SE1350357A1 - Combustion engine fuel system and method for handling water contained in fuel in a fuel system - Google Patents

Abstract

SUMMARY A fuel system (4) for an internal combustion engine (2) comprises a first fuel tank (20), a second fuel tank (22), a first fuel line (36) arranged in communication with the first fuel tank (20) and the the second fuel tank (22), a second fuel line (40) arranged in connection with the first fuel tank (40), a main feed pump (26) and a transfer pump (28). The main feed pump (26) is arranged to supply fuel from the first fuel tank ( 20) through the second fuel line (40) and the transfer pump (28) is arranged to supply fuel from the second fuel tank (22) to the first fuel tank (20) via the first fuel line (36). A water-separating pre-filter (30) is arranged downstream of the transfer pump (28), so that the transfer pump (28) feeds pressurized fuel through the pre-filter (30). A water tank (54) is arranged adjacent to the first fuel tank (20), so that the water tank (54) communicates with the pre-filter (30) and receives water separately from the pre-filter (30). The fuel system also enables a method for handling water present in fuel in a fuel system (4) and which reduces the risk of malfunctions of an internal combustion engine (2) and a motor vehicle. (Fig. 2)

Description

With fuel that includes a lot of water, this is a common problem. Leading the separated water to a separate water tank, which holds a larger volume of water than the fuel filter cavity, would minimize the risk of the fuel filter collapsing due to an overcrowded cavity while driving. In this way, the risk of damage to the internal combustion engine and the injection system would be minimized.

It is previously known to collect separated water in a water tank, which holds a larger volume than the cavity of the water-separating fuel filter. The document EP 2285615 B1 shows a fuel system for an internal combustion engine which comprises a water tank, which is arranged inside a fuel tank.

The fuel system further comprises a water-separating suction filter, which is arranged upstream of a fuel pump. Downstream of the fuel pump, a pressure filter is provided, which also separates water present in the fuel. The separated water from the two filters is led via a pipe to the water tank inside the fuel tank. By arranging the water tank inside the fuel tank, the problem is solved with the water tank freezing at low temperatures at the same time as a larger volume of water can be collected before the water tank has to be emptied.

It is also previously known to collect separated water in the fuel tank, which holds a larger volume than the cavity of the water-separating fuel filter.

Document EP 2078845 A1 discloses a device for preventing fuel, which comprises water, from an internal combustion engine. The fuel system comprises a fuel filter arranged downstream of a fuel supply pump. The fuel filter separates water, which is present in the fuel, and the water is then led back to the fuel tank. As water has a higher density than fuel, the separated water sinks to the bottom of the fuel tank and can thus be emptied by opening a plug in the bottom of the fuel tank. In this way, a larger volume of water can be collected and the risk of damage to the internal combustion engine and its injection system is reduced. 10 15 20 25 30 Despite known solutions in the field, there is a need to further develop a fuel system which reduces the risk of damage to the injection system and internal combustion engine and which reduces the risk of operational disturbances caused by contaminants in the fuel.

SUMMARY OF THE INVENTION The object of the present invention is to provide a fuel system for an internal combustion engine which reduces the risk of damage to the injection system and internal combustion engine and which reduces the risk of malfunctions caused by contaminants in the fuel. Yet another object of the invention is to provide a fuel system for an internal combustion engine which allows easier handling of separated water than the prior art.

Another object is to provide a fuel system which is simple and non-bulky.

These objects are achieved with a fuel system of the kind mentioned in the introduction, which is characterized by the features stated in the characterizing part of claim 1.

These objects are also achieved with an internal combustion engine with such a fuel system according to the characterizing part of claim 11. The purposes of the pilotage are also achieved with a method for regulating a fuel system according to the characterizing part of claim 13. Corresponding purposes are also achieved with an internal combustion engine and a vehicle with such a fuel system.

By arranging a pre-filter downstream of a transfer pump in a low-pressure circuit in a fuel system for an internal combustion engine, a fuel system is provided which reduces the risk of operational disturbances caused by contaminants in the fuel. 10 15 20 25 30 The transfer pump, whose main task is to supply the first fuel tank with fuel, feeds fuel from the second fuel tank through the pre-filter.

The pre-filter filters out particles and separates water, which is present in the fuel.

The filtered fuel is then fed via the first fuel line to the first fuel tank. The fuel, as when the main feed pump is thus pre-filtered and in this way the main feed pump is protected against contamination in the fuel. The separated water is led to a water tank arranged next to the first fuel tank. The water tank holds a larger volume than today's water-separated fuel filters and the water tank thus does not risk being filled in a short time. The risk of the pre-filter collapsing is thus reduced and thus the risk of contaminated fuel and water being fed to the injection system and the internal combustion engine is reduced. In this way, the risk of operational disturbances caused by the contaminants is reduced.

Preferably, a first electric motor is arranged to drive the transfer pump and a second electric motor is arranged to drive the main feed pump. Furthermore, the transfer pump and the main feed pump are suitably low pressure pumps.

Preferably, the pre-filter is a fine-mesh water-separating fuel filter. Such a water-separating pre-filter suitably comprises a filter housing and a filter element, which filter housing has an inlet in connection with the transfer pump, a first outlet in connection with the first fuel line and a second outlet in connection with the water tank.

Conveniently, the water tank is arranged adjacent to the bottom of the first fuel tank, so that a partition wall keeps the water in the water tank and the fuel in the first fuel tank separate. The partition wall alternatively consists of the bottom wall of the first fuel tank. When the water tank is full, it is conveniently emptied through an outlet in the bottom wall of the water tank. As the water and fuel are separated by a partition, there is no risk of fuel being emptied in connection with the emptying of water. In this way, a fuel system 10 is provided for an internal combustion engine, which allows an easier handling of separated water than known technology.

Preferably, an electric heater is arranged next to the water tank.

In this way, a fuel system is provided for an internal combustion engine, which reduces the risk of the accumulated separated water freezing at low temperatures. Alternatively, the water tank is designed to withstand freezing. When the internal combustion engine has started, the fuel, which is returned to the first fuel tank through a backflow line, is heated. The fuel in the first fuel tank is thus heated and because the water tank is arranged adjacent to the first fuel tank, the accumulated water in the water tank can, thanks to the conductivity of the first fuel tank, be heated.

Suitably a drainage valve is arranged at the outlet of the water tank, which drainage valve is connected to a control unit via a CAN bus. Alternatively, a level sensor connected to the CAN bus is arranged in the water tank, so that the driver is warned by means of a light and / or sound signal when the water in the water tank has reached a predetermined level in the water tank. In this way, a fuel system is provided for an internal combustion engine, which allows an easier handling of separated water than known technology.

By arranging the water tank adjacent to the bottom of the first fuel tank, a smaller surface of the space-saving chassis is taken up and a non-bulky fuel system is provided. Furthermore, this placement of the water tank allows it to be more easily accessible and visible.

Conveniently, the water tank comprises a transparent material, which allows the operator to easily identify when the water tank starts to get full and needs to be emptied. In this way, a fuel system is provided for an internal combustion engine, which allows an easier handling of separated water than known technology. Preferably, the first fuel tank is designed to hold a smaller volume than the second fuel tank. Preferably, the first fuel tank holds 20-50 liters and the second fuel tank 300-1000 liters. Conveniently, the water tank holds 1-10 liters. In this way, the space-efficient chassis is utilized in an advantageous manner and a non-bulky fuel system is achieved.

Suitably a valve is arranged downstream of the transfer pump and downstream of the pre-filter. The valve has an inlet in connection with the transfer pump, a first outlet in connection with the first fuel line and a second outlet in connection with the second fuel line, so that the transfer pump is connected to the first fuel line when the valve is arranged in a first position. and so that the transfer pump is connected to the second fuel line when the valve is arranged in a second position. In this way, the first fuel tank can be bypassed and the transfer pump can supply fuel from the second fuel tank to the second fuel line, downstream of the first fuel tank and the main feed pump, and on to the internal combustion engine.

Preferably, the main feed pump, the transfer pump and the valve are connected to the control unit via the CAN bus. In this way a compact fuel system is achieved, which is easy to control and in this way allows a correct fuel supply to the internal combustion engine.

By arranging the main feed pump in the first fuel tank, the main feed pump is protected from the environment and has a natural cooling of the fuel in the first fuel tank. Alternatively, the transfer pump, pre-filter and valve are also arranged inside the first fuel tank. With the main feed pump, transfer pump, pre-filter and valve arranged inside the first fuel tank, a non-bulky fuel system is provided.

Additional features and advantages of the invention will become apparent from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS In the following, as an example, a preferred embodiment of the invention is described with reference to the accompanying drawings, in which: Fig. 1 shows a schematic side view of a vehicle, which comprises a fuel system for an internal combustion engine according to the present invention, Fig. 2 shows a wiring diagram for a fuel system according to the present invention, and Fig. 3 shows a flow chart of a method for handling water present in fuel in a fuel system according to the present invention.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION Fig. 1 shows a schematic side view of a vehicle 1 which comprises a fuel system 4 for an internal combustion engine 2. The internal combustion engine 2 is connected to a gearbox 6, which is connected to the drive wheel of the vehicle 1 via a drive wheel. The vehicle also includes a chassis 10.

Fig. 2 shows a wiring diagram for the fuel system 4. The fuel system 4 comprises several components, of which a main fuel filter 12, a high-pressure pump 14, an accumulator in the form of so-called common rail 16 and an injection system 18 are schematically shown in the form of a fuel injector. arranged on the internal combustion engine 2. Alternatively, the common rail 16 can be replaced by another form of injection system, for example piezo or unit injection system. The fuel system 4 also comprises a first fuel tank 20, a second fuel tank 22, a third fuel tank 24, a main feed pump 26, a transfer pump 28, a pre-filter 30 and a valve 32. These components may be arranged at the vehicle chassis 10. The main fuel filter 12 is arranged downstream of the main feed pump 26 and upstream of the high pressure pump 14 in the fuel system 4. Furthermore, the fuel system 4 comprises a backflow line 13, through which excess fuel flows back from the injection system 18, the common rail 16, the high pressure fuel pump and the first fuel pump 14. 20.

All three tanks 20, 22, 24 are in their respective upper parts connected to a ventilation duct 50 which communicates with the surroundings via an air filter 51. The ventilation line 50 ensures that the pressure in each tank 20, 22, 24 is and remains substantially the same and equal to the ambient air pressure regardless of how much fuel is in each tank. The air filter 51 prevents contaminants in the ambient air from entering the vent line 50 in connection with the ventilation of the tanks.

The first fuel tank 20 is designed 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 hold substantially the same volume and have a self-regulating flow between each other through a connecting pipe 34 arranged between the lower part of the second fuel tank 22 and the third fuel tank 24. According to Fig. 2, the transfer pump 28 is arranged between the first fuel tank 20 and the second fuel tank 22. The transfer pump 28 is driven by a first electric motor M1 and has The main task is to supply fuel from the second fuel tank 22 to the first fuel tank 20 via a first fuel line 36. Between the first fuel tank 20 and the second fuel tank 22 an excess line 38 is arranged so that fuel can be transported over from the first fuel tank 20 to the first. the second fuel tank 22 if the first fuel tank 20 becomes overfilled. The main feed pump 26 is arranged inside the first fuel tank 20 and is thus protected from the environment and cooled by the fuel. The main feed pump 26 is driven by a second electric motor M2 and feeds the fuel from the first fuel tank 20 via a second fuel line 40 through the main fuel filter 12 and on to the high pressure pump 14. At high pressure the fuel is then fed to the common rail 16 and on to the injection system 18. The main feed pump 26 and the transfer pump 28 are controlled by a control unit 42 via a CAN bus 44. The pre-filter 30, which is arranged downstream of the transfer pump 28, is preferably a fine-mesh water-separating fuel filter. In the second fuel tank 22, upstream of the transfer pump 28, a coarse-mesh screen 52 is arranged, through which the transfer pump 28 sucks fuel. The coarse mesh screen 52 filters out particles over a predetermined size. The transfer pump 28 sucks fuel from the second fuel tank 22, pressurizes the fuel and feeds it further through the pre-filter 30. Thereafter, the fuel is fed via the first fuel line 36 to the first fuel tank 20. The water separated in the pre-filter 30 is passed from the pre-filter 30 to a water tank 54, which is arranged adjacent to the bottom of the first fuel tank 20. The water tank 54 holds a larger volume than the water separating pre-filter 30 holds and the water tank 54 thus does not risk being filled in a short time. The risk of the pre-filter 30 collapsing is thus reduced, thereby reducing the risk of contaminated fuel, which includes water, being fed to the injection system 18 and the internal combustion engine 2.

The bottom wall of the water tank 54 has an outlet, in connection with which there is a drainage valve 56 arranged. The drain valve 56 is connected to the control unit 42 via the CAN bus 44. The water tank 54 is transparent, which allows the driver to easily see when the water tank 54 starts to get full and thus determine whether the water tank 54 needs to be emptied before or after a run.

The emptying takes place manually via the drain valve 56 when the vehicle is in a place designated for emptying. According to another embodiment, a level sensor connected to the CAN bus 44 can be arranged in the water tank 54, so that the driver is warned by means of a light and / or sound signal when the water in the water tank 54 has reached a predetermined level in the water tank 54.

Downstream of the pre-filter 30, the valve 32 is arranged, which comprises an inlet in connection with the transfer pump 28, a first outlet in connection with the first fuel line 36 and a second outlet in connection with the second fuel line 40. The valve 32 is connected to CAN bus 44 and is in a first position so controlled that the transfer pump 28 communicates with the first outlet and thereby communicates with the first fuel line 36. In a second position the valve 32 is so controlled that the transfer pump 28 is connected to the second fuel line 40. In this way, the first fuel tank 20 can be bypassed and the transfer pump 28 can supply fuel from the second fuel tank 22 to the second fuel line 40, downstream of the first fuel tank 20 and the main feed pump 26, and further to the internal combustion engine. 2. In the first fuel tank 20, a first level sensor 46 is arranged to identify the fuel level in the first fuel tank 20. A second essence sensor 48 is provided 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 unit 42, which controls the transfer pump 28 and the main feed pump 26. .

Fig. 3 shows a flow chart of a method for handling water present in fuel in the fuel system 4. The method according to the invention comprises the step (a) of separating water present in the fuel, by driving the transfer pump 28 with a first electric motor M1 , so that the transfer pump 28 feeds fuel from the second fuel tank 22 through a pre-filter 30, which is arranged downstream of the transfer pump 28. In the pre-filter 30, the separation thus takes place by separating the water present in the fuel from the fuel. Furthermore, the method comprises step (b) of directing the separated water from the pre-filter 30 to a water tank 54, arranged adjacent to the first fuel tank 20. By designing the water tank 54 with a larger volume than the pre-filter 30, the water tank 54 will not be filled. short time, which means that the internal combustion engine 2 can be driven and thus the vehicle can be driven for a considerable time between the emptying intervals of the water holder 54.

Claims (13)

10 15 20 25 30 11 PATENT REQUIREMENTS A fuel system for an internal combustion engine (2), which fuel system (4) comprises a first fuel tank (20), a second fuel tank (22), a first fuel line (36) arranged in connection with the first fuel tank (20) and the second fuel tank (22), a second fuel line (40) arranged in connection with the first fuel tank (40), a main feed pump (26) and a transfer pump (28), wherein the main feed pump (26) is arranged to supply fuel from the first fuel tank (20) through the second fuel line (40) and wherein the transfer pump (28) is arranged to supply fuel from the second fuel tank (22) to the first fuel tank (20) via the first fuel line (36), characterized by that a water-separating pre-filter (30) is arranged downstream of the transfer pump (28), so that the transfer pump (28) supplies pressurized fuel through the pre-filter (30), and that a water tank (54) is arranged in connection with the first the fuel tank (20), so that the water tank (54 ) communicates with the pre-filter (30) and absorbs water separated from the pre-filter (30). Fuel system according to claim 1, characterized in that a first electric motor (l1 / l1) is arranged to drive the transfer pump (28) and that a second electric motor (M2) is arranged to drive the main feed pump (26), Fuel system according to claims 1 or 2, characterized in that the water tank (54) is arranged in connection with the bottom of the first fuel tank (20) so that the separated water in the water tank (54) and the fuel in the first fuel tank (20) are kept. separated. Fuel system according to one of the preceding claims, characterized in that the water tank (54) comprises a transparent material. Fuel system according to one of the preceding claims, characterized in that the bottom wall of the water tank (54) has an outlet, through which outlet the water tank (54) is emptied of water. 10 15 20 25 30 12 Fuel system according to one of the preceding claims, characterized in that a main fuel filter (12) is arranged downstream of the main feed pump (26). Fuel system according to one of the preceding claims, characterized in that the main feed pump (26) is arranged inside the first fuel tank (20). Fuel system according to one of the preceding, characterized in that the transfer pump (28) is arranged inside the first fuel tank (20). Fuel system according to one of the preceding, characterized in that the pre-filter (30) is arranged inside the first fuel tank (20). Fuel system according to one of the preceding claims, characterized in that the first fuel tank (20) is designed to accommodate a smaller volume than the second fuel tank (22). Internal combustion engine (2), characterized in that it comprises a fuel system (4) according to any one of claims 1-10. Vehicle (1) characterized in that it comprises a fuel system (4) according to any one of claims 1-10. A method of handling water present in fuel in a fuel system (4) for an internal combustion engine (2), the fuel system (4) comprising: a first fuel tank (20), a second fuel tank (22), a first fuel line (36) arranged in connection with the first fuel tank (20) and the second fuel tank (22), a second fuel line (40) arranged in connection with the first fuel tank (20), a main feed pump (26) and a transfer pump (28) , wherein the main feed pump (26) is arranged to supply fuel from the first fuel tank (20) through the second fuel line (40) and wherein the transfer pump (28) is arranged to supply fuel from the second fuel tank (22) to the first the fuel tank (20) via the first fuel line (36), 13 characterized by the steps of: a) separating water present in fuel by feeding the transfer fuel from the second fuel tank (22) through a pre-filter (28) with the transfer pump (28) 30), which is arranged downstream of the transfer pump ( 28), b) directing the separated water from the pre-filter (30) to a water tank (54), arranged adjacent to the first fuel tank (20).