CN110234414B

CN110234414B - Fluid filter having a filter insert with a pre-filter element and a main filter element

Info

Publication number: CN110234414B
Application number: CN201880010774.9A
Authority: CN
Inventors: C.鲍曼; J.埃布勒; L.施佩尔特
Original assignee: Mann and Hummel GmbH
Current assignee: Mann and Hummel GmbH
Priority date: 2017-02-07
Filing date: 2018-02-06
Publication date: 2021-11-09
Anticipated expiration: 2038-02-06
Also published as: CN110234414A; DE112018000711A5; WO2018146102A1; DE102017001100A1

Abstract

The invention relates to a fluid filter (10), in particular for fuel or oil, comprising a filter housing (12) and a filter insert (20) which is arranged in the filter housing (12) in a replaceable manner and which has a prefilter element (22) and a main filter element (24) which are arranged one above the other in the filter housing (12) in the direction of a longitudinal axis (26) of the filter housing (12). The filter housing (12) has a prefilter discharge (98) for the prefilter element (22) and a main filter discharge (100) for the main filter element (24) which is configured separately from the prefilter discharge (98). The two discharge openings are closed in a fluid-tight manner in an operating position of the filter insert (20) in the filter housing (12). The filter insert (20) can be transferred from its operating position into a drainage position by an axially directed removal movement of the filter insert (20), in which the unfiltered side (60) of the prefilter element (22) is connected in a fluid-tight manner to a prefilter drain (98) and the unfiltered side (66) of the main filter element (24) is connected in a fluid-tight manner to a main filter drain (100). The fluid filter (10) according to the invention enables a simplified and rapid replacement of the filter insert (20).

Description

Fluid filter having a filter insert with a pre-filter element and a main filter element

Technical Field

The invention relates to a fluid filter, in particular for fuel or oil, having a filter housing and a filter insert arranged in the filter housing in a replaceable manner, the filter insert having a prefilter element and having a main filter element which are arranged one above the other in the filter housing in the direction of a longitudinal axis of the filter housing. The invention further relates to a filter insert.

Background

From EP 2649292B 1 a fuel filter is known with three annular filter elements, which are arranged coaxially with respect to one another, and wherein at least two of the annular filter elements are arranged offset with respect to one another in the axial direction. The annular filter elements are connected in series and can be traversed in sequence by the fluid to be filtered.

WO 2007/128306 a2 discloses a liquid filter for an internal combustion engine, having a filter housing with a filter insert arranged exchangeably therein. In the maintenance position, the clean oil line is raised relative to the filter housing, so that oil present in the filter housing can flow into the outflow channel of the filter housing.

Furthermore, a fuel filter is known from DE 102015003165 a1, having a filter housing and a filter element arranged exchangeably in the filter housing, wherein a main filter element and a prefilter element are arranged one above the other in the longitudinal direction. The filter housing has a pre-filter discharge and a main filter discharge. When the filter element is pulled out in the longitudinal direction, the filter system is transferred into a drain position, wherein the unfiltered side of the prefilter element is connected in a fluid-tight manner to the prefilter drain and the unfiltered side of the main filter element is connected in a fluid-tight manner to the main filter drain. However, separate outflow of the main filter outlet and the prefilter outlet cannot be achieved, since they merge together in the drainage position and the filter system as a whole is emptied via the prefilter outlet.

If the filter inserts of the fluid filter are not implemented as life-long components, they must be replaced at defined intervals. Known filters, such as fuel filters or fuel filters, in particular for internal combustion engines, have a complex construction of their filter housing and only permit a cumbersome replacement of the filter insert. In multistage filters, that is to say filters having a plurality of filter elements connected one behind the other, in practice it is often necessary to last for a long time until the fluid in the filter housing has been discharged. Furthermore, it may occur that contaminated, i.e. unfiltered, fluid reaches the clean side of the filter housing. This can lead to downstream units, for example injection systems or internal combustion engines, being affected or damaged.

Disclosure of Invention

The object of the present invention is therefore to provide a fluid filter and a filter insert of the type mentioned at the outset, which enable a simplified and rapid replacement of the filter insert.

The invention is described in the specification as a modification.

The fluid filter according to the invention can be designed in particular as a fuel filter or as an oil filter, in particular for an internal combustion engine of a motor vehicle. The fluid filter includes a filter housing. A filter insert is exchangeably arranged in the filter housing. The filter insert has a pre-filter element and a main filter element. The pre-filter element and the main filter element may be traversed sequentially, i.e. in sequence, by the fluid to be filtered. By means of the multistage filtration of the fluid, particularly good degrees of separation can be achieved and/or a large volume flow of the fluid to be filtered through the filter can be established. The pre-filter element and the main filter element are arranged one above the other in the direction of the longitudinal axis of the filter housing. The main filter element can be arranged here above or below the prefilter element. This allows a particularly compact construction of the fluid filter. In particular, the space requirement for installing the fluid filter in the radial direction with respect to the longitudinal axis of the filter housing can be reduced. When the filter insert is arranged in the filter housing, the longitudinal axis of the filter housing can fall together with the longitudinal axis of the filter insert. The longitudinal axis of the filter housing is typically oriented vertically or approximately vertically during operation of the fluid filter. The deviation of the longitudinal axis of the filter housing from the vertical is preferably at most 30 °, particularly preferably at most 20 °, very particularly preferably at most 10 °. The pre-filter element can be arranged here above or below the main filter element. In other words, the fluid filter may be traversed by fluid from top to bottom or vice versa. The filter insert with the pre-filter element and the main filter element forms a (structural) unit that can be handled in one piece. It only requires replacement of the filter insert and not replacement of the unit comprising the pre-filter element and the main filter element. The filter housing according to the invention has a prefilter outlet for the prefilter element and a main filter outlet for the main filter element, which is designed separately from the prefilter outlet. One respective (fluid) outlet opening is thus provided for each of the two filter elements of the filter insert. This makes it possible to accelerate the emptying of the filter element before the filter insert is replaced with a new filter insert. In the operating position of the filter insert in the filter housing, the prefilter outlet and the main filter outlet are closed against fluid flow. Thus, when the filter insert is in the operating position in the filter housing, no fluid can flow out of the drain opening. The two outlet openings are closed against fluid flow by a filter insert arranged in the filter housing in the operating position. In this way, it is ensured in a simple and reliable manner that the outlet opening is closed fluid-tightly during filter operation of the fluid filter.

The filter insert can be transferred from its operating position into the drain position by an axially directed removal movement of the filter insert. This can be done, for example, by unscrewing a housing cover of a filter tank which closes the filter housing. The filter insert is held in this case in a tensile manner on the housing cover, for example by being connected to the housing cover by means of a snap-in groove, snap or bayonet connection. In the drainage position of the filter insert, the unfiltered side of the prefilter element is connected in a fluid-tight manner to the prefilter drain and the unfiltered side of the main filter element is connected in a fluid-tight manner to the main filter drain. The unfiltered side is understood in each case as the volume of the filter housing which is connected in a fluid-tight manner upstream of the filter medium of the respective filter element. In other words, unfiltered fluid flows to the prefilter element on the unfiltered side of the prefilter element. Instead, fluid pre-filtered by the pre-filter element on the unfiltered side of the main filter element flows to the main filter element. In the drainage position of the filter insert, therefore, a fluid flow out of the region of the unfiltered side of the prefilter element or the main filter element into the corresponding prefilter drain or main filter drain can be achieved. When the filter insert is replaced, the filter insert can be emptied into the filter housing before the filter insert is completely removed from the filter housing. The residual quantity remaining in the filter insert can thereby be reduced and undesired soiling of the surroundings of the fluid filter is suppressed.

The fluid disposed in the filter housing can be smoothly discharged from the filter housing via two separately formed discharge openings. It is thus not necessary to remove the filter insert from the fluid in the filter housing or to insert a replacement filter insert into the fluid. It goes without saying that the pre-filter discharge is preferably arranged below the pre-filter element and the main filter discharge is preferably arranged below the main filter element. This enables the fluid to drain autonomously from the filter housing under the influence of gravity. Overall, in the fluid filter according to the invention, the replacement of the filter insert with the pre-filter element and the main filter element is simplified and accelerated.

For a structurally simple design of the fluid filter, it can be provided according to the invention that the filter insert in its operating position in the filter housing bears sealingly against the filter housing in order to prevent fluid-tight closure of the pre-filter discharge opening and the main filter discharge opening. The sealing of the discharge opening is thus brought about in this case by the filter insert itself. For the sealing contact, the filter insert can preferably have one or more sealing elements. According to the invention, the filter insert can rest in its operating position on the filter housing in a sealed manner on the inside with at least one end disk of the prefilter element and of the main filter element. The construction of the filter insert can thereby be further simplified. In particular, the seat or receptacle for the sealing element or elements can be integrated directly into the end disk provided with the sealing element.

The prefilter drain and the main filter drain are sealed relative to one another in accordance with the invention in the drainage position of the filter insert. This can be brought about by the sealing abutment of the filter insert on the filter housing. Thereby, it is possible to avoid that unfiltered fluid from the unfiltered side of the pre-filter element passes over to the unfiltered side of the main filter element. Thereby a higher level of contamination damage to the main filter element can be avoided. In other words, it is ensured that unfiltered fluid in the drainage position of the filter insert can be pushed into the region which in operation is in contact only with the prefiltered fluid.

The filter housing can according to the invention have a housing base with an end-side axial outlet for the fluid. Fluid filtered by the filter element located below along the longitudinal axis of the filter housing can be discharged from the housing through the axial outlet. The axial outlet is sealed with respect to the pre-filter drain and the main filter drain in the drain position of the filter insert. This can additionally prevent contamination from reaching the axial outlet on the clean side in the drainage position of the filter insert. The axial outlet is preferably arranged centrally on the housing base, in particular coaxially to the longitudinal axis of the filter housing.

According to a preferred development of the invention, the axial outlet at the end is surrounded by an annular connection piece of the filter housing arranged in the filter housing. The filter insert rests sealingly against the annular connection piece of the filter housing in the operating position and also in the drainage position, preferably with the end disk of the prefilter element or of the main filter element. It is thereby ensured that, both in the operating position and in the drainage position, no fluid can reach the axial outlet on the clean side from the unfiltered side of the filter element lying below. The annular connection piece can preferably be arranged coaxially to the longitudinal axis of the filter housing and/or to the axial outlet. The annular connection piece extends from the housing base into the interior of the filter housing, preferably parallel to the longitudinal axis of the filter housing. The annular connection piece thus shields the axial outlet in the radial direction with respect to the longitudinal axis of the filter housing.

Advantageously, the axial outlet on the end side can be connected in the operating position of the filter insert in a fluid-tight manner, in particular directly, to the clean side of the pre-filter element or the main filter element. This simplifies the discharge of the fluid filtered by the prefilter element or the main filter element from the filter housing. The clean side is understood to mean a filter housing volume which is fluidically connected downstream of the filter medium of the respective filter element and which can be filled with fluid which has been conducted through the filter medium during operation of the fluid filter.

For a particularly simple design of the fluid filter and a simplified insertion of the filter insert into the filter housing, the filter housing can have a filter pot with an inner diameter which tapers in steps from the inlet opening of the filter housing towards the housing bottom thereof. The filter housing can thus be designed in the region of its inner wall with sealing surface sections for sealing against the filter insert, in particular the end discs, which become less distant from the longitudinal axis of the filter insert toward the housing base with increasing distance from the inlet opening of the filter housing. In this case, the sealing elements of the filter insert are at a distance from the longitudinal axis of the fuel filter insert that is different in a corresponding manner to this and in the operating state of the fluid filter in the filter housing rest sealingly against the sealing surface section. The filter insert can thus be inserted into its operating position in the filter housing without unnecessary overstressing of its sealing element by friction on the housing inner wall. At the same time, it can be ascertained by the length of the corresponding axial extension of the sealing surface section when the sealing element is disengaged from the sealing surface section when the filter insert is pulled out of the filter tank.

Between the prefilter element and the main filter element, according to the invention, a flow channel for the fluid can be arranged, which is delimited directly in the direction of the longitudinal axis of the filter housing or filter insert by the end discs of the prefilter element and of the main filter element which correspond to one another. The flow channel thus extends directly between the two mutually corresponding end discs of the two filter elements. In other words, the end discs bounding the flow channel are arranged on the mutually directed end faces of the pre-filter element and the main filter element. The filter housing preferably has a (laterally arranged) side outlet in this case, into which the flow channel opens. The flow passage may be fluidly connected downstream of the pre-filter element or the main filter element. Typically, the flow channel is fluidly connected to the clean side of the filter element of the filter insert arranged above in the direction of the longitudinal axis of the filter insert. The flow channel may be configured as a radial flow channel. If the clean side of the pre-filter element is fluidly connected with the flow channel, fluid can be pumped from the side outlet to the inlet for the main filter element in the filter housing by means of a pump coupled to the side outlet. The flow channel is preferably configured annularly with respect to the longitudinal axis of the filter insert.

Handling of the filter insert can thereby be simplified even further, so that the two end discs of the pre-filter element and the main filter element which directly delimit the flow channel are constructed integrally with one another. This furthermore provides advantages in terms of production technology and allows particularly advantageous production of the fluid filter or filter insert. Furthermore, the filter housing can be implemented with a further simplified construction, in particular without the need for a housing-side divided chamber.

The fluid filter may according to the invention have a water separation unit for separating water contained in the fluid. Components connected downstream of the fluid filter can thereby be reliably protected against potentially harmful water contents in the fluid. The water separation unit preferably has a coalescing medium in view of separating the fluid, in particular the water contained in the fuel, as efficiently as possible. The coalescing media may be fluidly connected downstream of the filter media of the main filter element for the purpose of as large a separation efficiency as possible. The coalescing media herein may be implemented in a single layer or in multiple layers as desired. The water separation unit is preferably arranged in the filter element below in the operating position.

In an advantageous development, it is provided that the water separation unit is arranged radially within the prefilter element or the main filter element and that the filter element with the water separation unit can be traversed in sequence by the fluid. This allows a particularly compact construction of the fluid filter. Preferably, the filter element in which the water separation unit is arranged is traversed in the filter operation from the outside to the inside in the radial direction by the fluid to be filtered.

In a particularly preferred embodiment, the fluid filter with an axial outlet on the housing bottom, which is surrounded by a built-in annular connection piece, and a water separation unit arranged radially within the filter element can be characterized in that the filter housing has a water outlet on the housing bottom for the water separated from the fluid, which water outlet is surrounded by the annular connection piece in the radial direction. In this way, the water separation unit is preferably arranged radially within the filter element below in the direction of the longitudinal axis of the filter housing. The water outlet is formed on the housing bottom at a distance from the axial outlet. The annular connection piece surrounds both the axial outlet and the water outlet. The water outlet may be separated from the axial outlet by an annular barrier to prevent separated water from reaching the axial outlet. The annular barrier can be formed on the housing base, in particular concentrically and radially within the annular socket. The water separating device can bear sealingly against the annular barrier in the operating position of the filter insert. In this way, the water separated off at the water separation device during the outward-inward flow passes directly into the water collecting channel formed between the annular barrier and the annular connection piece.

For a particularly compact construction of the fluid filter, the prefilter element and the main filter element can each be designed according to the invention as a round filter element, in particular as a filter medium having star-shaped folds. Preferably, the pre-filter element and the main filter element are arranged coaxially with respect to the longitudinal axis of the filter housing. This simplifies the insertion of the filter insert into the filter housing.

A filter insert for a fluid filter according to the invention, which filter insert has a prefilter element and has a main filter element, which are arranged one behind the other in the direction of the longitudinal axis of the filter insert, also falls within the framework of the invention. Such a filter insert can be replaced quickly and simply.

Other advantages of the invention are illustrated from the description and drawings. The features described above and yet to be elucidated can be used in accordance with the invention on their own or in various combinations of any kind.

Drawings

Shown in the drawings are:

fig. 1 shows, in a schematic longitudinal section, a fluid filter having a filter housing and a filter insert arranged therein in an operating position, the filter insert having a pre-filter element and a main filter element; and

fig. 2 shows the fluid filter of fig. 1 with the filter insert in a drainage position.

Detailed Description

Fig. 1 shows a fluid filter 10 according to the present invention. The fluid filter 10 can be designed, for example, as a fuel filter for filtering out contaminants contained in fuel, in particular diesel fuel. The fluid filter 10 is suitable for use in a motor vehicle having an internal combustion engine, for example.

The fluid filter 10 comprises an openable filter housing 12 with a filter tank 14 with an inlet opening 16 and with a filter cover 18 for closing the filter tank 14. The filter cover 18 may be screwed into the filter tank 14. Another way of fastening the filter cover 18 on the filter tank 14 is conceivable. The filter housing 12 can be made, for example, of metal or of a plastic material.

A filter insert 20 is exchangeably arranged in the interior of the filter housing 12. In fig. 1, the filter insert 20 is in an operating position in the filter housing 12, so that the fluid filter 10 can be used in a separating operation. The filter insert 20 includes a pre-filter element 22 and a main filter element 24. The two

filter elements

22, 24 are arranged one above the other in the direction of the longitudinal axis 26 of the filter housing in the filter housing 12. When the filter insert 20 is installed in the filter housing 12 in the operating position, the longitudinal axis 26 of the filter housing and the longitudinal axis 28 of the filter insert fall together. A main filter element 24 is fluidly disposed downstream of the pre-filter element 22. In other words, in the filter operation, in the present case the fluid to be filtered first flows through the pre-filter element 22 arranged above in the filter housing 12 and then through the main filter element 24 arranged below the pre-filter element 22.

The pre-filter element 22 and the main filter element 24 are each embodied as a circular filter element with filter media 30a, 30b arranged annularly about the longitudinal axis 28 of the filter insert. The filter media 30a of the pre-filter element 22 and the filter media 30b of the main filter element 24 may be traversed by the fluid to be filtered from the outside to the inside in a radial direction with respect to the longitudinal axis 28 of the filter insert. The filter media 30a, 30b are each embodied as a star-folded filter bellows. The upper end disk 32 of the prefilter element 22 is releasably coupled or couplable to the housing cover 18 via a bayonet connection 34. The pre-filter element 22 is held on the underside by a lower end disc 36. The main filter element 24 is retainingly disposed between the upper end disc 38 and the lower end disc 40. A lattice-shaped support tube 42 is provided for radially inwardly supporting the filter media 30a, 30b of the prefilter element 22 and the main filter element 24, respectively. The filter media 30a, 30b preferably rest directly on the inside against the respective support tube 42.

The

end discs

36, 38 of the pre-filter element 22 and the main filter element 24, which end discs correspond to each other, i.e. the lower end disc 36 of the pre-filter element 22 and the upper end disc 38 of the main filter element 24, are arranged spaced apart from each other in the axial direction. The two

end disks

36, 38 are sealed (fluid-tight) against the filter housing 12 on the inside by sealing

elements

44, 46. The two

end discs

36, 38 thus serve as sealing discs, by means of which the filter housing 12 is divided in the axial direction inside into a pre-filter chamber 48 with the pre-filter element 22 and a main filter chamber 50 with the main filter element 24. A flow channel 52 for fluid pre-filtered by the pre-filter element 22 is arranged between the upper end disc 38 of the main filter element 24 and the lower end disc 36 of the pre-filter element 22. The flow duct 52 is delimited directly in the axial direction by the

end discs

38, 40 of the pre-filter element and the

main filter element

22, 24, which end discs correspond to one another. To direct the fluid to be filtered to the pre-filter element 22, the filter housing 12 has a first inlet 54.

The upper end disk 38 of the main filter element 24 and the lower end disk 36 of the pre-filter element 22 are in this case, for example, formed integrally with one another and can be embodied, in particular, as a plastic injection molded part. Between the two

end disks

36, 38, spacer elements 56 are arranged, which are formed on the two

end disks

36, 38, respectively.

The flow channel 52 is of substantially annular design. The flow channel 52 is in fluid connection on the outlet side in the operating position of the filter insert 20 with a laterally (radially laterally) arranged lateral outlet 58 of the filter housing 12. A pump (not shown) may be coupled at the side outlet 58. The pump is used to draw contaminated fluid through the first inlet 54 to the unfiltered side 60 of the pre-filter chamber 48, through the pre-filter element 22 to the clean side 62 of the pre-filter chamber 48, and through the flow passage 52 to the side outlet 58. The pump is also used to pump pre-filtered fluid drawn from filter housing 12 via a second inlet 64 of filter housing 12 to an unfiltered side 66 of main filter chamber 50 of filter housing 12 for directing the pre-filtered fluid through filter media 30b of main filter element 24 to a clean side 68 of main filter chamber 50. The first inlet 54, the second inlet 64 and the side outlet 58 are each arranged on the filter housing 12 axially offset relative to one another.

The main filter element 24 can have a water separation unit 70 radially within its filter medium 30b for separating the water contained in the fluid. The water separation unit 70 here advantageously comprises a coalescing medium 72 which is arranged annularly around the longitudinal axis 28 of the filter insert. Coalescing media 72 may be disposed downstream of filter media 30b of main filter element 24, as shown in fig. 1, particularly in fluid connection. The coalescing media 72 may be constructed in a single layer or multiple layers as desired and made of, for example, a nonwoven fabric. The water separation unit 70 and the two

filter elements

22, 24 are arranged coaxially with the longitudinal axis 28 of the filter insert. After flowing through the prefilter element 22 and the main filter element 24, the fluid passes through the water separator unit 70 to an axial outlet 74, which is formed on a housing base 76 of the filter tank 14.

Spaced apart from the axial outlet 74, a water outlet 78 for water separated from the fluid is also formed on the housing bottom 76. The axial outlet 74 and the water outlet 76 are surrounded by an annular connection piece 80 within the filter housing 12. The lower end disk 40 of the main filter element 24 rests sealingly with a sealing element 82 against the annular socket 80 in the operating position of the filter insert 20. Unfiltered fluid is thereby prevented from flowing under the main filter element 24 toward the axial outlet 74 or filtered fluid from the clean side 68 to the main filter drain 100.

Radially inside the annular connection piece 80, between the water outlet 78 and the axial outlet 74, an annular barrier 84 extends, which engages around the axial outlet 74. In this way, a water collecting channel 86 is formed between the annular connection 80 and the annular barrier 84, which leads into the water outlet 78. The water separation unit 70 rests sealingly against the annular barrier 84 in the operating position. Water separated from the fluid flows into the water collection channel 86 during operation of the fluid filter 10 based on gravity and exits the filter housing 12 through the water outlet 78.

The filter pot 14 has an inner cross section which tapers axially toward the housing base 76, i.e. in stages along the introduction direction 88 for the filter insert. The filter housing 12 thus has, in the region of its inner wall 90, sealing surface sections 92a-d for sealing abutment against the

end discs

36, 38, 40 of the filter insert 20, which become less distant from the longitudinal axis 26 of the filter housing towards the housing base 76 with increasing distance from the inlet opening 16 of the filter housing 12. The sealing

elements

44, 46 on the

end disks

36, 38 assigned to one another and the further sealing element 94 of the upper end disk 38 of the main filter element 24 and the sealing element 96 of the lower end disk 40 of the main filter element 24 are at different distances from the longitudinal axis 28 of the filter insert in a corresponding manner and in the operating position of the filter insert 20 in the filter housing 12 shown rest sealingly against the sealing surface sections 92a-d of the filter pot 14. The filter insert 20 can thereby be simplified and inserted into its operating position in the filter housing 12 without unnecessary stress being generated in its

sealing elements

44, 46, 94, 96.

The sealing

elements

46 and 94 of the upper end disk 38 of the main filter element bear against the sealing surfaces 92b and 92c, so that in the operating position of the filter insert 20 the prefilter outlet 98 for the prefilter element 22 is closed against fluid flow. In the operating position, the main filter outlet 100 for the main filter element 24 is likewise closed against fluid flow by the sealing contact of the sealing element 96 of the lower end disk 40 against the sealing surface 92d and the sealing contact of the sealing element 82 against the annular connection piece 80. The operation of the

vents

98, 100 is discussed in detail in fig. 2.

Fig. 2 shows the fluid filter 10 of fig. 1 with the filter insert 20 arranged in a drain position. To replace the filter insert 20, the housing cover 18 is first unscrewed from the filter canister 14. The filter insert 20 is lifted in the axial direction by means of a bayonet connection 34 with the housing cover 18. The filter insert 20 is therefore removed from the filter pot 14 of the filter housing 12 in a section 102 opposite the introduction direction 88, so that it is in the drainage position shown.

By removing the filter insert 20 from the filter tank 14, the sealing element 46 comes out of engagement with the sealing surface 92 b. In a similar manner, the sealing element 44 reaches into the region of the (covered) bypass channel on the upper side of the sealing surface 92 a. Thereby creating a fluid connection between the unfiltered side 60 of the prefilter element 22 and the prefilter drain 98 and a fluid connection between the clean side 62 of the prefilter element 22 and the prefilter drain 98 via the flow passage 52. The fluid in the pre-filter chamber 48 can thus flow under the influence of gravity into the pre-filter outlet 98 arranged below the pre-filter element 22 and be discharged from the filter housing 12.

The sealing element 94 remains in engagement with the sealing surface 92c in the drainage position of the filter insert. Unfiltered, contaminated fluid is thereby prevented from reaching the main filter chamber 50. Thereby avoiding unwanted ingress of contaminants into the main filter chamber 50. The filter insert 20 is preferably retained in the drain position until the pre-filter chamber 48 has been at least approximately completely emptied before it is completely removed from the filter tank 14.

In the drain position, the sealing element 96 is also lifted up to above the sealing surface 92 d. Thereby opening a flow path from the unfiltered side 66 of the main filter chamber 50 to the main filter drain 100. Fluid on the unfiltered side 66 can thus flow under the influence of gravity first into the drain channel 104, which is formed between the sealing surface 92d and the annular nozzle 80. In this manner, fluid flows from the vent passage 104 out of the filter housing 12 via the main filter vent 100.

By the abutment of the sealing element 94 against the sealing surface 92c, the main filter outlet 100 is also sealed in the drainage position relative to the pre-filter outlet 98. The annular connection piece 80 is dimensioned over its length such that the sealing element 82 also bears sealingly against the annular connection piece 80 in the drainage position. Overflow of fluid from drain passage 104 to clean side 68 of main filter element 24 is thereby avoided.

Only after the fluid on the unfiltered side 66 has flowed out of the outlet channel 104 at least approximately completely, does the filter insert 20 continue to be lifted from the drainage position in the axial direction, so that the sealing element 82 is disengaged from the annular connection piece 80. In this way, fluid on the clean side 68 of the main filter element 24 may flow into the main filter drain 100 via the drain passage 104 if fluid is not drawn through the axial outlet 74. By designing the emptying sequence of the

filter chambers

48, 50 to be provided, the entry of contaminants into the clean side 68 of the main filter element 24 can be reliably avoided when removing or replacing the filter insert 20. Furthermore, since the two

filter chambers

48, 50 each have their own

separate outlet

98, 100, a rapid and thorough emptying of the filter housing 12 can be achieved.

After the filter insert 20 is completely removed from the filter canister 14, the filter canister is disengaged from the housing cover 18 and a new filter insert 20 is secured to the housing cover 18. The filter insert 20 is then inserted into the filter tank 14 along the introduction direction 88 and is transferred into its installation position (see fig. 1) by screwing the housing cover 18 onto the filter tank 14.

Claims

1. Fluid filter (10) comprising:

-a filter housing (12),

a filter insert (20) which is arranged in the filter housing (12) in an exchangeable manner, having a prefilter element (22) and having a main filter element (24) which are arranged one above the other in the filter housing (12) in the direction of a longitudinal axis (26) of the filter housing,

wherein the filter housing (12) has a pre-filter discharge (98) for the pre-filter element (22) and a main-filter discharge (100) for the main-filter element (24) which is configured separately from the pre-filter discharge (98),

wherein the prefilter outlet (98) and the main filter outlet (100) are each closed in a fluid-tight manner in an operating position of the filter insert (20) in the filter housing (12), and wherein, in a drainage position of the filter insert (20), the unfiltered side (60) of the prefilter element is fluidically connected to the prefilter outlet (98) and the unfiltered side (66) of the main filter element is fluidically connected to the main filter outlet (100), the filter insert (20) being transferable into the drainage position by an axially directed removal movement of the filter insert (20) from its operating position, wherein the prefilter outlet (98) and the main filter outlet (100) are sealed off from one another in the drainage position of the filter insert (20).

2. The fluid filter according to claim 1, characterized in that the fluid filter (10) is for fuel.

3. The fluid filter according to claim 1, characterized in that the fluid filter (10) is for oil.

4. The fluid filter according to claim 1, characterized in that the prefilter drain (98) and the main filter drain (100) are sealed against one another in the drainage position of the filter insert (20) by sealing abutment of the filter insert (20) on the filter housing (12).

5. The fluid filter according to claim 1, characterized in that the filter insert (20) in its operating position in the filter housing (12) bears sealingly against the filter housing (12) for the fluid-tight closure of the pre-filter discharge (98) and the main filter discharge (100).

6. The fluid filter according to one of claims 1 to 5, characterized in that the filter insert (20) rests sealingly against the filter housing (12) in its operating position with at least one end disk (36, 38, 40) of each of the pre-filter element (22) and the main filter element (24).

7. The fluid filter according to one of claims 1 to 5, characterized in that the filter housing (12) has a housing bottom (76) with an end-side axial outlet (74) for the fluid, which is sealed in the drainage position of the filter insert (20) with respect to the pre-filter drain (98) and the main filter drain (100).

8. The fluid filter according to claim 7, characterized in that the axial outlet (74) at the end is surrounded by an annular connection piece (80) of the filter housing (12) arranged in the filter housing (12), and the filter insert (20) in the operating position and the drainage position bears sealingly against the annular connection piece (80) of the filter housing (12).

9. The fluid filter according to claim 8, characterized in that the filter insert (20) rests sealingly with the end discs (40) of the pre-or main filter elements (22, 24) against an annular connection piece (80) of the filter housing (12) in the operating position and in the drainage position.

10. The fluid filter according to claim 7, characterized in that the end-side axial outlet (74) is fluidically connected to the clean side (62, 68) of the prefilter element (22) or the main filter element (24) in the operating position of the filter insert (20).

11. The fluid filter according to one of claims 1 to 5, characterized in that the filter housing (12) has a filter pot (14) with an inner diameter which tapers in stages from the inlet opening (16) of the filter housing (12) towards its housing bottom (76).

12. The fluid filter according to one of claims 1 to 5, characterized in that a flow channel (52) for the fluid is arranged between the prefilter element (22) and the main filter element (24), which flow channel is directly delimited in the direction of the longitudinal axis (26) of the filter housing by end discs (36, 38) of the prefilter element (22) and the main filter element (24) which correspond to one another, wherein the filter housing (12) has a lateral outlet (58) into which the flow channel (52) opens.

13. The fluid filter according to claim 12, characterized in that the two end discs (36, 38) of the pre-filter element (22) and of the main filter element (24) which directly delimit the flow channel (52) are constructed integrally with one another.

14. A fluid filter according to any one of claims 1-5, characterised by a water separation unit (70) for separating water contained in the fluid.

15. The fluid filter according to claim 14, characterized in that the water separation unit (70) is arranged radially inside the pre-filter element (22) and the main filter element (24) and can be flowed by the fluid in sequence through the filter elements (22, 24) with the water separation unit (70).

16. A fluid filter according to claim 5, characterised in that the filter housing (12) has a water outlet (78) on the housing bottom (76) for water separated from the fluid, which water outlet is surrounded by an annular connection piece (80) in the radial direction.

17. The fluid filter according to one of claims 1 to 5, characterized in that the prefilter element (22) and the main filter element (24) are each configured as a circular filter element and are arranged coaxially to a longitudinal axis (26) of the filter housing (12).

18. The fluid filter of claim 17, wherein the pre-filter element (22) and the main filter element (24) are each configured as a circular filter element having star-folded filter media (30 a, 30 b).

19. Filter insert (20) of a fluid filter (10) according to one of claims 1 to 5, having a pre-filter element (22) and having a main filter element (24), which are arranged one behind the other in the direction of a longitudinal axis (28) of the filter insert (20).