DE4243500A1 - Catalyst insert, esp. for cleaning engine exhaust gases - Google Patents

Abstract

New catalyst insert, especially for engine exhaust gas cleaning, is wound from essentially flat twisted or woven wire ropes (9,10) made up of wires which have been coated with a catalytically active material (wash-coat). The novel feature is that after winding, the wires or wire ropes are thermally and/or mechanically fixed to each other.Also claimed is an exhaust gas catalyser using this insert. A third claim covers a method for forming the insert consisting of twisting or weaving the wire ropes, winding them to form the insert shape (27), thermally and/or mechanically fixing the wires to each other, and applying a catalytically active coating.

Description

The invention relates to a catalyst insert, in particular for a Catalyst for cleaning internal combustion engine exhaust gases after the upper Concept of claim 1. Furthermore, the invention relates to a such a catalyst and a process for Production of such a catalyst insert.

The use of wire mesh or fabric layers for catalytic us kending uses of catalysts, such as in vehicles used with gasoline engines to purify the exhaust is off EP 0 325 111 A2 known. The filter and post-combustion shown there Device for exhaust gases, in particular from internal combustion engines, consists of a spiral bobbin, which by winding a substantially flat wire mesh layer with these flanking edging jackets in Form of metal knitted ribbons and using spacers is formed. Both the edging coats and the wire knitla gene can be provided with a catalytic coating. Special Measures for compacting and fixing the winding body in itself cannot be found in this publication.

DE 39 08 581 A1 describes a catalyst body made of multilayer Me tall woven or knitted, which are sintered together. By powdery or granular particles that are on the individual layers or whose wires are sintered on, the separation effect of the Kataly be increased.

From DE 41 09 227 A1 it is very generally known to have a catalytic converter to form the gate body from multi-layer metal mesh or knitted fabric where is soldered to such a fabric or knitted fabric. Details on the soldering process is not done.

The invention is based, to use a catalyst Generic type so that it is particularly simple adjustable, mechanically particularly stable and efficient.

In terms of device technology, this task is carried out by the Characteristic part of claim 1 specified features solved. Correspond Appropriate solution features in terms of process technology are in the Kenn Drawing part of claim 13 specified.

Through the intended thermal and / or mechanical fixation of the Wires and / or wire mesh or fabric layers in the wound state the structure of the insert is stabilized so that it can be used for its further use Treatment - e.g. B. for the application of a catalytically active Surface coating - or use - e.g. B. for the further auto Matic or manual handling in the production of an exhaust gas catalyzer sators - is particularly suitable. Basically, the Wire structure of the use is advantageous because a targeted swirling of the Exhaust gas flow and thus an optimal dwell time or conversion rate for the exhaust gases at low exhaust gas back pressure. In addition, it is completely made of metallic wire material Tigt catalyst use according to the invention compared to catalyst on sentences z. B. made of ceramic material far less sensitive to Be damage and particularly easy to recycle. By fixing the Wires and layers to each other is further avoided that the wires rub against each other and thus the catalytically effective coating solves.

By the provided according to claim 2 solder connections between the Contact points of the wires within the individual layers and between The layers are mechanically mechanically used bilized so that it as a self-supporting whole no further stops structures needed. In this respect, the use according to the invention is also particularly suitable for use in motor vehicles, where it is particularly is strongly exposed to shocks, vibrations and the like.

Claim 3 indicates an alternative for the thermal fixation of the Wires or wire layers in the form of a weld, e.g. B. a laser  or electron beam welding. This welding can, for. B. select be made during the winding of the winding body.

By the so-called "wash-coat coating" provided according to claim 4 tung "with a catalytically active surface coating, for example a platinum-rhodium alloy becomes the catalytic one Surface area of the wires increased significantly, creating the catalyst effect is optimized. "Wash-coat coatings" are basically from the Known in the art and therefore do not require any further details Explanation. It is only necessary to add that the wash-coat coating tion from aluminum oxides and so-called promoters - i.e. additive fen, which increase the catalytic effect of the precious metals - exist. The precious metals - e.g. B. Platinum, Rho dium and / or palladium - fixed as the actual catalyst substances.

Claim 5 characterizes an advantageous embodiment of the winding layers. By combining a flat lay with an in a wavy shape embossed wire mesh or fabric layer are without additional measures flow channels formed in the catalyst insert. This means that the exhaust gas routing through the catalyst insert can be Optimizing the efficiency of which can be influenced. About that In addition, the wavy embossing of a wire mesh or - Fabric layer additionally structurally reinforced. Through the im Claim 5 specified parallel direction of the generated by the embossing The wave peaks and valleys of the embossed location remain the two-layer winding was easy to wind because the direction of the wave crests and troughs is parallel runs to the winding axis.

An alternative for the arrangement of the wave peaks and valleys is in the An Say 5 also specified, after which this obliquely to the winding axis of Can run. So that exhaust gas flow channels in the Catalyst insert formed, this related to the winding axis assert helically and additionally through the Winding up the layers in relation to the radial direction of the roll remove the axis in a spiral. Relative to a fixed axial length of the In this way, the flow channels are considerably extended which further increases the efficiency of the operation.  

The measures specified in claims 6 to 9 serve a white structural reinforcement and stabilization of the catalyst sentence. Due to the pressing of the insert, this can be brought to a defined final form on the one hand and on the other hand the catalytically effective wire surface per unit volume of the insert be significantly increased. In addition, by the in claim 6 specified winding of the wire mesh or fabric layers on a Carrier tube in a particularly simple manner, the outer cross-sectional shape of the Determined. This corresponds to the cross-sectional shape of the Carrier tube and can be round, elliptical, teardrop-shaped, triangular, long oval or the like.

According to claim 10, the wires used for use are flat wire trained. Based on its volume, it offers a special one large surface so that the catalytic effect of the insert is optimized becomes.

Claim 11 characterizes a catalyst, in particular for cleaning of internal combustion engine exhaust gases, which is a housing with exhaust gas supply and exhaust line and an insert according to the invention therein.

As an advantageous embodiment of this catalyst is according to the An say 12 or 13 provided an additional thermal or mecha African fixation of the insert in the form of soldering or ver welding with the housing or with an additional support cross in the Housing. It is also possible to use one of his Determine the shape of the corresponding receptacle in the housing. So that's the Reliable use not only in itself, but also in the housing fixed.

Claim 14 gives a particularly simple manufacturing process for the catalyst insert according to the invention. Accordingly, the individual Wire mesh or fabric layers made of corresponding round or flat knitted or woven wires, these layers into a winding body wound, then the wires of the winding body thermally and / or mechanically fixed and a catalytically effective coating on the Wires applied.  

Claim 15 is a particularly simple, but very effective thermal fixing method for the catalyst according to the invention gate insert. Accordingly, they are provided with a solder layer Wires at their points of contact within and between the one individual layers are soldered by a corresponding high-temperature process and then applied a catalytically active coating on the wires brings. Alternatively, the solder layer can be before or after Knit or interweave the wires to be applied where for prior application due to coating technology reasons prefer is. After knitting or weaving such coated The winding body is thus already complete for soldering equipped so that here an intermediate production step in the manufacture the catalyst insert can be omitted.

Another alternative for thermal fixation of the wires or Wire layers is specified in claim 16, according to which these parts together welded, in particular using a laser or electron beam be welded.

According to claim 17 it is provided that a wire mesh or fabric lay in a flat state, shaped in a wave shape and with a flat surface Wire mesh or fabric layer simultaneously to a winding body with two layered winding layer is wound up.

According to claim 18 it is provided that the winding body before or after the soldering is pressed to its final shape. Of these two alterna It is preferable to use a crimp before soldering thereby holding the insert together in its compressed final shape and this due to the mutual connection of the wires in the pressing th state shows no tendency to move against the direction of the pressure expand again.

Furthermore, can be placed in the winding former for additional stabilization or stabilizing pins are driven in after soldering (claim 19). Since this is radial to the winding axis, i.e. perpendicular to the flow direction The use of exhaust gases through which the insert is to run is used against the dynamic pressure and the pulsations of the exhaust gas flowing through solidified.  

The "wash-coat coating method" specified in claim 20 is - as explained - known per se. It represents a particularly affordable measure to increase the surface area of the wires of the insert Such "wash-coat coating" can coat noble metal particularly well tungen, z. B. introduced on the basis of a platinum / rhodium alloy become.

Further features, details and advantages of the invention are according to following description can be seen in the embodiments of the Subject of the invention with reference to the accompanying drawings is tert. Show it

Fig. 1 shows a schematic longitudinal section through an exhaust gas catalyst according to the invention with a wire mesh insert,

Fig. 2 is a cross sectional view of the catalyst according to Fig. 1,

Fig. 3 is a perspective view of a winding layer of an inventive wire mesh used in the laid-flat or partially coiled state with axially parallel extending embossing,

Fig. 4 is a perspective view of a winding location for an inventive wire mesh used in the laid-flat or partially coiled state with the winding axis of oblique embossing,

Fig. 5 is a plan view of a flattened wire knit layer,

Fig. 6 is a plan view of a flattened wire fabric layer,

Fig. 7 is a perspective, partially broken away, partial view of a pre-coated with solder wire before knitting or weaving,

Fig. 8 is a schematic representation of a braze joint between two wires,

Fig. 9 is a perspective, partially broken-away fragmentary view of a wire with a wash-coat coating,

FIG. 10A-E are schematic cross sections through a pipe insert with support having thereon a wound bobbin in different cross-sectional configurations, and

Fig. 11 is a perspective, partially broken away, partial view of a catalytic converter according to FIG. 1, with additional cross-brace against the exhaust gas flow pressure.

The exhaust gas catalytic converter shown in FIGS. 1 and 2 has a cylindrical housing 1 with an exhaust gas supply line 2 and an exhaust gas discharge line 3 .

A wire mesh insert 4 is arranged concentrically in the housing 1 , where an inlet space 6 or outlet space 7 remains free in front of the front ends 5 of this insert 4 .

The wire mesh insert 4 is designed as a winding body which is wound from a two-layer winding layer 8 . This winding layer 8 consists of a flat lay flat wire mesh layer 9 and an up there positioned, embossed in a waveform of wire mesh layer 10, as is clear from FIG. 3. This two-layer winding layer 8 is spirally wound on a support tube 11 , the length of which corresponds essentially to the width of the flat or embossed wire mesh layers 9 , 10 . Contrary to the direction of flow (arrows 12 ) of the exhaust gases through the catalyst, this support tube 11 is closed and tapered. Furthermore, the embossed wire mesh layer 10 ends at the radially outer end of the winding layer 8 in front of the flat wire mesh layer 9 , which is continued to fill the housing cross-section as far as possible over a certain circumferential angle ( FIG. 2).

The diameter of the wire mesh insert 4 corresponds essentially to the inside diameter of the housing 1 , so that its cross section is essentially completely filled. The wire mesh insert 4 is soldered to the housing 1 with its outer surface.

In the winding layer 8 shown in FIG. 3 from the two wire knitting layers 9 , 10 , the embossing of the winding layer 10 and thus the wave crests 15 and valleys 16 run parallel to the winding axis 17 of the winding body pers.

In the example shown in FIG. 4, the embossments extend and there with the crests 15 and valleys 16 of the embossed wire mesh layer 10 obliquely to the winding axis 17 so that the flow channels formed by the embossed helically with respect to the axial direction and with respect to the radial direction of the bobbin Extend spirally from the winding axis.

The wires of the knitted wire fabric 9 , 10 shown individually in FIGS. 7 to 9 are wires 18 which, as shown, can be round or flat in cross section and which are provided with a solder layer 19 . In the case of a flat design, a maximum wire surface is obtained with a given wire quantity and dimension. As is clear from Fig. 8, the individual wires 18 are fixed by means of the Lötmit telschicht 19 at their contact points 20 with each other and between the individual wire mesh layers 9 , 10 by solder connections 21 to each other. As is clear from Fig. 9, the wires 18 are provided with a so-called "wash-coat coating" 22 , which in turn carries catalytically active particles of a platinum-rhodium alloy. For additional union stabilization radially arranged stabilizing pins 13 are provided which bridge the annular space between the support tube 11 and the inner surface 14 of the housing. These stabilizing pins 13 are inserted through the wall of the housing 1 and fixed thereon and on the support tube 11 ( FIG. 2).

In Fig. 5 the wire mesh layer 9 is a flat, flat web Darge provides. The wire mesh layer 9 is composed of appropriately entangled meshes 23 of wires 18 .

The layers shown in FIGS . 3 and 4 can also be made from a wire mesh layer 24 , as shown in FIG. 6. The wire fabric consists of warp wires 25 and weft wires 26 running perpendicular thereto, which are woven in the usual way.

As is clear from Fig. 10, the wire mesh insert 4 can have various external cross-sectional shapes, which are determined by the cross-sectional shape of the central support tube 11 . Thus, the insert shown in FIG. 10A is circular and the insert shown in FIG. 10B is oval. A teardrop shape ( FIG. 10C), a slot-like shape ( FIG. 10D) or a triangular shape with rounded corners ( FIG. 10E) are also conceivable. The winding body 27 made from the wire mesh layers 9 , 10 is indicated in FIGS. 10A to 10E by cross hatching.

As is clear from Fig. 11, the wire mesh insert 4 in Ge housing 1 can be additionally supported against the flow direction 12 of the exhaust gases by a support cross 28 arranged in its outlet space 7 .

The manufacture of the wire mesh insert 4 is summarized again as an example as follows:

There are first two flat wire mesh layers 9 , 10 knitted from wires 18 , which are provided with a solder layer 19 . One of the layers is then embossed into the wavy shape shown in FIG. 3 and placed on the flat wire mesh layer 9 . The winding layer 8 formed from the two wire mesh layers 9 , 10 is then wound onto the carrier tube 11 . The wound body thus formed is stabilized by the action of a correspondingly high temperature by the wires of the wire mesh layers 9, 10 are soldered at their contact points 20 within the individual layers 9 and 10 and between these sheets 9, 10 who the. Then the wash-coat coating 22 is brought up with a catalytic surface coating in the usual and known manner. The wire mesh insert 4 is inserted into the housing 1 and then fixed therein with the stabilizing pins 13 and / or by the support cross 28 and / or by welding.

Claims (20)

1. Catalyst insert, in particular for an exhaust gas catalytic converter for cleaning internal combustion engine exhaust gases, which insert (wire mesh insert 4 ) is wound from essentially flat wire mesh or fabric layers ( 9 , 10 , 24 ) which are made with a catalytically active coating (wash-coat coating 22 ) provided wires ( 18 ), characterized in that the wires ( 18 ) and / or wire mesh or fabric layers ( 9 , 10 , 24 ) in the wound state against each other thermally and / or are mechanically fixed. 2. Use according to claim 1, characterized in that the wires ( 18 ) for thermal fixation with a solder layer ( 19 ) are provided, by means of which the wires ( 18 ) at their mutual contact points ( 20 ) within the individual layers (wire mesh layers 9 , 10 ) and between the layers (wire mesh layers 9 , 10 ) are soldered together. 3. Use according to claim 1, characterized in that the wires ( 18 ) at their mutual points of contact ( 20 ) within the individual layers (wire mesh layers 9 , 10 ) and between the layers (wire knitting layers 9 , 10 ) are welded together (welding) . 4. Use according to one of claims 1 to 3, characterized in that the wires ( 18 ) of the insert (wire mesh insert 4 ) have a so-called "wash-coat coating" ( 22 ) with a catalytically active surface coating. 5. Use according to one of claims 1 to 4, characterized in that the winding layers ( 8 ) each have two layers of a flat wire mesh in the flat state ( 9 ) or -woven layer ( 24 ) and an embossed in a wavy shape in the flat state Wire mesh ( 10 ) or fabric layer exist, the crests ( 15 ) and valleys ( 16 ) of the embossed layer (wire mesh layer 9 ) parallel or oblique to the winding axis ( 17 ) of the insert (wire mesh insert 4 ). 6. Use according to one of claims 1 to 5, characterized in that the wire mesh ( 9 , 10 ) or fabric layers are wound on a support tube ( 11 ) whose cross-sectional shape determines the outer cross-sectional shape of the insert (wire mesh insert 4 ). 7. Insert according to one of claims 1 to 6, characterized in that the insert (wire mesh insert 4 ) is pressed. 8. Use according to one of claims 1 to 7, characterized in that the insert (wire mesh insert 4 ) for mechanically fixing the wires ( 18 ) and / or wire mesh or fabric layers ( 9 , 10 , 24 ) from radial to the winding axis ( 17 ) extending stabilizing pins ( 13 ) is interspersed. 9. Use according to claim 8, characterized in that the stabilization pins ( 13 ) on the support tube ( 11 ) and / or a housing ( 1 ) for use (wire mesh insert 4 ) are attached. 10. Use according to one of claims 1 to 9, characterized in that the wires ( 18 ) of the wire mesh or fabric layers ( 9 , 10 , 24 ) consist of flat wire. 11. Exhaust gas catalytic converter, in particular for cleaning internal combustion engine exhaust gases with a housing ( 1 ) with exhaust gas feed ( 2 ) and exhaust ( 3 ) and an insert (wire mesh insert 4 ) according to one of claims 1 to 11 in the housing ( 1 ). 12. Exhaust gas catalytic converter according to claim 11, characterized in that the insert (wire mesh insert 4 ) is soldered or welded to the housing ( 1 ) or in a shape corresponding to the insert (wire mesh insert 4 ) in the housing ( 1 ) is set. 13. Exhaust gas catalytic converter according to claim 11 or 12, characterized in that a support cross ( 28 ) is arranged in the housing ( 1 ) in the exhaust gas flow direction ( 12 ) behind the insert (wire mesh insert 4 ). 14. A method for producing a catalyst insert according to one of claims 1 to 10, characterized by the following process steps:

• - knitting or weaving of the individual layers (wire mesh layers 9 , 10 , 24 ),
• - winding the layers (wire mesh layers 9 , 10 , 24 ) into a winding body ( 27 ),
• - Thermal and / or mechanical fixing of the wires ( 18 ) of the winding body ( 27 ) and
• - Applying a catalytically active coating (wash-coat coating 22 ) on the wires ( 18 ).

15. The method according to claim 14, characterized in that provided with a before or after the knitting or weaving of the wires ( 18 ) on the solder layer ( 19 ) provided wires ( 18 ) of the winding body ( 27 ) at their contact points ( 20 ) within and between the individual layers (wire mesh layers 9 , 10 ) are soldered for thermal fixation. 16. The method according to claim 14, characterized in that the wires ( 18 ) of the winding body ( 27 ) at the contact points ( 20 ) within and between the individual layers (wire mesh layers 9 , 10 ) are welded for thermal fixation. 17. The method according to any one of claims 14 to 16, characterized in that a wire mesh ( 10 ) or fabric layer ( 24 ) embossed in a flat state in wave form and with a flat wire mesh ( 9 ) or fabric layer ( 24th ) is wound up simultaneously into a winding body ( 27 ) with two-layer winding layers ( 8 ). 18. The method according to any one of claims 14 to 17, characterized in that the winding body ( 27 ) before or after its thermal fixation tion is pressed to its final shape. 19. The method according to any one of claims 14 to 18, characterized in that in the winding body ( 27 ) for mechanical fixation stabilization pins ( 13 ) are driven. 20. The method according to any one of claims 14 to 19, characterized in that the wires ( 18 ) are provided with a "wash-coat coating" ( 22 ).