Filter Element

Abstract

A filter element has a folded bellows folded in a zigzag shape and provided with folds. The folded bellows has a first section with a first curvature and a second section with a second curvature. The first curvature is greater than the second curvature. The folds of the folded bellows in the first section have a varying fold height.

Claims

1. A filter element comprising: a folded bellows folded in a zigzag shape and comprising folds, wherein the folded bellows comprises a first section comprising a first curvature and further comprises a second section comprising a second curvature, wherein the first curvature is greater than the second curvature, and wherein the folds of the folded bellows in the first section have a varying fold height.

2. The filter element according to claim 1, wherein the folds of the folded bellows in the first section include first folds comprising a first fold height and further include second folds comprising a second fold height, wherein the first fold height is greater than the second fold height.

3. The filter element according to claim 2, wherein the first folds and the second folds form M-folds.

4. The filter element according to claim 1, wherein the folds of the folded bellows in the first section include first folds comprising a first fold height extending between an inner radius of the first section and an outer radius of the first section, and wherein the folds of the folded bellows in the first section further include second folds comprising a second fold height extending from the outer radius of the first section in a direction toward the inner radius, wherein the second folds are arranged between the first folds.

5. The filter element according to claim 1, wherein the first section is a circular section.

6. The filter element according to claim 1, wherein the second section is a straight section.

7. The filter element according to claim 1, wherein the folded bellows comprises a third section with a third curvature, wherein the third curvature is greater than the second curvature, and wherein the folds of the folded bellows in the third section comprise a varying fold height.

8. The filter element according to claim 7, wherein the third section is a circular section.

9. The filter element according to claim 1, wherein the folded bellows comprises a radial extension that changes in an axial direction of the folded bellows.

10. The filter element according to claim 1, wherein the folded bellows comprises an oval cross section or a stadium-shaped cross section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 shows a schematic illustration of a filter element according to a first embodiment.

[0029] FIG. 2 shows a schematic detail view of a first section of the folded bellows of FIG. 1.

[0030] FIG. 3 is a schematic illustration of a filter arrangement with a filter element.

[0031] FIG. 4 shows a schematic illustration of a filter element as a variant of FIG. 1.

[0032] In the Figures, same reference characters refer to same functions or same elements inasmuch as nothing to the contrary is indicated.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0033] FIG. 1 shows a schematic illustration of a filter element in plan view. The filter element has an endless folded bellows 1 which is formed of a zigzag-shaped filter medium. In the cross section view of FIG. 1, one can recognize a stadium shape of the folded bellows 1 with two curved round sections 2, 2 and two straight sections 3, 3. In particular at the straight sections 3, 3, one can see the zigzag-shaped folds with outer fold edges 6 and inner fold edges 7 between which fold sections 8 are positioned. In this and in the following Figures, only some fold edges and fold sections are provided with reference characters in an exemplary fashion.

[0034] The straight fold sections 3, 3 have no curvature but extend straight. This is indicated by the dash-dotted line 5. In order to realize the oval shape or stadium shape, further curved sections 2, 2 with folds are provided. The resulting curvature is indicated by the dash-dotted line 4 and follows in the illustrated example a circular section. The sections 2, 2 with a circular curvature 4 have thus a stronger curvature than the straight sections 3, 3 that have no curvature 5. In FIG. 1, a radius R.sub.1 for the right circular section 2 is indicated in order to illustrate the curvature 4.

[0035] In the straight sections 3, 3, the spacings of the inner fold edges 7 and of the outer fold edges 6 are constant. One speaks in this context also of a constant fold height H.sub.1 or constant fold depth. In the more strongly curved circular sections 2 or 2, folds with different fold height are provided. The example of the section 2 illustrates that folds of the height H.sub.1, identical to the fold height of the straight sections 3, 3, are present. Moreover, less deep folds are provided which have a height H.sub.2<H.sub.1. One can say that, between folds of the depth H.sub.1, folds with reduced fold depth H.sub.2 are provided from the exterior. The folds of reduced depth, i.e., with less wide fold sections, can also be referred to as intermediate folds.

[0036] In this way, it is made easier to maintain the curvature 4 in the stronger curved section 2 and still ensure a sufficient or large filter surface. In FIG. 2, a detail illustration of a section 2 is illustrated in order to explain the fold geometry.

[0037] In FIG. 2, three circular arc sections with a respective radius R.sub.1, R.sub.2, and R.sub.3 are indicated. The radius R.sub.1 corresponds to the inner radius R.sub.1 as indicated in FIG. 1 for the section 2. The radius R.sub.3 corresponds to the outer radius of the section 2. Fold sections 8 extend between the inner and the outer radius R.sub.1, R.sub.3. These folds have a fold height H.sub.1=R.sub.3R.sub.1. The resulting outer fold edges are identified by 6 and the inner fold edges by 7. Moreover, at regular spacings folds with reduced fold height H.sub.2 are provided. Between two fold sections 8 with great fold depth H.sub.1 a fold 12 with shorter fold sections 13 is provided that adjoin a fold edge 9. The fold edge 9 extends on the circular section according to radius R.sub.2 which can also be referred to as intermediate radius.

[0038] One can speak of contacting M-shaped folds or M-folds. This is indicated by reference character 12. The folds with reduced height H.sub.2 extend from the exterior in the direction toward the interior RI of the resulting endless folded bellows (compare FIG. 1). In the orientation of FIG. 2, the interior of the folded bellows is to the left and the exterior space to the right.

[0039] Due to the M-folds or due to the varying fold height as a function of the curvature radius of the section in the folded bellows, it is prevented, on the one hand, that the fold sections snugly contact each other, in particular in the region of the inner radius R.sub.1, and additionally the fold stability is increased. On the one hand, the folds with reduced height H.sub.2 space apart the fold sections 8 with great depth and provide an additional contribution to the filter surface. As a whole, an improved fold distribution relative to sections with constant fold height is provided in this way.

[0040] The folded bellows is suitable in particular for use as an air filter for intake air of a motor in a motor vehicle. In FIG. 3, in an exemplary fashion an embodiment for a filter arrangement 20 is indicated. The filter arrangement 20 comprises a filter housing 10 in which a filter element 1 of the type of an endless folded bellows, as illustrated, for example, in FIG. 1, is inserted. Raw air RO is supplied to the filter housing 10, guided through the filter medium with its folds, and supplied as clean air RE to an internal combustion engine 11 of a motor vehicle. In this way, it is achieved that the combustion air RO is purified from contaminants or particles.

[0041] In FIG. 4, a variant of FIG. 1 or further development of a filter element as an air filter is illustrated. The filter element comprises again an endless folded bellows 19 that comprises several sections of different curvature illustrated in cross section. A first section 2 is illustrated with M-folds and varying fold heights, as explained in connection with section 2 of FIG. 1. In clockwise direction, a straight section 14, a curved section 15, and a further curved section 16 adjoin the section 2. In order to close the circumference to the straight section 3, further curved sections, not identified in detail, of filter material folded in a zigzag shape are provided.

[0042] Along the circumference of the folded bellows 19, the curvature changes its sign. The section 2 is identified with an inner radius of curvature R.sub.1 and the dash-dotted curvature 4. The adjoining straight section 14 has a disappearing curvature 5, the following section 15 a curvature 17, and the section 16 has a curvature 18 which can be referred to by a circle with the circle radius R.sub.4. One can see that the curvature, viewed from the interior RI of the folded bellows, changes its sign. At the transition from the section 15 to the section 16, the center of the circle for the radii R.sub.5 and R.sub.4 are displaced from the inner side RI to the exterior side. It is possible, for example, that the installation situation requires that folded bellows with changing curvature and, in particular, a sign change from concave to convex be made available. In this context, it is beneficial to realize the folds with varying height. In the example of FIG. 4, M-shaped folds result also wherein, for increasing the filter surface, folds with reduced depth or height in the direction relative to the respective radius of curvature are provided.

[0043] Even though the invention has been explained with the aid of embodiments, it can be modified in many ways. For example, in addition to the illustrated radii and shapes for the curved sections, other oval shapes of endless folded bellows can be provided also. It is possible to provide in the interior of the folded bellows a support tube in order to stabilize the filter medium when fluid to be filtered passes through. In addition to the proposed M-folds, also irregular spacings of the intermediate folds and the provision of folds of reduced depth between folds of great depth are conceivable. It is possible also to apply end disks to the fold profiles in order to realize a closed filter element. The end disks can be provided with connecting sockets or other passages for inflow and outflow of raw or clean fluid.

EMPLOYED REFERENCE CHARACTERS

[0044] 1, 19 folded bellows [0045] 2, 3 section [0046] 4, 5 curvature [0047] 6 outer fold edge [0048] 7 inner fold edge [0049] 8 fold section [0050] 9 fold edge [0051] 10 air filter housing [0052] 11 motor [0053] 12 M-fold [0054] 13 short fold section [0055] 14, 15, 16 section [0056] 17, 18 curvature [0057] 20 filter arrangement [0058] RO raw air [0059] RE clean air [0060] RI interior [0061] R.sub.i, R.sub.2, R.sub.3 radius [0062] H.sub.1, H.sub.2, H.sub.3 fold height