Fuel filter for a vehicle

Abstract

Fuel filter for a vehicle, with a housing (2, 3) for receiving a fuel-permeable filter body (7), and with a vent line (11) for venting fuel before it exits the housing (2, 3), wherein an inlet opening (12) for the vent line (11) is spaced apart from an end region of the filter body (7) when the filter body (7) is housed in the housing (2, 3), wherein the inlet opening (12) is spaced apart from an inner wall of a cover element (15), and wherein a distance (14) of the inlet opening (12) from the inner wall of the cover element (15) is less than when the filter body (7) is housed in the housing (2, 3), a distance of the inlet opening (12) to the end region of the filter body (7), characterized by the fact that with the filter body (7) being housed in the housing (2, 3), the inlet opening (12) is formed in a cap (16) coupled to the filter body (7), which at least partially closes off the filter body (7) towards its end area.

Description

[0001] The invention relates to a fuel filter for a vehicle, comprising the features of the preamble of claim 1.

[0002] Bleeding the fuel system may be necessary, in particular, if a clogged fuel filter element has been replaced with a new one, or if there is a leak in the fuel supply system. Air can also enter the fuel supply system if the fuel tank is completely emptied.

[0003] The vent line of a vehicle equipped with a fuel filter is connected to a return line leading to the fuel tank. Either the unfiltered fuel can be vented, or the fuel after it has passed through the filter element. Venting ensures that the fuel exiting the fuel filter does not contain any gas bubbles, which would otherwise prevent the desired injection pressure from being achieved.

[0004] When operating a vehicle with a fuel filter of the type mentioned above, it has sometimes been found that providing fuel to be injected into the vehicle's internal combustion engine takes a comparatively long time.

[0005] US Patent 7,393,455 B1 describes a fuel filter with a filter element, wherein an air volume is located between an outer wall of the filter element and a housing in which the filter element is held. When the fuel filter is operated, the air is compressed, and the fuel level in the housing rises. As the filter element becomes clogged, the fuel level continues to rise. A pressure relief valve opens when the pressure of the compressed air exceeds a threshold. This reduces the air volume in the fuel filter as the filter element becomes clogged. Finally, when the fuel level reaches the upper end of an external space around the filter element, it can be seen that the filter element should be replaced.

[0006] One such fuel filter is shown, for example, in the publications DE 10 2009 043 638 A1 and DE 10 2009 041 298 A1. Further embodiments of fuel filters are shown in EP 1 440 721 A1 and DE 60 2004 006 277 T2.

[0007] The object of the present invention is to create a fuel filter of the type mentioned above which enables a particularly rapid and safe provision of fuel for injection.

[0008] This problem is solved by a fuel filter having the features of claim 1. Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims.

[0009] The fuel filter according to the invention for a vehicle comprises a housing for receiving a fuel-permeable filter element and a vent line for venting fuel before it exits the housing. With the filter element housed in the housing, an inlet opening for the vent line is spaced apart from an end region of the filter element, and the inlet opening is spaced apart from an inner wall of a cover element. The distance between the inlet opening and the inner wall of the cover element is less than the distance between the inlet opening and the end region of the filter element when the filter element is housed in the housing. The inlet opening is thus located closer to the inner wall of the cover element than in a fuel filter known from the prior art.

[0010] The inlet opening is formed in a cap coupled to the filter body, which is housed within the casing. The cap seals off the filter body at least partially towards its end. When the clogged filter body is replaced, the cap is also replaced, so that a new and therefore unclogged inlet opening is provided each time the filter body and cap are changed.

[0011] The distance between the inlet opening and the inner wall of the cover element determines the maximum fill level in the housing when the fuel filter is operating, provided the fuel contains air and is being vented. During operation, the air between the inlet opening and the inner wall of the cover element is compressed to the pressure applied by the pump that supplies fuel to the filter. Because the inlet opening is positioned relatively close to the inner wall of the cover element, any air bubble that forms below the cover element can be largely, and in particular completely, expelled from the housing.Since fuel is virtually incompressible compared to air, only a comparatively small amount of air needs to be compressed before the fuel reaches the desired outlet pressure in the fuel filter, at which point it is delivered to an injection system or a high-pressure pump. This allows fuel to be made available for injection particularly quickly. As a result, the time until injection begins in the internal combustion engine of the vehicle equipped with the fuel filter is significantly reduced.

[0012] The fuel filter is particularly suitable for integration into a fuel supply system that stores high-pressure fuel in a common rail and delivers it to the combustion chamber of an internal combustion engine via an injector. In such a high-pressure system, pressure fluctuations in the injection system are comparatively small compared to a pump-injector system, typically around 5 bar. In contrast, pump-injector systems can experience pressure fluctuations of up to 50 bar. The smaller the pressure fluctuations, the less air contained in the fuel dissolves in the form of tiny air bubbles. Therefore, with low pressure fluctuations, larger air bubbles are present in the fuel, which must be vented through the vent line.

[0013] In an advantageous embodiment of the invention, the distance between the inlet opening and the inner wall of the cover element is less than 10 mm. A further reduction in the size of any air bubble that may form in the fuel filter below the cover element can be achieved if the distance between the inlet opening and the inner wall of the cover element is less than 5 mm.

[0014] If, according to a further advantageous embodiment of the invention, the distance between the inlet opening and the inner wall of the cover element in the axial direction of the vent line is only 1 mm, this achieves a dimension that enables reliable operation of the vent line even when considering manufacturing tolerances occurring in series production. At the same time, a minimal distance between the inlet opening and the inner wall of the cover element is achieved with regard to any air bubble that may form in the fuel filter. This results in a particularly significant reduction in starting time, i.e., a particularly rapid supply of fuel for injection.

[0015] The cover element can be formed by a lid of the housing. This allows for particularly good adjustment of the relative position of the vent line to the cover element, and this relative position is independent of the design of the filter body. In an alternative embodiment, with the filter body housed within the casing, the cover element can be formed by a cap coupled to the filter body, which at least partially seals off the filter body towards its end. In this case, the air extracted from the fuel collects below the cap. This creates a comparatively small collection area for the air bubble.

[0016] The cap can taper towards the inlet opening. This makes it easier to align the inlet opening relative to the vent pipe.

[0017] In a further advantageous embodiment of the invention, at least one rib is formed on a housing lid, which, when the filter body is housed in the housing, is in contact with the cap. Additionally or alternatively, the at least one rib can also be formed on the cap, thus keeping the cap at a distance from the housing lid. The rib ensures that the cap, and therefore the inlet opening, is located at the defined distance from the inner wall of the housing lid. The rib also prevents the filter body and cap from shifting within the housing during operation of the fuel filter. Such shifting could otherwise lead to the inlet opening becoming blocked if the cap came into contact with the inner wall of the lid in the area of ​​the inlet opening.

[0018] Finally, it has proven advantageous if the cover element has a recess aligned with the inlet opening. In this case, the distance of the inlet opening from the inner wall of the cover element is determined by the depth of the recess, which can be formed in the material of the cover element.

[0019] The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the figure description and / or shown in the figures alone, can be used not only in the combination specified in each case, but also in other combinations or on their own, without leaving the scope of the invention.

[0020] Further advantages, features, and details of the invention will become apparent from the claims, the following description of preferred embodiments, and the drawings. These show: Fig. 1. A first embodiment of a fuel filter in which a vent line has a particularly small distance to a cover of a housing of the fuel filter; and Fig. 2 an alternative fuel filter in which an inlet opening for a fuel filter vent line is formed by a cap of a filter body.

[0021] At a Fig. The fuel filter 1 shown for a vehicle consists of a housing formed by a lower part 2 and a cover 3 screwed to the lower part 2. An inlet line 4 is located in a central part of the housing, through which unfiltered fuel enters the housing. The unfiltered fuel is supplied from a fuel tank by a (not shown) fuel pump. At one end of the inlet line 4, the fuel exits into a headspace 5 of the housing, as shown in Fig. 1 is illustrated by flow arrows 6.

[0022] A hollow cylindrical filter element 7 serves to filter the fuel. Fuel can pass through the filter element 7 from the outside via a space formed between the housing and the filter element 7. The filtered fuel thus passes through openings 8, one of which is shown schematically and by way of example, into an outlet line 9, which is also located in the central part of the housing. The filtered fuel then flows through the outlet line 9 to a high-pressure pump (not shown), which supplies a common rail with fuel under high pressure. From the common rail, the filtered fuel passes through injectors into the combustion chambers of an internal combustion engine.

[0023] One possible flow path of the fuel coming from the headspace 5, via the space between the housing and the filter body 7, through the filter body 7 to the through-opening 8, is shown in Fig. 1 illustrated by further flow arrows 10.

[0024] In the central section of the fuel filter is another line, which serves as a vent line 11. The vent line 11 has a small bore at its upper end, serving as an inlet opening 12. Fuel coming from the supply line 4 can enter the vent line 11 through this inlet opening 12, as indicated by a further flow arrow 13 in Fig. Figure 1 illustrates the vent line 11, which leads back into the (not shown) fuel tank.

[0025] The inlet opening 12 of the vent line 11 has a very small distance 14 to a screw head 15 formed integrally with the cover 3. This distance 14 determines the fuel level in the fuel filter 1 when it is in operation, provided the fuel contains air bubbles. When the fuel filter 1 is operating, the fuel pump moves fuel from the fuel tank through the fuel filter 1 and establishes a fuel delivery pressure there. The resulting air volume from the fuel venting, the height of which corresponds to the distance 14 between the inlet opening 12 and the inner wall of the screw head 15 formed integrally with the cover 3, is, when the fuel filter 1 is in operation, at precisely the pressure level that corresponds to the outlet pressure of the vented fuel in the outlet line 9.

[0026] After the fuel pump switches off, this air volume expands to a lower pressure, approximately atmospheric pressure. If fuel is to be injected into the combustion chambers of the internal combustion engine again, the fuel pump must first build up the delivery pressure at which the fuel exits the fuel filter 1. For this, the expanded air volume must be compressed to the delivery pressure. Because the distance 14 between the vent opening 12 and the cover 3 is very small, only a very small volume of air needs to be compressed, and the delivery pressure in the fuel filter 1 can be used up particularly quickly. This results in a shorter vehicle starting time. The distance 14 can be, for example, only 1 mm. An upper end cap 16 forms an end section of the filter body 7 and seals the filter body 7 tightly against fuel at the top.In the area of ​​the upper end cap 16 and in the area of ​​a corresponding lower end disc 17 of the filter body 7, the replaceable filter body 7 is sealed to the inlet line 4 and to the outlet line 9 by seals 18. A further sealing ring 19 ensures a tight fit of the cover 3 to the lower part 2 of the housing.

[0027] At the in Fig. In the embodiment of the fuel filter 1 shown in Figure 2, the upper end cap 16 forms a conical head 20 towards the center of the fuel filter 1. The inlet opening 12 is also formed by this head 20 of the upper end cap 16. A bore is provided for this purpose in a flat end region of the conical head 20. The head 20, which tapers conically towards the flat end region, can also be shaped like a pyramid.

[0028] At the in Fig.In the embodiment shown in Figure 2, the distance 14 from the inlet opening 12 to the inner wall of the screw head 15 is determined by the shape of the head part 20 of the end cap 16. In this embodiment, the unfiltered fuel flows upwards through an outer space 21 formed between the filter body 7 and the housing wall in the fuel filter 1 into the head chamber 5. A space between the outlet line 9 and an inner wall of the filter body 7 or a corresponding wall on the housing side serves as a vent line 11.

[0029] A bridge 22, which can be arranged on the screw head 15 or on the flat upper surface of the head part 20, ensures that the very small distance 14 between the inlet opening 12 and the inner wall of the screw head 15 is not undercut. Even in this embodiment, the distance 14 can be, for example, only 1 mm. Reference symbol list 1 fuel filter 2 lower part 3 lids 4 Inlet line 5 headroom 6 Flow arrow 7 filter bodies 8 Passage opening 9 Outlet pipe 10 Flow arrow 11 Vent line 12 Entrance opening 13 Flow arrow 14 distance 15 screw head 16 End cap 17 End disc 18 Seal 19 Sealing ring 20 Headboard 21 Outdoor space 22 Bridge

Claims

[1] Fuel filter for a vehicle, with a housing (2, 3) for receiving a fuel-permeable filter body (7), and with a vent line (11) for venting fuel before it escapes from the housing (2, 3), wherein an inlet opening (12) for the vent line (11) is spaced from an end region of the filter body (7) when the filter body (7) is accommodated in the housing (2, 3), wherein the inlet opening (12) is spaced from an inner wall of a cover element (15), and wherein a distance (14) of the inlet opening (12) from the inner wall of the cover element (15) is smaller than a distance of the inlet opening (12) from the end region of the filter body (7) when the filter body (7) is accommodated in the housing (2, 3), characterized by , that when the filter body (7) is accommodated in the housing (2, 3), the inlet opening (12) is formed in a cap (16) coupled to the filter body (7), which cap closes off the filter body (7) at least in regions towards its end region. [2] Fuel filter according to claim 1, characterized by that the distance (14) of the inlet opening (12) from the inner wall of the cover element (15) is less than 10 mm, in particular less than 5 mm. [3] Fuel filter according to claim 1 or 2, characterized by that the distance (14) of the inlet opening (12) from the inner wall of the cover element (15) is 1 mm. [4] Fuel filter according to one of claims 1 to 3, characterized by that the cover element (15) is formed by a cover (3) of the housing (2, 3). [5] Fuel filter according to one of claims 1 to 4, characterized by that the cap (16) tapers conically towards the inlet opening (12). [6] Fuel filter according to one of claims 1 to 5, characterized by that at least one web (22) is formed on a cover (3) of the housing (2, 3), which web is in contact with the cap (16) when the filter body (7) is accommodated in the housing (2, 3). [7] Fuel filter according to one of claims 1 to 6, characterized by that the cover element (15) has a recess aligned with the inlet opening (12).

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