BACKGROUND OF THE INVENTION
Field of the invention
[0001] 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
[0002] Currently, ceramic honeycomb catalytic converters are widely used as automobile exhaust
gas purifying devices.
[0003] 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.
[0004] 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.
[0005] Normally, a ceramic honeycomb catalytic converter is manufactured as shown in Fig.
3.
[0006] First, the carrier manufacturer packages a ceramic carrier 10 (ceramic honeycomb
structure) which has passed inspection, and sends it to a catalyst manufacturer.
[0007] The catalyst manufacturer unpacks this, performs processes such as causing the ceramic
carrier 10 (ceramic honeycomb structure) to hold the catalyst (i.e., 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.
[0008] 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).
[0009] 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.)).
[0010] In order to solve this problem, the present inventors have 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).
[0011] However, the above canning structure has been 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.
[0012] US-A-3959865 describes a catalyst support which is resiliently supported in a casing
by a cellular foam. Resilient thermally resistant inorganic paper layers are provided
between the foam and the casing and between the foam and the catalyst support. The
paper layers permit formation of the foam
in situ. It is mentioned that it is possible to mount the support and deposit catalyst on
it.
SUMMARY OF THE INVENTION
[0013] The present invention has been made in the 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, in the catalyst carrying process, in the canning process,
and in handling in each of the processes, without allowing the holding material to
carry expensive catalyst at the time of carrying the catalyst.
[0014] According to the present invention, a canning structure is provided as set out in
claim 1.
[0015] The impermeable film preferably circles at least the portion where the ceramic honeycomb
structure and the holding material are in contact.
[0016] Also, 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.
[0017] Further, in 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).
[0018] Here, the impermeable film is preferably also water-repellent.
[0019] Further, in the present invention, the holding material is preferably a non-intumescent
ceramic fiber mat.
[0020] Also, according to the present invention, a catalyst carrying method is provided
as set out in claim 9.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021]
Fig. 1A is a schematic perspective view illustrating an example of the canning structure
according to the present invention;
Fig. 1B is a plan view of that shown in Fig. 1A;
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 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
Fig. 4 is a schematic explanatory diagram illustrating an example of a ceramic honeycomb
catalytic converter.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] The canning structure according to the present invention is 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.
[0023] 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 carry
expensive catalyst at the time of carrying the catalyst.
[0024] The present invention will be described in further detail with reference to the drawings.
[0025] Figs. 1A through 1C illustrate an example of the canning structure according to the
present invention, wherein Fig. 1A is a schematic perspective view, Fig. 1B is a plan
view, and Fig. 1C is a longitudinal-sectional view.
[0026] As shown in Figs. 1A through 1C, the canning structure according to the present invention
comprises a canning structure comprises a ceramic honeycomb structure 10; said honeycomb
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 material 13.
[0027] At this time, with the canning 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.
[0028] 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).
[0029] Also, with the canning 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.
[0030] Also, the outer diameter L
2 of the protrusions of the impermeable film are preferably greater than the outer
diameter L
1 of the ceramic honeycomb structure.
[0031] Thus, the catalyst slurry can be readily prevented from 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.
[0032] Also, the shape of the impermeable film used in the present invention is preferably
cylindrical.
[0033] 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.
[0034] 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.
[0035] 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.
[0036] 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).
[0037] 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).
[0038] Here, the impermeable film used with the present invention is combustible.
[0039] This is in order to easily remove the impermeable film which has become no longer
necessary, by a thermal process (500 to 700° C) following carrying the catalyst (catalyst
coating).
[0040] 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.
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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 reliability.
[0045] 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).
[0046] Also, the holding material used with the present invention is preferably a non-intumescent
ceramic fiber mat.
[0047] 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.
[0048] 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 µm or greater by less than 6 µm, such
that application of an initial plane pressure of 2 kgf/cm
2 at room temperature and then raising the temperature to 1,000°C results in generation
of a plane pressure of at least 1 kgf/cm
2, and also has the compression properties in that there is little increase or decrease
within the actual usage temperature range of the catalytic converter.
[0049] 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).
[0050] 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.
[0051] 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.
[0052] 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.
1A through 1C), which is then packaged and sent to a catalyst manufacturer.
[0053] 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, which is then packaged
and sent to a canning manufacturer.
[0054] 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.
[0055] 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.
[0056] 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).
[0057] 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.
[0058] 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.
Embodiment
[0059] 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/cm
2, was prepared. An impermeable film (material: polyethylene) 0.03 mm in thickness
was wrapped on the perimiter thereof, following which a non-intumescent ceramic fiber
mat ("MAFTEC" (product name), manufactured by MITSUBISHI CHEMICAL CORPORATION) of
1,200 g per 1 m
2 was further wrapped thereupon, as a holding material.
[0060] 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.
[0061] 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.
[0062] 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.
[0063] 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.
[0064] Also, absolutely no cracking or chipping of the ceramic honeycomb structures was
observed at any point in the above manufacturing process.
First Comparative Example
[0065] A canning structure was manufactured under the same conditions as the 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.
[0066] 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.
[0067] Incidentally, absolutely no cracking or chipping of the ceramic honeycomb structures
was observed at any point in the above manufacturing process.
Second Comparative Example
[0068] 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/cm
2, were prepared, and were placed in the ceramic honeycomb catalytic converter (pressing
canning) manufacturing process shown in Fig. 3.
[0069] Consequently, the rate of cracking or chipping of the ceramic honeycomb structures
throughout the above manufacturing process reached 25%.
[0070] 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.
1. Einblechungsstruktur umfassend eine Keramik-Wabenstruktur (10), die nicht mit einem
Katalysator bestückt worden ist, ein Metallgehäuse (11) und ein Haltematerial (13),
wobei die Keramik-Wabenstruktur (10) in das Metallgehäuse eingeblecht ist und durch
das Haltematerial (13) darin gehalten ist, und wobei ein undurchlässiger Film (60)
zwischen der Keramik-Wabenstruktur (10) und dem Haltematerial (13) bereitgestellt
ist,
dadurch gekennzeichnet, dass der undurchlässige Film (60) brennbar ist.
2. Einblechungsstruktur nach Anspruch 1, worin der undurchlässige Film (60) zumindest
jenen Abschnitt umgibt, in dem die Keramik-Wabenstruktur (10) und das Haltematerial
(13) in Kontakt sind.
3. Einblechungsstruktur nach Anspruch 1 oder Anspruch 2, worin der undurchlässige Film
(60) an beiden Stirnflächen der Keramik-Wabenstruktur (10) 10 mm oder mehr in die
Gasströmungsrichtung übersteht.
4. Einblechungsstruktur nach Anspruch 3, worin der äußere Durchmesser der Überstände
(62) des undurchlässigen Films (60) größer als der äußere Durchmesser der Keramik-Wabenstruktur
(10) ist.
5. Einblechungsstruktur nach einem der Ansprüche 1 bis 4, worin die Form des undurchlässigen
Films (60) zylindrisch ist.
6. Einblechungsstruktur nach einem der Ansprüche 1 bis 5, worin die Dicke des undurchlässigen
Films (60) 0,1 mm oder weniger beträgt.
7. Einblechungsstruktur nach einem der Ansprüche 1 bis 6, worin der undurchlässige Films
(60) wasserabweisend ist.
8. Einblechungsstruktur nach einem der Ansprüche 1 bis 7, worin das Haltematerial (13)
eine nicht schwellende Keramikfasermatte ist.
9. Verfahren zur Bereitstellung eines Katalysators auf einer Keramik-Wabenstruktur (10),
die in ein Metallgehäuse (11) eingeblecht und durch ein Haltematerial (13) darin gehalten
ist;
worin ein undurchlässiger Film (60) zwischen der Keramik-Wabenstruktur (10) und dem
Haltematerial (13) bereitgestellt ist und eine Katalysatoraufschlämmung ausschließlich
auf die Keramik-Wabenstruktur-Seite des undurchlässigen Films (60) gegossen wird,
wodurch verhindert wird, dass das Haltematerial (13) den Katalysator trägt, sodass
ausschließlich die Keramik-Wabenstruktur (10) den Katalysator trägt;
dadurch gekennzeichnet, dass der undurchlässige Film (60) brennbar ist.