Liquid filter and volume compensation element for a liquid filter

Abstract

The invention relates to a liquid filter, comprising: a housing (2) comprising a cover (3); a liquid inlet (4) and a liquid outlet (5); and a filter element (20), which is arranged in an interior (6) of the housing (2) and comprises a first end cap (21) facing the cover (3), a second end cap (22) and a filter medium (23) arranged between the two end caps (21, 22) in an axial direction (A), wherein the filter element (20) separates a purified side (7) from an original side (8). The liquid filter further comprises a volume compensation element (40) comprising an elastically reversibly compressible central body (41) having a central body interior (42), wherein the central body interior (42) encloses an initial volume in the uncompressed state and a final volume in the compressed state, wherein the volume difference between the final volume and the initial volume corresponds to at least 35% of the maximum volume change of the liquid in the liquid filter (1) under normal pressure in the temperature range between +90° C. and -40° C. The volume compensation element (40) comprises a first sealing area (50) surrounding the central body (41), wherein the first sealing area (50) is designed to cooperate with the housing (2) and the cover (2) in the fully assembled state of the liquid filter (1) in such a way that the interior (6) of the housing is sealed fluid-tightly from the exterior (9) of the liquid filter (1). The volume compensation element (40) has a second sealing region (60) surrounding the central body (41), wherein the second sealing region (60) is designed to prevent a fluid short circuit between the clean side (7) and the raw side (8).

Description

Field of the Invention

[0001] The present invention relates to a liquid filter and a volume compensation element for a liquid filter. Background Art

[0002] In a liquid filter, depending on the type of liquid to be filtered, it can happen that the liquid in the liquid filter strongly changes its specific volume and / or assumes another physical state upon a temperature change and thereby undergoes a strong volume increase (for example when water freezes to ice). The resulting risk is that the housing of the liquid filter may be damaged by the volume increase.

[0003] Therefore, it is known from the prior art that in a liquid filter, which is used, for example, for a liquid urea solution (DENOX) for catalytic reduction of nitrogen oxides in the automotive field, a volume compensation element is provided inside the housing, which is not filled with liquid but is elastically deformable. When the volume of the liquid in the housing increases, the volume compensation element is compressed by the additional volume and in this way prevents an excessive pressure increase on the housing wall.

[0004] Such a volume compensation element is known from document DE 10 2017 203 796 A1. Summary of the Invention

[0005] The recognition on which the present invention is based is that in a liquid filter (in which the purified side is separated from the raw side inside), two types of seals are necessary to ensure the functionality of the liquid filter.

[0006] The first type of seal relates to an external seal, i.e., sealing the interior of the liquid filter, in which there is liquid, relative to the external space of the liquid filter. This external seal is independent of whether the liquid in the interior is on the (filtered) purified side or on the (unfiltered) raw side. In other words: the liquid filter must be sealed and not allow leakage to the outside.

[0007] The second type of seal relates to an internal seal inside the liquid filter. Inside, a filter element is usually arranged through which the liquid to be filtered flows, specifically from the raw side to the purified side. For effective filtration and thus the mode of operation, it is important that no accidental fluid short - circuit occurs between the raw side and the purified side (an exception can be an over - pressure situation, which is prevented, for example, by an over - pressure valve). In other words: inside, unfiltered liquid should not reach the purified side past the filter element from the raw side, and conversely, filtered liquid should not reach the raw side from the purified side.

[0008] In the case of a liquid filter having a housing and a cover, the external seal is usually caused by a housing seal arranged between the housing and the cover, for example in the form of a separate O - ring.

[0009] For an internal sealing arrangement, the filter element is sealed relative to the housing by means of at least one first filter element seal, for example in the form of a separate O-ring. Depending on the arrangement of the (uncleaned) liquid inlet, the (cleaned) liquid outlet, and the type of filter arrangement (axial or radial flow-through), a second filter element seal may also be required, for example in the form of a separate O-ring.

[0010] It has been shown that providing a plurality of different sealing devices, such as O-rings and their assembly during the assembly of a liquid filter, is cost-intensive and the logistics are complex (e.g., in the case of warehousing, providing replacement parts, etc.), and errors may occur during assembly, for example, caused by forgetting one of the sealing devices or mixing different sealing devices. Due to the large number of different parts, there is a risk that the liquid filter may not be functional, for example, after maintenance, because of external leakage or fluid short-circuiting inside the liquid filter. In a liquid filter having a volume compensation element, this volume compensation element is additionally an element to be prepared, stored, and assembled, which additionally increases the complexity of logistics, storage, and assembly. Furthermore, it may be difficult to securely hold the volume compensation element in its set position inside the filter during multiple compression and decompression cycles (e.g., freezing with the volume compensation element compressed and thawing with the volume compensation element decompressed). If a secure hold in position is not achieved, there is a risk that the volume compensation element may adversely affect the internal or external seal, the liquid inlet or outlet, the filter element, or the particles already deposited in the filter element due to a change in position.

[0011] There may thus be a need to provide a liquid filter having a volume compensation element, in which the external and internal seals are permanently ensured in a reliable manner, which can be assembled and maintained simply and with a small number of assembly steps, in which the number of mutually separate and mutually assemblable parts is kept small, and in which the volume compensation element is reliably and permanently held substantially in a fixed position inside the liquid filter so as not to affect the functionality of the liquid filter and so that the particles already deposited in the filter element are not dislodged by the movement of the volume compensation element.

[0012] Advantages of the invention:

[0013] This need can be met by the content of the independent claims of the present invention. Advantageous embodiments of the invention are described in the dependent claims.

[0014] According to a first aspect of the present invention, a liquid filter is provided, which includes a housing having a cover, an inlet for the liquid and an outlet for the liquid, and a filter element. The filter element is arranged inside the housing and has a first end cap facing the cover, a second end cap, and a filter medium arranged axially between the two end caps. The filter element separates a purified side from a raw side. The liquid filter further has a volume compensation element, which has a centrally located body that can be elastically and reversibly compressed and has an internal space within the centrally located body. The internal space of the centrally located body encloses an initial volume in the uncompressed state and encloses a final volume in the compressed state. Here, the volume difference between the final volume and the initial volume corresponds to at least 35%, preferably at least 50%, particularly preferably at least 75%, and most particularly preferably at least 90% of the maximum volume change of the liquid in the liquid filter at normal pressure within a temperature range between +90 °C and -40 °C. Alternatively or additionally, the initial volume is at least 20% larger than the final volume, or at least 30% larger than the final volume, particularly preferably at least 50% larger than the final volume, and most particularly preferably at least twice as large as the final volume (i.e., 100% larger than the final volume). The volume compensation element has a first sealing area or a first sealing portion area surrounding the centrally located body, wherein the first sealing area is configured to cooperate with the housing and the cover in the fully assembled state of the liquid filter such that the interior of the housing is fluid-tightly sealed from the external space of the liquid filter. The volume compensation element has a second sealing area or a second sealing portion area surrounding the centrally located body, wherein the second sealing area is configured to prevent fluid short-circuiting between the purified side and the raw side. The second sealing area can be arranged, for example, in the area of the cover in the assembled state of the liquid filter.

[0015] Here, the final volume can be defined, for example, as the volume occupied by the volume compensation element in a state completely compressed by the possible liquid volume change.

[0016] In other words: The volume compensation element has a sealing device for external sealing and at least partially has a sealing device or a part of the sealing device for internal sealing.

[0017] Advantageously, a volume compensation element can be used to prevent damage to the housing when the volume of the liquid changes. Additionally, at least two sealing devices (e.g., O-rings) implemented as separate elements can be advantageously saved, one for external sealing and one for internal sealing. This advantageously simplifies the logistics of all necessary parts for providing a liquid filter, simplifies warehousing, facilitates assembly by saving the assembly steps for two separate sealing devices, and improves the reliability of assembly (e.g., during initial assembly or after maintenance), as it is impossible to forget one of the saved separate sealing devices. Furthermore, advantageously, if the first sealing area and / or the second sealing area are arranged on the volume compensation element such that they occupy the positions of the original sealing devices for external and internal sealing in the assembled state, traditional filter cartridges, traditional housings, and traditional cover parts can also be used in the liquid filter. In this way, it is advantageously possible to use existing parts, thus eliminating the costs for modification and tooling costs.

[0018] The term "comprising" can be understood synonymously with the term "including" in the context of this application.

[0019] The inlet, for example, can be arranged for the liquid to be filtered, while the outlet, for example, can be arranged for the filtered liquid.

[0020] The axial direction should be understood as the direction along the longitudinal axis of the liquid filter or the filter cartridge. The radial direction should be understood as the direction perpendicular to the axial direction.

[0021] The filter cartridge can be configured, for example, as a hollow cylinder, such as a cylindrical shape. The filter cartridge can be configured, for example, to be rotationally symmetric, where the longitudinal axis can be used as the axis of symmetry.

[0022] The volume compensation element is arranged to be compressed when the volume of the liquid enclosed within the liquid filter changes and reduces the pressure increase on the housing and the cover, such that the overall housing-cover is not damaged, for example, during the transformation of liquid water into ice.

[0023] The central body can be configured, for example, as an open cavity into which the liquid in the liquid filter cannot enter. However, the central body can also be configured as a closed cavity. The central body can be configured to be elastically reversible, such that the central body occupies its initial volume and possibly even its initial shape again when the pressure weakens (e.g., when the ice melts). Either gas (air) or an elastically reversible compressible foam can be located in the cavity. The central body can assume most of the volume change functionality of the volume compensation element, for example, greater than 90%.

[0024] The volume compensation element can have an inner section when looking from the inside outwards. Looking radially outwards, an intermediate section or connecting section adjoins the inner section. Looking radially outwards, an outer section or outer end section adjoins the intermediate section or connecting section. A central body can be arranged, for example, in the inner section. In the intermediate section or connecting section, the volume compensation element can protrude outwards from the central body approximately in the radial direction. The volume compensation element can be constructed in a closed loop or can protrude from the central body in the form of spokes or ribs. The volume compensation element can be guided approximately along the axial direction, for example, at the end of the connecting section. In the outer section or outer end section, the volume compensation element can extend, for example, along the radial direction.

[0025] The first sealing area causing the external seal can be arranged, for example, more externally than the second sealing area when looking in the radial direction.

[0026] The second sealing area can be spaced further away from the upper end of the central body than the first sealing area when looking in the axial direction. Here, when looking in the axial direction, the upper end of the central body can be arranged between the upper side of the cover and the second sealing area.

[0027] The volume compensation element can be constructed, for example, rotationally symmetric. Here, for example, the longitudinal axis of the liquid filter can be used as the axis of symmetry. The longitudinal axis of the liquid filter can also be, for example, the longitudinal axis of the volume compensation element.

[0028] By constructing the volume compensation element in one piece, the volume compensation element can be manufactured, transported, stored, and assembled particularly cost-effectively. The risk of incorrect assembly is advantageously reduced. The volume compensation element can be manufactured, for example, by means of an injection molding method. The term "one piece" can be understood to mean that the volume compensation element cannot be disassembled without damage. For example, a compressible element, such as a foam plastic part, can be arranged in the cavity surrounded by the central body. If such a compressible element cannot be removed from the cavity without damaging the central body and / or the foam plastic body, then the compressible element can be a component of the volume compensation element constructed in one piece.

[0029] By constructing the volume compensation element as an element separate from the filter element, the volume compensation element can be simply replaced during maintenance advantageously. Here, the volume compensation element can be arranged releasably and without damage on the inside or in the interior of the liquid filter. Preferably, the volume compensation element is not connected to the liquid filter (to another element, such as the filter element, the cover, or the housing) by material locking.

[0030] By surrounding the inner space with the filter medium, where the central body extends into the inner space of the filter medium, a particularly space-saving embodiment of the volume compensation element is advantageously provided. At the same time, this advantageously and particularly effectively prevents damage to the filter medium surrounding the inner space during volume expansion of the liquid.

[0031] The volume compensation element can, for example, extend into the interior space along the axial direction by at least 50% or at least 75% of the length of the interior space.

[0032] Alternatively or additionally, the volume compensation element can extend into the interior space by at least 5 mm, preferably at least 10 mm.

[0033] Here, the interior space can, for example, extend between two sides of the first end cap or the second end cap facing the interior space.

[0034] By the first end cap having a channel-shaped first opening through which the central body extends into the interior space of the filter medium, it advantageously causes: the volume compensation element to be axially position-fixed and secured in the liquid filter. In addition, this facilitates the precise assembly of the volume compensation element, since the first opening serves as an assembly aid (key-lock principle).

[0035] The first opening can be configured as a through-hole in the first end cap. The first opening can be centrally arranged in the first end cap.

[0036] For example, it can be provided that the central body has substantially the same diameter as the first opening in the region of the first opening in the uncompressed state.

[0037] In addition, for example, it can be provided that the second end cap has a channel-shaped second opening. For example, it can be provided that such a second opening fluidically connects the interior space of the filter element to the inlet or the outlet.

[0038] By the first end cap having an inner neck protruding in the direction of the cover member, with the volume compensation element being arranged at least sectionally between the free end of the inner neck and the cover member when viewed in the axial direction, it advantageously causes: the volume compensation element to be axially position-fixed and secured in the assembled state of the liquid filter or to have only a small axial movement clearance. This can, for example, prevent particles deposited in the filter medium from being shaken off by the moving volume compensation element.

[0039] The volume compensation element can, for example, be clamped between the free end of the inner neck and the cover member. Then, there is always mechanical contact with the free end of the inner neck and the cover member. In this way, the volume compensation element is held particularly position-fixed.

[0040] The volume compensation element can be arranged in the region of the connecting section between the free end of the inner neck and the cover member.

[0041] The inner neck can, for example, be centrally arranged on the first end cap. The inner neck can, for example, surround the first opening. The inner neck can, for example, completely surround the first opening, i.e., without interruption when viewed in the circumferential direction.

[0042] The inner neck can project here, for example, on the side of the first end cap facing away from the filter medium.

[0043] It can be provided, for example, that the inner wall of the inner neck is spaced apart from the edge of the first opening when viewed in the radial direction, for example, by at least 10% or at least 20% of the opening diameter and / or by at least 3 mm or at least 5 mm or at least 8 mm.

[0044] The first sealing region is arranged in the outer end section of the volume compensation element when viewed in the radial direction, wherein the first sealing region is compressed or squeezed or deformed between the housing and the cover in the axial direction and / or in the radial direction in the assembled state of the liquid filter, and advantageously reliably ensures the external seal in a simple manner. The external seal is automatically ensured by the assembly of the volume compensation element, eliminating the risk of forgetting the sealing device for the external seal.

[0045] Here, if the first sealing region is arranged axially between the cover and the housing, the first sealing region can be used as a radial seal. If the first sealing region is arranged radially between the housing and the cover, the first sealing region can act as a radial seal. It can also be that, if the first sealing region is arranged, for example, on a surface of the housing inclined with respect to the axial direction and is pressed against this surface by the cover, the first sealing region acts not only as an axial seal but also as a radial seal.

[0046] In an expansion scheme of the present invention, it is provided that the first end cap has an outer neck projecting in the direction of the cover, wherein the second sealing region is arranged on the underside of the volume compensation element facing away from the cover, and wherein the second sealing region is compressed or squeezed or deformed between the inner wall of the housing and the outer wall of the outer neck in the axial direction and / or in the radial direction in the assembled state of the liquid filter.

[0047] This advantageously causes the internal seal to be substantially achieved on the outer side of the first end cap, thereby achieving a small bend or a large radius of curvature of the second sealing region. This advantageously results in a large sealing surface and material protection. It can be advantageously provided that the second sealing region replaces the sealing device (such as an O-ring) for traditional internal seals, and thus the conventionally used filter element can be reused.

[0048] The outer neck is arranged radially more outwardly than the inner neck (if such an inner neck exists). The outer neck can surround or enclose the inner neck, as long as such an inner neck exists.

[0049] The outer neck, for example, may have a free end. The free end, for example, may point substantially in the axial direction towards the cover member. In the region of the free end, for example, a radially outwardly protruding edge may be provided. This edge, for example, may not protrude radially outward as far as the first end cap. For example, it may be provided that the upper side of the end cap, the radially outwardly directed part of the outer wall of the outer neck, and the wall side of the edge facing away from the cover member form a groove. For example, it may be provided that the second sealing region is arranged in the groove. For example, it may be provided that the inner wall of the housing has a recess in the groove region. This recess or the first recess, for example, may be used to guide the second sealing region through between the inner wall of the housing and the edge and arrange it in the groove. A recess in the housing wall or another recess (axially further spaced from the cover member compared to the said recess or the first recess) may also form a housing-side support surface or sealing surface for the second sealing region or extend the internal sealing path for the internal seal and thereby improve the internal seal.

[0050] It may be provided that the free end of the inner neck has a greater spacing from the first end cap than the free end of the outer neck when viewed in the axial direction. That is, the inner neck may protrude axially beyond the outer neck.

[0051] The second sealing region may be arranged, for example, in the outer end section of the volume compensation element when viewed in the radial direction. The second sealing region may, for example, be completely arranged on the side of the volume compensation element facing away from the cover member.

[0052] Depending on whether a sealing surface is formed on the apparent inner wall of the housing and the outer wall of the outer neck, an axial, radial or mixed axial-radial sealing effect can be achieved. At least a partially radial sealing effect can be particularly advantageous here, because this sealing effect can already be achieved by means of a press fit through the structural design of the housing, the filter element and the volume compensation element without the application of axial pressure, for example by means of a threaded connection of the cover member.

[0053] In an expansion scheme of the present invention, it is provided that the second sealing region is pressed or squeezed or deformed between the inner wall of the cover member and the outer wall of the inner neck in the axial direction and / or in the radial direction in the assembled state of the liquid filter.

[0054] Here, the cover member may extend, for example, inclined relative to the axial direction in the contact region with the second sealing region, for example, at an angle between 20° and 70° relative to the axial direction, preferably between 35° and 60°.

[0055] This enables the filter element to be assembled or disassembled particularly easily, simply, and with little effort, because the second sealing region, or rather the second sealing part region, does not bear against the filter element and the inner wall of the housing during assembly, and thus, no friction needs to be overcome when inserting or removing the filter element from the housing. The internal seal in the cover region can advantageously be precisely adjusted by the axial position of the cover relative to the housing. If the cover is, for example, screwed onto the housing, the pressing of the second sealing region can be increased by stronger tightening and thus the sealing effect can be improved. The radial sealing effect can be adjusted by the configuration of the contact region of the second sealing region with the outer wall of the outer neck and the shaping of the outer neck in this contact region, or by the configuration of the cover in the contact region with the second sealing region.

[0056] Here, for example, the second sealing region of the volume compensation element can be arranged, for example, in the connecting section.

[0057] The inner neck can have a recess or groove along the radial direction on its outer side in the contact region with the second sealing region, which serves as a supporting surface or a sealing surface for the second sealing region.

[0058] A shoulder can be formed on the outer wall of the inner neck, which projects radially outwards, and the second sealing region can be at least partially supported on this shoulder.

[0059] In an expansion scheme of the present invention, it is provided that the second sealing region projects radially outwards from the central body of the volume compensation element, wherein the second sealing region is axially spaced apart from the upper end of the central body facing the cover, and wherein the second sealing region presses or compresses against the inner wall of the inner neck and / or against the upper side of the first end cap facing the cover in the assembled state of the liquid filter.

[0060] Here, for example, it can be provided that the second sealing region is axially spaced apart from the upper end of the central body by at least 75% of the distance, for example, between the cover and the first end cap.

[0061] This advantageously causes the first sealing region for external sealing and the second sealing region for internal sealing to be spatially constructed significantly separately from each other. Thus, for example, the second sealing region can be made of a material different from that of the first sealing region by simple means, for example, by a two-component injection molding method. Additionally advantageously, in this way, the second sealing region serves as a stop element and an axial positioning aid when the volume compensation element is assembled in the filter element. During assembly, the volume compensation element can simply be pressed axially against the filter element until the second sealing region bears against the upper side of the first end cap. In this way, the axial position of the volume compensation element can be adjusted repeatedly and precisely in a simple manner, thereby always ensuring the correct function of the liquid filter even in difficult installation conditions.

[0062] Furthermore, advantageously, a particularly large sealing surface can be achieved in this way for internal sealing and for particularly reliably preventing a fluid short circuit between the purification side and the raw side. Finally, the second sealing region can in this way serve as a safety valve in the case of a sudden pressure shock in the direction of the interior space of the filter medium (for example in the case of a fully compressed volume compensation element). In this case, for example, the second sealing region can be configured such that it releases the first opening when a adjustable pressure peak is exceeded and thus enables a rapid pressure reduction in the direction of the cover part. Thereby, damage to the filter medium can be advantageously prevented.

[0063] By configuring the first sealing region as an elastic sealing lip or an elastic sealing projection, a particularly good external sealing effect is advantageously achieved.

[0064] Here, the sealing projection can be configured with a greater material thickness compared to the adjacent region. The sealing lip can be configured with a particularly flexible shape.

[0065] By configuring the second sealing region as an elastic sealing lip or an elastic sealing projection, a particularly good internal sealing effect is advantageously achieved.

[0066] The first sealing region and / or the second sealing region can for example be made of an elastic material or an elastomer. The first sealing region and / or the second sealing region can for example have at least one material from the following group: rubber, raw rubber, silicone, fluoroelastomer, ethylene and propylene monomers, copolymer composed of butadiene and acrylonitrile, neoprene.

[0067] According to a second aspect of the invention, a volume compensation element is proposed.

[0068] The volume compensation element is provided for assembly in a liquid filter that separates a purification side from a raw side. The volume compensation element includes a centrally located body that can be elastically and reversibly compressed and has a central body interior space. The central body interior space encloses an initial volume in the uncompressed state and a final volume in the compressed state, where the initial volume is at least 20% larger than the final volume, or at least 30% larger than the final volume, particularly preferably at least 50% larger than the final volume, and most preferably at least twice as large as the final volume (i.e., 100% larger than the final volume). The volume compensation element has a first sealing region surrounding the central body, where the first sealing region is configured to fluid-tightly seal the interior of the liquid filter from the external space of the liquid filter; and the volume compensation element has a second sealing region surrounding the central body, where the second sealing region is configured to prevent a fluid short circuit between the purification side and the raw side.

[0069] At least two sealing devices (e.g., O-rings) implemented as separate elements can thus be advantageously integrated into a single element. This advantageously simplifies the logistics of all the necessary parts for providing a liquid filter, simplifies warehousing, facilitates assembly by saving the assembly of two separate sealing devices, and improves the reliability of the assembly (e.g., at first assembly or after maintenance), since it is impossible to forget one sealing device. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Additional features and advantages of the present invention will become apparent to those skilled in the art from the following description of exemplary embodiments with reference to the accompanying drawings. However, each exemplary embodiment should not be construed as a limitation of the present invention. The drawings illustrate:

[0071] FIG. 1: A schematic cross-section of a liquid filter known from the prior art;

[0072] Figure 2a : A schematic cross-section of a liquid filter;

[0073] Figure 2b : Figure 2a Details of the internal and external seals of the liquid filter of

[0074] Figure 2c : Figure 2a A cross-sectional perspective view of the volume compensation element of the liquid filter of

[0075] Figure 3a : A schematic cross-section of another liquid filter;

[0076] Figure 3b : Figure 3a Details of the internal and external seals of the liquid filter of

[0077] Figure 3c : For the liquid filter according to Figure 3a A cross-sectional perspective view of the volume compensation element of the liquid filter of

[0078] Figure 4a : A schematic cross-section of another liquid filter;

[0079] Figure 4b : Figure 4a Details of the internal and external seals of the liquid filter of

[0080] Figure 4c : For Figure 4a A cross-sectional perspective view of the volume compensation element of the liquid filter of DETAILED DESCRIPTION

[0081] FIG. 1 shows a schematic cross-section of a liquid filter 1 of the prior art.

[0082] The liquid filter 1 comprises a housing 2 with a cover 3, a liquid inlet 4 and a liquid outlet 5, as well as a filter element 20. The filter element 20 is arranged inside 6 the housing 2 and has a first end cap 21 facing the cover 3, a second end cap 22 and a filter medium 23 arranged between the two end caps 21, 22 in the axial direction A. The second end cap 22 faces here the bottom 14 of the cup-shaped housing 2. The direction of gravity can point here, for example, from the cover 3 to the bottom 14. The filter element 20 separates the purified side 7 (on which the filtered liquid is present) from the raw side 8 (on which the liquid to be filtered is present). The first end cap 21 has a channel-shaped first opening 26. The second end cap 22 has a channel-shaped second opening 27. The filter element 20 is here constructed in a hollow cylindrical shape and encloses the internal space 25 between the first end cap 21 and the second end cap 22. The first end cap 21 has a first support element 24a which projects towards the cover 3. The second end cap 22 has a second support element 24b which projects towards the bottom of the housing (downwards in the drawing). By means of the two support elements 24a, 24b, the filter element 20 is clamped between the cover 3 and the bottom and is thus fixed in a substantially position-fixed manner along the axial direction A. In FIG. 1, a volume compensation element 40 is arranged below the filter element 20, which can be elastically reversibly compressed between an initial volume and a final volume: the volume compensation element can accommodate an additional volume in the case of a change in the liquid volume in the interior 6 in such a way that it is compressed starting from the initial volume. Thereby, the pressure load on the housing 2 and the cover 3 is reduced.

[0083] The external seal between the interior 6 of the liquid filter 1 and the external space 9 is achieved by a housing seal 70 which is here constructed, for example, as a separate O-ring.

[0084] The internal seal between the raw side 8 and the purified side 7 is achieved by a first filter element seal 71 and a second filter element seal 72, which are arranged radially outside the first end cap 21 or the second end cap 22 and seal the two end caps 21, 22 in a radially sealed manner relative to the housing 2.

[0085] The axial direction A extends here along the longitudinal axis of the liquid filter 1 or the filter element 20. The radial direction R extends perpendicular to the axial direction A. The rotational direction U encircles the axial direction A.

[0086] Figure 2a A schematic cross-section of the liquid filter 1 is shown.

[0087] Differently from the liquid filter 1 of FIG. 1, in Figure 2aThe liquid filter 1 shown in FIG. 4 has a volume compensation element 40 having a central body 41 that can be elastically reversibly compressed and having a central body inner space 42. The central body inner space 42 surrounds an initial volume in an uncompressed state and surrounds a final volume in a compressed state. The volume difference between the final volume and the initial volume corresponds to at least 35% of the maximum volume change of the liquid in the liquid filter 1 under normal pressure in a temperature range between +90° C. and -40° C. Alternatively or additionally, it is provided that the initial volume is at least 20% larger than the final volume, or at least 30% larger than the final volume, particularly preferably at least 50% larger than the final volume, and quite particularly preferably at least twice as large as the final volume (i.e. 100% larger than the final volume). The volume compensation element 40 has a first sealing area 50 surrounding the central body 41, wherein the first sealing area 50 is configured to seal the interior 6 of the liquid filter 1 relative to the outer space 9 of the liquid filter 1 in a fluid-tight manner, that is, the first sealing area 50 contributes to the external sealing of the liquid filter 1 or ensures the external sealing. The volume compensation element 40 also has a second sealing area 60 surrounding the central body 41, wherein the second sealing area 60 is configured to prevent a fluid short circuit between the clean side 7 and the raw side 8, at least in the area of ​​the cover 3, i.e., the second sealing area contributes to or ensures the internal sealing of the liquid filter 1. In this embodiment, a second filter element seal 72 is also provided in the area of ​​the bottom 14 of the housing 2 in order to improve the internal sealing.

[0088] In another (not shown here) embodiment, in which the inlet 4 is realized by the cover 3, for example, the lower end cap 22 can be configured without the second opening 27. The liquid can then, for example, flow into the space between the filter element 20 and the housing 2 and leave the liquid filter 1 through the outflow 5. In this case, the second filter element seal 72 can be omitted, and the volume compensation element 40 with its two sealing areas 50, 60 alone brings about the external and internal sealing.

[0089] In the exemplary embodiment shown, the volume compensation element 40 is designed merely by way of example to be essentially rotationally symmetrical.

[0090] Viewed in the radial direction R, the volume compensation element 40 can be divided from the center into the following sections or regions: a central body 41 is arranged in the center, which extends downward in the axial direction A from an upper end 46 of an upper side 45 of the volume compensation element 40 in a cup-shaped manner. The central body 41 functionally assumes the majority of the volume compensation. The upper side 45 is initially designed to be planar and extends outward from the cup-shaped central body 41 approximately in the radial direction R. This section can be referred to as a connecting section 47 or a middle section, which serves to connect the central body 41 at least to the first sealing area 50.

[0091] The connecting region 47 is adjoined radially further outward by an outer section or outer region or outer end region 43. A first sealing region 50 is arranged in this outer end region 43, which extends to the radial end of the volume compensation element 40. The outer end region combines the sealing function of the volume compensation element. Thus, the two functions (volume compensation and sealing) are spatially separated in the radial direction in this embodiment, whereby, for example, the material thickness can be advantageously adapted to the respective function.

[0092] The connecting region 47 can be designed as a closed surface, but it can also be designed in the form of spokes or in the manner of connecting ribs and serve to connect the central body 41 to the outer end region 43 .

[0093] The volume compensation element 30 is designed in one piece in this exemplary embodiment only by way of example, ie the central body 41 , the first sealing area 50 and the second sealing area 60 cannot be separated from one another without causing damage. They can be produced, for example, by an injection molding process.

[0094] The volume compensation element 30 is designed here merely as an example as an element separate from the filter insert 20 and is not connected thereto in a materially bonded manner.

[0095] The central body 41 projects into the interior 25 of the filter medium 23. In this exemplary embodiment, the volume compensation element 40 is arranged in the intermediate space between the housing 2 and the first, upper end cap 21. The central body 41 projects into the interior 25 of the filter medium 23 through the first channel-shaped opening 26 in the first end cap 21.

[0096] The central body 41 projects into the interior 25 along the axial direction A along approximately 80% to 90% of the length L of the interior 25 . The length L corresponds here, for example, to the distance between the two end shields 21 , 22 as viewed in the axial direction A.

[0097] The first opening 26 can be arranged, for example, centrally in the first end cap 21 .

[0098] The first end cap 21 has an inner neck 28 protruding in the direction of the cover 3. The inner neck 28 surrounds or encircles or surrounds the first opening 26. The inner wall 30 of the inner neck 28 is arranged at a distance from the edge of the first opening 26. The neck distance K corresponds to, for example, approximately half the diameter of the first opening 26. The neck distance K can be, for example, at least 3 mm or at least 5 mm.

[0099] Here, the volume compensation element 40 is arranged at least in sections between the free end 29 of the inner neck 28 and the cover 3, as seen in the axial direction A. The volume compensation element 40 can be clamped between the free end 29 and the cover 3, thereby causing axial and / or radial fixing of the volume compensation element 40 or a narrowing of the movement play.

[0100] The first sealing area 50 is arranged in the outer end section 43 of the volume compensation element 40 when viewed in the radial direction R, wherein the first sealing area 50 is pressed between the housing 2 and the cover 3 in the axial direction A and / or in the radial direction R. In the illustrated embodiment, the inner wall 10 of the housing 2 has a recess 13 in the area where the first sealing area 50 abuts against the inner wall 10 of the housing. A sealing projection configured as the first sealing area 50 is supported on the recess 13 having an approximately horizontal or slightly inclined support surface. The cover 3 has an edge that is inserted into the interior 6 of the housing 2, and this edge presses the first sealing area 50 radially outward slightly inclined against the recess 13 from above when the cover 3 is tightened, and thus presses the first sealing area 50 between the cover 3 and the inner wall 10 of the housing. Thereby, an external seal is produced. The first sealing area 50 can also be configured, for example, as a sealing lip or a sealing strip (Dichtschnur) or have another configuration that causes an external seal of the liquid filter 1.

[0101] The first end cover 21 has an outer neck 32 that projects in the direction of the cover 3, wherein the second sealing area 60 is arranged on the underside 44 of the volume compensation element 40 facing away from the cover 3, and wherein the second sealing area 60 is pressed between the inner wall 10 of the housing and the outer wall 33 of the outer neck 32 in the axial direction A and / or in the radial direction R in the assembled state of the liquid filter 1.

[0102] The second sealing area 60 is configured as a sealing projection here and projects from the underside 44 of the volume compensation element 40 in an L-shape, wherein the horizontal part of the "L" shape points radially inwards.

[0103] In the illustrated embodiment, an edge 34 projects in the radial direction R from the free end 37 of the outer neck 32. This edge 34 and the outer wall 33 of the outer neck 32 and the upper side 36 of the first end cover 21 facing the cover 3 form a groove 35. The second sealing area 60 configured as a sealing projection is received in the groove 35. The vertical part of the "L" shape guides past the edge 34 externally. In this way, a particularly long internal sealing path 61 is produced: on the one hand, the sealing projection seals between the outer neck 32 and the inner wall 10 in the groove 35. In addition, the section of the "L" shape that is guided along the edge 34 and arranged or pressed between the edge 34 and the inner wall 10 can also contribute to the internal seal.

[0104] The second sealing area 60 configured as a sealing projection can here replace the first filter element seal 71 that is usually present there with no major modification to the structural design of the housing 2 and / or the filter element 20.

[0105] When assembling the liquid filter 1, for example, the volume compensation element 40 can first be inserted or pushed into the filter element 20 through the first opening 26, for example, and then the filter element 20 can be inserted into the housing 2. Disassembly can be carried out in the reverse order. Here, the volume compensation element can be reused according to its state.

[0106] The central body 41 is constructed as hollow in the illustrated embodiment or the central body 41 surrounds a tubular or cup-shaped cavity, the central body internal space 42. The central body 41 or the volume compensation element 40 is arranged in the liquid filter 1 such that the cavity cannot be filled with liquid. The cavity is filled with a gas, for example, air. In another embodiment, the central body internal space 42 can also be filled with a slightly compressible elastomer or slightly compressible foam plastic and is closed around.

[0107] The filter element 20 is constructed as a hollow cylinder here and is flowed through radially from the outside to the inside. The opposite flow direction can also be considered. A filter element 20 that can be flowed through axially can also be considered. The filter medium 23 can be, for example, star-folded and made of filter paper. The filter medium 23 can also be coated. An embodiment can also be considered in which the filter medium 23 is made of, for example, a meltblown non-woven fabric or other artificial fibers. The filter medium 23 is provided for depositing particles and / or dirt from the liquid, for example, particles larger than 20 μm, preferably larger than 10 μm, and very particularly preferably larger than 1 μm.

[0108] Figure 2b Shown Figure 2a Details of the internal and external seals of the liquid filter 1 shown. The internal seal path 61 is shown here by a thicker line. The part of the second seal area 60 that extends in the area of the recess 13 of the inner wall 10 of the housing can also contribute to the internal seal path 61.

[0109] In addition, the external seal path 51 of the first seal area 50 is shown as a slightly thicker line. This line shows where or how the seal of the interior 6 of the housing 2 with respect to the external space 9 is caused.

[0110] In Figure 2b In the detail view, the horizontal section of the volume compensation element 40 extends above the outer neck 32 and its free end 37 on the left side of the first seal area 50 (when looking along the axial direction A). In other words: There is a gap (marked by two horizontal lines) circumferentially between the upper end of the outer neck 32 and the volume compensation element 40. Of course, there can also be an embodiment in which the volume compensation element 40 is supported on the upper end of the outer neck 32 in this area.

[0111] Figure 2c Shown Figure 2a4 is a perspective view of a cross section of a volume compensation element 40. It is clearly visible that the volume compensation element 40 is essentially rotationally symmetrical. In addition, an axial offset can be seen at the end of the connecting section 47. The inner neck 28 is bridged by this axial offset. As a result, the volume compensation element 40 can be mounted exactly in its radial nominal position and is also held essentially stationary there, for example by a slight excess of the diameter of the inner neck 28 relative to the end of the connecting section 47.

[0112] The volume compensation element 40 has here a hollow central body 41. However, in another embodiment, the central body can also be filled, for example with a well-compressible foamed plastic.

[0113] Figure 3a A schematic cross section of another liquid filter 1 is shown.

[0114] Figure 3a Liquid filter 1 with Figure 2a The difference between the liquid filter 1 and the second sealing area 60 lies mainly in the position of the second sealing area 60 on the volume compensation element 40 and the position of the internal seal in the liquid filter 1. In addition, the volume compensation element 40 is filled or formed by a very well compressible material at the center body. The material can be, for example, a foam plastic or an elastomer that can be elastically and reversibly deformed.

[0115] exist Figure 3a In the liquid filter 1 shown, the second sealing area 60 is no longer Figure 2a The second sealing area is arranged almost directly adjacent to the first sealing area 50 and slightly below it. Instead, the second sealing area is arranged at the axially offset lower end of the transition between the connecting area 47 and the outer end area 43 (see Figure 2a ). The second sealing area 60 can be configured, for example, as a sealing projection, i.e., a thickening. The second sealing area is pressed or squeezed or deformed between the inner wall 11 of the cover and the outer wall 31 of the inner neck 28 in the axial direction A and / or in the radial direction R. In this exemplary embodiment, the cover 3 in the contact area 12 with the second sealing area 60 extends only obliquely relative to the axial direction A, for example, at an angle W between 20° and 70°, here about 45°, relative to the axial direction.

[0116] Here, the outer wall 31 of the inner neck 28 can have a small, for example groove-shaped, recess 39 , in which the second sealing area 60 is received and which increases the contact area or sealing surface and enables precise positioning of the second sealing area 60 on the inner neck 28 .

[0117] Alternatively or additionally, a shoulder 38 can be configured on the outer wall 31 of the inner neck 28, which projects radially outwardly and on which the second sealing region 60 can be supported at least in part. Instead of the shoulder 38, the inner neck 28 can also have another support surface.

[0118] The contact or sealing zone for internal sealing or the internal sealing path 61 is mainly formed between the outer wall 31 of the inner neck 28 and the second sealing region 60 or between the second sealing region 60 and the cover part 3.

[0119] Figure 3b Shown Figure 3a Details of the internal and external sealing of the liquid filter 1 shown. The internal sealing path 61 and the external sealing path 51 are in turn shown by thicker lines.

[0120] It can be seen that there is a missing area between the outer neck 32 and the inner neck 28 that was left empty in Figures 2a to 2c the embodiment. Instead, in Figure 3b a shoulder 38 of platform type is configured in the right region of the inner neck 28. On this shoulder 38, a horizontal section of the volume compensation element 40 is supported on the left side of the first sealing region 50. In principle, gaps can exist here but also as in Figure 2a and 2b such that the volume compensation element 40 is not supported. Moreover, embodiments can also be given in which, as in Figure 2a and 2b there is an empty space between the inner neck 28 and the outer neck 32.

[0121] Furthermore, a groove-like recess 39 is clearly visible, for example. The cooperation of the recess 39 or the wall of the groove with the thickening or the sealing projection of the volume compensation element 40 in the second sealing region 60 results in a particularly good internal seal. In addition, the internal sealing path 61 is extended thereby.

[0122] Figure 3c Shown Figure 3a A cross-sectional perspective view of the volume compensation element for a liquid filter shown. However, the volume compensation element 40 shown in Figure 3c is now configured with a hollow central body interior space 42 (instead of being configured with a filled central body 41 as in Figure 2c ), like the volume compensation element 40 in Figure 3a . Clearly visible is the second sealing region 60 configured as a sealing projection at the transition of the lower side of the volume compensation element 40 to the connection region 47 to the outer end region 43.

[0123] Figure 4a A schematic cross-section of another liquid filter 1 is shown.

[0124] Figure 4a The liquid filter 1 and Figure 2a and 3a The difference between the liquid filters mainly lies in the position of the second sealing region 60 on the volume compensation element 40 and thus the location where internal sealing is caused in the liquid filter 1. In addition, the volume compensation element 40 is filled or formed at the location of the central body with a material that can be very well compressed here (see also Figure 3a ). This material can be, for example, a foam plastic or an elastomer that can be elastically reversibly deformed, etc.

[0125] In Figure 4a the liquid filter 1 shown, the second sealing region 60 projects radially outward from the central body 41 of the volume compensation element 40, wherein the second sealing region 60 is axially spaced from the upper end portion 46 of the central body 41 facing the cover part 3 in the axial direction A. The second sealing region 60 presses or bears against the inner wall 30 of the inner neck 28 and / or against the upper side of the first end cap 21 facing the cover part 3.

[0126] The first sealing region 50 is located on another element or branch protruding from the central body 41 or on a protruding disk different from the second sealing region 60. Here, the first sealing region 50 is arranged on a branch or element or disk protruding on the upper end portion 46 of the central body.

[0127] The second sealing region 60 is here spaced from the upper end portion 46 by at least about 80% to 90% of the spacing D between the cover part 3 and the first end cap 21, however at least 30%, preferably at least 50% and particularly preferably at least 75%. Most particularly preferably, the second sealing region 60 is spaced from the upper end portion 46 between 95% and 105% of this spacing D, for example 100%. Then a particularly long internal sealing path 61 is produced.

[0128] The second sealing region 60 here completely covers the first opening 26. As a sealing region or contact region or internal sealing path 61 for the internal sealing of the liquid filter, a radial seal is produced here not only between the radially outer end of the second sealing region 60 and the inner wall 30 of the inner neck 28. At the same time, an axial seal or internal sealing path 61 can also be produced between the lower side of the second sealing region 60 in this plane and the upper side 36 of the first end cap 21 by means of the axial pressure exerted by the cover part 3 on the upper end portion 46 of the volume compensation element 40.

[0129] The precise and simple assembly of the volume compensation element 40 in the filter element 20 can also be achieved by the second sealing region 60 that projects radially outward and covers the first opening 26. Once the volume compensation element 40 abuts with its second sealing region 60 against the upper side 36 of the first end cap 21, further axial displacement is no longer possible, and the assembler knows that the target position has been reached.

[0130] Figure 4b shows Figure 4a Details of the internal and external seals of the liquid filter 1. The internal seal path 61 and the external seal path 51 are again shown by thicker lines.

[0131] It can be seen that here there is a Figures 2a to 2c void area in the embodiment between the outer neck 32 and the inner neck 31. However, the horizontal section of the volume compensation element 40 is supported on the upper end of the outer neck 32 to the left of the first sealing area 50. In principle, however, there can also be a gap as in Figure 2a and 2b such that the volume compensation element 40 is not supported.

[0132] The inner neck 28 has a short (substantially horizontally extending) shoulder 38 on its radial outer side, which, however, does not extend through to the outer neck 32.

[0133] Figure 4c shows Figure 4a A cross-sectional perspective view of the volume compensation element for the liquid filter 1. However, the volume compensation element 40 shown in Figure 4c is now constructed with a hollow central body interior space 42 (instead of a filled central body 41 as in Figure 2c ) like the volume compensation element 40 in Figure 4a . Clearly visible is the planar configuration of the second sealing area 60 with sealing protrusions arranged on the radially free ends.

[0134] Finally, it should be noted that the volume compensation element 40 and the liquid filter 1 can be used, for example, in a water filter or for an aqueous solution, such as in a filter for an aqueous urea solution for DENOX applications in the automotive field. However, in principle, use in diesel filters, oil filters, and gasoline filters can also be considered.

Claims

1. A liquid filter comprising: - a housing (2) having a cover (3); - an inlet (4) for the liquid and an outlet (5) for the liquid; - a filter element (20) which is arranged in the interior (6) of the housing (2) and has a first end cap (21) facing the cover (3), a second end cap (22) and a filter medium (23) arranged in the axial direction between the two end caps (21, 22), wherein: The filter element (20) separates the purified side (7) from the raw side (8); a volume compensation element (40) having an elastically reversibly compressible central body (41) with a central body interior space (42), wherein the central body interior (42) encloses an initial volume in the uncompressed state and a final volume in the compressed state, wherein the volume difference between the final volume and the initial volume corresponds to at least 35% of the maximum volume change of the liquid in the liquid filter (1) at normal pressure in a temperature range between +90° C. and -40° C.; The volume compensation element (40) has a first sealing area (50) surrounding the central body (41). wherein the first sealing area (50) is configured to cooperate with the housing (2) and the cover (3) in a fully assembled state of the liquid filter (1) so that the interior (6) of the housing is sealed in a fluid-tight manner with the exterior space (9) of the liquid filter (1), The volume compensation element (40) has a second sealing area (60) surrounding the central body (41). The second sealing area (60) is designed to prevent a fluid short circuit between the clean side (7) and the raw side (8).

2. The liquid filter according to claim 1, wherein: The volume compensation element (40) is designed in one piece.

3. The liquid filter according to claim 1 or 2, wherein: The volume compensation element (40) is constructed as an element separate from the filter element (20).

4. The liquid filter according to claim 1 or 2, wherein: The filter medium (23) surrounds an inner space (25), Therein, the central body (41) projects into the interior space (25) of the filter medium (23).

5. The liquid filter according to claim 4, wherein: The first end cap (21) has a channel-shaped first opening (26), wherein the central body (41) projects through the first opening (26) into the interior (25) of the filter medium (23).

6. The liquid filter according to claim 1 or 2, wherein: The first end cap (21) has an inner neck portion (28) protruding toward the cover (3). The volume compensation element (40) is arranged at least in sections between the free end (29) of the inner neck (28) and the cover (3) as viewed in the axial direction.

7. The liquid filter according to claim 1 or 2, wherein: The first sealing area (50) is arranged in an outer end section (43) of the volume compensation element (40) as viewed in the radial direction. The first sealing area (50) is pressed between the housing (2) and the cover (3) in an axial direction and / or in a radial direction when the liquid filter (1) is in an assembled state.

8. The liquid filter according to claim 1 or 2, wherein: The first end cap (21) has an outer neck portion (32) protruding toward the cover (3). wherein the second sealing area (60) is arranged on an underside (44) of the volume compensation element (40) facing away from the cover (3), The second sealing area (60) is pressed between the housing inner wall (10) and the outer wall (33) of the outer neck (32) in the axial direction and / or in the radial direction when the liquid filter (1) is in an assembled state.

9. The liquid filter according to claim 6, wherein: The second sealing area (60) is pressed between the inner wall (11) of the cover and the outer wall (31) of the inner neck (28) in the axial direction and / or in the radial direction when the liquid filter (1) is assembled. Therein, the cover (3) extends in a contact area (12) with the second sealing area (60).

10. The liquid filter according to claim 6, wherein: The second sealing area (60) protrudes radially outward from the central body (41) of the volume compensation element (40), wherein the second sealing area (60) is spaced apart from an upper end (46) of the central body (41) facing the cover (3) in the axial direction, The second sealing area (60) is pressed against the inner wall (30) of the inner neck (28) and / or against the upper side (34) of the first end cap (21) facing the cover (3) when the liquid filter (1) is in an assembled state.

11. The liquid filter according to claim 1 or 2, wherein: The first sealing area (50) is configured as an elastic sealing lip or an elastic sealing protrusion, and / or The second sealing area (60) is configured as an elastic sealing lip or an elastic sealing protrusion.

12. The liquid filter according to claim 1, wherein The second sealing area (60) is designed to prevent a fluid short circuit between the clean side (7) and the raw side (8) in the area of ​​the cover (3).

13. The liquid filter according to claim 4, wherein: The central body (41) extends into the interior space (25) of the filter medium (23) along at least 50% of the length of the interior space (25) in the axial direction.

14. The liquid filter according to claim 4, wherein: The central body (41) extends into the interior (25) of the filter medium (23) along at least 75% of the length of the interior (25) in the axial direction.

15. The liquid filter according to claim 6, wherein: The volume compensation element (40) is clamped between the free end (29) of the inner neck (28) and the cover (3) when viewed in the axial direction.

16. The liquid filter according to claim 9, wherein The cover element (3) extends obliquely with respect to the axial direction in a contact area (12) with the second sealing area (60).

17. The liquid filter according to claim 9, wherein: The cover element (3) extends in a contact region (12) with the second sealing area (60) at an angle of between 20° and 70° relative to the axial direction.

18. The liquid filter according to claim 10, wherein The second sealing area (60) is spaced apart from the upper end (46) of the central body (41) facing the cover (3) in the axial direction by at least 75% of the distance between the cover (3) and the first end shield (21).

19. A volume compensation element, which is designed to be installed in a liquid filter, which separates a purified side (7) from a raw side (8), in, The volume compensation element (40) comprises a central body (41) which can be elastically and reversibly compressed and has a central body inner space (42). wherein the central body interior space (42) encloses an initial volume in an uncompressed state and a final volume in a compressed state, wherein the initial volume is at least 20% greater than the final volume, The volume compensation element (40) has a first sealing area (50) surrounding the central body (41), wherein the first sealing area (50) is designed to seal the interior (6) of the liquid filter (1) from an exterior space (9) of the liquid filter (1) in a fluid-tight manner, The volume compensation element (40) has a second sealing area (60) surrounding the central body (41), wherein the second sealing area (60) is designed to prevent a fluid short circuit between the clean side (7) and the raw side (8).

20. The volume compensation element according to claim 19, wherein: The initial volume is at least 30% greater than the final volume.

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