Patent Publication Number: US-2013247548-A1

Title: Particle separator having a multi-part housing, method for producing the particle separator and motor vehicle having the particle separator

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation, under 35 U.S.C. §120, of copending International Application No. PCT/EP2011/068995, filed Oct. 28, 2011, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German Patent Application DE 10 2010 051 712.7, filed Nov. 19, 2010; the prior applications are herewith incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a particle separator for the treatment of exhaust gases of an internal combustion engine, including a housing having a multi-part form. The invention can be used, in particular, for mobile internal combustion engines such as are provided, for example, in motor vehicles. The invention also relates to a method for producing the particle separator and a motor vehicle having the particle separator. 
     The exhaust gas of an internal combustion engine generally contains pollutants and solids which, specifically taking into consideration the relevant regulations for the protection of health and the environment, must be removed. With regard to the solids, it has already been proposed to filter constituents of the fuel, such as, for example, soot or unburned hydrocarbons, sulfur compounds, etc., out of the exhaust gas and then (catalytically and/or thermally and/or chemically) eliminate or convert them. It is known for that purpose to use filters which have, for example, a porous wall, on or in which the solids are retained. 
     Aside from the solids generated from the burned fuel, the exhaust gas may have entrained in it additional particles which have a different origin and which are several times larger than the solids. Internal combustion engines and the associated exhaust systems are often subject to intense vibrations during operation. That can cause particles, in particular in the form of chips, pieces of coatings and deposits and parts of exhaust-gas treatment units, to become detached and, while entrained by the exhaust-gas flow, damage downstream components as a result of the momentum of the impact. Furthermore, the particles can lead to increased abrasion in moving components in the exhaust system, in particular a turbocharger or turbocompressor, as a result of the increased friction action in sealing gaps. Additionally, exhaust systems are known which recirculate a part of the generated exhaust gas to the internal combustion engine again (AGR/EGR: exhaust-gas recirculation), in such a way that, in that case, there is likewise the risk of the internal combustion engine being exposed to such particles and thus being damaged. 
     It has now been found that, with progressive operating duration, the retained particles can cause problems. It must be taken into consideration in that case that the particles are, for example, ceramic and/or metallic and are not converted in the exhaust system. Consequently, the particles accumulate in the exhaust system, for example, in the vicinity of a particle separator, and/or impact repeatedly against the latter. Such an accumulation of particles may lead to a local and/or fluctuating pressure loss in the exhaust-gas flow, which may result in undesired (power-reducing) effects in the internal combustion engine and/or the exhaust system. Furthermore, in that case, the strain on the particle separator also increases, in such a way that the stability of the particle separator takes on an increased significance. 
     Furthermore, in the case of planar particle separators of that type, it was found that the connection of a screen layer and the housing was in part technically very complex and thus also expensive to implement. Additionally, it was also observed that, in continuous operation, the connection also became partially detached again, as a result of which, to some extent, new (metallic) particles were produced which then again posed a risk to the downstream components of the exhaust system. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the invention to provide a particle separator having a multi-part housing, a method for producing the particle separator and a motor vehicle having the particle separator, which overcome the hereinafore-mentioned disadvantages and at least partially solve the highlighted technical problems of the heretofore-known particle separators, methods and vehicles of this general type. It is sought, in particular, to specify a particle separator for the treatment of exhaust gases, in which the particle separator remains stable even under high loading by large particles and is simultaneously easy to manufacture. 
     With the foregoing and other objects in view there is provided, in accordance with the invention, a particle separator for the treatment of exhaust gases of an internal combustion engine. The particle separator comprises a housing with an inlet opening, an outlet opening a central axis, a first part with a first joining surface and a second part with a second joining surface, the first joining surface and the second joining surface corresponding to one another, and at least one metallic layer, through which exhaust gas can flow, disposed in the housing and spacing the first joining surface and the second joining surface apart from one another over the full circumference. 
     The particle separator, for the treatment of exhaust gases of an internal combustion engine according to the invention, has at least one metallic layer through which an exhaust gas can flow in a housing having an inlet opening, an outlet opening, a cross section and a central axis, wherein the at least one metallic layer has at least one undulation or corrugation which spans the cross section of the housing. 
     In this case, a particle separator refers, in particular, to a device which retains, for example, (ceramic and/or metallic) chips, splinters, lumps, etc. which have become detached from a component of the exhaust system, for example due to vibration during operation and/or due to pulsation of the exhaust-gas flow and/or due to aging. It is possible, in particular, for particles which have become detached from a ceramic or ceramically coated honeycomb body to be retained. It is also possible for less stable particles to be broken down, due to their momentum in interaction with the rigidity or inertia of the particle separator, into smaller particles which do not pose a hazard to further components disposed downstream. 
     The metallic layer through which the exhaust gas can flow is constructed specifically for the retention of the particles mentioned above. It is preferable in this case for only a (single) metallic layer to be used. The layer may, if appropriate, be formed with a plurality of plies (for example a first ply for filtering out the particles and a second ply for fixing the first ply in the housing), wherein the plies are then preferably connected to one another by brazing, welding, sintering or the like. The metallic layer thus constitutes, in particular, a (single) areal structure which (completely) spans the cross section of the housing, in such a way that a flow past the metallic layer is not possible. In this case, the metallic layer is constructed to be so robust or dimensionally stable that it can permanently withstand the conditions (in particular the contact with the particles) at the location of use in the exhaust system. 
     The metallic layer may, for example, be in the form of a perforated metal sheet, in the form of a sheet-metal grid or the like. Furthermore, the metallic layer may (preferably) be in the form of a fabric which includes wires, filaments and/or chips in a regular and/or irregular configuration with respect to one another. Scrims and mats formed from wires, filaments and/or chips may also be used. The wires, filaments and/or chips may be connected to one another, for example, by resistance welding, sintering and/or brazing. The metallic layer is, in particular, distinguished by its permeability to exhaust gases, in which case a very low pressure loss is generated. In this case, “metallic” means, in particular, an iron-containing and/or aluminum-containing metallic alloy. 
     The housing is generally a sheet-metal casing which is matched to the shape of the exhaust line. The housing may be formed from tubular material with various cross-sectional shapes: circular, oval, polygonal or other required shapes. In particular, use is made in this case of a substantially cylindrical housing which can, for example, be inserted between the adjoining parts of the exhaust line and welded thereto. 
     The exhaust gas generally flows into the housing through the inlet opening, and the exhaust gas exits again through the outlet opening. The central axis of the housing generally runs through the geometric center of area of the inlet opening and of the outlet opening. It is possible in this case, if appropriate, for the central axis to also be curved if the housing has a bend. In the case of a cylindrical embodiment, for example, the central axis forms the central axis through the central point of the circular cross section. The cross section of the housing between the inlet opening and the outlet opening is oriented perpendicular to the central axis and may have varying area sizes and/or area shapes. It is, however, preferable for the size and shape of the cross section to be uniform along the central axis, that is to say the inlet opening, cross section and outlet opening are identical in this regard. With regard to the position of the at least one metallic layer in the housing, it is preferable for the metallic layer not to extend beyond the inlet opening or the outlet opening. 
     In the present case, the housing has a multi-part form, specifically with at least two parts. The first part of the housing and the second part of the housing have joining surfaces which face toward one another (pointing in the direction of the central axis) and which correspond to one another in such a way that, when placed onto one another, they form a housing which can be mounted in an exhaust system at a suitable location. Such joining surfaces are formed, in particular, as a result of a single-piece housing undergoing a cutting process, so that the corresponding joining surfaces once formed are the direct contact surfaces of the housing. Furthermore, the joining surfaces preferably correspond in such a way that (elastic and/or plastic) deformations of the metallic layer as a result of the positioning of the housing parts relative to one another are taken into consideration so that the metallic layer bears in a (gas-)tight manner against the joining surfaces. Additionally, it is also pointed out in this case that the joining surfaces are, in particular, not formed with flanges or the like, that is to say they correspond substantially only to the material thickness of the wall of the housing. 
     The metallic layer is furthermore disposed relative to the housing or to the first part and to the second part in such a way that the first joining surface and the second joining surface are spaced apart over the full circumference. In particular, the first joining surface and the second joining surface are spaced apart uniformly over the circumference (only) by the thickness of the metallic layer. In other words, this is also intended to express that, after the assembly of the individual components, the gap between the housing parts is filled completely by the metallic layer (and any connecting media such as brazing material, etc.). Consequently, the gap has substantially the dimension of the thickness of the metallic layer. It is thus ensured that no gas-permeable gaps are formed between the metallic layer and the first part and second part of the housing. 
     In accordance with another advantageous feature of the particle separator of the invention, the first joining surface and the second joining surface do not lie in a flat plane. The “flat plane” refers, in particular, to a plane in the mathematical sense which extends through the particle separator at an angle with respect to the central axis. By contrast thereto, it is preferable for both joining surfaces to be disposed in a (multiply) curved, in particular undulating, plane transverse (that is to say, in particular, perpendicular) with respect to the central axis. This yields a likewise undulating profile of the joining surfaces in the circumferential direction, in the housing. 
     In accordance with a further advantageous feature of the particle separator of the invention, the at least one metallic layer, the first part and the second part are braced with one another by an outer housing. In this case, the metallic layer is positioned and/or fixed between the first part and the second part in the direction of the central axis by the joining surfaces of the parts. An outer housing is disposed (partially) around the first part and the second part and, while being (preferably) spaced apart from the metallic layer, is connected at the outside in each case to the first part and to the second part. The connection of the housing parts to the outer housing may be realized either by plugging-in, clamping or screwing, or cohesively, for example by welding or brazing. “Cohesive” connections are connections in which the connecting partners are held together by atomic or molecular forces. In particular, the first part and the second part and the metallic layer are connected to one another merely by frictional locking as a result of the bracing by the outer housing. In other words, this means, in particular, that the metallic layer is (merely) held or clamped between the parts of the (inner) housing (that is to say no cohesive connections are required there), wherein the retention force required for this purpose is generated by the outer housing. In this case, the outer housing is disposed at the outside in the manner of a sleeve and is connected to the respective part of the inner housing close to the inlet opening and the outlet opening (for example by using a brazed connection (hard solder) or a welded connection). In this case, the inner parts of the housing and the outer housing form a type of encircling cavity into which externally projecting partial regions of the metallic layer can extend. 
     In accordance with an added advantageous feature of the particle separator of the invention, the outer housing has a spacing in the region of the corresponding first joining surface and second joining surface, positioned relative to one another, of the housing. As a result of the spacing, the metallic layer can be positioned radially by the outer housing, for example, by abutting against the outer housing in the outwardly projecting partial regions of the metallic layer (in the event of a change of position during operation). Furthermore, in this situation, the encircling cavity and the gas-tight connection of the outer housing to the housing parts reliably prevents the escape of exhaust gas. The outer housing may likewise be part of an existing exhaust system, for example of an exhaust-gas line. 
     In accordance with an additional feature of the particle separator of the invention, the at least one metallic layer has a machined edge which is disposed at least partially outside the housing. The metallic layer is often cut out from a strip of material. In this case, cut or welded points are formed in the edge region. The cut or welded points may exhibit a changed permeability to exhaust gas and/or may have partially loose or labile constituents which could become detached during operation. It is therefore advantageous for at least such a part of a machined edge to be disposed outside the housing, in particular in the encircling cavity formed by the outer housing. The machined edge may additionally be provided with a hem (formed, for example, with an additional metal foil) and/or reinforcement device (for example additives, weld seams, etc.) in order, for example, to permanently withstand the clamping forces of the housing parts. 
     In accordance with again another advantageous feature of the particle separator of the invention, the at least one metallic layer at least partially makes contact with the outer housing. It can thereby be achieved that the metallic layer is positioned radially by the outer housing, and/or that, by punctiform heating, for example resistance spot welding, a fixed or at least securing connection can be produced between the metallic layer and the outer housing from the outside, without cumbersome mounting from the inside being necessary. 
     A nonwoven, which has wire filaments sintered with one another, is used, for example, as a metallic layer. This can preferably be described by at least one of the following features:
         diameter of the wire filaments: between 20 and 50 μm [micrometers], in particular, constructed with two different (intermixed and/or interconnected) wire filaments (for example one 20 to 25 μm; the other 38 μm to 42 μm);   mass per unit area of the nonwoven: between 350 g/mm 2  and 550 g/mm 2  [grams per square millimeter];   air permeability of the nonwoven: between 2300 and 3500 l/m 2 /s [liters per square meter and second].       

     Such a nonwoven may be used for retaining soot and/or other solids in the exhaust gas. 
     In a further advantageous embodiment of the particle separator, the at least one metallic layer is formed with openings with a width in a region of at least 0.05 mm [millimeters]. It is very particularly preferable for the metallic layer to have only openings which have at least an extent of 0.05 mm. In this case, the metallic layer preferably has a separation effect (only) for particles which are larger than the openings. It is very particularly preferable for the openings to have, at a maximum, a width of up to 0.25 mm, in particular in a range of from 0.1 to 0.2 mm. It is the intention, in particular, for the particle separator to retain particles which can damage or block subsequent components (situated downstream) of the exhaust system. At the same time, however, the largest possible openings should be provided, which therefore pose the least possible flow resistance. A (priority) conversion of solids from the combustion of the fuel (gasoline, diesel, etc.) is not of primary concern in this case. 
     With the objects of the invention in view, there is also provided a method for producing a particle separator having an outer housing, a metallic layer through which exhaust gas can flow, a first part of a housing with a first joining surface and with a first outer circumference, and a second part of a housing with a second joining surface and with a second outer circumference, and the first part and the second part corresponding to one another. The method comprises at least the following steps:
         placing the metallic layer between the first part and the second part, with the first joining surface and the second joining surface facing toward one another;   clamping the metallic layer by bringing the first part and the second part together;   pushing the outer housing over the first outer circumference of the first part and the second outer circumference of the second part; and   joining the outer housing to the first part and to the second part outside a region of the first joining surface and the second joining surface.       

     The method is suitable, in particular, for the production of the above-described particle separator with an outer housing. In this respect, all of the aspects discussed with regard thereto should likewise be considered in this case. 
     The outer housing may be formed in the manner of a bushing, a sleeve or the like as a separate, individual component which can be pushed over the first outer circumference of the first part and the second outer circumference of the second part. The outer housing may also be a portion of the exhaust line. The first part with its first joining surface and with its first outer circumference, in particular has a tubular form. The second part with its second joining surface and with its second outer circumference is manufactured, in particular, in the manner of the first part. The first outer circumference and the second outer circumference correspond in such a way that the first part and second part can be inserted in the assembled state into the outer housing. In particular, the first and the second outer circumferences are identical at least in the region of the first joining surface and of the second joining surface. The first joining surface and the second joining surface preferably also correspond in such a way that the metallic layer spaces the first part and the second part apart from one another in such a way that they can be inserted into the outer housing. In this case, the joining surfaces may form different, also uneven, surfaces which correspond to one another in such a way that they can be placed onto one another (for example also in the sense of a form-locking connection; form-locking connections arise as a result of the engagement of at least two connecting partners into one another, in such a way that the connecting partners do not become detached even without a transmission of force or when a transmission of force is interrupted). It must, however, be taken into consideration in this case that a thickness of a metallic layer is subtracted from the joining surfaces or from one of the joining surfaces. 
     The particle separator is already set into its final shape as a result of the configuration of the metallic layer between the first part and the second part. It should be noted in this case that the configuration of the metallic layer between the first part and the second part may also be performed after the outer housing is pushed onto and/or joined to one of the parts. 
     The metallic layer is fixedly locked in place as a result of its being clamped. In particular, the metallic layer is adequately secured in such a way that it can adequately withstand the forces resulting from the pulsating exhaust gas and any entrained particles. It should, however, be noted that the strength of the metallic layer may also first be generated by additional retention devices. Such retention devices may, for example, be weld spots, weld seams, brazed points, brazed seams, adhesive or rivets and the like. It should be noted in this case, too, that the clamping of the metallic layer may also first be performed after the outer housing is pushed onto and/or joined to one of the parts. 
     Since the outer housing is pushed over the first outer circumference and the second outer circumference, it is possible both for the outer housing to be pushed over the first and second parts (in any desired sequence) and also for the first and second parts to be pushed (for example sequentially) (in any desired sequence) into the outer housing. The first part and the second part may be pushed into the outer housing either in succession or simultaneously. In this case, the metallic layer may already be disposed there or may first be disposed between the first part and the second part during the sequential pushing-on process. 
     Various joining processes may be used for the joining of the outer housing to the first part and/or the second part. The parts may be conically clamped, pushed with a clearance fit against a stop, shrunk on, cohesively connected to one another, screwed in or clipped in. The outer housing is preferably joined to the parts from the outside by resistance-welded weld spots. The weld spots may also serve merely as a securing device in addition to one of the above-mentioned joining processes. The region of the first joining surface and of the second joining surface is disposed so as to prevent any influence being exerted on the joining process by deformation, thermal distortion or contact of other components with the metallic layer. In particular, the region is selected to be so broad that the metallic layer can be disposed in the outer housing without deformation. 
     In one refinement of the method, the metallic layer is guided into a pre-determined position by a spacing of the outer housing from the first part and from the second part in the region. It is advantageously the case that the metallic layer projects beyond the outer circumference of the first part and the second part and need not be positioned exactly during the preliminary configuration between the first part and the second part. The metallic layer is radially positioned and/or oriented as a result of the outer housing being pushed on and by using the spacing of the outer housing in the region of the first joining surface and of the second joining surface. The spacing may, however, also be selected in such a way that no contact can occur between the metallic layer and the outer housing. Any influence exerted, for example, by deformation of the outer housing is thereby eliminated. In this case, the guidance into a predetermined position by the spacing of the housing from the first part and from the second part should be understood to mean that the technician is assisted in attaining the exact positioning by a (uniform) cavity between the edge of the metallic layer and the outer housing. 
     In accordance with another advantageous mode of the method of the invention, the first part and the second part are manufactured from one piece by using a cutting process. In order to obtain a first part and a second part with a first joining surface and an exactly corresponding second joining surface in a simple, fast and inexpensive manner, the first part and the second part may initially be formed in one piece. One of the following processes: sawing; milling; thermal and mechanical cutting processes; laser cutting, is used, in particular, as a cutting process. Cutting processes, which do not necessitate further finish machining, in particular laser cutting, are preferably used. 
     With the objects of the invention in view, there is furthermore provided a method for producing a particle separator which has a metallic layer through which exhaust gas can flow, a first part of a housing with a first joining surface, and a second part of a housing with a second joining surface. The method comprises at least the following steps:
         providing a housing;   splitting the housing into a first part and a second part in such a way that a non-rectilinearly running first joining surface and a corresponding second joining surface are formed;   placing the at least one metallic layer between the first joining surface and the second joining surface; and   fixing the first joining surface and the second joining surface to one another in such a way that the metallic layer is held therebetween.       

     The method relates, in particular, to the production of a variant of the particle separator described herein according to the invention. Independently thereof, reference may also be made, for explanation of the method steps, to the other explanations in conjunction with the particle separator and/or the method described above. Laser cutting is preferably used for the splitting or dividing of the housing, specifically with regard to the complex profile of the joining surfaces for forming the undulation or corrugation of the metallic layer. The fixing of the metallic layer between the housing parts may in turn be realized cohesively (by brazing, welding, etc.). 
     With the objects of the invention in view, there is concomitantly provided a motor vehicle, comprising a configuration for the treatment of exhaust gases of an internal combustion engine with at least one exhaust-gas line, having an exhaust-gas recirculation system, wherein a particle separator according to the invention is provided in the exhaust-gas recirculation system. 
     Moving parts are provided in an internal combustion engine and in the exhaust system. In particular, the cylinder and piston of the internal combustion engine and the compressor blades of a turbocompressor are reliant on their effecting a good sealing action despite high thermal loading. Sharp-edged ceramic parts can specifically cause severe damage to turbocompressor blades and piston sealing rings. It is now proposed herein, in particular, that the particle separator according to the invention be disposed downstream of a ceramic honeycomb body and/or a ceramically coated honeycomb body, in particular in (that is to say including “directly at”) the exhaust-gas recirculation line upstream of a turbocompressor. Due to the particle separator, the adverse effect of the increase in flow resistance is practically permanently negligible. Furthermore, the particle separator can, due to its adaptable structural extent and flexibility, be used in a very flexible manner, in particular in regions of the exhaust line which have heretofore remained unutilized for structural reasons. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims, noting that the features specified individually in the dependent claims may be combined with one another in any desired technologically expedient manner and form further embodiments of the invention. 
     Although the invention is illustrated and described herein as embodied in a particle separator having a multi-part housing, a method for producing the particle separator and a motor vehicle having the particle separator, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  is a diagrammatic, longitudinal-sectional view of a particle separator with a clamped metallic layer and an outer housing; 
         FIG. 2  is a perspective view of a particle separator with a metallic layer in an inclined configuration; 
         FIG. 3  is a side-elevational view of a particle separator with non-flat joining surfaces; 
         FIG. 4  is a side-elevational view of a particle separator before clamping of the metallic layer between a first joining surface and a second joining surface; 
         FIG. 5  is a perspective view of a metallic layer with two plies; 
         FIG. 6  is a plan view of a particle separator; and 
         FIG. 7  is a block diagram of a motor vehicle having a particle separator in an exhaust system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the figures of the drawings in detail and first, particularly, to  FIG. 1  thereof, there is seen a particle separator  1  in an assembled state in which a metallic layer  3  is disposed between a first part  8  with a first joining surface  10  and a second part  9  with a second joining surface  11 . The first part  8  and the second part  9  thus form a (multi-part) housing  4 . The housing  4  is situated in an outer housing  13 . An inlet opening  5  and an outlet opening  6  define a central axis  7 . In this case, the particle separator  1  may have any desired shape. The outer housing  13  and the housing  4  are spaced apart in a region  17  in the vicinity of the first joining surface  10  and the second joining surface  11  by a spacing  12 , in such a way that a machined edge  14  of the metallic layer  3  just makes contact with the outer housing  13 . In this case it is, for example, possible for cohesive connections between the outer housing  13  and the first part  8 , the second part  9  and/or the metallic layer  3  at the machined edge  14  to be provided at contact points  23 . 
       FIG. 2  shows a circular particle separator  1  in which it is possible to see an obliquely disposed metallic layer  3  through the inlet opening  5 . The oblique configuration of the metallic layer  3  in the housing  4  is predefined by the first joining surface  10  of the first part  8  and the second joining surface  11  of the second part  9 . In this case, the metallic layer  3  is illustrated as not projecting beyond a first outer circumference or periphery  15  of the first part  8  and a second outer circumference or periphery  16  of the second part  9 . 
       FIG. 3  shows the particle separator  1  in a side view, wherein again the central axis  7  is defined by the inlet opening  5  and the outlet opening  6  of the housing  4 . In this embodiment, the metallic layer  3  rests in a curved form between the joining surface  10  of the first part  8  and the joining surface  11  of the second part  9 . 
       FIG. 4  shows the first housing part  8  with the joining surface  10  and the second housing part  9  with the second joining surface  11  as well as the metallic layer  3  with the machined edge  14  before an assembly or configuration process. It is shown therein that the metallic layer  3  may initially be flat and may first be set into a predetermined position  18 , and subsequently into a desired shape, as can be seen, for example, in  FIG. 3 , as a result of a configuration between the first joining surface  10  and the second joining surface  11 . 
       FIG. 5  shows a multi-ply version of a metallic layer  3 , wherein a first ply  31  and a second ply  32  are disposed in direct areal contact with one another (shown partially therein as an exploded illustration). The first ply  31 , which is impinged upon by a flow, has openings  28  with a width  29  which is several times smaller than a width  29  of openings  28  in the subsequent second ply  32 . Therefore, (only) the first ply performs the function of particle separation, whereas the second ply  32  serves (merely) as a (rear-side) support or partial abutment for the first ply  31 . In any case, the metallic layer  3  (or in this case the first ply  31 ) has openings  28  with a width  29  which lies in a range of from 0.05 to 0.25 mm. 
       FIG. 6  shows a particle separator  1  in a plan view, wherein the metallic layer  3  is, for simplicity, shown with a structure which visually does not correspond to a corrugation or undulation.  FIG. 6  shows merely one of many possibilities for the configuration of a cross section  30  of the housing  4  or of the inlet opening  5 . It is likewise possible for the inlet opening  5  and the outlet opening  6  to have shapes which differ from one another and/or from some other cross section  30  of the housing  4 . 
       FIG. 7  shows a motor vehicle  19  which has an internal combustion engine  2 , a particle separator  1 , a turbocharger  26  and optionally an exhaust-gas purification unit  24 . An exhaust system  20  is composed of an exhaust-gas line  21  and an exhaust-gas recirculation line  22 . The displacement of the internal combustion engine  2  is supplied, on the left-hand side in the illustration, with supercharged exhaust gas, and exhaust gas flows out again on the other side in a flow direction  27 . By using the particle separator  1  in the exhaust-gas recirculation line  22 , the turbocompressor of the turbocharger  26  is protected against any relatively large particles in the exhaust system  20 . Such particles may originate, for example, from a (partially) ceramic exhaust-gas purification unit  24  through which the exhaust gas has flowed through previously. The particle separator  1  thus protects all subsequent components (disposed downstream) against relatively large particles from the internal combustion engine  2  and portions of the exhaust-gas line  21  situated upstream of the particle separator  1 . Such components are, in particular, the turbocharger  26  and/or other exhaust-gas purification units and/or coolers  25  (or heat exchangers), in particular in the exhaust-gas recirculation line  22 . The internal combustion engine  2  and the displacements thereof are thus also protected against damage by relatively large particles.  FIG. 7  shows an arbitrary technically expedient configuration of the particle separator  1  and does not constitute any limitation with regard to the exact configuration of the particle separator  1 . 
     The invention thus at least partially solves the technical problems highlighted in conjunction with the prior art.