Patent Application
20070130897
This application claims benefit of priority based on Japanese Patent Application No. 2005-334781 filed on Nov. 18, 2005, and PCT/JP2006/316633 filed on Aug. 24, 2006. The contents of these applications are incorporated herein by reference in their entirety.
1. Field of the Invention
The present invention relates to a honeycomb structured body, a method for manufacturing a honeycomb structured body, and an exhaust gas purifying device.
2. Discussion of the Background
Recently, particulate matters (fine particles, hereinafter referred to as PM) such as soot, contained in exhaust gases that are discharged from internal combustion engines for vehicles such as a bus, a truck, construction equipment and the like, have raised problems as contaminants harmful to the environment and the human body.
In order to solve those problems, there have been proposed various applications in which a honeycomb structured body, which comprises a honeycomb unit comprising a plurality of cells longitudinally placed in parallel with one other with a cell wall therebetween, is used as filters for capturing PM in exhaust gases to purify the exhaust gases.
As materials for a conventional honeycomb unit, porous silicon carbide, cordierite or the like is known.
As for examples of the conventionally known honeycomb structured body of this kind, a honeycomb structured body in which each corner portion of all cells are provided with a reinforcing member in order to secure strength against thermal stress (for example, see JP-A 9-299731 and JP-A 49-113789), and a honeycomb structured body in which the thickness of cell walls and the size of each cell are enlarged to secure strength for a backwashing process and also to avoid bridging of PM during the backwashing (for example, see JP-A 2-146212) has been disclosed.
Moreover, a honeycomb structured body in which each corner portion of only the cells located at the outer area are provided with a reinforcing member (for example, see JP-A 10-264125) has been disclosed.
Furthermore, a honeycomb structured body in which the thickness of the outer edge wall is increased and the thickness of part of or all of the cell walls is made smaller gradually from the point contacting with the outer edge wall to the inner side (for example, see JP-A 2003-10616) has been disclosed.
The contents of JP-A 9-299731, JP-A 49-113789, JP-A 2-146212, JP-A 10-264125, and JP-A 2003-10616 are incorporated herein by reference in their entirety.
A honeycomb structured body of the present invention is a honeycomb structured body in which
a plurality of porous ceramic members are combined with one another by interposing an adhesive layer, each of the porous ceramic members having a plurality of cells placed in parallel with one another in a longitudinal direction with a cell wall therebetween and an outer edge wall on the outer edge surface thereof, wherein
the thickness of the outer edge wall of the porous ceramic member is greater than the thickness of the cell wall, and each of the porous ceramic members has a filling body which is provided so as to fill in at least one corner portion of at least one outermost cell of the porous ceramic members.
In the honeycomb structured body, the filling body is desirably provided at a corner portion constituted by the outer edge wall and a corner portion constituted by the outer edge wall and the cell wall, and a cross-sectional shape of the outermost cells at the face orthogonal to the longitudinal direction of the cells is desirably an almost tetragon, and a cross-sectional shape of the filling body at the face orthogonal to the longitudinal direction of the cells is desirably an almost right triangle or a shape of an almost right triangle in which the hypotenuse is curved or bent toward the inside or outside of the cell.
The porosity of the porous ceramic members is desirably set to at least about 45% and at most about 55%, and the aperture ratio of the cells at the cross-section perpendicular to the longitudinal direction of each of the porous ceramic members is desirably set to at least about 60% and at most about 75%.
In the honeycomb structured body, desirably either one of the both end portions of the cell is sealed.
In the honeycomb structured body, desirably, the thickness of the outer edge wall is at least about 1.3 times and at most about 3.0 times the thickness of the cell wall. Further, the thickness of the cell wall is desirably at least about 0.1 mm and at most about 0.4 mm, and more desirably in the range of about 0.2 mm to about 0.3 mm.
In the honeycomb structured body, the cross-sectional shape of the filling body is desirably an almost right triangle, and the length of one side of the almost right triangle is desirably at least about 5% and at most about 40% of the length of one side of the outermost cell. Further, the cross-sectional shape of the filling body is desirably a shape of an almost right triangle in which the hypotenuse is curved or bent toward the inside or outside of the cells, and the length of one side of the almost right triangle is desirably at least about 5% and at most about 40% of the length of one side of the outermost cell.
On the honeycomb structured body, desirably, a catalyst is supported.
The honeycomb structured body of the present invention is a honeycomb structured body in which
a plurality of porous ceramic members are combined with one another by interposing an adhesive layer, each of the porous ceramic members having a plurality of cells placed in parallel with one another in a longitudinal direction with a cell wall therebetween and an outer edge wall on the outer edge surface thereof,
wherein
the plurality of porous ceramic members comprise at least two kinds of porous ceramic members having different shapes,
the thickness of the outer edge wall of the porous ceramic member is greater than the thickness of the cell wall, and
each of the porous ceramic members has a filling body which is provided so as to fill in at least one corner portion of at least one outermost cell of the porous ceramic members.
In the honeycomb structured body, the filling body is desirably provided at a corner portion constituted by the outer edge wall and a corner portion constituted by the outer edge wall and the cell wall, and a cross-sectional shape of the outermost cells at the face orthogonal to the longitudinal direction of the cells is desirably an almost tetragon, and a cross-sectional shape of the filling body at the face orthogonal to the longitudinal direction of the cells is desirably an almost right triangle or a shape of an almost right triangle in which the hypotenuse is curved or bent toward the inside or outside of the cell.
The porosity of the porous ceramic members is desirably set to at least about 45% and at most about 55%, and the aperture ratio of the cells at the cross-section perpendicular to the longitudinal direction of each of the porous ceramic members is desirably set to at least about 60% and at most about 75%.
In the honeycomb structured body, desirably either one of the both end portions of the cell is sealed.
In the honeycomb structured body, desirably, the thickness of the outer edge wall is at least about 1.3 times and at most about 3.0 times the thickness of the cell wall. Further, the thickness of the cell wall is desirably at least about 0.1 mm and at most about 0.4 mm, and more desirably in the range of about 0.2 mm to about 0.3 mm.
In the honeycomb structured body the cross-sectional shape of the filling body is desirably an almost right triangle, and the length of one side of the almost right triangle is desirably at least about 5% and at most about 40% of the length of one side of the outermost cell. Further, the cross-sectional shape of the filling body is desirably a shape of an almost right triangle in which the hypotenuse is curved or bent toward the inside or outside of the cells, and the length of one side of the almost right triangle is desirably at least about 5% and at most about 40% of the length of one side of the outermost cell.
On the honeycomb structured body, desirably, a catalyst is supported.
A method for manufacturing a honeycomb structured body according to the present invention comprises:
manufacturing a ceramic molded body through extrusion-molding, using a material paste containing a ceramic material as a main component, the ceramic molded body having a plurality of cells placed in parallel with one another in the longitudinal direction with a cell wall therebetween;
manufacturing a plurality of porous ceramic members through manufacturing of the porous ceramic members by degreasing and firing the ceramic molded body, each of the porous ceramic members having a plurality of cells placed in parallel with one another in the longitudinal direction with a cell wall therebetween;
manufacturing a porous ceramic member aggregated body by aggregating the plurality of porous ceramic members by interposing an adhesive paste layer; and
drying the adhesive paste layer to solidify the adhesive paste layer,
wherein
upon manufacturing the ceramic molded body, a die is used such that a corner portion of a cell is formed into a shape that is provided with a filling body,
the thickness of the outer edge wall of the porous ceramic member is greater than the thickness of the cell wall of the porous ceramic member, and
each of the porous ceramic members has a filling body which is provided so as to fill in at least one corner portion of at least one outermost cell of the porous ceramic members.
In the method for manufacturing a honeycomb structured body, the filling body is desirably provided at a corner portion constituted by the outer edge wall, and a corner portion constituted by the outer edge wall and the cell wall of the porous ceramic members.
Further, it is desirable that a cross-sectional shape of the outermost cells at the face orthogonal to the longitudinal direction of the cells of the porous ceramic members is an almost tetragon, and a cross-sectional shape of the filling body at the face orthogonal to the longitudinal direction of the cells of the porous ceramic members is an almost right triangle or a shape of an almost right triangle in which the hypotenuse is curved or bent toward the inside or outside of the cells of the porous ceramic members.
In the method for manufacturing a honeycomb structured body, it is desirable that the porosity of the porous ceramic members is at least about 45% and at most about 55%, and the aperture ratio of the cells at the cross-section perpendicular to the longitudinal direction of each of the porous ceramic members is at least about 60% and at most about 75%.
The method for manufacturing a honeycomb structured body further comprises
sealing the cells of the ceramic molded body by filling a plug material paste into either one of the both end portions of each of the cells, after manufacturing the ceramic molded body.
In the method for manufacturing a honeycomb structured body, desirably, the thickness of the outer edge wall is at least about 1.3 times and at most about 3.0 times the thickness of the cell wall of the porous ceramic members.
Further, in the method for manufacturing a honeycomb structured body, the thickness of the cell wall of the porous ceramic members is desirably at least about 0.1 mm and at most about 0.4 mm, and more desirably in the range of about 0.2 mm to about 0.3 mm.
In the method for manufacturing a honeycomb structured body, it is desirable that the cross-sectional shape of the filling body is an almost right triangle, and the length of one side of the almost right triangle is desirably at least about 5% and at most about 40% of the length of one side of the outermost cell of the porous ceramic members.
Further, the cross-sectional shape of the filling body is desirably a shape of an almost right triangle in which the hypotenuse is curved or bent toward the inside or outside of the cells of the porous ceramic members, and the length of one side of the almost right triangle is desirably at least about 5% and at most about 40% of the length of one side of the outermost cell of the porous ceramic members.
The method for manufacturing a honeycomb structured body further comprises
supporting a catalyst on the porous ceramic members after firing the ceramic molded body or after drying the adhesive paste layer to solidify the adhesive paste layer in the manufacturing of the porous ceramic members.
The method for manufacturing a honeycomb structured body further comprises
manufacturing a ceramic block by drying the adhesive paste layer to solidify the adhesive paste layer, the ceramic block comprising a plurality of porous ceramic members that are combined with one another by interposing an adhesive layer; and
forming a sealing material layer on the peripheral portion of the ceramic block.
A method for manufacturing a honeycomb structured body according to the present invention comprises:
manufacturing a ceramic molded body through extrusion-molding, using a material paste containing a ceramic material as a main component, the ceramic molded body having a plurality of cells placed in parallel with one another in the longitudinal direction with a cell wall therebetween;
manufacturing a plurality of porous ceramic members through manufacturing of the porous ceramic members by degreasing and firing the ceramic molded body, each of the porous ceramic members having a plurality of cells placed in parallel with one another in the longitudinal direction with a cell wall therebetween;
manufacturing a porous ceramic member aggregated body by aggregating the plurality of porous ceramic members by interposing an adhesive paste layer; and
drying the adhesive paste layer to solidify the adhesive paste layer,
wherein
upon manufacturing the porous ceramic member aggregated body, at least two kinds of porous ceramic members having different shapes are aggregated,
the thickness of the outer edge wall of the porous ceramic member is greater than the thickness of the cell wall of the porous ceramic member, and
each of the porous ceramic members has a filling body which is provided so as to fill in at least one corner portion of at least one outermost cell of the porous ceramic members.
In the method for manufacturing a honeycomb structured body, the filling body is desirably provided at a corner portion constituted by the outer edge wall, and a corner portion constituted by the outer edge wall and the cell wall of the porous ceramic members.
Further, it is desirable that a cross-sectional shape of the outermost cells at the face orthogonal to the longitudinal direction of the cells of the porous ceramic members is an almost tetragon, and a cross-sectional shape of the filling body at the face orthogonal to the longitudinal direction of the cells of the porous ceramic members is an almost right triangle or a shape of an almost right triangle in which the hypotenuse is curved or bent toward the inside or outside of the cells of the porous ceramic members.
In the method for manufacturing a honeycomb structured body, it is desirable that the porosity of the porous ceramic members is at least about 45% and at most about 55%, and the aperture ratio of the cells at the cross-section perpendicular to the longitudinal direction of each of the porous ceramic members is at least about 60% and at most about 75%.
The method for manufacturing a honeycomb structured body further comprises
sealing the cells of the ceramic molded body by filling a plug material paste into either one of the both end portions of each of the cells, after manufacturing the ceramic molded body.
In the method for manufacturing a honeycomb structured body, desirably, the thickness of the outer edge wall is at least about 1.3 times and at most about 3.0 times the thickness of the cell wall of the porous ceramic members.
Further, in the method for manufacturing a honeycomb structured body, the thickness of the cell wall of the porous ceramic members is desirably at least about 0.1 mm and at most about 0.4 mm, and more desirably in the range of about 0.2 mm to about 0.3 mm.
In the method for manufacturing a honeycomb structured body, it is desirable that the cross-sectional shape of the filling body is an almost right triangle, and the length of one side of the almost right triangle is desirably at least about 5% and at most about 40% of the length of one side of the outermost cell of the porous ceramic members.
Further, the cross-sectional shape of the filling body is desirably a shape of an almost right triangle in which the hypotenuse is curved or bent toward the inside or outside of the cells of the porous ceramic members, and the length of one side of the almost right triangle is desirably at least about 5% and at most about 40% of the length of one side of the outermost cell of the porous ceramic members.
The method for manufacturing a honeycomb structured body further comprises
supporting a catalyst on the porous ceramic members after firing the ceramic molded body or after drying the adhesive paste layer to solidify the adhesive paste layer in the manufacturing of the porous ceramic members.
The method for manufacturing a honeycomb structured body further comprises
manufacturing a ceramic block by drying the adhesive paste layer to solidify the adhesive paste layer, the ceramic block comprising a plurality of porous ceramic members that are combined with one another by interposing an adhesive layer; and
forming a sealing material layer on the peripheral portion of the ceramic block.
A method for manufacturing a honeycomb structured body according to the present invention comprises:
manufacturing a ceramic molded body through extrusion-molding, using a material paste containing a ceramic material as a main component, the ceramic molded body having a plurality of cells placed in parallel with one another in the longitudinal direction with a cell wall therebetween;
manufacturing a plurality of porous ceramic members through manufacturing of the porous ceramic members by degreasing and firing the ceramic molded body, each of the porous ceramic members having a plurality of cells placed in parallel with one another in the longitudinal direction with a cell wall therebetween;
manufacturing a porous ceramic member aggregated body by aggregating the plurality of porous ceramic members by interposing an adhesive paste layer; and
drying the adhesive paste layer to solidify the adhesive paste layer,
wherein
in the manufacturing of the porous ceramic members, a filling body is formed after manufacturing of the ceramic molded body, the filling body provided so as to fill in at least one corner portion of at least one outermost cell of each of the porous ceramic members,
the thickness of the outer edge wall of the porous ceramic member is greater than the thickness of the cell wall of the porous ceramic member.
In the method for manufacturing a honeycomb structured body, the filling body is desirably provided at a corner portion constituted by the outer edge wall, and a corner portion constituted by the outer edge wall and the cell wall of the porous ceramic members.
Further, it is desirable that a cross-sectional shape of the outermost cells at the face orthogonal to the longitudinal direction of the cells of the porous ceramic members is an almost tetragon, and a cross-sectional shape of the filling body at the face orthogonal to the longitudinal direction of the cells of the porous ceramic members is an almost right triangle or a shape of an almost right triangle in which the hypotenuse is curved or bent toward the inside or outside of the cells of the porous ceramic members.
In the method for manufacturing a honeycomb structured body, it is desirable that the porosity of the porous ceramic members is at least about 45% and at most about 55%, and the aperture ratio of the cells at the cross-section perpendicular to the longitudinal direction of each of the porous ceramic members is at least about 60% and at most about 75%.
The method for manufacturing a honeycomb structured body further comprises
sealing the cells of the ceramic molded body by filling a plug material paste into either one of the both end portions of each of the cells, after manufacturing the ceramic molded body.
In the method for manufacturing a honeycomb structured body, desirably, the thickness of the outer edge wall is at least about 1.3 times and at most about 3.0 times the thickness of the cell wall of the porous ceramic members.
Further, in the method for manufacturing a honeycomb structured body, the thickness of the cell wall of the porous ceramic members is desirably at least about 0.1 mm and at most about 0.4 mm, and more desirably in the range of about 0.2 mm to about 0.3 mm.
In the method for manufacturing a honeycomb structured body, it is desirable that the cross-sectional shape of the filling body is an almost right triangle, and the length of one side of the almost right triangle is desirably at least about 5% and at most about 40% of the length of one side of the outermost cell of the porous ceramic members.
Further, the cross-sectional shape of the filling body is desirably a shape of an almost right triangle in which the hypotenuse is curved or bent toward the inside or outside of the cells of the porous ceramic members, and the length of one side of the almost right triangle is desirably at least about 5% and at most about 40% of the length of one side of the outermost cell of the porous ceramic members.
The method for manufacturing a honeycomb structured body further comprises
supporting a catalyst on the porous ceramic members after firing the ceramic molded body or after drying the adhesive paste layer to solidify the adhesive paste layer in the manufacturing of the porous ceramic members.
The method for manufacturing a honeycomb structured body further comprises
manufacturing a ceramic block by drying the adhesive paste layer to solidify the adhesive paste layer, the ceramic block comprising a plurality of porous ceramic members that are combined with one another by interposing an adhesive layer; and
forming a sealing material layer on the peripheral portion of the ceramic block.
An exhaust gas purifying device according to the present invention comprises
a honeycomb structured body in which a plurality of porous ceramic members are combined with one another by interposing an adhesive layer, each of the porous ceramic members having a plurality of cells placed in parallel with one another in a longitudinal direction with a cell wall therebetween and having an outer edge wall on the outer edge surface thereof;
a casing that covers the periphery of the honeycomb structured body; and
a holding sealing material that is placed between the honeycomb structured body and the casing,
one end of the casing at an exhaust gas inlet side being connected to an introducing pipe that is connected to an internal combustion system,
the other end of the casing being connected to an exhaust pipe that is connected to the outside,
the thickness of the outer edge wall of the porous ceramic member is greater than the thickness of the cell wall, and
each of the porous ceramic members has a filling body which is provided so as to fill in at least one corner portion of at least one outermost cell of the porous ceramic members.
In the exhaust gas purifying device, the filling body is desirably provided at a corner portion constituted by the outer edge wall and a corner portion constituted by the outer edge wall and the cell wall, and a cross-sectional shape of the outermost cells at the face orthogonal to the longitudinal direction of the cells is desirably an almost tetragon, and a cross-sectional shape of the filling body at the face orthogonal to the longitudinal direction of the cells is desirably an almost right triangle or a shape of an almost right triangle in which the hypotenuse is curved or bent toward the inside or outside of the cell.
The porosity of the porous ceramic members is desirably set to at least about 45% and at most about 55%, and the aperture ratio of the cells at the cross-section perpendicular to the longitudinal direction of each of the porous ceramic members is desirably set to at least about 60% and at most about 75%.
In the exhaust gas purifying device, desirably either one of the both end portions of the cell is sealed.
In the exhaust gas purifying device, desirably, the thickness of the outer edge wall is at least about 1.3 times and at most about 3.0 times the thickness of the cell wall. Further, the thickness of the cell wall is desirably at least about 0.1 mm and at most about 0.4 mm, and more desirably in the range of about 0.2 mm to about 0.3 mm.
In the exhaust gas purifying device the cross-sectional shape of the filling body is desirably an almost right triangle, and the length of one side of the almost right triangle is desirably at least about 5% and at most about 40% of the length of one side of the outermost cell. Further, the cross-sectional shape of the filling body is desirably a shape of an almost right triangle in which the hypotenuse is curved or bent toward the inside or outside of the cells, and the length of one side of the almost right triangle is desirably at least about 5% and at most about 40% of the length of one side of the outermost cell.
On the honeycomb structured body of the exhaust gas purifying device, desirably, a catalyst is supported.
An exhaust gas purifying device according to the present invention comprises
a honeycomb structured body in which a plurality of porous ceramic members are combined with one another by interposing an adhesive layer, each of the porous ceramic members having a plurality of cells placed in parallel with one another in a longitudinal direction with a cell wall therebetween and having an outer edge wall on the outer edge surface thereof;
a casing that covers the periphery of the honeycomb structured body; and
a holding sealing material that is placed between the honeycomb structured body and the casing,
one end of the casing at an exhaust gas inlet side being connected to an introducing pipe that is connected to an internal combustion system,
the other end of the casing being connected to an exhaust pipe that is connected to the outside,
wherein
the plurality of porous ceramic members comprise at least two kinds of porous ceramic members having different shapes,
the thickness of the outer edge wall of the porous ceramic member is greater than the thickness of the cell wall, and
each of the porous ceramic members has a filling body which is provided so as to fill in at least one corner portion of at least one outermost cell of the porous ceramic members.
In the exhaust gas purifying device, the filling body is desirably provided at a corner portion constituted by the outer edge wall and a corner portion constituted by the outer edge wall and the cell wall, and a cross-sectional shape of the outermost cells at the face orthogonal to the longitudinal direction of the cells is desirably an almost tetragon, and a cross-sectional shape of the filling body at the face orthogonal to the longitudinal direction of the cells is desirably an almost right triangle or a shape of an almost right triangle in which the hypotenuse is curved or bent toward the inside or outside of the cell.
The porosity of the porous ceramic members is desirably set to at least about 45% and at most about 55%, and the aperture ratio of the cells at the cross-section perpendicular to the longitudinal direction of each of the porous ceramic members is desirably set to at least about 60% and at most about 75%.
In the exhaust gas purifying device, desirably either one of the both end portions of the cell is sealed.
In the exhaust gas purifying device, desirably, the thickness of the outer edge wall is at least about 1.3 times and at most about 3.0 times the thickness of the cell wall. Further, the thickness of the cell wall is desirably at least about 0.1 mm and at most about 0.4 mm, and more desirably in the range of about 0.2 mm to about 0.3 mm.
In the exhaust gas purifying device the cross-sectional shape of the filling body is desirably an almost right triangle, and the length of one side of the almost right triangle is desirably at least about 5% and at most about 40% of the length of one side of the outermost cell. Further, the cross-sectional shape of the filling body is desirably a shape of an almost right triangle in which the hypotenuse is curved or bent toward the inside or outside of the cells, and the length of one side of the almost right triangle is desirably at least about 5% and at most about 40% of the length of one side of the outermost cell.
On the honeycomb structured body of the exhaust gas purifying device, desirably, a catalyst is supported.
The honeycomb structured body according to the embodiments of the present invention is a honeycomb structured body in which
a plurality of porous ceramic members are combined with one another by interposing an adhesive layer, each of the porous ceramic members having a plurality of cells placed in parallel with one another in a longitudinal direction with a cell wall therebetween and an outer edge wall on the outer edge surface thereof, wherein
the thickness of the outer edge wall of the porous ceramic member is greater than the thickness of the cell wall, and each of the porous ceramic members has a filling body which is provided so as to fill in at least one corner portion of at least one outermost cell of the porous ceramic members.
Referring to the figures, the honeycombs structured body according to the embodiments of the present invention will be described below.
As shown in
With respect to the honeycomb structured body 10 shown in
As shown in
In the porous ceramic member 20, the aperture ratio of the cells at a cross-section perpendicular to the longitudinal direction is desirably set to at least about 60% and at most about 75%.
The aperture ratio of about 60% or more may prevent the pressure loss from increasing too much in the honeycomb structured body, whereas the aperture ratio about 75% or less may prevent the strength from being deteriorated, and in the case where the strength is not deteriorated, cracks are less likely to occur in the porous ceramic member constituting the honeycomb structured body. The more desirable lower limit value is about 65%.
The aperture ratio of the cells used here means the ratio occupied by cells in a cross-section perpendicular to the longitudinal direction of the porous ceramic member 20. The above-mentioned perpendicular cross-section refers to a cross-section that is not sealed by a plug.
In the porous ceramic member, the lower limit of the porosity is desirably set to about 45%, and the upper limit thereof is desirably set to about 55%.
The porosity of about 45% or more may prevent the pressure loss from increasing too much, whereas the porosity of about 55% or less may prevent the strength from being deteriorated. The more desirable lower limit is about 47% and the more desirable upper limit is about 53%.
Here, the porosity can be measured through known methods such as a mercury injection method, Archimedes method and a measuring method using a scanning electron microscope (SEM).
Moreover, in the porous ceramic member 20, the thickness (L3 in
By forming into a structure of this kind, the porosity and the aperture ratio are more easily maintained so that the pressure loss can be kept low more easily, and also the strength can more easily be secured.
Here, the thickness L3 of the outer edge wall 23a is desirably at least about 1.3 times and at most about 3.0 times the thickness L4 of the cell wall 23b.
When the value is about 1.3 times or more, the effect of securing the strength tends to be easily obtained, and when the value is about 3.0 times or less, it tends to become unnecessary that the thickness of the cell wall 23b be made smaller to secure the aperture ratio, with the result that damage such as cracks are less likely to occur in the cell wall 23b.
The lower limit of the thickness L4 of the cell wall 23b is desirably set to about 0.1 mm and the upper limit thereof is desirably set to about 0.4 mm.
In the case where the thickness L4 of the cell wall 23b is about 0.1 mm or more, the strength of the cell wall 23b is prevented from becoming too low that damage such as cracks are less likely to occur. On the other hand, in the case where the thickness L4 of the cell wall 23b is about 0.4 mm or less, the aperture ratio can more easily be maintained at a high level, and as a result, the pressure loss can be prevented from becoming too high.
The more desirable lower limit of the thickness L4 of the cell wall 23b is about 0.2 mm and the more desirable upper limit thereof is about 0.3 mm.
According to the honeycomb structured body in accordance with the embodiments of the present invention, a filling body is provided in at least one corner portion of at least one outermost cell of the porous ceramic members.
The cross-sectional shape of the outermost cells at a face orthogonal to the longitudinal direction of the cells is desirably an almost tetragon, although not particularly limited thereto.
Also, the cross-sectional shape of the filling body at the face orthogonal to the longitudinal direction of the cells is desirably an almost right triangle or a shape of an almost right triangle in which the hypotenuse is curved or bent toward the inside or outside of the cell, although not particularly limited thereto.
In particular, the right triangle is desirably an isosceles right triangle, because with this shape, the shape of the filling body becomes symmetrical across the corner portion, and the weight balance and the balance of thermal conductivity around the corner portion tend to become excellent, and therefore it becomes possible to efficiently disperse heat and stress applied to the porous ceramic member.
The shape in which the hypotenuse is curved or bent refers to a shape in which a line connecting the two apexes on the two acute angles among the three apexes of a right triangle is smoothly curved as shown in
According to the honeycomb structured body in accordance with the embodiments of the present invention, it is satisfactory if the filling body is provided in at least one corner portion of at least one outermost cell of the porous ceramic, and the position thereof is not limited and the number thereof may be any number, provided that it is one or larger. However, the filling body is desirably provided at a corner portion constituted by the outer edge wall, and at a corner portion constituted by the outer edge wall and the cell wall.
The corner portion constituted by the outer edge wall and the cell wall refers to a corner portion at the bifurcation point of the outer edge wall 23a and the cell wall 23b among corner portions of outermost cells 21a. On the other hand, the corner portion constituted by the outer edge wall refers to, in the porous ceramic member 20 shown in
Specifically, as shown in
According to the honeycomb structured body in accordance with the embodiments of the present invention, although it is satisfactory if there is at least one outermost cell, which is provided with a filling body that fills in the corner portions, the number of such cells is desirably as large as possible, and more desirably all the outermost cells are provided with a filling body that fills in the corner portions.
By providing corner portions of outermost cells 21a with a filling body that fills in the corner portions as mentioned above, it becomes possible to secure the strength of the porous ceramic member, and at the same time the secure the aperture ratio without reducing the thickness of the cell walls; thus, the pressure loss can be kept at a low level more easily and occurrence of damage such as cracks can also be avoided more easily.
In the porous ceramic member shown in
In the outermost cell 21a, the length (L2 in
The length L2 of about 5% or more may prevent cases in which effects of forming filling bodies can not be enjoyed, whereas the length L2 of about 40% or less tends to prevent the outermost cells from becoming too small.
For example, when the length of one side of the outermost cell 21a before providing the filling body is about 1.2 mm, the length L2 of one side of the filling body having a right triangle shape is desirably at least about 0.06 mm and at most about 0.48 mm.
In
Here, in
According to the honeycomb structured body in accordance with the embodiments of the present invention, by applying the constitution as mentioned above, it becomes possible to maintain the pressure loss at a low level, and secure the strength; as a result, it also becomes possible to prevent damage such as cracks from occurring. In addition, it becomes possible to avoid the occurrence of damage such as chip caused due to grasp by machine in the manufacturing process or contact between the ceramic members and the like.
In the porous ceramic member 20, either one end portion of the two end portions of each of the cells 21 is sealed with a plug 22; however, in the honeycomb structured body according to the embodiments of the present invention, an end portion of each of the cells in the porous ceramic member is not necessarily sealed, and the end portion may be sealed depending on the use of the honeycomb structured body.
Specifically, for example, when the honeycomb structured body according to the embodiments of the present invention is used as DPF (Diesel Particulate Filter), an end portion of the cell is desirably sealed, whereas when the honeycomb structured body according to the above-mentioned embodiments is used as a catalyst supporting carrier, it is not necessarily sealed at the end portion of the cell.
Moreover, it is satisfactory if the honeycomb structured body according to the embodiments of the present invention has at least one porous ceramic member having the above-mentioned characteristics and structure, however, it is more desirable to have a larger number of the porous ceramic member having the above-mentioned characteristics and structure.
The porous ceramic member is mainly made of porous ceramics, and examples of the material include nitride ceramics such as aluminum nitride, silicon nitride, boron nitride and titanium nitride; carbide ceramics such as silicon carbide, zirconium carbide, titanium carbide, tantalum carbide and tungsten carbide; andoxide ceramics suchas alumina, zirconia, cordierite, mullite, silica and aluminum titanate, and the like. Here, the porous ceramic member may be formed as a composite body of silicon and silicon carbide. In the case where the composite body of silicon and silicon carbide is used, silicon is desirably added thereto to make up to at least about 0% by weight and at most about 45% by weight of the entire body.
With respect to the material of the porous ceramic member when the porous ceramic member is used as DPF, a silicon carbide based ceramic which is superior in heat resistance and mechanical characteristics, and in addition, has a high thermal conductivity, is desirably used. Here, the silicon carbide based ceramic refers to a material having a silicon carbide content of about 60% by weight or more.
Moreover, with respect to the average pore diameter of the porous ceramic member, although not particularly limited, the lower limit value is desirably set to about 1 μm, and the upper limit value is desirably set to about 50 μm. More desirably, the lower limit value is set to about 5 μm, and the upper limit value is set to about 30 μm. The average pore diameter of about 1 μm or more tends to prevent the pressure loss from becoming high, whereas the average pore diameter of about 50 μm or less prevents PM to easily pass through the pores, and thus it becomes possible to surely capture the PM to prevent the capture efficiency of PM from being deteriorated.
The area of a cross-section perpendicular to the longitudinal direction of the porous ceramic member is not particularly limited, but normally the cross-section with the area of at least about 5 cm2 and at most about 50 cm2 is desirably used.
The area of about 5 cm2 or more prevents an effective filtration area as filter from becoming too small, whereas the area of about 50 cm2 or less tends to prevent occurrence of damage such as cracks due to thermal stress upon production and in use.
The plug 22 that seals the end portion of the porous ceramic member and the cell wall 23 are desirably made from the same porous ceramic material. With this arrangement, the contact strength between the two members tends to be increased, and moreover, by adjusting the porosity of the plug 22 in the same manner as the cell walls 23, it becomes possible to properly adjust the coefficient of thermal expansion of the cell walls 23 and the coefficient of thermal expansion of the plug 22 so that it becomes possible to prevent a gap from being generated between the plug 22 and the cell walls 23 due to a thermal stress upon production and in use and also to prevent cracks from occurring in the plug 22 and in portions of the cell walls 23 that are made in contact with the plug 22.
With respect to the length of the plug 22, although not particularly limited, in the case where the plug 22 is made from porous silicon carbide, for example, the lower limit value is desirably set to about 1 mm, whereas the upper limit value is desirably set to about 20 mm.
The length of the plug of about 1 mm or more may enable secure sealing of the end portion of the cells, whereas the length of the plug about 20 mm or less tends to prevent the effective filtration area of the honeycomb structured body from becoming small.
More desirably, the lower limit value of the length of the plug is about 2 mm and the upper limit value thereof is about 10 mm.
In the honeycomb structured body 10, the sealing material layer (adhesive layer) 11 is formed between the porous ceramic members 20, allowing to have a function that prevents leakage of exhaust gases, and also functions as a bonding material used for binding a plurality of the porous ceramic members 20 to one another. On the other hand, the sealing material layer (coat layer) 12, which is formed on the outer peripheral face of the ceramic block 15, is also allowed to function as a plug used for preventing exhaust gases passing through the cells from leaking from the outer peripheral face of the ceramic block 15 when the honeycomb structured body 10 is placed in an exhaust passage of an internal combustion engine, and is also allowed to function as an reinforcing member used for adjusting the external shape of the ceramic block 15 as well as strengthening the outer peripheral portion of the ceramic block 15.
Here, in the honeycomb structured body 10, the adhesive layer 11 and the coat layer 12 may be formed by using the same material, or may be formed by using different materials. In the case where the adhesive layer 11 and the coat layer 12 are made from the same material, the compounding ratio of the materials may be the same or may be different. Moreover, the material may have either a dense structure or a porous structure.
Examples of the material used for forming the adhesive layer 11 and the coat layer 12 include, although not particularly limited, a material made from inorganic fibers and/or inorganic particles in addition to an inorganic binder and an organic binder.
Examples of the above-mentioned inorganic binder include silica sol, alumina sol and the like. Each of these materials may be used alone, or two or more kinds of these may be used in combination. Among the above-mentioned inorganic binders, silica sol is more desirably used.
Examples of the organic binder include polyvinyl alcohol, methyl cellulose, ethyl cellulose, carboxymethyl cellulose and the like. Each of these may be used alone or two or more kinds of these may be used in combination. Among the organic binders, carboxymethyl cellulose is more desirably used.
Examples of the inorganic fibers include ceramic fiber such as alumina, silica, silica-alumina, glass, potassium titanate, aluminum borate, and the like. Examples thereof may further include whiskers made of alumina, silica, zirconia, titania, ceria, mullite, silicon carbide and the like. Each of these may be used alone, or two or more kinds of these may be used in combination. Among the inorganic fibers, alumina fibers are more desirably used.
Examples of the inorganic particles include carbides, nitrides and the like, more specifically, inorganic powder, made from silicon carbide, silicon nitride, boron nitride and the like. Each of these may be used alone, or two or more kinds of these may be used in combination. Among the above-mentioned inorganic particles, silicon carbide, which is superior in thermal conductivity, is more desirably used.
Moreover, balloons that are fine hollow spheres comprising oxide-based ceramics and a pore-forming agent such as spherical acrylic particles or graphite may be added to the above-mentioned paste used for forming the sealing material layer, if necessary.
Examples of the above-mentioned balloons include, although not particularly limited, alumina balloons, glass micro-balloons, shirasu balloons, flyash balloons (FA balloons), mullite balloons and the like. Among these, alumina balloons are more desirably used.
Moreover, a catalyst may be supported on the honeycomb structured body according to the embodiments of the present invention.
In the honeycomb structured body according to the embodiments of the present invention, by supporting a catalyst that is capable of converting toxic gas components such as CO, HC, NOx in exhaust gases, it becomes possible to sufficiently convert toxic gas components in exhaust gases through a catalytic reaction. Further, by supporting a catalyst that helps the burning of PM, it becomes possible to burn and remove the PM more easily. Consequently, the honeycomb structured body according to the embodiments of the present invention makes it possible to improve the performance of converting gas components in exhaust gases, and further to reduce the energy for burning the PM.
Examples of the catalyst include a catalyst made of noble metals such as platinum, palladium, rhodium, although not particularly limited thereto. The catalyst may be supported by including an element such as an alkali metal (Group 1 in Element Periodic Table), an alkali earth metal (Group 2 in Element Periodic Table), a rare-earth element (Group 3 in Element Periodic Table) and a transition metal element, in addition to the above-mentioned noble metals.
Moreover, when the above-mentioned catalyst is adhered to the honeycomb structured body, the catalyst may be adhered thereto after the surface has been preliminarily coated with a catalyst supporting layer made of alumina or the like. With this arrangement, the specific surface area is made greater so that the degree of dispersion of the catalyst is improved and the reaction sites of the catalyst can be increased. Furthermore, it becomes possible to prevent sintering of the catalyst metal by the catalyst supporting layer.
Examples of the material for the catalyst supporting layer include oxide ceramics, such as alumina, titania, zirconia and silica.
Here, the honeycomb structured body according to the embodiments of the present invention with catalyst supported thereon is allowed to function as a gas purifying (converting) device in the same manner as conventionally known DPFs (Diesel Particulate Filters) with a catalyst. Therefore, with respect to the case where the honeycomb structured body according to the embodiments of the present invention is used also as a catalyst supporting carrier, detailed description of the functions thereof is omitted.
A honeycomb structured body is required to have a low pressure loss as its basic characteristics. Effective means to reduce pressure loss include increasing porosity, increasing aperture ratio, and the like. However, a higher porosity, for example, presumably causes deterioration of strength, and in a case where the porosity is raised, while a reinforcing member is provided at cell walls of all the cells, with the thickness of the cell walls being unchanged, for the purpose of securing the strength of the honeycomb structured body, there tends to occur a problem of a reduced aperture ratio, causing an increase in the pressure loss.
Moreover, when the reinforcing members are provided while securing the aperture ratio so as to avoid an increase in the pressure loss, the thickness of the cell walls needs to be reduced, and in such a case, it tends to become difficult to secure the strength of the honeycomb structured body.
In contrast, in the honeycomb structured body according to the embodiments of the present invention, it becomes possible to simultaneously ensure the suppression of the pressure loss at a low level and the securing of the strength, which are the characteristics contradictory to each another.
Namely, the honeycomb structured body according to the embodiments of the present invention makes it possible to suppress the pressure loss and at the same time to secure the strength by keeping the porosity and the aperture ratio of the porous ceramic member in a desired range and increasing the thickness of the outer edge walls, as well as by providing corners of outermost cells with a filling body that fills in the corners.
Further, when an external force is applied to a conventional honeycomb structured body, presumably stress is focused on corner portions of cells, and cracks occur from this focal point of stress. On the other hand, in the honeycomb structured body according to the embodiments of the present invention, since the thickness of the outer edge wall is greater than the thickness of the cell wall, and a filling body is provided so as to fill in at least one corner portion of at least one outermost cell, it is presumed that stress can be prevented from being focused on the corner portion and thus cracks hardly occur. Moreover, the filling body at the corner portion also functions as a reinforcing body to reinforce the cell walls, with the result that it becomes possible to avoid deformation of the cell walls to reduce the occurrence of cracks even when an external stress is applied to the porous ceramic members. Furthermore, in a known honeycomb structured body, when the porosity or the aperture ratio of the porous ceramic members are increased, or the thickness of the cell wall is made smaller, for the purpose of reducing pressure loss, strength of the cell wall is deteriorated. However, in accordance with the honeycomb structured body according to the embodiments of the present invention, it becomes possible to reduce the occurrence of cracks even when the porosity and the aperture ratio are increased or the thickness of the cell wall is made smaller, and as a result, it becomes possible to keep the pressure loss at a low level, secure the strength, and avoid occurrence of damage such as cracks. In addition, it becomes possible to avoid the occurrence of damage such as chips caused due to grasp by machine in the manufacturing process or contact between the ceramic members.
Next, the following description will discuss a method for manufacturing the honeycomb structured body according to the above-mentioned embodiments.
First, an extrusion-molding process is carried out by using a material paste mainly comprising the above-mentioned ceramic material so that a rectangular pillar-shaped ceramic molded body is manufactured.
With respect to the material paste, although not particularly limited, such paste as to set the porosity of porous ceramic members after production to at least about 45% and at most about 55% is desirably used, and for example, a material paste prepared by adding a binder, a dispersant solution and the like to powder (ceramic powder) containing the above-mentioned ceramics may be used.
With respect to the particle diameter of the ceramic powder, although not particularly limited, those which are less susceptible to shrinkage in the succeeding firing process are desirably used, and for example, those powders, prepared by combining 100 parts by weight of powders having an average particle diameter of at least about 3 μm and at most about 70 μm with at least about 5 parts by weight and at most about 65 parts by weight of powders having an average particle diameter of at least about 0.1 μm and at most about 1.0 μm, are preferably used.
Here, an oxidizing process may be carried out on the ceramic powder.
Examples of the above-mentioned binder include, although not particularly limited, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyethylene glycol and the like.
In general, the compounding amount of the above-mentioned binder is desirably set to at least about 1 part by weight and at most about 15 parts by weight with respect to 100 parts by weight of the ceramic powder.
Examples of the dispersant solution include, although not particularly limited, an organic solvent such as benzene, alcohol such as methanol, water, and the like.
An appropriate amount of the above-mentioned dispersant solution is mixed therein so that the viscosity of the material paste is set within a fixed range.
The ceramic powder, the binder and dispersant solution are mixed by an attritor or the like, and sufficiently kneaded by a kneader or the like, and then the resulting material paste is extrusion-molded.
Moreover, a molding auxiliary may be added to the material paste, if necessary.
Examples of the molding auxiliary include, although not particularly limited, ethylene glycol, dextrin, fatty acid, fatty acid soap, polyvinyl alcohol and the like.
Furthermore, balloons that are fine hollow spheres comprising oxide-based ceramics and a pore-forming agent such as spherical acrylic particles and graphite may be added to the above-mentioned material paste.
Examples of the above-mentioned balloons include, although not particularly limited, alumina balloons, glass micro-balloons, shirasu balloons, flyash balloons (FA balloons), mullite balloons and the like. Among these, alumina balloons are more desirably used.
In this process, for carrying out extrusion molding, a die is select so as to form a shape in which corner portions of the predetermined cells are provided with the filling body.
Here, the filing body may be provided in the extrusion molding process as mentioned above, and also may be provided separately in a process after extrusion molding, for example, in a process of providing a plug described below; however, it is desirable to provide the filling body in the extrusion molding process, because an excellent productivity can be obtained.
Next, the above-mentioned ceramic molded body is dried by using a drier such as a microwave drier, a hot-air drier, a dielectric drier, a reduced-pressure drier, a vacuum drier and a freeze drier so that a ceramic dried body is formed. Thereafter, a predetermined amount of plug material paste, which forms plugs, is injected into the end portion on the outlet side of the inlet-side group of cells and the end portion on the inlet side of the outlet-side group of cells so that the cells are sealed.
With respect to the plug material paste, although not particularly limited, such paste as to set the porosity of a plug produced through the succeeding processes to at least about 30% and at most about 75% is desirably used, and for example, the same paste as the above-mentioned material paste may be used.
In this process, it becomes possible to adjust the length of the plug formed through the succeeding processes by adjusting the amount of paste to be injected.
Next, degreasing (for example, at the temperature of at least about 200° C. and at most about 500° C.) and firing (for example, at the temperature of at least about. 1400° C. and at most about 2300° C.) under predetermined conditions are carried out on the ceramic dried body in which the plug material paste is injected so that a porous ceramic member 20 constituted by a single sintered body as a whole, comprising a plurality of cells that are longitudinally placed in parallel with one another through cell walls, in which each of the cells has either one end portion sealed, is manufactured.
Here, with respect to the degreasing and firing conditions of the ceramic dried body, it is possible to apply conditions that have been conventionally used for manufacturing a filter made from porous ceramics.
Next, an adhesive paste to form the adhesive layer 11 is applied to each of the side faces of the porous ceramic member 20 with an even thickness to form an adhesive paste layer, and by repeating a process for successively piling up another porous ceramic member 20 on this adhesive paste layer, a porous ceramic member aggregated body having a predetermined size is manufactured. In order to secure the space between the porous ceramic members 20, there is a method in which a cavity holding member is attached to the surface of the porous ceramic member 20 and a plurality of the porous ceramic members 20 are combined with one another by interposing the cavity holding member so as to manufacture an aggregate body, and then an adhesive material paste is injected into the cavity between the porous ceramic members 20.
With respect to the material for forming the adhesive paste, since it has already been explained, the explanation thereof is omitted.
Next, the porous ceramic member aggregated body is heated so that the adhesive paste layer is dried and solidified to form the adhesive layer 11.
Moreover, by using a diamond cutter and the like, a cutting process is carried out on the porous ceramic member aggregated body in which a plurality of the porous ceramic members 20 are bonded to one another by interposing the adhesive layer 11 so that a ceramic block 15 having a cylindrical shape is manufactured. Also, porous ceramic members having various kinds of shapes may be combined with one another and bonded together by an adhesive, so that a ceramic block having a cylindrical shape as a whole is manufactured.
By forming a sealing material layer 12 on the outer periphery of the ceramic block 15 by using the sealing material paste, a honeycomb structured body 10 in which the sealing material layer 12 is formed on the outer periphery of the cylindrical ceramic block 15 having a plurality of the porous ceramic members 20 bonded to one another by interposing the adhesive layers 11.
Thereafter, a catalyst is supported on the honeycomb structured body, if necessary. The supporting process of a catalyst may be carried out on the porous ceramic member prior to the manufacturing of the aggregated body.
In the case where a catalyst is supported, desirably, an alumina film having a large specific surface area is formed on the surface of the honeycomb structured body, and a co-catalyst as well as a catalyst such as platinum is adhered to the surface of this alumina film.
With respect to the method for forming the alumina film on the surface of the honeycomb structured body, for example, a method in which the honeycomb structured body is impregnated with a solution of a metal compound containing aluminum such as Al(NO3)3 and then heated and a method in which the honeycomb structured body is impregnated with a solution containing alumina powder and then heated can be mentioned.
With respect to the method for adhering the co-catalyst, for example, a method in which the honeycomb structured body is impregnated with a solution of a metal compound containing rare earth element such as Ce(NO3)3 and then heated is proposed.
With respect to the method for supporting the catalyst, for example, a method in which the honeycomb structured body is impregnated with, for example, a nitric acid solution of diammine dinitro platinum ([Pt(NH3)2(NO2)2]HNO3, platinum concentration: about 4.53% by weight) and then heated is proposed.
Moreover, the catalyst may also be supported through a method in which the catalyst is adhered to an alumina particle in advance, to impregnate the honeycomb structured body with a solution containing alumina powder with a catalyst adhered thereto, and heat it thereafter.
As shown in
Furthermore, in
In the exhaust gas purifying device 40 having the above-mentioned configuration, exhaust gases discharged from the internal combustion system such as an engine, are directed into the casing 41 through the introducing pipe 43, and allowed to flow into the honeycomb structured body 10 from inlet-side cells; after having passed through the cell walls where particulates are captured and being purified thereby, the exhaust gases are discharged out of the honeycomb structured body from outlet-side cells, and then discharged to the outside through the exhaust pipe 44.
Moreover, in an exhaust gas filter on which a catalyst for purifying exhaust gases is supported, a toxic component, for example CO, HC, NOx and the like included in exhaust gases are converted to CO2, H2O, N2 and the like, respectively, and discharged outside the bodies.
In the exhaust-gas purifying device 40, after a large quantity of particulates have been accumulated on the cell walls of the honeycomb structured body 10 to cause an increase in pressure loss, a regenerating process is carried out on the honeycomb structured body 10.
In the regenerating process, gases, heated by using a heating means that is not shown herein, are allowed to flow into the honeycomb structured body so that the honeycomb structured body 10 is heated to burn and eliminate the particulates accumulated on the cell walls. Moreover, the particulates may be burned and eliminated by using a post-injection system.
The following description will discuss the present invention in detail by means of examples; however, the present invention is not intended to be limited by these examples.
An α-type silicon carbide powder having an average particle diameter of 22 μm (hereinafter referred to as SiC coarse powder) (6000 parts by weight), 2570 parts by weight of an α-type silicon carbide powder having an average particle diameter of 0.5 μm (hereinafter referred to as SiC fine powder), 700 parts by weight of an organic binder (methyl cellulose), 300 parts by weight of adore forming agent (acrylic resin) having an average particle diameter of 20 μm with pores formed therein, 330 parts by weight of a lubricant (UNILUB, manufactured by NOF Corp.), 150 parts by weight of glycerin, and an appropriate amount of water were blended and evenly mixed to prepare a mixed material composition. This mixed composition was charged into an extrusion molding apparatus, and extrusion molded to manufacture a pillar-shaped raw molded body in which corner portions of cells are provided with a filling body as shown in
Next, the above-mentioned raw molded bodies were dried by using a microwave dryer or the like to prepare ceramic dried bodies, and predetermined cells were then filled with a plug material paste having the same composition as the composition used for extrusion-molding.
Next, after these had been again dried by using a dryer, the resulting products were degreased at 400° C., and fired at 2200° C. in a normal-pressure argon atmosphere for 3 hours to manufacture porous ceramic members 20, each of which comprises a silicon carbide sintered body having a size of 34.3 mm×34.3 mm×150 mm, the number of cells 21 (cell density) of 50.5 pcs/cm2, the size of the cell of 1.17 mm×1.17 mm, a thickness of the cell wall of 0.24 mm, a thickness of the outer edge wall of 0.40 mm, an aperture ratio of 66.4%, and a porosity of 47.5%. Here, the length L2 of one side of a filling body having a right triangle shape (isosceles right triangle shape) provided at corner portions of a square-shaped cell at a cross-section perpendicular to the longitudinal direction of the cells, was set to 10% of the length L1, (=1.17 mm) of one side of the cell before the filling body was provided.
Next, by using a heat resistant adhesive paste containing 30% by weight of alumina fibers having an average fiber length of 20 μm, 21% by weight of silicon carbide particles having an average particle diameter of 0.5 μm, 15% by weight of silica sol, 5.6% by weight of carboxymethyl cellulose and 28.4% by weight of water, a number of the porous ceramic members 20 were bonded to one another, and this was further dried at 120° C., and was cut by using a diamond cutter so that a cylindrical ceramic block 15 with an adhesive material layer having a thickness of 1 mm was manufactured.
Next, ceramic fibers made from alumina silicate (shot content: 3%, average fiber length: 100 μm) (23.3% by weight), which served as inorganic fibers, silicon carbide powder having an average particle diameter of 0.3 μm (30.2% by weight), which served as inorganic particles, silica sol (SiO2 content in the sol: 30% by weight) (7% by weight), which served as an inorganic binder, carboxymethyl cellulose (0.5% by weight), which served as an organic binder, and water (39% by weight) were mixed and kneaded to prepare a sealing material paste.
Next, a sealing material paste layer having a thickness of 0.2 mm was formed on the outer peripheral portion of the ceramic block 15 by using the above-mentioned sealing material paste. Further, this sealing material paste layer was dried at 120° C. so that a cylindrical aggregated honeycomb structured body 10 having a size of 143.8 mm in diameter×150 mm in length was manufactured. Table 2 shows the rate (part by weight) of each material used in the preparation of the above mixed composition.
Tables 1 and 3 show in detail the structures, shapes and dimensions of a porous ceramic member constituting the manufactured honeycomb structured body. In Table 3, (a) to (e) shown in the item of Table 1 mean that porous ceramic members each having the respective structures (a) to (e), which were described in detail in Table 1, were manufactured, and the resulting porous ceramic members were used.
The same processes as those of Example 1 were carried out to manufacture a honeycomb structured body, except that weight ratio of materials for porous ceramic members, cross-sectional shape of filling bodies, porosity, aperture ratio, thickness of cell walls, thickness of outer edge walls, cell density or ratio of the length of one side of a filling body to the length of one side of a cell before forming the filling body (hereinafter, referred to as ratio of one side of a filling body) was changed as shown in Tables 1 to 3.
Moreover, with respect to the cross-sectional shape of the filling body, the expression “the hypotenuse of a right triangle is curved” means that the cross-sectional shape of the filling body was a shape of a right triangle in which a hypotenuse line connecting the two apexes on the acute angles is smoothly curved, and the hypotenuse is curved toward the direction of the apex on the right angle of the right triangle, i.e., toward the outside of the cell (c.f.
The same processes as those of Example 1 were carried out to manufacture a honeycomb structured body, except that weight ratio of materials for porous ceramic members, structure of the porous ceramic member, cross-sectional shape of filling bodies, porosity, aperture ratio, thickness of cell walls, thickness of outer edge walls, cell density or ratio of one side of a filling body was changed as shown in Tables 1 to 3.
Note)
*1 Ratio (%) of one side of filling body means L2/L1 or L5/L1 in the dimensions shown in
The evaluations (measurement) mentioned below were carried out on the honeycomb structured bodies obtained in Examples 1 to 12 and Comparative Examples 1 to 14.
(1) Measurement of Pressure Loss
Each of the porous ceramic members relating to the Examples and the Comparative Examples was connected to a blower, and gas (air flow) was passed therethrough at a flow rate of 13 m/s; thus the pressure loss in the honeycomb structured body was measured. The results are as shown in Table 4.
(2) Measurement of Mechanical Characteristics of Porous Ceramic Member by Means of Iron Ball Dropping
The mechanical characteristics of the porous ceramic members were evaluated by using an iron ball drop impact device as shown in
In this iron ball drop impact device 50, a board member 52 was propped up against a platform 53 at the angle (indicated as α in
(3) Measurement of strength of outer edge wall portions of porous ceramic members using a force gauge
As shown in
As shown in Table 4, the honeycomb structured bodies according to the Examples have a low pressure loss, and tend not to be damaged by dropping of an iron ball (dynamic load). Also, in the measurement using a force gauge (static load), a high pressure was required to cause damage in those honeycomb structured bodies.
On the other hand, the honeycomb structured bodies according to the Comparative Examples have a high pressure loss, or tend to be damaged by dropping of an iron ball, or only a low pressure was required to cause damage therein in the measurement using a force gauge.
The description in the above mainly discusses the honeycomb structured body according to the embodiments of the present invention, by taking a honeycomb structured body which can be suitably used as a ceramic filter as an example. However, in the honeycomb structured body according to the embodiments of the present invention, the honeycomb structured body may be manufactured without being filled with a plug material paste as mentioned above, and the honeycomb structured body in which the end portion of the cells is not sealed with the plug may be suitably used as a catalyst supporting carrier, and such a honeycomb structured body may exert the same effects as the present invention in which the honeycomb structured body is used as a ceramic filter.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-334781 | Nov 2005 | JP | national |
| PCT/JP06/16633 | Aug 2006 | JP | national |
