FILTER DEVICE

Description

[0001] The invention relates to a filter element having the features in the preamble of claim 1. The invention further relates to a filter device having such a filter element.

[0002] In many fluid systems in which filter devices are used, the fluid in question, such as a fuel, a lubricant, or an operating fluid for an application system, is subjected to intermittent pressure loading. The occurrence of undesirable pressure pulsations can lead to material fatigue in system components as a result of the pulsation load. This can also impair the dosing accuracy when dosing a fluid in question with a dosing valve, combined with a deterioration in the spray quality of the fluid being dosed. To counteract this, it is state of the art to provide a pulsation-damping compensator device for filter devices used in fluid systems subject to pressure pulsations.

[0003] DE 10 2012 223 028 A1 discloses a filter device of the aforementioned type, which is intended for use in an aftertreatment device for exhaust gases from an internal combustion engine. In such a device, in which an aqueous urea solution, such as that available under the brand name AdBlue®, is injected into the exhaust stream in metered amounts to reduce nitrogen oxides contained in the exhaust gas to nitrogen and water, pressure pulsations are particularly disruptive. The solution known from the aforementioned document provides a closed protective sheath made of an elastomer as a compensation element, which can be deformed against the force of a spring arrangement to smooth out pressure fluctuations.With the flexibility provided by the spring arrangement, the sleeve also acts as a compensator to reduce the ice pressure that builds up in the event of the aqueous urea solution freezing in the filter device and leads to damage to the filter element due to excessive pressure load.

[0004] EP 0 881 396 A2 describes a filter element which has an element material extending between two cap parts, which is supported on the inner circumference against a fluid-permeable support device, wherein a compensator device is arranged in the interior of the support device.

[0005] Further filter elements are disclosed in EP 2 441 968 A1, EP 1 041 327 A2, US 6 213 153 B1, EP 1 222 402 A0 or WO 01 / 29431 A1 and US 2018 / 0195475 A1.

[0006] Based on this prior art, the invention aims to provide a filter element and a filter device of the type in question which are characterized by particularly reliable operating behavior while having a particularly simple structure.

[0007] According to the invention, this object is achieved by a filter element which has the features of patent claim 1 in its entirety.

[0008] According to the characterizing part of claim 1, an essential feature of the invention is that a cap part is an integral component of the compensator device.

[0009] In a preferred embodiment, the filter element is surrounded on its outer circumference by a jacket at a predeterminable radial distance, forming a fluid chamber. This jacket, in turn, is surrounded by the filter housing at a predeterminable radial distance, forming a further fluid chamber. The two fluid chambers are fluid-conductingly connected to one another in the form of communicating tubes. This design of an inner jacket surrounding the filter element leads to a significant reduction in the freezing pressure acting on the filter element in the event of freezing.When the fluid spaces are arranged like communicating tubes, with the fluid spaces only being connected to one another at one end of the inner shell, in the event of freezing only the freezing pressure of the fluid volume in the inner fluid space has a damaging effect on the filter element, while the freezing pressure of the fluid volume in the outer fluid space is only effective between the outer shell and the inner wall of the filter housing. With a structurally small volume of the inner fluid space, freezing damage can therefore be largely avoided. A further advantage of the inner shell is the formation of an onflow guard for the filter element, because when the unfiltered fluid flows into the outer fluid space, the outer side of the shell forms an impact surface for the unfiltered flow.

[0010] Advantageously, the arrangement is such that the communicating tubes are arranged coaxially to the longitudinal axis of the filter element and have a cylindrical structure.

[0011] In advantageous embodiments, the filter element has the element material extending between two cap parts, the unfiltrate or inflow side of which opens into one fluid space and the filtrate or outflow side of which points in the direction of the compensator device.

[0012] The element material is designed as a hollow cylinder with a plurality of filter fibers and is at least partially air-impermeable, preferably substantially air-impermeable and particularly preferably completely air-impermeable.

[0013] With particular advantage, the arrangement can be such that one, in particular the upper cap part is an integral component of the casing and that the other, in particular the lower or base-side cap part is an integral component of the compensator device.

[0014] In order to establish the fluid-carrying connection between the two communicating tubes, in advantageous embodiments the casing has at least one fluid passage point in its base-side region.

[0015] For effective protection of the element material against flow forces, a support device is arranged between the filter element and the compensator device, against which the element material is supported when fluid flows through it from the outside to the inside.

[0016] To ensure fluid-tight closure of one fluid chamber of the communicating tubes, which is located on the outside of the casing, the two cap parts are sealed against the filter housing by means of a sealing device.

[0017] With regard to the design of the compensator device, the arrangement is advantageously such that the compensator device has a thin-walled hollow body, preferably made of a plastic material. The thin wall of the hollow body forms a type of membrane that is reversibly deformable to dampen pulsations.

[0018] Advantageously, the arrangement can be such that the upper cap part of the filter element is penetrated at the end by the hollow body, forming at least one further fluid passage point, which protrudes axially beyond the upper cap part with a predeterminable projection and is fixed in its installation position by the upper cap part in this area.

[0019] The fluid-permeable support device can advantageously be formed from a support tube which extends between the two cap parts and radially surrounds the hollow body.

[0020] In a particularly advantageous embodiment, the filter housing has an inlet for unfiltered material, in particular in the form of a particle-contaminated urea-hydrogen solution, which, after being cleaned of particles from the element material in a fluid direction from the outside to the inside, can be discharged from the filter housing via an outlet. Air supplied in the opposite direction via the outlet blows out the unfiltered material remaining in the filter housing at least partially toward the inlet of the filter housing, bypassing the element material. Due to the extensive emptying of the filter housing thus enabled when the filter is shut down, the filter device according to the invention is particularly effectively protected against damage caused by freezing pressure.

[0021] For particularly reliable emptying, the arrangement can advantageously be such that the upper cap part is provided with an additional element material that filters out particles from an air stream and is connected on its clean side to the fluid space between the casing and the one element material. This prevents the risk of contaminants being introduced via the air stream used for blowing out. A hydrophobic element material can advantageously be provided here, which prevents the transfer of unfiltered material during normal filtration operation.

[0022] The invention is explained in detail below using an embodiment shown in the drawing.

[0023] In the single figure, the filter element of the embodiment of the filter device is shown in longitudinal section and the associated filter housing is shown in a schematically simplified longitudinal section.

[0024] The filter housing 2 has a circular-cylindrical main part 4 and an adjoining upper head part 6. On the main part 4, near the transition to the head part 6, there is a lateral inlet 8 through which, as indicated by a flow arrow 10, unfiltered material can flow into the circular-cylindrical interior 12 of the main part 4. On the head part 6, an outlet 14 is also located laterally, through which, during operation, filtrate flows out, as indicated by flow arrow 16. In the simplified representation of the head part 6, the fluid connection between outlet 14 and the main part 4 is not shown in detail.

[0025] The filter element 18 accommodated in the circular-cylindrical interior 12 of the main part 4 comprises an element material 20 in the form of a circular-cylindrical hollow body, which is accommodated between an upper cap part 22 facing the head part 6 and a lower cap part 24. The upper cap part 22 has an annular groove 26 on its outer circumference, in which an O-ring 28 is seated, which seals the cap part 22 against the main housing part 4. Similarly, an annular groove 30 is formed on the lower cap part 24 for an O-ring 32, which seals the lower cap part 24 against the main housing part 4.To secure the filter element 18 in the installation position shown in the figure, the lower cap part 24, which is injection-molded in one piece from a plastic material, has, adjacent to an annular surface 34 that forms the contact surface for the front end of the hollow body of the element material 20, a downwardly projecting projection 36 in the shape of a hollow cylinder that is coaxial with the longitudinal axis of the housing and is connected via a steep thread 38 to a cover 40 that forms the bottom end of the main housing part 4 and can be secured thereto by means of a screw connection 42. The annular surface 34 of the cap part 24 is delimited radially inwardly by a nozzle 46 that is concentric with the longitudinal axis 44 of the housing and merges into an upwardly adjoining hollow body 48. This hollow body 48 has a thin-walled design so that it forms a flexible membrane.With its upper, closed end region, the hollow body 48 extends through a central opening 50 in the upper cap part 22, with the upper end 52 of the hollow body 48 projecting upward beyond the opening 50 in the region of a trough-like depression 54 in the cap part 22. The opening 50 has individual radially inwardly projecting projections 56 on the inside. During filtration operation, in which the element material 20 of the filter element 18 is flowed through from the outside to the inside, passage points are therefore formed between the opening 50 and the membrane of the hollow body 48, through which passage points, as indicated by flow arrows 58, filtrate reaches the head part 6 and the filtrate outlet 14. During flow from the outside to the inside, the element material is supported by a fluid-permeable support tube 60 that surrounds the hollow body 48.

[0026] The upper cap part 22 has a one-piece molded shell 62, which, with the exception of a thickened shell portion 64, has the shape of a circular cylindrical hollow body. The outer and inner diameters of the shell 62 are dimensioned such that a first fluid chamber 66 is formed between the outer side of the element material 20 and the inner side of the shell 62, and a second, outer fluid chamber 68 is formed between the outer side of the shell 62 and the main housing part 4. To form a fluid-conducting connection between the fluid chambers 66 and 68, wall openings 70 are formed in the shell 62 in the base-side end region of the shell 62.

[0027] With this arrangement and fluid connection, the two fluid chambers 66, 68 form a type of communicating tube which, with the exception of the thickened shell portion 64 with which the shell 62 rests against the housing interior, has a cylindrical structure coaxial with the longitudinal axis 44. During operation, with the unfiltered material flowing into the outer fluid chamber 68 via the inlet 8, the shell 62 forms the inflow surface, so that the outer side of the element material 20 is not exposed to any radially acting flow pressure load in the event of pressure pulsations, but rather the unfiltered material flows in the axial direction in the inner fluid chamber 66, as indicated by flow arrow 72. With its thin, membrane-like wall, the hollow body 48 forms a compensator device that smooths out the pulsations. For this purpose, the interior of the hollow body 48, closed off by the base cover 40, can contain a compressible medium, such as air or N 2 .To adjust the desired damping characteristics, the interior can be pressureless or filled with, for example, a low level of pressure.

[0028] Thanks to the special design of the fluid spaces 66, 68, the device according to the invention is largely freeze-proof, since only a small volume of fluid, which acts on the element material 20 under freezing pressure when frozen, is enclosed in the fluid space 66, while any freezing pressure developing in the outer fluid space 68 is absorbed by the jacket 62. For additional freeze protection, the device according to the invention offers the possibility of blowing out the unfiltered material located in the fluid spaces 66, 68 via the fluid inlet 8 when the device is shut down. For this purpose, a passage 76 is formed in a wall section 74 of the trough-like depression 54 of the upper cap part 22, which passage leads from the upper side of the cap part 22, forming the filtrate side, to the fluid space 66.Located in passage 76 is a particle filter 78 whose filter material is hydrophobic, so that no passage of unfiltered material from the fluid chamber 66 via passage 76 is possible, but the flow of blown air from the filtrate side via outlet 76 is possible. When the device is shut down, both the fluid volume in the first fluid chamber 66 and the second fluid chamber 68 can be blown out via the unfiltered material inlet 8 by supplying compressed air from the filtrate outlet 14. The device, which is thus practically completely emptied, is thus particularly reliably protected against freezing damage. In order to largely avoid a side flow of blown air during blowing out, the element material 20 of the filter element 18 is preferably provided with a fiber material that is essentially impermeable to air.

Claims

1. Filter element which has an element material (20), which extends between two cap parts (22, 24), and is supported on the inner circumference by a fluid-permeable supporting device (60), wherein a compensator device (48) is arranged in the interior of the supporting device (60), characterised in that one cap part (24) is an integral component of the compensator device (48).

2. Filter element according to claim 1, characterised in that the element material (20) which is surrounded on the outer circumference by a casing (62) and is formed from a hollow cylinder, in that the one cap part (22) is an integral component of the casing (62) and the other cap part (24) is an integral component of the compensator device (48), which engages through the supporting device with a thin-walled hollow body in the form of a supporting tube (60) and engages through the upper cap part with its free end (52), forming at least one further fluid passage point (50, 56).

3. Filter device, having a filter element (18) according to claim 1 or 2, which is accommodated in a filter housing, and in the interior of which filter element a compensator device (48) is accommodated, characterised in that the filter element (18) is surrounded on the outer circumference and at a predefinable radial distance, forming a fluid chamber (66), by the casing (62), which in turn is surrounded at a predefinable radial distance, forming a further fluid chamber (68), by the filter housing (2), and in that the two fluid chambers (66, 68) are connected to each other in a fluid-conducting manner in the form of communicating tubes.

4. Filter device according to claim 3, characterised in that the communicating tubes (66, 68) are arranged coaxial with the longitudinal axis (44) of the filter element (18) and have a cylindrical structure.

5. Filter device according to claim 3 or 4, characterised in that the filter element (18) has the element material (20) extending between two cap parts (22, 24), the unfiltered medium or incident flow side of which opens into the one fluid chamber (66) and the filtrate or outflow side of which is directed towards the compensator device (48).

6. Filter device according to one of claims 3 to 5, characterised in that the element material (20) is configured as a hollow cylinder with a plurality of filter fibres and is at least partially impermeable to air, preferably substantially impermeable to air, particularly preferably completely impermeable to air.

7. Filter device according to one of claims 3 to 6, characterised in that the one, in particular the upper cap part (22) is an integral component of the casing (62).

8. Filter device according to one of claims 3 to 7, characterised in that, to establish the fluid-conducting connection between the two communicating tubes (66, 68), the casing (62) has at least one fluid passage point (70) in its base region.

9. Filter device according to one of claims 3 to 8, characterised in that the element material (20) is supported on the supporting device (60) when the fluid flows through said element material from outside to inside.

10. Filter device according to one of claims 3 to 9, characterised in that the two cap parts (22, 24) are sealed with respect to the filter housing (2) by means of a sealing device (28).

11. Filter device according to one of claims 3 to 10, characterised in that the compensator device has a thin-walled hollow body (48) which is preferably formed from a plastic material.

12. Filter device according to one of claims 3 to 11, characterised in that the upper cap part (22) of the filter element (18) is penetrated at the end by the hollow body (48), which protrudes axially beyond the upper cap part (22) with a predefinable overhang and is fixed in its installation position by the upper cap part (22) in this region, forming at least one further fluid passage point (50).

13. Filter device according to one of claims 3 to 12, characterised in that the fluid-permeable supporting device is formed from a supporting tube (60), which extends between the two cap parts (22, 24) and surrounds the hollow body (48) radially.

14. Filter device according to one of claims 3 to 13, characterised in that the filter housing (2) has an inlet (8) for unfiltered medium, in particular in the form of a particle-contaminated urea-water solution, which, cleaned of the particles by the element material (20) in a fluid direction from outside to inside, can be discharged from the filter housing (2) via an outlet (14), and in that air supplied in the opposite direction via the outlet (14) blows out the unfiltered medium remaining in the filter housing (2) at least partially towards the inlet (8) of the filter housing (2) while bypassing the element material (20).

15. Filter device according to one of claims 3 to 14, characterised in that the upper cap part (22) is provided with a further element material (78), which filters particles out of an air flow, and is connected on its clean side to the fluid chamber (66) between the casing (62) and the one element material (20).