SE537126C2 - Fuel - Google Patents

Description

BACKGROUND OF THE INVENTION AND PRIOR ART The present invention relates to a fuel system according to the preamble of claim 1.

The fuel procured at service stations for the operation of internal combustion engines is not completely clean, but it essentially always contains a small amount of pollutants in the form of water, sand, dust and other types of particles. Systems for supplying fuel to an internal combustion engine include at least one fuel filter for filtering out contaminants from the fuel to prevent damaging components of the fuel system. In internal combustion engines equipped with high pressure injection of the fuel, it is extra important to provide good filtration of the fuel to, for example, protect a high pressure pump and injection means from contaminants. The fuel, which is usually diesel oil, is usually filtered in two stages before it is injected at high pressure into the combustion chambers of a diesel engine from an accumulator tank (Common Rail). To filter the fuel, a first filter housing is usually used with a first filter insert which is arranged upstream of a feed pump which sucks fuel from a fuel tank. The task of the first filter insert is to coarsely filter the fuel from coarser particles so that they do not damage the feed pump. Water is separated Life from the fuel in the first filter housing. A second filter housing with a second filter insert is arranged downstream of the feed pump to filter out finer particles in the fuel so that they do not reach and damage the high-pressure pump and the injection means.

Filter inserts should be changed frequently and hoisted at each service case, as the industry over time will have to respond to the filter inserts as they are gradually dropped again. In the case where a filter insert lifts out of a filter housing, an opening is exposed to a return line at a bottom portion of the filter housing. The remaining fuel in the filter housing then flows back to the fuel tank via the return line. However, this drainage of the fuel 1 537 126 in the filter housing does not always work and in such cases there is fuel left in the filter housing when a new filter insert is applied. At least part of the remaining industry in the filter housing is unfiltered. If the drainage does not work satisfactorily, there is a risk that the filtered fuel is passed on in the fuel system and damages sensitive components which are arranged downstream of the filter housing in the fuel line during a subsequent start of the combustion engine.

SUMMARY OF THE INVENTION The object of the present invention is to provide a fuel system where the risk that a filter housing is not emptied of fuel when a filter insert is lifted out of the filter housing is substantially eliminated.

This object is achieved with the fuel system of the kind mentioned in the introduction, which is characterized by the features stated in the can-drawing part of claim 1. When a filter insert is lifted out of a filter housing, an inlet opening to a return line is exposed. Since the inlet opening of the return line is located at a higher level than an upper part of the fuel tank, the remaining fuel in the filter housing normally flows back to the fuel tank, via the return line, at the time when the filter insert is lifted out. However, it has been found that the filter housing is not always emptied of fuel when the filter insert is lifted out and that the reason for this is that air accumulates in the return line and stops the fuel flow. In order for an industry flood to be obtained in the return line, the industry in the return line must be able to flow into the industry tank. A prerequisite for this is the presence of a continuous industry pillar in the return line in connection with the industry tank, which has an upper spirit which is located at a higher level than the industry surface in the industry tank. In the case of air accumulations in the return line, such an industry column is not always obtained. This is especially the case when the industry level in the industry tank is high. This problem is remedied according to the invention by arranging a venting device in the return line. With an appropriately placed venting device, any accumulations of air that obstruct the fuel flow in the return line can be eliminated in a simple and efficient manner. As a result, an industry column can essentially always be created in the return line in connection with the industry tank, which has the capacity to create an industry flood in the return line that eliminates the remaining industry in the filter housing when the filter insert is removed. The risk of unfiltered fuel being passed on to the industry management and causing damage to sensitive components during a subsequent operation is substantially eliminated. According to an embodiment of the present invention, the venting device is arranged inside the fuel tank. If an air accumulation is created inside the return line at the level of the industry surface in the industry tank, the industry flow in the return line ceases. The air accumulation that prevents the fuel flow in the return line is thus covered inside the fuel tank. In order to eliminate this air accumulation, the venting device must thus be arranged inside the fuel tank. Alternatively, a venting device can be arranged in the return line in a position upstream of the fuel tank. In this case, the air in the return line can be eliminated for preventive purposes before it is sucked down and accumulates in the return line inside the fuel tank.

According to an embodiment of the present invention, the venting device is arranged inside the fuel tank at a higher height level than the level of the fuel in the fuel tank as it is filled with fuel to 80%. The problem of stoppages in the return line thus usually arises only when the industry tank is full or substantially full. The return line usually has a vertical stretch down into the industry tank. Since air is lighter than industry, any air accumulates in an upper part of the vertical line of the return line inside the tank. Such air accumulations cause stops in the return line as they are located at the level of the industry level in the tank. Stops in the return line cause damned essentially only when the fuel tank is full or substantially full. Against this background, it is appropriate to arrange the venting device in the return line in a position in the fuel tank so that air in the return line can be released above or just below the industry level when the industry tank is full or almost full.

According to an embodiment of the present invention, the venting device has a design such that it prevents air from being led into the return pipe. The return line should for many reasons not contain air. It is therefore important that air is not sucked into the return line via the deaeration device. The venting device can be adapted to release air from the return line in the event that it exerts a predetermined pressure in the return line. This pressure can be an overpressure that is related to the air pressure inside the industry tank. The air pressure in the fuel tank usually corresponds to the ambient air pressure, as the fuel tank usually has a tank cap with a valve that ships air into the tank as the fuel in the tank is consumed.

According to an embodiment of the present invention, the venting device comprises a rudder having a first spirit connected to the return line and a second free spirit.

With such a rudder, a vent passage can be established between a lamp position in the return line and a lamp position inside the fuel tank. The venting device may comprise a pipe having a curved shape such that it comprises a local minimum portion, which is located at a lower height level than the spirits of the pipe, and that the local minimum portion is adapted to contain fuel. When a filter insert is lifted out of the filter housing, an industry flood is obtained in the return line. When the fuel flow in the return line reaches the venting device, a small amount of the fuel is led into the pipe. This large amount of fuel creates a water gap in the local minimum section that prevents air from penetrating into the return line. When the fuel flow is stopped in the return line, the accumulated air in the return line is pressurized by fuel that is coated upstream of the air collection. The accumulated air acquires an overpressure in relation to the air in the fuel tank. This pressure difference results in the accumulated air in the return line being led out to the air in the fuel tank via the local minimum batch containing fuel.

According to an embodiment of the present invention, the venting device comprises a one-way valve which is arranged in the pipe. The one-way valve may comprise a valve body which is pressed against a valve seat with a resilient force. The valve body can thus only be opened in one direction and against the action of said feed force. The one-way valve thus prevents ambient air in the fuel tank from being led into the return line at the same time. One-way valves also make it possible for accumulations of air that have an overpressure to leave the return line. The free spirit of said tube is advantageously located at a higher level than the first spirit of the tube.

Thus, air from the return line can essentially always be led out (want & industry surface in the branch tank. However, it is possible to discharge accumulated air in the return line to a position just below the industry level in the tank. Collected air in the return line can in this case be received in a position below the industry surface in the industry tank and relaxed in a position above the industry surface in the industry tank.

According to an embodiment of the present invention, the return line has an outlet which is located at a lower height above the surface of the branch where the fuel tank is filled with fuel to 10%. To prevent air from entering the return line via the outlet opening, it must be covered below the surface of the fuel in the tank. The return line should therefore end in connection with a bottom surface of the industry tank. One consequence of this is that the return line results in a great depth in the fuel tank when the fuel tank is completely filled. This creates a relatively large pressure at the return line outlet which must be overcome in order for the industry to be able to be led out of the return line. In this case, there is an obvious risk that any air accumulations in the return line will stop the fuel flow. According to an embodiment of the present invention, the return line is adapted to return the remaining fuel in a filter housing with a filter insert that filters fuel in an industry line comprising a high pressure pump and an accumulator tank. In industrial systems where the fuel is compressed to very high pressure in an accumulator tank (Common Rail), it is extra important that the fuel does not contain particles or water, as it can damage sensitive components such as high-pressure pumps and injection means. Said filter housing may contain a filter insert which is adapted to coarsely filter the fuel during operation before it is led to a feed pump which sucks the fuel from the fuel tank. The fuel injection system of the above-mentioned type usually has two fuel filters, namely a coarse filter which filters the fuel before it is led to a feed pump and a foam filter which filters out smaller particles in the fuel before it is pressurized in a high-pressure pump. Since part of the fuel in the filter housing with the coarse filter is completely unfiltered, it is extra important that all fuel in this filter housing is eliminated via the return line before a new filter insert is applied in the filter housing. The return line can, however, advantageously return fuel from both filter housings. If the filter inserts in both filter housings are replaced at the same time and they are drained by a common return line, it is extra important that the drainage of the fuel in the return line works because completely unfiltered fuel can otherwise be led past both filter housings if the fuel flow in the return line is stopped.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, by way of example, preferred embodiments of the invention are described with reference to the accompanying drawings, in which: Fig. 1 shows a fuel system with a deaeration device according to the present invention, Fig. 2 shows a first embodiment of the deaeration device and Fig. 3 shows a second embodiment of the deaeration device.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Fig. 1 shows an fuel system for an internal combustion engine in the form of a schematically indicated diesel engine 1. The fuel injection system and the diesel engine 1 are advantageously mounted in a heavy vehicle. The fuel system in this case is a so-called Common Rail system and comprises a fuel tank 2 with a fuel line 3 for guiding diesel oil from the fuel tank 2 to the cylinders of the diesel engine 1. The fuel line 3 comprises a first line portion 3a which leads diesel oil from the fuel tank 2 to a first filter housing 5. The first line portion comprises a hand pump 4. A feed pump 6 is arranged in the fuel line 3 to suck diesel oil from the fuel tank 2 to the first filter housing 5 via the first management party 3a. In the filter housing 5, the diesel oil is coarsely filtered with the aid of a schematically shown first filter insert 5a. Any water present in the diesel oil is also separated. The first filter housing 5 comprises an openable lid 5b which is opened in the event that the filter insert 5a is to be replaced.

The coarse-filtered diesel oil is led, via a second line section 3b, to the feed pump 6.

After coarse filtration, the diesel oil is so free from contaminants that the feed pump 6 cannot be damaged. The diesel oil is then led, via a third line portion 3c, to a second filter housing 7. In the second filter housing 7, the diesel oil is finely filtered by means of a schematically shown second filter insert 7a. The second filter housing 7 comprises an openable lid 7b which is opened in the event that the filter insert 7a is to be replaced. The finely filtered diesel oil is led from the second filter housing 7, via a fourth line section 3d, to a high-pressure pump 8. The diesel oil is now completely free of contaminants that can damage the high-pressure pump 8 and other components in the fuel system. The high-pressure pump 8 is adapted to pressurize the diesel oil so that it is fed with a very high pressure into an accumulator tank 9 in the form of a so-called Common Rail. The high pressure in the accumulator tank 9 constitutes a driving cold to enable injection of the diesel oil with a high pressure in the respective engines of the diesel engine 1. The diesel oil is injected into the cylinders of the diesel engine 1 by means of injection means 10. A return line 11 extending between an inlet opening 11a1 in the first filter housing 5 and the fuel tank 2 to allow emptying of residual diesel oil in the first filter housing 5 during the repair work and replacement 5a in the filter housing 5. The return line 11 also comprises an inlet opening 11a2 which enables emptying of remaining diesel oil in the second filter housing 7 during repair work and replacement of the filter insert 7a in the filter housing 7. The return line 11 is also connected to a line portion 11c for returning residual diesel oil not injected by the injectors 10 into the internal combustion engine 1. The return line 11 has an outlet opening 11b which is located at a bottom portion of the fuel tank 2. The return line 11 is provided with venting device 12 in a position inside the fuel tank 2.

In order for the filter inserts 5a, 7a to be able to maintain a good function, they should be replaced relatively frequently. When the filter inserts 5a, 7a are to be replaced, the respective lids 5b, 7b are opened, after which the filter inserts 5a, 7a can be lifted out. As the filter inserts 5a, 7a are lifted from the lower support surfaces in the respective filter housings 5, 7, the inlet openings 11 a1, 11a2 of the return line are exposed in the respective filter housings 5, 7. Since the inlet openings 11 a1, 11a2 of the return line are located at a higher level 2, normally remaining fuel in the filter housings 5, 7 flows back to the fuel tank 2 via the return line 11 when the inlet openings 11a1, 11a2 are exposed. New filter inserts 5a, 7a are applied in the respective filter housings 5, 7, after which the lids 5b, 7b are put in place. It is thus relatively easy to replace the filter inserts 5a, 7a in the filter housings 5, 7. In some cases, accumulations of air can form inside the return line 11. Such air accumulations can stop the flow of remaining diesel oil from the respective filter housings 5, 7 when the filter inserts are lifted out. . At least some of the diesel oil in the filter housings is unfiltered. If unfiltered diesel oil is not diverted from the filter housings 5, 7 in connection with a replacement of filter inserts 5a, 7a, particles and contaminants in the industry can be passed on to the industry management 3, at a subsequent start, causing damage to sensitive components such as the high pressure pump 8 and the injection means 10. .

The outlet opening 1 lb of the return line 11 is located at a height level h1 in the vicinity of a bottom surface in the fuel tank 2. Thus, the outlet opening 1 lb is essentially always coated at a lower level than the fuel level hb in the fuel tank 2. If the outlet opening 1 lb is arranged above the fuel tank 2b some parts of the fuel line 3 can be emptied of diesel oil, which results in it becoming black to start the internal combustion engine 1. As the fuel tank 2 is substantially full, the outlet opening 1 lb is relatively far below the fuel surface hb in the fuel tank 2. In this case a relatively large pressure is created at the outlet port. 1 lb. This is usually not a problem because the fuel column in the return line 11 is normally sufficiently high to push the fuel out of the fuel tank 2. However, air can accumulate inside the return line 11. There is a clamed risk that a continuous fuel column in the return line 11 adjacent the outlet opening 1 lb does not become higher than the fuel level in the tank 2. If this is the case, the fuel flow is stopped in the return line 11 and if the remaining diesel oil is found in the filter housings 5, 7, it is not drained away.

With the aid of the venting device 12, which is thus covered inside the fuel tank 2, a venting of the return line 11 takes place. The venting device 12 is arranged at a height level h2. Thus, accumulations of tuft at this height level h2 in the return line 11 can be led out from the return line 11. Thus, a coherent industry pillar can essentially always be created in the return line 11 which has the capacity to create a flow in the return line 11 so that the filter housings 5, 7 inches on diesel oil . The risk that unfiltered diesel oil 7,537,126 is passed on in industry management 3 and causes damage to sensitive components at a subsequent start is eliminated.

Fig. 2 shows an embodiment of the deaeration device 12. In this case the deaeration device 12 comprises a tube 12a with a first end 12a1 which is connected to the return line 11 and a second free spirit 12a2. The tube 12a has a curved shape so that it comprises a local minimum portion 12a3 which is located at a lower shear level than the rudder spirits 12a1,12a2 The local minimum portion 12a3 is adapted to contain fuel. The first spirit 12a1 of the rudder is covered at a height level h2. The free spirit 12a2 of the tube is located at a higher height level than the height level h2. In the event that the vehicle is refueled and the fuel tank 2 is filled up to a maximum level, the pipe 12 is filled with fuel. Even in cases where diesel oil is led through the return line 11, a certain amount of diesel oil is led into the tube 12. The tube 12 is automatically filled with diesel oil. Since diesel oil has a higher density of air, it accumulates in the minimum portion 12a3. The diesel oil in the minimum portion 12a3 creates a water sludge. Since the pressure in the return line 11 is essentially never lower than the ambient pressure, the liquid laser prevents ambient air from entering the return line 11 via the vent device 12. If air accumulates locally in the return line 11 and stops the flow in the return line 11, the supplied diesel oil upstream of the air accumulation in the return line 11 a pressure on the air accumulation. Thereby, the air accumulation shows a higher pressure than the air in the fuel tank 2, which is thus the pressure of the surroundings. This overpressure results in the accumulated air being able to pass past the liquid sludge in the minimum portion 12a3 and out via the free spirit 12a2 of the rudder. This eliminates the accumulated air in the return line 11. As a result, in most cases a sufficiently high cohesive fuel column can be created in the return line 11 which has the capacity to push diesel oil out of the return line 11 in the fuel tank 2.

Fig. 3 shows an alternative embodiment of the venting device 12. In this case, the venting device comprises a tube 12b having a first end 12b1 which is connected to the return line 11 on a height level h2 and a second free spirit 12b2. The tube 12b has a curved shape so that the free Linden 12b2 is located at a higher height level than the first Linden 12b1. The tube 12 has a one-way valve 12c. The one-way valve 12c is dimensioned so that it opens at a predetermined pressure in the return line 11. However, the one-way valve 12c prevents air from entering the return line 11, via the pipe 12b, even if the pressure in the fuel tank 12 adjacent to the free spirit 12b2 would be higher than inside the return line 11 in connection with the first spirit 12b1 of the rudder. The invention is in no way limited to the embodiments described in the drawings but can be varied freely within the scope of the patent claims. 9

Claims (12)

537 126 Patentkray A fuel system for an internal combustion engine (1), the fuel system comprising a fuel tank (2), a fuel line (3) for guiding fuel from the fuel tank (2) to the internal combustion engine (1), a filter housing (5, 7) comprising a demountable filter insert (5a, 7a) which is adapted to filter the fuel in the fuel line (3) and a return line (11) having an inlet (11ai, 11a2) in the filter housing (5, 7) and an outlet (11b) the fuel tank (2) , wherein the inlet (11ai, 11a2) of the return line is located at a higher level than an upper part of the fuel tank (2) and that the return line (11) is adapted to return the remaining fuel in the filter housing (5, 7) to the fuel tank (2) in the event as the filter insert (5a, 7a) is disassembled, characterized in that the return line (11) comprises a deaeration device (12) which is adapted to discharge air from the return line (11). Fuel system according to claim 1, characterized in that the venting device (12) is arranged inside the fuel tank (2). Fuel system according to claim 2, characterized in that the venting device (12) is arranged inside the fuel tank (2) at a higher bend level (h2) than the fuel level (hb) in the fuel tank where it is filled with fuel to 80%. Fuel system according to any one of the hazardous requirements, characterized in that the venting device (12) is designed so that it prevents air from being led into the return line (11). Fuel system according to one of the preceding claims, characterized in that the venting device (12) is adapted to open and release any air in the return line (11) at the time when it causes a predetermined pressure in the return line (11). Fuel system according to any one of the preceding claims, characterized in that the venting device comprises a pipe (12a, 12b) having a first end (12at, 12b1) connected to the return line (11) and a second free spirit (12a2). , 12b2). Fuel system according to claim 6, characterized in that the venting device comprises a root (12a) having a curved shape so as to comprise a local minimum portion (12a3), as the working position at a lower height level of the pipe spirits (12a1,12a2) and that the local mini-party (12a3) is adapted to contain fuel. 537 126 Fuel system according to claim 6, characterized in that the venting device comprises a one-way valve (12c) which is arranged in the tube (12b). Fuel system according to any one of claims 6-8, characterized in that the free spirit of said tubes (12a2, 12b2) is located at a higher level than the first spirit of the tube (12ai, 12b1). Fuel system according to one of the preceding claims, characterized in that the return line (11) has an outlet (11b) which is located at a lower height level (hi) of the surface of the branch (4) when the fuel tank (2) is filled with fuel to 10% . Fuel system according to any one of the preceding claims, characterized in that the return line (11) is adapted to return residual fuel in a filter housing (5, 7) with a filter insert (5a, 7a) which filters fuel in a fuel line (3) comprising a high pressure pump (8) and an accumulator tank (9). Fuel system according to claim 11, characterized in that said filter housing (5) comprises a filter insert (5a) adapted to coarsely filter the fuel during operation before it is led to a feed pump (6) in the fuel line (3) which sucks the fuel from the fuel tank (2). ). 11 537 126 1/2 5a E 3dN 5b7b 4 11a2 3b3c lib 1 al