid connection with a main fuel tank (10) containing fuel (11), the first fuel pump (16) being arranged to feed fuel from the main fuel tank (10) to a high pressure system (19), the high pressure system (19) being arranged to inject fuel to an internal combustion engine (2), and a first fuel filter (18) being arranged to filter particles and water from the fuel (11) before the fuel (11) is fed to the high pressure system (19), characterized by the steps of: a. to carry out conductivity measurement of the fuel (11) downstream of the first fuel filter (18) by means of a first sensor (22); b. to generate a measuring signal comprising a measured conductivity value to indicate a water content of the fuel (11) downstream of the first fuel filter (18).

14. Method according to claim 13, wherein the method further comprises a step of: c. to carry out conductivity measurements additionally with a second sensor (24) upstream of the first fuel filter (18) and to generate a measuring signal comprising measured conductivity values to indicate a water content of the fuel (11) upstream of the first fuel filter (18).

15. Method according to claim 13 or 14, wherein the method further comprises steps of: d. to communicate the measuring signal or signals to a control device (42) comprising a processing unit (120), and e. to compare the measuring signal from the first sensor (22), or the measuring signals from the first and the second sensors (22, 24) with predetermined conductivity values stored in a memory unit (121) of the processing unit (120), and/or f. to compare the received measuring signals from the first sensor (22) with the received measuring signals from the second sensor (24) to indicate a measured water filtration grade of the first fuel filter (18) and compare the measured water filtration grade with a predetermined water filtration grade stored in a memory unit (121) of the processing unit (120).

16. Method according to claim 15, wherein the method further comprises a step of: g. to create an error code if the measured conductivity values exceed the predetermined values, and/or h. to create an error code if the measured water filtration grade is lower than the predetermined water filtration grade.

17. A computer program comprising a program code which, when the program code is executed in a computer, achieves that said computer carries out the method according to any of the claims 13-16.

18. A computer program product comprising a data storage medium which is readable by a computer, the computer program code of a computer program according to claim 17 being stored on the data storage medium.