DE8717394U1 - Metallic catalyst carrier body made of two differently corrugated sheet metal layers - Google Patents

Description

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8766 7 0 2 EN

Interatom GmbH

D-5060 ö£egisch Gladbach 1

Metallic catalyst carrier body made of two differently corrugated sheet metal layers

The present invention relates to a catalyst carrier body according to the preamble of the claim Metallic catalyst carrier bodies of this type are used, for example, in the exhaust systems of motor vehicles preferably as so-called "starter catalysts" These catalyst carrier bodies are exposed to high thermal cycling, which limit their service life.

Various ways of increasing the elasticity of such catalyst carrier bodies and of controlling the pressure and tensile forces have already been proposed. DE-OS 26 36 672 also discloses a catalyst carrier body which is constructed from alternating layers of two differently corrugated sheets. Various problems arise with this known type of double corrugation, as with other known embodiments of double corrugations. Corrugations with very small wavelengths are difficult to produce in terms of production technology and, in addition, with irregularly wound double corrugations, the gas-permeable channels that form vary greatly in size. With other wavelength ratios of the double corrugations, where the number of contact points between the sheet layers is reduced, undefined gaps occur between the sheet layers. All of this leads to disadvantages when the catalyst carrier body is later coated with a ceramic mass and the actual catalyst material. Either channels with a small

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Cross-section and small gaps close up or undesirable ceramic bridges are created in small gaps* which later crumble under alternating thermal stress.

The object of the present invention is an elastic, metallic catalyst carrier body which avoids the disadvantages of the prior art mentioned above. In particular, the catalyst carrier body according to the invention should have as even a distribution of the channel cross-sections as possible, so that no pressure losses occur due to blocked small channels and gaps and no ceramic coating can crumble off.

To solve this problem, a catalyst carrier body with the characterizing features of claim 1 is proposed. The decisive feature of these features is that the two differently corrugated sheet metal layers have such periodicities that they can be synchronized with each other during winding. The result is a very even distribution of contact points that are nestled against one another and have the same direction of curvature between the two sheets. By selecting the shape of the corrugations, the amplitudes and the periodicities accordingly, it can be achieved that no channels with a very small cross-section are created at these contact points, but that each wave crest of the first corrugation only touches the second sheet metal layer once. The inventive selection of the ratio between the periodicities of the two sheet metal layers ensures that at least very many contact points that nestle against one another are created during winding. Although it is not possible to achieve with a spiral winding that both the wave crests and the wave troughs of the first layer nestle against the corresponding crests or valleys of the second layer, this can be achieved at least for one of the two sides. A

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Despite the very even distribution of the channel cross-sections, the catalyst carrier body has a high degree of elasticity, since all the surfaces that delimit the individual channels are curved and can therefore be deformed relatively easily. This is not the case, for example, with the wound catalyst carrier bodies made from alternating layers of smooth and corrugated metal sheets, which are also known from the state of the art. When installing such a catalyst carrier body in a jacket tube, which prevents thermal expansion, this elasticity is a great advantage and significantly increases the service life.

According to claim 2, it is proposed that the corrugations are produced by intermeshing toothed rollers. The simplest waveform that can be produced in this way is a sinusoidal shape, but other waveforms are also possible, for example with steeper or less steep edges. The periodicities, i.e. the wavelengths, of the two waves should also be 2:1. In order to meet the condition that a wave crest of the first corrugation may only touch the second sheet layer once, the amplitude of the second corrugation may be a maximum of half the amplitude of the first corrugation, with the wave shape otherwise being the same. However, such a large amplitude of the second corrugation was not achieved despite the the advantages of the present invention still lead to relatively different channel cross-sections. Therefore, claim 3 proposes that the amplitude of the second corrugation should be less than a quarter of the amplitude of the first corrugation, preferably even less than a Eighth. In this design, the corrugation of the second sheet layer is still sufficient to achieve a "synchronization" of the two corrugations during winding, but despite the high elasticity, it no longer results in very different channel cross-sections in the entire catalyst carrier body. As in claim 4 suggested, the wavelength ratios of the two corrugations can also be, for example, 1 : 3 and a

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j have an amplitude ratio that is greater than 1:3* The above considerations apply analogously. However, with a first wave length that is already relatively small, technical limits are set for the smaller second wave length* 5

In claim 5 it is proposed that the catalyst carrier bodies according to the invention should be fully or partially reinforced on the front sides. This measure, which is well known in the art, does not lead to an undesirable stiffening of the front sides in the case of the present inventive design, since, as stated, all channel walls are at least slightly curved and thus elastic. In addition, the contact points according to the invention, which are nestled against one another, can be soldered particularly durably, since these contact points develop a greater capillary effect due to the sharper angles between the sheet metal layers and therefore absorb liquid solder.

According to claim 6, it is further proposed that the inward-facing wave troughs of the first corrugation during winding should be synchronized with the inward-facing wave troughs of the second corrugation, so that the contact points nestled against one another are created there. This is technically easier during winding than synchronizing the outward-facing wave crests, since at least in the inner area

of a catalyst carrier body, the wave crests are significantly larger than the wave troughs, since the circumference at the height of the wave crests is significantly larger than at the height of the wave troughs. The first sheet metal layer with its significantly larger amplitude can compensate for these differences more easily by slight deformation if the synchronization with the second sheet metal layer takes place at the wave troughs.

An embodiment of the invention is shown schematically in the drawing. The drawing shows a greatly enlarged and straightened section of a

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Front view of a catalyst carrier body according to the invention. A first sheet metal layer 1 with the wavelength &lgr; and the amplitude A is spirally wound synchronously with a second sheet metal layer 2 with the wavelength X ₂ and amplitude A&rdquor;. In the present, preferred embodiment, the wavelengths "λ, to λ._ are 2:1. This means that the wave troughs of the first sheet metal layer 1 can be wound up in synchronization with the wave troughs of the second sheet metal layer 2, so that contact points 3 that are nestled against one another are created. The wave crests of the first sheet metal layer 1 cannot generally be synchronized at the same time as the corrugation of the second sheet metal layer 2, so that irregular contact points 4 are created there, which, however, does not negatively affect the advantageous properties of the catalyst carrier bodies according to the invention. The selected channel length ratio results in only slightly different cross-sections for the individual channels. The channels 5 located on the inside of the first sheet metal layer 1 generally have a slightly smaller cross-section than the channels 6 located on the outside of this sheet metal layer. If the wavelength ratios are selected differently from those in the present embodiment, these differences can be somewhat larger or smaller. However, particularly small or particularly large cross-sections do not occur, and the distribution of the different cross-sections is very uniform.

Catalyst carrier bodies according to the invention are particularly suitable as starting catalysts for installation close to the engine with high thermal cycling and are characterized by a long service life.

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Claims (6)

&bull; a * &bgr; · 87 &eacgr; 6 7 O 2 DE claims 6 1. A metallic catalyst carrier body wound from alternating layers of two differently corrugated sheets (1, 2), wherein one sheet layer (1) has a simple first corrugation of periodicity X^ and amplitude A ₁ , which mainly determines the size of the gas-flowing channels (5, 6) formed between the sheet layers, characterized in that the second sheet layer (2) has a second ^corrugation of periodicity λ 2 ^and amplitude A ₂ , wherein the following conditions apply: - ^a) ^2 ⁼ with &eegr; = 1, 2 or 3 and m = 1, 2, 3, 4, 5 or 6 and m ^ n, whereby the catalyst carrier body has many adjacent, periodically recurring contact points (3) of the same direction of curvature; b) A ₂ is, taking into account the shape and periodicity of the corrugations, at least so much smaller than A-, that the curvature of the first sheet layer (1) at these periodic, mutually nestling contact points (5) is approximately equal to or slightly greater than the curvature of the second sheet layer (2) at these points (3). 2. Catalyst carrier body according to claim 1, characterized in that the corrugations are preferably produced by intermeshing toothed rollers and are approximately sinusoidal and that ^a) . %1
A-, = &mdash;■-&mdash; and Z2 3. Catalyst carrier body according to claim 2, characterized in that A ₂ 2s ^i» Preferred 02 Oil &Ggr; · * tt · &bull; tr· 6 7 02 EN 4. Catalyst carrier body according to claim 1, characterized marked that applies: 5 a) b) 5. Catalyst carrier body according to claim 1, 2, 3 or 4, characterized in that one or both end faces of the catalyst carrier body are completely or partially bonded at the contact points (3, 4) between the two 15 sheet metal layers (1, 2) are soldered. 6. Catalyst carrier body according to claim 1, 2, 3, 4 or 5, characterized in that the mutually nestling contact points (3) between the two sheet metal layers (1, 2) are arranged on the inside of the first sheet metal layer (1) and on the outside of the second sheet metal layer (2). 038 02 02