Honeycomb

Details Honeycomb Honeycomb

2000-05-12

2004-04-13

Jones, Deborah (Department: 1775)

Stock material or miscellaneous articles

Structurally defined web or sheet

Honeycomb-like

C428S593000, C428S188000, C422S177000

Reexamination Certificate

active

06720060

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The invention relates to a honeycomb, particularly a catalytic converter substrate, pursuant to the generic part of claim 1 and a process for its manufacture.
The honeycomb can consist of smooth and/or structured foils, which can be arranged in plane or curved foil layers. The honeycomb can be surrounded by a housing, in which several honeycombs can also be accommodated one behind the other or adjacent to each other, where the individual honeycombs can be partially separated by walls or supports.
2. Prior Art
Document EP 0 430 945 B1 discloses a generic honeycomb consisting of at least three stacks of foils, these being folded about an associated bending line and wrapped around the bending line. The end areas of the foils are connected to each other and/or to the housing, at least along part of the lines of contact, by jointing techniques, preferably by brazing, in order to achieve sufficient stability of the honeycomb.
Particularly when using the honeycombs as catalytic converter substrates, they are, as a result of temporal and local temperature gradients, exposed to very high stresses that, particularly as a result of the low strength of the foils and joints, lead to cracks and compression of the honeycombs at high temperatures, and thus to a changing honeycomb structure, this altering the properties of the catalytic converter. It must be borne in mind in this context that the honeycomb can easily be used at temperatures of 900° C. and that temperatures differences within the honeycomb of 300 to 400° C. can occur in this case. Moreover, the joining of the foils by brazing is a comparatively complex and expensive process.
OBJECT AND SUMMARY OF THE INVENTION
The object of the invention is to create a honeycomb that is inexpensive to manufacture, displays a honeycomb structure that is sufficiently stable under the anticipated stresses, and demonstrates particularly high resistance to thermal shocks.
Due to the stiffening elements introduced according to the invention, which extend transverse to the foil layers i.e. intersect the major plane of the foil layers at an angle, for instance a 90° angle, the honeycomb structure is sufficiently stabilised. Forces resulting from temperature changes, for example, are absorbed by the stiffening elements and no longer, or no longer exclusively, by the joints connecting the foils to each other or to the housing. The stiffening elements, which are capable of withstanding tensile forces at least in the longitudinal direction, extend across several ducts through which flow is possible. The stiffening elements can pass through the foils in this context, e.g. two or more than two, and/or at least partially surround the honeycomb on the outside and, if appropriate, extend through or around the entire honeycomb.
The stiffness of the stiffening elements can correspond to that of the foils or, given appropriate orientation, also be less than that of the foils, e.g. half the foil thickness, e.g. using appropriate wires or strips. Preferably, the stiffness in the transverse direction of the stiffening elements is significantly higher than that of the foils, but substantially lower than that of the housing. In this way, while using the same material, the thickness of the stiffening elements can be two to five times the foil thickness of the thinnest foils, possibly up to ten times the foil thickness or more. Referred to the housing, the stiffening elements can display roughly half the housing thickness, advantageously one-quarter to one-eighth of the housing thickness, or also less than this given a corresponding difference between the thicknesses of the housing and the foils. It goes without saying that, given a corresponding choice of material, the stiffness ratios do not directly correspond to the material thickness ratios. The wall thickness of the housing can thus be 0.5 to 1.5 mm, for example, and that of the foil approx. 0.02 to 0.06 mm. This thickness of the stiffening elements can be equal to the foil thickness or a multiple thereof.
If, transverse to their direction of extension, the stiffening elements are elastically deformable relative to the housing and/or mounted on the housing in elastically deformable fashion, e.g. by areas of increased flexibility or extensibility located between them, the honeycomb displays high resistance to thermal shocks and great stability, as the foils are not rigidly fastened to each other by means of the stiffening elements, there being compensation for expansion and simultaneous stabilisation instead. The elastic deformability can exist in one or both directions transverse to the direction of extension of the stiffening elements. The elastically deformable sections are advantagegeously deformable under forces acting at temperature changes between room temperature and about 600 to 1000° C. on the honeycomb, advantageously in an extend that the tensions occurring due to the temperature changes could be absorbed significantly by the elastically deformable sections, for instance to an extend of more than 25% or more than 50%, advantageously substantially complete.
Elements of very high stiffness can also be introduced into the honeycomb, e.g. in the form of one or two-dimensional braces, the stiffness of which can be up to the stiffness of the housing or more and which are fixed to the housing indirectly or directly via elastically deformable areas. Areas of high stiffness thus alternate with the expansion areas guaranteeing the resistance to temperature shocks.
The stiffening elements according to the invention stabilise the honeycomb independently of the housing and permit relative movement of the foils in relation to the housing, this allowing optimum adaptation of the stiffness and load dissipation into the housing, on the one hand, and of the expansion properties, on the other hand, each of which have an influence on the function, stability and resistance to thermal shocks of the honeycomb. Moreover, this can also offer the option, if appropriate, of handling the honeycomb independently of the housing, e.g. when coating with catalytically active material.
The honeycombs according to the invention can, in particular, be used as catalytic converter substrates in the automotive sector, but also for other catalytic converters, e.g. in the power station sector or in chemical engineering. Accordingly, the diameter of the flow ducts can also vary over wide ranges, e.g. from approx. 1 mm to approx. 1 to 2 cm, without limitation. The flow ducts can be of one or two-dimensional design in each case.
The stiffening elements can be of one or two-dimensional design, e.g. in the form of wires, screws, strips, foils, particularly perforated foils or expanded-metal layers or the like. In this context, the stiffening elements can be of straight or curved design and extend parallel and/or perpendicular and/or at an angle to the foils forming the honeycomb structure. If appropriate, foil-type stiffening elements can also be used to divide the honeycomb structure into component honeycombs that are independent of each other in terms of flow, in which case the honeycomb continues to be a single structural unit.
The stiffening elements can be provided with meshing surfaces, such as threads, tooth profiles and the like, to form a positive connection with the respective corresponding component. In addition, the stiffening elements can also display resilient areas or plastically deformable areas extending in their longitudinal direction, these being produced by shaping or bending in each case, e.g. in the form of spiral wire springs, wire, strips of foil sections bent in meandering fashion, slitted foils or strips, expanded metal and the like.
The stiffening elements can be designed as wall sections that partially or completely pass through the honeycomb or border it on the outside as an outer wall. The wall sections can be made of downward-folded sections of the foils that are connected to each other, preferably over a large area. In this context, the sections can be c

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