Honeycomb body, in particular a catalytic converter carrier body, with a reinforced wall structure

A honeycomb body, in particular a catalytic converter carrier body, with stacked and/or wound sheet layers of which at least a portion are structured sheet layers, thus forming passages through which a fluid can flow. A portion of the sheet layers is of a first thickness and a portion of the sheet layers is of a second thickness which is greater than the first thickness. The honeycomb body contains in its interior a lattice-like structure that is formed from at least two sheet layers of the second thickness, of which at least one is a structured sheet layer and which at least in a location-wise manner are connected together by a procedure involving the intimate joining of materials. Honeycomb bodies according to the invention, while affording good stability, can have particularly thin sheet layers whereby at least locally they have a particularly low thermal capacity.

BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION 
The present invention concerns a honeycomb body having stacked and/or wound 
sheet layers of which some of the sheet layers are structured sheet layers 
forming passages in which a fluid can flow. Honeycomb bodies of this kind 
are used for example for the catalytic conversion of exhaust gases of an 
internal combustion engine. 
European Patent EP 0 436 533 B1 discloses honeycomb bodies which contain a 
stack, twisted in mutually opposite directions, of at least partially 
structured metal sheets in a tubular casing. One or more of the sheet 
layers of the stack is of greater thickness than the other layers, wherein 
the layer or layers contain or contains a thicker sheet or a plurality of 
thin sheets which bear closely against each other. The thicker and thinner 
sheet layers form walls of passages, through which the exhaust gas stream 
can flow. The sheet layers are connected to the tubular casing, at least 
in portions thereof, by a procedure involving intimate joining of the 
materials involved. The thicker sheet layers cannot be easily torn away at 
the tubular casing, by virtue of their greater mechanical strength. In 
addition they can also hold fast the thinner sheet layers which are 
adjacent thereto so that they also cannot be torn away from the tubular 
casing or however are held fast by the thick sheet layer at least in spite 
of being torn away at the tubular casing. The individual metal sheet 
layers of the stack can be soldered together, preferably at one of the two 
ends of the honeycomb body. The above-described configuration, by virtue 
of the thick sheet layers, affords a wall structure for stabilizing the 
honeycomb body. 
In recent years the development of new honeycomb bodies has been along the 
lines of reducing thermal capacity. With a lower thermal capacity it is 
possible to achieve in particular improved cold start performance when 
using the honeycomb bodies in exhaust gas catalytic converters. The 
ignition temperature as from which the catalytic procedure begins is 
achieved earlier. Besides thermal capacity the pressure drop which occurs 
in a gas flow through the honeycomb body also plays a part in development. 
The pressure drop should be as low as possible. Both development aims, 
namely a low thermal capacity and a low pressure drop, can be achieved by 
the use of thin passage walls. However the passage walls cannot be made of 
just any arbitrarily thin dimension as the wall structure otherwise 
becomes unstable and is damaged under thermal and/or mechanical loadings. 
SUMMARY OF THE INVENTION 
It is accordingly an object of the invention to provide a honeycomb body, 
in particular a catalytic converter carrier body, with a reinforced wall 
structure that overcomes the above-mentioned disadvantages of the prior 
art devices of this general type, which enjoys a high level of stability. 
With the foregoing and other objects in view there is provided, in 
accordance with the invention, a honeycomb body including a catalytic 
converter carrier body, including sheet layers being at least one of 
stacked and wound sheet layers having an interior, part of the sheet 
layers being structured sheet layers having passage wall surfaces defining 
a passage through which a fluid can flow, some of the sheet layers having 
a first thickness and others of the sheet layers having a second thickness 
being greater than the first thickness, at least two of the sheet layers 
of the second thickness forming a lattice-shaped structure in the interior 
and at least one of the at least two of the sheet layers of the 
lattice-shaped structure being a structured sheet layer and the at least 
two of the sheet layers of the lattice-shaped structure connected together 
at least in a location-wise manner by a procedure involving intimate 
joining of materials, a larger portion of the passage wall surfaces in the 
interior formed by the sheet layers of the first thickness than by the 
sheet layers of the second thickness and the first thickness being between 
15 .mu.m and 50 .mu.m. 
A honeycomb body according to the invention has sheet metal layers of a 
first thickness and sheet metal layers of a second thickness, wherein the 
second thickness is greater than the first thickness. In its interior the 
honeycomb body contains a lattice-like structure which is formed from at 
least two sheet layers of the second thickness. Of those sheet layers at 
least one is a structured sheet layer. The at least two sheet layers are 
connected together at least in a location-wise manner by a procedure 
involving intimate joining of materials, preferably by being soldered 
together. 
The reference to "a" thickness of a sheet layer denotes the mean thickness 
of the sheet material, while the local thickness can vary by some percent 
of the mean thickness. 
The connecting locations are point-like, line-like or surface-like. 
Connections involving intimate joining of the materials involved exist 
preferably over the entire length of the lattice-like structure, that is 
to say in the direction of flow through the passages, and transversely 
with respect to the direction of flow through the passages. A crucial 
consideration in terms of the stability of the honeycomb body is adequate 
inherent stability of the lattice-like structure. The connections 
involving intimate joining of the materials are therefore preferably 
continuous or disposed at suitable spacings. Depending on the 
configuration of the honeycomb body and the purpose of use however a 
connection involving intimate joining of the material involved is under 
some circumstances also adequate at the ends of the passages, that is to 
say at the ends of the honeycomb body. 
An advantage of the invention is that honeycomb bodies with thin walls can 
be of a stable structure. By virtue thereof it is possible for example to 
achieve a high cell density, that is to say a large number of passages per 
unit area in the cross-section of the honeycomb body, without having to 
tolerate the disadvantage of a high pressure drop. A high cell density has 
a favorable effect on the catalytic conversion of exhaust gases as it is 
possible to achieve a large catalytically active surface area per unit 
volume of the honeycomb body. 
In cold start phases or re-starting phases of an internal combustion engine 
with an exhaust gas catalytic converter it is important for the catalytic 
converter to reach the ignition temperature as quickly as possible. Thin 
walls permit that to occur, by virtue of their low thermal capacity. The 
crucial consideration is that the ignition temperature is reached quickly, 
at least locally at the thin walls. There is however no need for it to be 
attained approximately simultaneously everywhere in the catalytic 
converter as the chemical reactions which take place after the ignition 
temperature is attained are exothermic. The zones in which the ignition 
temperature is reached or exceeded therefore rapidly spread. 
The use of honeycomb bodies according to the invention results in early 
initiation of the catalytic procedure in exhaust gas catalytic converters. 
With the sheet layers of the first and second thicknesses receiving an 
approximately uniform incident flow of hot exhaust gas the catalytic 
procedure begins at the (thinner) sheet layers of the first thickness and 
rapidly spreads to the sheet layers of the second thickness. In comparison 
with honeycomb bodies of the same thermal capacity in respect of the sheet 
layers but only with sheet layers of one thickness, the catalytic 
procedure begins more quickly in the invention of the instant application. 
However it still begins more quickly even when the thermal capacity of the 
sheet layers of the honeycomb body according to the invention is greater, 
as long as there are thinner sheet layers. 
The connection by the intimate joining of the materials involved is 
preferably effected after the step of stacking and/or winding or coiling 
the sheet layers. Otherwise the sheet layers of the first thickness could 
be damaged, for example torn through, by the sheet layers of the second 
thickness or the lattice-like structure. 
The sheet layers are preferably soldered together. For soldering the 
lattice-like structure it is possible to consider all known soldering 
procedures in which finishing of the soldering operation is possible after 
stacking and/or winding or coiling of the sheet layers. In particular it 
is also possible to use different soldering processes for soldering the 
lattice-like structure and soldering the other sheet layers. For example 
solder foils or solder wires can be wound in between the sheet layers of 
the lattice-like structure. In that way solder joints can also be produced 
in the interior of the honeycomb body, within the lattice-like structure, 
while the other sheet layers are for example soldered together and to the 
lattice-like structure only at the ends of the honeycomb body. 
In regard to the honeycomb body according to the invention there are 
configurations with a plurality of lattice-like structures which are 
preferably uniformly distributed over the stack or winding of the sheet 
layers. 
A honeycomb body according to the invention is for example constructed with 
partially structured sheets, as described in the European Patent EP 0 436 
533 B1. The passage walls formed by sheet layers are preferably of a 
thickness that remains approximately the same over the axial length of the 
honeycomb body. There are however also embodiments in which the reinforced 
lattice-like wall structure extends only over one or more portions of the 
axial length of the honeycomb body. That can be achieved for example by 
portion-wise reinforcement of the sheet layers with shorter sheet layers. 
In a further embodiment with structured sheet layers the structures have 
line-like raised portions or ridges with which they contact adjacent sheet 
layers. At least two adjacent sheet layers which are structured in that 
way are in mutual contact with raised portions or ridges which extend in 
mutually crossed relationship so that they only touch each other in 
approximately point-wise manner. Those sheet layers are sheet layers of 
the second thickness and at a plurality of the contact points are 
connected together by a procedure using intimate joining of the materials 
involved, preferably by being soldered together, thus affording a 
three-dimensional lattice-like wall structure which stabilizes the 
honeycomb body. 
An advantage of the honeycomb body according to the invention is that 
forces which act on the lattice-like wall structure in directions in 
which, at any event at the locations at which the forces act, no sheet 
layers of the second thickness extend, can also be carried away by way of 
the lattice-like wall structure. 
A further advantage of the honeycomb body according to the invention is 
that of a favorable vibration characteristic. Due to its stable 
construction the lattice-like structure is insensitive to vibration. In 
addition however it also reduces the vibration lengths, perpendicularly to 
the axial length of the honeycomb body, of the regions with thinner sheet 
layers. The vibration lengths can be matched to a given purpose of use of 
the honeycomb body. Care is to be taken to ensure that no resonance 
vibrations of the honeycomb structure are induced. 
In a development of the honeycomb body according to the invention a larger 
part of the passage wall surfaces in the interior of the honeycomb body is 
formed by the sheet layers of the first thickness than by the sheet layers 
of the second thickness, with the first thickness being at least 20% less 
than the second thickness. 
In an embodiment of the honeycomb body the first thickness is of a value of 
between 15 .mu.m and 50 .mu.m, preferably about 20-30 .mu.m. 
In an advantageous development, the honeycomb body has a tubular casing, in 
the interior of which the sheet layers are disposed, wherein the 
lattice-like structure has a plurality of casing connecting locations at 
each of which at least a respective one of its sheet metal layers of the 
second thickness is connected to the tubular casing. That configuration 
can provide a stable unit containing the tubular casing and the 
lattice-like structure. An advantageous development thereof is one in 
which two casing connecting locations are connected together by the 
lattice-like structure. 
An embodiment of the honeycomb body according to the invention provides for 
the formation of passages through which a fluid can flow and which extend 
in substantially parallel relationship and which are approximately closed 
off relative to each other. The honeycomb body has stacked and/or wound or 
coiled sheet layers, of which at least a portion are structured sheet 
layers, wherein the configuration has sheet layers of the second 
thickness, with which the lattice-like structure is formed. The sheet 
layers of the second thickness are connected by a procedure using intimate 
joining of the materials involved, preferably soldering, at contact 
locations, to at least one other sheet layer of the second thickness, 
and/or there blend into another sheet layer of the second thickness. In 
other words, the sheet layers that blend into each other are parts of the 
same sheet. This embodiment includes honeycomb bodies which are wound in a 
spiral configuration, honeycomb bodies which are constructed in an S-shape 
and other embodiments of previously known honeycomb bodies with stacked 
and/or wound sheet layers. In certain alternative forms of the embodiment 
the lattice-like structure is formed from one or more sheets of the first 
thickness, which are reinforced in a portion-wise manner by sheet strips 
which are connected thereto by a procedure using intimate joining of the 
materials involved. Those portions form the passage walls of the second 
thickness. 
In a further embodiment, the lattice-like wall structure has a plurality of 
adjacent sheet layers of the second thickness, which have together, in 
respective pairs, a plurality of connecting locations, at least one of the 
sheet layers being a structured sheet layer. 
In a development, the lattice-like structure extends with two or more sheet 
layers, as viewed in the cross-section of the honeycomb body, 
approximately along a line extending in the manner of a spiral arm, 
preferably approximately along an involute. In still another development 
the honeycomb body has in cross-section a plurality of lattice-structured 
spiral arms. The spiral arms are connected together in the region of a 
spiral core, wherein the spiral arms preferably include approximately 
equal angles between them, at the spiral core. In that respect the angle 
is to be measured between the lines connecting the center of the spiral 
core to the points of attachment of the spiral arms to the spiral core. 
The spiral arms, the spiral core and optionally a tubular casing connected 
to the outer ends of the spiral arms form a stable framework, between 
which the passage walls of the first thickness are disposed. In an 
alternative form of this development the inner ends of the spiral arms are 
not connected together by way of a spiral core, but are directly connected 
to each other. In that situation the spiral arms divide each imaginary 
circle with a center point in the proximity of the connecting region of 
the spiral arms, the peripheral line of which is cut by the spiral arms, 
into portions of approximately equal size. 
In a further embodiment the honeycomb body is of a structure similar to 
that described in the European Patent EP 0 436 533 B1, with a stack of 
sheet layers, which stack is twisted in mutually opposite directions, 
wherein the lattice-like structure is disposed approximately at the center 
of the stack. In a development the stack includes further lattice-like 
structures, preferably such that an equal number of sheet layers are 
disposed between the lattice-like structures. 
Other features which are considered as characteristic for the invention are 
set forth in the appended claims. 
Although the invention is illustrated and described herein as embodied in a 
honeycomb body, in particular a catalytic converter carrier body, with a 
reinforced wall structure, it is nevertheless not intended to be limited 
to the details shown, since various modifications and structural changes 
may be made therein without departing from the spirit of the invention and 
within the scope and range of equivalents of the claims. 
The construction and method of operation of the invention, however, 
together with additional objects and advantages thereof will be best 
understood from the following description of specific embodiments when 
read in connection with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In all the figures of the drawing, sub-features and integral parts that 
correspond to one another bear the same reference symbol in each case. 
Referring now to the figures of the drawing in detail and first, 
particularly, to FIG. 1 thereof, there is shown a honeycomb body 1 
according to the invention with a stack, twisted in mutually opposite 
directions, of mutually alternate smooth sheet metals layers 17 and 
structured sheet metal layers 18. Approximately at its center, the stack 
includes a lattice-like structure 4 with a plurality of connecting 
locations 5, which is made up of two adjacent sheet layers 3. Those sheet 
layers 3 are sheet layers of a second thickness b. The other, oppositely 
twisted sheet layers are sheet layers 2 of a first thickness a. The stack 
is disposed in an interior of a tubular casing 6, wherein the lattice-like 
structure 4 is soldered to the tubular casing 6 at casing connecting 
locations 8. The solder connection or connections between the tubular 
casing 6 and the lattice-like structure 4 preferably extends or extend 
only over a portion or portions of an axial length of the tubular casing 
(not shown in the drawing) in order to permit different variations in 
length, due to thermal causes, of the tubular casing 6 and the wall 
structure. The sheet layers 2, 3 of the first thickness a and the second 
thickness b can be soldered together at some of or all their contact 
locations. 
FIG. 2 shows a honeycomb body 21 with wound or coiled sheet layers 2, 3 
that extend in cross-section approximately along involutes. Disposed 
approximately on a center axis of the honeycomb body 21 is a spiral core 7 
in the form of a hollow cylinder to which the sheet layers 2, 3 are 
connected. The honeycomb body 21 has two lattice-like wall structures 14 
that in cross-section follow spiral arm-like lines. They are each made up 
of three sheet layers 3, two being smooth and there between a structured 
layer, and they are disposed approximately symmetrically relative to each 
other with respect to the center axis of the honeycomb body 21. The angle 
.alpha. that they include between them at the spiral core 7 is therefore 
approximately 180.degree.. 
FIGS. 3 to 5 each show a portion of the lattice-like structure 4 having at 
least one smooth sheet layer 17 and the structured sheet layer 18, which 
are both of the second thickness b, and have a plurality of the connecting 
locations 5. The lattice-like structure 4 in FIG. 3 has triangular 
bordered passages 9. The passages 9 in FIG. 4 are approximately triangular 
in cross-section. Indicated by way of example with two lines that are 
straight lines along which the structured sheet layer 18 extends between 
the two smooth sheet layers 17. Of the smooth layers 17 at least one is of 
the second thickness b. The sheet layers 17; 18 of the second thickness b 
are connected together by a procedure involving intimate joining of the 
materials, at a plurality of their contact locations. If the second smooth 
sheet layer 17 in FIG. 4 is a sheet layer of the first thickness a, it is 
preferably also connected to the structured sheet layer 18 by the intimate 
joining method, at a plurality of its contact locations with respect to 
the structured sheet layer 18. FIG. 5 shows passages 9 of trapezoidal 
cross-sectional area. Lines indicate the direction along which there 
extend the lattice wall portions of the structured sheet layer 18, which 
connect the two smooth sheet layers 17 together. The two lines intersect 
outside the lattice cell 9 with an internal angle .beta.. FIG. 5 also 
shows the opposite angle .beta.' which is equal to the angle .beta.. The 
two lines make it possible to see the lattice construction which is 
basically of triangular cross-section and which imparts its stability to 
the structure. 
As the examples show, embodiments of the honeycomb body 1 according to the 
invention are of a similar structure to previously known honeycomb bodies. 
With just minor modifications they can be produced by use of the same 
processes as the previously known honeycomb bodies. Honeycomb bodies with 
lattice-like structures can therefore be produced at approximately the 
same cost but they permit the use of thinner sheet layers or they have a 
higher degree of stability than previously known honeycomb bodies.