U.S. patent application number 10/397231 was filed with the patent office on 2003-10-02 for holding material for catalytic converter.
Invention is credited to Anji, Toshiyuki, Mochida, Takahito, Sakane, Tadashi, Tanaka, Masafumi.
Application Number | 20030185723 10/397231 |
Document ID | / |
Family ID | 27800556 |
Filed Date | 2003-10-02 |
United States Patent
Application |
20030185723 |
Kind Code |
A1 |
Anji, Toshiyuki ; et
al. |
October 2, 2003 |
Holding material for catalytic converter
Abstract
A holding material is provided for a catalytic converter having
a catalyst carrier, a casing for receiving the catalyst carrier.
The holding material is interposed in a gap between the catalyst
carrier and the casing while wound on the catalyst carrier. The
holding material is constituted by a sewn product of a mat material
formed by collection of not smaller than 100 cc/5 g by wet volume
of inorganic fiber without use of any binder.
Inventors: |
Anji, Toshiyuki; (Tokyo,
JP) ; Tanaka, Masafumi; (Tokyo, JP) ; Sakane,
Tadashi; (Hamamatsu-shi, JP) ; Mochida, Takahito;
(Hamamatsu-shi, JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
1100 N GLEBE ROAD
8TH FLOOR
ARLINGTON
VA
22201-4714
US
|
Family ID: |
27800556 |
Appl. No.: |
10/397231 |
Filed: |
March 27, 2003 |
Current U.S.
Class: |
422/179 |
Current CPC
Class: |
D04H 1/4209 20130101;
F01N 3/2853 20130101; D04H 1/52 20130101; D04H 1/45 20130101 |
Class at
Publication: |
422/179 |
International
Class: |
F01N 007/14 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2002 |
JP |
P. 2002-095937 |
Claims
What is claimed is:
1. A holding material for a catalytic converter, interposed in a
gap between a catalyst carrier and a casing receiving the catalyst
carrier, comprising: a mat material formed of not smaller than 100
cc/5 g by wet volume of inorganic fiber without use of any binder
and sewn with sewing thread.
2. The holding material according to claim 1, wherein the mat
material is sewn at intervals of a sewing pitch of 3 mm to 30
mm.
3. The holding material according to claim 1, wherein the sewing
thread is made of one of metal fiber sewing thread, inorganic fiber
sewing thread and organic fiber sewing thread.
4. The holding material according to claim 1, wherein the sewing
thread is made of at least one member selected from the group
consisting of alumina fiber, mullite fiber, silica-alumina fiber,
silica fiber, glass fiber, rock wool and biodegradable fiber.
5. The holding material according to claim 1, wherein the sewing
thread is made of a mixture of at least two members selected from
the group consisting of metal fiber, inorganic fiber, and organic
fiber.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a catalyst carrier holding
material used in a catalytic converter, for example, for purging
exhaust gas emitted from an automobile.
[0003] 2. Description of the Related Art
[0004] As known commonly, a catalytic converter for purging exhaust
gas is loaded in a vehicle such as an automobile in order to remove
detrimental components such as carbon monoxide, hydrocarbon and
nitrogen oxides from exhaust gas emitted from an engine of the
vehicle. Generally, as shown in FIG. 2 which is a sectional view,
the catalytic converter has a catalyst carrier 1 shaped like a
cylinder, a metal casing 2 for receiving the catalyst carrier 1,
and a holding material 3 interposed in a gap between the catalyst
carrier 1 and the casing 2 while mounted on the catalyst carrier
1.
[0005] Generally, the catalyst carrier 1 has a cylindrical
honey-comb molded material, for example, made of cordierite, and a
precious metal catalyst carried by the molded material. It is
therefore necessary that the holding material 3 interposed in a gap
between the catalyst carrier 1 and the casing 2 has a function for
holding the catalyst carrier 1 safely to prevent the catalyst
carrier 1 from being damaged by collision with the casing 2 due to
vibration or the like during the running of the automobile, and a
function for sealing the catalyst carrier 1 to prevent non-purged
exhaust gas from leaking out through the gap between the catalyst
carrier 1 and the casing 2. Therefore, at the present time, there
is widely used a so-called mat type holding material which is
constituted by inorganic fiber such as alumina fiber, mullite fiber
or other ceramic fiber collected into a predetermined thickness
while bound with an organic binder to thereby provide adequate
elasticity.
[0006] Examples of the organic binder generally used in the holding
material 3 include rubber compounds, water-soluble organic
high-molecular compounds, thermoplastic resins, and thermosetting
resins. It is necessary to make the holding material 3 thin to a
certain degree because the holding material 3 can be hardly mounted
on the catalyst carrier 1 and hardly attached to the casing 2 if
the holding material 3 is too thick. Therefore, the holding
material 3 generally used is formed so that the ratio of the amount
of the organic binder to the total amount of the holding material
is in a range of from 5% by weight to 10% by weight or about 12% by
weight at maximum.
[0007] The catalyst carrier 1 has been however recently heated to
about 1,000.degree. C. in order to improve purging efficiency. For
this reason, the organic binder listed above is decomposed and
burned out easily, so that CO.sub.2, CO and various kinds of
organic gases are produced. Particularly, a great deal of gas is
produced in an early stage of the start of the catalytic converter.
Regulation of exhaust emission control has become more and more
rigid. There is a possibility that the amount of exhaust gas may be
over a regulated value because of CO.sub.2, etc. derived from the
organic binder. On the other hand, electronic engine control has
been recently developed. The presence of CO.sub.2 having no
relation to exhaust gas originally may cause malfunctions of
exhaust sensors to exert a bad influence on the electronic engine
control. To prevent this drawback, a maker carries out a baking
process to burn out the organic binder before shipping. The baking
process is a heavy burden imposed on the maker. This is a major
issue.
[0008] Reduction in quantity of the organic binder is also
conceived. In this case, force of binding the inorganic fiber is
however weakened in accordance with the reduction in quality of the
organic binder. For this reason, it is necessary to make the
holding material 3 thick, so that there is a problem that
assembling property is worsened.
SUMMARY OF THE INVENTION
[0009] As described above, the related-art holding material has
various problems resulting from the organic binder. Therefore, an
object of the invention is to provide a holding material for a
catalytic converter in which inorganic fiber can be bound well even
without use of any organic binder so that the thickness of the
holding material can be kept equal to that of a related-art holding
material.
[0010] The present inventors have made eager examination to achieve
the foregoing object. As a result, it has been found that the
thickness of the holding material can be suppressed without use of
any organic binder when continuous inorganic fiber is collected
into a mat shape and sewn. Thus, the invention is accomplished.
[0011] That is, in order to achieve the foregoing object, the
invention provides a holding material for a catalytic converter
having a catalyst carrier, a casing for receiving the catalyst
carrier, and a holding material interposed in a gap between the
catalyst carrier and the casing while wound on the catalyst
carrier, the holding material being constituted by a sewn product
of a mat material formed by collection of not smaller than 100 cc/5
g by wet volume of inorganic fiber without use of any binder.
[0012] The wet volume is an index for providing a fiber length and
is calculated by a method having the following steps:
[0013] (1) weighing 5 g of a dried fiber material by a weigher with
accuracy of two or more decimal places;
[0014] (2) putting the weighed fiber material into a glass beaker
having a weight of 500 g;
[0015] (3) putting about 400 cc of distilled water at a temperature
of 20-25.degree. C. into the glass beaker prepared in the step (2)
and dispersing the fiber material into the distilled water (by an
ultrasonic cleaner if necessary) while stirring carefully by a
stirrer so that the fiber material is not cut;
[0016] (4) transferring the content of the beaker prepared in the
step (3) into a 1,000 ml graduated measuring cylinder and adding
distilled water into the graduated measuring cylinder up to the
scale of 1,000 cc;
[0017] (5) ten-times repeating a process of stirring the content of
the graduated measuring cylinder prepared in the step (4) by
turning the graduated measuring cylinder upside down while blocking
an opening of the graduated measuring cylinder with the palm of a
hand or the like carefully to prevent water from leaking out;
[0018] (6) measuring the sedimentation volume of fiber by eye
observation after placing the graduated measuring cylinder quietly
under room temperature for 30 minutes after the stop of the
stirring; and
[0019] (7) applying the aforementioned procedure to three samples
and taking an average of the measured values as a measured
value.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a sectional view showing a holding material
according to the invention.
[0021] FIG. 2 is a sectional view typically showing a catalytic
converter.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] A holding material according to the invention will be
described below in detail.
[0023] As shown typically in FIG. 1 which is a sectional view, the
holding material 3 according to the invention is formed in such a
manner that a mat material 30 formed by collection of inorganic
fiber without use of any binder is sewn with sewing thread 31.
[0024] The kind of the inorganic fiber for forming the mat material
30 is not limited. For example, alumina fiber, mullite fiber or
other ceramic fiber may be used suitably. More specifically, the
material preferably used as the alumina fiber is fiber, for
example, containing 90% by weight or more of Al.sub.2O.sub.3 (and
SiO.sub.2 as a residual component) and having low crystallinity in
terms of X-ray crystallography. The material preferably used as the
mullite fiber is a mullite composition, for example, having an
Al.sub.2O.sub.3/SiO.sub.2 weight ratio of about 72/28 to about
80/20 and having low crystallinity in terms of X-ray
crystallography. Examples of the other ceramic fiber may include
silica-alumina fiber, and silica fiber. Any known material used in
a holding material in the related art may be used as the other
ceramic fiber. In addition, glass fiber, rock wool or biodegradable
fiber may be mixed with the inorganic fiber.
[0025] In the invention, there is used continuous fiber selected
from these kinds of inorganic fiber and having a wet volume of not
smaller than 100 cc/5 g, preferably not smaller than 400 cc/5 g. If
inorganic fiber having a wet volume smaller than 100 cc/5 g is
used, individual fiber pieces are too short to keep both density
and thickness at initial values because fiber pieces are apt to
drop out through gaps of the sewing thread 31 according to the
sewing pitch (the distance between adjacent portions of sewing
thread 31) even in the case where sewing is performed. In addition,
because fiber pieces are little intertwined with one another, there
is a possibility that delamination may occur to reduce both holding
performance and sealing performance when the holding material is
mounted in the casing. Incidentally, the upper limit of the wet
volume is not particularly provided but is generally selected to be
in a range of from 400 cc/5 g to 1,000 cc/5 g.
[0026] Metal fiber sewing thread, inorganic fiber sewing thread or
organic fiber sewing thread can be used as the sewing thread
31.
[0027] Preferred examples of the sewing thread include SUS fiber
sewing thread (such as Naslon sewing thread), alumina fiber sewing
thread, mullite fiber sewing thread, silica-alumina fiber sewing
thread, silica fiber sewing thread, glass fiber sewing thread, rock
wool sewing thread, biodegradable fiber sewing thread, carbon fiber
sewing thread, cotton thread, acrylic fiber sewing thread,
polyethylene fiber sewing thread, polyethylene terephthalate fiber
sewing thread, aramid fiber sewing thread, aromatic polyamide fiber
sewing thread, and polyoxybenzole fiber sewing thread. Sewing
thread made of a mixture of two kinds of fiber selected from the
group consisting of metal fiber, inorganic fiber and organic fiber
can be also used preferably. The mixed fiber sewing thread is
advantageous to both production aspect and functional aspect
because strength of metal fiber, elasticity (spring characteristic)
of inorganic fiber and flexibility of organic fiber can be mixed
synergically.
[0028] Because the organic fiber sewing thread is decomposed at a
high temperature, the same gas as produced from an organic binder
used in a related-art holding material is produced from the organic
fiber sewing thread. The amount of the organic fiber sewing thread
used for sewing is however considerably small compared with the
amount of the binder used, so that the gas produced from the
organic fiber sewing thread is practically insignificant. Further,
although the inorganic fiber also contains a binder, the amount of
the binder contained in the inorganic fiber is further smaller.
Accordingly, a holding material substantially containing no organic
component can be obtained when the holding material is heated after
sewing as will be described later. In consideration of the organic
component, it may be said that the metal fiber sewing thread is the
most preferable.
[0029] The sewing pitch is determined variously in accordance with
the length (wet volume) of the inorganic fiber for forming the mat
material 30 and the thickness and density of the resulting holding
material but is preferably selected to be in a range of from 3 mm
to 20 mm. Particularly when the organic fiber sewing thread is
used, the amount of the organic fiber sewing thread used increases
as the pitch decreases. Accordingly, it is preferable from the
point of view of suppressing the organic component that the pitch
is selected to be large to a certain degree.
[0030] The holding material 3 according to the invention is
produced as follows. First, inorganic fiber is collected without
use of any binder to thereby produce a mat material 30 having a
predetermined thickness. On this occasion, various kinds of
additives (except any binder) as mixed with the related-art holding
material may be mixed with the mat material 30. Then, the mat
material 30 is compressed into a thickness of the finally produced
holding material and sewn while the compressed state is kept by
temporal tacking with nonwoven fabric or the like if necessary.
Thus, the holding material is obtained. Incidentally, when the mat
material 30 is sewn with inorganic fiber sewing thread, it is
preferable that the whole of the mat material 30 is heated after
sewing to remove the binder contained in the fiber.
[0031] As shown in FIG. 2, the holding material 3 formed in the
aforementioned manner according to the invention is wound on the
catalyst carrier 1 and interposed between the gap between the
catalyst carrier 1 and the casing 2 in the same manner as in the
related art.
EXAMPLE
[0032] The invention will be described below more specifically in
connection with the following Example but the invention is not
limited thereto at all.
[0033] (Production of Holding Material)
[0034] Alumina fiber having a wet volume of 800 cc/5 g was
collected without use of any binder to form a mat material 100 mm
in width, 314 mm in length, 20 mm in thickness and 1,000 g/m.sup.2
in grammage (areal density). Then, the mat material was compressed
into a thickness of 7.5 mm, temporally tacked with nonwoven fabric
and sewn with Naslon sewing thread at intervals of a pitch of 10 mm
to obtain a holding material.
[0035] (Mount Test)
[0036] The holding material was wound on a cordierite catalyst
carrier of a cylindrical honey-comb structure having an outer
diameter of 100 mm and a length of 120 mm and then mounted in a
stainless steel casing to produce a catalytic converter. The
produced catalytic converter was connected to an exhaust pipe of a
gasoline engine. Exhaust gas was passed through the catalytic
converter. Gas emitted from the catalytic converter during the
passage of the exhaust gas was analyzed. As a result, CO.sub.2, CO
and organic gas were not detected even just after the passage of
the exhaust gas. In addition, non-purged exhaust gas supposed to be
derived from leakage of the holding material was not detected even
during the passage of the exhaust gas, so that good sealing
performance was obtained.
[0037] As described above, according to the invention, there can be
obtained a holding material containing no organic component or
containing a very small amount of organic component even in the
case where the organic component is contained, so that various
problems caused by the related-art holding material using an
organic binder can be solved.
* * * * *