EP3280510A1

EP3280510A1 - Filter device

Info

Publication number: EP3280510A1
Application number: EP15715721.5A
Authority: EP
Inventors: Tobias Wendel; Valentin Pichlmaier; Klaus Mössinger
Original assignee: FSP Fluid Systems Partners Holding AG
Current assignee: Argo Hytos Group AG
Priority date: 2015-04-09
Filing date: 2015-04-09
Publication date: 2018-02-14
Also published as: CN107427748A; WO2016162073A1; US20180126307A1

Abstract

The invention relates to a filter device for filtering a hydraulic liquid, comprising a housing (12), which has a housing upper part (14) and a housing lower part (16) that can be detachably connected to the housing upper part, wherein the housing upper part (14) has a housing inlet (34) and a housing outlet (38) and a filter element (88) is arranged in the housing lower part (16), the unfiltered side (118) of which filter element has a flow connection to the housing inlet (34) and the filtered side (120) of which filter element has a flow connection to the housing outlet (38). According to the invention, in order to develop the filter device in such a way that the filter device can be produced more economically, the housing upper part (14) has an inner wall (48) that is convexly curved outward along the entire periphery of the housing upper part and an insertable flow-guiding element (70) is arranged in the housing upper part (14), which flow-guiding element divides the interior of the housing upper part (14) into an unfiltered region (112) and a filtered region (114), wherein the unfiltered region (112) has a flow connection to the unfiltered side (118) of the filter element (88) and the housing inlet (34) leads into the unfiltered region (112), and wherein the filtered region (114) has a flow connection to the filtered side (120) of the filter element (88) and the housing outlet (38) leads out of the filtered region (114).

Description

FILTER DEVICE

The invention relates to a filter device for filtering a hydraulic fluid having a housing which has an upper housing part and a lower housing part detachably connectable to the upper housing part, wherein the upper housing part has a housing inlet for hydraulic fluid to be filtered and a housing outlet for filtered hydraulic fluid and a filter element is arranged in the lower housing part, the side of which is in flow connection with the housing inlet and whose clean side is in flow connection with the housing outlet.

Such filter devices are used in hydraulic systems, for example in self-propelled machines, especially construction machinery and agricultural machinery. By means of such filter devices can

Hydraulic fluids, such as mineral oils, are filtered. For this purpose, a filter element is used, to which the hydraulic fluid to be filtered can be supplied from a housing inlet of the filter device and from which the filtered fluid can be supplied to a housing outlet of the filter device. The housing comprises an upper housing part and a detachably connectable with this housing lower part. It can be provided, for example, that the lower housing part can be screwed to the upper housing part. The upper housing part has the housing inlet and the housing outlet, to each of which a hydraulic line can be connected. In the lower housing part is the filter element, which can be replaced if necessary, by the lower housing part is separated from the upper housing part.

The supply of hydraulic fluid to the raw side of the filter element as well as the removal of filtered liquid from the clean side of the filter element to the housing outlet is often characterized in that in the upper housing part Strö- mungskanäle are provided. The upper housing part is this made in many cases by machining or in the form of a casting. Since the hydraulic fluid can be under a high pressure, for example a pressure of several 100 bar, in particular 400 to 500 bar, the upper housing part as well as the lower housing part on a considerable material thickness to ensure the necessary mechanical stability.

A filter device of the aforementioned type is known from DE 1 436 277 AI.

Object of the present invention is to develop a filter device of the type mentioned in such a way that it can be produced more cheaply.

This object is achieved in a filter device of the generic type according to the invention that the upper housing part has along its entire circumference convexly outwardly curved inner wall, and that in the upper housing part an insertable flow guide is arranged, which divides the interior of the upper housing part into a raw area and a clean area , wherein the raw area is in flow communication with the raw side of the filter element and the housing inlet opens into the raw area, and wherein the clean area is in fluid communication with the clean side of the filter element and the housing outlet leads out of the clean area.

In the filter device according to the invention, an upper housing part is used, the inner wall is convexly curved along its entire circumference outwards. The inner wall thus has an oval, in particular elliptical, or else a circular shape with respect to a plan view. This makes it possible to produce the upper housing part with relatively low material thickness and still give the upper housing part a high compressive rigidity. The inner wall of the upper housing part has virtually no jump along its circumference about the longitudinal axis of the housing Changes in shape on which at a pressure load of several 100 bar, especially at a pressure load of 400 to 500 bar, mechanical stress peaks could arise. The material thickness of the upper housing part can thus be chosen relatively small and the upper housing part can be produced inexpensively, without a machining is required.

The lower housing part of the filter device according to the invention is preferably cylindrical, so that the inner wall of the housing lower part is convexly curved along its entire circumference and consequently also the lower housing part has a high compressive rigidity with a relatively small material thickness.

In order to be able to feed the hydraulic fluid to be filtered to the raw side of the filter element and to be able to remove the filtered fluid from the clean side of the filter element, a flow guiding element is used in the filter device according to the invention, which can be inserted into the upper housing part. The flow guide divides the upper housing part into a raw area and a clean area. The housing inlet opens into the raw area and the raw side of the filter element is in flow communication with the raw area, so that the hydraulic fluid to be filtered can be supplied to the filter element via the raw area. The clean area is in fluid communication with the clean side of the filter element and the housing outlet leads out of the clean area so that the filtered hydraulic fluid can be supplied to the housing outlet via the clean area. It is therefore not necessary to mold additional flow channels in the upper housing part.

The flow guide can be inexpensively made of a plastic material, since it is essentially subject only to the pressure load resulting from the pressure difference, which adjusts itself to the filter element. As it flows through the filter element, the hydraulic fluid experiences a pressure drop of a few bar, for example 3 to 5 bar. As a consequence, that the pressure of the hydraulic fluid in the raw area of the housing is only a few bar different from the pressure of the hydraulic fluid in the clean area and the flow guide used in the upper housing part only has to withstand this relatively small pressure difference. While the upper housing part as well as the lower housing part is conveniently made of metal in uses of the filter device in the high pressure area, especially in uses in the range of 400 to 500 bar, the flow guide can be inexpensively made of a plastic material.

The inner wall of the upper housing part, it has already been pointed out, has a circular or oval shape in the filter device according to the invention. It is particularly advantageous if the inner wall of the housing upper part is designed to be circular or elliptical in a plane oriented perpendicular to a longitudinal axis of the housing. The longitudinal axis of the housing is conveniently aligned or parallel to the longitudinal axis of the filter element and extends from a top wall of the upper housing part to a bottom wall of the lower housing part.

In an advantageous embodiment of the invention, the inner wall of the housing upper part with respect to the longitudinal axis of the housing at the level of the housing inlet and the housing outlet on an elliptical inner wall portion, and in an end portion of the housing upper part facing the housing lower part, the inner wall has a circular inner wall portion. The provision of an elliptical inner wall section at the level of the housing inlet and the housing outlet has the advantage that the material thickness of the housing upper part in the region of the housing inlet and the housing outlet can be made larger than in the peripheral region between the housing inlet and the housing outlet, and the provision of a circular inner wall section in FIG the

Housing bottom end portion has the advantage that the inner wall in this end can carry an internal thread into which the housing seunterteil can be screwed with a complementary configured external thread.

It is particularly advantageous if the radius of the circular inner wall section is greater than the large semiaxis of the elliptical inner wall section. With such a configuration, the interior of the housing upper part thus widens in the direction of the housing lower part. This facilitates the provision of an internal thread in the adjoining the lower housing part region of the housing upper part, without thereby affecting the flow connection between the housing inlet and the raw side of the filter element or the flow connection between the clean side of the filter element and the housing outlet.

In an advantageous embodiment of the invention, the outer wall of the upper housing part in the circumferential direction between the housing inlet and the housing outlet on the outside convex curved outer wall sections. By the convex outwardly curved shape of the outer wall in the

Peripheral area between the housing inlet and the housing outlet is the housing upper part imparted a particularly high compressive stiffness, the material thickness of the upper housing part can be kept relatively low.

In the region of the housing inlet and / or in the region of the housing outlet, the outer wall can be designed to simplify the production of a connection between the housing inlet and the housing outlet and a hydraulic line. The flat areas of the housing outer wall may extend in the longitudinal direction of the housing upper part from the top to the bottom thereof.

It is favorable if the outer wall of the housing upper part has circular-arc-shaped or elliptical-arc-shaped outer wall sections in the circumferential direction between the housing inlet and the housing outlet. It can be provided, for example, that the outer wall of the housing upper part is formed in the peripheral region between the housing inlet and the housing outlet circular arc-shaped, and that the inner wall of the housing upper part is designed elliptical. Alternatively it can be provided that the outer wall in the peripheral region between the housing inlet and the housing outlet is designed elliptical arc-shaped and the inner wall of the upper housing part is designed circular. In addition, it can be provided that the outer wall in the peripheral region between the housing inlet and the housing outlet is designed elliptical arc-shaped and that also the inner wall of the housing upper part is designed elliptical, wherein the eccentricities of the inner wall and the outer wall are advantageously different. The combination of a circular shape and an ellipse, as well as the combination of two ellipses with different eccentricity has the advantage that a greater material thickness can be selected for the upper housing part in the region of the housing inlet and the housing outlet than in the peripheral regions between the housing inlet and the housing outlet Different thicknesses of material do not cause any jumps in rigidity at which stress peaks which impair mechanical stability can arise when the upper part of the housing is subjected to a high pressure load.

The provision of a greater material thickness in the region of the housing inlet and the housing outlet than in the region between the housing inlet and the housing outlet has the advantage that the housing inlet as well as the housing outlet may have an internal thread with a plurality of thread turns, so that in the housing inlet and in the housing outlet in each case a connection element with a complementarily configured external thread can be screwed, wherein the screw also withstands very high pressure loads. In the peripheral region between the housing inlet and the housing outlet, however, the material thickness can be selected to be lower. As already mentioned, it is advantageous if regions of different material thickness of the upper housing part continuously merge into one another, because even with a high pressure load on the upper housing part, its pressure rigidity-impairing stress peaks can be avoided.

The housing outlet is conveniently diametrically opposite the housing inlet.

It is particularly advantageous if the housing outlet is arranged at the same height with respect to the longitudinal axis of the housing as the housing inlet.

The upper housing part is produced in an advantageous embodiment of the invention by cold forming or by hot forming. It can be provided, for example, that the upper housing part is designed as a steel extruded part or as a forged part.

For the design of the flow guide so far no further details have been made. In an advantageous embodiment of the invention, the flow guide on a cutting disc with a sealing element which is sealingly applied to the inner wall of the upper housing part. By means of the sealing element, the raw area can be reliably separated from the clean area, so that it is ensured that hydraulic fluid to be filtered can not reach the clean area directly from the raw area without first passing through the filter element.

The arranged on the blade sealing element is preferably formed as formed on the cutting disc sealing lip. The embodiment in the form of a sealing lip gives the sealing element a high elastic deformability, so that the sealing element can easily adapt to the shape of the inner wall of the housing upper part when inserting the flow in the upper housing part. It is advantageous if the cutting disc is inclined to the longitudinal axis of the housing, wherein the housing inlet opens on a first side of the cutting disc, preferably the filter element facing side of the cutting disc in the upper housing part and the housing outlet on the first side opposite the second side of the Cutting disc, preferably the filter element facing away from the side of the cutting disc, leads out of the upper housing part.

Hydraulic fluid, which flows into the housing upper part via the housing inlet, preferably passes directly into a raw area arranged below the separating disk, from which the hydraulic fluid can reach the raw side of the filter element. Filtered hydraulic fluid is preferably supplied from the clean side of the filter element to the region above the cutting disc, from which the filtered fluid can flow out via the housing outlet on the housing.

In an advantageous embodiment of the invention, the filter element forms a cylindrical filter cartridge which can be detachably and fluid-tightly connected to the flow-guiding element, and the flow-guiding element has at least one passage for filtered hydraulic fluid.

The filter cartridge may be aligned or parallel to the longitudinal axis of the housing of the filter device and occupy with its raw side a distance from the inner wall of the housing lower part, so that forms an annular space between the raw side of the filter cartridge and the inner wall of the housing base to which the liquid to be filtered are supplied can. The hydraulic fluid can flow through the filter cartridge radially from outside to inside, that is, the clean side of the filter cartridge is arranged on the inside. From the clean side of the filter cartridge, the filtered liquid can be conveyed via the at least one passage of the flow guide element to an area arranged above the flow guide element. from which the filtered liquid can flow out of the housing via the housing outlet.

The filter cartridge preferably has an upper end disk facing the flow guide element and a lower end disk facing away from the flow guide element, and a filter material is arranged between the upper end disk and the lower end disk, wherein a sleeve-shaped connecting part is positioned on the upper end disk, with a sleeve-like connection Connecting part of the flow guide is releasably connectable. With the help of the connecting part and the connecting part, the filter cartridge can be releasably connected to the flow guide in a simple manner.

Conveniently, the connecting part is integrally connected to the cutting disc. The cutting disc and the connecting part can form a one-piece plastic molded part.

The connecting part is preferably pluggable connectable to the connection part. For example, it can be provided that the connecting part in the

Connector is inserted. Alternatively it can be provided that the connection part can be inserted into the connection part.

At the connecting part and / or on the connecting part a sealing element is favorably arranged, with which it is ensured that unfiltered hydraulic fluid can not get directly into the connecting part, without first to flow through the filter cartridge.

The sealing element, which is arranged on the connecting part or on the connecting part, is advantageously formed on the connecting part or on the connecting part.

It is particularly advantageous if the sealing element, which is arranged on the connecting part and / or on the connecting part, is designed as a sealing lip. As already mentioned, the flow guide is subject to a relatively low pressure load, even if the pressure of the hydraulic fluid is a total of several 100 bar. However, in order to keep the material used of the flow guide as small as possible, it is advantageous if the flow guide element has at least one support rib, which can be applied to the inner wall of the housing upper part. The flow guide element can be supported on the inner wall of the housing upper part via the at least one support rib.

As already mentioned, it is favorable if the flow guide element has a cutting disk oriented obliquely to the longitudinal axis of the housing. In such a configuration, it is advantageous if at least one support rib is integrally formed on the upper side of the cutting disk. By providing such a support rib can be counteracted in a structurally simple manner a tilting movement of the obliquely aligned to the longitudinal axis of the housing cutting disc.

In order to support the flow guide in the axial direction, it has in an advantageous embodiment of the invention, an axial extension, which can be applied to a ceiling wall of the upper housing part. The axial extension may be formed, for example in the form of a hollow cylinder, on the outside of which preferably at least one support rib is formed, wherein the support rib extends radially outwardly relative to the longitudinal axis of the hollow cylinder.

In the hollow cylinder immersed in a preferred embodiment of the invention, a pressure sensor, by means of which the pressure difference between the raw area and the clean area of the upper housing part can be detected. Conveniently, the interior of the hollow cylinder is in fluid communication with the raw region of the filter device via a connecting channel formed in the flow guiding element, so that the pressure of the hydraulic fluid prevailing in the raw region can be detected in the interior of the hollow cylinder. The pressure sensor may have a transverse bore, via which the pressure of the hydraulic fluid prevailing in the clean area can be detected.

The pressure sensor is preferably designed as a pressure switch which changes its switching position as a function of the pressure difference between the pressure prevailing in the raw area and the pressure prevailing in the clean area.

The following description of an advantageous embodiment of the invention is used in conjunction with the drawings for further explanation. Show it :

1 shows a perspective view of an embodiment of a filter device;

Figure 2 is a plan view of the filter device of Figure 1;

FIG. 3: a sectional view of the filter device along the line 3-3 in FIG

Figure 2;

FIG. 4 shows a sectional view of the filter device along the line 4-4 in FIG

Figure 2;

FIG. 5: a sectional view of the filter device along the line 5-5 in FIG

FIG. 3;

FIG. 6: a sectional view of the filter device along the line 6-6 in FIG

FIG. 3;

FIG. 7 is a perspective view of an upper housing part of the filter device from FIG. 1 at an angle from below; FIG. 8 is a perspective view of a flow-guiding element of the filter device from FIG. 1 at an angle from below and FIG

FIG. 9 shows a perspective view of the flow-guiding element

Figure 8 obliquely from above.

In the drawing, an advantageous embodiment of a filter device according to the invention is shown schematically and overall occupied by the reference numeral 10. The filter device 10 forms a pressure filter with which hydraulic fluid can be filtered, which is under a pressure of several 100 bar, for example under a pressure of 450 bar. The filter device 10 has a housing 12 with an upper housing part 14 and a lower housing part 16. The lower housing part 16 is detachably connectable to the upper housing part 14, in the illustrated embodiment, the lower housing part 16 with the upper housing part 14 can be screwed.

The lower housing part 16 is cup-shaped, this is particularly clear from Figures 3 and 4. It has a lower housing jacket 18 with a circular cylindrical outer wall 20 and a circular cylindrical

Inner wall 22 and a bottom 24, to the outside of a hexagon 26 connects.

The lower housing shell 18 carries at its end facing the housing upper part 14 on the outside an annular groove 28 which receives a not shown in the drawing to achieve a better overview of the sealing ring. At a distance from the annular groove 28, the jacket 18 on the outside on an external thread 30 which can be screwed into a complementary ausgestaltetes internal thread 32 of the upper housing part 14.

The housing upper part 14 has a housing inlet 34 and a housing outlet 38 arranged at a same height as the housing inlet 34 with respect to a longitudinal axis 36 of the housing 12, the housing outlet 38 lying diametrically opposite the housing inlet 34. The housing inlet 34 has an internal thread 40 for connecting a hydraulic line, via which the filter device 10 to be filtered hydraulic fluid can be supplied. In a corresponding manner, the housing outlet 38 has an internal thread 42 for connecting a hydraulic line, via which filtered hydraulic fluid can be removed from the filter device 10.

The upper housing part 14 has an upper housing jacket 44, which is covered on the side facing away from the housing lower part 16 by a housing cover 46. The upper housing shell 44 has an inner wall 48, which forms an elliptical inner wall section 50 relative to the longitudinal axis 36 at the level of the housing inlet 34 and the housing outlet 38, to which a transition section 52 connects in the direction of the housing lower part 16. The transition section 52 forms a transition from the elliptical inner wall section 50 to a circular inner wall section 54, which extends up to the housing cover 46 facing away from lower end face 56 of the upper housing part 14 and the internal thread 32 has.

The outer wall of the upper housing jacket 44 is formed in the region of the housing inlet 34 by a first planar outer wall section 58 and in the region of the housing outlet 38 by a second planar outer wall section 60 which each extend from an upper side 62 of the upper housing part 14 to the lower end side 56. In the circumferential direction between the first planar outer wall section 58 and the second planar outer wall section 60, the upper housing shell 44 forms on the outside a first circular arc-shaped outer wall section 64 and a second circular arc-shaped outer wall section 66, wherein the two arcuate outer wall sections 64, 66 are diametrically opposed to each other and circumferentially over each extend an angular range of about 115 °.

The main axis 67 of the elliptical inner wall 50 is aligned perpendicular to a connecting axis 68, the housing inlet 34 with the

Housing outlet 38 connects. This becomes clear in particular from FIG. The provision of the elliptical inner wall section 50 and the circular arcuate outer wall portions 64 and 66 has the consequence that the upper housing part 14 in the region of the housing inlet 34 and in the region of the housing outlet 38 has a greater wall thickness than in the remaining peripheral areas, the areas of different material thickness of the housing top 14 continuously merge into one another. With the exception of the internal threads 40 and 42, via the hydraulic fluid can flow into the housing 12 and flow out of the housing 12, the upper housing part 14 has no flow channels, in particular, the upper housing part 14 has no sudden changes in material thickness and thus no jumps in rigidity, to which under the influence of the pressurized hydraulic fluid, the pressure stiffness of the housing 12 could interfere with stress peaks.

The upper housing part 14 is therefore characterized as well as the lower housing part 16 by a very high compressive stiffness at relatively low material thickness.

In the upper housing part 14, a flow guide 70 is used, which is formed as a one-piece plastic molding and a cutting disc 72 forms, which is aligned obliquely to the longitudinal axis 36 of the housing 12 and on its outer periphery a formed on the cutting disc 72 sealing lip 74 carries. The cutting disk 72 is oriented such that the housing inlet 34 is disposed below the cutting disk 72 and that the housing outlet 38 is disposed above the cutting disk 72. This becomes clear in particular from FIG.

Integrally connected to the underside of the cutting disk 72 is a sleeve-shaped connecting part 76 which, with respect to the longitudinal axis 36, extends up to the level of the annular groove 28 formed in the lower housing jacket 18.

Coaxially to the longitudinal axis 36 of the housing 12, a projection in the form of a hollow cylinder 78 adjoins the upper side of the cutting disk 72 and extends with its end facing away from the blade 72 on the housing cover 46 is supported.

On the outside of the hollow cylinder 78 and the top of the cutting disc 72, a first support rib 80, a second support rib 82 and a third support rib 83 are formed, with which the cutting disc 72 on the housing inlet 34 side facing away from the elliptical inner wall portion 50 is supported. The support ribs 80, 82, 84 extend to the level of a radially inwardly directed step 86, which extends uniformly over the entire circumference of the elliptical inner wall portion 50 and forms an axial stop for the support ribs 80, 82 and 84.

The lower housing part 16 surrounds a filter element, which is designed as a filter cartridge 88 in the illustrated embodiment. The filter cartridge 88 has an upper end disk 90 facing the flow guide element 70 and a lower end disk 82 facing away from the flow guide element 70, between which extends a filter material 94 which is supported on the inside on a support tube 96. The support tube 96 has a plurality of passage openings 98 and the filter material 94 is folded in a star-shaped manner in the usual manner and can be traversed in the radial direction from outside to inside by hydraulic fluid.

The upper end disk 90 has a drain opening 100, via which filtered hydraulic fluid can flow out of the filter cartridge 88 in the axial direction. At the upper end plate 90, a sleeve-shaped connecting part 102 is held, which can be inserted into the sleeve-shaped connection part 76 of the flow guide 70 and on its upper end plate 90 remote end portion outside a sealing lip 104 carries, which bears tight against the inside of the sleeve-shaped connection part 76.

At the lower end plate 92 a per se known bypass valve 106 is arranged in the usual manner. The bypass valve 106 ensures that in case a blockage of the filter material 94 hydraulic fluid can flow through the filter cartridge 88.

The lower end plate 92 is supported on the housing bottom 24 of the lower housing part 16 via a cup-shaped support element 110 having a plurality of perforations 108.

Between the first support rib 80 and the second support rib 82, the separation disk 72 has a first passage 81, and between the second support rib 82 and the third support rib 84, the separation disk 72 has a second passage 83. This becomes clear in particular from FIG.

The flow guide 70 divides the interior of the upper housing part 14 into a raw area 112, into which the housing inlet 34 opens, and a clean area 114, from which the housing outlet 38 leads out. The raw area 112 is connected via an annular space 116, which surrounds the filter cartridge 88 in the circumferential direction, with the raw side 118 of the filter cartridge 88 in fluid communication. Liquid to be filtered can flow into the blank area 112 via the housing inlet 34 and flow through the filter cartridge 88 radially from outside to inside. The hydraulic fluid thereby passes to the clean side 120 of the filter cartridge 88. The clean side 120 is disposed on the inside of the filter material 94 and is above the drain opening 100 of the upper end plate 90, the adjoining connecting part 102 and the connecting part 76 with the first passage 81 and second passage 83 of the cutting disc 72 in fluid communication, and can pass through the passages 81, 83 in the clean region 114, from which the filtered liquid can flow out of the housing 12 via the housing outlet 38.

If the filter cartridge 88 is to be exchanged, then the lower housing part 16 can be unscrewed from the upper housing part 14, so that the filter cartridge 88 is accessible to the user. After the replacement of the filter cartridge 88, the lower housing part 16 can be bolted to the upper housing part 14 again. The hydraulic fluid can have a pressure of several 100 bar. Despite this large pressure load, the upper housing part 14 and the lower housing part 16 can be produced in a material-saving manner, wherein for the production of the upper housing part 14 as well as for the production of the lower housing part 16, a cold-forming process or a hot-forming process can be used. In particular, it can be provided that the housing upper part 14 is designed as a steel extruded part or as a forged part.

In order to detect the pressure difference between the prevailing in the raw area 112 pressure of the hydraulic fluid and the pressure prevailing in the clean area 114 hydraulic fluid, the filter device 10, a differential pressure sensor 124 which is configured in the illustrated embodiment as a differential pressure switch, the housing cover 46 passes through and into the hollow cylinder 78 of the flow guide 70 dips. The interior of the hollow cylinder 78 is connected via a formed in the flow guide 70 connecting channel 126 with the raw area 112 in flow communication. To seal the interior of the hollow cylinder 78, the differential pressure sensor 124 carries a first sealing ring 128, which bears tight against the inside of the hollow cylinder 78. The differential pressure sensor has a screwed into the housing cover 46 sensor housing 130 in which a piston 132 is held coaxially with the longitudinal axis 36 of the housing 12 back and forth. On the side facing the flow guide 70 bottom of the piston 132 counteracts the force of a return spring 134 of the prevailing pressure in the interior of the hollow cylinder 78, that is, the pressure of the Rohbereichs 112, and on the flow guide 70 remote from the top of the piston 132 acts in the clean area 114 prevailing pressure. For this purpose, the inner space 136 of the sensor housing 130, which is arranged above the piston 132, is in fluid communication with the clean area 114 via a transverse bore 138 and a thread 140. Above the transverse bore 114, the thread 140 is sealed by means of a second sealing ring 142. On the piston 132, a permanent magnet 144 is held, which is outside the Sensor housing 130 is arranged associated magnetic field sensitive element 146. In the illustrated embodiment, the magnetic field-sensitive element is designed as a reed contact.

Depending on how great the pressure difference is between the pressure prevailing in the raw area 112 and the pressure prevailing in the clean area 114, the piston 132 and thus also the permanent magnet 144 assume a distance to the magnetic-field-sensitive element 146 which is predetermined by the force of the return spring 134. The strength of the magnetic field prevailing at the location of the magnetic field-sensitive element 146 is consequently dependent on the pressure difference, so that a differential pressure-dependent sensor signal can be provided by the magnetic-field-sensitive element. The pressure difference is dependent on the degree of contamination of the filter material 94. The greater the degree of contamination, the greater the pressure difference detected by the differential pressure sensor 124. By means of the differential pressure sensor 124 can thus be provided depending on the degree of contamination of the filter material signal.

Claims

P A T E N T A N S P R E C H E

Filter device for filtering a hydraulic fluid with a housing (12) having an upper housing part (14) and with the upper housing part (14) detachably connectable housing lower part (16), wherein the upper housing part (14) has a housing inlet (34) for hydraulic fluid to be filtered and a housing outlet (38) for filtered hydraulic fluid and in the housing lower part (16) a filter element (88) is arranged, the raw side (118) with the housing inlet (34) in flow communication and the clean side (120) with the housing outlet (38) in Flow connection is characterized in that the upper housing part (14) has a convexly outwardly curved inner wall (48) along its entire circumference, and in that the upper housing part (14) an insertable flow guide (70) is arranged, which the interior of the upper housing part (14 ) into a raw area (112) and a clean area (114), wherein the raw area (11 2) is in flow communication with the raw side (118) of the filter element (88) and the housing inlet (34) opens into the raw area (112), and wherein the clean area (114) is in fluid communication with the clean side (120) of the filter element (88) stands and the housing outlet (38) leads out of the clean area (114).

Filter device according to claim 1, characterized in that the inner wall (48) of the upper housing part (14) is designed in a direction perpendicular to a longitudinal axis (36) of the housing (12) aligned plane circular or elliptical.

Filter device according to claim 1 or 2, characterized in that the inner wall (48) of the upper housing part (14) with respect to the longitudinal axis (36) of the housing (12) at the level of the housing inlet (34) and the housing outlet (38) an elliptical inner wall portion (50), and in that the inner wall (48) of the upper housing part (14) has a circular inner wall section (54) in an end section facing the lower housing part (16).

4. Filter device according to claim 1, 2 or 3, characterized in that the housing upper part (14) in the circumferential direction between the housing inlet (34) and the housing outlet (38) convexly outwardly curved outer wall sections (64, 66).

5. Filter device according to claim 4, characterized in that the outer wall sections (64, 66) of the upper housing part (14) are designed in a circular arc or elliptical arc.

6. Filter device according to one of the preceding claims, characterized in that the housing upper part (14) has areas of different material thickness, which merge into one another continuously.

7. Filter device according to one of the preceding claims, characterized in that the housing outlet (38) diametrically opposite the housing inlet (34).

8. Filter device according to one of the preceding claims, characterized in that the housing inlet (34) and the housing outlet (38) relative to the longitudinal axis (36) of the housing (12) are arranged at the same height.

9. Filter device according to one of the preceding claims, characterized in that the upper housing part (14) by cold or

Hot working is made.

10. Filter device according to one of the preceding claims, characterized in that the flow guide (70) has a cutting disc (72) having a sealing element (74) which is sealingly engageable with the inner wall (48) of the upper housing part (14).

11. Filter device according to claim 10, characterized in that the sealing element forms a formed on the cutting disc (72) sealing lip (74).

12. Filter device according to claim 10 or 11, characterized in that the cutting disc (72) to the longitudinal axis (36) of the housing (12) is inclined, wherein the housing inlet (34) on a first side of the cutting disc (72) in the housing upper part ( 14) and wherein the housing outlet (38) leads out of the housing upper part (14) on the second side of the separating disk (72) opposite the first side.

13. Filter device according to claim 12, characterized in that the first side of the cutting disc (72) facing the filter element (88) and that the second side of the cutting disc (72) facing away from the filter element (88).

14. Filter device according to one of claims 10 to 13, characterized in that the filter element forms a cylindrical filter cartridge (88) which is releasably and fluid-tightly connected to the flow guide (70), and in that the flow guide (70) at least one passage (81 , 83) for filtered hydraulic fluid.

15. Filter device according to claim 14, characterized in that the filter cartridge (88) has a flow guide (70) facing the upper end plate (90) and the flow guide (70) facing away from lower end plate (92), between which a filter material (94). is arranged, wherein at the upper end plate (90) a sleeve-shaped connecting part (102) is arranged, which is provided with a hülsenför- Migen connecting part (76) of the flow guide (70) is detachably connectable.

16. Filter device according to claim 15, characterized in that the connecting part (102) with the connection part (76) is pluggable connectable.

17. Filter device according to claim 16, characterized in that a sealing element (104) is arranged on the connecting part (102) and / or on the connecting part (76).

18. Filter device according to claim 17, characterized in that the sealing element (104) is integrally formed on the connecting part (102) or on the connecting part (76).

19. Filter device according to claim 18, characterized in that the sealing element is designed as a sealing lip (104).

20. Filter device according to one of the preceding claims, characterized in that the flow-guiding element (70) has at least one support rib (80, 82, 84) which can be applied to the inner wall (48) of the upper housing part (14).

21. Filter device according to one of the preceding claims, characterized in that the flow guide element (70) has an axial extension (78) which can be applied to a top wall (46) of the housing upper part (14).