Note: Descriptions are shown in the official language in which they were submitted.
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CANNING STRUCTURE AND CATALYST CARRYING METHOD THEREOF
BACKGROUND OF THE INVENTION
Field of the invention
The present invention relates to a canning structure for
a catalytic converter which is a device for purifying harmful
combustion gases exhausted from internal combustion engines and
the like, and to a catalyst carrying method thereof.
Description of the Related Art
Currently, ceramic honeycomb catalytic converters are
widely used as automobile exhaust gas purifying devices.
Environmental issues in recent years along with even
stricter exhaust gas restrictions are requiring that catalysts
be able to function immediately following starting the engine
when the exhaust gas is still cool, i.e., cold starts.
Accordingly, a step being taken is to reduce the thickness
of the partitions of the catalyst carrier to 1/2 to 1/6 of the
conventional thickness , so as to lower the thermal capacity of
the catalyst carrier and speed up the temperature rising of the
catalyst carrier, along with improving engine performance due
to decrease of pressure loss.
Normally, a ceramic honeycomb catalytic converter is
manufactured as shown in Fig. 3.
First , the carrier manufacturer packages a ceramic carrier
10 (ceramic honeycomb structure) which has passed inspection,
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and sends it to a catalyst manufacturer.
The catalyst manufacturer unpacks this, performs processes
such as causing the ceramic carrier 10 (ceramic honeycomb
structure ) to hold the catalyst ( i . a . , catalyst coating ) , thermal
processing, inspection, etc., thereby forming a catalyst carrier
25 ( ceramic honeycomb catalyst carrier ) , which is then packaged
and sent to a canning manufacturer.
The canning manufacturer unpacks this and attaches a
holding material 13 to the catalyst carrier 25 so as to fix within
a metal case 11 by compressed fixing (canning) , thus forming a
canning catalyst carrier 30, following which joining parts such
as a cone portion 17 and flange 18 and the like are welded to
the canning catalyst carrier 30 as necessary, thus completing
a catalytic converter 1 (ceramic honeycomb catalytic converter)
(see Fig. 4).
Now, in the event that a ceramic honeycomb structure having
the thickness of the partitions at around 1/2 to 1/6 of the
conventional thickness is used as the above catalyst carrier,
there has been the problem that the ceramic honeycomb structure
easily cracks or chips during tranporting, the catalyst carrying
process, the canning process, and handling in each of the
processes (e.g. , packaging, unpacking, placing on or taking off
of the mechanical facilities (conveyers, chucking, canning,
etc.)).
In order to solve this problem, the present Inventors have
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proposed a new ceramic honeycomb catalytic converter
manufacturing process using a canning structure (an article
wherein a ceramic honeycomb structure before carrying the
catalyst is fixed inside a metal case beforehand, using a holding
material).
However, the above canningstructure hasbeen uneconomical,
since at the time of carrying the catalyst (i.e., catalyst
coating) , expensive catalyst is carried by not only the ceramic
honeycomb structure but also the holding material which does not
take part in the catalytic reaction with the exhaust gas.
SUMMARY OF THE INVENTION
The present invention has been made in light of the present
situation, and accordingly, it is an object thereof to provide
a canning structure and a catalyst carrying method thereof,
capable of preventing chipping and cracking of the ceramic
honeycomb structure at the time of transporting, the catalyst
carrying process, the canning process, and handling in each of
the processes, without allowing the holding material to carry
expensive catalyst at the time of carrying the catalyst.
According to the present invention, a canning structure
is provided which comprises a ceramic honeycomb structure before
carrying a catalyst fixed beforehand within a metal case by a
holding material; wherein an impermeable film is provided between
the ceramic honeycomb structure and the holding material.
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At this time, the impermeable film preferably circles at
least the portion where the ceramic honeycomb structure and the
holding material are in contact.
Also, according to the present invention, the impermeable
film preferably has protrusions protruding from both edge planes
of the ceramic honeycomb structure by 10 mm or more (preferably
20 mm or more, and more preferably 30 mm or more) , with the outer
diameter of the protrusions of the impermeable film being greater
than the outer diameter of the ceramic honeycomb structure.
Further, according to the present invention, the shape of
the impermeable film is preferably cylindrical, and the thickness
of the impermeable film is preferably 0.1 mm or less (preferably
0.05 mm or less, and more preferably 0.03 mm or less).
Here, the impermeable film is preferably combustible and
also water-repellent.
Further, according to the present invention, the holding
material is preferably a non-intumescent ceramic fiber mat.
Also, according to the present invention, a catalyst
carrying method is provided for a canning structure comprises
a ceramic honeycomb structure; said honeycomb structure having
been not loaded with a catalyst, a metal case and a holding
material, and said ceramic honeycomb structure being canned in
said metal case and being held by said holding material thereto;
wherein an impermeable film is provided between the ceramic
honeycomb structure and the holding material, and then a catalyst
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slurry is poured in only on the ceramic honeycomb structure side
of the impermeable film, thereby preventing the holding material
from carrying the catalyst , such that only the ceramic honeycomb
structure carries the catalyst.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. lA is a schematic perspective view illustrating an
example of the canning structure according to the present
invention;
1o Fig. 1B is a plan view of that shown in Fig. lA;
Fig. 1C is a longitudinal-sectional view of that shown in
Fig. la;
Fig. 2 is a schematic diagram illustrating an example of
the manufacturing process of the ceramic honeycomb catalytic
i5 converter using the canning structure according to the present
invention;
Fig. 3 is a schematic diagram illustrating an example of
the manufacturing process of a conventional ceramic honeycomb
catalytic converter; and
2o Fig. 4 is a schematic explanatory diagram illustrating an
example of a ceramic honeycomb catalytic converter.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The canning structure according to the present invention
25 is a canning structure comprises a ceramic honeycomb structure;
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said honeycomb structure having been not loaded with a catalyst ,
a metal case and a holding material, and said ceramic honeycomb
structure being canned in said metal case and being held by said
holding material thereto, wherein an impermeable film is provided
between the ceramic honeycomb structure and the holding material .
Thus, chipping and cracking of the ceramic honeycomb
structure can be prevented at the time of transporting, the
catalyst carrying process, the canning process, and handling in
each of the processes, without allowing the holding material to
io carry expensive catalyst at the time of carrying the catalyst.
The present invention will be described in further detail
with reference to the drawings.
Figs. lA through 1C illustrate an example of the canning
structure according to the present invention, wherein Fig. lA
i5 is a schematic perspective view, Fig. 1B is a plan view, and Fig.
1C is a longitudinal-sectional view.
As shown in Figs. lA through 1C, the canning structure
according to the present invention comprises a canning structure
comprises a ceramic honeycomb structure 10; said honeycomb
2o structure having been not loaded with a catalyst, a metal case
11 and a holding material 13 , and said ceramic honeycomb structure
being canned in said metal case and being held by said holding
material thereto, wherein an impermeable film 60 is provided
between the ceramic honeycomb structure 10 and the holding
25 material 13.
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At this time, with the caning structure according to the
present invention, the impermeable film 60 preferably circles
at least the portion where the ceramic honeycomb structure 10
and the holding material 13 are in contact, as shown in Figs.
1A through 1C.
This is to prevent the catalyst slurry containing the
catalyst component from flowing to the holding material in the
event that the above canning structure is caused to hold the
catalyst (i.e., subjected to catalyst coating).
1o Also, with the caning structure according to the present
invention, the impermeable film preferably has protrusions 62
protruding from both edge planes of the ceramic honeycomb
structure 10 by a length "a" which is 10 mm or more (preferably
20 mm or more, and more preferably 30 mm or more), as shown in
Fig. 1C.
Also, the outer diameter L2 of the protrusions of the
impermeable film are preferably greater than the outer diameter
L1 of the ceramic honeycomb structure.
Thus, the catalyst slurry can be readily prevented from
2o flowing to the holding material in the catalyst carrying process,
causing the canning structure to hold the catalyst (i.e.,
catalyst coating) can be performed in a sure manner, and the
catalyst carrying process can be optimized.
Also, the shape of the impermeable film used in the present
invention is preferably cylindrical.
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This is to allow the impermeable film to be easily provided
so as to circle the ceramic honeycomb structure, so the canning
process can be simplified, and also the perimeter of the ceramic
honeycomb structure can be seamlessly circled, so catalyst slurry
can be readily prevented from flowing out from the ceramic
honeycomb structure in a sure manner.
Also, the impermeable film used in the present invention
may be a sheet formed integrally with the ceramic fiber mat which
serves as the holding material.
Thus, the impermeable film and the holding material can
be wound onto the perimeter surface of the ceramic honeycomb
structure at the same time, so the canning process can be
simplified.
Further, the thickness of the impermeable film used with
the present invention is preferably 0.1 mm or less (preferably
0.05 mm or less, and more preferably 0.03 mm or less).
This is due to the fact that the thickness of the impermeable
film must be as thin as possible, in order to fix the ceramic
honeycomb structure in the metal case in a secure manner with
the holding material, in the event that the impermeable film is
removed from the canning structure which has carried the catalyst
(coated with the catalyst).
Here, the impermeable film used with the present invention
is preferably combustible.
This is in order to easily remove the impermeable film which
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has become no longer necessary, by a thermal process ( 500 to 700° C )
following carrying the catalyst (catalyst coating).
Also, the impermeable film used with the present invention
is preferably water-repellent , in order to prevent the catalyst
slurry from flowing to the holding material in a sure manner.
Now, while the material of the impermeable film used with
the present invention is not particularly restricted as long as
the above conditions are all met, polyethylene, nylon, etc. , are
preferably used.
Further, in addition to the above advantages, the canning
structure according to the present invention is capable of
protecting the ceramic honeycomb structure from external shock
and vibrations, and accordingly chipping and cracking of ceramic
honeycomb structures (particularly of those with thin walls
(thickness of partitions; 0.10 mm or thinner) ) can be prevented
at the time of transporting, the catalyst carrying process, the
canning process, and handling in each of the processes.
The canning structure according to the present invention
is preferably of an arrangement wherein the metal case has a
stuffing structure or a tourniquet structure.
This is because the plane pressure distribution at the time
of canning is uniform, which allows prevention of engine exhaust
gasses leaking, corrosion of the holding material due to the
exhaust gasses, and rattling, damage, etc., of the ceramic
honeycomb structure due to engine vibrations, thereby improving
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reliability.
Particularly, in the event that the metal case has a
tourniquet structure, not only is the plane pressure distribution
uniform, but canning can be performed at a constant plane pressure
regardless of irregularities in the diameter of the ceramic
honeycomb structure, which is particularly preferable for
ceramic honeycomb structures with low mechanical strengths
(particularly, those with thin walls).
Also, the holding material used with the present invention
is preferably a non-intumescent ceramic fiber mat.
This allows the maximum plane pressure at the time of
canning due to irregularities in the diameter of the ceramic
honeycomb structure to be reduced, and further to prevent damage
to ceramic honeycomb structures (particularly, those with thin
walls ) , since an excessive pressure is not generated at the time
of heating as with intumescent mats.
Now, the non-intumescent ceramic fiber mat used with the
present invention is made up of at least one selected from the
following group; alumina, mullite, silicon carbide, silicon
nitride, and zirconia. This non-intumescent ceramic fiber mat
is formed of ceramic fibers wherein the fiber diameter is 2 um
or greater by less than 6 um, such that application of an initial
plane pressure of 2 kgf /cm2 at room temperature and then raising
the temperature to 1,000°C results in generation of a plane
pressure of at least 1 kgf/cmz, and also has the compression
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properties in that there is little increase or decrease within
the actual usage temperature range of the catalytic converter.
The partition thickness of the ceramic honeycomb structure
used with the present invention is preferably 0.10 mm or thinner
(more preferably, 0.08 mm or thinner).
This is in order to cause the catalyst to function at cold
starts as well, by lowering the thermal capacity of the catalyst
carrier and speeding up the temperature rising of the catalyst
carrier, along with improving engine performance due to
decreasing pressure loss.
Next, an example of a manufacturing processing for the
ceramic honeycomb catalytic converter using the canning
structure according to the present invention will be described
with reference to Fig. 2.
First, the carrier manufacturer provides an impermeable
film 60 to the perimeter of a ceramic carrier 10 ( ceramic honeycomb
structure) which has passed inspection, further wraps the holding
material 13 , and fixes the ceramic carrier 10 within a metal case
11 (i.e. , performs canning) , thereby forming a canning structure
22 (See Figs. lA through 1C), which is then packaged and sent
to a catalyst manufacturer.
The catalyst manufacturer unpacks this, performs the
processes such as causing the canning structure 22 to carry the
catalyst (i.e., catalyst coating), thermal processing,
inspection, etc., thereby forming a canning catalyst carrier,
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which is then packaged and sent to a canning manufacturer.
Incidentally, the catalyst carrying is performed by
pouring a catalyst slurry in from the upper part of the canning
structure 22 while suctioning the catalyst slurry out from the
lower part of the canning structure 22, thereby causing the
ceramic honeycomb structure to be dipped in catalyst slurry such
that the canning structure 22 carries the catalyst.
At this time, the impermeable film provided to the
perimeter of the ceramic honeycomb structure not only prevents
the catalyst slurry from flowing out to the holding material,
but also can be easily removed in the thermal process.
The canning manufacturer unpacks this and welds joining
parts such as a cone portion 17 and flange 18 and the like to
the canning catalyst carrier 30 as necessary, thereby completing
the catalytic converter (ceramic honeycomb catalytic converter
1) (see Fig. 4).
As described above, method for manufacturing the ceramic
honeycomb catalytic converter according to the present invention
is capable of protecting the ceramic honeycomb structure from
external shock and vibrations as compared with conventional
manufacturing methods ( see Fig. 3 ) , and accordingly chipping and
cracking of ceramic honeycomb structures can be markedly
prevented at the time of transporting, the catalyst carrying
process, the canning process, and handling in each of the
processes.
r
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Next , the present invention will be described in further
detail with reference to embodiments, but it should be noted that
the present invention is by no means restricted to these
embodiments.
A ceramic carrier (ceramic honeycomb structure)
manufactured of cordierite, with a diameter of 106 mm, length
of 114 mm, partition thickness of 0.03 mm, and 233 cells/cm2,
was prepared. An impermeable film (material: polyethylene) 0.03
mm in thickness was wrapped on the perimiter thereof , following
TM
which a non-intumescent ceramic fiber mat ("MAFTEC" (product
name) , manufactured by MITSUBISHI CHEMICAL CORPORATION) of 1, 200
g per 1 m2 was further wrapped thereupon, as a holding material.
The ceramic honeycomb structure upon which the impermeable
film and holding material have been wrapped was pressed into a
stainless-steel can (metal case) with an inner diameter of 114
mm, length of 124 mm, and thickness of 1.5 mm, using a tapered
jig for pressing, thereby manufacturing the canning structure
22 shown in Fig. 1.
Incidentally, the impermeable film 60 has protrusions 62
which protrude from both edge planes of the ceramic honeycomb
structure 10 by a length "a" which is 10 mm.
Next, twenty of such canning structures 22 obtained with
the embodiment were placed in the ceramic honeycomb catalytic
converter manufacturing process shown in Fig. 2.
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Consequently, the catalyst slurry was completely prevented
from flowing out to the holding material in the catalyst carrying
(catalyst coating) process, and loss of expensive catalyst slurry
was prevented.
Also, absolutely no cracking or chipping of the ceramic
honeycomb structures was observed at any point in the above
manufacturing process.
A canning structure was manufactured under the same
conditions asthe above embodiment, without using the impermeable
film 60, and twenty of such were placed in the ceramic honeycomb
catalytic converter manufacturing process shown in Fig. 2.
Consequently, the catalyst slurry flowed out to the holding
material in the catalyst carrying process, such that 8~ of the
catalyst slurry used was carried by the holding material and hence
wasted.
Incidentally, absolutely no cracking or chipping of the
ceramic honeycomb structures was observed at any point in the
above manufacturing process.
Second Comparative Examp7~
Twenty ceramic carriers (ceramic honeycomb structures)
manufactured of cordierite, with a diameter of 106 mm, length
of 114 mm, partition thickness of 0.06 mm, and 140 cells/cm2,
were prepared, and were placed in the ceramic honeycomb catalytic
converter (pressing canning) manufacturing process shown in Fig.
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3.
Consequently, the rate of cracking or chipping of the
ceramic honeycomb structures throughout the above manufacturing
process reached 25~.
Thus, according to the canning structure and catalyst
carrying method thereof according to the present invention, the
holding material does not carry expensive catalyst at the time
of carrying catalyst, and accordingly chipping and cracking of
ceramic honeycomb structures can be prevented at the time of
transporting, the catalyst carrying process, the canning process,
and handling in each of the processes.
