SE1350359A1 - Combustion engine fuel system and a method of replacing filter elements in a fuel system - Google Patents

Description

If fuel remains with the fuel filter, the clean side of the new filter element, which is arranged in the filter housing, risks coming into contact with the polluted fuel, and unfiltered fuel risks being passed on in the fuel lines to the engine.

This can affect the fuel system's injection system or the internal combustion engine's aftertreatment system. A fuel system where fuel is not present in the fuel filter when changing the filter would minimize the risk of impact on the injection system and thereby reduce the risk of malfunctions.

It is previously known to provide a divertable fuel pump to change the flow direction in a fuel system and thus clean the fuel filter. Document US-B2-6619303 discloses a fuel system for an internal combustion engine, which comprises a fuel pump and a fuel filter, which are arranged in a fuel tank. The main task of the fuel pump is to pump fuel through the fuel filter, which filters out pollutants in the fuel. When the fuel filter needs to be cleaned, the direction of the fuel pump changes, so that the flow direction through the fuel filter changes. Fuel is then pumped from the fuel tank via a second fuel line through the fuel filter from the other direction. In this way, contaminants in the fuel filter are transported to the fuel pump and on to a collection container. Document US-B2-6619303 thus shows a method for cleaning a fuel filter by using a reversible fuel pump.

It is also previously known to arrange divertable fuel pumps in order to change the flow direction in a fuel system for safety purposes and thus empty the injection system of fuel. Document US-A-4726335 discloses a fuel system for an internal combustion engine, which comprises two electrically driven fuel pumps, which supply the fuel system injection system with fuel. The fuel pumps are controlled with respect to the fuel requirements of the internal combustion engine. In the event of a risk situation, the direction of the fuel pumps is changed, so that they suck out the fuel present in the injection system and in this way the internal combustion engine stops.

Despite known solutions in the field, there is a need to further develop a fuel system, which reduces the risk of complications and operational disruptions in connection with filter replacement.

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 malfunctions caused by contaminants in the fuel. Another purpose is to prevent unfiltered fuel from being passed on in fuel lines after the filter in connection with the change of fuel filter. Yet another object is to provide a fuel system for an internal combustion engine which, when changing the filter, reduces the risk of contaminated fuel remaining in the fuel filter. Yet another object is to provide a fuel system for an internal combustion engine which prevents the filter changer from coming into direct contact with fuel.

Another object is to provide a fuel system for an internal combustion engine, which reduces the environmental impact of filter replacement.

Another object is to provide a fuel system for an internal combustion engine, which simplifies operation when changing filters.

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. The corresponding objects are also achieved with a method for replacing a filter element in a fuel system according to the characterizing part of claim 11. Corresponding objects are also achieved with an internal combustion engine and a vehicle with such a fuel system.

By arranging at least one reversible fuel pump in a low-pressure circuit in the fuel system of an internal combustion engine, a fuel system is provided which reduces the risk of complications and operational disturbances in connection with filter replacement. Preferably, the fuel filters comprise replaceable filter elements, which are arranged in filter housings. Preferably, the main feed pump is a reversible low pressure pump. When the filter element of the main fuel filter, which is arranged downstream of the main feed pump, needs to be replaced, contaminated, unfiltered fuel may remain with the main fuel filter. When the old filter element is removed from the main fuel filter, the contaminated fuel can flow to the side of the fuel filter that is occupied by filtered fuel. If a new filter element is then arranged at the main fuel filter, the clean side of the new filter element risks coming into contact with the contaminated fuel. This can lead to contaminated fuel reaching the fuel system's injection system, which can thus be affected and the risk of operational disruptions due to contaminated fuel increases.

By changing the direction of the main feed pump before a new filter element is arranged at the main fuel filter, the fuel present at the main fuel filter is sucked out by means of the main feed pump and fed on to the first fuel tank. In this way, a fuel system is allowed, which reduces the risk of contaminated fuel remaining at the fuel filter, and in this way the risk of operational disturbances caused by contaminants in the fuel is reduced.

Preferably, a return line is arranged between the main fuel filter and the second fuel line. Furthermore, a first non-return valve is arranged at the return line, and a second non-return valve is arranged at the second fuel line, downstream of the connection to the return line and upstream of the main fuel filter. When the filter element of the main fuel filter needs to be replaced, the direction of the main feed pump changes and the first and second non-return valves cause the fuel present in the main fuel filter to be sucked out by means of the main feed pump and fed via the return line to the second fuel line. and further to the first fuel tank. In this way, the main fuel filter is substantially emptied when the new filter element is arranged at the main fuel filter and the risk of contaminated fuel coming into contact with the clean side of the new filter element is reduced. In this way, the risk of contaminated fuel affecting the injection system is also reduced.

Preferably, the transfer pump is a reversible low pressure pump. The main task of the transfer pump is to supply the first fuel tank with fuel, which is done by the transfer pump feeding fuel from the second fuel tank through the pre-filter and via the first fuel line on to the first fuel tank. The fuel that reaches the electric motor-controlled main feed pump is thus pre-filtered, which means that the main feed pump is protected against contaminants in an advantageous manner, which reduces the risk of malfunctions of the main feed pump. When the filter element of the pre-filter, which is arranged downstream of the transfer pump, needs to be replaced, contaminated fuel may remain with the pre-filter. When the old filter element is removed from the pre-filter, the contaminated fuel can flow to the side of the pre-filter which is occupied by filtered fuel.

If a new filter element is then arranged in the pre-filter, the clean side of the new filter element risks coming into contact with the contaminated fuel. This can cause contaminated fuel to reach the main feed pump. By changing the direction of the transfer pump before a new filter element is arranged at the pre-filter, the fuel present at the pre-filter is sucked out by means of the transfer pump and fed on to the second fuel tank. In this way, a fuel system is allowed, which reduces the risk of contaminated fuel reaching the main feed pump during filter change, which reduces the risk of malfunctions of the main feed pump caused by contaminants in the fuel. 10 15 20 25 30 Suitably, the main fuel pump is adjustable by changing the direction of rotation of the electric motor connected to the main fuel pump.

Suitably, the transfer pump is also adjustable by changing the direction of rotation of the electric motor connected to the transfer pump.

By changing the pre-filter and / or the main fuel filter on fuel when changing the filter before a new filter element is arranged on the fuel filter, a fuel system is provided which prevents the filter changer from coming into direct contact with fuel, which is beneficial from a health point of view. Without fuel standing at the fuel filter, it will also be easier to change filters, less spillage and pollution, and in this way a fuel system is created, which allows easier handling when changing filters and which reduces the environmental impact when changing filters. Preferably, the fuel filter is emptied of fuel before the old filter element is removed from the filter housing. Alternatively, the old filter element is removed before emptying the fuel filter.

Preferably, the pre-filter comprises a fine-mesh water-separating filter element.

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.

Alternatively, the valve is arranged in its second position when the filter element of the main fuel filter needs to be replaced. In this way, the transfer pump communicates with the second fuel line and the transfer pump can thus suck out the fuel present in the main fuel filter and feed it on to the second fuel tank. In this way, the fuel in the first fuel tank is prevented from being contaminated with contaminated fuel, which allows the main feed pump to be protected from contamination. It is also possible to bypass the pre-filter with a bypass line in this embodiment, so that the transfer pump does not suck the contaminated fuel through the pre-filter on the way to the second fuel tank.

Suitably, the main feed pump, the transfer pump and the valve are connected to a control unit via a 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.

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. In this way a non-bulky fuel system is provided.

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.

Further advantages of the invention will become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, exemplary embodiments of the invention are described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a schematic side view of a vehicle, which includes 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 a first embodiment, Fig. 3 shows a wiring diagram for a fuel system according to a second embodiment, and Fig. 4 shows a flow chart of a method for replacing filter elements in a fuel system according to the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION Fig. 1 shows a schematic side view of a vehicle 1, which vehicle 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 8 of the vehicle 1.

The vehicle also includes a chassis 10.

Fig. 2 shows a wiring diagram for a fuel system 4 of the internal combustion engine 2 according to a first embodiment. The fuel system 4 is of the type commonly referred to as the common rail and comprises several components of which 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 shown in the form of a fuel injector are arranged in the internal combustion engine. Alternatively, the fuel system may 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 located at the vehicle chassis 10. The main fuel filter 12 is located downstream of the main feed pump 26 and upstream of the high pressure pump 14 in the fuel system 4. The main feed pump 26 is a low pressure pump which supplies the high pressure pump 14 with low pressure. Furthermore, the fuel system 4 comprises an backflow line 13, through which excess fuel flows from the injection system 18, common rail 16, high pressure pump 14 and main fuel filter 12 back to the first fuel tank 20. The main fuel filter 12 includes a filter element 15. In this example, the main fuel filter 12 also comprises a filter housing in which the filter element 15 is housed, and which filter housing is formed with connections for the lines which lead the fuel to and from the filter.

The first fuel tank 20 is designed to accommodate a smaller volume than the second fuel tank 22 and also a smaller volume than 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 reversible, driven by a first electric motor M1 and has as its main task 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 second fuel tank 22 if the first fuel tank 20 becomes overfilled lld. 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 reversible, is driven by a second electric motor M2 and has as its main task to feed 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. With high pressure the fuel is then fed to the common rail 16 and further 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 is arranged downstream of the transfer pump 28 and the filter element 31 arranged at the pre-filter 30 is preferably fine mesh. The transfer pump 28 sucks fuel from the second fuel tank 22, pressurizes the fuel and then feeds it through the pre-filter 30, via the first fuel line 36, on to the first fuel tank 20. The main feed pump 26, which is arranged in the first fuel tank 20, is thus protected from contamination.

When the filter element 15 of the main fuel filter 12 needs to be replaced, it is removed from the filter housing. If this has not previously been completely drained from fuel that has not passed the filter, contaminated fuel may remain in the filter housing of the main fuel filter 12. When the old filter element 15 is removed from the main fuel filter 12, unfiltered fuel may flow to the side of the main fuel filter 12. which is intended for filtered fuel. When the new filter element 15 is mounted on the main fuel filter 12, the clean side of the new filter element 15 then risks coming into contact with the contaminated (unfiltered) fuel. This can cause contaminated fuel to reach the fuel system's injection system 18, which can thus be affected and the risk of malfunctions due to contaminated fuel increases. By changing the direction of the main feed pump 26 before a new filter element 15 is arranged at the main fuel filter 12, the fuel present at the main fuel filter 12 is sucked out by means of the main feed pump 26 and fed on to the first fuel tank 20. Preferably, the fuel is already sucked out of the main fuel filter 12. before the filter element 15 is dismantled, but this can also be done after the filter element 15 has been dismantled. In this way, the main fuel filter 12 (filter housing) is substantially emptied when the new filter element 15 is mounted in the main fuel filter 12 and the risk of contaminated fuel coming into contact with the clean side of the new filter element 15 is reduced. In this way, the risk of contaminated fuel affecting the injection system 18 is also reduced.

What has been described above for the main fuel filter 12 also applies correspondingly to the pre-filter 30. In the case where the filter element 31 of the pre-filter 30 needs to be replaced, contaminated fuel can also remain with the pre-filter 30. When the old filter element 31 is removed from the pre-filter 30 it can become contaminated (unfiltered) fuel 10 15 20 25 30 11 flow to the side of the pre-filter 30 which is intended for filtered fuel. If a new tilting element 31 is then mounted on the pre-filter 30, the clean side of the new filter element 31 risks coming into contact with the contaminated fuel. This can cause contaminated fuel to be transported to the first fuel tank 20, which can cause the main feed pump 26 to be affected by contamination. By changing the direction of the transfer pump 28, before a new filter element 31 is arranged on the pre-filter 30, the fuel present in the pre-filter 30 is sucked out by means of the transfer pump 28 and fed on to the second fuel tank 22. In this way, the pre-filter 30 is substantially emptied when the new filter element 31 is mounted on the pre-filter 30 and the risk of contaminated fuel coming into contact with the clean side of the new filter element 31 is reduced. This reduces the risk of contaminated fuel causing malfunctions of the main feed pump 26.

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 the CAN bus 44 and is in a first position so controlled that the transfer pump 28 is connected to the first outlet and thereby communicates with the first fuel line 36. In a second position the valve 32 is controlled so that the transfer pump 28 is connected to the second outlet and thereby communicates with the second fuel line 40. Thus, 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 fuel The fuel level in the first fuel tank 20. A second level 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 wiring diagram for a fuel system 4 according to a second embodiment which largely corresponds to the first embodiment.

In addition to what is described with reference to Fig. 2, a return line 41 is arranged between the main fuel filter 12 and the second fuel line 40. Furthermore, a first non-return valve 43 is arranged at the return line 41, which first non-return valve 43 causes fuel and water can only flow through the return line 41 in the direction from the main fuel filter 12 to the second fuel line 40. At the second fuel line 40, downstream of the connection to the return line 41 and upstream of the main fuel filter 12, a second non-return valve 45 is provided. Since the filter element 15 of the main fuel filter 12 needs to be replaced, the direction of the main feed pump 26 is changed before a new filter element 15 is mounted at the main fuel filter 12. The first and second check valves 43, 45 cause the fuel present at the main fuel filter 12 to be sucked out with by means of the main feed pump 26 and fed via the return line 41 to the second fuel line 40 and further to the first fuel tank 20. In this way the main fuel filter 12 is substantially emptied when the new filter element 15 is arranged at the main fuel filter 12 and the risk of contaminated fuel comes into contact with the clean side of the new filter element 15 is reduced. In this way, the risk of contaminated fuel affecting the injection system 18 is also reduced.

Fig. 4 shows a flow chart of a method for changing filter elements in the fuel system 4. The method comprises the step (a) of changing the direction of rotation of at least one fuel pump 26, 28, so that at least one fuel filter 12, downstream of the fuel pump 26, 28, 30 emptied of fuel. The method further comprises the step (b) of disassembling (removing) a filter element 15, 31 arranged at the fuel filter 12, 30 and the step (c) of mounting (arranging) a new filter element 15, 31 of the fuel filter 12, 30. In this way, the risk of the clean side of the new filter element 15, 31 coming into contact with contaminated fuel is reduced, which reduces the risk of operational disturbances caused by contaminated fuel. According to an embodiment of the method, said fuel filter is the main fuel filter 12, and said fuel pump is the main feed pump 26. According to a second embodiment of the method, said fuel filter is the pre-filter 30, and said fuel pump is the transfer pump 28.

Preferably, step (a) is performed before step (b), but it is also possible to perform step (b) before step (a). Thus, the filter element 15, 31 is first removed from the fuel filter 12, 30, after which the fuel filter 12, 30 is emptied of fuel by changing the direction of rotation of the at least one fuel pump 26, 28. In a further alternative embodiment it is possible to first make the step (a) for draining the main part of the fuel present in the filter, then the step (b) when the filter element 15,31 is removed, and then another step (a ) to drain any fuel that may remain in the filter before performing step (c).

According to the method, the direction of rotation of the fuel pump 26, 28 is preferably changed by changing the direction of rotation of an electric motor M1, I / I2 coupled to the fuel pump 26, 28.

The specified components and features stated above can, within the scope of the invention, be combined between different specified embodiments.

Claims (15)

10 15 20 25 30 14 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 (20), and two fuel pumps, of which 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 in that a first electric motor (M1) is arranged to drive the transfer pump (28) and that a second electric motor (l \ / l2) is arranged to drive the main feed pump (26), a pre-filter (30) is arranged downstream the transfer pump (28) and a main fuel filter (12) are arranged downstream of the main feed pump (26), wherein at least one of the fuel pumps (26, 28) is adjustable, so that the flow direction through at least one of the fuel filters (12, 30) can be reversed. Fuel system according to claim 1, characterized in that the at least one fuel pump (26, 28) is adjustable by changing the direction of rotation of its electric motor (M1, M2). Fuel system according to one of Claims 1 or 2, characterized in that the main feed pump (26) is arranged inside the first fuel tank (20). Fuel system according to one of the preceding claims, characterized in that the transfer pump (28) is arranged inside the first fuel tank (20). Fuel system according to one of the preceding claims, characterized in that the pre-filter (30) is arranged inside the first fuel tank (20). 10 15 20 25 30 15 Fuel system according to one of the preceding claims, characterized in that the pre-filter (30) and the main fuel filter (12) each comprise a replaceable filter element (15, 31). Fuel system according to one of the preceding claims, characterized in that a valve (32) is arranged downstream of the transfer pump (28) and downstream of the pre-filter (30), wherein the valve (32) has 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), so that the transfer pump (28) is connected to the first fuel line (36) when the valve (32) is arranged in a first position and so that the transfer pump (28) is connected to the second fuel line (40) when the valve (32) is arranged in a second position. 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 1-8. Vehicle (1) characterized in that it comprises a fuel system (4) according to any one of claims 1-8. A method of replacing filter elements 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), and two fuel pumps, of which 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 the steps of: a) changing the direction of rotation of at least one fuel pump (26, 28) so that at least one, downstream of the fuel pump (26, 28) is arranged, fuel filter (12, 30) is drained of fuel, b) remove one filter element (15, 31) arranged at the fuel filter (12, 30), and c) arrange a new filter element (15, 31) of the fuel filter (12, 30). A method according to claim 11, characterized in that said fuel filter is the main fuel filter (12), and said fuel pump is the main feed pump (26). Method according to claim 11, characterized in that said fuel filter is the dry filter (30), and said fuel pump is the transfer pump (28). Method according to claim 11, characterized in that step b) is performed before step a). Method according to Claim 11, characterized in that the direction of rotation of the fuel pump (26, 28) is changed by changing the direction of rotation of an electric motor (M1, I1 / I2) connected to the fuel pump (26, 28).