Fuel filter with a fuel filter element comprising a pre-filter and a main filter element

Abstract

Fuel filter (10) comprising: - a filter housing (12), - a fuel filter element (26) interchangeably arranged in the filter housing (12) with a pre-filter element (28), and with a main filter element (30), which are arranged one behind the other in the filter housing (12) in the direction of the longitudinal axis (32) of the filter housing (12), and - a fuel drain channel (106) arranged in the filter housing (12) below the filter element (26), wherein, in the operating position of the filter element (26) in the filter housing (12), a respective raw side of the pre-filter element (28) and the main filter element (30) are sealed against the fuel drain channel (106) by a sealing contact of the filter element (26) with the filter housing (12), and wherein the raw side of the main filter element (30) can be fluidically connected to the fuel drain channel (106) by axially moving the filter element (26) out of its operating position in the filter housing (12) via the raw side of the pre-filter element (28), wherein a flow channel (48) for the fuel pre-filtered by the pre-filter element (28) is arranged between the pre-filter element (28) and the main filter element (30), which is axially connected by mutually associated end disks (38,40) of the pre-filter element (28) and the main filter element (30) is directly limited, wherein the filter housing (12) has a lateral fuel outlet (54) through which the flow channel (48) can be fluidically connected to a fuel pump (56) in order to pump the pre-filtered fuel to the main filter element via a fuel inlet (58) of the filter housing.

Description

Technical field

[0001] The invention relates to a fuel filter with a filter housing and a filter element arranged interchangeably in the filter housing, comprising a pre-filter element and a main filter element, which are arranged one behind the other in the filter housing in the direction of the longitudinal axis of the filter housing. The invention further relates to a fuel filter element. State of the art

[0002] DE 10 2008 048 228 A9 and US 3 900 400 A each disclose a filter with a pre-filter element and a main filter element arranged concentrically to the longitudinal axis of the fuel filter or axially one behind the other. Another fuel filter with two filter elements arranged one above the other and fluidically connected in series is known from EP 0 852 158 A1.

[0003] WO 2006 / 070221 A1 shows another fuel filter with a pre-filter element and a main filter element arranged concentrically to the longitudinal axis of the fuel filter.

[0004] US 2017 / 0 204 821 A1 discloses a fluid filter cartridge, in particular a fuel filter cartridge, comprising a first filter element and a second filter element; wherein the first filter element is an element for separating water from fluid; wherein the second filter element is a tubular filter element with an open filter interior; wherein the first and second filter elements are arranged one behind the other with respect to a longitudinal extent of the fluid filter cartridge, wherein a water collection space is provided for collecting water separated from the fluid by the first filter element, which is arranged at least partially within the open filter interior of the second filter element.

[0005] Similar fuel filters are known from DE 20 2006 004 527 U1 and EP 1 485 605 B1.

[0006] Fuel filter elements, unless designed as lifetime components, must be replaced at specific intervals. Conventional filters have a complex filter housing design, making element replacement cumbersome. When removing the element from the housing, a significant amount of contaminated fuel remains, complicating the process. Furthermore, unfiltered fuel can enter the clean side of the filter housing. This can impair or damage any injection system or internal combustion engine connected to the filter.

[0007] The object of the invention is therefore to provide a fuel filter and a fuel filter element mentioned above, which enable a simple and safe replacement of the fuel filter element and which can be manufactured in a simple and cost-effective manner. Disclosure of the invention

[0008] The problem relating to the fuel filter is solved by a fuel filter according to claim 1. The fuel filter element according to the invention has the features specified in claim 14. Further developments of the invention are described in the description and in the dependent claims.

[0009] The fuel filter according to the invention has a fuel drain channel arranged in the filter housing below the filter element. In the operating position of the filter element in the filter housing, a respective raw side of the pre-filter element and the main filter element are sealed against the fuel drain channel by a sealing contact of the filter element with the filter housing. The raw side of the main filter element can be fluidically connected to the fuel drain channel by axially moving the filter element out of its operating position in the filter housing via the raw side of the pre-filter element. A raw side is understood to be the filter housing volume fluidly upstream of a filter medium of the respective filter element, in which the fuel to be carried through the filter medium is arranged. The fuel filter according to the invention enables simplified and safe replacement of the fuel filter element.By diverting the fuel located on the raw side into the fuel drain channel, the introduction of contaminated fuel onto the clean side of the main filter element—i.e., the flow areas of the fuel filter for the fuel filtered by both filter elements—is prevented. When replacing the fuel filter element, it can drain before the element is completely removed from the filter housing. This also prevents unwanted contamination of the area surrounding the fuel filter. For a particularly simple fuel filter design, the fuel drain channel is preferably fluidically connected to a fuel return line in the filter housing, according to the invention. Such a fuel return line is necessary in modern fuel filters anyway and serves to return the fuel to a fuel tank. This eliminates the need for an additional fuel drain opening in the filter housing.The essential point is that the fuel contained in the fuel drain channel can flow out completely due to gravity alone.

[0010] According to the invention, an axially directed (radial) flow channel for the fuel pre-filtered by the pre-filter element is arranged between the pre-filter element and the main filter element. This flow channel is directly bounded axially by corresponding end plates of the pre-filter element and the main filter element. The filter housing has a lateral fuel outlet through which the flow channel can be fluidically connected to a fuel pump to pump the pre-filtered fuel to the main filter element via a fuel inlet in the filter housing. The flow channel is preferably annular in shape relative to the longitudinal axis of the fuel filter element.

[0011] According to a preferred embodiment of the invention, the fuel filter element in its installation position is located in the filter housing with at least one end disc of the main filter element and at least one sealing element, preferably two sealing elements, of the pre-filter element sealingly against the filter housing.

[0012] For a particularly simple design of the fuel filter and a simplified insertion of the fuel filter element into the filter housing, the filter housing can have a filter pot with an inner diameter that tapers gradually from an insertion opening of the filter housing towards its bottom area.

[0013] The filter housing can thus form sealing surface sections on its inner wall for the sealing contact of the fuel filter element's end discs. These sealing surfaces are spaced closer to the longitudinal axis of the fuel filter element with increasing distance from the filter housing's inlet opening towards the housing base. The sealing elements of the lower end disc of the main filter element and the two end discs of the pre-filter element are, in this case, spaced at correspondingly different distances from the longitudinal axis of the fuel filter element and, when the fuel filter is in operation, make contact with these sealing surface sections within the filter housing. This allows the fuel filter element to be inserted into its operating position in the filter housing without unnecessary stress on its sealing elements due to friction against the housing's inner wall.

[0014] Handling the fuel filter element can be further simplified by connecting the two end discs of the pre-filter element and the main filter element, which define the flow channel, together for joint removal, and in particular by forming them as a single piece. This also offers manufacturing advantages and allows for particularly cost-effective production of the fuel filter. Furthermore, the filter housing can be designed with a further simplified structure, especially without compartments partitioned within the housing.

[0015] In the simplest design, a low-pressure area comprising the pre-filter element and a high-pressure area comprising the main filter element of the fuel filter are separated from each other, at least partially, by a wall element that extends axially from the main filter element, at least partially, through the pre-filter element. According to the invention, the wall element can be integrally formed at one end against an end plate of the main filter element.

[0016] According to the invention, the main filter element of the filter insert can include a water separation unit for separating water contained in the fluid. This allows a combustion engine or fuel injection system powered by the fuel to be reliably protected from potentially harmful water content in the fuel.

[0017] The water separation unit of the main filter element preferably comprises a water separation gap which is fluidically connected at one end to a water drain channel extending axially, at least partially, through the pre-filter element. The water separated from the fuel can be discharged via the water drain channel and thus, for example, fed into a water collection chamber of the filter housing. The water separation gap can, in particular, be arranged between a filter medium of the main filter element and a perforated tube functioning as a final separator.

[0018] The water drainage channel is preferably limited radially on the outside by the aforementioned wall element, which may be formed on the end disk of the main filter element that limits the flow channel.

[0019] According to the invention, the water drain channel preferably has a fluid-tight wall along its entire length to create an additional settling zone in which the water separated from the fuel can settle downwards by gravity. In one embodiment of the invention, the water drain channel can be internally bounded radially by a pipe element that is part of a vent pipe, preferably located centrally inside the fluid filter, or part of a perforated pipe of the water separator unit. Despite the water separation functionality of the fuel filter element, no separate components are required, and the overall size of the fuel filter remains unchanged.

[0020] According to one embodiment of the invention, the vent pipe is (permanently) attached to the filter housing and can, in particular, be snapped or screwed to it. Thus, even when the pre-filter and main filter elements are replaced, the vent pipe remains in the filter housing as a lifetime component. This offers cost advantages and conserves resources.

[0021] The vent pipe can extend axially beyond the upper end plate of the main filter element with its inlet opening, or it can be flush or substantially flush with the upper end plate of the main filter element. This ensures reliable venting of the main filter element.

[0022] The vent pipe preferably opens at its other end into the fuel return line of the filter housing described above, through which the fuel can be returned to a fuel tank. The vent pipe may be equipped with a restrictor to prevent backflow of contaminants into the area of ​​the main filter element.

[0023] According to the invention, the water separation unit can include a coalescing medium to achieve the most efficient possible separation of water contained in the fuel. For maximum separation efficiency, the coalescing medium can be fluidically connected downstream of a filter medium of the main filter element. The coalescing medium can be configured as required, either in a single layer or in multiple layers.

[0024] The wall element described above, preferably together with an end disc of the pre-filter element pointing away from the main filter element (i.e., the lower end disc of the pre-filter element), defines a receiving gap into which a housing or water outlet nozzle of the filter housing extends axially. The lower end disc of the pre-filter element, as well as the wall element, can each be provided with an (elastomeric) sealing element for this purpose.

[0025] As an alternative to forming a receiving gap, the wall element can be tightly connected to the lower end plate. In this case, sealing at a housing or water drain connection can be achieved, for example, via a sealing element arranged radially inside the wall element. Brief description of the drawings

[0026] The drawing shows: Fig. 1 a fuel filter with a filter housing and a filter element arranged therein with a pre-filter element and a main filter element in a perspective sectional view; Fig. 2. Remove the fuel filter Fig. 1 in a longitudinal section; and Fig. 3. Remove the filter insert Fig. 1 in a cutaway view. embodiment(s) of the invention

[0027] In the Fig. 1 and Fig. Figure 2 shows a fuel filter 10 for filtering out impurities contained in fuel, especially diesel fuel. The fuel filter 10 is suitable, for example, for use in commercial vehicles with internal combustion engines.

[0028] The fuel filter 10 comprises an openable filter housing 12 with a filter bowl 14 having an inlet opening 16 and a housing cover 18 for closing the filter bowl 14. The filter cover 18 can be screwed into the filter bowl 14. Alternative methods of attaching the filter cover 18 to the filter bowl 14 are conceivable. The filter housing 12 can be made of, for example, metal or plastic. A filter head 20 is formed at the lower end of the filter housing 12. The fuel filter 10 is thus designed for a vertical installation in operation, in a manner known per se.

[0029] The filter housing 12 has a fuel inlet 22, which serves to supply the fuel to be filtered, for example from a fuel tank (not shown), to the fuel filter 10. A fuel return line 24 of the filter housing serves to return contaminated fuel, e.g. to the aforementioned fuel tank.

[0030] Inside the filter housing 12, a fuel filter element 26 is arranged. The fuel filter element 26 comprises a pre-filter element 28 and a main filter element 30. The two filter elements 28 and 30 are arranged one above the other in the filter housing 12, aligned along the longitudinal axis 32 of the fuel filter. The longitudinal axis 32 of the fuel filter coincides with the longitudinal axis 34 of the fuel filter element 26. The main filter element 30 is fluidically connected downstream of the pre-filter element 28. In other words, during operation, the fuel to be filtered first flows through the pre-filter element 28, which is located at the bottom of the filter housing, and subsequently through the main filter element 30, which is located above the pre-filter element 28.

[0031] The pre-filter element 28 and the main filter element 30 are each designed as circular filter elements with a filter medium 36 arranged in a ring around the longitudinal axis 34 of the filter element. The fuel to be filtered flows through the filter medium 36 of both the pre-filter element 28 and the main filter element 30 in a radial direction from the outside to the inside, around the longitudinal axis 34 of the fuel filter element 26. The filter media 36 are each designed as a star-shaped pleated filter bellows and are held between a lower and an upper end disk 38, 40 of the respective filter element. The upper end disk 40 of the main filter element 30 is detachably coupled to the housing cover 18 via a bayonet connection 41 (snap connection or similar). A grid-shaped support tube 42 serves to radially support the filter media 36 of the pre-filter element 28 as well as the main filter element 30 on the inside.The filter media 36 are located on the inside of the respective support tube, preferably directly against it.

[0032] The corresponding end discs 38, 40 of the pre-filter element and the main filter element, i.e., the lower end disc 38 of the main filter element 30 and the upper end disc 40 of the pre-filter element, are arranged axially spaced apart from each other. These two end discs 38, 40 each bear against the inside of the filter housing via sealing elements 43, creating a fluid-tight seal. The two end discs 38, 40 thus serve as sealing discs, dividing the inside of the filter housing axially into a pre-filter chamber 44 containing the pre-filter element 28 and a main filter chamber 46 containing the main filter element. A flow channel 48 for the fuel pre-filtered by the pre-filter element 28 is arranged between the upper end disc 40 of the pre-filter element 28 and the lower end disc 38 of the main filter element 30.The flow channel 48 is directly limited in the axial direction by the mutually associated end disks 38, 40 of the pre- and main filter element.

[0033] The upper end disc 40 of the pre-filter element 28 and the lower end disc 38 of the main filter element 30 are connected to each other for the joint assembly of the main and pre-filter elements 30, 28, in particular formed in one piece and may in particular be designed as a plastic injection-molded part. As can be seen from the Fig. 1 and Fig. As can be seen from Figure 2, spacer elements 50 are arranged between the two end discs, which are attached to the two end discs, in particular molded on.

[0034] The flow channel 48 is essentially annular and is fluidically connected in a radial direction to the inner wall 52 of the filter housing 12. The flow channel 48 is fluidically connected at its outlet to a lateral (radially) arranged fuel outlet 54 of the filter housing 12. A fuel pump 56 can be connected to the fuel outlet 54. The fuel pump 56 serves to draw the contaminated fuel into the pre-filter chamber 44 and through the pre-filter element 28, and to pump the pre-filtered fuel, which is discharged from the filter housing 12, back into the main filter chamber 46 of the filter housing 12 via a fuel inlet 58 of the filter housing 12. This is done to guide the pre-filtered fuel through the filter medium 36 of the main filter element 30. The fuel inlet 58 is axially offset relative to the fuel outlet 54 of the filter housing 12.

[0035] The main filter element 30 has a water separation unit 60 for separating water contained in the fuel. The water separation unit 60 comprises a coalescing medium 62, which is arranged in a ring around the longitudinal axis 34 of the fuel filter element 26. The coalescing medium 62 can be, as shown in the Fig. 1 and Fig. As shown in Figure 2, the coalescing medium 62 is arranged downstream of the filter medium 36 of the main filter element 30, particularly in a fluidic manner. The coalescing medium 62 advantageously rests against the inside of a central tube 64 to prevent it from collapsing when pressurized during operation of the fuel filter 10. The central tube 64 is located within the support tube 42 and coaxially with the longitudinal axis 34 of the fuel filter element 26. The coalescing medium 62 is thus positioned between the central tube 64 and the support tube 42 of the filter medium 36 of the main filter element 30. The coalescing medium 62 can be constructed as required in one or more layers and, for example, consist of a nonwoven fabric.

[0036] As from the Fig. 1 and Fig. As shown in Figure 2, a perforated tube 66 is arranged within the central tube. The perforated tube 66 serves functionally as a final separator for the water contained in the fuel. The perforated tube 66 is arranged coaxially with the longitudinal axis 34 of the fuel filter element 26. The interior of the perforated tube 66 is fluidically connected to a fuel channel 70 of the filter housing 12 via a fuel drain channel 68, which extends partially through the pre-filter element 28 in the axial direction. During operation, the fuel, filtered by the pre- and main filter elements 28, 30 and at least partially freed of water, flows from the interior of the perforated tube 66 downwards from the fuel filter element 26 via the fuel drain channel 68 and the fuel channel 70 of the filter housing 12.

[0037] An annular water separation gap 72 is formed between the sieve tube 66 and the coalescing medium 62 or the central tube 64. The water separation gap 72 is open at the bottom and is fluidically connected at one end to a longitudinally extended water drainage channel 74.

[0038] A substantially tubular wall element 76 is attached, in particular integrally formed, to the lower end disk 38 of the main filter element 30. This wall element 76 extends axially from the lower end disk 38 of the main filter element 30 towards the filter head, i.e., downwards. The wall element 76 extends axially into the pre-filter element 28 up to the level of the lower end disk 38 of the pre-filter element 28. The wall element 76 defines the inner radial boundary of the pre-filter chamber 44 and separates it from the water drain channel 74 of the fuel filter element 26. In other words, the outer radial boundary of the water drain channel 74 for the water separated from the fuel is directly defined by the tubular wall element 76.

[0039] The wall element 76 thus separates a low-pressure area 78 comprising the pre-filter element 28 and a high-pressure area 80 of the fuel filter insert 26 comprising the main filter element 30 from each other.

[0040] The water drainage channel 74 can extend completely or partially through the pre-filter element 28 in an axial direction and is fluidically connected to a water drainage channel or water collection chamber 84 of the filter housing 12 via a housing or water drainage nozzle 82 of the filter housing 12.

[0041] The tubular wall element 76 and the lower end plate 38 of the pre-filter element 28 together define a receiving gap 86 into which the housing or water drain nozzle 82 projects in a sealed axial direction. The wall element 76 rests against the water drain nozzle 82 on the inside via a sealing element 43, and the lower end plate 38 of the pre-filter element 28 rests against the water drain nozzle 82 on the outside via another sealing element 43. This seals the low-pressure area or pre-filter chamber 44 against the high-pressure area or water drain channel 74.

[0042] The water drain channel 74 is bounded radially on the inside by a pipe element 88. The pipe element 88 also forms a radially outer boundary of the fuel drain channel 68. At one end, the pipe element 88 is integrally connected to a centrally arranged vent pipe 92 of the fuel filter 10 via a fenestrated connecting section 90 (not shown) that is arranged obliquely to the longitudinal axis 34 of the fuel filter element 26. Alternatively, the pipe element can also be formed as part of the perforated tube 66 of the fuel filter element 26.

[0043] A free end section of the perforated tube 66 is designed as a sealing lip or a sealing collar 94 and rests fully and tightly against the outer surface of the tube element 88. The other end of the tube element 88 of the vent pipe 92 is latched (or screwed) to a fuel drain fitting 96 of the filter housing 12, i.e., at its lower end, and rests against this fitting on the inside via a sealing element 43.

[0044] The vent pipe 92 serves to vent the main filter element 30 or the main filter chamber 46 and extends coaxially through the longitudinal axis 34 of the fuel filter element. The vent pipe 92 can protrude axially at one end beyond the upper end disc 40 of the main filter element 30 with its inlet opening 98.

[0045] The inlet opening 98 of the vent pipe 92 is located in this case between the upper end disc 40 of the main filter element 30 and the housing cover 18. It is understood that the vent pipe 92 can also be arranged flush or substantially flush with the upper end disc 40 of the main filter element. The vent pipe 92 projects at its other end into a sealing vent port 100 of the filter housing 12. The vent port 100 can be fluidically connected to the fuel return line 24 of the filter housing 12. During operation of the fuel filter 10, air contained in the fuel or fuel vapors in the area of ​​the main filter chamber 46 can thus be evacuated from the filter housing 12 via the vent pipe 92 and the fuel return line 24 of the filter housing 12. For safety reasons, the vent pipe 92 may be fitted with a throttle 102, for example in the area of ​​its inlet opening 98.

[0046] The pre-filter chamber 44 is bounded at the bottom by a housing base 104 of the filter housing 12. In its illustrated installation state, the pre-filter element 28 is axially spaced from the housing base 104. This creates a fuel drain channel 106 between the lower end disk 38 of the pre-filter element 28 and the housing base 104. The fuel drain channel 106 surrounds the longitudinal axis 32 of the fuel filter housing 12 and is open to the fuel return line 24 of the filter housing 12, i.e., fluidically connected to it.

[0047] The filter housing 14 has an internal cross-section that tapers axially towards the housing base 104, i.e., in the insertion direction 108 of the fuel filter element. The filter housing 12 thus has sealing surface sections 110 in the area of ​​its inner wall 52 for the sealing contact of the end discs 38, 40 of the fuel filter element, which are spaced closer together with increasing distance from the insertion opening 16 of the filter housing 12 towards the housing base 104 and closer to the longitudinal axis 34 of the fuel filter element 26. The sealing elements 43 of the lower end disc 38 of the main filter element 30 and of the two end discs 38, 40 of the pre-filter element 28 are spaced at different distances corresponding to the longitudinal axis 34 of the fuel filter insert 26 and, in the operating position of the fuel filter insert 26 shown, are in sealing contact with the sealing surface sections 110 of the filter pot 14 in the filter housing 12.This allows the fuel filter element 26 to be simplified and inserted into its operating position in the filter housing without unnecessary stress on its sealing elements 43.

[0048] To replace the fuel filter element 26, it is moved axially out of the filter housing 14 against the insertion direction 108. As soon as the fuel filter element is removed via a thread 112 ( Fig. 2) When the axial path is moved from its shown installation position to a drainage position, the sealing elements 43 of the lower and upper end discs 38, 40 of the pre-filter element 28 and the lower end disc 38 of the main filter element 30 are removed from their respective sealing positions on the filter housing 12 and the water drain nozzle 82, respectively. Consequently, the main filter chamber 46 is fluidically connected to the fuel drain channel 106 via the pre-filter chamber 44. This allows the raw fuel from the main filter chamber 46 to flow through the pre-filter chamber 44, together with the raw fuel located there, into the fuel drain channel 106 under the influence of gravity. The fuel can then flow to the fuel return line 24 via the fuel drain channel 106.

[0049] It should be noted that the axial length of the housing-side water drain spout 82 is dimensioned such that the sealing element 43 of the wall element 76 remains in sealing contact with the water drain spout 82 in the drainage position of the fuel filter element 26. This ensures that fuel from the pre-filter chamber 44 does not reach the clean side of the fuel filter 10, specifically the water drain (spout) or the fuel drain spout 96 of the fuel channel 70.

[0050] Fig. 3 shows the fuel filter element from the Fig. 1 and Fig. 2 in a cutaway view and in a longitudinal section. The grid structure of the perforated tube 66 is clearly visible in this view. The perforated tube 66 is connected to the upper end disk 40 of the main filter element 30, e.g., by a snap-fit ​​connection. The sealing collar 94 of the perforated tube can be made of an elastically deformable (plastic) material. The sealing collar 94 can thus be inserted axially into the filter housing ( Fig. 1 and Fig. 2) The main filter element 30 is slid onto the pipe element 88, guided by the inclined connecting section 90 of the vent pipe 92, in a sealing manner. The lower end disc 38 of the main filter element 30 has a retaining rib 114 on its inner circumference. The retaining rib 114 extends axially from the lower end disc 38 towards the upper end disc 40 of the main filter element 30 and supports the central tube 64 on its inner side.

[0051] During operation of the fuel filter 10, the unfiltered fuel drawn in by the fuel pump flows through the fuel inlet 22 of the filter housing into the pre-filter chamber 44 and flows radially from the outside to the inside through the filter medium 36 of the pre-filter element 28. The fuel passes through the tubular wall element 76 of the main filter element, via the flow channel 48 and the lateral fuel outlet 54 of the filter housing, into the fuel pump 56. The pre-filtered fuel is pumped into the main filter chamber 46 of the filter housing 12 by means of the fuel pump, which is fluidically connected between the fuel outlet 54 and the fuel inlet 58. The pre-filtered fuel flows through the filter medium 36 of the main filter element 30, the coalescing medium 62, and the perforated tube in a radial direction from the outside to the inside, relative to the longitudinal axis 34 of the fuel filter element 26.In this process, the water contained in the fuel is at least partially separated from the fuel and flows downwards by gravity from the water separation gap 72 via the water drainage channel 74 into the water collection chamber 84 of the filter housing 12. The fuel, thus freed from impurities, flows out of the fuel filter 10 via the fuel channel 70 and can be supplied to an internal combustion engine or a fuel injection pump.

[0052] To replace the fuel filter element 26, the housing cover 18 is first removed from the filter housing 14. The bayonet connection 41 between the housing cover 18 and the fuel filter element 26 is closed or is closed by the screwing movement of the housing cover 18. The fuel filter element 26 is moved axially as a whole in the direction of the longitudinal axis 32 of the filter housing 12 from its installation position by the screwing movement ( Fig. 1 and Fig. 2) is moved. As soon as the filter element is in the drainage position, the raw (pre-filtered) fuel flows from the main filter chamber 46 of the filter housing 12 into the pre-filter chamber 44 and, together with the raw fuel located there, via the fuel drain channel 106 into the fuel return line 24 and, if applicable, into a fuel tank fluidically connected to it. When the housing cover 18 is further unscrewed or lifted from the filter pot 14 together with the fuel filter element 26, the inner sealing element 43 of the wall element 76 and the sealing element 43 of the lower end disc 38 of the pre-filter element 28, which rests against the water drain port 82, are also moved from their sealing position on the water drain port 82. Any liquid level of a fuel-water mixture that may be present on the clean side can then flow radially outwards into the fuel drain channel 106 and flow out of the filter housing 12 via the fuel return line 24.After the fuel filter element 26 has been completely removed from the filter housing, it is detached from the housing cover 18 and a new fuel filter element 26 is attached to the housing cover 18. The fuel filter element 26 is then inserted into the filter housing 14 in the insertion direction and moved into its installation position by screwing the housing cover 18 onto the filter housing 14. Fig. 1 and Fig. 2).

Claims

[1] Fuel filter (10) comprising: - a filter housing (12), - a fuel filter element (26) interchangeably arranged in the filter housing (12) with a pre-filter element (28), and with a main filter element (30), which are arranged one behind the other in the filter housing (12) in the direction of the longitudinal axis (32) of the filter housing (12), and - a fuel drain channel (106) arranged in the filter housing (12) below the filter element (26), wherein, in the operating position of the filter element (26) in the filter housing (12), a respective raw side of the pre-filter element (28) and the main filter element (30) are sealed against the fuel drain channel (106) by a sealing contact of the filter element (26) with the filter housing (12), and wherein the raw side of the main filter element (30) can be fluidically connected to the fuel drain channel (106) by axially moving the filter element (26) out of its operating position in the filter housing (12) via the raw side of the pre-filter element (28), wherein a flow channel (48) for the fuel pre-filtered by the pre-filter element (28) is arranged between the pre-filter element (28) and the main filter element (30), which is axially connected by mutually associated end disks (38,40) of the pre-filter element (28) and the main filter element (30) is directly limited, wherein the filter housing (12) has a lateral fuel outlet (54) through which the flow channel (48) can be fluidically connected to a fuel pump (56) in order to pump the pre-filtered fuel to the main filter element via a fuel inlet (58) of the filter housing. [2] Fuel filter according to claim 1, characterized by , that the fuel drain channel (106) is fluidically connected to a fuel return line (24) of the filter housing (12) to return the fuel from the filter housing (12) to a fuel tank. [3] Fuel filter according to claim 1 or 2, characterized by , that the fuel filter element (26) in its operating position in the filter housing (12) is in a sealing position on the inside of the filter housing (12) with at least one end disc (38, 40) of the main filter element (30) and of the pre-filter element (28). [4] Fuel filter according to any one of the preceding claims, characterized by , that the filter housing (12) has a filter pot (14) with an inner diameter that tapers stepwise from an insertion opening (16) of the filter housing (12) towards its housing bottom (104). [5] Fuel filter according to any one of the preceding claims, characterized by , that the two end discs (38, 40) of the pre-filter element (28) and the main filter element (30), which directly define the flow channel (48), are connected to each other for the joint construction of the main and pre-filter element (30, 28), are formed in one piece together. [6] Fuel filter according to any one of the preceding claims, characterized by, that a low-pressure area (78) comprising the pre-filter element (28) and a high-pressure area (80) comprising the main filter element (30) of the fuel filter insert (26) are separated from each other at least section by a wall element (76) which extends from the main filter element (30) in an axial direction at least partially through the pre-filter element (28). [7] Fuel filter according to claim 6, characterized by , that the wall element (76) is attached at one end to an end disk (38, 40) of the main filter element (30), in particular by molding. [8] Fuel filter according to any one of the preceding claims, characterized by a water separator unit (60) for separating water contained in the fuel. [9] Fuel filter according to claim 8, characterized by, that the water separation unit (60) comprises a water separation gap (72) which is fluidically connected via a water drainage channel (74) to a water collection chamber (84) of the filter housing (12), wherein the water drainage channel (74) extends in axial direction at least sectionally through the pre-filter element (28). [10] Fuel filters according to claims 6 and 9, characterized by , that the water drainage channel (74) is radially limited on the outside by the wall element (76). [11] Fuel filter according to claim 10, characterized by , that the wall element (76) together with a lower end disk (38) of the pre-filter element (28) pointing away from the main filter element (30) defines a receiving gap (86) into which a water drain nozzle (82) of the filter housing (12) extends in a sealing manner. [12] Fuel filter according to any one of claims 8 to 11, characterized by, that the water drainage channel (74) is radially limited on the inside by a pipe element (88) which is part of a vent pipe (92) of the fuel filter (10) or part of a sieve tube (66) of the water separator unit (60). [13] Fuel filter according to claim 12, characterized by , that the vent pipe (92) is attached to the filter housing (12), in particular snapped or screwed to it, wherein the vent pipe (92) preferably opens at one end into a fuel return line (24) for returning the fuel to a fuel tank. [14] Fuel filter element (26) for a fuel filter (10) according to one of the preceding claims, comprising a pre-filter element (28) and a main filter element (30) arranged one behind the other in the direction of the longitudinal axis (34) of the fuel filter element (26), wherein a flow channel (48) for the fuel pre-filtered by the pre-filter element (28) is arranged between the pre-filter element (28) and the main filter element (30), which is directly limited in the axial direction by mutually associated end disks (38, 40) of the pre-filter element (28) and the main filter element (30).

Images