U.S. patent application number 14/620507 was filed with the patent office on 2015-08-27 for honeycomb structure.
The applicant listed for this patent is NGK Insulators, Ltd.. Invention is credited to Toshihiro HIRAKAWA, Shogo HIROSE, Toshio YAMADA.
Application Number | 20150240679 14/620507 |
Document ID | / |
Family ID | 53856469 |
Filed Date | 2015-08-27 |
United States Patent
Application |
20150240679 |
Kind Code |
A1 |
YAMADA; Toshio ; et
al. |
August 27, 2015 |
HONEYCOMB STRUCTURE
Abstract
Provided is a honeycomb structure including a honeycomb
substrate having partition walls defining cells extending from an
inflow end face to an outflow end face, and plugging portions. The
cells include at least one cell group consisting of a both-end
plugged cell, an inlet cell adjacent to the both-end plugged cell,
and an outlet cell adjacent to the both-end plugged cell. The
partition walls defining the both-end plugged cell have a first
common partition wall defining both of the inlet cell and the
both-end plugged cell, and a second common partition wall defining
both of the outlet cell and the both-end plugged cell. A first
flow-through hole is formed in an end portion of the first common
partition wall on the outflow end face side, and a second
flow-through hole is formed in an end portion of the second common
partition wall on the inflow end face side.
Inventors: |
YAMADA; Toshio;
(Nagoya-City, JP) ; HIROSE; Shogo; (Nagoya-City,
JP) ; HIRAKAWA; Toshihiro; (Nagoya-City, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NGK Insulators, Ltd. |
Nagoya-City |
|
JP |
|
|
Family ID: |
53856469 |
Appl. No.: |
14/620507 |
Filed: |
February 12, 2015 |
Current U.S.
Class: |
55/523 ;
55/522 |
Current CPC
Class: |
Y02T 10/20 20130101;
F01N 3/0222 20130101; F01N 2330/48 20130101; Y02T 10/12
20130101 |
International
Class: |
F01N 3/022 20060101
F01N003/022 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 24, 2014 |
JP |
2014-033448 |
Claims
1. A honeycomb structure comprising: a honeycomb substrate having
partition walls defining a plurality of cells which form through
channels for a fluid and extend from an inflow end face as one end
face where the fluid flows in to an outflow end face as the other
end face where the fluid flows out; and plugging portions disposed
at open ends of the cells of the honeycomb substrate, wherein the
cells include at least one cell group consisting of three cells
which are a both-end plugged cell in which the plugging portions
are disposed at both open ends on the inflow end face side and the
outflow end face side, an inlet cell which is adjacent to the
both-end plugged cell and in which the plugging portion is only
disposed at the open end on the outflow end face side, and an
outlet cell which is adjacent to the both-end plugged cell and in
which the plugging portion is only disposed at the open end on the
inflow end face side, the partition walls defining the both-end
plugged cell constituting the cell group have a first common
partition wall which is a common partition wall defining both of
the inlet cell and the both-end plugged cell, and a second common
partition wall which is a common partition wall defining both of
the outlet cell and the both-end plugged cell, a first flow-through
hole is formed in an end portion of the first common partition wall
on the outflow end face side, and a second flow-through hole is
formed in an end portion of the second common partition wall on the
inflow end face side.
2. The honeycomb structure according to claim 1, wherein in a cross
section of the honeycomb substrate which is perpendicular to an
extending direction of the cells, the inlet cell, the both-end
plugged cell and the outlet cell constituting each of the at least
one cell group are arranged so that a first center which is the
center of the inlet cell, a second center which is the center of
the both-end plugged cell and a third center which is the center of
the outlet cell are positioned on a same straight line.
3. The honeycomb structure according to claim 1, wherein in the
cross section of the honeycomb substrate which is perpendicular to
the extending direction of the cells, the inlet cell, the both-end
plugged cell and the outlet cell constituting each of the at least
one cell group are arranged to form an L-shape.
4. The honeycomb structure according to claim 1, wherein an open
area of the first flow-through hole is from 0.3 to 3.5 times as
large as an average value of sectional areas in the direction
perpendicular to the cell extending direction of the inlet cell,
the both-end plugged cell and the outlet cell constituting the cell
group.
5. The honeycomb structure according to claim 2, wherein an open
area of the first flow-through hole is from 0.3 to 3.5 times as
large as an average value of sectional areas in the direction
perpendicular to the cell extending direction of the inlet cell,
the both-end plugged cell and the outlet cell constituting the cell
group.
6. The honeycomb structure according to claim 3, wherein an open
area of the first flow-through hole is from 0.3 to 3.5 times as
large as an average value of sectional areas in the direction
perpendicular to the cell extending direction of the inlet cell,
the both-end plugged cell and the outlet cell constituting the cell
group.
7. The honeycomb structure according to claim 1, wherein an open
area of the second flow-through hole is from 0.3 to 3.5 times as
large as the average value of the sectional areas in the direction
perpendicular to the cell extending direction of the inlet cell,
the both-end plugged cell and the outlet cell constituting the cell
group.
8. The honeycomb structure according to claim 2, wherein an open
area of the second flow-through hole is from 0.3 to 3.5 times as
large as the average value of the sectional areas in the direction
perpendicular to the cell extending direction of the inlet cell,
the both-end plugged cell and the outlet cell constituting the cell
group.
9. The honeycomb structure according to claim 3, wherein an open
area of the second flow-through hole is from 0.3 to 3.5 times as
large as the average value of the sectional areas in the direction
perpendicular to the cell extending direction of the inlet cell,
the both-end plugged cell and the outlet cell constituting the cell
group.
10. The honeycomb structure according to claim 1, which is made of
a porous ceramic material.
11. The honeycomb structure according to claim 1, wherein the
honeycomb substrate is integrally formed.
12. The honeycomb structure according to claim 1, wherein the
honeycomb substrate has a segment structure constituted of a
plurality of honeycomb segments.
Description
[0001] The present application is an application based on
JP-2014-033448 filed on Feb. 24, 2014 with the Japanese Patent
Office, the entire contents of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a honeycomb structure, and
more particularly, relates to a honeycomb structure which is
excellent in trapping efficiency and inhibits an increase of
pressure loss when ash is accumulated.
[0004] 2. Background Art
[0005] Heretofore, for the purpose of removing particulates
(hereinafter also referred to as PM (Particulate Matter)) included
in exhaust gas discharged from various engines and the like,
exhaust gas purifying devices including honeycomb structure filter
(honeycomb structure) have been used. There is known a honeycomb
structure including a honeycomb structured honeycomb substrate and
plugging portions disposed at open ends of inlet cells which are
predetermined cells of this honeycomb substrate on the outflow end
face side thereof and at open ends of outlet cells which are the
residual cells on the inflow end face side (e.g., see Patent
Documents 1 and 2). Specifically, the honeycomb substrate has
porous partition walls defining a plurality of cells which form
through channels for the exhaust gas.
[0006] When the exhaust gas including particulates flows into the
honeycomb structure from the inflow end portion side which is one
end portion, the exhaust gas is filtered by the partition walls to
remove the particulates and purified gas is discharged from the
outflow end portion side which is the other end portion. In such a
manner, exhaust gas is purified by the honeycomb structure.
[0007] When the exhaust gas flows into the inlet cells of the
honeycomb structure, the exhaust gas passes through the partition
walls defining the inlet cells to flow into the outlet cells, since
the open ends of the inlet cells on the outflow end face side are
plugged. Furthermore, the open ends of the outlet cells on the
inflow end face side are plugged, and hence the purified gas is
discharged from the open ends on the outflow end face side. The PM
accumulated in the honeycomb structure is burnt by raising the
temperature of the exhaust gas every appropriate interval or by
heating with an electric heater or the like. As described above,
the PM is prevented from being excessively accumulated in the
honeycomb structure.
[0008] Furthermore, some other honeycomb structures having plugging
portions disposed only at one end portion or at the other end
portion in order to prevent increase of pressure loss (e.g., see
Patent Documents 3 and 4).
[0009] [Patent Document 1] JP-A-S49-038266
[0010] [Patent Document 2] JP-A-S56-148607
[0011] [Patent Document 3] JP-A-2003-035126
[0012] [Patent Document 4] JP-A-2004-108203
SUMMARY OF THE INVENTION
[0013] However, in honeycomb structures described in Patent
Documents 1 and 2, one open end or the other open end of each cell
is plugged, and hence pressure loss noticeably increases.
Furthermore, when ash which is a noncombustible substance included
in PM is accumulated, such accumulated ash is hard to be discharged
from the honeycomb structure. Therefore, the pressure loss when ash
is accumulated also noticeably increases. In a honeycomb structure
described in Patent Document 3, there are cells in which no
plugging portion is disposed, and hence as compared with the
honeycomb structures described in Patent Documents 1 and 2, less
ash is accumulated, and the pressure loss increase is low. However
trapping efficiency of PM is deteriorated. In a honeycomb structure
described in Patent Document 4, similarly to Patent Document 3,
there are cells in which no plugging portion is disposed, and hence
the pressure loss increase is low, however as compared with the
honeycomb structures described in Patent Documents 1 and 2, the
trapping efficiency of PM is deteriorated. Further, in the
honeycomb structure described in Patent Document 4, the plugging
portions are disposed in the cells on the outflow end portion side,
and hence ash is easily deposited in the outflow end portion of the
honeycomb structure. Ash deposited in this portion is hard to be
discharged. In consequence, when the deposited ash is not
discharged, the pressure loss disadvantageously increases. On the
other hand, a great deal of labor is required to discharge ash.
[0014] In consequence, there has earnestly been desired development
of a honeycomb structure which has a favorable trapping efficiency
and inhibits increase of pressure loss when ash is accumulated.
[0015] The present invention has been developed in view of such
problems of conventional technologies, and an object thereof is to
provide a honeycomb structure which has a favorable trapping
efficiency and inhibits increase of pressure loss when ash is
accumulated.
[0016] According to the present invention, a honeycomb structure
described in the following is provided.
[0017] [1] A honeycomb structure including a honeycomb substrate
having partition walls defining a plurality of cells which form
through channels for a fluid and extend from an inflow end face as
one end face where the fluid flows in to an outflow end face as the
other end face where the fluid flows out, and plugging portions
disposed at open ends of the cells of the honeycomb substrate,
wherein the plurality of cells include at least one cell group
consisting of three cells which are a both-end plugged cell in
which the plugging portions are disposed at both open ends on the
inflow end face side and the outflow end face side, an inlet cell
which is adjacent to the both-end plugged cell and in which the
plugging portion is only disposed at the open end on the outflow
end face side, and an outlet cell which is adjacent to the both-end
plugged cell and in which the plugging portion is only disposed at
the open end on the inflow end face side, the partition walls
defining the both-end plugged cell constituting the cell group have
a first common partition wall which is a common partition wall
defining both of the inlet cell and the both-end plugged cell, and
a second common partition wall which is a common partition wall
defining both of the outlet cell and the both-end plugged cell, a
first flow-through hole is formed in an end portion of the first
common partition wall on the outflow end face side, and a second
flow-through hole is formed in an end portion of the second common
partition wall on the inflow end face side.
[0018] [2] The honeycomb structure according to the above [1],
wherein in a cross section of the honeycomb substrate which is
perpendicular to an extending direction of the cells, the inlet
cell, the both-end plugged cell and the outlet cell constituting
each of the at least one cell group are arranged so that a first
center which is the center of the inlet cell, a second center which
is the center of the both-end plugged cell and a third center which
is the center of the outlet cell are positioned on a same straight
line.
[0019] [3] The honeycomb structure according to the above [1],
wherein in the cross section of the honeycomb substrate which is
perpendicular to the extending direction of the cells, the inlet
cell, the both-end plugged cell and the outlet cell constituting
each of the at least one cell group are arranged to form an
L-shape.
[0020] [4] The honeycomb structure according to any one of the
above [1] to [3], wherein an open area of the first flow-through
hole is from 0.3 to 3.5 times as large as an average value of
sectional areas in the direction perpendicular to the cell
extending direction of the inlet cell, the both-end plugged cell
and the outlet cell constituting the cell group.
[0021] [5] The honeycomb structure according to any one of the
above [1] to [4], wherein an open area of the second flow-through
hole is from 0.3 to 3.5 times as large as the average value of the
sectional areas in the direction perpendicular to the cell
extending direction of the inlet cell, the both-end plugged cell
and the outlet cell constituting the cell group.
[0022] [6] The honeycomb structure according to any one of the
above [1] to [5], which is made of a porous ceramic material.
[0023] [7] The honeycomb structure according to any one of the
above [1] to [6], wherein the honeycomb substrate is integrally
formed.
[0024] [8] The honeycomb structure according to any one of the
above [1] to [6], wherein the honeycomb substrate has a segment
structure constituted of a plurality of honeycomb segments.
[0025] A honeycomb structure of the present invention has a
trapping efficiency of the same degree as a trapping efficiency of
a conventional honeycomb structure. That is, the honeycomb
structure of the present invention is excellent in trapping
efficiency. Furthermore, the honeycomb structure of the present
invention has cell groups including three specific cells, and first
flow-through holes and second flow-through holes are formed in
predetermined partition walls, respectively. That is, in the
honeycomb structure of the present invention, spaces where ash is
deposited are present at two positions; at an end portion on the
outflow end face side and at an end portion on the inflow end face
side (see symbols X and Y of FIG. 2). Furthermore, in the honeycomb
structure of the present invention, the ash which is accumulated in
the honeycomb structure suitably joins a flow of an exhaust gas to
be discharged outside along a route of an inlet cell, a both-end
plugged cell and an outlet cell. Therefore, the honeycomb structure
of the present invention inhibits an increase of a pressure loss
when the ash is accumulated. As a result, maintenance operations
when the ash is accumulated are performed less times, i.e., the
maintenance operation may scarcely be needed to be performed. That
is, the honeycomb structure is so-called free of maintenance in
regard to deposition of ash.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a perspective view schematically showing one
embodiment of a honeycomb structure of the present invention;
[0027] FIG. 2 is a sectional view schematically showing a cross
section parallel to an extending direction of cells in the one
embodiment of the honeycomb structure of the present invention;
[0028] FIG. 3 is an enlarged view schematically showing an enlarged
part of a cross section perpendicular to the cross section shown in
FIG. 2;
[0029] FIG. 4A is a plan view schematically showing an example of
arrangement patterns of cell group in the honeycomb structure of
the present invention;
[0030] FIG. 4B is a plan view schematically showing another example
of the arrangement patterns of a cell group in the honeycomb
structure of the present invention;
[0031] FIG. 4C is a plan view schematically showing still another
example of the arrangement patterns of a cell group in the
honeycomb structure of the present invention;
[0032] FIG. 4D is a plan view schematically showing a further
example of the arrangement patterns of a cell group in the
honeycomb structure of the present invention;
[0033] FIG. 4E is a plan view schematically showing a further
example of the arrangement patterns of a cell group in the
honeycomb structure of the present invention;
[0034] FIG. 4F is a plan view schematically showing a further
example of the arrangement patterns of a cell group in the
honeycomb structure of the present invention;
[0035] FIG. 4G is a plan view schematically showing a further
example of the arrangement patterns of a cell group in the
honeycomb structure of the present invention;
[0036] FIG. 4H is a plan view schematically showing a still further
example of the arrangement patterns of a cell group in the
honeycomb structure of the present invention;
[0037] FIG. 5A is a plan view schematically showing an example of
arrangement patterns of cell groups in the honeycomb structure of
the present invention;
[0038] FIG. 5B is a plan view schematically showing another example
of the arrangement patterns of cell groups in the honeycomb
structure of the present invention;
[0039] FIG. 6A is a plan view schematically showing an example of
arrangement patterns of cell groups in the honeycomb structure of
the present invention;
[0040] FIG. 6B is a plan view schematically showing another example
of the arrangement patterns of cell groups in the honeycomb
structure of the present invention;
[0041] FIG. 7A is a plan view schematically showing an example of
arrangement patterns of cell groups in the honeycomb structure of
the present invention;
[0042] FIG. 7B is a plan view schematically showing another example
of the arrangement patterns of cell groups in the honeycomb
structure of the present invention;
[0043] FIG. 8 is a plan view schematically showing an example of
arrangement patterns of cell groups in the honeycomb structure of
the present invention;
[0044] FIG. 9 is a plan view schematically showing an example of
arrangement patterns of cell groups in the honeycomb structure of
the present invention;
[0045] FIG. 10 is a plan view schematically showing an example of
arrangement patterns of cell groups in the honeycomb structure of
the present invention;
[0046] FIG. 11A is a plan view schematically showing an example of
arrangement patterns of cell groups in the honeycomb structure of
the present invention;
[0047] FIG. 11B is a plan view schematically showing another
example of the arrangement patterns of cell groups in the honeycomb
structure of the present invention;
[0048] FIG. 11C is a plan view schematically showing still another
example of the arrangement patterns of cell groups in the honeycomb
structure of the present invention;
[0049] FIG. 11D is a plan view schematically showing a further
example of the arrangement patterns of cell groups in the honeycomb
structure of the present invention;
[0050] FIG. 12A is an explanatory view schematically showing a
manufacturing step of one embodiment of the honeycomb structure of
the present invention;
[0051] FIG. 12B is an explanatory view schematically showing a
manufacturing step of the one embodiment of the honeycomb structure
of the present invention; and
[0052] FIG. 12C is an explanatory view schematically showing a
manufacturing step of the one embodiment of the honeycomb structure
of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0053] Hereinafter, embodiments of the present invention will be
described. It should be understood that the present invention is
not limited to the following embodiments and that the following
embodiments, to which changes, improvements and the like are
suitably added on the basis of ordinary knowledge of a person
skilled in the art without departing from the scope of the present
invention, also fall in the gist of the present invention.
[0054] [1] Honeycomb Structure:
[0055] One embodiment of a honeycomb structure of the present
invention is a honeycomb structure 100 shown in FIG. 1. The
honeycomb structure 100 includes a honeycomb substrate 10 having
partition walls 1 defining a plurality of cells 2, and plugging
portions 25 disposed at open ends of the cells 2 of the honeycomb
substrate 10. The partition walls 1 define the plurality of cells 2
which form through channels for a fluid and extend from an inflow
end face 11 as one end face where the fluid flows in to an outflow
end face 12 as the other end face where the fluid flows out. The
plurality of cells 2 include at least one cell group 5 including
three cells which are a both-end plugged cell 2b in which the
plugging portions 25 are disposed at both open ends on the inflow
end face 11 side and the outflow end face 12 side, and an inlet
cell 2a and an outlet cell 2c which are adjacent to the both-end
plugged cell 2b. The inlet cell 2a is adjacent to the both-end
plugged cell 2b, and has the plugging portion 25 disposed only on
the outflow end face 12 side of the open ends. The outlet cell 2c
is adjacent to the both-end plugged cell 2b, and has the plugging
portion 25 disposed only on the inflow end face 11 side of the open
ends. That is, one both-end plugged cell 2b is adjacent to an inlet
cell 2a and an outlet cell 2c. The partition walls 1 defining the
both-end plugged cell 2b constituting the cell group 5 have a first
common partition wall 1a and a second common partition wall 1b. The
first common partition wall 1a is the common partition wall 1
defining both of the inlet cell 2a and the both-end plugged cell
2b. The second common partition wall 1b is the common partition
wall 1 defining both of the outlet cell 2c and the both-end plugged
cell 2b. A first flow-through hole 7 is formed in an end portion of
the first common partition wall 1a on the outflow end face 12 side,
and a second flow-through hole 8 is formed in an end portion of the
second common partition wall 1b on the inflow end face 11 side.
[0056] In the honeycomb structure 100 shown in FIG. 1 and FIG. 2,
through-cells which are non-plugged cells (i.e., cells whose both
open ends are opened) are not present, and hence deterioration of a
trapping efficiency due to the presence of the through-cells can be
prevented. That is, more suitable trapping efficiency can be
obtained than a honeycomb structure in which one open end or the
other open end of each cell is plugged; such a honeycomb structure
as described in Patent Documents 3 and 4.
[0057] Furthermore, the honeycomb structure 100 inhibits an
increase of a pressure loss when ash is accumulated. As a result,
for the honeycomb structure 100, maintenance operations when the
ash is accumulated are performed less times, and the maintenance
operations may scarcely be needed to be performed. That is, the
honeycomb structure 100 is so-called free of maintenance in regard
to deposition of ash. Specifically, in the honeycomb structure 100,
the ash is easily deposited at two positions; at an end portion on
the outflow end face 12 side (shown by symbol "X" in FIG. 2) and at
an end portion on the inflow end face 11 side (shown by symbol "Y"
in FIG. 2), which are in through channels formed along a route of
inlet cell 2a, both-end plugged cell 2b and outlet cell 2c. On the
other hand, in a conventional honeycomb structure (such a honeycomb
structure as described in Patent Document 1), ash is easily
deposited only in an end portion on the outflow end face side. That
is, the honeycomb structure 100 has a large space where the ash can
be deposited. Consequently, the honeycomb structure 100 has a
smaller degree of increase of pressure loss as compared with the
conventional honeycomb structure, even when the amount of ash as
much as can be deposited under predetermined conditions in the
conventional honeycomb structure is accumulated in the present
honeycomb structure. Furthermore, the ash accumulated in the
honeycomb structure 100 suitably joins a flow of an exhaust gas to
be discharged outside. For example, the ash present in the inlet
cell 2a flows into the both-end plugged cell 2b from the first
flow-through hole 7 formed in the partition wall 1 between the
inlet cell 2a and the both-end plugged cell 2b. Next, the ash flows
into the outlet cell 2c from the second flow-through hole 8 formed
in the partition wall 1 between the both-end plugged cell 2b and
the outlet cell 2c. Afterward, the ash is discharged from the
honeycomb structure 100. In this way, the ash can be deposited in
the large space and the accumulated ash joins the flow of the
exhaust gas to be suitably discharged. Hence the through channels
of the exhaust gas would not completely be closed, and the degree
of increase of pressure loss due to the deposition of ash is
reduced (increase of pressure loss is inhibited).
[0058] FIG. 1 is a perspective view schematically showing one
embodiment of the honeycomb structure of the present invention.
FIG. 2 is a sectional view schematically showing a cross section
parallel to an extending direction of cells in the one embodiment
of the honeycomb structure of the present invention.
[0059] The inlet cells, the both-end plugged cells and the outlet
cells are preferably arranged as follows. That is, in a cross
section of the honeycomb substrate which is perpendicular to the
cell extending direction, a center of the inlet cell is "a first
center", a center of the both-end plugged cell is "a second
center", and a center of the outlet cell is "a third center". Then,
the inlet cell, the both-end plugged cell and the outlet cell are
preferably arranged so that the first center, the second center and
the third center are positioned on a same straight line. In the
honeycomb structure 100, the inlet cell 2a, the both-end plugged
cell 2b and the outlet cell 2c are arranged so that the center of
the inlet cell 2a (first center), the center of the both-end
plugged cell 2b (second center) and the center of the outlet cell
2c (third center) are positioned on the same straight line.
[0060] Furthermore, in another preferable configuration, the inlet
cell, the both-end plugged cell and the outlet cell are arranged to
form an L-shape as shown in FIG. 4A to FIG. 4H, when seen from the
cell extending direction. That is, in this preferable
configuration, the cell group consisting of three cells of one
inlet cell, one both-end plugged cell and one outlet cell is formed
into the L-shape.
[0061] That "the inlet cell, the both-end plugged cell and the
outlet cell form the L-shape" indicates that the respective cells
are arranged in a state where the first common partition wall and
the second common partition wall are not in such a positional
relation as to face each other, but are positioned to form two
adjacent partition walls among the partition walls constituting the
both-end plugged cell.
[0062] FIG. 4A is a plan view schematically showing an example of
arrangement patterns of a cell group in the honeycomb structure of
the present invention. FIG. 4B is a plan view schematically showing
another example of the arrangement patterns of a cell group in the
honeycomb structure of the present invention. FIG. 4C is a plan
view schematically showing still another example of the arrangement
patterns of a cell group in the honeycomb structure of the present
invention. FIG. 4D is a plan view schematically showing a further
example of the arrangement patterns of a cell group in the
honeycomb structure of the present invention. FIG. 4E is a plan
view schematically showing a further example of the arrangement
patterns of a cell group in the honeycomb structure of the present
invention. FIG. 4F is a plan view schematically showing a further
example of the arrangement patterns of a cell group in the
honeycomb structure of the present invention. FIG. 4G is a plan
view schematically showing a further example of the arrangement
patterns of a cell group in the honeycomb structure of the present
invention. FIG. 4H is a plan view schematically showing a still
further example of the arrangement patterns of a cell group in the
honeycomb structure of the present invention.
[0063] The honeycomb structure of the present invention includes at
least one cell group. That is, in the honeycomb structure of the
present invention, the cell group as one set of three cells
consisting of the inlet cell, the both-end plugged cell and the
outlet cell may partially be present. Also when the above cell
group is partially present, the advantageous effect of the present
invention can be expected. When the cell group is partially
present, for example, in a configuration, the cell groups are
disposed in the central portion of the honeycomb structure (central
portion in the cross section perpendicular to the cell extending
direction), and the cells described below (through-cells or
conventional type cells) are disposed in the outer circumferential
portion (portion other than the central portion). That is, the
cells disposed in the outer circumferential portion of the
honeycomb structure may be cells which have no plugging portions at
both ends (through-cells) or cells having plugging portions in a
checkered pattern in both the end faces, only in the inflow end
face, or only in the outflow end face (conventional type cells).
The latter cells (conventional type cells) are the cells in which
the plugging portions are disposed as in the conventional type
honeycomb structure. Furthermore, the abovementioned arrangements
in the central portion and the outer circumferential portion of the
honeycomb structure may be reversed. In the honeycomb structure of
the present invention, the "ratio of the cell groups" may suitably
be determined in consideration of the required trapping efficiency
or pressure loss. The ratio is preferably from 10 to 100% and
further preferably from 30 to 100%. The "ratio of the cell groups"
is the ratio of "number of the cell groups" to "value of 1/3 of the
number of all the cells (number of all the cells regardless of the
presence/absence of the plugging portions". It is to be noted that
the cells are counted excluding cells deformed by a circumferential
wall or cells in which one or more sides (walls) forming each of
the cells constitute the circumferential wall (hereinafter, these
cells may be referred to as "incomplete cells").
[0064] When a plurality of cell groups are included, there is not
any special restriction on an arrangement pattern of these cell
groups, but the plurality of cell groups can be arranged as shown
in, for example, FIG. 5A to FIG. 11D. It is to be noted that in
FIG. 5A to FIG. 11D, "1" indicates the inlet cells. "2" indicates
the both-end plugged cells. "3" indicates the outlet cells.
Furthermore, FIG. 5A to FIG. 11D schematically show the arrangement
patterns of the cell groups, and for the convenience in explaining
the arrangement pattern of the cell groups, a part of the honeycomb
structure is extracted and shown. Additionally, in FIG. 5A to FIG.
11D, depiction of the plugging portions is omitted.
[0065] Each of FIG. 5A to FIG. 11D is a plan view schematically
showing the arrangement patterns of cell groups in the honeycomb
structure of the present invention.
[0066] FIG. 5A and FIG. 5B show examples where the cell groups each
including the inlet cell, the both-end plugged cell and the outlet
cell arranged on the same straight line are arranged in a same
order. FIG. 6A and FIG. 6B show examples where each of the
arrangements shown in FIG. 5A and FIG. 5B is shifted as much as one
cell (to the left side or the right side in the drawing or to the
upside or the downside in the drawing) every row. FIG. 7A, FIG. 7B
and FIG. 8 show examples where the number of the cells to be
shifted (to the left side or the right side in the drawing) is
changed in respective rows on the basis of the arrangement shown in
FIG. 5A. FIG. 9 and FIG. 10 show examples where the cell groups
shown in FIG. 4A, FIG. 4B and FIG. 4E are alternately arranged.
[0067] Furthermore, in the honeycomb structure of the present
invention, as shown in FIG. 11A to FIG. 11D, the cell groups each
including the inlet cell, the both-end plugged cell and the outlet
cell arranged on a same straight line may be arranged while
shifting as much as 1/2 cell to the horizontal direction of the
drawing (to the left side or the right side in the drawing) every
row.
[0068] In FIG. 5A and FIG. 5B among FIG. 5A to FIG. 8 and FIG. 11A
to FIG. 11D, the inlet cell, the both-end plugged cell and the
outlet cell are arranged on a straight line, respectively, and
hence the plugging portions are easily formed which facilitates
preparation.
[0069] In FIG. 6A, FIG. 6B and FIG. 8, all of four partition walls
of each inlet cell are adjacent to the both-end plugged cell or the
outlet cell, and hence the exhaust gas also flows through these
partition walls. Therefore, in the arrangements (arrangement
patterns) shown in FIG. 6A, FIG. 6B and FIG. 8, the pressure loss
lowers as much as about 5% as compared with the other arrangement
patterns.
[0070] In addition, a plurality of types of arrangement patterns
shown in FIG. 5A to FIG. 11D may be combined and arranged.
[0071] An open area of the first flow-through hole is preferably
from 0.3 to 3.5 times and further preferably from 0.5 to three
times as large as an average value of sectional areas of the inlet
cell, the both-end plugged cell and the outlet cell constituting
the cell group. When the above "open area of the first flow-through
hole" is smaller than the above lower limit value, there is the
fear that the pressure loss increases. When the above "open area of
the first flow-through hole" is in excess of the above upper limit
value, there is the fear that isostatic strength deteriorates. The
"sectional areas of the inlet cell, the both-end plugged cell and
the outlet cell" are the areas of the respective cells in the cross
section perpendicular to the cell extending direction. In the
present description, the "average value of the sectional areas of
the inlet cell, the both-end plugged cell and the outlet cell
constituting the cell group" is the following value. That is, the
above average value is a value obtained by multiplying a value of
the sum of "sectional area of the inlet cell", "sectional area of
the both-end plugged cell" and "sectional area of the outlet cell"
constituting one cell group by 1/3. It is to be noted that when the
open area is calculated, a plurality of cell groups are suitably
selected.
[0072] The "end portion on the outflow end face side" in which the
first flow-through hole is formed is specifically a portion from
the outflow end face of the honeycomb structure to a position of
1/3 of the length of the honeycomb structure in the cell extending
direction (first flow-through hole forming region). The first
flow-through hole is preferably formed in the above first
flow-through hole forming region, but in the above first
flow-through hole forming region, the hole is more preferably
formed in a portion from the outflow end face of the honeycomb
structure to a position of 1/5 of the length of the honeycomb
structure in the cell extending direction.
[0073] An open area of the second flow-through hole is preferably
from 0.3 to 3.5 times and further preferably from 0.5 to three
times as large as the average value of the sectional areas of the
inlet cell, the both-end plugged cell and the outlet cell
constituting the cell group. When the above "open area of the
second flow-through hole" is smaller than the above lower limit
value, there is the fear that the pressure loss increases. When the
above "open area of the second flow-through hole" is in excess of
the above upper limit value, there is the fear that the isostatic
strength deteriorates.
[0074] The "end portion on the inflow end face side" in which the
second flow-through hole is formed is specifically a portion from
the inflow end face of the honeycomb structure to the position of
1/3 of the length of the honeycomb structure in the cell extending
direction (second flow-through hole forming region). The second
flow-through hole is preferably formed in the above second
flow-through hole forming region, but in the above second
flow-through hole forming region, the hole is more preferably
formed in a portion from the inflow end face of the honeycomb
structure to the position of 1/5 of the length of the honeycomb
structure in the cell extending direction.
[0075] There is not any special restriction on a shape of the
opening of each of the first flow-through hole and the second
flow-through hole, and the shapes of the openings of the respective
flow-through holes may be the same or different. Examples of the
shape of the opening of each flow-through hole include a circular
shape, a semicircular shape, an elliptic shape, a semi-elliptic
shape (shape obtained by cutting an ellipse along a short
diameter), a triangular shape and a quadrangular shape. FIG. 3
shows the enlarged first flow-through holes 7. The shape of the
opening of the first flow-through holes 7 is semi-elliptic. Such a
semi-elliptic opening is easily formed. FIG. 3 is an enlarged view
schematically showing an enlarged part of a cross section
perpendicular to the cross section (cross section A-A) shown in
FIG. 2.
[0076] The honeycomb structure of the present invention is
preferably made of a porous ceramic material. That is, the
honeycomb substrate and the plugging portions constituting the
honeycomb structure are preferably made of the porous ceramic
material. When the honeycomb structure is made of the porous
ceramic material, catalyst is easily loaded onto the honeycomb
structure. The honeycomb structure of the present invention may be
made of a sintered metal obtained by forming and then sintering
metal powder, or a metal foil.
[0077] Specifically, when the honeycomb structure is made of a
ceramic material, the ceramic material is further preferably at
least one selected from the group consisting of cordierite, silicon
carbide, a silicon-silicon carbide based composite material,
mullite, alumina, aluminum titanate, silicon nitride, and a silicon
carbide-cordierite based composite material, from the viewpoint
that the materials are excellent in strength and heat resistance.
Among these materials, cordierite and silicon carbide are
preferable.
[0078] The honeycomb substrate of the honeycomb structure of the
present invention preferably has a segment structure constituted of
a plurality of honeycomb segments. Such segment structure enables
manufacturing a honeycomb structure which is hard to be integrally
manufactured (e.g., large honeycomb structure).
[0079] The honeycomb substrate having the segment structure can
specifically be a bonded assembly having a plurality of honeycomb
segments and a bonding layer to bond the plurality of honeycomb
segments to one another.
[0080] In addition, the honeycomb substrate of the honeycomb
structure of the present invention is also preferably integrally
formed. The honeycomb substrate integrally formed in this manner,
simplifies the manufacturing steps. When the honeycomb substrate is
"integrally formed", it is meant that the honeycomb substrate is
constituted of one member. That is, the whole honeycomb substrate
is formed at a time by a method of extrusion or the like.
[0081] The respective members of the honeycomb structure of the
present invention will further be described in the following.
[0082] [1-1] Honeycomb Substrate:
[0083] A thickness of the partition walls of the honeycomb
substrate 10 is preferably from 40 to 600 .mu.m, further preferably
from 80 to 500 .mu.m and especially preferably from 100 to 400
.mu.m. When the above thickness of the partition walls is smaller
than 40 .mu.m, there is the fear that the strength of the partition
walls may be insufficient. On the other hand, when the thickness is
in excess of 600 .mu.m, there is the fear that the pressure loss
increases.
[0084] A porosity of the partition walls of the honeycomb substrate
10 is preferably from 25 to 80%, further preferably from 30 to 75%
and especially preferably from 30 to 70%. When the above porosity
is smaller than 25%, there is the fear that the pressure loss
increases. On the other hand, when the porosity is in excess of
80%, there is the fear that the strength of the partition walls may
be lower. Here, in the present description, "porosity" is a value
measured by a mercury porosimeter.
[0085] An average pore diameter of the partition walls of the
honeycomb substrate 10 is preferably from 5 to 100 .mu.m, further
preferably from 7 to 80 .mu.m and especially preferably from 7 to
60 When the above average pore diameter is smaller than 5 .mu.m,
there is the fear that the pressure loss increases. On the other
hand, when the average pore diameter is in excess of 100 .mu.m,
there is the fear that the exhaust gas purification performance
deteriorates. Here, in the present description, "the average pore
diameter" is a value measured by the mercury porosimeter.
[0086] A cell density of the honeycomb substrate 10 is preferably
from 12 to 200 cells/cm.sup.2, further preferably from 15 to 150
cells/cm.sup.2 and especially preferably from 20 to 120
cells/cm.sup.2. When the above cell density is smaller than 12
cells/cm.sup.2, there is the fear that the isostatic strength
lowers. On the other hand, when the cell density is in excess of
200 cells/cm.sup.2, there is the fear that the pressure loss
increases.
[0087] A shape of each of the cells 2 in the cross section
perpendicular to the extending direction of the cells 2 of the
honeycomb substrate 10 can be, for example, quadrangular or
hexagonal.
[0088] A length of the honeycomb substrate 10 (honeycomb structure
100) in the cell extending direction can be from 50 to 1000 mm or
more (in excess of 1000 mm) In addition, when each end face of the
honeycomb structure 100 is circular, a diameter of the end faces
can be from 25 to 600 mm or more (in excess of 600 mm).
[0089] A shape of the honeycomb substrate 10 can be each of various
shapes such as a columnar shape, an elliptic columnar shape, a
quadrangular columnar shape and a hexagonal columnar shape. Among
these shapes, the columnar shape and the quadrangular columnar
shape are preferable.
[0090] [1-2] Plugging Portion:
[0091] A depth of each plugging portion (length in the cell
extending direction) is preferably from 0.3 to 10 mm, further
preferably from 0.5 to 8 min and especially preferably from 1 to 7
mm. When the depth of the plugging portion is smaller than the
above lower limit value, there is the fear that the plugging
portions drop out due to vibrations or the like. When the depth of
the plugging portion is in excess of the above upper limit value
and the honeycomb structure is used as a filter, there is the fear
that portions of the honeycomb structure functioning as the filter
decrease.
[0092] A material of the plugging portions can be the same as the
material of the partition walls. In particular, the material of the
plugging portions is preferably a porous ceramic material.
[0093] The honeycomb structure 100 shown in FIG. 1 has a
circumferential wall 26, but does not necessarily have the
circumferential wall 26. The circumferential wall 26 can be formed
by applying an outer circumference coating ceramic material to an
outer circumference of the honeycomb structure. Furthermore, the
circumferential wall 26 may be formed simultaneously with the
partition walls in a process of preparing the honeycomb substrate
10, when the honeycomb substrate is integrally formed by extrusion
or the like.
[0094] [2] Manufacturing Method of Honeycomb Structure:
[0095] The honeycomb structure of the present invention can be
manufactured, for example, as follows. The honeycomb structure in
which the honeycomb substrate is integrally formed will be
described.
[0096] First, a kneaded material to prepare the honeycomb substrate
is prepared and this kneaded material is formed to prepare a
honeycomb formed body (forming step).
[0097] Next, the obtained honeycomb formed body (or a honeycomb
dried body after drying is performed as required) is fired to
prepare a honeycomb fired body (honeycomb fired body preparing
step).
[0098] Next, the prepared honeycomb fired body 50 is disposed so
that the end portion thereof on the outflow end face 112 side is
positioned on the upside as shown in FIG. 12A. Afterward, a resin
member is pushed into each partition wall 3 in which a first
flow-through hole is to be formed. Afterward, the honeycomb fired
body 50 is inverted and disposed so that the end portion thereof on
the inflow end face 111 side is positioned on the upside.
Afterward, as shown in FIG. 12B, a resin member 20 is pushed into
each partition wall 3 in which a second flow-through hole is to be
formed, so that a portion of the partition wall 3 into which the
resin member 20 is pushed is destroyed. It is to be noted that the
partition walls 3 are very thin, and hence the resin members 20 can
be pushed thereinto by manual force. When the resin members are
used in this manner, the flow-through holes (first flow-through
holes and second flow-through holes) each having a desirable size
can surely be formed. That is, each resin member performs a
function of a spacer, and the resin members burn away when fired,
so that the flow-through holes (first flow-through holes and second
flow-through holes) are formed.
[0099] There is not any special restriction on physical properties
of the resin member, as long as the resin member performs the
function as spacer and burns away when fired. As to a hardness of
the resin member, the resin member may be hard to such an extent
that a part of partition wall may be destroyed. It is to be noted
that when the partition wall is partially destroyed, the resin
member is not directly pushed, but the resin member may be pushed
by using a needle, laser beams or the like. In this case, the
hardness of the resin member can freely be set, and the resin
member does not have to be hard to such an extent that the
partition wall can be destroyed.
[0100] Specifically, as the resin member, a member made of
polyethylene, a member made of nylon or the like may be used.
[0101] Next, as shown in FIG. 12C, in the honeycomb fired body 50
into which the resin members 20 has been pushed, a plugging
material 23 is charged into spaces formed by pushing the resin
members 20 thereinto (plugging material charging step).
[0102] It is to be noted that in the manufacturing method of the
honeycomb structure of the present invention, a method without
using the resin members may be employed. That is, a viscosity of
the plugging material may be increased, so that each portion that
becomes the flow-through hole is not closed with the plugging
material, when the plugging material is charged thereinto.
[0103] Next, the honeycomb fired body into which the plugging
material is charged is fired again to form the plugging portions
(plugging portion forming step). The resin members burn away when
fired in this manner, and portions where the resin members have
been disposed become the first flow-through holes and the second
flow-through holes. In such a manner, the honeycomb structure can
be prepared.
[0104] In addition, the honeycomb structure may be prepared by
grinding partition walls of the honeycomb dried body dried after
forming or by burning using laser beams to form the flow-through
holes each having the desirable size, and then charging the
plugging material so that the portions which become the
flow-through holes are not closed, followed by the firing.
EXAMPLES
[0105] Hereinafter, the present invention will specifically be
described on the basis of examples, but the present invention is
not limited to these examples.
Example 1
[0106] A pore former, an organic binder and water were added to a
cordierite forming raw material to obtain a forming raw material.
The forming raw material was mixed and kneaded to prepare a
columnar kneaded material. As an organic binder, methylcellulose
was used, and 5 parts by mass of methylcellulose was added to 100
parts by mass of the cordierite forming raw material. The water was
added as a dispersing medium as much as 10 mass % to the whole
forming raw material. The cordierite forming raw material is a raw
material which becomes cordierite when fired. Specifically, the
cordierite forming raw material is a ceramic raw material obtained
by mixing "predetermined raw materials" to obtain a chemical
composition in which silica (SiO.sub.2) is in a range of 42 to 56
mass %, alumina (Al.sub.2O.sub.3) is in a range of 30 to 45 mass %,
and magnesia (MgO) is in a range of 12 to 16 mass %. "The
predetermined raw materials" are raw materials selected from the
group consisting of talc, kaolin, calcinated kaolin, alumina,
aluminum hydroxide and silica.
[0107] Next, the kneaded material was extruded by using a
predetermined die to obtain a honeycomb formed body having
partition walls defining a plurality of cells and a circumferential
wall formed simultaneously with the partition walls by the
extrusion. In the honeycomb formed body, the cell shape (shape of
each cell in the cross section perpendicular to the extending
direction of the cells) was square and the whole shape was
columnar.
[0108] Next, the obtained honeycomb formed body was dried by
dielectric drying and hot air drying, and then fired at the highest
temperature of 1420.degree. C. for 100 hours to prepare a honeycomb
fired body.
[0109] The obtained honeycomb fired body had a partition wall
thickness of 100 .mu.m and a cell density of 45 cells/cm.sup.2.
Furthermore, the porosity of the partition walls of the honeycomb
fired body was 50%. In addition, the average pore diameter of the
honeycomb fired body was 18 .mu.m. The honeycomb fired body had a
columnar shape having a bottom surface diameter of 320 mm and a
length of 300 mm in the cell extending direction. Additionally, the
porosity and the average pore diameter were values measured by a
mercury porosimeter.
[0110] Next, resin members made of polyethylene were pushed from
the inflow end face side along the cell extending direction into
the honeycomb structure so as to destroy predetermined end portions
of partition walls, thereby removing portions (inflow end portions)
from the partition wall. Afterward, portions (outflow end portions)
of the partition wall on the outflow end face side were similarly
removed.
[0111] Next, plugging material was charged into parts of region
formed by removing the portions from the partition wall so that
holes where the adjacent cells communicate with each other are
left. That is, the plugging material was charged into each cell at
a depth smaller than the depth of the removed portion. Afterward,
the firing was performed again. In this way, the honeycomb
structure made of a porous ceramic material was prepared.
[0112] The prepared honeycomb structure was such a honeycomb
structure as shown in FIG. 1. The arrangement pattern of cell
groups was such a pattern as shown in FIG. 5A. Specifically, inlet
cells, both-end plugged cells and outlet cells were arranged so
that centers of the three cells constituting each cell groups were
positioned on a same straight line. Furthermore, a plurality of
cell groups was present and the cell groups were vertically and
horizontally aligned and arranged.
[0113] The open area of each first flow-through hole was 0.3 times
as large as the average value of the sectional areas of the inlet
cells, the both-end plugged cells and the outlet cells constituting
the cell groups. Furthermore, the open area of each second
flow-through hole was 0.3 times as large as the average value of
the sectional areas of the inlet cells, the both-end plugged cells
and the outlet cells constituting the cell groups. As to the
calculation of the above open areas, 20 cell groups were randomly
selected.
[0114] In addition, the ratio of the cell groups was 100%. It is to
be noted that the ratio of the cell groups is a ratio of "number of
the cell groups" to "value of 1/3 of the number of all the cells".
Furthermore, when the "number of the cell groups" is counted, a
same cell is not counted twice. That is, it can be considered that
the "number of the cell groups" is the number of the both-end
plugged cells. It is to be noted that when the cells are counted,
cells deformed by the circumferential wall or cells in which one or
more sides forming each cell constitute a part of the
circumferential wall (incomplete cells) are excluded. Furthermore,
the shape of the opening of each of the first flow-through holes
and second flow-through holes was quadrangular. The width of the
opening of the flow-through hole was the same as the width of the
inner dimension of each cell. Specifically, the partition wall
destroyed by pushing the resin member made of polyethylene into the
honeycomb structure as described above had a state where a part of
the partition wall did not remain in the form of a so-called burr.
It is to be noted that it can be considered, for example, that FIG.
3 shows a state where a part of each partition wall remains in the
form of the so-called burr.
[0115] Next, as to the obtained honeycomb structure, "trapping
efficiency", "initial pressure loss" and "pressure loss after ash
deposition" were measured and evaluated by the following methods.
The results are shown in Table 1.
[0116] [Trapping Efficiency]
[0117] An exhaust gas (200.degree. C.) including soot generated by
a "soot generator which burns diesel fuel (light oil), thereby
generating soot" was allowed to pass the honeycomb structure. The
soot included in the exhaust gas before the exhaust gas passed the
honeycomb structure was trapped with filter paper, and the weight
(W1) of the soot was measured. The soot included in the exhaust gas
which passed the honeycomb structure was trapped with filter paper,
and the weight (W2) of the soot was measured. The obtained (W1) and
(W2) were substituted into Equation (1) described below, to obtain
the trapping efficiency (%).
((W1-W2)/W1).times.100 Equation (1)
[0118] Afterward, the trapping efficiency was evaluated on the
basis of the following standards. When the trapping efficiency
improves as much as 15% or more as compared with trapping
efficiencies of corresponding comparative examples each having
plugging portions only at the inflow end face or only at the
outflow end face (shown by "TE1 to TE6" in Table 2), the evaluation
is "A". When the improvement is 10% or more and smaller than 15%,
the evaluation is "B". When the improvement is 5% or more and
smaller than 10%, the evaluation is "C". When the improvement is
smaller than 5%, the evaluation is "D". It is to be noted that the
improvement of the trapping efficiency of 5% or more can usually be
considered to be preferable (practical). The results are shown in
Table 1.
[0119] [Initial Pressure Loss]
[0120] Air was allowed to flow through the honeycomb structure at
an atmospheric pressure (1 atm), room temperature (20.degree. C.)
and a rate of 15 m.sup.3/minute to measure the "initial pressure
loss". Afterward, the initial pressure loss was evaluated on the
basis of the following standards.
[0121] When the initial pressure loss decreases as much as 30% or
more as compared with pressure losses of corresponding comparative
examples each having plugging portions in end portions on both of
the inlet side and the outlet side (shown by "PD1 to PD3" in Table
2), the evaluation is "A". When the decrease is smaller than 30%
and 15% or more, the evaluation is "B". When the decrease is
smaller than 15% and 5% or more, the evaluation is "C". When the
decrease is smaller than 5%, the evaluation is "D". It is to be
noted that the decrease of the initial pressure loss of 5% or more
can usually be considered to be preferable (i.e., practical). The
results are shown in Table 1.
[0122] [Pressure Loss after Ash Deposition]
[0123] Ash discharged from engine was collected in advance, for
example, at the above evaluation tests, which is prepared for use.
First, in a state where the inflow end face of the honeycomb
structure was disposed to face upside, 100 g of the ash was
supplied into the honeycomb structure from the inflow end face.
Next, this honeycomb structure was attached to an exhaust tube of a
six-cylinder 6,000 cc diesel engine, and operated on conditions of
2,000 rpm and 100 N-m. After ten minutes from the start of the
engine, "initial pressure loss after ash deposition" was measured.
Afterward, the initial pressure loss after ash deposition was
evaluated on the basis of the following standards. When the
"initial pressure loss after ash deposition" increases as much as
5% or less from the "initial pressure loss", the evaluation is "A".
When the increase is in excess of 5% and 10% or less, the
evaluation is "B". When the increase is in excess of 10% and 20% or
less, the evaluation is "C". When the increase is in excess of 20%,
the evaluation is "D". An increase of 20% or less can be considered
to be practical. The results are shown in Table 1.
TABLE-US-00001 TABLE 1 Arrangement Partition wall Open area of
first Open area of Initial pattern of cell thickness Cell density
flow-through second flow- Trapping pressure Pressure loss after
Structure groups (.mu.m) (cells/cm.sup.2) hole (times) through hole
(times) efficiency loss ash deposition Example 1 Integral FIG. 5A
140 65 0.3 0.3 A C B Example 2 Integral 140 65 0.5 0.5 A B A
Example 3 Integral 140 65 0.5 1.0 A A A Example 4 Integral 140 65
1.0 0.5 A A A Example 5 Integral 140 65 1.0 1.0 A A A Example 6
Integral 140 65 2.0 2.0 A A A Example 7 Integral 140 65 3.0 3.0 A A
A Example 8 Integral 140 65 3.5 3.5 B A A Example 9 Integral FIG.
6A 250 35 0.5 0.5 A B A Example 10 Integral 250 35 3.0 3.0 A A A
Example 11 Integral FIG. 8 140 65 0.3 0.3 A C B Example 12 Integral
140 65 1.0 1.0 A A A Example 13 Integral FIG. 9 250 35 0.3 0.3 A C
B Example 14 Integral 250 35 1.0 1.0 A A A Example 15 Integral FIG.
11C 140 65 0.3 0.3 A C B Example 16 Integral 140 65 0.5 0.5 A B A
Example 17 Integral 140 65 2.0 3.0 A A A Example 18 Integral 140 65
3.5 3.5 B A A Example 19 Segment FIG. 7A 250 35 0.3 0.3 A C B
Example 20 Segment 250 35 1.0 1.0 A A A Example 21 Segment FIG. 10
250 35 1.0 2.0 A A A Example 22 Segment 250 35 3.5 3.5 B A A
[0124] In the honeycomb structure of the present example, the
evaluation of "trapping efficiency" was "A", the evaluation of
"initial pressure loss" was "C", and the evaluation of "pressure
loss after ash deposition" was "B".
[0125] In Tables 1 and 2, "integral" in the column of "structure"
indicates that the honeycomb structure is constituted of one
extruded structure as in the present example. "Segment" in the
column of "structure" indicates that the honeycomb structure is
constituted by bonding a plurality of segment honeycomb structures
with a bonding material.
Examples 2 to 22 and Comparative Examples 0.1 to 9
[0126] First, in Examples 2 to 18, the procedures of Example 1 were
repeated to prepare honeycomb structures satisfying conditions
shown in Tables 1 and 2.
[0127] In each of Examples 19 to 22, segment honeycomb structures
each having a cross section of vertical size 40 mm.times.horizontal
size 40 mm and length 300 mm were prepared. The prepared segment
honeycomb structures were bonded with a bonding material to prepare
a bonded honeycomb assembly, and the outer circumference of this
bonded honeycomb assembly was ground. Afterward, an outer
circumference coating having a thickness of 1 mm was further
applied to prepare a honeycomb structure having a diameter of 320
mm and a length of 300 mm. Additionally, the thickness of the
bonding material was 1 mm.
[0128] Comparative Examples 1 to 9 were honeycomb structures which
have no flow-through holes to allow adjacent cells to communicate
with each other or no both-end plugged cells having both end
portions plugged. Furthermore, such honeycomb structures are
conventional type honeycomb structures having plugging portions in
a checkered pattern at both end faces, only in an inflow end face,
or only in an outflow end face. Comparative Examples 1 to 3 are
comparative examples corresponding to Examples 1 to 8, 11, 12 and
15 to 18. Comparative Examples 4 to 6 are comparative examples
corresponding to Examples 9, 10, 13 and 14. Comparative Examples 7
to 9 are comparative examples corresponding to Examples 19 to
22.
[0129] Additionally, as to "trapping efficiency", evaluation was
performed on the basis of a comparative example which has a better
trapping efficiency (i.e., having a larger trapping efficiency) of
the two comparative examples corresponding to the example and each
having plugging portions "only at the inflow end face" or "only at
the outflow end face". For example, the trapping efficiency of the
honeycomb structure of Example 1 was evaluated on the basis of the
honeycomb structure of Comparative Example 2 or 3 having a larger
trapping efficiency TE1 or TE2.
[0130] As to each of the above honeycomb structures, the procedures
of Example 1 were repeated to measure and evaluate "trapping
efficiency", "initial pressure loss" and "pressure loss after ash
deposition". The results are shown in Tables 1 and 2. In Table 2,
"both end faces" in the column of "arrangement of plugging
portions" indicate that plugging portions are formed in end
portions of predetermined cells on the inflow end face side and end
portions of the residual cells on the outflow end face side wherein
the plugging portions are arranged alternately (in a zigzag manner)
so as to form so-called checkered patterns at both of the end
faces. In Table 2, "inflow end face only" in the column of
"arrangement of plugging portions" indicates that the plugging
portions are disposed only in the end portions on the inflow end
face side, and the plugging portions are not disposed in the end
portions on the outflow end face side wherein the above plugging
portions are arranged to form the so-called checkered pattern in
the inflow end face. In Table 2, "only the outflow end face" in the
column of "the arrangement of the plugging portions" indicates that
the plugging portions are disposed only in the end portions on the
outflow end face side, the plugging portions are not disposed in
the end portions on the inflow end face side wherein the above
plugging portions are arranged to form the so-called checkered
pattern at the outflow end face.
TABLE-US-00002 TABLE 2 Partition wall Initial thickness Cell
density Arrangement of Trapping pressure Structure (.mu.m)
(cells/cm.sup.2) plugging portions efficiency loss Comparative
Integral 140 65 Both end face -- PD1 Example 1 Comparative Integral
140 65 Inflow end face only TE1 -- Example 2 Comparative Integral
140 65 Outflow end face TE2 -- Example 3 only Comparative Integral
250 35 Both end face -- PD2 Example 4 Comparative Integral 250 35
Inflow end face only TE3 -- Example 5 Comparative Integral 250 35
Outflow end face TE4 -- Example 6 only Comparative Segment 250 35
Both end face -- PD3 Example 7 Comparative Segment 250 35 Inflow
end face only TE5 -- Example 8 Comparative Segment 250 35 Outflow
end face TE6 -- Example 9 only
[0131] It has been confirmed that the honeycomb structures of
Examples 1 to 22 have improved initial pressure loss and trapping
efficiency as compared with the honeycomb structures of Comparative
Examples 1 to 9. Furthermore, it can be confirmed that the pressure
loss after ash deposition increases less and maintenance operations
to be performed when the ash is accumulated is not required.
Additionally, after the test, each honeycomb structure was
disassembled to observe the insides of the cells. A small amount of
ash has been deposited, and it can be considered that most of the
ash has been discharged together with the exhaust gas from the
engine.
INDUSTRIAL APPLICABILITY
[0132] A honeycomb structure of the present invention can be used
as a filter to purify exhaust gas discharged from a car or the
like.
DESCRIPTION OF SYMBOLS
[0133] 1 and 3: partition wall, 1a: first common partition wall,
1b: second common partition wall, 2: cell, 2a: inlet cell, 2b:
both-end plugged cell, 2c: outlet cell, 5: cell group, 7: first
flow-through hole, 8: second flow-through hole, 10: honeycomb
substrate, 11: inflow end face, 12 and 112: outflow end face, 20:
resin member, 23: plugging material, 25: plugging portion, 26:
circumferential wall, 50: honeycomb fired body, and 100: honeycomb
structure.
* * * * *