FILTER ELEMENT FOR FILTERING A FLUID STREAM

Description

[0001] The present invention relates to a filter device with a filter element for filtering lubricating oil, according to the preamble of claim 1 or according to the preamble of claim 8.

[0002] If a fluid flow flows through a filter element, this results in a pressure drop in the fluid flow across the filter element. The lower the filter fineness of a filter body, the higher the pressure drop in the fluid flow across the filter body. In order to avoid an excessive, undesirable pressure drop, a filter element can have a plurality of filter bodies, each with a different filter fineness, which form different filter stages. A filter element can furthermore have at least one bypass valve for bypassing one or more filter stages. The pressure drop across the filter element or which filter stages the fluid flow flows through depends on the viscosity of the fluid flow, whereby the viscosity of the fluid flow depends on the temperature of the fluid flow. The filter fineness of the respective filter body and the at least one bypass valve can be designed such that, depending on the temperature orDepending on the viscosity of the fluid flow, different filter bodies are flowed through, thereby achieving different degrees of purity of the filtered fluid flow.

[0003] The filter element can be arranged in a filter housing with a cover and have fixing tabs that engage with the cover when the cover is arranged on the filter housing and the filter housing is in the closed position, whereby the filter element is centered in the filter housing, even if the filter housing is in an inclined installation position. A disadvantage is that the fixing tabs only engage with the cover when the filter housing is in the closed position. If the cover is removed from the filter housing, e.g. when changing the filter element, the filter element is no longer centered in the filter housing by the fixing tabs. When the cover is removed, the filter element rests against the inner walls of the filter housing, which makes changing the filter element more difficult. A further disadvantage is that water and oil aging products are only inadequately separated by the filter element.

[0004] WO 01 / 38744 A1 discloses a filter comprising a filter element with different filter stages and a protective filter body arranged in the filter element. Furthermore, a bypass for bypassing the filter element is formed in the filter element. Furthermore, the filter element has a spacer edge, which is arranged circumferentially in the housing at a distance from one another. The spacer edge fluidically separates the filter stages of the filter element from one another.

[0005] DE 10 2017 003 732 A1 discloses a filter in which a fine filter is arranged downstream of a main filter.

[0006] The present invention therefore addresses the problem of providing an improved or at least alternative embodiment for a filter element, which in particular prevents the filter element from contacting the filter housing when the filter element is changed and which makes it possible to separate water and oil aging products from the fluid flow when filtering the fluid flow.

[0007] The present invention therefore addresses the problem of providing an improved or at least alternative embodiment for a filter element, which enables an improvement in the filtration performance of the filter element.

[0008] This problem is solved according to the invention by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

[0009] The present invention is based on the general idea of ​​providing a fluid device for filtering lubricating oil, preferably in a wind turbine, with at least one fluid filter element for filtering lubricating oil. The filter device has at least one substantially cylindrical filter housing in which the respective filter element is arranged. An annular space extending along a longitudinal center axis of the filter housing is formed between an inner wall of the filter housing and the filter element. A cylindrical, three-stage filter element for filtering lubricating oil is provided, comprising a cylindrical fine filter body forming a fine filter stage, a cylindrical main filter body forming a main filter stage, and a cylindrical protective filter body forming a protective filter stage, and comprising a first end plate.on which at least one bypass valve is formed for bypassing the fine filter stage and the main filter stage, and with an intermediate disc which axially connects the fine filter body to the main filter body, wherein the fine filter body and the main filter body axially follow one another and enclose a cavity of the filter element, so that the fine filter stage and the main filter stage are arranged fluidically parallel, and wherein the protective filter body is arranged in this cavity, so that the protective filter stage is fluidically downstream of the fine filter stage and the main filter stage, in which according to a first solution according to the invention at least two radially projecting spacer elements are formed on the intermediate disc, spaced from one another in the circumferential direction and distributed over the circumference of the intermediate disc,through which the filter element is supported on the filter housing when changing the filter element. The spacer elements are formed from axially and radially extending ribs, and the respective filter element is supported radially on the filter housing via the spacer elements. This is advantageous because it facilitates changing the filter element. The spacer elements center the filter element in the middle of the filter housing. This is advantageous because it enables uniform filtration of the fluid flow. The spacer elements are expediently designed so that they represent the lowest possible flow resistance for the fluid flow flowing through the filter element. The fluid flow is freed of impurities as it flows through the filter element.The larger part of the fluid flow is filtered at the main filter body and the protective filter body, and the smaller part at the fine filter body. The fluid flow flows through the filter element from the outside to the inside. If the oil is cold, e.g., during the start-up of a wind turbine, the oil has a high viscosity. As a result, only a very small part of the fluid flow can flow through the main filter stage and the fine filter stage. This increases the pressure acting on the bypass valve, which causes the bypass valve to open. The fluid flow or oil flows through the bypass valve into the cavity and then through the protective filter stage. This makes it possible to supply a wind turbine with filtered lubricating oil even when the turbine is started up. If the oil heats up during operation and subsequently circulates in the wind turbine in a warm state, a larger part of the fluid flow is able toto flow through the main filter stage. This results in a pressure drop at the respective bypass valve, which leads to the closure of the bypass valve. The heated fluid flow essentially flows through the main filter stage and then the protective filter stage, although small portions of the fluid flow may also flow through the fine filter stage. If the oil or fluid flow is hot, the fluid flow flows through the fine filter stage and the main filter stage simultaneously and then the protective filter stage, whereby the required degree of purity of the fluid flow is achieved by the main filter stage and the fine filter stage. At the protective filter stage, cleaning of the fluid flow essentially only takes place when the fluid flow flows through the bypass valve in a contaminated state and then through the protective filter stage. The fluid flow is particularly thoroughly freed of contaminants by the fine filter stage.while the main filter stage and the bypass valve prevent an excessive pressure drop in the fluid flow at the filter element. It is conceivable that the at least one bypass valve is designed in the manner of a pressure-sequence valve. If a defined pressure is built up at the bypass valve by the fluid flow, the bypass valve opens. If the defined pressure at the bypass valve falls below, the bypass valve closes. It is conceivable that the fine filter body and the main filter body comprise a filter material that includes glass fibers, and that the protective filter body comprises a wire mesh. It is also possible that fixing tabs are arranged on the first end plate. The filter housing can have a cover for closing the filter housing. The cover can have receiving openings complementary to the fixing tabs, into which the fixing tabs engage.The filter element is centered in the filter housing by the fixing tabs when the cover is placed on the filter housing or when the filter housing is closed. The fixing tabs protrude axially from the first end plate, and it is conceivable that the fixing tabs and / or the first end plate are manufactured by injection molding.

[0010] The filter element presented here can be used as an exchangeable unit in a filter housing of a filter device that serves to filter the fluid flow.

[0011] A preferred embodiment is one in which at least one of the filter bodies, i.e. the fine filter body and / or the main filter body and / or the protective filter body, is designed as a ring filter body through which the fluid flow to be filtered flows radially during operation of a filter device equipped with the filter element in order to achieve the respective filtration task. Ring filter bodies of this type with radial flow are characterized by a relatively small space requirement with a relatively large flow-through cross-section and thus by a comparatively low back pressure. An embodiment in which at least the protective filter body is designed as a ring filter body is particularly advantageous, as it can be accommodated relatively easily in the interior space or cavity of the filter element enclosed by the fine filter body and the main filter body.The optimal variant is one in which all three filter bodies are designed as ring filter bodies.

[0012] To achieve a particularly large filtration area, a pleated filter material is preferably used for the respective filter body. In a ring filter design, the filter material is then pleated in a star shape. This applies to the fine filter body and / or the main filter body and / or the protective filter body, preferably at least to the fine filter body and / or the main filter body.

[0013] According to a second solution according to the invention, it is provided that at least the fine filter body is designed to absorb water and / or adsorb oil aging products from the fluid flow. In addition to the fine filter body, the main filter body can also be designed to absorb water and / or adsorb oil aging products from the fluid flow. It is expedient to reduce the water content in the oil to a minimum. If water is present in the oil, water vapor bubbles can form during a pressure drop, which implode when the pressure increases. Furthermore, water acts as a type of catalyst and accelerates the tendency of the oil to oxidize. This creates long-chain, insoluble and depositing oil aging products such as resins, sludge or varnish. This results in increased wear and maintenance costs, e.g. of a wind turbine in which the oil circulates.The formation of oil aging products reduces the oil's ability to serve as a coolant. Accordingly, it is particularly advantageous if the fine filter body and, if applicable, the main filter body are designed to absorb both water and adsorb oil aging products. The two inventive solutions presented here can be implemented separately, i.e., independently of one another, or together, i.e., cumulatively.

[0014] According to an advantageous embodiment, the fine filter body and / or the main filter body can contain a superabsorbent for absorbing water. A superabsorbent is a plastic, usually a polymer, capable of absorbing several times its own weight in a polar liquid, particularly water. Upon absorption of the liquid or water, the superabsorbent swells and forms a hydrogel. In other words, the fine filter body or the main filter body can contain a superabsorbent, i.e., water-absorbing polymer that forms a hydrogel upon absorption of water.

[0015] Preferably, the fine filter body or the main filter body can have at least one water-absorbing layer containing the superabsorbent or the water-absorbing polymer, in particular as a powder, granulate, or fiber. The water-absorbing layer extends, in particular, in a ring shape and coaxially with the rest of the fine filter body or the main filter body.

[0016] Advantageously, the water-absorbing layer may comprise a polyester fleece comprising two fleece layers, between which the superabsorbent or water-absorbing polymer is arranged. The polyester fleece may be laminated to fix the two layers together and thus secure the superabsorbent or water-absorbing polymer between the layers, i.e., within the polyester fleece.

[0017] According to another advantageous embodiment, the fine filter body and / or the main filter body can have a filter layer arrangement for adsorbing oil aging products. This arrangement has several filter layers with different filter finenesses and is arranged in the fine filter body or the main filter body such that the filter fineness increases in the direction of flow through the filter body. As a result, the filtration effect increases in the direction of flow from filter layer to filter layer, which promotes the permanent storage or adsorption of relatively long-chain oil aging products without resulting in an excessive pressure loss. The filter fineness correlates with the filtration effect, which correlates with the mesh size or pore size, which in turn correlates with the permeability for solids to be filtered out.The smaller the mesh size or pore size, the finer the filter material and the smaller the solids it can retain. The filter layer arrangement, or rather its filter layers, extends in a ring-shaped manner and coaxially with the rest of the fine filter body.

[0018] The filter layer arrangement can expediently comprise at least two filter layers, namely a coarse filter layer and a fine filter layer, which are arranged in the flow direction of the fine filter body such that the flow passes through the coarse filter layer first and then the fine filter layer. Advantageously, the filter layer arrangement can comprise at least three filter layers, namely a coarse filter layer, a medium filter layer, and a fine filter layer, which are arranged in the flow direction of the fine filter body such that the flow passes through the coarse filter layer first, then the medium filter layer, and finally the fine filter layer.

[0019] Advantageously, each filter layer of the filter layer arrangement can be formed from a glass fiber fabric. The glass fiber fabrics used in the various filter layers differ from one another in terms of their mesh sizes and permeabilities.

[0020] A particularly advantageous embodiment is one in which at least one filter layer of the filter layer arrangement contains the superabsorbent or is formed by a water-absorbing layer containing the superabsorbent. This gives the filter layer arrangement an additional function, namely as a water absorber. Alternatively, the water-absorbing layer can be provided in addition to the filter layer arrangement, downstream or preferably upstream of it.

[0021] The fine filter body or the main filter body comprises a filter material that can be constructed in multiple layers, such that it can include the aforementioned water-absorbing layer and / or the aforementioned filter layer arrangement. Additional layers can also be provided, such as one or more wire layers to stabilize the filter material and / or one or more plastic layers to protect the glass fiber layers. The filter material can be folded in a star shape to form the annular filter body.

[0022] The main filter body can also expediently have a filter layer arrangement for adsorbing oil aging products, which can be designed similarly to the above-described filter layer arrangement of the fine filter body, although the filtration effect of the fine filter body is smaller or finer. Additionally or alternatively, the main filter body can also have such a water-absorbing layer, which can be provided above for the fine filter body. Ultimately, more volume is available in the main filter body for more superabsorbent, so that more water can be absorbed overall.

[0023] It is of course conceivable that at least two radially projecting spacer elements are formed on the intermediate disc, spaced apart from one another in the circumferential direction and distributed over the circumference of the intermediate disc, by means of which the filter element is supported on the filter housing when the filter element is changed and that at the same time the fine filter body is designed to absorb water and oil ageing products from the fluid flow.

[0024] One possible embodiment proposes that the fine filter body has a filter mesh of 3µm + / - 1µm, the main filter body a filter mesh of 10µm + / - 3µm, and the protective filter body a filter mesh of 50µm + / - 10µm. In this context, the filter mesh is defined as 99.5% of particles with a particle size of the respective mesh size being filtered out of the fluid stream. This means, for example, that a filter element with a filter mesh of 10µm can filter out 99.5% of particles with a particle size of at least 10µm from the fluid stream.

[0025] According to the invention, the spacer elements are formed from axially and radially extending ribs. This is advantageous because an intermediate disk with axially and radially extending ribs can be manufactured relatively inexpensively and because the axially and radially extending ribs allow the fluid flow to pass between the ribs. The ribs present only a low flow resistance to the fluid flow, thereby largely avoiding an undesirable pressure drop at the ribs.

[0026] In a further embodiment of the invention, the filter element can have a second end plate having a central outlet opening. The protective filter body is arranged in the region of the second end plate such that the fluid flow from the cavity can only flow through the protective filter body to the outlet opening. This essentially prevents the fluid flow from the cavity out of the filter element without first at least partially flowing through the protective filter body. This is advantageous because it improves the filtration performance of the filter element. The contaminated fluid flow that has flowed through the at least one bypass valve flows through the protective filter body and leaves the filter element in the filtered state through the outlet opening of the second end plate.

[0027] In another embodiment, the protective filter body can have an open end plate and a closed end plate, the protective filter body being radially and tightly supported on the fine filter body or the main filter body via its open end plate in the region of the second end plate. This largely prevents the fluid flow between the fine filter body or the main filter body and the protective filter body from flowing past the open end plate. The fluid flow is deflected in the region of the second end plate by the open end plate such that the fluid flow flows through the protective filter body and is freed from at least the coarsest contaminants. It is of course possible for parts of the fluid flow to flow through the protective filter body beforehand.The fluid flow flows through the open end plate of the protective filter body and then leaves the filter element through the central outlet opening of the second end plate.

[0028] According to a further advantageous embodiment, the protective filter body can have radially projecting support elements on its closed end plate, which are distributed circumferentially and arranged at a distance from one another. The protective filter body is radially supported by the support elements on the fine filter body, the main filter body, or the intermediate plate. As a result, the protective filter body is centered in the cavity. This is advantageous because it enables uniform flow through the protective filter body. The fluid flow can flow past the closed end plate between two adjacent support elements. It is advantageous for the support elements to be designed such that the flow resistance offered by the support elements to the fluid flow is as low as possible.

[0029] A filter element of the type described above can be arranged in a substantially cylindrical filter housing, wherein an annular space extending along a longitudinal center axis of the filter housing is formed between an inner wall of the filter housing and the filter element. The filter element is supported radially on the filter housing via the spacer elements. The filter element is further centered in the filter housing by the spacer elements such that the longitudinal center axis of the filter element runs substantially parallel to the inner wall of the filter housing or parallel to the longitudinal center axis of the filter housing, whereby the annular space always has the same diameter. This is advantageous because it enables uniform filtration of the fluid flow.

[0030] A filter device with at least one filter element of the type described above, which is arranged in a substantially cylindrical filter housing, is preferably used in a wind turbine for filtering lubricating oil.

[0031] Further important features and advantages of the invention emerge from the subclaims, from the drawings and from the associated description of the figures based on the drawings.

[0032] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0033] Preferred embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, wherein the same reference numerals refer to the same or similar or functionally identical components.

[0034] They show, schematically Fig. 1 is an isometric view of a filter element according to the invention, Fig. 2 is a top view of the filter element according to the invention, Fig. 3 is a partially sectioned side view of the filter element according to the invention, Fig. 4 is a highly simplified sectional view of a filter material, Fig. 5 is a sectional view as in Fig. 4 , but with a different design of the filter material.

[0035] As in Fig. 1illustrated, a cylindrical and three-stage filter element 1 for filtering a fluid flow, in particular for filtering lubricating oil, has a cylindrical fine filter body 2, which forms a fine filter stage 2', a cylindrical main filter body 3, which forms a main filter stage 3', and a cylindrical protective filter body 4, which forms a protective filter stage 4'. The fine filter body 2 and the main filter body 3 axially follow one another and enclose a Fig. 3 shown cavity 5, so that the fine filter stage 2' and the main filter stage 3' are arranged fluidically parallel. The also only in Fig. 3 The protective filter body 4 shown is arranged in this cavity 5, so that the protective filter stage 4' is fluidically arranged downstream of the fine filter stage 2' and the main filter stage 3'. The protective filter body 4 is in Fig. 1 and 3arranged in the area of ​​the main filter body 3. It is also conceivable that the protective filter body 4 is arranged in the area of ​​the fine filter body 2.

[0036] In the preferred embodiment shown here, all three filter bodies—the fine filter body 2, the main filter body 3, and the protective filter body 4—are each designed as annular filter bodies, so that, during operation of a filter device equipped with the filter element 1, the fluid flow to be filtered flows radially through the respective annular filter body 2, 3, 4 in order to achieve the respective filtration task. Such radially flowable annular filter bodies are characterized by a relatively small space requirement with a relatively large flow cross-section and thus by a comparatively low backpressure.

[0037] The filter element 1 further comprises a first end plate 6, on which at least one bypass valve 7 is formed for bypassing the fine filter stage 2' and the main filter stage 3'. Fig. 1 to 3 The number of bypass valves shown is merely an example. It is conceivable that 6 fixing tabs 8 are formed on the first end plate.

[0038] As in the Fig. 1 and 3 As illustrated, the filter element 1 has an intermediate disc 9, through which the fine filter body 2 is axially connected to the main filter body 3. Radially projecting spacer elements 10 are formed on the intermediate disc 9, spaced apart from one another in the circumferential direction and distributed over the circumference of the intermediate disc 9. The number of Fig. 1 to 3The spacer elements 10 shown are to be understood merely as examples. It is conceivable that the spacer elements 10 are formed from axially and radially extending ribs 11. It does not depart from the scope of the present invention if the spacer elements 10 have a different geometric shape.

[0039] The fine filter body 2 can have a filter fineness of 3µm + / - 1µm, the main filter body 3 can have a filter fineness of 10µm + / - 3µm, and the protective filter body 4 can have a filter fineness of 50µm + / - 10µm. The fine filter body 2 can also be designed to absorb water and / or oil aging products from the fluid flow. This will be discussed further below in connection with the Fig. 4 and 5 explained in more detail.

[0040] The filter element 1 is arranged in a substantially cylindrical filter housing 12 such that an annular space 15 extending along a longitudinal center axis 14 of the filter housing 12 is formed between an inner wall 13 of the filter housing 12 and the filter element 1. The filter element 1 is supported radially on the filter housing 12 via the spacer elements 10 formed on the intermediate disk 9. The filter housing 12, the inner wall 13 and the annular space 15 are only Fig. 1 and 3 schematically illustrated.

[0041] According to the Fig. 1 and 3 The filter element 1 has a second end plate 17 in which a central outlet opening 18 is formed. The protective filter body 4 is arranged in the region of the second end plate 17 such that the fluid flow from the cavity 5 can only flow through the protective filter body 4 to the outlet opening 18.

[0042] As in Fig. 3As illustrated, the protective filter body 4 has an open end plate 19 and a closed end plate 20. The protective filter body 4 is radially and tightly supported on the fine filter body 2 or the main filter body 3 via its open end plate 19 in the region of the second end plate 17. It is further conceivable for the protective filter body 4 to have support elements 21 on its closed end plate 20 that project radially and are distributed in the circumferential direction and arranged at a distance from one another. The protective filter body 4 is radially supported on the fine filter body 2 or the main filter body 3 or the intermediate plate 9 via the support elements 21.

[0043] A filter device 16 with the filter housing 12 and with at least one filter element 1 of the type described above is preferably used in a wind turbine for filtering lubricating oil.

[0044] According to the Fig. 4 and 5the fine filter body 2 may comprise a filter material 22, of which Fig. 4 and 5 In each case, only a small part is shown as a sectional view. In the case of an annular fine filter body 2, the filter material 22 can also extend in a ring shape. Preferably, the filter material 22 is also folded so that it extends in a star shape within the annular fine filter body 2.

[0045] According to an advantageous embodiment, the fine filter body 22 can contain a superabsorbent 23 for absorbing water. Such a superabsorbent 23 is a plastic, typically a polymer 24, which is capable of absorbing several times its own weight in a polar liquid, i.e., in particular, water. Upon absorption of the liquid or water, the superabsorbent 23 swells and forms a hydrogel 25. In other words, the fine filter body 2 can contain a superabsorbent, i.e., water-absorbing polymer 24, which forms a hydrogel 25 upon absorption of water.

[0046] For this purpose, the fine filter body 2 can preferably have at least one water-absorbing layer 26 in the filter material 22, which contains the superabsorber 23 or the water-absorbing polymer 24. The water-absorbing layer 26 extends in particular in a ring shape and coaxially to the rest of the fine filter body 2. Advantageously, it can now be provided that the water-absorbing layer 26 comprises or is formed by a polyester fleece 27 that has two fleece layers 28, 29, between which the superabsorber 23 or the water-absorbing polymer 24 is arranged. The polyester fleece 27 can be laminated in order to fix the two layers 28, 29 to one another and thus to secure the superabsorber 23 or the water-absorbing polymer 24 between the layers 28, 29, i.e., in the polyester fleece 27.

[0047] Additionally or alternatively, it can now be provided that the fine filter body 2 has a filter layer arrangement 30 in the filter material 22 for adsorbing oil aging products. This filter layer arrangement has a plurality of filter layers 31, 32, 33 that have different filter finenesses and are arranged in the fine filter body 2 such that the filter fineness increases in the flow direction 34 of the fine filter body 2, indicated by arrows. As a result, the filtration effect increases in the flow direction 34 from filter layer 31, 32, 33 to filter layer 31, 32, 33. The filter layers 31, 32, 33 and thus the filter layer arrangement 30 extend in particular in an annular manner and coaxially with the rest of the fine filter body 2.

[0048] The filter layer arrangement 30 can expediently comprise at least two, three or more filter layers 31, 32, 33. In the example of Fig. 4Exactly three filter layers are provided in the filter layer arrangement 30, namely a coarse filter layer 31, a middle filter layer 32 and a fine filter layer 33, which are arranged in the flow direction 34 of the fine filter body 2 so that the coarse filter layer 31 is the first filter layer to be flowed through, then the middle filter layer 32 and finally the fine filter layer 33. Fig. 5In the embodiment shown, however, exactly two filter layers are arranged in the filter layer arrangement 30, namely a coarse filter layer 31 and a fine filter layer 33, which are arranged in the flow direction 34 of the fine filter body 2 such that the flow passes through the coarse filter layer 31 first and then the fine filter layer 33. As mentioned above, the file filter body 2 can have a filter fineness of 3 µm + / - 1 µm. With the progressive filtration effect presented here, this filter fineness of the multi-layer fine filter body 2 is ultimately defined by the layer with the lowest filter fineness. In this example, this means that the fine filter layer 33 has a filter fineness of 3 µm + / - 1 µm, while the middle filter layer 32 and the coarse filter layer 31 are coarser.For example, the middle filter layer 32 can have a filter fineness of 6 µm + / - 2 µm or more, and the coarse filter layer 31 can have a filter fineness of 9 µm + / - 3 µm or more. Advantageously, the respective filter layer 31, 32, 33 of the filter layer arrangement 30 can be formed from a glass fiber fabric or glass fiber fleece. The glass fiber fabrics or glass fiber fleeces used in the various filter layers 31, 32, 33 differ from one another in terms of their mesh widths, permeabilities, or pore sizes. Different fiber lengths and / or fiber thicknesses are also conceivable.

[0049] In the example of Fig. 4 the water-absorbing layer 26 is provided in addition to the filter layer arrangement 30. In Fig. 4The water-absorbing layer 26 is arranged upstream of the filter layer arrangement 30 with respect to the flow direction 34. This ensures that the superabsorbent 23 and, during operation, the hydrogel 25 are better retained in the filter material 22.

[0050] At the Fig. 5 In the embodiment shown, the superabsorbent 23 is integrated into the filter layer arrangement 30. For this purpose, the water-absorbing layer 26 is arranged between two of the filter layers 31, 32, 33 of the filter layer arrangement 30. In the example of Fig. 5 the water-absorbing layer 26 forms the middle layer between the coarse filter layer 31 and the fine filter layer 33. This gives the filter layer arrangement 30 an additional function, namely as a water absorber.

[0051] The fine filter body 2 thus has a filter material 22 which is constructed in multiple layers, so that it can have the above-mentioned water-absorbing layer 26 and / or the above-mentioned filter layer arrangement 30. In addition, further layers can be provided, such as one or more wire layers for stabilizing the filter material 22. In the example of the Fig. 4 and 5 The filter material 22 is stabilized and protected by an upstream wire mesh layer 35 and an downstream wire mesh layer 36. At least one additional, not shown, plastic fleece layer can be provided, for example, to protect the glass fiber layers.

Claims

1. Filter apparatus (16) for filtering lubricating oil, preferably in a wind turbine, with at least one filter element (1) for filtering lubricating oil, - wherein the filter apparatus (16) has at least one essentially cylindrical filter housing (12) in which the respective filter element (1) is arranged, - wherein an annular space (15) extending along a longitudinal central axis (14) of the filter housing (12) is formed between an inner wall (13) of the filter housing (12) and the filter element (1), - wherein the filter element (1) is formed cylindrical and in three stages, - wherein the filter element (1) has a cylindrical fine filter body (2) forming a fine filter stage (2'), a cylindrical main filter body (3) forming a main filter stage (3'), and a cylindrical protective filter body (4) forming a protective filter stage (4'), - wherein the fine filter body (2) and the main filter body (3) follow one another axially and enclose a cavity (5) of the filter element (1), such that the fine filter stage (2') and the main filter stage (3') are arranged fluidically parallel, - wherein the protective filter body (4) is arranged in this cavity (5), such that the protective filter stage (4') is fluidically arranged downstream of the fine filter stage (2') and the main filter stage (3'), - wherein the filter element (1) has a first end plate (6) on which at least one bypass valve (7) is formed for bypassing the fine filter stage (2') and the main filter stage (3'), - wherein the filter element (1) has an intermediate disc (9) which axially connects the fine filter body (2) to the main filter body (3), characterized in - that at least two radially projecting spacer elements (10) are formed on the intermediate disc (9), spaced apart from one another in the circumferential direction and distributed over the circumference of the intermediate disc (9), - that the spacer elements (10) are formed from axially and radially extending ribs (11), and - that the respective filter element (1) is supported radially on the filter housing (12) via the spacer elements (10).

2. Filter apparatus (16) according to claim 1, characterized in - that the fine filter body (2) is configured as an annular filter body, through which the fluid flow can flow radially, and / or - that the main filter body (3) is configured as an annular filter body, through which the fluid flow can flow radially, and / or - that the protective filter body (4) is configured as an annular filter body, through which the fluid flow can flow radially.

3. Filter apparatus (16) according to any one of the preceding claims, characterized in - that the fine filter body (2) is configured to absorb water and / or adsorb oil ageing products from the fluid flow, - wherein the fine filter body (2) preferably contains a superabsorbent (23) for absorbing water, and - wherein the fine filter body (2) preferably has at least one water-absorbing layer (26) containing the superabsorbent (23), and - wherein the water-absorbing layer (26) preferably comprises a polyester nonwoven fabric (27) having two nonwoven layers (28, 29) between which the superabsorbent (23) is arranged.

4. Filter apparatus (16) according to claim 3, characterized in that the fine filter body (2) for adsorbing oil ageing products has a filter layer arrangement (30) which has multiple filter layers (31, 32, 33) which have different filter finenesses and which are arranged in the fine filter body (2) such that the filter fineness increases in the flow direction (34) of the fine filter body (2).

5. Filter apparatus (16) according to claim 4, characterized in - that the filter layer arrangement (30) has at least two filter layers, namely a coarse filter layer (31) and a fine filter layer (33), which are arranged in the flow direction (34) of the fine filter body (2) such that the flow first passes through the coarse filter layer (31) and then the fine filter layer (33), or - that the filter layer arrangement (30) has at least three filter layers, namely a coarse filter layer (31), a middle filter layer (32) and a fine filter layer (33), which are arranged in the flow direction (34) of the fine filter body (2) such that the flow first passes through the coarse filter layer (31), then the middle filter layer (32) and finally the fine filter layer (33).

6. Filter apparatus (16) according to claim 4 or 5, characterized in that at least one filter layer (31, 32, 33) of the filter layer arrangement (30) is formed by a glass fiber fabric.

7. The filter apparatus (16) according to claim 3 and according to any one of claims 4 to 6, characterized in that at least one filter layer (31, 32, 33) of the filter layer arrangement (30) contains the superabsorbent (23) or is formed by a water-absorbing layer (26) containing the superabsorbent (23).

8. Filter apparatus (16) for filtering lubricating oil, preferably in a wind turbine, with at least one filter element for filtering lubricating oil, - wherein the filter apparatus (16) has at least one essentially cylindrical filter housing (12) in which the respective filter element (1) is arranged, - wherein an annular space (15) extending along a longitudinal central axis (14) of the filter housing (12) is formed between an inner wall (13) of the filter housing (12) and the filter element (1), - wherein the filter element (1) is formed cylindrical and in three stages, - wherein the filter element (1) has a cylindrical fine filter body (2) forming a fine filter stage (2'), a cylindrical main filter body (3) forming a main filter stage (3'), and a cylindrical protective filter body (4) forming a protective filter stage (4'), - wherein the fine filter body (2) and the main filter body (3) follow one another axially and enclose a cavity (5) of the filter element (1), such that the fine filter stage (2') and the main filter stage (3') are arranged fluidically parallel, - wherein the protective filter body (4) is arranged in this cavity (5), such that the protective filter stage (4') is fluidically arranged downstream of the fine filter stage (2') and the main filter stage (3'), - wherein the filter element (1) has a first end plate (6) on which at least one bypass valve (7) is formed for bypassing the fine filter stage (2') and the main filter stage (3'), - wherein the filter element (1) has an intermediate disc (9) which axially connects the fine filter body (2) to the main filter body (3), characterized in - that at least two radially projecting spacer elements (10) are formed on the intermediate disc (9), spaced apart from one another in the circumferential direction and distributed over the circumference of the intermediate disc (9), - that the spacer elements (10) are formed from axially and radially extending ribs (11), - that the respective filter element (1) is supported radially on the filter housing (12) via the spacer elements (10), and - that the fine filter body (2) is configured to absorb water and / or oil ageing products from the lubricating oil.

9. Filter apparatus (16) according to any one of the preceding claims, characterized in - that the fine filter body (2) has a filter fineness of 3 µm + / -1 µm, - that the main filter body (3) has a filter fineness of 10 µm + / - 3 µm, - that the protective filter body (4) has a filter fineness of 50 µm + / - 10 µm.

10. Filter apparatus (16) according to claim 8 or 9, characterized in - that the filter element (1) has a second end plate (17) which has a central outlet opening (18), - that the protective filter body (4) is arranged in the area of the second end plate (17) such that the fluid flow from the cavity (5) can only flow through the protective filter body (4) to the outlet opening (18).

11. Filter apparatus (16) according to claim 10, characterized in - that the protective filter body (4) has an open end plate (19) and a closed end plate (20), - that the protective filter body (4) is radially and tightly supported on the fine filter body (2) or on the main filter body (3) via its open end plate (19) in the area of the second end plate (17).

12. Filter apparatus (16) according to claim 11, characterized in that the protective filter body (4) has, on its closed end plate (20), radially projecting support elements (21) which are distributed in the circumferential direction and arranged at a distance from one another, by means of which the protective filter body (4) is radially supported on the fine filter body (2) or on the main filter body (3) or on the intermediate plate (9).