DE202007002429U1 - Diesel particulate filter with a ceramic filter body - Google Patents

Abstract

diesel particulate Filter comprising a ceramic filter body (1) of a Ceramic material (6) for filtering an exhaust gas flow (2) of a Diesel engine, wherein the filter body (1) gas channels (18, 18 ') with flat and porous filter sections (3), which for flow through the exhaust gas stream (2) provided transversely to the surface of the filter sections (3) are characterized in that the filter body (1) made of ceramic impregnated fiber webs (4), in particular Paper is formed by sintering under such temperature Fibers (5) of the fiber material are burned free, and that the ceramic material (6) forming the consistent between its two Surfaces (7, 8) porous and gas permeable Filter section (3) is sintered together, wherein the fiber webs (4) for forming the filter body (1) in multiple layers to a stack (39) stacked and offset mutually arranged contact surfaces (40) with each other and wherein the stack (39) for forming the gas channels (18, 18 ') is expanded to a honeycomb cross-section.

Description

Technical area

The The invention relates to a diesel particulate filter with a ceramic Filter body for filtering an exhaust gas flow of a diesel engine, wherein the filter body areal and porous Filter sections which, to flow through with the Exhaust stream provided transversely to the surface of the filter sections are.

State of the art

From the DE 35 01 182 A1 is known an exhaust filter for diesel engines. The ceramic filter bodies disclosed there have layered, flat and porous filter sections, between which gas channels are formed. The gas channels are mutually closed. A stream of exhaust gas flowing in on one side into the gas passages open to it is forced by the sealing plugs to flow through the porous filter sections transversely to their surface. The exhaust ducts located on the opposite side are open in the outflow direction and release the filtered exhaust gas flow.

to Production of the ceramic filter body shown there no information is provided. Geometrically comparable bodies, as they are known for example from catalytic converters are by Extruding made. This requires a lot of tooling for the shaping. The degrees of freedom in the shaping the filter body and in particular special filter sections as well as the gas channels is limited by the extrusion process. A flow-optimized design of the diesel particulate filter is difficult.

Of the Invention is based on the object, a generic Further develop diesel particulate filter such that with little effort an improved shape is possible.

These Task is by a diesel particulate filter with the features of claim 1.

Disclosure of the invention

It becomes a diesel particulate filter with a ceramic filter body proposed from a ceramic material, wherein the filter body of ceramic impregnated fiber webs, in particular of Paper is formed so under temperature by sintering that Fibers of the fiber material are burned free. The ceramic material is under education of consistently between its two Surfaces porous and gas permeable Filter section sintered together. The fibrous webs are used to form the Filter body in several layers to a stack on top of each other layered and staggered contact surfaces connected with each other. The stack is too close to forming the gas channels expanded honeycomb cross-section. The use of ceramic impregnated fiber webs allows improved shaping. Level ceramic impregnated fiber webs are low Expense stacked on top of each other and thereby stripwise glued together. After a subsequent expansion in the stacking direction arises in a simple way a cross section with honeycombed gas channels. Im impregnated, but not yet sintered state, the fiber webs keep the above described filter base in shape. The dimensional stability In this state, even complex shapes with thin ones are enough Channel cross sections and thin wall thicknesses produce. During the sintering process, the fibers of the fiber webs burn free and produce the desired continuous porosity the filter sections. Compared to a previously known extrusion process can be thinner wall thicknesses and almost any Produce channel cross-sections or cross-sectional profiles. Based on the same inflow cross section a lot more single channels are provided become. The pore size can be different Fiber materials or ceramic impregnations set become. With reference to the desired filtration effect the present invention carried out diesel particulate filter a significantly lower pressure drop in the flow on.

Prefers adjacent gas channels are mutually on an inflow side and a discharge side closed. The closed on the outflow side Gas channels represent input side gas channels, while closed by the on the input side Gas channels output side gas channels are formed. The mutual closing stops when flowing a Aufstauwirkung ago, the incoming exhaust gas to it forces to pass through the porous filter sections. The On the input side closed, open to the output gas channels provide a precisely defined discharge of the filtered exhaust gas safely.

The closing of the gas channels, for example, by pressing the corrugated fiber webs at a suitable location, possibly supported by a glue, done. In a preferred development, closure plugs made of ceramic material are provided for closing off the gas channels, the sealing plugs and the fiber web being sintered together in particular to form a monolithic body. From the ceramic impregnated fiber material can be very small channel cross-sections produce, as a result, only very small sealing plug are required. The result is a uniform material filter body. Waiving additional fastening materials for The sealing plugs may be exposed to high temperature loads on the filter while avoiding thermal cracking.

It may be appropriate, a honeycomb shape such to choose that gas channels with over theirs Run length of constant flow cross sections arise. The cross section of the inlet and outlet side gas channels from the inflow side to the outflow side therefore constant. Notwithstanding previously known extruded filter bodies allows the use of ceramic impregnated fiber webs but in particular the formation of gas channels with variable Cross-sections. Advantageously, the cross section of the input side narrows Gas channels from the inflow side to the outflow side out. The cross-section expands expediently the output side gas channels from the inflow side towards the outflow side. Especially with a linear change Cross-section progress along the barrel length the gas channels an at least approximately constant Flow rate and an at least approximately constant Pressure drop at the filter sections. The filtration load the individual filter sections is over their entire surface at least approximately constant. The flow resistance is reduced. Maintenance intervals or intervals between free-burn cycles are extended.

In a preferred embodiment, the gas channels in the stacking direction a constant height. this makes possible it, from the layered and mutually banded connected Semifinished by expansion in the stacking direction a filter blank to draw in block form, the block height in the direction of flow is constant. Stand on the inflow side and on the outflow side in each case the same total cross-sections are available, which leads to Minimization of the flow resistance and thus associated pressure drop contributes.

Out the honeycomb shape results in a hexagonal channel cross-section. From this and from the alternating, adjacent arrangement of on and off output-side gas channels results that not only Input and output side gas channels directly next to each other lie. Rather, are also input side gas channels and output side gas channels in pairs next to each other. Especially in the border area between two similar neighboring ones Gas ducts may be appropriate, gas impermeable Provide areas for gas exchange between these channels to avoid.

In expedient development has at least one Fiber web unimpregnated sections to form openings in the filter body. The unimpregnated sections the fibrous web burn during the sintering process. Due to the absence of a ceramic Impregnation remain at this point openings, for example, an unimpeded gas exchange between two Allow adjacent gas channels. this makes possible it, z. B. in the inlet or outflow before or after the adjacent stopper the flow cross-section all gas channels for example for to use a catalytic exhaust treatment.

Brief description of the drawings

embodiments The invention are described below with reference to the drawing described. Show it:

1 a schematic perspective view of a ceramic filter body according to the invention of ceramic impregnated, expanded into a honeycomb structure and sintered fiber webs for use in a diesel particulate filter,

2 a schematic representation of a stack of ceramic impregnated fiber webs prior to expansion to a honeycomb structure,

3 a variant of the arrangement according to 1 with cross-sectionally linearly variable gas channels,

4 a schematic longitudinal sectional view of two adjacent gas channels with an intermediate opening for an unimpeded gas exchange,

5 a schematic representation of a rolling plant for impregnating fiber webs with ceramic material,

6 a schematic representation of a doctor blade system for impregnating fiber webs with ceramic material,

7 a schematic perspective view of a with the arrangement according to 4 or 5 partially impregnated, cut-out fibrous web.

Embodiment (s) of the invention

1 shows a schematic, partially sectioned perspective view of a ceramic filter body according to the invention 1 , The filter body 1 is part of a diesel particulate filter, not shown, and for filtering an exhaust stream 2 a diesel engine provided. The filter body 1 is through related with the below 5 to 7 described in more detail, ceramic impregnated fiber webs 4 educated. The fiber webs 4 are as shown below 2 to a semi-finished product 17 joined, which to the block-shaped filter body 1 expanded with a honeycomb structure.

To 2 is a variety of ceramic impregnated fiber webs 4 in a stacking direction 41 to a pile 39 layered. These can be individual cut pieces of fibrous web 4 to 7 to get voted. It may also be appropriate to have a continuous fiber web 4 to fold and zigzag to a pile 39 to lay. The layered fiber webs 4 are at staggered contact surfaces 40 connected with each other. These are glue strips 43 . 43 ' made of ceramic glue. The top two fiber webs 4 are with glue strips 43 interconnected, wherein the glue strips are narrower than a respective distance between them. In the illustrated embodiment, the distance between two glue strips 43 about three times the width of a glue strip 43 , The fibrous web directly underneath 4 is with the overlying fiber web 4 with glue strips 43 ' connected. These glue strips 43 ' lie opposite the glue strips arranged above and below 43 offset so that they are exactly in the middle between the glue strips 43 are arranged. In width and distance to each other, the glue strips 43 ' with the glue strips 43 match. The above-described mutual arrangement of the glue strips 43 . 43 ' continues through the entire pile 39 continued. After gluing the fiber webs 4 becomes the stack formed from it 39 in the stacking direction 41 according to arrows 44 expanded, as a result, the blank of the filter body 1 to 1 arises. The width of the glue strips 43 . 43 ' and their distances from each other are chosen such that when expanding a honeycomb structure with gas channels 18 . 18 ' arises, with the gas channels 18 . 18 ' Have cross sections in the form of an equilateral hexagon. The expansion is carried out so far that the hexagonal cross sections are also approximately equiangular.

Referring again to 1 is a flow through the filter body 1 from the exhaust gas flow 2 in a longitudinal direction 38 of the filter body 1 from an inflow side 33 to a discharge side 34 intended. By the expansion of the fiber webs 4 ( 2 ) creates a plurality of at least approximately axially parallel gas channels 18 . 18 ' with along the longitudinal direction 38 more constant, in the stacking direction 41 measured height. In the cross-sectional plane of the filter body 1 diagonal to the stacking direction 41 are alternately a gas channel 18 and a gas channel 18 ' intended. The gas channels 18 are to the inflow side 33 open towards and in the opposite direction to the outflow side 34 towards by means of sealing plugs 22 locked. Related to the aforementioned diagonal direction lies between two gas channels 18 one gas channel each 18 ' , to the inflow side 33 towards by means of a sealing plug 22 ' closed and to the outflow side 34 is open. During operation, the exhaust gas stream flows 2 according to an arrow 23 parallel to the axis to the inflow side 33 open gas channels 18 one. Sidewalls of the through the expanded stack 39 ( 2 ) produced ceramic structure form flat and porous filter sections 3 , The at the stopper 22 pent-up exhaust gas flow 2 becomes in diagonal direction according to arrows 24 deflected and flows through the porous ceramic filter sections 3 across to its surface. According to the arrows 24 occurs the exhaust stream 2 through the filter sections 3 through into the outlet side 34 open channels 18 ' and pour out of them according to arrows 25 out. When passing through the porous filter sections 3 becomes the exhaust gas flow 2 cleaned by entrained soot particles or the like.

For certain applications, it may be useful in the through the fiber webs 4 formed filter area openings 13 whose production is described below. The schematic longitudinal section after 4 it can be seen that such an opening 13 for example, upstream of a sealing plug 22 ' is arranged. The input side gas channel 18 is consistently on the stopper 22 ' past. The adjacent adjacent channel structure is through the sealing plug 22 ' in the output side gas channel 18 ' and an input side channel section 18 '' divided up. The exhaust gas flow 2 ( 1 ) can be upstream of the sealing plug 22 ' taking advantage of the flow cross-section of the gas channels 18 and the channel sections 18 '' in the filter body 1 flow. In this area, for example, a catalytic coating can be provided by utilizing the entire flow cross-section. Upstream of the sealing plug 22 ' the exhaust gas is corresponding to an arrow 23 '' through the opening 13 in the input side gas channel 18 diverted. There he unites with the gas flow after arrow 23 , resulting in the filtration function described above. Similarly, openings can also be used 13 downstream of the stopper 22 ( 1 ) be provided.

Another advantageous possibility is, in addition to the in 1 shown flow along the arrows 24 also a flow through the contact surfaces 40 permit. In this case, the in 2 shown glue strips 43 designed porous and form flowed through filter sections.

In 3 is another embodiment of the filter body 1 to 1 shown. Deviating from the illustration according to 1 in which the gas channels 18 . 18 ' along the longitudinal direction 38 have a constant cross-section, narrow the cross sections of the input side gas channels 18 from the inflow side 33 to the outflow side 34 out. Conversely, the cross sections of the output-side gas channels expand 18 ' from the inflow side 33 to the outflow side 34 but with all gas channels 18 . 18 ' the channel height remains constant. This is achieved by a trapezoidal shape of the contact surfaces 40 with at the inflow side 33 wide and on the outflow side 34 narrow strips of glue 43 , Conversely, the glue strips 43 ' on the inflow side 33 narrow and on the outflow side 34 wide. In the embodiment shown, the width of the glue strips changed 43 . 43 ' from the inflow side 33 to the outflow side 34 towards linear, with the glue strips 43 ' wider by the same amount as the strips of glue 43 become narrower. As a result of the constant channel height, the cross-sectional profile is also approximately linear. But it can also be a deviant, non-linear course appropriate.

The along arrows 23 in the gas channels 18 incoming exhaust gas flow 2 ( 1 ) penetrates along the entire run length of the gas channels 18 . 18 ' through the filter sections 3 according to arrows 24 therethrough. This reduces the input-side volume flow 23 in the gas channel 18 along its run length, while the output side volume flow 25 in the gas channel 18 ' enlarged along the length of its run. The above related to 3 described cross section of the gas channels 18 . 18 ' causes the flow velocity within the gas channels 18 . 18 ' as well as the over the filter sections 3 measured pressure difference between the gas channels 18 . 18 ' along the run length of which are at least approximately constant. The Filtrierbelastung the filter sections 3 is thereby along the run length of the gas channels 18 . 18 ' at least approximately constant.

Further differences in the arrangement 3 to the exemplary embodiment 1 still exist in that the sealing plug 22 . 22 ' in the stacking direction 41 are arranged one above the other, wherein side by side alternately gas channels 18 . 18 ' are arranged. In addition, the fiber webs 4 exemplary in the area of contact surfaces 40 gas impermeable. This can be done by a suitable partial ceramic impregnation or by a suitable design of the glue strips 43 . 43 ' be achieved. In the remaining features and reference numerals, the embodiment agrees 3 with the one after 1 match.

5 shows a schematic representation of a device for ceramic impregnation of the fiber web according to the invention 4 , Two feed rollers 30 . 31 The device are arranged axially parallel to each other and are flush with each other. They rotate in opposite directions, with a ceramic material in a wedge-shaped gap above their contact line 6 is stored. The ceramic material 6 may be a dry powder of finely ground ceramics, which is used for dry impregnation of the fiber web 4 is provided. In the embodiment shown is with the ceramic material 6 an aqueous emulsion 9 produced. Instead of water, another suitable liq fluid or a liquid mixture may be appropriate. Another roller 10 is axially parallel to the feed roller 30 arranged and touches them along a Berührlinie. The feed roller 30 carries as a result of their rotation indicated by an arrow the ceramic emulsion 9 to the roller 10 and roll the ceramic emulsion 9 on the surface of the roller 10 on. By means of the roller 10 becomes the ceramic material 6 in the material of the below in the direction of an arrow 28 along guided fiber web 4 rolled. For this lies the roller 10 with contact pressure on the fiber web 4 on. It will be a watering of the fiber web 4 with the emulsion 9 carried out. The flat, permeable fiber web 4 takes the finely ground ceramic material 6 within their entire cross section.

Another possibility for a ceramic impregnation of the fiber web 4 is in 6 shown. The raw fiber web 4 will be in the direction of an arrow 27 fed to the device shown and runs around a pressure roller 29 around. Related to the arrow 27 specified direction of movement is in front of the pressure roller 29 a sieve 15 on the fiber web 4 on. Above the screen 15 is also an aqueous emulsion on this 9 with the ceramic material 6 stored. The emulsion 9 is done by means of a squeegee 11 under pressure through the sieve into the material of the fibrous web 4 scrape into it, thereby impregnating the fiber web 4 with the emulsion 9 he follows. Alternatively, a dry impregnation of the fiber web 4 with the ceramic material 6 respectively.

From the after 5 or 6 produced fiber webs 4 becomes the semi-finished product 17 as shown 2 formed and expanded. Furthermore, the formation of the sealing plug 22 . 22 ' a ceramic mass at a suitable location in the gas channels 18 . 18 ' brought in. The filter blank formed in this way is sintered after a drying process in a sintering furnace under the action of temperature, wherein the ceramic material 6 together with the ceramic mass of the sealing plugs 22 . 22 ' is sintered together to a monolithic ceramic body. At the high sintering temperature, the material burns the fiber webs 4 . 4 ' , whereby the ceramic material 6 becomes porous. The porosity is designed such that the exhaust gas flow 2 ( 1 ) across the surface of the ceramic filter sections 3 can flow through them.

7 shows in perspective schematic representation of the endless fiber web 4 , The fiber web 4 is made of fibers 5 educated. For this purpose, a felt, a textile fabric or knitted fabric may be provided. Preferably, an open, permeable filter paper is selected. The fiber web 4 is flat and permeable in the sense that the finely ground ceramic material 6 ( 5 . 6 ) between fibers 5 the fiber web 4 can penetrate. The permeability of the fiber web 4 and the impregnation process according to the 5 or 6 are coordinated so that a part of the fibers 5 after impregnation with the ceramic material 6 ( 5 . 6 ) on both opposite surfaces 7 . 8th the fiber web 4 lie free. This leads to the burning of the fibers 5 during the sintering process, that the sintered ceramic filter section 3 consistently from a surface 7 to the opposite surface 8th porous and thus transversely to the surface of the filter section 3 gas permeable to the exhaust gas flow 2 ( 1 ).

For certain applications, it may be expedient to bring about gas tightness at least in sections. For example, the filter body 1 ( 3 ) in the area of the contact surfaces 40 be gas impermeable, while a gas permeability is desired only in the remaining areas. In this case, in addition to the soaking impregnation of the fiber web 4 also in sections a closed surface coating with the ceramic material 6 ( 5 ) on at least one of the two surfaces 7 . 8th without the fibers there 5 exposed. In this case, during sintering, a closed ceramic body is produced, which is in the area of the surface 7 . 8th non-porous and therefore not gas-permeable.

It may be convenient to the fiber web 4 as uncircumcised endless material over the entire surface with the ceramic material 6 ( 5 . 6 ) to impregnate. In the illustrated embodiment according to 7 are not impregnated sections 12 intended. Part of the non-impregnated sections 12 becomes the later formation of the openings 13 ( 4 ) excluded from the impregnation. Another unimpregnated section 12 is by a border area 26 formed, which is a limited area 36 surrounds. The limited plane 36 has the contour that is used to stack the semifinished product 17 to 2 is required. The fabric 36 is by trimming the fiber web 4 in particular by punching out the peripheral contour of the fabric 36 as well as by punching out the cutouts 16 produced. It may also be appropriate to punch out the cutouts 16 to dispense and only the associated sections 12 from the impregnation with the ceramic material 6 ( 2 ). This is done in more detail below. During the sintering process, the unimpregnated sections then burn 12 completely and leave the openings 13 ( 4 ).

The representation after 5 it can be seen that the roller 10 a surface structuring 14 having. This corresponds in shape to the contour of the fabric 36 to 7 , The ceramic emulsion 9 is only through the raised surfaces of the surface structuring 14 in the fiber web 4 rolled. In intermediate areas of the surface structuring set back in the radial direction 14 can not impregnate with the ceramic material 6 done so that the fiber web 4 to 7 only partially and to form the non-impregnated sections 12 with the ceramic material 6 is impregnated.

An alternative way of producing non-impregnated sections 12 in the fiber web 4 follows from the illustration below 6 in the area of the screen 15 , The sieve 15 is similar to screen printing with schematically indicated covers 35 Mistake. The covers 35 correspond in shape to the shape of the non-impregnated sections 12 to 7 , When brushing the ceramic emulsion 9 by means of the squeegee 11 prevent the covers 35 partially an impregnation and form the non-impregnated sections 12 ,

In the embodiments shown, an impregnation of the fiber webs takes place first 4 with the ceramic material 6 ( 5 . 6 ) and then the assembly to the semi-finished product 17 ( 2 ) and expanding to the blank of the filter body 1 to 1 or 3 , This blank is then dried and finally sintered. It may also be appropriate to the blank of the filter body 1 first of unimpregnated fiber webs 4 to shape and then, for example, in a dip with the ceramic material 6 ( 5 . 6 ) to soak. This is followed by a drying process and finally the sintering process.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 3501182 A1 [0002]

Claims (10)

Diesel particulate filter comprising a ceramic filter body ( 1 ) made of a ceramic material ( 6 ) for filtering an exhaust gas stream ( 2 ) of a diesel engine, wherein the filter body ( 1 ) Gas channels ( 18 . 18 ' ) with flat and porous filter sections ( 3 ) which, for the flow through the exhaust gas flow ( 2 ) across the surface of the filter sections ( 3 ) Are provided, characterized in that the filter body ( 1 ) made of ceramic impregnated fiber webs ( 4 ), in particular paper is formed by sintering at such temperature that fibers ( 5 ) of the fiber material are baked, and that the ceramic material ( 6 ) forming the continuous between its two surfaces ( 7 . 8th ) porous and gas-permeable filter section ( 3 ) is sintered together, wherein the fibrous webs ( 4 ) for forming the filter body ( 1 ) in several layers to a stack ( 39 ) stacked on top of each other and at mutually offset contact surfaces ( 40 ) and the stack ( 39 ) for forming the gas channels ( 18 . 18 ' ) is expanded to a honeycomb cross-section. Diesel particulate filter according to claim 1, characterized in that adjacent gas channels ( 18 . 18 ' ) alternately on an inflow side ( 33 ) and on a downstream side ( 34 ) are closed. Diesel particulate filter according to claim 2, characterized in that for firing the gas channels ( 18 . 18 ' ) Sealing plugs ( 22 . 22 ' ) are provided of ceramic material. Diesel particulate filter according to claim 3, characterized in that the sealing plugs ( 22 . 22 ' ) and the fiber web ( 4 ) to a monolithic filter body ( 1 ) are sintered together. Diesel particulate filter according to one of claims 1 to 4, characterized in that the cross section of the input-side gas channels ( 18 ) from the inflow side ( 33 ) to the outflow side ( 34 ) narrowed. Diesel particulate filter according to one of claims 1 to 5, characterized in that the cross-section of the outlet-side gas channels ( 18 ' ) from the inflow side ( 33 ) to the outflow side ( 34 ) extended. Diesel particulate filter according to one of claims 1 to 4, characterized in that the cross section of the inlet and outlet side gas channels ( 18 . 18 ' ) from the inflow side ( 33 ) to the outflow side ( 34 ) is constant. Diesel particulate filter according to one of claims 1 to 7, characterized in that the gas channels ( 18 . 18 ' ) relative to a stacking direction ( 41 ) have a constant height. Diesel particulate filter according to one of claims 1 to 8, characterized in that gas impermeable areas ( 42 ) of fibrous webs ( 4 ) are provided. Diesel particulate filter according to one of claims 1 to 10, characterized in that at least one fibrous web ( 4 . 4 ' ) unimpregnated sections ( 12 ) for the formation of openings ( 13 ) in the filter body ( 1 ) having.