Abstract:
Disclosed are: a separation element ( 20 ) of a liquid separator ( 10 ) for the separation of liquid from an aerosol; a separation medium ( 38 ); a liquid separator ( 10 ); and a method for producing a separation element. The separation element ( 20 ) has at least one separation medium ( 38 ) for separating at least the liquid, the separation medium being arranged circumferentially about an element axis ( 22 ) in at least one medium layer ( 40 ). The aerosol is able to flow through the separation element ( 20 ) radially relative to the element axis ( 22 ). At least one medium layer ( 40 ) has, on a radially inward circumferential surface, at least one channel-shaped indentation ( 42 ) extending axially to the element axis ( 22 ) to realize at least one channel ( 44 ) for separated liquid.

Description:
Technical field 
       [0001]    The invention relates to a separation element of a liquid separator, in particular, an oil separator, in particular, of a crankcase ventilation system of an internal combustion engine, a compressor air/oil separator, or an air/oil separator box, for the separation of liquid from an aerosol. 
         [0002]    The invention also relates to a separation medium of a separation element of a liquid separator, in particular, an oil separator, in particular, of a crankcase ventilation system of an internal combustion engine, a compressor air/oil separator, or an air/oil separator box, for the separation of liquid from an aerosol. 
         [0003]    Furthermore, the invention relates to a liquid separator, in particular, an oil separator, in particular, of a crankcase ventilation system of an internal combustion engine, a compressor air/oil separator, or an air/oil separator box, for the separation of liquid from an aerosol, the liquid separator comprising a housing having at least one aerosol inlet for the aerosol and at least one gas outlet for gas liberated from the liquid, and at least one separator element having at least one separation medium for the separation of the liquid. 
         [0004]    Finally, the invention also relates to a method for producing a separation element of a liquid separator, in particular, an oil separator, in particular, of a crankcase ventilation system of an internal combustion engine, a compressor air/oil separator, or an air/oil separator box, for the separation of liquid from an aerosol. 
       BACKGROUND 
       [0005]    Separation elements known in the prior art, which have wound medium layers for separating liquid droplets or liquid aerosols from gases, comprise media that are selected for each respective product so that said media can be wound in a kink-free manner. 
         [0006]    U.S. Pat. No. 4,915,714 A discloses a fiber layer element and a method for using such an element to remove and collect small particles from liquids, or soluble solids from gas streams. The element is formed from one or more fibrous layers perforated by holes and supported by an appropriate support structure. The fiber layers are subjected to pressure, in order to achieve a desired thickness. The punched holes then contribute to creating discharge channels through which the liquids can flow out. 
         [0007]    The invention addresses the problem of creating a separation element, a separation medium, a liquid separator, and a method of the aforementioned type, with which it is as simple as possible to achieve the most efficient discharge of liquid possible. 
       SUMMARY 
       [0008]    The problem is solved according to the invention, in that the separation element comprises at least one separation medium for separating at least the liquid that is arranged in at least one medium layer circumferentially about an element axis, wherein the aerosol can flow through the separation element, for example, radially outwardly from radially inward or radially inwardly from radially outward, relative to the element axis, wherein the element axis extends vertically in space with at least one directional component in the normal operational orientation of the separation element, and wherein at least one medium layer of at least one separation medium has, on a circumferential surface that is radially inward relative to the element axis, a channel-shaped indentation extending axially to the element axis at least with one directional component, for example, in order to realize at least one channel, in particular, a discharge or drainage channel, for separated liquid. 
         [0009]    According to the invention, at least one medium layer has at least one separation medium on a circumferential surface of at least one channel-shaped indentation that is radially inward relative to the element axis. The at least one channel-shaped indentation extends axially to the element axis with at least one directional component. The element axis is arranged vertically in space with at least one directional component in the normal operational orientation of the separation element. In this manner, a channel is formed. This channel can act as a discharge channel or drainage channel, in particular, for the liquid entering the channel. The channel is preferably arranged vertically in space either at least with one directional component or completely. Separated liquid can then follow the force of gravity and run spatially downward in the at least one channel. It is thus easy to implement efficient discharging of the separated liquid. Depending on the direction of flow of the aerosol through the at least one separation medium, the at least one indentation is located on the inflow side or outflow side of the corresponding medium layer. The separated liquid can reach the channel ahead of or behind the corresponding medium layer in the direction of flow. 
         [0010]    Advantageously, a plurality of medium layers made of separation medium may be arranged in a layered manner. With a plurality of medium layers, a medium winding can thus be realized. Then, a radially outward circumferential surface of at least one medium layer laid radially further inward may delimit an indentation on the radially inward circumferential surface of an adjacent medium layer laid radially further outward. In this manner, at least one channel can be realized. The channel may advantageously act as a drainage channel. In one embodiment, the channel may be circumferentially closed, in particular, relative to the longitudinal direction thereof. 
         [0011]    Alternatively, different material layers may also be arranged between the medium layers with the separation medium. In this case, the different material layers delimit there the corresponding at least one channel. 
         [0012]    Advantageously, at least one separation medium may comprise at least one coalescence medium or be composed thereof. With a coalescence medium, even the smallest liquid droplets can be combined—in particular, coalesced—into larger liquid drops. The larger liquid drops can in turn be separated out and discharged in the at least one channel. 
         [0013]    Advantageously, the separation element—in particular, at least one separation medium—may have a plurality of channels-shaped indentations. In this manner, the separated liquid can be discharged at a plurality of places in the separation element. 
         [0014]    Advantageously, the liquid separator may be or have an oil separator, which may be arranged in a crankcase ventilation system of an internal combustion engine. Advantageously, the aerosol may be crankcase gas (blowby gas) from the crankcase of the internal combustion engine. Advantageously, the liquid to be separated may comprise or be composed of oil, in particular, motor oil. With the separation element, it is possible to separate out motor oil or other drop-shaped components such as water, fuel, or the like entrained in the blowby gas. The separated motor oil may be fed back to a motor oil circuit of the internal combustion engine. The blowby gas, liberated from the motor oil, may be fed to an air intake conduit or discharged to the environment. 
         [0015]    However, the invention is not limited here to an oil separator of a crankcase ventilation system of an internal combustion engine of a motor vehicle. The invention may also be used outside of motor vehicle technology, in particular, with industrial engines. The invention may also be applied with different droplet separators or liquid separators, in particular, for compressor air/oil separation or with air/oil separator boxes. 
         [0016]    In one advantageous embodiment, at least one part of the at least one separation medium may be wound circumferentially about the element axis in a plurality of medium layers. Winding makes it easy to realize a plurality of medium layers. In this manner, the separation element can be obtained from one piece—in particular, a medium web—of a corresponding separation medium. 
         [0017]    Advantageously, the at least one separation medium may be wound about a winding core. Advantageously, the winding core may at least comprise a component already being used for the liquid separator, in particular, a support tube of the separator element or for the separator element. This obviates the need to separate the separation medium from the winding core after the winding. Alternatively, a separate winding core may be used, for example, in the form of a fabric tube or another tubular and fluid-permeable structure such as an expanded mesh, a perforated plate, or the like. 
         [0018]    In another advantageous embodiment, a plurality of channel-shaped indentations may be arranged so as to be uniformly distributed circumferentially, and/or a plurality of channel-shaped indentations may be arranged so as to be non-uniformly distributed circumferentially. In this manner, a plurality of discharge channels can be realized at different places on the at least one medium layer, in particular, within the medium winding formed by a plurality of medium layers, over correspondingly large parts of the circumference, in particular, over the entire circumference. Thus, separated liquid can be discharged at a plurality of places on the separation element. The efficiency of the liquid discharge can thus be further improved. 
         [0019]    Advantageously, a plurality of channel-shaped indentations may be arranged so as to be uniformly distributed. In this manner, the liquid can be discharged more uniformly. 
         [0020]    Alternatively or additionally, a plurality of channel-shaped indentations may be arranged so as to be non-uniformly distributed. Different material properties of the separation medium along the circumference or—with a plurality of material layers—different radial distances of the corresponding indentations to the element axis may thus be taken into account, and/or may influence the distribution of the indentations when the separation element is being produced. Overall, the liquid discharge in the entire separation element can be improved. 
         [0021]    In another advantageous embodiment, at least two channel-shaped indentations may be different with respect to the respective cross-sections—in particular, the shapes thereof and/or the cross-sectional surfaces thereof—transversely to the flow path of the separated liquid, and/or at least two channel-shaped indentations may be identical with respect to the respective cross-sections thereof. In this manner, the separation channels can be specifically adapted to different requirements. 
         [0022]    Advantageously, at least two indentations may have different cross-sectional surfaces, such that the flow cross-sections for the separated liquid are different. 
         [0023]    Alternatively or additionally, the shapes of the cross-sections of at least two indentations may be different. In particular, the at least two indentations may extend with different circumferential widths relative to the element axis, so as to be able each to cover a differently-sized circumferential region. 
         [0024]    Alternatively or additionally, at least two channel-shaped indentations may be identical in the cross-sections thereof—in particular, the shape and/or cross-sectional surface thereof. It is then possible to have uniform discharging of the liquid. 
         [0025]    Overall, appropriately selecting the cross-section of the channel-shaped indentations makes it possible to adapt—in particular, to vary—the characteristic of the fluid discharge. 
         [0026]    In another advantageous embodiment, at least one channel-shaped indentation may extend to a margin of the at least one separation medium that is spatially downward in the normal operational orientation—in particular, over the entire axial extension of the at least one separation medium relative to the element axis. In this manner, the liquid can be guided to the spatially downward end face of the separation element, and discharged there from the separation element. 
         [0027]    Advantageously, the at least one channel-shaped indentation—in particular, the at least one channel—may be open to a downward end face of the at least one separation medium, in particular, to both end faces of the separation medium. The at least one opening of the at least one channel-shaped indentation makes it possible for the separated liquid to depart from the at least one separation medium. 
         [0028]    Advantageously, at least one channel-shaped indentation may extend over the entire axial extension of the at least one separation medium relative to the element axis. In this manner, the liquid can be guided continuously through the separation element, from the axially upward end face relative to the element axis in the normal operational orientation to the axially downward end face. 
         [0029]    In another advantageous embodiment, at least one separation medium in the region of at least one channel-shaped indentation may be bent exclusively at the radially inward circumferential surface thereof or at the radially inward and radially outward circumferential surfaces. In this manner, corresponding indentations are located at least on the radially inward circumferential surface. 
         [0030]    Advantageously, at least one channel-shaped indentation bent radially outward is realized exclusively at the radially inward circumferential surface of the at least one separation medium. The radially outward circumferential surface of the at least one separation medium lying opposite to the at least one indentation may be realized without corresponding bends and follow a uniform course. Thus, a radial extension—in particular, thickness—of the corresponding medium layer of the at least one separation medium can be lower overall. 
         [0031]    Alternatively, the at least one separation medium in the region of at least one indentation may be bent at the radially inward and radially outward circumferential surfaces thereof. Alternatively, the at least one separation medium in the region of at least one indentation may be bent at the radially inward and radially outward circumferential surfaces thereof. In this manner, less—in particular, no—compression of the material of the at least one separation medium between the radially outward circumferential surface and the radially inward circumferential surface is required. 
         [0032]    In another advantageous embodiment, the at least one separation medium may have at least one embossment and/or punch along at least one channel-shaped indentation, at least on the radially inward circumferential surface relative to the element axis. With the at least one embossment and/or punch, a predetermined bending region—in particular, a predetermined bending line—can be realized, along which the radially inward circumferential surface can be bent to the at least one channel-shaped indentation. A corresponding shaping—in particular, bending—of the at least one channel-shaped indentation can thus be realized in an easier and more precise manner. The at least one embossment and/or punch makes it possible for the position and contour of the at least one indentation to be more precisely defined. 
         [0033]    In another advantageous embodiment, the at least one separation medium may be non-stretchable along the radially inward and radially outward circumferential surfaces thereof relative to the element axis. In this manner, the stability of the at least one separation medium can be improved. A more stable shape design can be realized. 
         [0034]    Advantageously, the at least one separation medium may be non-stretchable at the circumferential surfaces thereof under normal operational conditions and/or under normal production conditions. This makes it possible to prevent the circumferential surfaces from being able to stretch during production or operation. It is thus possible to prevent the at least one separation medium from stretching or swelling during operation. In addition, the radially inward circumferential surface can be successfully bent or folded over along corresponding regions—in particular, lines—when the at least one separation medium is laid—in particular, wound—uniformly and in particular cylindrically relative to the element axis. Channel-shaped indentations can thus automatically be created at the corresponding fold regions or bend regions. In this manner, realizing the at least one channel-shaped indentation does not necessitate separate production steps or tools. 
         [0035]    In another advantageous embodiment, at least one separation medium may be compressed in the radial direction relative to the element axis along at least one channel-shaped indentation. In this manner, the radially outward circumferential surface and the radially inward circumferential surface of the at least one separation medium can be moved relative to one another in order to produce the at least one indentation. Combining the compressibility of the material between the circumferential surfaces and the non-stretchability in the region of the circumferential surfaces of the at least one separation medium makes it possible to easily—in particular, automatically—realize the at least one indentation when the at least one separation medium is being laid and in particular wound. 
         [0036]    The at least one channel may be formed almost of itself due to the structure and/or rigidity of the laid—in particular, wound—separation medium. Additional components or tools are thus not required. 
         [0037]    The at least one separation medium may be relatively rigid. This makes it possible to form corresponding pleats and/or kinks—which can produce the at least one channel-shaped indentation—when the separation medium is being, in particular, cylindrically laid and in particular wound. The pleats/kinks may automatically extend axially to the element axis, so as to be most suitable as discharge channels. 
         [0038]    In another advantageous embodiment, at least one separation medium may at least comprise or be composed of medium fibers, in particular, glass fibers. With medium fibers, it is easy to realize separation media that are only slightly stretchable, or are non-stretchable under normal conditions, at the circumferential surfaces thereof, and that are compressible in the radial direction, i.e., perpendicular to the circumferential surfaces. 
         [0039]    Advantageously, a layer thickness of at least one medium layer of the at least one separation medium may be approximately between  0 . 5  and  5  mm, preferably between 1 and 3 mm, particularly preferably between 1.5 and 2.5 mm. 
         [0040]    Advantageously, an inner diameter of the separation element may be approximately between 20 and 500 mm, in particular between 30 and 200 mm, e.g., approximately 47 mm. 
         [0041]    Advantageously, a winding thickness of the separation element—i.e., the difference between the outer radius and the inner radius—may be approximately between 4 and 120 mm, in particular between 15 and 25 mm, preferably approximately 20 mm. 
         [0042]    The layer thickness, the inner diameter, the outer diameter, and the winding thickness may also be smaller or larger. 
         [0043]    Advantageously, the separation element may have approximately between two and 60 medium layers, preferably approximately 12 medium layers, of the at least one separation medium. More or fewer medium layers may also be provided. 
         [0044]    Advantageously, a specific minimum bend radius of the at least one separation medium at which the at least one separation medium can be laid circumferentially and in particular cylindrically relative to the element axis without producing kinks or bends, especially due to mechanical tension, may be greater than the inner diameter of the separation element. In other words, the at least one separation medium may be laid, in particular, wound at least in a partial region of the separation element with a bend radius that is smaller than the minimum bend radius, so that the least one channel-shaped indentation is produced automatically when the at least one separation medium is laid and in particular wound. 
         [0045]    The specific minimum bend radius of the at least one separation medium is characterized by the stretching properties, in particular, the non-stretchability of the at least one separation medium at the circumferential surfaces thereof, in combination with the compressibility thereof between the circumferential surfaces. The stretching properties may be determined by the rigidity of the at least one separation medium. 
         [0046]    The specific minimum bend radius may be determined experimentally by cylindrically bending the separation medium. The radius at which the first kinks or bends are recognizable, in particular, with the unaided eye, in particular, on the radially inward circumferential side can be designated the specific minimum bend radius. 
         [0047]    The technical problem is also solved with the separation medium in that a specific minimum bend radius of the at least one separation medium is greater than the inner diameter of the separation element. 
         [0048]    The technical problem is also solved with the liquid separator, in that the at least one separation medium is arranged in at least one medium layer circumferentially about an element axis, wherein the at least one separation element is arranged in the housing such that the aerosol can flow through the at least one separation medium radially outwardly from radially inward or radially inwardly from radially outward, relative to the element axis, wherein the element axis extends vertically in space at least with one directional component in the normal operational orientation of the separation element, and wherein at least one medium layer of the at least one separation medium has, on a circumferential surface that is radially inward relative to the element axis, at least one channel-shaped indentation extending axially to the element axis at least with one directional component in order to realize at least one channel for separated liquid. 
         [0049]    Advantageously, the housing may have at least one liquid outlet for the separated liquid. Through the liquid outlet, the separated liquid can be removed from the housing. 
         [0050]    Finally, the technical problem is solved with the method in that a separation medium is realized as a medium web, the medium web being laid—in particular, wound—circumferentially into a medium winding about an element axis, wherein a radially inner radius of the medium winding is smaller than a specific minimum bend radius of the separation medium at which the separation medium can be bent without pleats and without kinks, such that during laying, at least one channel-shaped indentation extending axially to the element axis at least with one directional component, in order to realize at least one channel for separated liquid, is realized on at least one radially inward circumferential surface of at least one medium layer of the at least one separation medium. For example, first the specific minimum bend radius of a medium web is determined, and then a radially inner radius of the medium web that is smaller than the determined specific minimum bend radius is selected in production. It is also possible to first define an inner radius of the medium winding to be used in a product, and then select a medium or medium web with which the specific minimum bend radius has been determined, preferably in advance, this bend radius being greater than the previously defined inner radius of the medium winding to be realized. In both method variants, however, it is preferable to first determine the specific minimum bend radius of at least one medium or at least one medium web. It is also preferable in both method variants to select a medium that has a specific minimum bend radius that is greater than the radially inner radius of the medium winding. 
         [0051]    Moreover, the features and advantages demonstrated in connection with the separation element according to the invention, the separation medium according to the invention, the liquid separator according to the invention, and the method for producing a separation element according to the invention and the respective advantageous embodiments thereof are mutually applicable, mutatis mutandis. It shall be readily understood that the individual features and advantages can be combined with one another, wherein other advantageous effects that go beyond the sum of the individual effects may emerge. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0052]    Other advantages, features, and details of the invention shall be made more apparent by the following description, which addresses an embodiment of the invention in greater detail, with reference to the accompanying drawings. The features disclosed in the drawings, the description, and the claims in combination will be individually considered, as appropriate, and combined into other appropriate combinations by a person skilled in the art. In the schematic drawings, 
           [0053]      FIG. 1  illustrates an oil separator of a crankcase ventilation system of an internal combustion engine of a motor vehicle; 
           [0054]      FIG. 2  illustrates a longitudinal section of the oil separator from  FIG. 1  along a section line II-II therefrom; 
           [0055]      FIG. 3  illustrates a cross-section of a separation element of the oil separator from  FIGS. 1 and 2 ; 
           [0056]      FIG. 4  illustrates a detail view of the cross-section of the separation element from  FIG. 3 ; 
           [0057]      FIG. 5  illustrates a longitudinal section of the separation element from  FIGS. 3 and 4 ; and 
           [0058]      FIG. 6  illustrates a detail view of the longitudinal section of the separation element from  FIG. 5 . 
       
    
    
       [0059]    Identical components are provided with the same reference numbers in the figures. 
       DETAILED DESCRIPTION 
       [0060]      FIG. 1  illustrates a side view of oil separator  10  of a known (and not otherwise depicted) crankcase ventilation system of an internal combustion engine of a motor vehicle in a normal operational orientation. The oil separator  10  is used to separate motor oil from crankcase ventilation gas (blowby gas) and return the oil to the motor oil circuit of the internal combustion engine. The blowby gas with the entrained oil exists as an aerosol. The oil separator  10  is arranged in a crankcase ventilation line of the crankcase ventilation system. 
         [0061]    The oil separator  10  comprises a two-part openable housing  12  comprising an inlet  14  for blowby gas to be liberated from oil, and an outlet  16  for blowby gas liberated from the oil. The inlet  14  is arranged in a circumferential wall above the outlet  16  in the normal operational orientation of the oil separator  10 , as illustrated in  FIG. 1 . The inlet  14  is connected to the crankcase of the internal combustion engine via a line section (not shown) of the crankcase ventilation line. The outlet  16  is connected to an air intake conduit of the internal combustion engine via another line section (not shown) of the crankcase ventilation line. 
         [0062]    The housing  12  is further provided with an oil outlet  18  that leads downward out from the housing  12  in the normal operational orientation. The oil outlet  18  is connected to an oil return line (not shown) that leads to an oil sump of the internal combustion engine. 
         [0063]      FIG. 2  illustrates a longitudinal section of the oil separator  10  along a section line II-II from  FIG. 1 . In the housing  12 , a separation element  20  is arranged coaxially to an axis  22  so as to separate the inlet  14  from the outlet  16 . The blowby gas must flow through the separation element  20  when the oil separator  10  is being operated. 
         [0064]    In the present embodiment, the axis  22  coincides with a housing axis of the housing  12  and an element axis of the separation element  20 . For the sake of clarity, the term “axis  22 ” is consistently used hereinbelow. This is used to refer to the element axis, the housing axis, or both, as the context requires. Subsequent discussion of “radial”, “axial”, “circumferential”, “coaxial,” or the like is made with respect to the axis  22 , unless otherwise indicated. 
         [0065]    The separation element  20  illustrated in different sections and detail views in  FIGS. 3 to 6  has overall the shape of a round—in particular, circular or oval—hollow cylinder. 
         [0066]    The separation element  20  is preferably supported coaxially on a gridlike support tube  24 . The support tube  24  may, for example, in turn be fixed to the element cover  260  with an axially upper end, as illustrated in  FIG. 2 . The separation element  20  is preferably connected—for example, glued or welded—in a sealed manner to the element cover  260 . At the end thereof that faces the upper part  26 , the support tube  24  is open, so that the interior space thereof, i.e., the element interior space  28  of the separation element  20  is connected to the inlet  14 . 
         [0067]    On the axially lower end facing away from the upper part  26 , the support tube  24  and/or the element bottom  32  are preferably closed, so that the element interior space  28  is also closed there to a collecting space  30  for the separated oil. The collecting space  30  is located below the separation element  20  in the housing  12  in the normal operational position. The oil outlet  18  leads downward out from the collecting space  30 . 
         [0068]    At the lower end of the separation element  20 , which preferably faces the collecting space  30 , there is preferably also provided a disc-shaped or annular element bottom  32  that is connected in a sealed manner to the separation element  20 . The element bottom  32  extends radially outwardly and circumferentially. The element bottom  32  preferably has an approximately U-shaped profile, which is open upward to the separation element  20  and the upper part  26 . This simplifies adhesion to the separation element. The axially lower end face of the separation element  20  is located preferably within the U-shaped profile of the element bottom  32 . 
         [0069]    The separation element  20  is surrounded radially outwardly by a coaxial outflow-side outlet annular space  34 , which is delimited radially outwardly by the circumferential wall of a lower part  36  of the housing  12 . The outlet annular space  34  is located on the outflow-side post-filtration gas side of the separation element  20 . The outlet annular space  34  is fluidically connected to the outlet  16 . 
         [0070]    The separation element  20  shall be described in further detail herein below with reference to the detail views and sections from  FIGS. 3 to 6 . The separation element  20  is composed of a separation medium  38 , which is wound circumferentially in a plurality of medium layers  40 —for example, 13 medium layers  40 —into a coaxial medium winding. An inner diameter and outer diameter of the separation element  20  are, for example, approximately 47 mm and approximately 87 mm, respectively. The separation medium  38  is a glass fiber structure, which is substantially non-stretchable radially outward and radially inward in the axial direction and in the circumferential direction along the circumferential surfaces thereof. The separation medium  38  is compressible in the radial direction. A specific minimum bend radius of the separation medium  38 —which results on the one hand from the rigidity along the circumferential surfaces and on the other hand from the compressibility transverse to the circumferential surfaces—is smaller than the inner radius, i.e., half of the inner diameter of the finished medium winding, i.e., the separation element  20 . With the specific minimum bend radius, the separation medium  38  can be bent without forming kinks or bends on the radially inward circumferential surface thereof relative to the bend. 
         [0071]    The separation medium  38  is permeable to aerosol in the radial direction. The separation medium acts as a coalescence medium such that oil droplets entrained with the blowby gas are captured at the separation medium  38  and agglomerated into larger oil drops. 
         [0072]    The medium layers  40  of the separation medium  38  have a large number of channel-shaped indentations  42 , distributed circumferentially. The indentations  42  are respectively located on the radially inward circumferential surface of the corresponding medium layers  40 . With the corresponding radially opposite radially outward circumferential surface of the respective radially inward adjacent medium layer  40 , the indentations form respective channels  44  for the separated oil. 
         [0073]    The indentations  42  and thus the channels  44  may extend each axially, in particular, over the entire axial extension of the separation element  20 . However, an advantageous effect also arises if one or more discharge channels  44  extend only over a part of the axial extension of the separation element  20 . Provided that the discharge channels extend over the entire axial extension of the separation element  20 , they are each open on the upper end face thereof—which faces the element cover  260 —and on the lower end face thereof—which faces the element bottom  32 . 
         [0074]    The indentations  42  and thus the discharge channels  44  of the separation element  20  are partially alike and partially different in the cross-section thereof, i.e., the respective cross-sectional surface and shape thereof. There are regions in which some indentations  42  are distributed circumferentially uniformly. However, the indentations  42  are mostly different and non-uniformly distributed. 
         [0075]    To produce the separation element  20 , a medium web made of separation medium  38  is wound into a plurality of medium layers  40  about the support tube  24 . Due to the rigidity of the separation medium  38  in the circumferential direction and in the axial direction and the connected non-stretchability on the circumferential surfaces thereof, bends, kinks, or pleats form automatically because of the mechanical tension during the winding, the bends, kinks, and pleats extending in the axial direction and locally causing a reduction in the thickness of the medium layer. In the region of the bends, the corresponding indentations  42  are realized during the winding. Then, the radially inward circumferential surface of the separation medium  38  bends radially outward, compressing the material of the separation medium  38  between the radially inward circumferential surface and the radially outward circumferential surface. The layer thickness of the corresponding medium layers  40  is thinner in the region of the indentation  42  than in the adjacent regions. In this manner, the discharge channels  4  are formed automatically during the winding, without the need for additional tools, components, or the like. 
         [0076]    The support tube  24  with the finished separation element  20  is preferably fixed onto the element cover  260 . 
         [0077]    The upper part  26  and the lower part  36  are releasably connected to one another, so as to close off the housing  12 . For the purpose of maintenance—in particular, to replace the separation element  20 —the upper part  26  and the lower part  36  may be separated from one another, the upper part  26  thus forming a housing cover. 
         [0078]    When the internal combustion engine is operating, the blowby gas—loaded with oil—is guided out from the crankcase through the corresponding line section, via the inlet  14 , into an inlet space  46  in the upper part of the lower part  36 . The blowby gas flows from the inlet space  46  into the element interior space  28  of the separation element  20 . The flow of the blowby gas into the oil separator  10  is indicated in  FIG. 2  by bent arrows  48 . 
         [0079]    The blowby gas flows radially outwardly from radially inward through the medium layers  40  of the separation medium  38 . The blowby gas is then liberated from the oil. 
         [0080]    The blowby gas liberated from the oil arrives at the outlet annular space  34  and leaves the oil separator  10  through the outlet  16 . The oil is fed to the air intake conduit via the corresponding line section. 
         [0081]    The oil contained in the blowby gas is retained in the separation medium  38  and agglomerated into larger oil drops. The larger oil drops reach the discharge channels  44 . The oil drops then fall downward under the force of gravity, leaving the separation element  20  at the lower end face thereof that faces the element bottom  32 . The flow of oil in the separation medium  38 , the discharge channels  44 , and the housing  12  is indicated in  FIGS. 2, 5, and 6  by dashed arrows  50 . 
         [0082]    The oil reaches the collecting space  30  along the element bottom  32 . There, the oil can be discharged continuously or as needed via the oil outlet  18  and fed to the oil sump via the oil return line.