U.S. patent application number 12/854399 was filed with the patent office on 2011-03-31 for honeycomb structure and method for manufacturing the same.
This patent application is currently assigned to NGK Insulators, Ltd.. Invention is credited to Shuhei Fujita, Koji KIMURA, Takuya Nunome.
Application Number | 20110076443 12/854399 |
Document ID | / |
Family ID | 43780689 |
Filed Date | 2011-03-31 |
United States Patent
Application |
20110076443 |
Kind Code |
A1 |
KIMURA; Koji ; et
al. |
March 31, 2011 |
HONEYCOMB STRUCTURE AND METHOD FOR MANUFACTURING THE SAME
Abstract
A honeycomb structure includes porous partition walls via which
a plurality of cells constituting through channels for a fluid are
partitioned; and an outer peripheral wall positioned in the
outermost periphery of the structure. Open frontal areas of
predetermined cells in an end face of the structure on a fluid
inlet side thereof and open frontal areas of remaining cells in an
end face of the structure on a fluid outlet side thereof have
plugged portions. The outward end faces of the plugged portions are
flat, the plugged portions do not have any bubble having a diameter
of 0.3 mm or more, and a value obtained by dividing the standard
deviation of the plugging depths of the plugged portions by the
average plugging depth of the plugged portions is 0.15 or less.
Inventors: |
KIMURA; Koji; (Nagoya-City,
JP) ; Nunome; Takuya; (Nagoya-City, JP) ;
Fujita; Shuhei; (Nagoya-City, JP) |
Assignee: |
NGK Insulators, Ltd.
Nagoya-City
JP
|
Family ID: |
43780689 |
Appl. No.: |
12/854399 |
Filed: |
August 11, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61247098 |
Sep 30, 2009 |
|
|
|
Current U.S.
Class: |
428/117 ;
264/267 |
Current CPC
Class: |
B29D 99/0089 20130101;
B29L 2031/608 20130101; B29C 43/18 20130101; Y10T 428/24157
20150115; B28B 11/007 20130101 |
Class at
Publication: |
428/117 ;
264/267 |
International
Class: |
B32B 3/12 20060101
B32B003/12; B29C 43/18 20060101 B29C043/18 |
Claims
1. A honeycomb structure comprising: porous partition walls via
which a plurality of cells constituting through channels for a
fluid are partitioned; and an outer peripheral wall positioned in
the outermost periphery of the structure, open frontal areas of
predetermined cells in an end face of the structure on a fluid
inlet side thereof and open frontal areas of remaining cells in an
end face of the structure on a fluid outlet side thereof being
provided with plugged portions, wherein the outward end faces of
the plugged portions are flat, the plugged portions do not have any
bubble having a diameter of 0.3 mm or more, and a value obtained by
dividing the standard deviation of the plugging depths of the
plugged portions by the average plugging depth of the plugged
portions is 0.15 or less.
2. The honeycomb structure according to claim 1, wherein the depths
of the plugged portions are from 3 to 12 mm.
3. The honeycomb structure according to claim 1, wherein the
predetermined cells and the remaining cells are alternately
arranged.
4. The honeycomb structure according to claim 1, wherein the
material of the partition walls and the plugged portions contains
at least one selected from the group consisting of cordierite,
mullite, alumina, silicon carbide and aluminum titanate.
5. A method for manufacturing a honeycomb structure in which the
honeycomb structure according to claim 1 is manufactured,
comprising: a masking process of attaching a sheet to one end face
of a formed honeycomb article comprising porous partition walls via
which a plurality of cells constituting through channels for a
fluid are partitioned and an outer peripheral wall positioned in
the outermost periphery of the article, and making holes in the
positions of the sheet superimposed on the cells in which plugged
portions are to be formed; a first press-in process of pressing the
end of the formed honeycomb article, to which the sheet is
attached, into a container in which a plugging material is
received, to press the plugging material into the cells via the one
end face of the formed honeycomb article through the holes formed
in the sheet; and a second press-in process of moving, along the
surface of the sheet, a press-in jig including a pressurization
member having a hardness of 60 to 90 degrees, having a plate-like
shape, chamfered along one side of the shape perpendicular to a
thickness direction and having a flat face disposed adjacent to the
chamfered face in parallel with the thickness direction, in a state
where an angle between a pressurization face which is the chamfered
face and the sheet is from 15 to 50.degree., to press, by the
pressurization face, the plugging material supplied between the
sheet and the pressurization face into the cells in which the
plugging material is charged, over the plugging material, through
the holes formed in the sheet.
6. The method for manufacturing the honeycomb structure according
to claim 5, wherein the length of the flat face in the thickness
direction of the pressurization member is a length of 20 to 40% of
the thickness of the pressurization member.
7. The method for manufacturing the honeycomb structure according
to claim 5, wherein the material of the pressurization member
contains a rubber.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a honeycomb structure and a
method for manufacturing the honeycomb structure, and more
particularly, it relates to a honeycomb structure which can
suppress deformation, cracking or the like due to a temperature
change and a method for manufacturing the honeycomb structure.
[0003] 2. Description of the Related Art
[0004] There is a rising need to remove fine particles or harmful
substances from an exhaust gas of an internal combustion engine, a
boiler or the like in consideration of an influence on environment.
In particular, regulations on the removal of the fine particles
(hereinafter referred to as a particulate matter (PM) sometimes)
discharged from a diesel engine tend to be strengthened in Europe,
United States and Japan. Moreover, a honeycomb structure is used as
a collecting filter for removing such a PM.
[0005] Examples of the filter used for such a purpose include a
honeycomb filter in which a plugged honeycomb structure is utilized
(see, e.g., Patent Documents 1 and 2). Here, the plugged honeycomb
structure comprises porous partition walls via which a plurality of
cells constituting through channels for a fluid (an exhaust gas, a
purified gas) are partitioned, and an outer peripheral wall
positioned in the outermost periphery of the structure. Open
frontal areas of predetermined cells in the end face of the filter
on a fluid (exhaust gas) inlet side thereof and open frontal areas
of remaining cells in the end face of the filter on a fluid
(purified gas) outlet side thereof have plugged portions. According
to such a honeycomb filter, the exhaust gas flows into the cells
through the end face of the filter on the exhaust gas inlet side
thereof, the exhaust gas which has flowed into the cells passes
through the partition walls, and the exhaust gas (the purified gas)
passed through the partition walls is discharged through the end
face of the filter on the exhaust gas outlet side thereof.
Moreover, when the exhaust gas passes through the partition walls,
the PM included in the exhaust gas is collected by the partition
walls, and the exhaust gas becomes the purified gas. [0006] [Patent
Document 1] JP-A-2009-40046 [0007] [Patent Document 2]
JP-A-2006-231162
SUMMARY OF THE INVENTION
[0008] Conventional honeycomb filters include a honeycomb filter in
which the outward end faces of the plugged portions are recessed, a
honeycomb structure in which plugged portions irregularly have
large bubbles therein and a honeycomb filter in which plugged
portions have non-uniform plugging depths. When the temperature of
the honeycomb filter is raised or lowered, a heat stress is
concentrated on a part of the honeycomb filter, thereby causing a
damage to the honeycomb filter sometimes.
[0009] The present invention has been developed in view of such a
conventional technology problem, and an object thereof is to
provide a honeycomb structure which can suppress cracking,
deformation or the like due to a temperature change, and a method
for manufacturing the honeycomb structure.
[0010] According to the present invention, there are provided a
honeycomb structure and a method for manufacturing the honeycomb
structure as follows.
[0011] [1] A honeycomb structure comprising: porous partition walls
via which a plurality of cells constituting through channels for a
fluid are partitioned; and an outer peripheral wall positioned in
the outermost periphery of the structure, open frontal areas of
predetermined cells in an end face of the structure on a fluid
inlet side thereof and open frontal areas of remaining cells in an
end face of the structure on a fluid outlet side thereof being
provided with plugged portions, wherein the outward end faces of
the plugged portions are flat, the plugged portions do not have any
bubble having a diameter of 0.3 mm or more, and a value obtained by
dividing the standard deviation of the plugging depths of the
plugged portions by the average plugging depth of the plugged
portions is 0.15 or less.
[0012] [2] The honeycomb structure according to [1], wherein the
depths of the plugged portions are from 3 to 12 mm.
[0013] [3] The honeycomb structure according to [1] or [2], wherein
the predetermined cells and the remaining cells are alternately
arranged.
[0014] [4] The honeycomb structure according to any one of [1] to
[3], wherein the material of the partition walls and the plugged
portions contains at least one selected from the group consisting
of cordierite, mullite, alumina, silicon carbide and aluminum
titanate.
[0015] [5] A method for manufacturing a honeycomb structure in
which the honeycomb structure according to any one of [1] to [4] is
manufactured, comprising: a masking process of attaching a sheet to
one end face of a formed honeycomb article comprising porous
partition walls via which a plurality of cells constituting through
channels for a fluid are partitioned and an outer peripheral wall
positioned in the outermost periphery of the article, and making
holes in the positions of the sheet superimposed on the cells in
which plugged portions are to be formed; a first press-in process
of pressing the end of the formed honeycomb article, to which the
sheet is attached, into a container in which a plugging material is
received, to press the plugging material into the cells via the one
end face of the formed honeycomb article through the holes formed
in the sheet; and a second press-in process of moving, along the
surface of the sheet, a press-in jig including a pressurization
member having a hardness of 60 to 90 degrees, having a plate-like
shape, chamfered along one side of the shape perpendicular to a
thickness direction and having a flat face disposed adjacent to the
chamfered face in parallel with the thickness direction, in a state
where an angle between a pressurization face which is the chamfered
face and the sheet is from 15 to 50.degree., to press, by the
pressurization face, the plugging material supplied between the
sheet and the pressurization face into the cells in which the
plugging material is charged, over the plugging material, through
the holes formed in the sheet.
[0016] [6] The method for manufacturing the honeycomb structure
according to [5], wherein the length of the flat face in the
thickness direction of the pressurization member is a length of 20
to 40% of the thickness of the pressurization member.
[0017] [7] The method for manufacturing the honeycomb structure
according to [5] or [6], wherein the material of the pressurization
member contains a rubber.
EFFECT OF THE INVENTION
[0018] According to the honeycomb structure of the present
invention, the outward end faces of the plugged portions (the end
faces directed to the outside of the honeycomb structure) are flat,
and the plugged portions do not have any bubble having a diameter
of 0.3 mm or more. Furthermore, the value obtained by dividing the
standard deviation of the plugging depths of the plugged portions
by the average plugging depth of the plugged portions is 0.15 or
less. Therefore, it is possible to remarkably decrease the
fluctuations of the heat capacity, thermal expansion (coefficient),
Young's modulus and the like in each of the plugged portions. When
a temperature change or the like occurs, a portion on which a
stress is concentrated can be inhibited from being generated, and
accordingly, the breakage, deformation or the like of the honeycomb
structure during the occurrence of the temperature change or the
like can be suppressed.
[0019] According to the method for manufacturing the honeycomb
structure of the present invention, after charging the plugging
material into the cells of the formed honeycomb article, the
press-in jig including the pressurization member having the formed
pressurization face is moved along the surface of the sheet in the
state where the angle between the pressurization face and the sheet
is from 15 to 50.degree., to further charge the plugging material.
Therefore, it is possible to manufacture the honeycomb structure in
which the outward end faces of the plugged portions (the end faces
directed to the outside of the honeycomb structure) are flat, and
the plugged portions do not have any bubble having a diameter of
0.3 mm or more. Furthermore, the value obtained by dividing the
standard deviation of the plugging depths of the plugged portions
by the average plugging depth of the plugged portions is 0.15 or
less.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1A is a perspective view schematically showing one
embodiment of a honeycomb structure of the present invention;
[0021] FIG. 1B is a plan view schematically showing the embodiment
of the honeycomb structure of the present invention;
[0022] FIG. 1C is a schematic diagram showing a cross section cut
along the A-A' line of FIG. 1B;
[0023] FIG. 2A is a schematic diagram showing a part of a process
in one embodiment of a method for manufacturing a honeycomb
structure of the present invention;
[0024] FIG. 2B is a schematic diagram showing a part of the process
in the embodiment of the method for manufacturing the honeycomb
structure of the present invention;
[0025] FIG. 2C is a schematic diagram showing a part of the process
in the embodiment of the method for manufacturing the honeycomb
structure of the present invention;
[0026] FIG. 2D is a schematic diagram showing a part of the process
in the embodiment of the method for manufacturing the honeycomb
structure of the present invention;
[0027] FIG. 2E is a schematic diagram showing a part of the process
in the embodiment of the method for manufacturing the honeycomb
structure of the present invention;
[0028] FIG. 2F is a schematic diagram showing the state of a formed
honeycomb article in a case where the plugging material is recessed
in the embodiment of the method for manufacturing the honeycomb
structure of the present invention;
[0029] FIG. 2G is a schematic diagram showing a part of the process
in the embodiment of the method for manufacturing the honeycomb
structure of the present invention;
[0030] FIG. 3A is a schematic diagram showing a part of the process
in the embodiment of the method for manufacturing the honeycomb
structure of the present invention;
[0031] FIG. 3B is a schematic diagram showing the cross section of
a press-in jig used in the embodiment of the method for
manufacturing the honeycomb structure of the present invention;
[0032] FIG. 3C is a schematic diagram showing a state where the
press-in jig is disposed in the end face of the formed honeycomb
article (the surface of the sheet) in another embodiment of the
method for manufacturing the honeycomb structure of the present
invention;
[0033] FIG. 4A is a side view schematically showing a first
press-in device in a manufacturing apparatus used in the embodiment
of the method for manufacturing the honeycomb structure of the
present invention;
[0034] FIG. 4B is a side view schematically showing the first
press-in device in the manufacturing apparatus used in the
embodiment of the method for manufacturing the honeycomb structure
of the present invention;
[0035] FIG. 5 is a side view schematically showing a device for
inverting the formed honeycomb article (an inverting device) in the
manufacturing apparatus used in the embodiment of the method for
manufacturing the honeycomb structure of the present invention;
[0036] FIG. 6 is a side view schematically showing a second
press-in device in the manufacturing apparatus used in the
embodiment of the method for manufacturing the honeycomb structure
of the present invention;
[0037] FIG. 7 is a schematic diagram showing the cross section of a
drying device in the manufacturing apparatus used in the embodiment
of the method for manufacturing the honeycomb structure of the
present invention;
[0038] FIG. 8A is a plan view schematically showing a honeycomb
structure 200 manufactured by another embodiment of the method for
manufacturing the honeycomb structure of the present invention;
and
[0039] FIG. 8B is a perspective view schematically showing the
honeycomb structure 200 manufactured by the embodiment of the
method for manufacturing the honeycomb structure of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0040] Hereinafter, a configuration for carrying out the present
invention will specifically be described, but it should be
understood that the present invention is not limited to the
following embodiment, and is appropriately subjected to design
change, improvement or the like based on the ordinary knowledge of
a person with ordinary skill in the art without departing from the
scope of the present invention.
[0041] (1) Honeycomb Structure:
[0042] As shown in FIGS. 1A to 1C, one embodiment of a honeycomb
structure of the present invention comprises porous partition walls
3 via which a plurality of cells 2 constituting through channels
for a fluid are partitioned; and an outer peripheral wall 4
positioned in the outermost periphery of the structure. Open
frontal areas of the predetermined cells 2 in an end face 11 of the
structure on a fluid inlet side thereof and open frontal areas of
the remaining cells 2 in an end face 12 of the structure on a fluid
outlet side thereof have plugged portions 5. Outer end faces 7 of
the plugged portions 5 are flat, the plugged portions 5 do not have
any bubble having a diameter of 0.3 mm or more, and a value
obtained by dividing the standard deviation of plugging depths 8 of
the plugged portions 5 by the average plugging depth of the plugged
portions 5 is 0.15 or less.
[0043] Here, `the outer end faces 7` of the plugged portions 5 are,
as shown in FIG. 1C, the end faces directed to the outside of the
honeycomb structure 100 (exposed to the outside) to face an outer
space, among the end faces of the plugged portions 5. It is to be
noted that among the end faces of the plugged portions 5, end faces
opposite to `the outer end faces 7` are `inward end faces 7a` shown
in FIG. 1C. Moreover, `the outer end faces 7 of the plugged
portions 5 are flat` mean a state where any recess having a depth
larger than 0.3 mm or any protrusion of 0.3 mm or more is not
formed in the outer end faces 7 of the plugged portions 5.
Moreover, `bubbles` are spaces formed in the plugged portions 5 and
having a diameter of 0.3 mm or more. Furthermore, the
presence/absence of the bubbles is judged by enlarging, twice, the
cross section of each of the plugged portions 5 cut along the plane
including the central axis thereof to observe the cross section
with a microscope and judging whether or not the space having a
diameter of 0.3 mm or more is formed. The diameter of each bubble
is seen in `the cross section of the plugged portion 5 cut along
the plane of the plugged portion 5 including the central axis
thereof`. The diameter of the bubble is a value measured in a state
where the bubble is enlarged twice by an optical microscope. `The
diameter of the bubble in the cross section of the plugged portion
5 cut along the plane of the plugged portion 5 including the
central axis thereof` is a corresponding diameter calculated from
the area of the bubble in the cross section. `The corresponding
diameter calculated from the area of the bubble` is the diameter of
`a circular shape` having an area equal to that of the bubble in
the cross section. Moreover, `the standard deviation of the
plugging depths 8 of the plugged portions 5` is the standard
deviation of the plugging depths 8 of 20 plugged portions, when the
20 plugged portions are arbitrarily selected. Moreover, `the
average plugging depth of the plugged portions 5` means the average
value of the plugging depths of the 20 plugged portions from which
`the standard deviation of the plugging depths 8 of the plugged
portions 5` is calculated as described above. Moreover, `the depths
of the plugged portions 5` mean the lengths of the plugged portions
5 in the extending direction of the cells 2.
[0044] FIG. 1A is a perspective view schematically showing one
embodiment of the honeycomb structure of the present invention.
FIG. 1B is a plan view schematically showing the embodiment of the
honeycomb structure of the present invention. FIG. 1C is a
schematic diagram showing a cross section cut along the A-A' line
of FIG. 1B.
[0045] Thus, in a honeycomb structure 100 of the present
embodiment, the outward end faces 7 of the plugged portions 5 (the
end faces directed to the outside of the honeycomb structure) are
flat, and the plugged portions 5 do not have any bubble having a
diameter of 0.3 mm or more. Furthermore, the value obtained by
dividing the standard deviation of the plugging depths 8 of the
plugged portions 5 by the average plugging depth of the plugged
portions is 0.15 or less. Therefore, it is possible to decrease the
fluctuations of the heat capacity, thermal expansion (coefficient),
Young's modulus and the like in each of the plugged portions. When
a temperature change or the like occurs, a portion on which a
stress is concentrated can be inhibited from being generated, and
accordingly, the generation of the breakage, deformation or the
like during the occurrence of the temperature change or the like
can be suppressed.
[0046] In the honeycomb structure of the present embodiment, the
outer end faces 7 of the plugged portions 5 are flat. In
consequence, during the regeneration of the honeycomb structure or
the like, `the distribution (fluctuation) of heat based on the
irregularities of the end faces of the plugged portions` decreases,
and a thermal shock resistance improves. Measurement for judging
whether or not the outer end faces 7 of the plugged portions 5 of
the honeycomb structure are flat (flatness) are performed by a
laser microscope.
[0047] In the honeycomb structure of the present embodiment, the
plugged portions 5 do not have any bubble having a diameter of 0.3
mm or more. In consequence, the plugged portions substantially have
a solid structure. During the regeneration of the honeycomb
structure or the like, the distribution (fluctuation) of the heat
of the plugged portions in the end face of the honeycomb structure
decreases, and the thermal shock resistance improves.
[0048] In the honeycomb structure of the present embodiment, the
value obtained by dividing `the standard deviation of the plugging
depths 8 of the plugged portions 5` by `the average plugging depth
of the plugged portions 5` is 0.15 or less, preferably from 0.03 to
0.1. In consequence, during the regeneration of the honeycomb
structure or the like, the distribution (fluctuation) of the heat
of the plugged portions in the end face of the honeycomb structure
decreases, and the thermal shock resistance improves. Moreover, the
depths of the plugged portions entirely become uniform, and hence
the PM collection areas of the partition walls can easily be
controlled, so that the fluctuations of the PM collection
performances of honeycomb structure products can be decreased. When
the value obtained by dividing `the standard deviation of the
plugging depths 8 of the plugged portions 5` by `the average
plugging depth of the plugged portions 5` is larger than 0.15,
during the regeneration of the honeycomb structure or the like, the
distribution (fluctuation) of the heat of the plugged portions in
the end face of the honeycomb structure increases, and the thermal
shock resistance deteriorates. Moreover, since the depths of the
plugged portions entirely become non-uniform, and hence the PM
collection areas of the partition walls cannot easily be
controlled, with the result that the fluctuations of the PM
collection performances of honeycomb structure products
increase.
[0049] In the honeycomb structure of the present embodiment, the
depths 8 of the plugged portions 5 are preferably from 3 to 12 mm,
further preferably from 5 to 10 mm. When the depths are smaller
than 3 mm, the strength of the plugged portions 5 deteriorates
sometimes. When they are larger than 12 mm, the PM collection areas
of the partition walls 3 decrease sometimes.
[0050] In the honeycomb structure 100 of the present embodiment,
open frontal areas of predetermined cells 2 in the end face 11 on a
fluid inlet side and open frontal areas of remaining cells in the
end face 12 on a fluid outlet side have the plugged portions 5.
Moreover, the predetermined cells and the remaining cells are
alternately arranged (side by side), and the plugged portions and
`the open frontal areas of the cells` preferably form checked
patterns in the inlet side end face 11 and the outlet side end face
12.
[0051] In the honeycomb structure of the present embodiment, the
material of the partition walls 3 and the plugged portions 5
preferably contains at least one selected from the group consisting
of cordierite, mullite, alumina, silicon carbide and aluminum
titanate. Moreover, the material of the partition walls 3 and the
plugged portion 5 is further preferably at least one selected from
the group consisting of cordierite, mullite, alumina, silicon
carbide and aluminum titanate, and the material of the partition
walls 3 and the plugged portion 5 is especially preferably one
selected from the group consisting of cordierite, mullite, alumina,
silicon carbide and aluminum titanate. Furthermore, the material of
the plugged portions 5 is preferably the same as that of the
partition walls 3.
[0052] In the honeycomb structure 100 of the present embodiment,
the average pore diameter of the partition walls 3 is preferably
from 10 to 40 .mu.m, further preferably from 10 to 30 .mu.m. With
the average pore diameter smaller than 10 .mu.m, even when a less
amount of particulate matter is deposited, a pressure loss
increases sometimes. When it is larger than 40 .mu.m, the honeycomb
structure 100 becomes brittle and easily breaks down sometimes. The
average pore diameter of the partition walls 3 is a value measured
with a mercury porosimeter.
[0053] In the honeycomb structure 100 of the present embodiment,
the porosities of the partition walls 3 are preferably from 30 to
70%, further preferably 35 to 60%. When the porosities are smaller
than 30%, the pressure loss increases sometimes. When they are
larger than 70%, the honeycomb structure 100 becomes brittle and
easily breaks down sometimes. The porosities of the partition walls
3 are values measured with the mercury porosimeter.
[0054] In the honeycomb structure 100 of the present embodiment,
the thicknesses of the partition walls 3 are preferably from 200 to
300 .mu.m, further preferably from 250 to 300 .mu.m. When the
thicknesses are smaller than 200 .mu.m, the strength of the
honeycomb structure 100 deteriorates sometimes. When they are
larger than 300 .mu.m, the pressure loss during the passage of the
exhaust gas through the cells increases sometimes.
[0055] In the honeycomb structure 100 of the present embodiment,
the cell density of the cross section perpendicular to the cell
extending direction is preferably from 46.5 to 62.0 cells/cm.sup.2.
When the cell density is smaller than 46.5 cells/cm.sup.2, the
strength of the honeycomb structure 100 deteriorates sometimes.
When it is larger than 62.0 cells/cm.sup.2, the pressure loss
increases sometimes.
[0056] In the honeycomb structure 100 of the present embodiment,
there is not any special restriction on a cell shape, but the cell
shape is a polygonal shape such as a triangular, quadrangular,
pentangular or hexagonal shape, a circular shape or an elliptic
shape, or may be another irregular shape in the cross section
perpendicular to the cell extending direction. Moreover, a
combination of these shapes may be used. Furthermore, in the cross
section of the honeycomb structure 100 perpendicular to the cell
extending direction, the sectional areas of the cells are
preferably equal, but the sectional areas of the predetermined
cells 2 including the plugged portions 5 on the side of the inflow
side end face 11 (the sectional areas in the cross section of the
structure perpendicular to the cell extending direction) are
smaller than the sectional areas of the remaining cells 2 including
the plugged portions 5 on the side of the outflow side end face
(the sectional areas in the cross section of the structure
perpendicular to the cell extending direction) in a preferable
configuration.
[0057] There is not any special restriction on the outer shape of
the honeycomb structure 100 of the present embodiment, but examples
of the outer shape include a cylindrical shape, an elliptic tubular
shape, `a tubular shape with a bottom surface having a polygonal
shape, e.g., a square tubular shape or the like`, and a tubular
shape with a bottom surface having an irregular shape. Moreover,
there is not any special restriction on the size of the honeycomb
structure 100, but the honeycomb structure is formed so that the
ratio of the length of the formed honeycomb article in the axial
direction with respect to the outer diameter of the formed
honeycomb article (the length/the outer diameter) is preferably
from 0.1 to 0.8, further preferably from 0.1 to 0.6. Furthermore,
when the honeycomb structure 100 has another shape, the area of the
bottom surface thereof is preferably in the same range as that of
the bottom surface of the above cylindrical shape. In addition, in
FIG. 1, all the cells have a square shape and an equal size, but as
in the shape of a honeycomb structure 200 shown in FIGS. 8A and 8B,
the sizes of the adjacent cells of the honeycomb structure may be
changed to increase a PM collection capacity. In the cross section
of the honeycomb structure 200 perpendicular to the cell extending
direction shown in FIGS. 8A and 8B, cells having large sectional
areas and cells having small sectional areas are alternately
arranged. FIG. 8A is a plan view schematically showing another
embodiment of the honeycomb structure of the present invention.
FIG. 8B is a perspective view schematically showing the other
embodiment of the honeycomb structure of the present invention.
[0058] In the honeycomb structure 100 of the present embodiment,
the outer peripheral wall positioned in the outermost periphery may
be an integrally formed wall formed integrally with the formed
honeycomb article during forming, or a cement coat wall formed by
grinding the outer periphery of the formed honeycomb article into a
predetermined shape after the forming, and making an outer
peripheral wall of cement or the like. When the outer peripheral
wall is the integrally formed wall, the thickness of the outer
peripheral wall is preferably from 0.5 to 1.5 mm. This also applies
to a case where the outer peripheral wall is the cement coat wall.
Moreover, when the outer peripheral wall is the cement coat wall,
examples of the material of the cement coat wall is a material
obtained by adding a flux component such as glass to a common raw
material.
[0059] In the honeycomb structure 100 of the present embodiment, a
catalyst for burning and removing the particulate matter, a
catalyst for removing a harmful substance such as NO.sub.x from the
exhaust gas or the like may be loaded on the surfaces of the
partition walls 3 in accordance with a use application.
[0060] (2) Method for manufacturing Honeycomb Structure:
[0061] Next, one embodiment of the method for manufacturing the
honeycomb structure of the present invention will be described. The
method for manufacturing the honeycomb structure of the present
invention is a method for manufacturing the above honeycomb
structure of the present invention, and the above embodiment of the
honeycomb structure of the present invention can be manufactured by
the embodiment of the method for manufacturing the honeycomb
structure of the present invention.
[0062] First, a tubular formed honeycomb article is formed of a
ceramic forming material containing a ceramic material, and
comprises partition walls via which a plurality of cells
constituting through channels for a fluid are partitioned and an
outer peripheral wall positioned in the outermost periphery of the
article.
[0063] The ceramic material contained in the ceramic forming
material preferably contains at least one selected from the group
consisting of a cordierite forming material, cordierite, mullite,
alumina, silicon carbide and aluminum titanate, is further
preferably at least one selected from the group consisting of the
cordierite forming material, cordierite, mullite, alumina, silicon
carbide and aluminum titanate, and is especially preferably one
selected from the group consisting of the cordierite forming
material, cordierite, mullite, alumina, silicon carbide and
aluminum titanate. It is to be noted that the cordierite forming
material is a ceramic material obtained by blending a chemical
composition in a range of 42 to 56 mass % of silica, 30 to 45 mass
% of alumina and 12 to 16 mass % of magnesia, and the material is
fired to form cordierite.
[0064] Moreover, this ceramic forming material is preferably
prepared by mixing the above ceramic material with a dispersion
medium, an organic binder, an inorganic binder, a pore former, a
surfactant and the like.
[0065] To form the article of the ceramic forming material, the
forming material is first kneaded to obtain a kneaded clay, and the
obtained kneaded clay is preferably formed into a honeycomb shape.
There is not any special restriction on a method for kneading the
forming material to form the kneaded clay, but examples of the
method include methods in which, for example, a kneader, a vacuum
clay kneader and the like are used. There is not any special
restriction on a method for forming the formed honeycomb article of
the kneaded clay, and a heretofore known forming method such as
extrusion forming or injection forming may be used. Preferable
examples of the method include a method for extrusion-forming the
formed honeycomb article by use of a die having a desirable cell
shape, partition wall thickness and cell density. As the material
of the die, a hard alloy which does not easily wear is
preferable.
[0066] Moreover, after the above forming, the resultant formed
honeycomb article may be dried. There is not any special
restriction on a drying method, but examples of the method include
hot air drying, microwave drying, dielectric drying, reduced
pressure drying, vacuum drying and freeze drying. Above all, the
dielectric drying, microwave drying and hot air drying are
preferably performed alone or as a combination of them. Moreover,
drying conditions are preferably set to a drying temperature of 80
to 150.degree. C. and a drying time of five minutes to two
hours.
[0067] Next, the resultant formed honeycomb article is preferably
fired. It is to be noted that the firing may be performed after
forming the plugged portions in the formed honeycomb article.
[0068] Moreover, the formed honeycomb article is preferably
calcinated before firing (finally firing) the formed honeycomb
article. The calcinating is performed for degreasing, and there is
not any special restriction on a calcinating method as long as an
organic substance (the organic binder, dispersion medium, pore
former or the like) contained in the formed honeycomb article can
be removed. In general, the burning temperature of the organic
binder is from about 100 to 300.degree. C., and the burning
temperature of the pore former is from about 200 to 800.degree. C.,
whereby as calcinating conditions, the article is preferably heated
in an oxidizing atmosphere at about 200 to 1000.degree. C. for
about 3 to 100 hours.
[0069] The formed honeycomb article is fired (finally fired) to
sinter and densify the forming material constituting the formed and
calcinated article, thereby acquiring a predetermined strength.
Firing conditions (temperature, time and atmosphere) vary in
accordance with the type of the forming material, and hence
appropriate conditions may be selected in accordance with the type
of the forming material. When, for example, the cordierite forming
material is used, a firing temperature is preferably from 1410 to
1440.degree. C. Moreover, a firing time is preferably from four to
six hours.
[0070] Next, a plugging material is charged into the open frontal
areas of the predetermined cells (first cells) in the end face of
the formed honeycomb article on the fluid inlet side thereof, and
the open frontal areas of the remaining cells (second cells) in the
end face of the article on the fluid outlet side thereof, whereby
the above embodiment of the honeycomb structure of the present
invention is preferably obtained which has the plugged portions in
the open frontal areas of the predetermined cells (the first cells)
in the end face of the article on the fluid inlet side thereof and
the open frontal areas of the remaining cells (the second cells) in
the end face of the article on the fluid outlet side thereof.
[0071] Examples of a method for charging the plugging material into
the formed honeycomb article include a method comprising a masking
process of attaching a sheet to one end face of a formed honeycomb
article comprising porous partition walls via which a plurality of
cells constituting through channels for a fluid are partitioned and
an outer peripheral wall positioned in the outermost periphery of
the article, and making holes in the positions of the sheet
superimposed on the cells in which plugged portions are to be
formed; a first press-in process of pressing the end of the formed
honeycomb article to which the sheet is attached into a container
in which a plugging material is received to press the plugging
material into the cells via the one end face of the formed
honeycomb article through the holes formed in the sheet; and a
second press-in process of moving, along the surface of the sheet,
a press-in jig including `a pressurization member having a
plate-like shape and having a face chamfered along one side of the
shape perpendicular to a thickness direction and a flat face
disposed adjacent to the chamfered face in parallel with the
thickness direction`, to press, by a pressurization face which is
the chamfered face, the plugging material supplied between the
sheet and the pressurization face into the cells in which the
plugging material is charged, over the plugging material, through
the holes formed in the sheet. Moreover, after forming the plugged
portions in the one end face, the plugged portions are also formed
in the other end face by a similar method, to obtain the honeycomb
structure of the present invention.
[0072] Hereinafter, the method for charging the plugging material
into the formed honeycomb article will be described in more
detail.
[0073] First, as shown in FIGS. 2A and 2B, a sheet 21 is attached
to one end face of a formed honeycomb article 22 comprising porous
partition walls via which a plurality of cells constituting through
channels for a fluid are partitioned and an outer peripheral wall
positioned in the outermost periphery of the article, and holes 28
are made in positions of the sheet 21 superimposed on the cells in
which plugged portions are to be formed (the masking process). FIG.
2A is a schematic diagram showing a part of the process in one
embodiment of the method for manufacturing a honeycomb structure of
the present invention. FIG. 2B is a schematic diagram showing a
part of the process in the embodiment of the method for
manufacturing the honeycomb structure of the present invention.
[0074] As the material of the sheet 21, a polyester-based resin is
preferable. Above all, polyethylene terephthalate (PET) is further
preferable. The thickness of the sheet 21 is preferably from 30 to
70 .mu.m.
[0075] To form the holes 28 in the sheet 21, the end face of the
formed honeycomb article 22 is preferably beforehand photographed
by an image pickup device to acquire image data with which the
shapes and positions of the cells in which the plugged portions are
to be formed and the cells in which the plugged portions are not to
be formed can be specified. Moreover, holes are preferably made in
`the portions of the sheet superimposed on the cells in which the
plugged portions are to be formed` based on the acquired image data
by a laser. There is not any special restriction on the image
pickup device, but examples of the device include a charge-coupled
device (CCD) camera and a complementary metal oxide semiconductor
(CMOS) sensor.
[0076] Next, as shown in FIG. 2C, the end of the formed honeycomb
article 22 to which the sheet is attached is pressed into a
container (a container for plugging) 23 in which a plugging
material 24 is received to press the plugging material 24 into
cells 25 via the one end face of the formed honeycomb article 22
through the holes formed in the sheet (the first press-in process).
Moreover, after pressing the plugging material 24 into the cells
25, as shown in FIG. 2D, the formed honeycomb article is extracted
from the container 23 for plugging. To press the end of the formed
honeycomb article 22 into the container 23 for plugging, the end of
the formed honeycomb article 22 is directed downwards in a vertical
direction, and the formed honeycomb article 22 is preferably moved
downwardly in the vertical direction. FIG. 2C is a schematic
diagram showing a part of the process in the embodiment of the
method for manufacturing the honeycomb structure of the present
invention. FIG. 2D is a schematic diagram showing a part of the
process in the embodiment of the method for manufacturing the
honeycomb structure of the present invention.
[0077] As the plugging material, a material used as the material of
the partition walls is preferably used, and the amount of the
dispersion medium is preferably regulated so that the viscosity of
the material at 25.degree. C. is from 100 to 300 dPas.
[0078] In the first press-in process, as shown in FIGS. 4A and 4B,
it is preferable to use a first press-in device 31 comprising the
container 23 for plugging in which the plugging material is
received, and press-in means 26 for pressing, into the container 23
for plugging in which the plugging material is received, the end of
the formed honeycomb article 22 including the porous partition
walls via which a plurality of cells constituting the through
channels for the fluid are partitioned and the outer peripheral
wall positioned in the outermost periphery of the article, to
charge the plugging material into the cells through the end face of
the formed honeycomb article 22. FIG. 4A is a side view
schematically showing the first press-in device in a manufacturing
apparatus used in one embodiment of a method for manufacturing the
honeycomb structure of the present invention. FIG. 4B is a side
view schematically showing the first press-in device in the
manufacturing apparatus used in the embodiment of the method for
manufacturing the honeycomb structure of the present invention.
[0079] There is not any special restriction on the container 23 for
plugging, in which the plugging material is received, as long as
the one end of the formed honeycomb article can be inserted into
the container 23 for plugging, to charge, into the cells, the
plugging material received in the container 23 for plugging. There
is not any special restriction on the material of the container 23
for plugging, but stainless steel or the like may be used.
Moreover, the thickness of the container 23 for plugging is
preferably from 20 to 40 mm, and the inner diameter of the
container 23 for plugging is preferably from 101 to 105% of the
diameter of the end face of the formed honeycomb article.
[0080] The press-in means 26 preferably includes a grasping portion
which grasps the formed honeycomb article, and a pressurization
mechanism which moves the formed honeycomb article upwards and
downwards in the vertical direction in a state where the article is
grasped. Subsequently, the formed honeycomb article is preferably
pressed into the container 23 for plugging, by use of the
pressurization mechanism. There is not any special restriction on
the grasping portion, but examples of the grasping portion include
a grasping portion including two plates having mutually facing
surfaces which are provided with an elastic material such as rubber
so that the elastic material can come in contact with the formed
honeycomb article to sandwich the formed honeycomb article between
the two plates. Moreover, examples of the pressurization mechanism
include a mechanism which moves the grasping portion upwards and
downwards by a motor or the like.
[0081] Furthermore, the first press-in device 31 may have a
constitution in which the formed honeycomb article is fixed by the
press-in means 26, and the container 23 for plugging is moved
upwards and downwards in the vertical direction. In this case, the
container 23 for plugging is preferably disposed on a table, and
the table is moved upwards and downwards in the vertical direction
by the motor.
[0082] Next, as shown in FIG. 2E, the formed honeycomb article 22
is preferably inverted so that the end face of the article in which
the plugging material 24 is charged is directed upwardly in the
vertical direction. There is not any special restriction on a
method for inverting the formed honeycomb article 22, an inverting
device may be used, and the article may manually (manpower) be
inverted, but the inverting device is preferably used. FIG. 2E is a
schematic diagram showing a part of the process in the embodiment
of the method for manufacturing the honeycomb structure of the
present invention.
[0083] When the formed honeycomb article is inverted, an inverting
device 32 shown in FIG. 5 is preferably used. The inverting device
32 preferably comprises an inverting mechanism 32b which grasps and
inverts the formed honeycomb article 22 and an elevating mechanism
32a which moves the inverting mechanism 32b grasping the formed
honeycomb article 22 upwards and downwards. The elevating mechanism
32a and the inverting mechanism 32b are preferably driven by the
motor or the like. FIG. 5 is a side view schematically showing the
device which inverts the formed honeycomb article (the inverting
device) in the manufacturing apparatus used in the embodiment of
the method for manufacturing the honeycomb structure of the present
invention.
[0084] It is to be noted that in a state where the formed honeycomb
article is inverted to dispose the plugging material in the end
face of the article directed upwardly in the vertical direction, as
shown in FIG. 2F, the end face of the plugging material (the end
face directed to the upside of the vertical direction) is recessed,
and recess portions 27 are formed sometimes. However, in the method
for manufacturing the honeycomb structure of the present
embodiment, these recesses can be eliminated in the next second
press-in process. FIG. 2F is a schematic diagram showing the state
of the formed honeycomb article in a case where the plugging
material is recessed in the embodiment of the method for
manufacturing the honeycomb structure of the present invention.
[0085] Next, as shown in FIGS. 2G and 3A, a press-in jig 43
including `a pressurization member 41 having a hardness of 60 to 90
degrees, having a plate-like shape, chamfered along one side of the
shape perpendicular to a thickness direction and having a flat face
45 disposed adjacent to the chamfered face in parallel with the
thickness direction` is moved along the surface of the sheet 21, in
a state where an angle .theta.1 (hereinafter referred to as `the
attack angle .theta.1 sometimes) between a pressurization face 42
which is the chamfered face and the sheet is from 15 to 50.degree.,
to press, by the pressurization face 42, the plugging material
supplied between the sheet and the pressurization face into the
cells in which the plugging material is charged, over the plugging
material, through the holes formed in the sheet 21 (the second
press-in process). Thus, the plugging material is charged by the
pressurization face 42 in a state where the angle .theta.1 between
the pressurization face 42 of the pressurization member 41 and the
sheet is from 15 to 50.degree., whereby bubbles can be prevented
from being in the plugged portions, or recesses can be prevented
from being formed in the end faces of the plugged portions. FIG. 2G
is a schematic diagram showing a part of the process in the
embodiment of the method for manufacturing the honeycomb structure
of the present invention. FIG. 3A is a schematic diagram showing a
part of the process in the embodiment of the method for
manufacturing the honeycomb structure of the present invention.
[0086] The attack angle .theta.1 is from 15 to 50.degree.,
preferably 30 to 45.degree.. When the angle is smaller than
15.degree., the bubbles are undesirably formed in the plugged
portions. When it is larger than 50.degree., the bubbles are
undesirably formed in the plugged portions, or the recesses are
formed in the end faces of the plugged portions.
[0087] As shown in FIG. 3B, in the method for manufacturing the
honeycomb structure of the present embodiment, the press-in jig 43
includes `the pressurization member 41 having a hardness of 60 to
90 degrees, having a plate-like shape, chamfered along one side
(ridgeline) of the shape perpendicular to the thickness direction
and having the flat face 45 disposed adjacent to the chamfered face
(the pressurization face 42) in parallel with the thickness
direction`. Furthermore, the jig includes a support portion 44
which supports the end of the pressurization member 41 on the end
face side opposite to the flat face 45. The material of the support
portion 44 is preferably aluminum or stainless steel. Here,
`chamfered along the one side perpendicular to the thickness
direction` means that there is formed a state where the one side
and a part of two faces which sandwich the one side therebetween
are removed. Therefore, `the one side` in `chamfered along the one
side` has already been removed, and is not present in the
pressurization member. Moreover, in the pressurization member, `the
chamfered face (the pressurization face 42)` is formed by `removing
the one side and a part of the two faces which sandwich the one
side therebetween`. Therefore, the pressurization member has `the
chamfered face (the pressurization face 42)` formed by `removing
the one side and a part of the two faces which sandwich the one
side therebetween`. It is to be noted that the pressurization
member is `chamfered along the one side perpendicular to the
thickness direction`, but this expression specifies a position to
be chamfered, and it does not means that when the pressurization
member is manufactured, the process of `chamfering the member along
the one side perpendicular to the thickness direction` is
necessarily performed. As shown in FIG. 3B, the sectional shape of
the pressurization member 41 cut along a plane thereof
perpendicular to the pressurization face 42 and the flat face 45 is
pentangular. FIG. 3B is a schematic diagram showing the cross
section of the press-in jig used in the embodiment of the method
for manufacturing the honeycomb structure of the present
invention.
[0088] The hardness of the pressurization member 41 is from 60 to
90 degrees, preferably 60 to 80 degrees. When the hardness is lower
than 60 degrees, the pressurization member softens, whereby the
bubbles are unfavorably formed in the plugged portions, or the
recesses are formed in the end faces of the plugged portions. When
it is higher than 90 degrees, the pressurization member hardens,
whereby the bubbles are unfavorably formed in the plugged portions,
or the recesses are formed in the end faces of the plugged
portions. The hardness of the pressurization member is a value
measured by a method conforming to K6253.
[0089] Moreover, as shown in FIGS. 3A and 3B, in the cross section
of the pressurization member 41 of the press-in jig 43 cut along
the plane perpendicular to both the pressurization face 42 and the
flat face 45, a tilt angle (a small side angle) (a pressurization
face tilt angle) .theta.2 with respect to the flat face 45 of the
pressurization face 42 is preferably from 15 to 80.degree., further
preferably 30 to 75.degree.. The pressurization face tilt angle
.theta..sub.2 is an angle (the small side angle) formed between a
face extended from the flat face 45 to a pressurization face 42
side and the pressurization face 42.
[0090] Moreover, as to the flat face 45 of the pressurization
member 41, `a length B in the thickness direction of the
pressurization member 41` is preferably from 20 to 40% of the
thickness of the pressurization member 41. When the length is
smaller than 20%, the rigidity of the pressurization member
deteriorates, and the plugging material is not easily supplied to
the recess portions sometimes. When it is larger than 40%, the
rigidity rises, and plugging is completed sometimes while the
bubbles are left.
[0091] In the method for manufacturing the honeycomb structure of
the present invention, as shown in FIG. 3C, when the press-in jig
is moved along the surface of the sheet 21 attached to the end face
of the formed honeycomb article, an angle (a small side angle) (a
pressurization member tilt angle) .theta.3 formed between the
pressurization member and a normal line N of the sheet is
preferably from 0 to 30.degree.. Moreover, the pressurization
member tilt angle .theta.3 and the pressurization face tilt angle
.theta..sub.2 are preferably regulated in the above ranges to set
the attack angle .theta.1 to 15 to 50.degree.. Here, the
pressurization member tilt angle .theta.3 is formed between a line
extending in a direction perpendicular to the thickness direction
(a pressurization member reference line C) and the normal line N in
the cross section perpendicular to both the pressurization face and
the flat face, and it is the small side angle. Moreover, as shown
in FIG. 3C, the pressurization member tilt angle .theta.3 is the
angle of the pressurization member tilted so as to fall down along
a proceeding direction (a direction in which the press-in face is
formed). When the pressurization member tilt angle .theta.3 is
0.degree., the press-in jig is moved along the surface of the sheet
21 in a state where the flat face 45 comes in contact with the
sheet 21. Moreover, when the pressurization member tilt angle
.theta.3 is larger than 0.degree., the press-in jig is moved along
the surface of the sheet 21 in a state where the sheet 21 comes in
contact with a ridgeline with which the flat face 45 and the
pressurization face 42 come in contact. FIG. 3C is a schematic
diagram showing a state where the press-in jig is disposed on the
end face of the formed honeycomb article (the surface of the sheet)
in another embodiment of the method for manufacturing the honeycomb
structure of the present invention.
[0092] There is not any special restriction on the shape of the
pressurization face 42 constituting the pressurization member 41,
but the shape is preferably rectangular. The thickness of the
pressurization member 41 is preferably from 6 to 10 mm. Moreover,
the length of the pressurization member 41 in a direction
perpendicular to the thickness direction (a reference line
direction) in the cross section perpendicular to both the
pressurization face and the flat face (the length of the portion of
the member which is not supported by the support portion 44) is
preferably from 15 to 25 mm. Furthermore, the length of the
pressurization member 41 in a direction perpendicular to both the
thickness direction and the reference line direction is preferably
from (D+10) to (D+20) mm, in which D (mm) is the diameter of the
formed honeycomb article as a plugging material charging target.
The pressurization face 42 preferably has such a size that when the
pressurization face is moved along the end face of the formed
honeycomb article, the face moves over the whole end face of the
formed honeycomb article (the upside of the vertical
direction).
[0093] The material of the pressurization member 41 preferably
contains a rubber, and is specifically preferably urethane rubber
or silicone rubber.
[0094] When the plugging material is charged by the press-in jig
43, the press-in jig 43 is preferably moved along the surface of
the sheet 21 while pressing the end face of the formed honeycomb
article by the press-in jig 43. At this time, the pressure to press
the end face of the formed honeycomb article by the press-in jig 43
(downwardly in the vertical direction) is preferably from 0.2 to
0.5 MPa, further preferably from 0.3 to 0.5 MPa. When the pressure
is smaller than 0.2 MPa, the plugging material is not easily
charged. When it is larger than 0.5 MPa, the end of the formed
honeycomb article easily breaks down.
[0095] When the press-in jig 43 is moved along the end face of the
formed honeycomb article 22 (the surface of the sheet), a moving
speed is preferably from 100 to 400 mm/second. When the speed is
lower than 100 mm/second, the amount of the plugging material to be
supplied decreases, and a recessed shape is easily left in the
surface of the structure, which deteriorates the production
efficiency of the honeycomb structure sometimes. When the speed is
higher than 400 mm/second, the plugging material is not easily
uniformly charged into the cells of the honeycomb structure
sometimes.
[0096] The plugging material used in the second press-in process is
preferably the same as the plugging material used in the first
press-in process.
[0097] In the second press-in process, a second press-in device 34
shown in FIG. 6 is preferably used which comprises the press-in jig
43 including a pressurization member having a formed pressurization
face, and further presses, by the pressurization member, the
plugging material into the cells over the plugging material charged
in the cells of the formed honeycomb article 22. It is to be noted
that the second press-in process may be performed manually without
using the second press-in device 34. FIG. 6 is a side view
schematically showing the second press-in device of the
manufacturing apparatus used in the embodiment of the method for
manufacturing the honeycomb structure of the present invention.
[0098] As shown in FIG. 6, the second press-in device 34 preferably
comprises a fixing table 37 for fixing the formed honeycomb article
22. The fixing table 37 shown in FIG. 6 includes a table portion
37a and a leg portion 37b. In the table portion 37a, there is
preferably formed a hole into which the end of the formed honeycomb
article can be inserted. Moreover, the formed honeycomb article is
preferably inserted into the hole, and fixed in a state where the
end face of the formed honeycomb article is positioned on the same
plane as the upper surface of the table portion 37a (the surface
directed upwardly in the vertical direction), and the plugging
material is preferably charged into the cells in this state.
[0099] When the second press-in process is performed using the
second press-in device 34, the formed honeycomb article having the
one end face side in which the plugging material is charged is
fixed to the fixing table 37 so as to fix the one end face side
thereof to the table portion 37a. Afterward, the press-in jig
including `the pressurization member having the plate-like shape,
chamfered along one side of the shape perpendicular to the
thickness direction and having the flat face disposed adjacent to a
chamfered face in parallel with the thickness direction is moved
along the surface of the sheet in a state where the attack angle
.theta.1 is from 15 to 50.degree., to press, by the pressurization
face, the plugging material supplied between the sheet and the
pressurization face into the cells in which the plugging material
is charged, over the plugging material, through the holes formed in
the sheet.
[0100] Moreover, the press-in jig 43 is preferably moved by a
pressurization mechanism for moving the jig in a direction
perpendicular to the end face of the formed honeycomb article
(upwards and downwards in the vertical direction), and a driving
mechanism for moving the jig along the end face of the formed
honeycomb article (the surface of the sheet). The pressurization
mechanism is preferably a mechanism for moving the pressurization
member upwards and downwards in the vertical direction by an air
pressure, an oil pressure or the like. The driving mechanism is
preferably a mechanism for moving the jig in a horizontal direction
by the motor or the like.
[0101] Next, the plugging material charged in the formed honeycomb
article is preferably dried to form the plugged portions (a drying
process). In the drying process, a drying device 38 shown in FIG. 7
is preferably used. FIG. 7 is a side view schematically showing the
drying device 38 in the embodiment of the manufacturing apparatus
of the honeycomb structure of the present invention.
[0102] Examples of the drying device include a hot air drying
device, a hot plate and a far infrared drier. A drying temperature
is preferably from 150 to 200.degree. C. A drying time is
preferably from one to three minutes.
[0103] In the method for manufacturing the honeycomb structure of
the present invention, after forming the plugged portions in the
predetermined cells of one end face of the formed honeycomb
article, the plugged portions are preferably formed in the
remaining cells of the other end face of the article by the same
method, to obtain the honeycomb structure of the present
invention.
EXAMPLES
[0104] Hereinafter, the present invention will further specifically
be described with respect to examples, but the present invention is
not limited to these examples.
Example 1
[0105] A plurality of components selected from the group consisting
of talc, kaolin, calcinated kaolin, alumina, aluminum hydroxide and
silica were combined to prepare a cordierite forming material at a
predetermined ratio so that a chemical composition of the material
contained 42 to 56 mass % of SiO.sub.2, 30 to 45 mass % of
Al.sub.2O.sub.3 and 12 to 16 mass % of MgO. To 100 parts by mass of
the cordierite forming material, as a pore former, 10 to 20 parts
by mass of graphite was added. Furthermore, appropriate amounts of
methyl celluloses and a surfactant were added thereto,
respectively, to prepare a kneaded clay. The prepared kneaded clay
was subjected to vacuum deaeration, and extruded to obtain a formed
honeycomb article comprising partition walls via which a plurality
of cells were partitioned and an outer peripheral wall.
[0106] Next, the resultant formed honeycomb article was dried at
180.degree. C. for three minutes, and fired at 1420.degree. C. for
five hours. The resultant formed honeycomb article had a partition
wall thickness of 0.3 mm, a cell density of 46.5 cells/cm.sup.2, a
porosity (a partition wall porosity) of 45% and an average pore
diameter (a partition wall average pore diameter) of 25 .mu.m. The
porosity and average pore diameter were measured with a mercury
porosimeter.
[0107] Next, plugged portions were formed in the resultant formed
honeycomb article to form checkered patterns in both the end faces,
thereby obtaining a honeycomb structure. The plugged portions were
formed appropriately using devices (a first press-in device 31, a
second press-in device 34, an inverting device 32 and a drying
device 38) shown in FIGS. 4A to 7. The first press-in device 31 has
a holding portion capable of holding and transferring the formed
honeycomb article, a plugging material supply mechanism and a
pressurization mechanism. The device holds the formed honeycomb
article while the press-in face of the article is disposed on the
downside. After supplying the desirable amount of the plugging
material to a container 23, the device pressurizes the end face of
the formed honeycomb article opposite to the press-in face thereof
to press the plugging material into the article. The inverting
device 32 has a holding portion capable of holding and transferring
the formed honeycomb article, a rotation mechanism and a driving
mechanism. In the second press-in device, the press-in face of the
article needs to be disposed on the upside in a vertical direction,
and hence the inverting device removes the formed honeycomb article
from the container 23, and rotates the formed honeycomb article to
direct the press-in face of the article upwardly in the vertical
direction. Moreover, by the driving mechanism, the formed honeycomb
article can be installed in a conveyance mechanism of the second
press-in device. The second press-in device 34 comprises a
positioning mechanism for positioning and holding the formed
honeycomb article in a desirable position, a supply mechanism for
supplying the desirable amount of the plugging material, a
pressurization member, a driving mechanism for the pressurization
member, and a conveyance mechanism, and the device presses the
plugging material into the formed honeycomb article by the press-in
jig 43, thereby forming the plugged portions. The drying device 38
has a conveyance mechanism and a chamber portion, and performs
drying in a state where at least the plugged portions of the formed
honeycomb article are included in a chamber. The drying device
shown in FIG. 7 shows the only chamber portion. A plurality of
chamber portions may be disposed.
[0108] To form the plugged portions, first, a sheet was attached to
one end face of the formed honeycomb article, and holes were made
in positions of the sheet superimposed on the cells in which the
plugged portions were to be formed (a masking process). The
material of the sheet was polyethylene terephthalate (PET), and the
thickness thereof was 25 .mu.m. The holes were made in the sheet by
a laser.
[0109] Next, the end of the formed honeycomb article to which the
sheet was attached was pressed into a container for plugging, in
which a plugging material was received, to press the plugging
material into cells via the one end face of the formed honeycomb
article through the holes formed in the sheet (a first press-in
process). As the plugging material, 40 mass % of kaolin having an
average particle diameter of 5 .mu.m, 40 mass % of talc having an
average particle diameter of 40 .mu.m, 15 mass % of aluminum oxide
having an average particle diameter of 10 .mu.m and 5 mass % of
silica having an average particle diameter of 5 .mu.m were used as
main inorganic components. The viscosity of the plugging material
was 250 dPas at 25.degree. C.
[0110] Next, the plugging material was further pressed into the
cells in which `the plugging material was charged, over `the
existing plugging material (a second press-in process). The second
press-in process was performed using the second press-in device 34
shown in FIG. 6. The formed honeycomb article having the one end
face side in which the plugging material was charged was fixed to a
fixing table 37 so as to fix the one end face side thereof to a
table portion 37a. Afterward, the press-in jig including `a
pressurization member having a plate-like shape, chamfered along
one side perpendicular to a thickness direction, and having a flat
face disposed adjacent to a chamfered face in parallel with the
thickness direction` was moved along the surface of the sheet in a
state where an attack angle .theta.1 was from 15 to 50.degree., and
the plugging material supplied between the sheet and the
pressurization face was preferably pressed by the pressurization
face into the cells in which the plugging material was charged,
over the plugging material, through the holes formed in the sheet.
Moreover, when the press-in jig was moved along the surface of the
sheet, the jig was moved while pressing the end face of the formed
honeycomb article by the press-in jig. A pressure at this time (the
pressure) was set to 0.4 MPa. Moreover, the material of the
press-in jig was urethane rubber. Furthermore, the hardness of the
pressurization member was 70 degrees, and a pressurization face
tilt angle .theta..sub.2 was 45.degree.. In addition, a
pressurization member tilt angle .theta.3 was 5.degree., and an
attack angle .theta.1 was 40.degree.. Moreover, as to the flat face
of the pressurization member, a ratio (a flat end face ratio) of
`the length of the flat face in the thickness direction of the
pressurization member` with respect to the thickness of the
pressurization member was 30%. The hardness of the pressurization
member was a value measured by a method conforming to JIS
K6253.
[0111] Next, the plugged portions were dried using the drying
device to obtain the honeycomb structure. As the drying device, a
hot air drier was used. The drying temperature was set to
180.degree. C., and the drying time was set to three minutes.
[0112] As to the obtained honeycomb structure, `the
presence/absence of the bubble (having a diameter of 0.3 mm or
more) of the plugged portion` and `the presence/absence of the
recess (having a depth of 0.3 mm or more) of the surface (the end
face) of the plugged portion` were evaluated. Results are shown in
Table 1. In Table 1, `the hardness` indicates the hardness of the
pressurization member. `The bubble` indicates the presence/absence
of the bubble of the plugged portion. `The recess` indicates the
presence/absence of the recess in the surface (the end face) of the
plugged portion.
[0113] (Presence/Absence of Plugged Portion)
[0114] Each plugged portion is cut along `the plane of the plugged
portion including the central axis thereof`, and the cross section
is enlarged twice by a microscope, to observe whether or not a
bubble having a diameter of 0.3 mm or more is present.
[0115] (Presence/Absence of Recess of Surface (End Face) of Plugged
Portion)
[0116] The plugged portion is cut along `the plane of the plugged
portion including the central axis thereof`, and the cross section
is enlarged twice by a microscope, to observe whether or not a
recess having a depth of 0.3 mm or more is present in `the end face
(the surface) of the plugged portion directed to the outside of the
honeycomb structure`.
TABLE-US-00001 TABLE 1 Pressurization Pressurization Attack face
member Flat face angle tilt angle tilt angle Hardness ratio
.theta.1 (.degree.) .theta.2 (.degree.) .theta.3 (.degree.)
(degree) (%) Bubble Recess Ex. 1 50 50 0 70 25 None None Ex. 2 40
45 5 70 30 None None Ex. 3 15 20 5 60 40 None None Ex. 4 40 40 0 60
30 None None Ex. 5 40 55 10 80 30 None None C. E. 1 60 60 0 90 60
Present Present C. E. 2 10 55 65 70 20 Present None C. E. 3 40 45 5
50 30 Present Present C. E. 4 40 45 5 100 20 Present None
Example 2 to 5, Comparative Examples 1 to 4
[0117] Honeycomb structures were prepared in the same manner as in
Example 1 except that an attack angle .theta.1, a pressurization
face tilt angle .theta..sub.2, a pressurization member tilt angle
.theta.3, the hardness of a pressurization member and a flat end
face ratio were changed as shown in Table 1. In the same manner as
in Example 1, `the presence/absence of bubbles in plugged portions`
and `the presence/absence of recesses in the surfaces (end faces)
of the plugged portions` were evaluated. Results are shown in Table
1.
[0118] It is seen from Examples 1 to 3 and Comparative Examples 1
and 2 of Table 1 that when the attack angle is smaller than
15.degree., recesses are formed in the surfaces of the plugged
portions. Moreover, it is seen that when the attack angle exceeds
50.degree., the bubbles are formed in the plugged portions, and the
recesses are formed in the surfaces of the plugged portions.
Furthermore, it is seen from Examples 4 and 5 and Comparative
Examples 3 and 4 that when the hardness of the pressurization
member is lower than 60 degrees, the bubbles are formed in the
plugged portions, and the recesses are formed in the surfaces of
the plugged portions. In addition, it is seen that when the
hardness of the pressurization member is higher than 90 degrees,
the recesses are formed in the surfaces of the plugged
portions.
[0119] The honeycomb structure of the present invention can
suitably be utilized for the disposal of fine particles or harmful
substances in an exhaust gas from an internal combustion engine, a
boiler or the like. In addition, the honeycomb structure can also
be applied to a device for removing harmful substances from a
device which discharges a large amount of soot and smoke.
DESCRIPTION OF REFERENCE NUMERALS
[0120] 2: cell, 3: partition wall, 4: outer peripheral wall, 5:
plugged portion, 7: outward end face, 7a: inward end face, 8:
plugging depth, 11: end face on inlet side, 12: end face on outlet
side, 21: sheet, 22: formed honeycomb article, 23: container
(container for plugging), 24: plugging material, 25: cell, 26:
press-in means, 27: recess portion, 28: hole, 31: first press-in
device, 32: inverting device, 32a: elevating mechanism, 32b:
inverting mechanism, 33: plugging material before charging, 34:
second press-in device, 37: fixing table, 37a: table portion, 37b:
leg portion, 38: drying device, 41: pressurization member, 42:
pressurization face, 43: press-in jig, 44: support portion, 45:
flat face, 46: ridgeline, .theta.1: attack angle, .theta.2:
pressurization face tilt angle, .theta.3: pressurization member
tilt angle, N: normal line, C: pressurization member reference
line, and 100, 200: honeycomb structure
* * * * *