Process for the production of a honeycomb body of twisted sheet metal layers

A honeycomb body has a plurality of at least partially structured sheet metal layers forming a plurality of passages through which a fluid can pass. The sheet metal is plastically deformed in a region of a mandrel passage whose cross-section is substantially determined by a mandrel of a winding device with which the honeycomb is formed. The free flow cross-section of the mandrel passage is closed at least in a portion of the passage along the flow direction by deforming the sheet metal with a deformation punch. The deformation punch has an end portion with a sharp-edged rim.

BACKGROUND OF THE INVENTION 
Field of the Invention 
The present invention relates to a process, a device and an apparatus for 
the production of a honeycomb body having a plurality of at least 
partially structured metal sheets which form a plurality of passages 
through which a fluid can pass. 
Catalytic converters are used for reducing the emission of pollutants from 
internal combustion engine, in particular Otto engines. The catalytic 
converter has a catalytically active substance which disposed on a 
carrier. In order to provide the largest possible surface area for the 
catalytically active substance, the carrier body may have a honeycomb 
form. Such a honeycomb body is formed from one or more stacks of a 
plurality of at least partially structured sheets. U.S. Pat. No. 4,923,109 
discloses a design configuration of a honeycomb body in which the stack is 
twisted or wound in opposite directions about itself and about a central 
region. 
International publication WO 90/03220 describes a metallic catalyst carrier 
body. That carrier body is made up from at least partially structured 
sheets. It includes three or more stacks of sheets which are folded about 
a bend line in the central region of the honeycomb body and twisted in 
opposite directions around each other and around the central region with 
the bend lines. 
Further catalyst carrier body configurations are disclosed, for instance, 
in international publication WO 94/01661. 
Catalyst carrier bodies of that kind are produced with apparatuses that 
include a forked winding or wrapping device which rotates about a central 
axis and which engages each stack. A shaping mold or matrix has an 
internal contour which substantially corresponds to the external contour 
of the honeycomb body in the wound condition. 
German published, non-prosecuted application DE 195 22 327 A1 discloses an 
apparatus for the production of a honeycomb body that has a plurality of 
at least partially structured sheets forming a plurality of passages 
through which a fluid can pass. The apparatus includes a forked wrapping 
or winding device which is rotatable about a central axis and which 
engages each stack, and a shaping mold or matrix which is of an internal 
contour corresponding to the external contour of the honeycomb body to be 
produced. The mold or matrix surrounds the winding device. The wall of the 
mold is formed with at least one opening for the stack ends. The opening 
extends substantially parallel to the central axis. During the production 
of a honeycomb body, at least one stack which is formed by a multiplicity 
of at least partially structured sheets is introduced into the mold, with 
the ends of each stack projecting out of the mold through openings. Each 
stack is held in a central region by a winding device which is rotatable 
about a central axis. As the winding device rotates, the stacks are 
twisted to form a honeycomb body which fills the entire mold. 
German published, non-prosecuted application DE 195 21 685 A1 also 
discloses an apparatus and a process for the production of a honeycomb 
body. The apparatus includes a forked winding device which is rotatable 
about an axis and which engages each stack, and mold segments which close 
to define a mold. The mold is formed from at least two mold segments. Each 
mold segment is pivotable about a pivot axis which respectively extends 
parallel to the axis of the winding device, opposite to the direction of 
rotation of the winding device. The mold segments are closed in opposite 
relationship to the direction of rotation of the winding device when the 
stack has reached a predetermined degree of winding. 
The wound honeycomb bodies are conventionally introduced into tubular 
casings. The honeycomb bodies are introduced into a tubular casing 
substantially immediately following the winding operation. In that 
procedure, the honeycomb body is pressed into the tubular casing in the 
axial direction thereof. 
The carrier body which is produced in that way is subjected to further 
production steps which involve for example brazing, sintering or welding. 
The metal honeycomb bodies are integrated into an exhaust system. For that 
purpose the two ends of the carrier body are connected to a respective 
pipe of the exhaust system. To provide for a satisfactory connection 
between the tubular casing of the carrier body and the component parts of 
the exhaust system, it is necessary for the dimensions of the tubular 
casing and the contour thereof to be within certain tolerances. In order 
to observe the required tolerances, the art calibrates the tubular casing 
of the carrier body prior to and/or after the insertion of the honeycomb 
body. The calibration is generally effected in such a way that a tool with 
a plurality of segments is introduced into the tubular casing and the 
individual segments are spread radially outwardly. The segments are spread 
beyond the yield limit of the casing material so that the tubular casing 
is stress-free in that region. International application WO 96/14500 
discloses an apparatus with which it is possible to calibrate a honeycomb 
body with a tubular casing. 
Moreover, international application WO 96/12876 discloses a catalyst 
carrier body in which the free flow cross-section of the passages is 
closed in an outer annular region, at least in a portion of the exhaust 
gas flow. The passages are closed by plastic deformation of the passage 
walls. The closed passages serve to provide for heat insulation. 
The winding device with at least one holding mandrel or bar forms a channel 
in the honeycomb body (e.g. the catalyst carrier body) whose cross-section 
is substantially determined by the cross-section of the mandrel. When a 
winding device with a plurality of mandrels is used, there result a 
corresponding number of such passages within the honeycomb body. The free 
cross-section of the mandrel passage is usually larger than the 
cross-section of the other passages in the honeycomb body. The flow 
profile is affected by the presence of at least one mandrel passage. If 
the honeycomb body has a plurality of mandrel passages, they have a 
greater influence on the catalytic effect of the honeycomb body used as a 
catalyst carrier body. 
SUMMARY OF THE INVENTION 
It is accordingly an object of the invention to provide a process for the 
production of a honeycomb body which overcomes the above-mentioned 
disadvantages of the prior art methods of this general type and which 
reduces the impact of the mandrel passages on the operating behavior of a 
honeycomb body. It is a further object of the invention to provide a 
honeycomb body, and a device and an apparatus by means of which the impact 
of the one or more mandrel passage on the operating performance of the 
honeycomb body is reduced, utilizing simple measures. 
With the foregoing and other objects in view there is provided, in 
accordance with the invention, a method of producing a honeycomb body, 
which comprises: 
providing a winding device with a mandrel; 
winding a plurality of at least partially structured sheet metal layers 
with the winding device to form a honeycomb body defining a plurality of 
passages through which a fluid can flow along a flow direction, and 
forming a mandrel passage in the honeycomb body with the mandrel of the 
winding device; and 
closing a free cross-section of the mandrel passage at least in a portion 
along the flow direction of the fluid. 
The starting point of the invention is essentially a honeycomb body with a 
plurality of at least partially structured sheets or sheet metal layers 
forming a plurality of passages through which a fluid can flow. At least 
one passage is a mandrel passage whose cross-section is essentially 
determined by a mandrel or bar of the winding device. Such a honeycomb 
body may be produced, for example, by the honeycomb body production 
process known from the German published applications DE 195 21 685 A1, DE 
195 22 327 A1 or DE 195 28 963 A1. These disclosures are herewith 
expressly incorporated by reference. 
The process according to the invention is characterized in the plastic 
deformation of at least a part of the sheets in the region of the mandrel 
passage whose cross-section is determined substantially transversely by 
the mandrel of the winding device. The free flow cross-section of the 
mandrel passage is thereby closed at least in a portion thereof relative 
to the direction of flow of the fluid (e.g. the exhaust gas). The process 
may result in a complete closure of the mandrel passages whereby the 
mandrel passages have no influence or a partial closure whereby they have 
only a very slight influence on the operating performance of the honeycomb 
body. 
The novel method is preferably integrated in conventional honeycomb body 
production methods. For that purpose, in accordance with an added feature 
of the invention, the sheets are plastically deformed in the region of the 
mandrel passage prior to the removal of the honeycomb body from a shaping 
mold. The mold serves to form a honeycomb body, wherein at least one 
layered stack comprising a plurality of at least partially structured 
sheets is introduced into the mold for forming a honeycomb body and is 
held and wound around in the mold by a winding device in a central region. 
The advantage of this embodiment of the process is that the plastic 
deformation operation follows immediately after the honeycomb body is 
formed in the mold. This alternative form of the process can be integrated 
within a honeycomb body production procedure. 
In accordance with an additional feature of the invention, the plastic 
deformation is effected during the removal of the honeycomb body from the 
mold. With such a procedure, two process steps, namely the removal of the 
honeycomb body from the mold and producing the plastic deformation, are 
integrated to constitute a joint step in the process. By virtue of that 
integration of the plastic deformation operation within the removal of the 
honeycomb body from the mold, no additional time is required for effecting 
plastic deformation as that operation is implemented in situ with the step 
of removing the honeycomb body from the mold. 
Effecting plastic deformation of at least a part of the sheets in the 
region of a mandrel passage prior to the removal of the honeycomb body 
from the mold or during the removal of the honeycomb body from the mold 
also has the advantage that the honeycomb body can adopt a position which 
is defined in relation to the mandrel passages, in respect of a bar punch 
or ram which is used for producing the plastic deformation of at least a 
part of the sheets. There is no need for the honeycomb body to be 
positioned for implementing plastic deformation. 
Although it is necessary under some circumstances to position a honeycomb 
body which is introduced into a tubular casing in order to be able to 
effect plastic deformation of at least a part of the sheets in the region 
of the mandrel passage, it may be desirable to effect the deformation on 
the honeycomb body in a tubular casing. A honeycomb body which is 
introduced into a tubular casing and which was possibly subjected to a 
brazing operation has substantially reached its final position in the 
tubular casing. After the honeycomb body has been introduced into the 
tubular casing, the honeycomb body is relieved of stress so that the free 
cross-section of the mandrel passage can be larger than the cross-section 
of the mandrel passage in a honeycomb body which is still disposed in a 
shaping mold. Therefore, with both alternative forms of the process, care 
is to be taken to ensure that the plastic deformation is sufficiently 
great so that the cross-section of the mandrel passage is closed. 
Preferably the deformation operation is effected during the introduction of 
the honeycomb body into a tubular casing. This means that two production 
steps are combined into one step in the process, whereby the time required 
for production of the honeycomb body is not increased. 
With the above and other objects in view there is also provided, in 
accordance with the invention, a honeycomb body, comprising: 
a plurality of at least partially structured sheet metal layers forming a 
plurality of passages through which a fluid can flow in a flow direction; 
at least one of said passages being a mandrel passage having a 
cross-section determined by a mandrel of a winding device; 
a free flow cross-section of said mandrel passage being closed in a portion 
along the flow direction by plastic deformation of said sheet metal layers 
in a region of said mandrel passage. 
The cross-section of the mandrel passage prior to deformation is 
essentially determined by the mandrel or bar of the winding device. The 
free flow cross-section of the mandrel passage is closed at least in a 
portion along the flow direction of an exhaust gas by plastic deformation 
of at least a part of the sheets in the region of the mandrel passage. The 
sheets of the honeycomb body themselves form the closure for the mandrel 
passage so that it is possible to omit additional closure means. This 
configuration of the honeycomb body also provides that the cross-section 
of the mandrel passage no longer has a formative influence on the 
operating performance of the honeycomb body. 
With the above and other objects in view there is also provided, in 
accordance with the invention, a device for closing a free cross-section 
of a mandrel passage formed in a honeycomb body, the honeycomb body having 
a plurality of at least partially structured sheet metal layers defining a 
multiplicity of flow passages through which a fluid can flow along a flow 
direction and the mandrel passage being formed by a mandrel of a winding 
device forming the honeycomb body, the device comprising: 
a deformation punch for plastically deforming at least a part of the sheet 
metal layers in a region of the mandrel passage and closing a free flow 
cross-section of the mandrel passage at least in a portion thereof along 
the flow direction; and 
a counter-holding means opposite said deformation punch, said deformation 
punch and said counter-holding means being movable relative to each other. 
A preferred embodiment of the device is one in which the deformation punch 
has a substantially V-shaped end portion. With that punch the sheets are 
bent towards each other so that the mandrel passage is closed. Preferably 
the configuration of the deformation punch is such that it has a 
substantially hollow end portion, in particular the end portion has a 
hollow conical shape which enlarges towards a free end. In a most 
preferred embodiment it is a hollow cone. 
The plastic deformation is further facilitated where the end portion of the 
deformation punch has a substantially sharp-edged rim. Upon the insertion 
of the deformation punch into the honeycomb body the rim cuts into the 
sheets and the cut-in portions are bent and possibly pressed together by 
the V-shaped configuration of the end portion. The fact that the punch 
cuts into the sheets facilitates the deformation procedure, while adjacent 
sheets are not influenced by the deformation or are so influenced only to 
a negligible extent. 
In accordance with again another feature of the invention, there is 
provided an apparatus for the production of a honeycomb body as outline 
above, whereby the apparatus comprises the afore-mentioned device. 
More specifically, the apparatus has a mold which has a preferably 
circumferentially extending outer flange which is releasably connected to 
a base plate formed with at least one passage opening extending 
substantially transversely with respect to the base plate, and a winding 
device. The deformation punch can be introduced into the mold through the 
passage opening so that deformation can be effected prior to removal of 
the honeycomb body from the mold. In that case, the deformation punch is 
introduced into the mold through the opening. 
In accordance with again another feature of the invention, the apparatus 
has a mold with an ejector punch which can be passed through an opening in 
the base plate. The ejector punch also carries at least one deformation 
punch. That configuration of the apparatus provides that the deformation 
operation is effected during an operation for removal of the honeycomb 
body from the mold. 
In accordance with a concomitant feature of the invention, the apparatus 
has a tubular casing punch by which a tubular casing can be pushed onto 
the honeycomb body. The tubular casing punch has at least one deformation 
punch. The mandrel passages are closed by the deformation punch while the 
tubular casing is slipped onto the honeycomb body. 
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 
process and apparatus for the production of a honeycomb body of twisted 
sheet metal layers, 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 
Referring now to the figures of the drawing in detail and first, 
particularly, to FIG. 1 thereof, there is seen a metal honeycomb body 1 
having a plurality of at least partially structured sheets forming a 
plurality of passages through which a fluid can pass. The honeycomb body 1 
is disposed in a tubular casing 10. The cross-section of the honeycomb 
body is substantially circular. A deformation punch or ram 6 is located 
opposite an axial end face 5 of the honeycomb body. The deformation punch 
6 can be reciprocated in the longitudinal (i.e. axial) direction. The 
displacement travel of the deformation punch 6 is such that it can engage 
into the honeycomb body 1 with its end portion 7 which is adjacent to the 
end face 5 of the honeycomb body 1. 
The honeycomb body 1 is a monolithic structure formed of a plurality of at 
least partially structured metal sheets or sheet metal layers. As shown by 
the exemplary detail of FIG. 3, the honeycomb body 1 is formed from smooth 
sheets 3 and corrugated sheets 4. The smooth sheets 3 and the corrugated 
sheets 4 define a plurality of passages 2 through which a fluid can pass. 
It is apparent from the view in FIG. 3 that the honeycomb body has a 
mandrel passage 9. The mandrel passage 9 is defined by a smooth sheet 3. 
That is not necessarily the case. The free flow cross-section of the 
mandrel passage 9 is larger in comparison with the free cross-section of a 
passage 2. 
The deformation punch 6 is partially driven into the honeycomb body 1 in 
order to close the mandrel passage 9. FIG. 2 shows a snapshot of the 
position of the deformation punch 6 within the honeycomb body 1. The 
deformation punch 6 has a substantially V-shaped end portion 7. As an 
alternative to the V-shaped configuration of the end portion 7 the 
deformation punch may also be a hollow taper which enlarges towards the 
free end. In particular the end portion has a hollow-conical 
configuration. 
The end portion 7 has a substantially sharp-edged rim 8. When the 
deformation punch 6 penetrates into the honeycomb body 1 the sharp-edged 
rim 8 partially severs the sheets 3, 4. The sheets 3, 4 which are within 
an imaginary boundary line defined by the rim 8 are plastically deformed 
so that due to the plastic deformation they close the cross-section of the 
mandrel passage 9 (cf. FIG. 2). 
In the embodiment shown in FIG. 1, the honeycomb body 1 is already disposed 
in the tubular casing 10. The tubular casing 10 is pushed onto the 
honeycomb body 1 by means of a tubular casing punch or ram 11, as is shown 
in FIG. 4. Two deformation punches 6 are arranged at a spacing relative to 
each other at an end face 12 of the tubular casing punch 11. The end face 
12 is thereby aligned adjacent the end face 5 of the honeycomb body 1. 
When the tubular casing 10 is pushed onto the honeycomb body 1 the mandrel 
passages of the honeycomb body 1 are closed by plastic deformation at 
least of a part of the sheets in the region of each mandrel passage. The 
free flow cross-section of the mandrel passage is thereby closed at least 
in a portion along the flow direction of an exhaust gas. 
Instead of pushing the tubular casing onto the honeycomb body, the 
honeycomb body can be pushed into the tubular casing. In that case at 
least one deformation punch can be arranged on a non-illustrated punch 
member by which the honeycomb body is pushed into the tubular casing. 
Alternatively or in addition, at least one deformation punch can be 
arranged on a counter-holding means forming a support abutment for the 
tubular casing. The structure in principle of such an apparatus is 
substantially the same as the apparatus illustrated in FIG. 4, with the 
tubular casing punch 11 forming a stationary counter-holding means. 
FIGS. 5 and 6 each show a respective embodiment of an apparatus for the 
production of a honeycomb body. The configuration of the apparatuses 
substantially corresponds to the configuration of the apparatus known from 
German published application DE 195 22 327 A1. The content of that 
disclosure is incorporated herein. FIG. 5 shows a shaping mold or matrix 
13 defined by a wall 14. The wall 14 has a plurality of openings 15 
through which a stack of layered smooth and corrugated sheets can be 
introduced into the internal space of the mold 13. The wall 14 is 
connected by way of a flange 16 to a base plate 17. A winding device with 
bars which project into the interior of the mold 13 is not shown. 
An opening 18 is formed in the base plate 17 through which an ejector punch 
19 connected to an actuating rod 20 can be introduced into the interior of 
the mold 13. The punch 19 has deformation punches 6 at its end face 22 
towards the interior of the mold 13. Actuation of the punch 19 in the 
direction of the longitudinal axis 21 of the mold 13 causes a honeycomb 
body which is disposed in the mold 13 to be urged out of the interior of 
the mold 13. During that operation the mandrel passages of the honeycomb 
body are simultaneously closed by the deformation punches. 
FIG. 6 shows a further embodiment of an apparatus for the production of a 
honeycomb body. The structure in principle of the apparatus shown in FIG. 
6 corresponds to that illustrated in FIG. 5. The same components of the 
apparatus are denoted by the same references. Unlike the apparatus shown 
in FIG. 5 the embodiment illustrated in FIG. 6 has an ejector punch 19 
formed with passage openings 23 through each of which can be passed a 
respective deformation punch 6. The deformation punches 6 are disposed on 
a common carrier 24. The carrier 24 with the deformation punches 6 is 
mounted to be reciprocable in such a way that the deformation punches 6 
can be guided through the passage openings 23 whereby the deformation 
punches 6 are partially introduced into a honeycomb body within the mold. 
The free flow cross-section at least of the mandrel passage is partly 
closed, i.e., along a portion in the direction of flow of the exhaust gas. 
After the mandrel passages have been closed the carrier can be returned to 
its starting position. The ejector punch 19 then conveys the honeycomb 
body out of the interior of the mold 13.