FILTER DEVICE

Abstract

Disclosed is a filter device comprising at least one filter element (3), through which a fluid to be purified can flow with a determinable fluid operating pressure and which can be accommodated in a housing (1), wherein the fluid pressure prevailing at the respective filter element (3) may exhibit general pressure increases or pressure peaks which are damaging to the respective filter element (3), in particular to the filter material (9) thereof, and which can be reduced and/or smoothened by means of a compensation device which acts directly upon the respective filter element (3) and which has at least one flexible compensation element (29) that enables the volume of the fluid chamber of the housing (1) to be increased in accordance with a pressure peak or pressure increase, characterised in that the flexible compensation element (29) is arranged between the outer side of the filter material (9) of the filter element (3) and the adjacent inner wall of the housing (1).

Description

The invention relates to a filter device having at least one filter element, through which a fluid that is to be cleaned can flow at a predefinable fluid operating pressure, and which can be accommodated in a housing, wherein the fluid pressure prevailing at the respective filter element may exhibit pressure peaks or general pressure increases, which are damaging to the respective filter element and in particular, to the filter material thereof, which pressure peaks and increases can be reduced and/or leveled out by means of a compensation device, which acts directly on the respective filter element, and which has at least one flexible compensation element making it possible to increase the volume of the fluid chamber of the housing in accordance with a pressure peak or pressure increase.

Filter devices having at least one filter element, which can be accommodated in a housing, through which filter element fluid can flow at a corresponding system pressure or fluid operating pressure, are commercially available and are widely used, for example in the case of hydraulic systems in system branches, through which hydraulic fluid flows. In order to achieve a pressure-stable design of the respective filter element, as a rule it is provided that a support tube, preferably made out of a plastic material, is provided, which, having been provided with perforations, provides the support for the inserted filter material against the predefined direction of flow of the fluid. In the case of a filter device known from DE 10 2008 004 344 A1, the filter material, as a pleated filter mat, is placed about a fluid-permeable support tube, and the respective filter element is provided with end caps.

In the operation of a filter device, in particular in hydraulic systems, depending on the application, greater pressure pulsations or pressure peaks may arise. As a result, the fluid pressure prevailing locally at the respective filter element may deviate from the predefined fluid operating pressure and in particular, may exceed that pressure such that this may result in damage to the filter element, in particular the inserted filter material. Pressure pulsations of this kind occur in particular in hydraulic systems having quick-closing valves or having piston pumps. When such pressure pulsations arise, the contaminate pick-up required of the respective filter element and the correspondingly adjusted filtration grade may, at times, be affected. Should this situation arise, this may lead to a deterioration of the filter material.

In order to counter this hazard, in the prior art, pressure fluctuations that arise are smoothed out by means of a flexible compensation device; cf. the document, US 2009/0218295 A1. In the case of this known solution, the flexibility of the compensation device makes it possible to modify the volume located inside a filter housing, which accommodates a respective filter element. Among other things, the known solution is not satisfactory insofar as the installation space needed for the compensation device inside the filter housing is comparatively larger, so that a compact design cannot be implemented.

Starting from this prior art, the object of the invention is to provide a filter device, which better meets the requirements placed thereon and, in particular, makes a compact design possible.

This object is achieved according to the invention by a filter device, which has the features of claim 1 in its entirety.

According to the characterizing part of claim 1, an essential special feature of the invention is that the flexible compensation element is disposed between the outside of the filter material of the filter element and the adjacent inner wall of the housing. In contrast to the above-mentioned, known solution, in which the output device is connected as an axial extension to the end of the filter element, the invention makes it possible to design the filter device of this kind in such a way that the overall length of the housing does not substantially exceed the overall length of the filter element.

A particularly compact design can be implemented when the flexible compensation element is formed by an at least partial casing of the outside of the filter element, which is located in the housing.

It is especially advantageous that such a casing may be formed by a body having a predefined compressibility, wherein this may preferably be a porous material having closed pores, for example a foam. In the case of an especially advantageous embodiment, a casing made out of foam rubber, preferably an ethylene propylene diene monomer rubber (EPDM), is provided. A casing of this kind provides a particularly beneficial balance between unloaded volume size and compressed volume size.

In the case of especially advantageous embodiments having a filter element, which has a filter material that encases a hollow-cylindrical, inner filter cavity, which material is enclosed at the end by an end cap that forms the inlet and the outlet of the fluid chamber, the configuration is advantageously such that the casing completely encompasses the filter element, leaving the end cap at least partially free. An optimal compensation effect can thereby be achieved with a minimum size limit on the additional installation space required for the compensation device.

It is particularly advantageous that the configuration may be such that the casing has the form of a circular-cylindrical bowl, the inside of which rests against a support tube, which, in turn, rests against the outside of the filter material of the relevant filter element as the outer support tube thereof. In the case of a pressure increase or pressure peak in the inner fluid chamber of the filter element, the volume of said chamber is increased by compressing the casing by means of pressure, which is applied to the outer support tube.

In especially advantageous embodiments, the configuration may be such that the outside of the bowl of the casing rests against the inside of the housing, which can, however, be removed from the housing together with the filter element as a unit, if a state arises in which there is an absence of fluid operating pressure. Because the bowl, together with the filter element, can be removed from the housing during a replacement procedure, there is an additional, significant advantage that the replacement of the filter can be done in a convenient, clean and environmentally friendly manner because, when the filter element is removed, residual fluid and deposits are removed with the bowl of the casing; as a result, neither the housing not the environment are placed at risk during the handling of used filter elements.

An additional, special advantage of the invention is that, in addition to damping pressure pulsations, the compensation device forms a freeze protection for the filter device. This is of significance when it comes to fluids in the form of substances that can freeze. This is true in the case of those systems used in automotive engineering that are referred to in technical terms as AdBlue systems, for example. In these systems, aqueous urea solutions are supplied to the flow of exhaust gas in measured amounts from a supply tank, via a feeding system for exhaust treatment in the case of combustion engines, wherein ammonia is obtained from the urea by means of hydrolysis. This ammonia acts as a selective reducing agent in the flow of exhaust gas. In order to optimize the efficiency of the reduction, the aqueous urea solution is supplied to the flow of exhaust gas in a measured dose by a pump, which is load-dependently controlled by a control device. In the case of a urea solution that is supplied by a piston pump, which, because of the system, is subject to pressure pulsations, on the one hand, the compensation device exerts a smoothing effect. On the other hand, as freeze protection, the compensation device prevents the walls of the filter device from bursting due to an increase in volume as a result of a freezing process and therefore, the conditional freezing of the urea solution, or in particular, prevents damage to or the deterioration of a respective filter element because the compensation device compensates for an increase in volume as a result of freezing.

Pursuant to claim 9, the subject matter of the invention is also a filter element, which in particular, is provided for use in a filter device according to one of the claims 1 through 8.

The invention is described in greater detail below on the basis of an embodiment, which is depicted in the drawings. Shown are:

FIG. 1 an oblique view in perspective of an embodiment of the filter device according to the invention, viewed from the end cap of an associated filter element;

FIG. 2 an oblique view, in perspective, of only the filter element of the embodiment, again viewed from the end cap thereof, and having a partial cutaway of the casing so that a part of the outside of the filter material of the filter element is visible;

FIG. 3 a longitudinal section of the filter element shown in FIG. 2;

FIG. 4 a longitudinal section of the embodiment of the filter device, wherein the filter element from FIGS. 2 and 3 has been accommodated in the associated filter housing; and

FIG. 5 a partial longitudinal section of only the region of the filter element that is adjacent to the end cap, which has been enlarged as compared to FIG. 3.

The embodiment of the filter device according to the invention shown as a whole in FIGS. 1 and 4, and shown in a sectional view in the case of the latter Figure, has a filter housing 1, which is provided in order to accommodate the filter element 3, which is shown separately in FIGS. 2 and 3, and shown in a sectional view in the case of the latter Figure. The filter housing 1, which is made out of a plastic or a metal material, has the shape of a hollow cylinder, which is closed at the bottom 5, and which is open at the opposite, upper end 7. The filter element 3, which can be inserted into the filter housing from the open end 7, which filter element is formed in the manner of a so-called filter cartridge, has a filter material 9 in the form of a pleated filter mat, which, in the manner that is customary for such filter cartridges, encloses a fluid-permeable support tube 11, preferably made out of plastic, within which an inner filter cavity 13 is located. A second, external, fluid-permeable support tube 15 is located on the outside of the filter material 9. The filter material 9 is enclosed at the lower end in the drawing by a closed end cap 17. Located at the other end of the filter material 9 is an end cap 19, at which a connection is made to an associated filter head, which is not shown, and by means of which a fluid that is to be cleaned is supplied, and the cleaned fluid is discharged. The end cap 19, which, like the closed end cap 17, is made as a single piece out of a plastic material using injection molding, has a connection fitting 21 for a fluid connection to the inner filter cavity 13, at which fitting, an O-ring 23 is located in order to form a seal at the filter head.

As can most clearly be seen in FIGS. 1 and 2, the end cap 19 does not have a completely circular profile but rather, has recesses, which extend inward in a radial direction. As a result, annular gaps 25 are formed on the circumference of the end cap 19 between the end cap 19 and the edge 27 of a casing, which encloses the end cap 19. This casing has the form of a bowl 29, which extends from the open edge 27 thereof, to a closed bottom part 31, forming a circular cylinder. In the functional position, in which the bowl 29 is accommodated in the filter housing 1, the bottom part 31 of the bowl 29 is located at the bottom 5 of the housing 1; see FIG. 4. Like the connection fitting 21, the gaps 25 form the fluid connection from the filter head, which is not shown, to the inner fluid chamber of the filter element 3, wherein the direction of flow in the case of a filtering process may be provided in such a way that the fluid that is to be cleaned flows in via the connection fitting 25, is distributed along the support tube 15 and, after passing through the filter material 9, is discharged via the connection fitting 21 of the end cap 19.

The bowl 29, which is closed at the bottom part 31, and which forms a casing that completely encloses the filter element 3 up to the upper end cap 19, is made out of a compressible material. In the functional position, wherein the filter element 3 is accommodated in the housing 1, see FIG. 4, in such a way that the smooth outer surface of the bowl 29 that forms the casing rests against the likewise smooth inner wall of the housing 1, the bowl 29 forms an effective compensation device due to the flexibility thereof, in that there is an increase in the volume of the fluid chamber in the filter element 3 as a result of a pressure-dependent compression of the material of the bowl 29, which compensates for pressure increases or smooths out pressure peaks. Materials that are preferably porous, compressible materials having closed pores, are considered as a material for the bowl 29, which is suitable for pressing against the inner wall of the housing 1. In the case of the present embodiment, the bowl 29, which serves as a casing, is formed out of a foam rubber, preferably an ethylene propylene diene monomer rubber (EPDM). As shown in FIGS. 3 and 4, the bowl 29 is a single-piece component having a protuberance 33 that extends axially inward from the bottom part 31 as a centering piece for the closed lower end cap 17. A stabilizing element 35 extends from that lower cap into the inner filter cavity 13.

As already mentioned, the outside of the bowl 29, which forms the casing, and the inner wall of the filter housing 1 are smooth. The dimensioning of the filter element 3 and housing 1 is such that the filter element 3 can be inserted into the housing 1 from the open end 7 of said housing. In order to allow easy insertion and removal, three recessed, longitudinal grooves 29, which are offset to one another at intervals of 120°, are formed in the outside of the bowl 29 as an interruption to the otherwise smooth outer surface, of which grooves only one is visible in FIG. 2. These longitudinal grooves 39 permit a corresponding pressure equalization when the filter element 3 is inserted into the housing 1 and when the filter element 3 is removed from the housing 1 when the filter element is exchanged. Thanks to the casing, which is formed by a bowl 29 that is closed at the bottom part 31 thereof, residual fluids and deposited materials remain within the bowl 29 when a filter element 3 that is to be exchanged is removed, said bowl thereby serving as a container for contaminated media. Contamination of the housing during changing processes is thereby avoided. The operating fluids coming into contact with the wall of the housing 1 during the filtering process is also prevented by the fact that the bowl 29 is pressed against the inner wall of the housing 1 by the system pressure that prevails there during the filtration process.

Claims

1. A filter device having at least one filter element (3), through which a fluid that is to be cleaned can flow at a predefinable fluid operating pressure, and which can be accommodated in a housing (1), wherein the fluid pressure prevailing at the respective filter element (3) may exhibit pressure peaks or general pressure increases, which are damaging to the respective filter element (3), and in particular to the filter material thereof (9), which pressure peaks and increases can be reduced and/or leveled out by means of a compensation device, which acts directly on the respective filter element (3), and which has at least one flexible compensation element (29), which makes it possible to increase the volume of the fluid chamber of the housing (1) in accordance with a pressure peak or pressure increase, characterized in that the flexible compensation element (29) is disposed between the outside of the filter material (9) of the filter element (3) and the adjacent inner wall of the housing (1).

2. The filter device according to claim 1, characterized in that the flexible compensation element is formed by an at least partial casing (29) of the outside of the respective filter element (3) located in the housing (1).

3. The filter device according to claim 2, characterized in that a casing (29) is formed by a body having a predefined compressibility.

4. The filter device according to claim 1, characterized in that a casing (29) made out of a porous material having closed pores, such as a foam, is provided.

5. The filter device according to claim 1, characterized in that a casing (29) made out of foam rubber, preferably an ethylene propylene diene monomer rubber (EPDM), is provided.

6. The filter device according to claim 1, characterized in that a filter element (3) is provided with a filter material (9) that encases a hollow-cylindrical, inner filter cavity, which material is enclosed at the end by an end cap (19) that forms the inlet (25) and the outlet (21) of the fluid chamber, and in that the casing (29) completely encompasses the filter element (3), leaving the end cap (19) at least partially free.

7. The filter device according to claim 1, characterized in that the casing has the form of a circular-cylindrical bowl (29), the inside of which rests against a support tube (15), which, in turn, rests against the outside of the filter material (9) of the relevant filter element (3) as the outer support tube (15) thereof.

8. The filter device according to claim 1, characterized in that the outside of the bowl (29) of the casing rests against the inside of the housing (1), which can, however, be removed from the housing (1) together with the filter element (3) as a unit, if a state arises in which there is an absence of fluid operating pressure.

9. A filter element, in particular for use in a filter device according to claim 1, having a casing (29) made out of a compressible material, which at least partially encompasses the outside of the associated filter element (3).

10. The filter element according to claim 9, characterized in that a casing (29) made out of a porous material having closed pores such as a foam, preferably foam rubber, is provided.

11. The filter element according to claim 9, characterized in that said element has a filter material, which encases a hollow-cylindrical, inner filter cavity (13), which material is enclosed at the end by an end cap (19) that forms the inlet (25) and the outlet (21) of the fluid chamber, and in that the casing (29) completely encompasses the filter element (3), leaving the end cap (19) at least partially free.