EP2452793B1

EP2452793B1 - Manufacturing method of plugged honeycomb structure

Info

Publication number: EP2452793B1
Application number: EP10251925.3A
Authority: EP
Inventors: Satoru Tanaka; Shuichi Ichikawa; Suguru Kodama
Original assignee: NGK Insulators Ltd
Current assignee: NGK Insulators Ltd
Priority date: 2010-11-12
Filing date: 2010-11-12
Publication date: 2014-04-23
Anticipated expiration: 2030-11-12
Also published as: PL2452793T3; EP2452793A1

Description

[Technical Field]

The present invention relates to a method for manufacturing a plugged honeycomb structure. More specifically, the present invention relates to a method for manufacturing a plugged honeycomb structure capable of being used for a filter such as diesel particulate filter and having predetermined cells plugged in an end face.

[Background Art]

As a dust-collecting filter represented by a diesel particulate filter (DPF), a ceramic filter is used. As the ceramic filter, there is known a plugged honeycomb structure having a large number of cells partitioned and formed by partition walls, functioning as fluid passages, and each plugged in only one end portion by plugging. Further, the plugged honeycomb structure may have a checkerwise pattern in the end face due to discontinuous disposition of plugging members.
Because of the disposition of the plugging members in a checkerwise pattern or the like, exhaust gas flowing into the structure from one end face and discharged from the other end face inevitably passes through the partition walls in the midst of the flow inside the plugged honeycomb structure. This enables the plugged honeycomb structure to trap particulate matter contained in exhaust gas in the partition walls with passing the exhaust gas flowing from one end face through the partition walls. As a result, gas purified by the removal of the particulate matter can be discharged.
The disposition of the plugging members, which is the key to the filter function of the plugged honeycomb structure, is performed in a step of filling the plugging material into end portions of predetermined cells. The filling of the plugging material is generally performed by immersion of an end face of the honeycomb structure in the plugging material (see Patent Document 1). At this time, a mask is applied to the opening of each of the cell end portions where the plugging material is not filled, and the plugging material is filled into the end portions of the predetermined cells.
After the plugging material is supplied into the cells, the filling of the plugging member is completed by separating the plugging material inside the cells from the plugging material outside the cells.
However, in conventional techniques, since the following two phenomena are caused, plugging of cell end portions with the plugging material becomes imperfect.
In the first place, when the plugging material inside the cells and the plugging material outside the cells are separated from each other, according to the movement of the plugging material outside the cells, the plugging material inside the cells are drawn out to make the filling of the plugging material imperfect. To cope with this, there have been devised techniques for compulsorily separating the continuity of the plugging material outside the cells and the plugging material inside the cells (see Patent Documents 2 to 4).
Patent Documents 2 and 3 each discloses a method for manufacturing a plugged honeycomb structure, where, after immersing an end face of the honeycomb structure in a plugging material contained in a storage container, the brim of the storage container is slid along the end face to compulsorily separate the plugging material filled into the cells and the plugging material outside the cells.
Further, Patent Document 4 discloses a method for manufacturing a plugged honeycomb structure, where, after immersing an end face of the honeycomb structure in a plugging material, air is supplied between the end face of the honeycomb structure and the plugging material present outside the cells to form an air layer. In this manufacturing method, the air layer compulsorily separates the continuity of the plugging material inside the cells and the plugging material outside the cells.
Next, even if the plugging material is once filled so as to plug the cell end portions, pressure toward inside or outside along the cell extension direction is applied on the plugging material, and a hole connecting the inside with the outside of the cell is formed in the plugging material filled in the cell end portion.
Patent Document 5 discloses a method for manufacturing a plugged honeycomb structure, where one end face of the honeycomb structure is immersed in a plugging material in a state that the other side cell end portions are open. This reduces the pressure repelling the flow of the plugging material into the cell end portions to make the flow of the plugging material into the cell end portions easy.

[Prior Art Document]

[Patent Document]

[Patent Document 1] JP-A-2001-300922
[Patent Document 2] JP-A-2006-272183
[Patent Document 3] JP-A-2004-290766
[Patent Document 4] JP-A-2004-25098
[Patent Document 5] JP-A-2008-55345

JP 2000 190312 describes a method of sealing cells of a ceramic molding according to the preamble of claim 1 by bringing a mask with openings in a sealing pattern into contact with an end face of the molding, then filling sealing paste into the cells of the molding through said openings, reducing a paste sectional area in the end face of the cells, and then separating the mask from the end face.
An agitating piece is vertically moved while pressurizing it from a sealing paste discharging tank, the tank having a mask provided at its side face and formed with openings in a sealing pattern. Sealing paste is supplied and discharged from the openings of the mask, thereby allowing the paste to intrude into an end of the cells of the ceramic molding.
The sectional area of the paste at an end face of the cells is then reduced by operating or displacing the mask along the end face of the molding. Then the mask can be separated from the end face of the molding in the paste sectional area reduced state.
However, in recent years, there has been a tendency of decreasing the porosity of the ceramic honeycomb structure in order to manufacture a DPF having high strength and high durability or a tendency of downsizing the honeycomb structure as a DPF for a small-sized vehicle, and the techniques of Patent Documents 1 to 5 cannot cope with the tendencies. This is because, in a downsized honeycomb structure or a honeycomb structure having reduced porosity, pressure applied on the plugging material filled in the cell end portions so as to eject the material to the outside of the cells becomes high to make filling of the plugging material difficult and causes a hole connecting the inside with the outside of the cells in the plugging material even if the plugging material is filled into the cell end portions.
The manufacturing method of Patent Document 5 has a drawback of productivity since the step of removing the mask provided on the cell end portion on the side opposite to the end portion immersed in the plugging material. In addition, since the manufacturing method of Patent Document 5 is on the assumption that pressure leaks out from the partition walls, the effect is not exhibited in the aforementioned honeycomb structure having reduced porosity.
In view of the above problem, the present invention aims to provide a method for manufacturing a plugged honeycomb structure, where a plugging material is filled into cell end portions of a honeycomb structure so that the cell end portions can be plugged lest the inside of the cell should communicate with the outside.

[Summary of the Invention]

In order to solve the aforementioned problems, the present inventors earnestly studied the step where the plugging material is filled into cell end portions of the honeycomb structure, which led to the completion of the present invention. That is, according to the present invention, the following method for manufacturing a plugged honeycomb structure is provided.
A method for manufacturing a plugged honeycomb structure having porous partition walls separating and forming a plurality of cells extending through from one end face to the other end face of the honeycomb structure, the method comprising: a masking step of providing a mask having injection holes formed so that 10 to 60% of an area of an opening portion of each of cells to be plugged on the one end face and/or the other end face is open with an injection hole gravity center as the gravity center of the injection hole being shifted from a cell opening gravity center as the gravity center of the opening portion of each of the cells, and after the masking step, a plugging material-filling step of supplying a plugging material having flowability into the cells to be plugged from the injection hole with causing repulsion pressure as pressure from the inner portions of the cells toward the opening portions.
The method for manufacturing a plugged honeycomb structure according to [1], wherein the mask having the injection holes formed lest each of the injection holes should contain the cell opening gravity center inside thereof is provided in the masking step.
The method for manufacturing a plugged honeycomb structure according to [1] or [2], wherein the mask having the injection holes formed so that 20 to 50% of the area of the opening portion of each of the cells is open is provided in the masking step.
The method for manufacturing a plugged honeycomb structure according to any one of [1] to [3], wherein the mask having the injection holes formed so that the rate of the length in the horizontal axial direction with respect to the length in the vertical direction of each of the injection holes is 2.0 to 4.0 is provided in the masking step.
The method for manufacturing a plugged honeycomb structure according to any one of [1] to [4], wherein the plugging material-filling step is performed with holding a honeycomb structure so that the injection hole gravity center is located above the cell opening gravity center in a direction perpendicular to the cell extension direction so that the plugging material supplied to the inside of the cell received the action of the gravity in addition to the repulsion pressure.
The method for manufacturing a plugged honeycomb structure according to any one of [1] to [5], whereinthepluggingmaterial-fillingstepisperformed with holding a honeycomb structure so that the cell extension direction from one end face to the other end face is horizontal.
The method for manufacturing a plugged honeycomb structure according to any one of [1] to [6], wherein, after supplying the plugging material into the cells, the plugging material present outside the cells across the mask is moved perpendicularly to the extension direction to separate the plugging material present outside the cells from the plugging material inside the cells in the plugging material-filling step.
The method for manufacturing a plugged honeycomb structure according to any one of [1] to [7], wherein the plugging material has a viscosity of 100 to 700 dPa·s.
A method for manufacturing a plugged honeycomb structure of the present invention can fill the plugging material into cell end portions of a honeycomb structure so that the end portions can be plugged without connecting the inside of the cells with the outside.

Brief Description of the Drawings

[Fig. 1] Fig. 1 is a perspective view of a honeycomb structure.
[Fig. 2] Fig. 2 is a partial cross-sectional view of a honeycomb structure in the A-A' cross section in Fig. 1.
[Fig. 3] Fig. 3 is a perspective view of a plugged honeycomb structure.
[Fig. 4] Fig. 4 is a view showing an embodiment of a method for manufacturing a plugged honeycomb structure of the present invention for explaining how a plugging material is supplied to the inside of the cell from the injection hole.
[Fig. 5] Fig. 5 is a view showing an embodiment of a method for manufacturing a plugged honeycomb structure of the present invention in a step following Fig. 4 for explaining the state of the plugging material filled and maintained in the cell end portion.
[Fig. 6] Fig. 6 is a plan view of a cell opening portion provided with a mask having an injection hole which does not include the cell opening gravity center.
[Fig. 7] Fig. 7 is a plan view of a cell opening portion provided with a mask having an injection hole which includes the cell opening gravity center in such a manner that the injection hole gravity center is shifted from the cell opening gravity center.
[Fig. 8] Fig. 8 is a view showing a state of providing a mask having no injection hole on both the end faces of the honeycomb structure for explaining an embodiment of a method for manufacturing a plugged honeycomb structure of the present invention.
[Fig. 9] Fig. 9 is a view showing the state of formation of injection holes in the masks provided on both the end faces of the honeycomb structure in the step following Fig. 8.
[Fig. 10] Fig. 10 is a view showing the step following Fig. 9 for explaining a state of supplying a plugging material to the inside of the cells by immersing both the end faces of a honeycomb structure held so that the extension direction becomes horizontal in the plugging material contained in storage containers.
[Fig. 11] Fig. 11 is a view showing the step following Fig. 10 for explaining a state of dividing a part of a side wall, and sliding the tip portion of the dividable side wall to move downward, thereby separating the plugging material outside the cells from the plugging material filled into the cell end portions.

[Reference Numerals]

1: honeycomb structure, 2: partition wall, 3: cell, 4: end face, 5: opening portion, 6: cell center, 7: cell end portion, 8: outer peripheral wall, 9: cell opening gravity center, 10: extension direction, 11: mask, 12: injection hole, 13: injection hole gravity center, 14: inside face, 21: length in the horizontal axial direction, 22: length in the vertical axial direction, 31: plugging material, 31a: pluggingmaterial, 31b: pluggingmaterial, 41: storage container, 42: inside bottom portion, 43: side wall, 48: complementary side wall, 49: tip portion, 50: dividable side wall, 51: vertical direction, 52: upward direction, 53: downward direction, 55: cell central direction, 56: cell end portion direction, 60: horizontal direction, 61: plugged honeycomb structure, 62: end face on one side, 63: end face on the other side, 64: plugging

[Mode for Carrying Out the Invention]

Hereinbelow, an embodiment of the present invention will be described with referring to drawings. The present invention is by no means limited to the following embodiments.
A method for manufacturing a plugged honeycomb structure of the present invention (hereinbelow, referred to as a "manufacturing method of the present invention") is characterized by a method for filling a plugging material into cell end portions of a honeycomb structure. In the first place, a honeycomb structure, names of each portion of the honeycomb structure, and the like will be described prior to the description of a manufacturing method of the present invention.
1. Honeycomb structure:

Fig. 1 shows an example of a honeycomb structure 1 as a perspective view. Fig. 2 is a cross-sectional view of a honeycomb structure 1 in the A-A' cross-section shown in Fig. 1. The honeycomb structure 1 has porous partition walls 2 by which a plurality of cells 3 extending from an end face 62 on one side to the other end face 63 on the other side are partitioned and formed.

The manufacture of a ceramic honeycomb structure used for a DPF or the like goes through the steps of forming kneaded clay of a ceramic powder into a honeycomb shape to obtain a formed article and then firing the formed article to obtain a fired article. Both the aforementioned formed article and the fired article fall into honeycomb structures of the present specification.
In the case of a honeycomb structure 1 having ceramic as a main component, the material is not particularly limited. From the viewpoints of strength, thermal resistance, corrosion resistance, and the like, the material is preferably one of silicon carbide, silicon-silicon carbide based composite material, silicon nitride, alumina, mullite, cordierite, aluminum titanate, silicon carbide-cordierite based composite material, lithium aluminum silicate, and aluminum titanate. Of these, silicon carbide or silicon-silicon carbide based composite material is more preferable.
With referring to Fig. 2, the portions where the cells are open in the end face 4 of the honeycomb structure 1, that is, the ends of the cells 3 are called opening portions 5. In addition, the direction where the cells 3 are extending over in the honeycomb structure 1 is called an extension direction 10. The extension direction 10 is sometimes used for convenience sake when the orientation of the honeycomb structure 1 is described.
When the plugging material is filled into cell end portions 7 of the honeycomb structure 1 shown in Fig. 1 according to a manufacturing method of the present invention, a plugged honeycomb structure 61 where pluggings 64 are disposed as shown in the perspective view of Fig. 3 can be obtained. In Fig. 3, the honeycomb structure is shown so that the pluggings 64 show a checkerwise pattern when the end face 4 of the honeycomb structure 1 is viewed from the front. A manufacturing method of the present invention is not limited to the method where the pluggings 64 are disposed in such a checkerwise pattern and can be applied to the disposition of the pluggings 64 of any distribution pattern as long as the pluggings 64 are disposed in cell end portions 7.
2. Basic embodiment of a method for manufacturing a plugged honeycomb structure of the present invention:

In the description here, simplified schematic view is used for convenience sake with extracting one cell 3 and partition walls 2 partitioning and forming the cell 3. Figs. 4 and 5 each shows a cross-sectional view along the extension direction 10 of the cell 3 and the partition walls 2 partitioning and forming the cell 3. By one embodiment of a manufacturing method of the present invention, how the plugging material 31 is supplied to the cell end portion 7 is shown.

A manufacturing method of the present invention is a method where a mask 11 having injection holes 12 is provided on the open portions 5 of cells 3 to supply the plugging material 31 having flowability into the cells 3 from the injection holes 12, thereby filling the plugging material 31 into the cell end portions 7. In addition, the manufacturing method of the present invention has a masking step and a plugging material-filling step described below.
2-1. Masking step:

A masking step in a manufacturing method of the present invention is a step provided with a mask 11 having injection holes 12 on the opening portions 5 of the cells 3.

Figs. 6 and 7 each shows an opening portion 5 of a cell 3 provided with the mask 11 having the injection hole 12 in the masking step. Incidentally, these figures show views of the end face 4 of the honeycomb structure 1 viewed from the extension direction 10.
In the mask 11 provided on the opening portions 5 in the masking step, the injection hole gravity center 13 is shifted with respect to the cell opening gravity center 9.
Incidentally, Fig. 6 shows a form where the cell opening gravity center 9 is present outside the injection hole 12, and Fig. 7 shows a form where the cell opening gravity center 9 is included in the injection hole 12.
2-1-1. Injection hole:

The injection hole 12 means a hole present in the mask 11 provided on the opening portion 5 of the cell 3 and is formed so that the plugging material 31 can be supplied to the inside of the cell 3 from the outside of the cell 3.

The area of the injection hole 12 corresponds to 10 to 60% of the area of the opening portion 5 of one cell 3. That is, in the opening portion 5, the plugging material 31 is supplied to the inside of the cell 3 from the portion of 10 to 60% of the area of the opening portion 5, and the remaining 40 to 90% portion of the area of the opening portion 5 is shut.
2-1-1-1. Definitions of the injection hole gravity center and the cell opening gravity center and positional relation of these centers:

With referring to Fig. 4, in the case of providing a flat film-shaped mask 11 on the honeycomb structure 1 having a flat end face 4 perpendicular to the extension direction 10, the injection hole gravity center 13 is determined as the gravity center of the plane figure of the injection hole 12, and the cell opening gravity center 9 is determined as the gravity center of the plane figure of the opening portion 5. In addition, in this case, since the opening portion 5 and the injection hole 12 are present in the same plane, the gap between the injection hole gravity center 13 and the cell opening gravity center 9 can be recognized as it is.

There can be considered a case that the honeycomb structure 1 has an inclination structure where a part of the end face 4 is deviated from the plane perpendicular to the extension direction 10 and a case where the mask 11 is not flat but curved. In the case of such an irregular formation, in consideration of pressure basically applied along the extension direction 10 to the plugging material 31 filled into the cell end portion 7, the injection hole gravity center 13 and the cell opening gravity center 9 and the positional relation of the injection hole gravity center 13 and the cell opening gravity center 9 are determined as follows .
In the case of the aforementioned irregular formation, the injection hole gravity center 13 is determined as the gravity center of the plane figure obtained by projecting the injection hole 12 in the extension direction 10 to the projection plane, which is a plane perpendicular to the extension direction 10.
Further, in the case of the aforementioned irregular formation, the cell opening gravity center 9 is determined as the gravity center of the plane figure obtained by projecting the opening portion 5 in the extension direction 10 to the same projection plane as in the determination of the injection hole gravity center 13.
Therefore, in the case that the mask 11 or the opening portion 5 is in an irregular formation, there can be recognized the gap between the injection hole gravity center 13 and the cell opening gravity center 9 both determined on the same projection plane by the aforementioned method.
2-1-2. Method of disposing the mask:

The method of disposing the mask 11 is not limited as long as the mask 11 having the injection holes 12 having the aforementioned formation can be provided on the opening portions 5.

Figs. 8 and 9 show an embodiment where, after the opening portion 5 is covered with the mask 11 with no hole, the injection hole 12 is formed. Specifically, Fig. 8 shows a vertical cross-section along the extension direction 10 of the honeycomb structure 1, where both the entire end faces 4 of the honeycomb structure 1 are covered with the masks 11 with no hole to shut the opening portions 5 of the cells. Fig. 9 shows the state where the injection holes 12 are formed in the masks 11 covering the predetermined opening portions 5 after the masks 11 with no hole are provided on both the end faces 4 as shown in Fig. 8.
Alternatively, though it is not illustrated, the masks 11 where the holes functioning as the injection holes 12 are formed in advance are prepared and provided on the opening portions 5 so as to have the characteristics of the present invention.
2-2. Plugging material-filling step:

With referring to Fig. 4, the plugging material-filling step in a manufacturing method of the present invention is a step of filling the plugging material 31 into cell end portions 7 by supplying the plugging material 31 having flowability to the inside of cells 3 from the injection holes 12.

2-2-1. Plugging material:

The plugging material 31 used in the plugging step is not particularly limited as long as it has flowability and can plug cell end portions 7. A specific plugging material 31 is slurry prepared by mixing a ceramic powder with a dispersion medium such as water for dispersing the ceramic powder as in the plugging of a conventional plugged honeycomb structure.

Incidentally, when a honeycomb structure 1 containing ceramic as a main component is plugged, as the plugging material 31, it is preferable to use ceramic slurry of the same raw material as that of the honeycomb structure. In this case, when the plugging material 31 is filled into cell end portions 7 and fired, the thermal expansion coefficient is the same between the honeycomb structure 1 and the plugging material 31, and therefore a plugged honeycomb structure 61 having high durability can be obtained.
2-2-2. State of causing repulsion pressure:

In the plugging material-filling step, the repulsion pressure from the inside of the cell 3 toward the opening portion 5 as shown by the outlined arrow in Fig. 4 is applied when the plugging material 31 is supplied from the injection hole 12.

In order to apply the repulsion pressure, there is a method where, for example, the opening portion 5 opposite to the side where the plugging portion 31 is supplied is shut with a mask 20 or the like as shown in Fig. 4 to use a repulsion force of the gas inside the cell 3 contracted by the supply of the plugging material 31 into the cell 3.
Alternatively, though it is not illustrated, the repulsion pressure applied on the plugging material 31 supplied to the inside of the cell 3 may be generated by sending gas such as air or liquid from the open portion 5 opposite to the side where the plugging material 31 is supplied.
2-2-3. Method for supplying the plugging material to the inside of cell:

The method for supplying the plugging material 31 to the inside of the cell 3 from the injection hole 12 is not particularly limited as long as the plugging material 31 can be supplied to the inside of the cell 3 against the repulsion pressure generating inside the cell 3.

The method for supplying the plugging material 31 to the inside of the cell 3 from the injection hole 12 may be any of the method where the plugging material 31 is continuously supplied to the inside of the cell 3 and the method where the plugging material 31 is intermittently supplied to the inside of the cell 3.
For example, as shown in Patent Document 4, there may be employed a method where the plugging material 31 contained in a plate-shaped storage container is pressed against the end face 4 of the honeycomb structure 1 to inject the plugging material 31 into the inside of the cell 3 under pressure.
Alternatively, as a method disclosed in JP-A-2009-40046 by the present applicant, the plugging material 31 may be supplied to the inside of the cell 3 by the use of a plugging apparatus having a pressurizing member helping the plugging material 31 to be supplied to the inside of the cell 3.
2-3. Function of manufacturing method of the present invention in basic embodiment:

Fig. 5 shows a state after the plugging material 31 is supplied to the cell end portion 7 in the step shown in Fig. 4. As is understandable from the transition from Fig. 4 to Fig. 5, when the plugging material 31 is supplied to the cell end portion 7 according to a manufacturing method of the present invention, there is caused a condition where the repulsion pressure to the plugging material 31 opposes the propulsive force of the plugging material 31 from the opening portion 5 side toward the cell center 6. In addition, due to the flowability of the plugging material 31, the plugging material 31 spreads over the entire cell end portion 7 by being pushed in the direction perpendicular to the extension direction 10 to be filled so that the inside of the cell 3 is separated from the outside.

In addition, as is understandable from Fig. 5, in a manufacturing method of the present invention, once the plugging material 31 has been supplied to the cell end portion 7, the plugging material 31 is not ejected to the outside of the cell 3 even under the repulsion pressure because of the support of the inside face 14 of the mask 11.
Since the solidification of the plugging material 31 proceeds from the portions in the vicinity of the partition walls 2 toward the central portion because the porous partition walls 2 absorb moisture of the plugging material 31, the solidification of the plugging material 31 in the cell opening gravity center 9 is slowest.
In addition, it is difficult to inhibit ejection and deformation of the plugging material 31 in the vicinity of the injection hole gravity center 13 even though the fact that the plugging material 31 has viscosity is taken into consideration.
In a manufacturing method of the present invention, since the injection hole gravity center 13 is shifted from the cell opening gravity center 9, once the plugging material 31 has been filled into the cell end portion 7, the plugging material 31 receives the action of the mask 11 suppressing the ejection and deformation of the plugging material 31 and easily be held as it is without deformation until it is solidified.
It is also possible to employ an embodiment provided with the masking step or the plugging material-filling step described below with having the constitution of the aforementioned basic embodiment of a manufacturing method of the present invention.
3. Masking step:

3-1. Embodiment provided with mask having the injection hole excluding the cell opening gravity center:
- In the masking step, it is preferable to provide the mask 11 having the injection hole 12 formed so as not to include the cell opening gravity center 9 therein as shown in Fig. 6.

Incidentally, this embodimentmeansthat the cell opening gravity center 9 is not included in the figure projected from the injection hole 12 to the projection plane when the cell opening gravity center 9 and the injection hole gravity center 13 are determined by the aforementioned irregular method, that is, when the injection hole gravity center 13 and the cell opening gravity center 9 are determined on the projection plane.
In the embodiment where the injection hole 12 does not include the cell opening gravity center 9, since the plugging material 31 in the vicinity of the cell opening gravity center 9, where the solidification of the plugging material 31 is slower, is covered by the inside face 14 of the mask 11, ejection of the plugging material 31 to the outside of the cell 3 is further inhibited. In addition, in this embodiment, it is securely prevented that the plugging material 31 is depressed in the vicinity of the cell opening gravity center 9 and moves toward the inside before the plugging material 31 is completely solidified, and no void is generated in the plugging material 31 filled into the cell end portion 7.
3-2. Embodiment provided with the injection hole where 20 to 50% of the opening portion area is open:

In the masking step, it is preferable to provide the mask 11 having the injection hole 12 formed so that 20 to 50% of the area of the opening portion 5 of the cell 3 is open. From such an injection hole 12, the plugging material 31 can easily be supplied to the inside of the cell 3, and the plugging material 31 once filled in the cell end portion 7 is hardly ejected to the outside of the cell 3.

3-3. Embodiment provided with the injection hole formed so that the rate of the length in the horizontal axial direction with respect to the length in the vertical direction of each of the injection holes is 2.0 to 4.0:

With referring to Fig. 6, in the masking step, it is preferable to provide the mask 11 having the injection holes 12 formed so that the rate of the length 21 in the horizontal axial direction with respect to the length 22 in the vertical direction of each of the injection holes is 2.0 to 4.0. From the injection hole 12 having such a form, the plugging material 31 can easily be supplied to the inside of the cell 3, and the plugging material 31 once filled in the cell end portion 7 is hardly ejected to the outside of the cell 3.

4. Plugging material-filling step:

4-1. Embodiment where the honeycomb structure is held in a state that the injection hole gravity center is located above the cell opening gravity center:
- In the plugging material-filling step, as shown in Fig. 4, it is preferable that the honeycomb structure 1 is held in a state that the injection hole gravity center 13 is located above the cell opening gravity center 9. In this embodiment, the plugging material 31 supplied to the inside of the cell 3 received the action of the gravity in addition to the repulsion pressure. Therefore, in this embodiment, the plugging material 31 easily spreads over the entire cell end portion 7.

4-2. Embodiment where the honeycomb structure is held so that the cell extension direction is horizontal:

In the plugging material-filling step, as shown in Fig. 4, it is preferable that the honeycomb structure 1 is held so that the extension direction 10 of the cells 3 is horizontal. In such a formation, as shown in Fig. 10, the plugging material 31 can easily be filled simultaneously with respect to both the end faces 4 of the honeycomb structure 1, and the supply conditions of the plugging material 31 at both the end faces 4 can be made the same.

4-3. Embodiment where, after supplying the plugging material into the cells, the plugging material present outside the cells across the mask is moved perpendicularly to the extension direction:

In the plugging material-filling step, it is preferable that, after supplying the plugging material 31 into the cells 3, the plugging material 31a present outside the cells 3 across the mask 11 is moved perpendicularly to the extension direction 10 to separate the plugging material 31a present outside the cells 3 from the plugging material 31b inside the cells 3. A specific example of this embodiment will be described below with referring to Figs. 10 and 11.

Fig. 10 is a vertical cross-sectional view along the extension direction 10 of the honeycomb structure 1 provided with the mask 11 and the plate-shaped storage container 41 containing the plugging material 31. The figure shows how the plugging material 31 is continuously injected into the cells 3 under pressure with the plugging material 31 contained in the plate-shaped storage containers 41 being pressed against the end faces 4 of the honeycomb structure 1.
The storage container 41 shown in Fig. 10 is constituted from two parts so that a part of the side wall 43 is separated from the other part. Specifically, in a portion where the side wall 43 is partially separated, a complementary side wall 48 is provided on the outside of the dividable side wall 50 on the side where the plugging material 31 is contained. In addition, in the side wall 43 having a complementary side wall 48 attached thereto, the position of the tip portion 49 of the dividable side wall 50 is in the middle portion of the side wall 43 having a complementary side wall 48 attached thereto.
Incidentally, the position of the tip portion 49 of the dividable side wall 50 is preferably on the inside bottom portion 42 side with respect to the fluid level of the plugging material 31 when the end faces 4 of the honeycomb structure 1 are pressed against the plugging material 31 contained in the storage container 41. This enables to separate the dividable side wall 50 from the complementary side wall 48 with keeping the end faces 4 of the honeycomb structure 1 in the state of being pressed against the plugging material 31.
Fig. 11 shows separation of the dividable side wall 50 from the complementary side wall 48 after the injection the plugging material 31 into the cell 3 by a method shown in Fig. 10. Since the tip portion 49 of the dividable side wall 50 locates in the aforementioned position, the dividable side wall 50 separated from the tip portion 48 can be moved perpendicularly to the extension direction 10 so as to traverse the end face 4 without getting stuck with the outer peripheral wall of the honeycomb structure 1.
At this time, it is preferable to move the tip portion 49 of the dividable side wall 50 so as to glide over the end face 4 of the honeycomb structure 1 (see Fig. 11). By the tip portion 49 of the dividable side wall 50, the plugging material 31 outside the cell 3 can compulsorily be separated from the plugging material 31 inside the cell 3, and superfluous plugging material 31 remaining on the end face 4 can be scraped off.
At this time, one of the storage container 41 where the complementary side wall 48 is separated and the honeycomb structure 1 may be moved, or both of them may be moved.
Further, it is more preferable that the plugging material 31a outside the cell 3 is moved along the direction from the injection hole gravity center 13 toward the cell opening gravity center 9. By the relative movement of the plugging material 31a, the brim of the injection hole 12 easily functions as a blade, and the plugging material 31a present outside the cells 3 across the mask 11 can smoothly be separated from the plugging material 31a present inside the cells 3.
4-4. Embodiment of filling the plugging material 31 simultaneously from both the end faces of the honeycomb structure:

In the plugging material-filling step, it is preferable to simultaneously supply the plugging material 31 from the injection holes 12 in the end face 62 on one side and the other end face 63 on the other side. This improves productivity.

When the plugging material 31 is ceramic slurry, it is possible to fire the honeycomb structure 1 having the plugging material 31 filled into cell end portions 7 after the plugging material-filling step.
The plugging material 31 has a viscosity of 100 to 700 dPa·s, more preferably 200 to 600 dPa·s from the viewpoints of inhibiting the incomplete plugging such as formation of a void in the plugging material 31 filled into the cell end portion 7 and reducing the variance in the plugging depth. When the viscosity of the plugging material 31 is 100 dPa·s or more, it securely inhibits the plugging material 31 from being filled deeply beyond necessity and from being ejected to the outside of the cell 3. In addition, when the viscosity of the plugging material 31 is 700 dPa·s or less, the plugging material 31 can securely be filled up to the desired depth from the end face 4. Incidentally, the viscosity of the plugging material 31 described here is measured according to JIS K 7117-1 by the use of a single cylinder type rotary viscometer.

[Example]

Hereinbelow, the present invention will be described in more detail on the basis of Examples. However, the present invention is by no means limited to these Examples.

(Examples 1 to 17 and Comparative Example 1 to 6)

(1) Honeycomb structure:
- A raw material powder containing a silicon carbide powder as a main component was kneaded to obtain kneaded clay, which was then subjected to extrusion forming to manufacture a honeycomb-shaped formed article. After the formed article was dried, both the end faces of the formed article were cut off to have flat and smooth faces, and thereby a honeycomb structure 1 for filling the plugging material 31 was obtained. The honeycomb structure 1 is constituted of cells 3 having a large-sized cell diameter and cells 3 having a small-sized cell. Specifically, the cells 3 having a large-sized cell were formed to have an octagonal shape having a distance of 1.99 mm between facing sides, and the cells 3 having a small-sized cell were formed to have a square shape having a side of 1.27 mm with the cells 3 having a large-sized cell and cells 3 having a small-sized cell being alternately disposed. In addition, the honeycomb structure 1 manufactured here is a segment having external dimensions of 36.9 mm x 36. 9 mm x 127 mm with a partition wall thickness of 0.38 mm and a cell density of 160 cells/inch² (25 cells/cm²).
(2) Masking step:
- An adhesive film serving as the mask 11 was stuck entirely on each of the end faces 4 of the above honeycomb structure 1. In the sticking of the adhesive film, an adhesive was applied on a surface on one side of a polyester film, and the film surface where the adhesive was applied was attached to each of the end faces 4 of the honeycomb structure 1 (see Fig. 8).

Then, the positions of the cells 3 were calculated by image processing according to a method generally employed in a method for manufacturing a plugged honeycomb structure. Further, the coordinate values corresponding to the positions of the opening portions 5 of the cells 3 to be plugged and the coordinate values of the inside portions and the profiles of the injection holes 12 were calculated. On the basis of these coordinate values, only the positions for forming the injection holes 12 were irradiated with a laser to form the injection holes 12.
In the end face 62 on one side of the honeycomb structure 1, the injection holes 12 were formed only in the portions covering the opening portions 5 of the cells 3 having a large cell diameter of the adhesive film, while, in the end face 63 on the other side of the honeycomb structure 1, the injection holes 12 were formed only in the portions covering the opening portions 5 of the cells 3 having a small cell diameter of the adhesive film. Incidentally, the injection holes 12 were formed to have an elliptic or a quadrangular shape. Regarding an elliptic injection hole 12, please see Figs. 6 and 7.

Regarding Examples 1 to 17 and Comparative Examples 1 to 6, the shape of the injection holes 12 of the mask 11 provided with the opening portions 5 of the cells 3 having a large cell diameter in the end face 62 on one side is shown in Table 1. Incidentally, in the "inclusion of gravity center" in Table 1, the case that the cell opening gravity center 9 was located inside the injection hole 12 is expressed as "present" of the inclusion of gravity center. The "opening area rate" is shown by the percentage (%) of the area of the injection hole 12 with respect to the area of the opening portion 5 of the cell 3.

Table 1

	Gravity center shift*¹ (mm)	Inclusion of gravity center*²	Injection hole shape	Length of injection hole in horizontal axial direction (L) (mm)	Length of injection hole in vertical axial direction (M) (mm)	L/M	Opening area rate (%)	Separation direction	Viscosity of plugging material (dPa·s)
Example 1	0.5	None	Quadrangle	1.8	0.8	2.3	40	Vertical	400
Example 2	0.5	None	Ellipse	1.8	0.8	2.3	30	Vertical	400
Example 3	0.5	None	Ellipse	1.8	0.6	3	20	Vertical	400
Example 4	0.5	None	Ellipse	1.8	0.45	4	20	Vertical	400
Example 5	0.5	None	Ellipse	1.2	0.6	2	10	Vertical	400
Example 6	0.5	None	Ellipse	0.9	0.6	1.5	10	Vertical	400
Example 7	0.5	None	Circle	0.9	0.9	1	20	Vertical	400
Example 8	0.5	None	Quadrangle	1.8	0.36	5	20	Vertical	400
Example 9	0.5	None	Quadrangle	1.8	0.3	6	10	Vertical	400
Example 10	0.5	None	Ellipse	1.8	0.8	2.3	30	Horizontal	400
Example 11	0.3	Present	Ellipse	1.8	0.8	2.3	30	Vertical	400
Example 12	0.5	None	Quadrangle	1.9	0.95	2	50	Vertical	400
Example 13	0.4	Present	Quadrangle	1.9	1.15	1.7	60	Vertical	400
Example 14	0.5	None	Quadrangle	1.8	0.8	2.3	40	Vertical	100
Example 15	0.5	None	Quadrangle	1.8	0.8	2.3	40	Vertical	200
Example 16	0.5	None	Quadrangle	1.8	0.8	2.3	40	Vertical	600
Example 17	0.5	None	Quadrangle	1.8	0.8	2.3	40	Vertical	700
Comp. Ex. 1	0	Present	Circle	1.6	1.6	1	50	Vertical	400
Comp. Ex. 2	0	Present	Ellipse	1.8	0.8	2.3	30	Vertical	400
Comp. Ex. 3	0	Present	Ellipse	1.8	0.8	2.3	30	Horizontal	400
Comp. Ex. 4	0	Present	Quadrangle	1.2	1.2	1	40	Vertical	400
Comp. Ex. 5	0.5	None	Quadrangle	1.8	0.8	2.3	40	Vertical	50
Comp. Ex. 6	0.5	None	Quadrangle	1.8	0.8	2.3	40	Vertical	800

*1: Shift between injection hole gravity center and cell opening gravity center.
*2: Whether the cell opening gravity center is included in the injection hole or not.

(3) Plugging material-filling step:

As the plugging material 31, ceramic slurry having the same components as those of the honeycomb structure 1 was employed, and the viscosity was adjusted to 50 to 800 dPa·s by adjusting the kind and amount of the binder to be added to the slurry (Table 1). Incidentally, the viscosity was measured according to JIS K 7117-1 by the use of a single cylinder type rotary viscometer.
For the supply of the plugging material 31, there was used a plate-shaped storage container 41 where a part of the side wall 43 is separated from the other part as shown in Figs. 10 and 11. As shown in Fig. 10, the honeycomb structure 1 was held so that the extension direction 10 was horizontal. After the fluid surface of the plugging material 31 contained in the storage container 41 was set to be almost perpendicular to the extension direction 10, the plugging material 31 was pressed against the end face 4 of the honeycomb structure 1 under a pressure of 0.2 MPa so that the distance between the inside bottom portion 42 of the storage container 41, and the end faces 4 of the honeycomb structure 1 were immersed in the plugging material 31. Incidentally, the time (time for injection under pressure) for immersion of the end faces 4 of the honeycomb structure 1 in the plugging material 31 was one second. The total amount of slurry filled into all the large cells (having a diameter of 1.99 mm) in the end face 62 on one side was 11g.
After the plugging material 31 was supplied, in Examples 1 to 9, 11 to 17, Comparative Example 1, 2, and 4 to 6, the plugging material 31a outside the cells and the plugging material 31b inside the cells 3 were separated from each other by separating the dividable side wall 50 from the complementary side wall 48 and sliding the tip portion 49 of the dividable side wall 50 downward on each of the end faces 4 of the honeycomb structure 1, that is, by moving the tip portion 49 perpendicularly to the extension direction 10 as shown in Fig. 11 ("vertical" in Table 1).
In Example 10 and Comparative Example 3, by horizontally moving the storage containers 41 to separate the storage containers 41 from the honeycomb structure 1, the plugging material 31a outside the cells 3 and the plugging material 31b inside the cells 3 were separated from each other ("horizontal" in Table 1, not illustrated).
After the plugging material 31 was filled into cell end portions 7 of the honeycomb structure 1 as described above and dried for solidification, the evaluation described below was performed.

(4) Evaluation:

The plugging material 31 filled into the cell end portions 7 of the cells 3 having a large diameter was evaluated for three items of presence/absence of imperfect plugging, average plugging depth, and plugging depth variance, and the results are shown in Table 2. The presence/absence of imperfect plugging was judged by checking the outflow of the plugging material 31 right after being filled into the cell end portion 7 from the cell end portion 7 to the end face of the honeycomb structure 1 or the presence/absence of a hole connecting the inside of the cell 3 with the outside of the cell 3 in the plugging material 31 filled into the cell end portion 7 due to the filling of an insufficient amount of the plugging material 31. The average plugging depth was calculated by arbitrarily selecting seven large-sized cells from the end face 4 of one honeycomb structure 1 to obtain the average depth of the plugging material 31 filled into the seven large-sized cells. The plugging depth was calculated by inserting a metal stick into the cells from the cell end portions 7 opposite to the side where the plugging material 31 was filled toward the cell end portions 7 where the plugging material 31 was filled and deducting the length of the inserted part of the metal stick from the entire length in the extension direction 10 of the cells 3. The plugging depth variance was obtained by calculating the standard deviation σ with respect to the aforementioned average plugging depth.

Table 2

	Imperfect plugging	Average plugging depth (mm)	Plugging depth variance σ (mm)
Example 1	None	6.0	0.7
Example 2	None	5.8	0.7
Example 3	None	5.6	0.8
Example 4	None	5.3	0.9
Example 5	None	4.8	1.1
Example 6	None	4.5	1.3
Example 7	None	5.0	1.2
Example 8	None	5.1	1.1
Example 9	None	4.7	1.3
Example 10	None	5.2	1.0
Example 11	None	5.3	1.0
Example 12	None	5.0	1.0
Example 13	None	5.7	1.1
Example 14	None	6.7	1.1
Example 15	None	6.3	0.9
Example 16	None	5.4	1.0
Example 17	None	4.9	1.2
Comp. Ex. 1	Present	5.1	1.5
Comp. Ex. 2	Present	4.6	1.2
Comp. Ex. 3	Present	3.9	1.3
Comp. Ex. 4	Present	4.8	1.3
Comp. Ex. 5	Present	6.5	1.5
Comp. Ex. 6	Present	4.2	1.3

All of Examples 1 to 17 had no imperfect plugging. On the other hand, all of Comparative Examples 1 to 6 had imperfect plugging. Therefore, in Example 1 to 17, which belong to the technical scope of a manufacturing method of the present invention, the plugging material 31 can be filled into the cell end portion 7 of a honeycomb structure 1 so that the cell end portion could be plugged without allowing the inside of the cell 3 to communicate with the outside.
From the evaluation results of Examples 1 to 4, 10 to 12, 15, and 16, by limiting the opening area rate of the injection whole 12 to 20 to 50% and the rate of the length in the horizontal direction to the vertical direction to 2.0 to 4.0, the plugging depth variance could be suppressed (1.0 mm or less) to improve the quality. When the rate is out of the range of 2.0 to 4.0, even though the imperfect plugging could be inhibited, the plugging material 31 hardly enters the inside of the cell 3, thereby increasing the plugging depth variance (Tables 1 and 2).
In addition, in Examples 2 and 10 and Comparative Examples 2 and 3, the directions for separating the plugging material 31a outside the cells 3 from the plugging material 31b inside the cells 3 were compared. Example 2 and Comparative Example 2 had larger plugging depth and smaller plugging depth variance than those of the Example 10 and Comparative Example 3, which were for comparison with Example 2 and Comparative Example 2 (Tables 1 and 2). Therefore, the embodiments where the direction for separating the plugging the plugging material 31a outside the cells 3 from the plugging material 31b inside the cells 3 is perpendicular to the extension direction 10 had more appropriate depth of plugging material 31 filled in the cells 3 than that of embodiments where the separation direction is parallel to the extension direction 10 and hardly had imperfect plugging and plugging depth variance.
In addition, in Examples 2 and 11, the injection hole 12 includes the cell opening gravity center 9 and the case that the injection hole 12 does not include the cell opening gravity center 9 were compared. Example 2 had larger plugging depth and small plugging depth variance than those of Example 11 (Tables 1 and 2). Therefore, the embodiment where the injection hole 12 did not include the cell opening gravity center 9 had more appropriate depth of plugging material 31 filled in the cells 3 than that of embodiments where the injection hole 12 included the cell opening gravity center 9 and hardly had imperfect plugging and plugging depth variance.
In addition, the Examples 14 to 17 and Comparative Examples 5 and 6 differed in only the viscosity of the plugging material 31. Examples 15 and 16, where the viscosity of the plugging material 31 was 200 to 600 dPa·s, had smaller plugging depth variance than that of Example 14, where the viscosity was 100 dPa·s, and that of Example 17, where the viscosity was 700 dPa·s (Tables 1 and 2). In addition, Comparative Example 5, where the viscosity was lower than 100 dPa· s, the plugging material 31 was ejected to the outside of a cell 3 after plugging to cause imperfect plugging. Example 6, where the viscosity was higher than 700 dPa· s, imperfect plugging was caused due to insufficient filling of the plugging material 31. Therefore, when the viscosity of the plugging material 31 is 100 to 700 dPa·s, the end portions of the cells 3 could be plugged without the inside of the cells communicating with the outside, and, when the viscosity of the plugging material is 200 to 600 dPa·s, a plugged honeycomb structure having high quality could be manufactured.

[Industrial Applicability]

The present invention can be used as a method for manufacturing a plugged honeycomb structure which can be used as a filter such as a diesel particulate filter and where predetermined cells are plugged in the end faces.

Claims

A method for manufacturing a plugged honeycomb structure (61) having porous partition walls (2) separating and forming a plurality of cells (3) extending through from one end face (62) to the other end face (63) of the honeycomb structure (61), the method comprising:
a masking step of providing a mask (11) having injection holes (12) formed so that 10 to 60% of an area of an opening portion (5) of each of cells (3) to be plugged on the one end face (4) and/or the other end face (4) is open with an injection hole gravity center (13) as the gravity center of the injection hole, and

after the masking step, a plugging material-filling step of supplying a plugging material (31) having flowability into the cells (3) to be plugged from the injection hole (12) with causing repulsion pressure as pressure from the inner portions of the cells (3) toward the opening portions (5), characterized in that in the masking step the injection hole gravity center (13) is shifted from a cell opening gravity center (9) as the gravity center of the opening portion of each of the cells.
The method for manufacturing a plugged honeycomb structure (61) according to Claim 1, wherein the mask (11) having the injection holes (12) formed lest each of the injection holes (12) should contain the cell opening gravity center (9) inside thereof is provided in the masking step.
The method for manufacturing a plugged honeycomb structure (61) according to Claim 1 or 2, wherein the mask (11) having the injection holes (12) formed so that 20 to 50% of the area of the opening portion (5) of each of the cells (3) is open is provided in the masking step.
The method for manufacturing a plugged honeycomb structure (61) according to any one of Claims 1 to 3, wherein the mask (11) having the injection holes (12) formed so that the rate of the length in the horizontal axial direction (21) with respect to the length in the vertical direction (22) of each of the injection holes (12) is 2.0 to 4.0 is provided in the masking step.
The method for manufacturing a plugged honeycomb structure (61) according to any one of Claims 1 to 4, wherein the plugging material-filling step is performed with holding a honeycomb structure (1) so that the injection hole gravity center (13) is located above the cell opening gravity center (9) in a direction perpendicular to the cell extension direction (10) so that the plugging material (31) supplied to the inside of the cell (3) received the action of the gravity in addition to the repulsion pressure.
The method for manufacturing a plugged honeycomb structure (61) according to any one of Claims 1 to 5, wherein the plugging material-filling step is performed with holding a honeycomb structure (1) so that the cell extension direction (10) from one end face (4) to the other end face (4) is horizontal.
The method for manufacturing a plugged honeycomb structure (61) according to any one of Claims 1 to 6, wherein, after supplying the plugging material (31) into the cells (3), the plugging material (31 a) present outside the cells (3) across the mask (11) is moved perpendicularly to the extension direction (10) to separate the plugging material (31 a) present outside the cells (3) from the plugging material (31 b) inside the cells (3) in the plugging material-filling step.
The method for manufacturing a plugged honeycomb structure (61) according to any one of Claims 1 to 7, wherein the plugging material (31) has a viscosity of 100 to 700 dPa·s.