DE2760151C2 - Moulded part for lining silencers on exhaust pipes - Google Patents

Description

The invention relates to a molded part for lining silencers on exhaust pipes of internal combustion engines, in particular on exhaust pipes of motor vehicles, according to the preamble of claim 1.

Heat and corrosion-resistant components for silencers are known from DE-GB 72 23 051. This is a nonwoven sheet made of heat and corrosion-resistant material in which a layer of mineral fiber is bonded to a layer of metal fiber. The layers can be bonded in various ways, with particular consideration being given to needling or quilting the two layers together, or connecting them with yarn or wire, or joining them together using some kind of adhesive. This always ensures that the metal fiber absorbs the hard pulsation of the exhaust gas streams and the mineral wool behind it is protected in this way, so that the mineral wool fibers can no longer break or be damaged in any other way.

From DE-GB 72 23 051, according to the preamble of claim 1, it is also known to design such a body as a molded part or pressed part. In practice, to produce such molded parts, it is usual to provide the mineral fiber layer with a binding agent to achieve internal cohesion and to harden it under pressure. The hardened mineral fiber molded part produced in this way is then provided with the metal fiber fleece, which is applied to the hardened mineral fiber layer. In this process, metal fibers penetrate only slightly into the hardened and fixed surface of the mineral fibers at the contact surface, and the securing of the position of the metal fiber layer on the mineral fiber layer, which is particularly necessary for handling the molded part when mounting it on the exhaust pipe, takes place in the manner explained, for example by needling or by means of an adhesive layer introduced between the two layers.

The connection of a layer of metal fiber and a layer of mineral fiber using yarn or wire has the disadvantage that the required large stitch and seam spacing of the quilting seams only allows the production of relatively large parts. In the case of small parts, such web pieces would fall apart according to the quilting seams drawn. In addition, the result is not a full-surface connection of the fiber layers, but only a linear one.

A carrier material is therefore generally used for the padding, which makes the production of such molded parts or mats considerably more expensive. For cost reasons, paper is often used, but this is flammable and must be rejected for safety reasons. If the molded part does not necessarily specify the installation position, the paper prevents sound absorption if it is accidentally installed incorrectly in the silencer. This is why silencer manufacturers often remove this paper, which in turn increases production costs.

It is also known to produce corresponding molded parts in which loose mineral fibers are arranged around a metal fiber tube and fixed in this position by a paper sheath.

Here too, the flammability of the paper prevents its sensible use. In addition, a significantly higher metal fiber content is required, since the metal fiber tube contributes to the stability of these molded parts and therefore has to be made sufficiently strong.

If an adhesive is used to connect the mineral fiber layer to the metal fiber layer, this will not work either, because the adhesive can be broken down by the temperatures prevailing in silencers, causing the layers to separate from one another and the lining to lose its cohesion. In addition, such a closed adhesive layer impairs the sound absorption of the mineral fiber layer. In any case, even when using adhesives that evaporate during operation and are therefore not disruptive, an additional work step is required to apply such an adhesive layer.

Further measures known from CH-PS 4 40 631 and DE-GM 76 28 169 are explained in connection with the advantages of the invention.

Overall, all of these procedures for bonding a metal fiber layer to a cured, surface-fixed and compacted mineral fiber layer have the disadvantage that additional work steps are required, which, apart from functional disadvantages, in any case make production more expensive.

In contrast, the object of the invention is to create a molded part of the type specified in the preamble of claim 1, in which sufficient internal support and a sufficiently strong connection of the mineral fiber layer and the metal fiber layer can be achieved with minimal manufacturing effort.

This object is solved by the characterizing features of claim 1.

By bonding using the mineral fiber's binding agent, and not using a separate adhesive, the additional work step required for such an application is eliminated, and the position is still secured by bonding. This is significantly supported by the metal fibers digging into the mineral fibers, which not only mechanically secures the position but also strengthens the bonding effect of the binding agent, since mutual penetration of mineral fibers and metal fibers also allows binding agent components below the surface of the mineral fiber layer to become effective for bonding. The combined effect achieved in this way results in a secure hold of the metal fibers on the mineral fibers without the need for complex additional measures.

The procedure is such that the metal fiber layer is pressed onto the mineral fiber layer, which contains the binding agent but has not yet hardened and therefore has a loose surface, and only hardens the mineral fiber layer after pressing. When pressed, the metal fibers penetrate the still loose surface of the mineral fiber layer and, during the pressing process, become entangled with the mineral fibers. The metal fibers come into contact with the binding agent in the mineral fiber layer at the same time and are bound by it when it hardens. In this way, the connection between the metal fiber layer and the mineral fiber layer is achieved by entangling and bonding, without any additional work being required. Rather, the metal fiber layer is brought together with the mineral fiber layer during the production of the mineral fiber layer before it hardens, and then, without any further action, the desired entanglement and bonding of the fibers of both layers is achieved.

It is known from practice that synthetic resin-bonded mineral fiber mats are produced in which mineral fibers that have already been sprayed with a binding agent are placed on a conveyor belt underneath the fiberizing unit or units. This conveyor belt guides the mineral fiber mat thus formed through a so-called drying tunnel in which the mineral fiber mat is pressed to the desired thickness and the binding agent is hardened by heat. However, a combination with metal fibers to connect them by interlocking and gluing does not take place.

A fireproof mineral fiber board is already known from Swiss patent 4 40 631, which is pressed and dried from a slurry of mineral fibers under elevated temperature and pressure. In order to be able to add reinforcements and, if necessary, structural parts such as door fittings to the mineral fiber material, similar to reinforced concrete, it is planned to either press such reinforcement elements onto the surface of the wet mat or to arrange them between two wet mats and press them together so that they are held in place by the binding agent. Wire mesh, expanded metal sheets, wires, threads, perforated sheets and the like, usually made of steel or other metals, can be used as reinforcement material.

Metal threads as tensile reinforcement elements do not form a second layer on the mineral fibers, but are embedded in them on the surface. In view of the smooth circumference of reinforcement threads, interlocking effects for additional positional security cannot occur. According to the invention, however, a metal wool layer is applied to the mineral fibers that have only been sprayed with a binding agent, which forms a second layer made of different types of fibers than the mineral fibers, with the wool layers only bonding and interlocking of the fibers on the surfaces of the two wool layers that are in contact with one another during the curing process. Mechanical reinforcement of the mineral fiber layer, for example against tensile forces that occur, by means of embedded tensile reinforcement threads, does not occur to any noticeable extent.

The invention can be implemented particularly advantageously if, in a further embodiment according to claim 2, the mineral fiber layer is produced with a maximum 1% binder content.

It is known from DE-GM 76 28 169, for example, that ready-made parts with a maximum 1% binder content are also well suited for silencers and guarantee the required non-flammability and sound absorption. However, such ready-made parts have the disadvantage that they have to be machined from a solid plate to fit the contours of the silencer, which is associated with processing costs and material loss. Because a molded part according to the invention is not first cured and then provided with a metal fiber layer, which requires complex additional fastening measures, but rather is combined with the metal fiber layer before curing, whereby the mineral fiber material of the molded part is still in an easily moldable, loose state when combined with the metal fiber layer, the molded part can thus be adapted to the contours of the silencer without material-removing processing during pressing. The mutual connection is also successful with a low binder content of less than 1%.

Claims (2)

1. Moulded part for lining silencers on exhaust pipes of internal combustion engines, in particular on exhaust pipes of motor vehicles, with an outer layer of mineral fibres sprayed with a binding agent, preferably basalt wool, and an inner layer of metal wool, preferably stainless steel wool, applied thereto and connected thereto, characterized in that the layers are pressed together and the connection is brought about without further action by the binding agent of the mineral fibres in the course of its hardening. 2. Moulded part according to claim 1, characterized in that the binder content of the mineral fibre layer is a maximum of 1%.