JP2023149427A - Honeycomb structure, manufacturing method for the same, and shape adjustment method for honeycomb molding - Google Patents

Abstract

To provide a manufacturing method for a honeycomb structure having an electrode layer with excellent thickness uniformity, and to provide the structure.SOLUTION: A manufacturing method for a honeycomb structure including a honeycomb structure part in which the thickness of a partition wall in a center part and the thickness of a partition wall in an outer peripheral part are different from each other includes a step of introducing a molding material from a back plate side and extruding the same, in a state of placing a back plate 70 in which a plurality of flow holes 70a communicating with a plurality of back holes 65a extending in a thickness direction is formed on an introduction part side of a plate-like mouthpiece body 60 having an introduction part 65 for the molding material in which the back holes are formed, and a molding part 66 in which slits 66a communicating with the back holes are formed and the molding material that has passed through the introduction part is formed into a honeycomb formed body. The hole diameters of the communication holes of the back plate change stepwise in a plane and the back plate includes: a first region 71 in which communication holes with relatively large diameters are arranged in parallel; and a second region 72 in which communication holes having relatively small diameters are arranged in parallel.SELECTED DRAWING: Figure 5

Description

The present invention relates to a honeycomb structure, a method for manufacturing the same, and a method for adjusting the shape of a formed honeycomb structure.

Catalyst carriers, in which a catalyst is supported on a carrier, are used to treat harmful substances in exhaust gas emitted from vehicle engines. During treatment, if the catalyst temperature is low when the engine is started, there is a problem that the catalyst is not heated to a predetermined temperature and the exhaust gas is not sufficiently purified. In order to solve these problems, we developed an electrically heated catalyst (electrically heated catalyst) that heats the catalyst supported on the carrier to its activation temperature before or at the time of starting the engine by supplying electricity to a conductive carrier and causing the carrier to generate heat. Development of exhaust gas treatment equipment using EHC is progressing. As such a carrier, Patent Document 1 discloses a ceramic honeycomb structure.

Patent No. 6438939

In order to generate heat in the honeycomb structure, an electrode layer is provided on the side surface thereof. For example, in order to improve the energization heat generation characteristics of the honeycomb structure, the thickness of the disposed electrode layer is required to be more uniform.

In view of the above, an object of the present invention is to provide a honeycomb structure including an electrode layer with excellent thickness uniformity.

A method for manufacturing a honeycomb structure according to an embodiment of the present invention includes a forming step of obtaining a honeycomb formed body by extrusion molding a forming material containing a ceramic raw material, and a forming step of obtaining a honeycomb formed body by drying the honeycomb formed body, and firing a honeycomb dried body obtained by drying the honeycomb formed body to form a honeycomb structure. A method for manufacturing a honeycomb structure, comprising: a firing step for obtaining a structure, wherein the honeycomb structure includes a honeycomb structure having an outer peripheral wall and a partition wall disposed inside the outer peripheral wall; a pair of electrode layers disposed on side surfaces of the honeycomb structure, the honeycomb structure having a center portion and an outer peripheral portion surrounding the center portion in a plane perpendicular to an extending direction of the honeycomb structure. , the thickness of the partition wall in the central part is different from the thickness of the partition wall in the outer peripheral part, and the molding process includes an introduction part for the molding material in which a plurality of back holes extending in the thickness direction are formed, and a thickness of the partition wall in the outer peripheral part. A plurality of slits communicating with the back hole are formed on the introduction part side of the plate-shaped die main body, which has a molding part for forming the molding material that has passed through the introduction part into the honeycomb molded body. The step includes the step of introducing and extruding the molding material from the back plate side in a state where a back plate in which a flow hole is formed is arranged, and the diameter of the plurality of flow holes of the back plate is adjusted stepwise in a plane. The first region has a first region in which communication holes having a relatively large diameter are arranged in parallel, and a second region in which communication holes having a relatively small diameter are arranged in parallel.
In one embodiment, when the molding material is extruded at an extrusion speed of 10 mm/sec to 40 mm/sec for 3 seconds to 25 seconds, the extrusion amount varies within the plane of the molded part of the die body by 2 mm or less. be.
In one embodiment, slits with different slit widths are formed in the molded part, and the slit width of the slit located at the center of the molded part is greater than the slit width of the slit located at the outer periphery of the molded part. It's also big.
In one embodiment, the first region is located at the outer periphery of the backplate, and the second region is located at the center of the backplate.

A method for adjusting the shape of a formed honeycomb body according to another embodiment of the present invention is a method for adjusting the shape of a formed honeycomb body having an outer circumferential wall and a partition wall arranged inside the outer circumferential wall. , in a plane perpendicular to the extending direction of the honeycomb formed body, has a central portion and an outer peripheral portion surrounding the central portion, and the thickness of the partition wall in the central portion is different from the thickness of the partition wall in the outer peripheral portion; The shape adjustment method includes a molding material introduction part in which a plurality of back holes extending in the thickness direction are formed, and a slit communicating with the back holes, and the molding material that has passed through the introduction part is applied to the honeycomb molded body. In a state where a back plate in which a plurality of flow holes communicating with the back hole are formed is disposed on the introduction part side of a plate-shaped mouthpiece body having a molding part to be molded, the molding material is poured from the back plate side. The pore diameters of the plurality of communication holes of the back plate change stepwise in a plane, and the pore diameters are relative to a first region where communication holes having relatively large diameters are arranged in parallel. and a second region in which relatively small flow holes are arranged in parallel.

A honeycomb structure according to yet another embodiment of the present invention is a honeycomb structure having partition walls extending from a first end face to a second end face and defining a plurality of cells serving as fluid flow paths, and an outer peripheral wall located on the outer periphery. a structural part; and a pair of electrode layers disposed on the side surfaces of the honeycomb structure; The thickness of the partition wall in the central part and the thickness of the partition wall in the outer peripheral part are different from each other, and the cell pitch of the cells in a plane perpendicular to the extending direction of the cells of the honeycomb structure part is 1.0 mm or more. It is 1.2 mm or less, and the variation in the cell pitch is 0.1 mm or less.
In one embodiment, the thickness of the outer peripheral wall in a plane perpendicular to the extending direction of the cells of the honeycomb structure is 0.1 mm or more and 0.5 mm or less, and the variation in the thickness of the outer peripheral wall is 0.2 mm. It is as follows.
In one embodiment, the degree of curvature in the extending direction of the cells of the honeycomb structure is 1 mm or less.
In one embodiment, the roundness of a surface of the honeycomb structure perpendicular to the direction in which the cells extend is 1 mm or less.
In one embodiment, the thickness of the electrode layer is 0.1 mm or more and 0.5 mm or less, and the variation in the thickness of the electrode layer is 0.092 mm or less.
In one embodiment, the ratio of the thickness of the partition wall in the outer peripheral part to the thickness of the partition wall in the central part of the honeycomb structure is 0.6 or more and 0.9 or less.

According to the embodiments of the present invention, a honeycomb structure including an electrode layer with excellent thickness uniformity can be obtained.

1 is a perspective view showing a schematic configuration of a honeycomb structure according to one embodiment of the present invention. FIG. 2 is a sectional view of the honeycomb structure shown in FIG. 1. FIG. FIG. 2 is a sectional view of the honeycomb structure shown in FIG. 1. FIG. FIG. 3 is a diagram for explaining cell pitch. FIG. 2 is a cross-sectional view schematically showing a general configuration of each part of a die used in a method for manufacturing a honeycomb structure according to an embodiment of the present invention. It is a figure which shows an example of the exit of a mouthpiece body when the molding material is extruded from the mouthpiece body without using a back plate. FIG. 7 is a diagram illustrating an example of the exit state of the mouthpiece body when molding material is extruded from the mouthpiece body using a back plate.

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. In addition, in order to make the explanation clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the embodiment, but this is just an example and does not limit the interpretation of the present invention. It's not something you do.

A. Honeycomb Structure FIG. 1 is a perspective view showing a schematic configuration of a honeycomb structure according to one embodiment of the present invention, and FIGS. 2 and 3 are cross-sectional views of the honeycomb structure shown in FIG. 1. The honeycomb structure 30 includes a honeycomb structure 10 and a pair of electrode layers 20, 20 that are disposed on the side surfaces of the honeycomb structure 10 and face each other with the honeycomb structure 10 in between.

The honeycomb structure 10 includes a partition wall 14 that extends (in the length direction) from a first end surface 10a to a second end surface 10b and defines a plurality of cells 12 that can serve as fluid flow paths, and a partition wall 14 that is located on the outer periphery. It has a surrounding outer peripheral wall 16. The outer peripheral wall 16 extends in the length direction. Each of the plurality of cells 12 is a space extending in the length direction. The cross-sectional shape of each cell 12 perpendicular to the length direction is approximately a regular hexagon in the illustrated example, but it may have other shapes such as other polygons (for example, triangles, quadrilaterals, pentagons), circles, ellipses, etc. Good too. The cross-sectional shape of the outer peripheral wall 16 perpendicular to the length direction is typically circular, but may be polygonal or elliptical.

For example, from the viewpoint of use as a catalyst carrier, the thickness of the partition wall 14 is preferably 310 μm or less, more preferably 250 μm or less, and even more preferably 230 μm or less. On the other hand, the thickness of the partition wall 14 is preferably 100 μm or more, more preferably 130 μm or more, and even more preferably 150 μm or more, from the viewpoint of strength, for example.

In a plane perpendicular to the direction in which the cells 12 extend (the central axis of the honeycomb structure 10 ), the honeycomb structure 10 has a center portion 31 and an outer peripheral portion 32 surrounding the center portion 31 , and the thickness of the partition wall 14 in the center portion 31 is and the thickness of the partition wall 14 of the outer peripheral portion 32 are different. Specifically, the thickness T1 of the partition wall 14 located at the center portion 31 is different from the thickness T2 of the partition wall 14 located at the outer peripheral portion 32. Although the magnitude relationship between the partition wall thicknesses T1 and T2 is not particularly limited, for example, the partition wall thickness T1 is larger than the partition wall thickness T2. The ratio (T2/T1) of the partition wall thickness T2 to the partition wall thickness T1 is, for example, 0.6 or more and 0.9 or less, and may be 0.8 or less. According to such a relationship, the temperature can be raised to the central portion 31 in a short time after applying a voltage to the honeycomb structure portion 10. Note that in this specification, "orthogonal planes" may also include "orthogonal cross sections."

The central portion 31 and the outer peripheral portion 32 may be arranged adjacent to each other or may be arranged apart from each other. In the illustrated example, an intermediate portion 33 is disposed between the central portion 31 and the outer peripheral portion 32. The size relationship between the partition wall thicknesses T1 and T2 and the thickness T3 of the partition wall 14 located in the intermediate portion 33 is not particularly limited, but the partition wall thickness T1 is larger than the partition wall thickness T3, and the partition wall thickness T3 is larger than the partition wall thickness T2. It is preferable. The ratio (T3/T1) of the partition wall thickness T3 to the partition wall thickness T1 is, for example, 0.7 or more and 0.95 or less.

The number of cells 12 per unit area in a plane perpendicular to the extending direction of cells 12 is, for example, 50 cells/cm ² to 150 cells/cm ² , preferably 75 cells/cm ² to 150 cells/cm ² .

The cell pitch P of the cells 12 in a plane orthogonal to the extending direction of the cells 12 is, for example, 1.0 mm or more and 1.2 mm or less, preferably 1.06 mm or more and 1.16 mm or less, and more preferably 1.1 mm or more and 1.1 mm or less. .12mm or less. Here, as shown in FIG. 4, the cell pitch P is the distance between the central portions 14a of opposing substantially parallel partition walls 14 in the thickness direction.

The variation in the cell pitch P (the variation in the plane perpendicular to the direction in which the cells 12 extend) is, for example, 0.1 mm or less, preferably 0.07 mm or less, and more preferably 0.05 mm or less. By satisfying such cell pitch variations in the honeycomb structure in which the partition wall thicknesses T are different between the central part 31 and the outer peripheral part 32, the later-described variations in the thickness of the outer peripheral wall, degree of curvature, and roundness can be satisfactorily achieved. Thus, a honeycomb structure including an electrode layer with excellent thickness uniformity can be obtained. The variation in cell pitch can be determined by measuring the cell pitch at a total of 70 or more and 120 or less locations along each diameter direction at regular intervals using a CNC image measurement system (for example, Nikon's NEXIV series). It is the absolute value of the difference between the measured value and its average value. Here, "each diametrical direction" means two directions, the X direction and the Y direction, when the cross-sectional shape of the cell is square, and three directions (a pair of opposite directions) when the cross-sectional shape of the cell is hexagonal. (direction perpendicular to the partition wall).

For example, from the viewpoint of strength, the thickness of the outer peripheral wall 16 is preferably 0.1 mm or more, more preferably 0.15 mm or more, and still more preferably 0.2 mm or more. On the other hand, the thickness of the outer peripheral wall 16 is, for example, 1 mm or less, preferably 0.5 mm or less, more preferably 0.45 mm or less, and still more preferably 0.4 mm or less. The variation in the thickness of the outer peripheral wall (the variation in the plane perpendicular to the direction in which the cells 12 extend) is preferably 0.2 mm or less, more preferably 0.15 mm or less. In addition, the variation in the thickness of the outer peripheral wall is measured by measuring the thickness of the outer peripheral wall at 8 locations with a digital microscope at regular intervals (every 45 degrees at the central angle) and the average value. is the absolute value of the difference between

The degree of curvature in the extending direction of the cells 12 of the honeycomb structure 10 (outer peripheral wall 16) is preferably 1 mm or less, more preferably 0.9 mm or less. The roundness of the surface of the honeycomb structure 10 (outer peripheral wall 16) perpendicular to the extending direction of the cells 12 is preferably 1 mm or less, more preferably 0.9 mm or less. The degree of curvature and roundness can be obtained, for example, by optical gauge bending measurement (measurement using a laser displacement meter). Specifically, the outer circumferential shape is measured at three points in the length direction of the honeycomb structure 10: the upper end, the center, and the lower end, and the obtained measurement data is subjected to best-fit processing ( The degree of curvature and roundness (unit: mm) can be obtained by performing a process to minimize the amount of deviation from the reference value) and determining the absolute value of the difference from the reference value.

The pair of electrode layers 20, 20 are disposed to sandwich the central axis of the honeycomb structure 10, and are each formed in a band shape extending in the direction in which the cells 12 of the honeycomb structure 10 extend. Although not shown, each of the pair of electrode layers 20, 20 is provided with a metal terminal, one terminal may be connected to the positive pole of the power source, and the other terminal may be connected to the negative pole of the power source.

The thickness of the electrode layer 20 is, for example, 0.05 mm or more, preferably 0.1 mm or more and 0.5 mm or less. The variation in the thickness of the electrode layer 20 is preferably 0.092 mm or less, more preferably 0.046 mm or less. The variation in the thickness of the electrode layer (mm) is determined by measuring the thickness of the electrode layer in multiple cross sections perpendicular to the cell extending direction of the honeycomb structure, and measuring the size of the honeycomb structure provided with the electrode layer using a laser length measuring machine. This is the difference between the maximum value and minimum value of the measured values obtained by measuring four or more points on each cross section. According to the honeycomb structure according to the embodiment of the present invention, such uniformity in thickness is achieved, the energization heat generation property of the resulting honeycomb structure is ensured, uneven energization heat generation is suppressed, and the honeycomb structure is uniformly formed. Can be heated.

The variation in the thickness of the electrode layer 20 is preferably 35% or less, more preferably 32% or less, and even more preferably 30% or less. The lower limit of the variation in the thickness of the electrode layer 20 is not particularly limited, but may be, for example, 20% or more, or 25% or more. In addition, the variation (%) in the thickness of the electrode layer is determined by measuring the thickness of the electrode layer in multiple cross sections perpendicular to the extending direction of the cells of the honeycomb structure at four or more points in each cross section using an optical microscope. It can be calculated by dividing the absolute value of the difference between and these average values by the average value. According to the honeycomb structure according to the embodiment of the present invention, such uniformity in thickness is achieved, the energization heat generation property of the resulting honeycomb structure is ensured, uneven energization heat generation is suppressed, and the honeycomb structure is uniformly formed. Can be heated.

Although the formation range of the electrode layer 20 is not particularly limited, the pair of electrode layers 20, 20 each have a central angle θ of a circular arc in a plane orthogonal to the extending direction of the cell 12, for example, in a range of 80° or more and less than 180°. The angle is preferably between 95° and 105°.

The electrical resistivity of the honeycomb structure 10 at 25° C. is preferably 0.1 Ωcm to 200 Ωcm. The electrical resistivity of the electrode layer 20 at 25° C. is preferably 0.1 Ωcm to 100 Ωcm, more preferably 0.1 Ωcm to 50 Ωcm.

The honeycomb structure section 10 is typically made of a porous body. The honeycomb structure part 10 is formed of a material containing a ceramic raw material. Typically, it is formed from a material containing silicon carbide. Preferably, it is formed from a material containing a silicon-silicon carbide composite material as a main component (for example, containing 95% by mass or more). A silicon-silicon carbide composite material may be a material in which a plurality of silicon carbide particles are bonded together by metal silicon. When the honeycomb structure is formed of a silicon-silicon carbide composite material, the "mass of silicon carbide particles as aggregate" contained in the honeycomb structure and the "mass of silicon carbide particles as a binder" contained in the honeycomb structure The ratio of the "mass of silicon as a bonding material" contained in the honeycomb structure to the total of "the mass of silicon" is preferably 10% by mass to 40% by mass, and preferably 15% by mass to 35% by mass. It is even more preferable. With such a material, the above electrical resistivity can be satisfactorily achieved.

Typically, the volume resistivity of the electrode layer 20 is made lower than the volume resistivity of the honeycomb structure part 10. According to such a relationship, electricity tends to flow preferentially to the electrode layer 20, and when electricity is applied, electricity tends to spread in the extending direction and circumferential direction of the cell 12. The volume resistivity of the electrode layer 20 is preferably 1/10 or less, more preferably 1/20 or less, and even more preferably 1/30 or less of the volume resistivity of the honeycomb structure 10. On the other hand, if the difference in volume resistivity between the two becomes too large, there is a risk that current will be concentrated between the opposing ends of the electrode layers 20, causing uneven heat generation in the honeycomb structure section 10. The volume resistivity of the electrode layer 20 is preferably 1/200 or more, more preferably 1/150 or more, and even more preferably 1/100 or more of the volume resistivity of the honeycomb structure 10. Here, the volume resistivity of the electrode layer 20 is a value measured at 25° C. using a four-terminal method.

As the material of the electrode layer 20, for example, conductive ceramics, metal, or a composite material of metal and conductive ceramics (cermet) can be used. Examples of the metal include simple metals such as Cr, Fe, Co, Ni, Si, or Ti, or alloys containing at least one metal selected from the group consisting of these metals. Examples of conductive ceramics include silicon carbide (SiC); metal compounds such as metal silicides such as tantalum silicide (TaSi ₂ ) and chromium silicide (CrSi ₂ ). Specific examples of composite materials (cermets) of metal and conductive ceramics include composite materials of metal silicon and silicon carbide, and composite materials of the metal silicide, metal silicon, and silicon carbide. Further, as specific examples of composite materials (cermets) of metals and conductive ceramics, from the viewpoint of reducing thermal expansion, one or more of the above metals are combined with alumina, mullite, zirconia, cordierite, silicon nitride, Examples include composite materials to which one or more types of insulating ceramics such as aluminum nitride are added. Among these, for example, a composite material of metal silicide, metal silicon, and silicon carbide is preferably used from the viewpoint that it can be fired at the same time as the honeycomb structure part 10 and contributes to simplifying the manufacturing process.

When the honeycomb structure 30 is used as a catalyst carrier, a catalyst is supported on the partition walls 14, and it is possible to convert CO, _NOx , hydrocarbons, etc. in the exhaust gas passing through the cells 12 into harmless substances through a catalytic reaction. Become. The catalyst is preferably a noble metal (e.g. platinum, rhodium, palladium, ruthenium, indium, silver, gold), aluminum, nickel, zirconium, titanium, cerium, cobalt, manganese, zinc, copper, tin, iron, niobium, magnesium , lanthanum, samarium, bismuth, barium, and combinations thereof.

B. Manufacturing method The above honeycomb structure (honeycomb structure portion) is typically manufactured by extrusion molding a molding material containing a ceramic raw material to obtain a honeycomb molded body, and a honeycomb dried body obtained by drying the honeycomb molded body. and a firing step of firing to obtain a honeycomb structure (honeycomb structure portion).

As mentioned above, the molding material includes a ceramic raw material. Other raw materials that may be included in the molding material include, for example, a binder, a dispersion medium, and an additive.

In the above molding step, the molding material is extruded from a die in which slits corresponding to the partition walls of the honeycomb structure are formed to obtain a honeycomb molded body having partition walls defining cells that serve as fluid flow paths.

FIG. 5 is a cross-sectional view schematically showing a general configuration of each part of a die used in a method for manufacturing a honeycomb structure according to an embodiment of the present invention. In FIG. 5, arrow A is the extrusion direction of the molding material. The plate-shaped cap 50 is composed of a cap body 60 and a back plate 70.

The base body 60 has a molding material introduction part 65 in which a plurality of back holes 65a for introducing the molding material extending in the thickness direction are formed, and a slit 66a communicating with the back holes 65a. It has a molding section 66 for molding the molding material into a honeycomb molded body. The back plate 70 is formed with a plurality of communication holes 70a that communicate with the back hole 65a, and by introducing the molding material from the back plate 70 side and extruding it, the material passes through the communication holes 70a and passes through the back hole 65a of the introduction part 65. The molding material introduced from the molding material is passed through the slit 66a of the molding part 66 to obtain a honeycomb molded body. Although FIG. 5 shows the die body 60 and the back plate 70 separated for convenience, they may be in contact with each other during extrusion.

The slit 66a has a shape complementary to the partition wall 14 of the honeycomb structure part 10. Specifically, the honeycomb structure 10 shown in FIG. 1 has a large number of substantially regular hexagonal cells 12, and the partition walls 14 have a lattice pattern. A cap body is used in which slits in a shape complementary to the grid pattern (lattice pattern) are formed. It is preferable that the back holes 65a are provided corresponding to the positions where the slits 66a, such as a lattice pattern, intersect.

When obtaining the honeycomb structure 10 shown in FIGS. 1 to 3, the slit width of the slit 66a located at the center portion 61 of the molded portion 66 is larger than the slit width of the slit 66a located at the outer peripheral portion 62 of the molded portion 66. . Further, in the molding part 66, the slit width of the slit 66a located in the intermediate part 63 between the central part 61 and the outer peripheral part 62 is smaller than the slit width of the slit 66a located in the central part 61, and It is larger than the slit width of the located slit 66a.

The diameters of the plurality of communication holes 70a of the back plate 70 change stepwise within the plane. Specifically, the back plate 70 has a first region 71 in which communication holes 70a having a relatively large diameter are arranged side by side, and a second region 72 in which communication holes 70a having a relatively small hole diameter are arranged in parallel. . In the illustrated example, the first region 71 is formed on the outer periphery of the back plate 70 and is arranged such that at least a portion thereof faces the outer periphery 62 of the molded portion 66 . The second region 72 is formed in the center of the back plate 70 and is arranged such that at least a portion thereof faces the center portion 61 of the molded portion 66 . Further, in the back plate 70, the diameter of the communication holes 70a arranged in parallel in the third region 73 between the first region 71 and the second region 72 is, for example, larger than the diameter of the communication holes 70a in the first region 71. It is small and larger than the hole diameter of the communication hole 70a of the second region 72. The third region 73 is arranged such that at least a portion thereof faces the intermediate portion 63 of the molded portion 66. The ratio (D2/D1) of the pore diameter D2 of the second region 72 to the pore diameter D1 of the first region 71 is, for example, 0.70 or more and 0.94 or less, preferably 0.85 or less, and more preferably 0. 80 or less. Further, the ratio (D3/D1) of the pore diameter D of the third region 73 to the pore diameter D1 of the first region 71 is, for example, 0.75 or more and 1 or less.

The diameters of the plurality of communication holes 70a formed in the first region 71 are substantially the same, and the diameters of the plurality of communication holes 70a formed in the second region 72 are substantially the same. Further, the diameters of the plurality of communication holes 70a formed in the third region 73 are approximately the same. Here, "substantially the same" means that the diameters of the plurality of communication holes are within a range of ±5% of the average value. Further, the hole diameter refers to the longest diameter of the communication hole in a cross-sectional shape parallel to the surface of the back plate. For example, in the case of a circle, it is the diameter, in the case of an ellipse, it is the major axis, and in the case of a polygon, it is the diagonal.

When the molding material is extruded at an extrusion speed of 10 mm/sec to 40 mm/sec for 3 seconds to 25 seconds, the variation in the amount of extrusion within the plane of the molding part 66 of the die body 60 is preferably 2 mm or less, more preferably It is 1 mm or less. FIG. 6 shows an example of the exit of the mouthpiece body 60 (molding part 66) when the molding material is extruded from the mouthpiece body 60 at a predetermined speed for a predetermined time without using the back plate 70. As shown in FIG. 6, the amount of molding material M extruded from the molding part 66 (the end surface portion of the honeycomb molded body) is larger in the center part 61 where the slit width is large, and is less in the outer peripheral part 62 where the slit width is small. There is a tendency to The variation in extrusion amount is the difference between the extrusion amount at the most extruded portion and the extrusion amount at the least extruded portion, and is indicated by arrow B in the example shown in FIG. By using the back plate 70, it is possible to equalize the amount of extrusion within the plane of the molding part 66 and suppress variations. Specifically, as shown in FIG. 7, the extrusion amount of the molding material M extruded from the molding part 66 can be made comparable between the central part 61 and the outer peripheral part 62.

A honeycomb structure obtained by suppressing variations in extrusion amount can satisfactorily achieve the above-mentioned variations in cell pitch, and can satisfactorily achieve variations in the thickness of the outer peripheral wall, degree of bending, and roundness. Furthermore, by suppressing variations in the extrusion amount, the yield can be significantly improved.

In another embodiment, after extruding the molding material from the die body without using a back plate and checking for variations in the amount of extrusion, the first region is formed corresponding to a location where the amount of extrusion is small, and the extrusion The shape of the honeycomb molded body is adjusted using the back plate in which the second region is formed corresponding to the location where the amount is large.

In yet another embodiment, for example, for the purpose of obtaining a honeycomb formed body bent in a predetermined direction, the above-mentioned The shape of the honeycomb formed body is adjusted using a back plate in which the first region is formed and the second region is formed in other parts.

The honeycomb formed body is dried to obtain a dried honeycomb body. Examples of methods for drying the honeycomb formed body include hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, and freeze drying. These may be used alone or in combination of two or more. Among these, it is possible to dry the entire honeycomb molded body quickly and uniformly without cracking, and after drying a certain amount of moisture using electromagnetic heating method, the remaining moisture is removed using external heating method. Preferably, it is dried. As the electromagnetic wave heating method, dielectric heating drying is preferable, and as the external heating method, hot air drying is preferable. The drying temperature is preferably 50°C to 120°C.

The dried honeycomb body is fired to obtain a honeycomb structure (honeycomb structure portion). Any suitable conditions may be employed as the firing conditions. The firing temperature is, for example, 1350°C to 1500°C. The firing time is, for example, 20 to 80 hours. Firing may be performed continuously or in multiple stages at different temperatures. In addition, when baking is performed in multiple stages, the above-mentioned baking time is the total baking time of each stage.

The dried honeycomb body may be calcined before the dried honeycomb body is subjected to the firing treatment. The calcination temperature can be determined, for example, depending on the combustion temperature of organic matter contained in the dried honeycomb body. The calcination temperature is, for example, 200°C to 1000°C. The calcination time is, for example, 10 hours to 100 hours. Note that calcination and firing may be performed continuously. Specifically, calcination may be performed during the heating process of calcination.

The electrode layer is typically formed by applying an electrode layer forming material and firing a coating layer obtained. The electrode layer forming material may be applied at any appropriate timing. Typically, the electrode layer forming material is applied to the dried honeycomb body. Note that the electrode layer forming material may be applied to the honeycomb fired body (during the above firing process). As a method for applying the electrode layer forming material, a printing method is preferably employed. For example, a plate having openings formed on the side surface of the dried honeycomb body is placed, and a paste-like electrode layer forming material is applied from above the plate by pressing with a squeegee. According to such a method, an electrode layer can be satisfactorily formed on the coated surface (the curved side surface). In addition, the obtained honeycomb structure can satisfactorily achieve the above-mentioned cell pitch variation, and the above-mentioned outer peripheral wall thickness variation, bending degree, and roundness. It is possible to form an electrode layer with high uniformity and excellent thickness uniformity.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples.

[Example 1]
(Base body)
A cap body (cap body 60) as shown in FIG. 5 was prepared. Specifically, the thickness of the introduction part in which the back holes were formed was 19 mm to 21 mm ± 0.1 mm, the diameter of the back holes was 0.85 mm to 0.90 mm ± 0.1 mm, and the pitch of the back holes was 1.18 mm. ~1.20mm±0.050mm. Further, the thickness of the molded part in which the slits were formed was 2.20 mm ± 0.1 mm, the width of the slit in the center was 0.330 mm ± 0.010 mm, and the width of the slit in the outer peripheral part was 0.280 mm ± 0.1 mm. 010 mm, and the width of the slit in the middle part was 0.310 mm±0.010 mm, and lattice-shaped slits were formed such that the back holes were located at the intersections of the lattice shape. The back hole was formed by drilling, and the slit was formed by grinding.

(back plate)
A back plate (back plate 70) as shown in FIG. 5 was prepared. Specifically, a mesh-like back plate was prepared by drilling a large number of flow holes in a plate-shaped member (back plate plate member) with a circular outer circumference and a thickness of 2.00 mm ± 0.17 mm. did. The diameter of the flow holes in the central part (circular area) including the center is 0.60 mm, the diameter of the flow holes in the middle part (doughnut-shaped area) is 0.65 mm, and the diameter of the flow holes in the outer periphery (doughnut-shaped area) is 0.60 mm. The hole diameter was 0.85 mm.

(cap)
Next, a back plate was attached to the introduction part side of the obtained base body by pin fitting to obtain a base.

(molding material)
Silicon carbide powder passed through a sieve and metal silicon powder were mixed at a mass ratio of 70:30 to obtain a raw material powder. A binder, additives, and water were added to the obtained raw material powder, and these were mixed to obtain a wet powder (mixture). The obtained wet powder was kneaded to obtain clay.

(honeycomb molded body)
The clay was extruded using an extrusion molding machine equipped with the die at an extrusion speed of 20 mm/sec to obtain a cylindrical honeycomb molded body with a length of 180 mm. Thereafter, the formed honeycomb body was dried to obtain a dried honeycomb body.

(Electrode layer forming material)
Metallic silicon (Si) powder with an average particle diameter of 6 μm, silicon carbide (SiC) powder with an average particle diameter of 35 μm, methyl cellulose, glycerin, and water were mixed using a rotation-revolution stirrer to prepare an electrode layer forming material. The Si powder and the SiC powder were mixed in a volume ratio of Si powder:SiC powder=40:60. Further, when the total of Si powder and SiC powder was 100 parts by mass, the blending amounts were 0.5 parts by mass of methylcellulose, 10 parts by mass of glycerin, and 38 parts by mass of water.

(electrode layer)
The electrode layer forming material was applied to the side surface of the dried honeycomb body by a printing method so that an electrode layer as shown in FIG. 1 was obtained (center angle of one electrode layer was 90°). Specifically, a plate having openings formed therein was placed on the outer peripheral surface of the dried honeycomb body, and the electrode layer forming material was applied from above the plate by pressing with a squeegee.

(Firing)
After drying the electrode layer forming material applied to the dried honeycomb body, it was fired in an argon atmosphere and then in an air atmosphere to obtain a honeycomb structure.

[Example 2]
A honeycomb molded body and a honeycomb structure were obtained in the same manner as in Example 1 except that back plate A shown below was used as the back plate.
(Preparation of back plate A)
A communication hole was formed in the plate member for the back plate by drilling. In the semicircular area on the left half, the diameter of the communication hole in the center is 0.70 mm, the diameter of the communication hole in the middle is 0.75 mm, the diameter of the communication hole in the outer periphery is 0.85 mm, and the diameter of the communication hole in the right half is 0.70 mm. In the semicircular area of , the diameter of the flow hole in the center was 0.60 mm, the diameter of the flow hole in the middle was 0.65 mm, and the diameter of the flow hole in the outer periphery was 0.75 mm. A back plate was produced in the same manner as in Example 1.

[Example 3]
A honeycomb molded body and a honeycomb structure were obtained in the same manner as in Example 1 except that back plate B shown below was used as the back plate.
(Preparation of back plate B)
A communication hole was formed in the plate member for the back plate by drilling. Five areas are set radially outward from the center, and the diameter of the communication hole in the innermost area (circular area) including the center is 0.60 mm, and the second, third, and fourth areas from the inside The hole diameters of the flow holes in the fifth region (all doughnut-shaped regions) were set to gradually increase outward to 0.65 mm, 0.70 mm, 0.75 mm, and 0.80 mm, respectively. A back plate was produced in the same manner as in Example 1 except for this.

[Comparative example 1]
A honeycomb molded body and a honeycomb structure were obtained in the same manner as in Example 1 except that a back plate was not used.

[Comparative example 2]
A honeycomb molded body and a honeycomb structure were obtained in the same manner as in Example 1 except that a back plate C shown below was used as the back plate.
(Preparation of back plate C)
A communication hole was formed in the plate member for the back plate by drilling. Same as Example 1 except that the flow holes with a hole diameter of 0.75 mm were formed without substantially changing the hole diameters of the large number of flow holes formed in the plane (in the center, middle, and outer periphery). A back plate was prepared.

<Evaluation>
For Examples and Comparative Examples, variations in extrusion amount, degree of bending, roundness, variation in cell pitch, variation in outer peripheral wall thickness, variation in electrode layer thickness, and heat generation unevenness were evaluated. The evaluation method is as follows. The evaluation results are summarized in Table 1.

1. Variation in extrusion amount The above clay was extruded using an extrusion molding machine equipped with the above die at an extrusion speed of 20 mm/sec until the extrusion length reached 5.0 cm to 10.0 cm, and the extruded portion was cut to measure. A molded body for use was obtained. The obtained measurement molded body was cut in half lengthwise along the length direction, and as shown in FIG. The height difference and convexity) were measured.
2. Curvature and Roundness The curvature and roundness of the obtained honeycomb structure were evaluated using a laser displacement meter (laser sensor, manufactured by Micro-Epsilon). Specifically, three of the lengthwise upper end (6 mm from the tip), lower end (6 mm from the end), and center (midway between the upper and lower ends) of the obtained dried honeycomb body are used. The outer circumferential shape of each point was measured. The obtained measurement data was subjected to best-fit processing with respect to the reference outer peripheral shape, and the absolute value of the difference from the reference value was determined.
Note that the roundness and degree of curvature of the honeycomb fired body (honeycomb structure part) are approximately the same as the degree of circularity and degree of curvature of the dried honeycomb body (specifically, the degree of circularity and degree of curvature of the dried honeycomb body) (at most, it was about 0.05 mm larger).
3. Variation in Cell Pitch The cell pitch of the obtained honeycomb structure was measured using a CNC image measurement system (NEXIV, manufactured by Nikon Corporation), and the variation in cell pitch was evaluated. Specifically, measurements were taken at 71 locations in each of three directions (directions perpendicular to a pair of opposing partition walls) of a cell with a hexagonal cross-sectional shape, and the difference between the obtained measured values and the average value was calculated. The absolute value of was calculated.
4. Variation in the thickness of the outer peripheral wall For the obtained honeycomb structure, the thickness of the outer peripheral wall was measured at 8 points at 45° central angle intervals using a digital microscope (manufactured by Sanko Co., Ltd., "Dino-Lite"). The absolute value of the difference between the measured value and the average value was determined, and the variation in the thickness of the outer peripheral wall was evaluated.
5. Variation in the thickness of the electrode layer The thickness of the electrode layer at multiple cross sections (5 locations at predetermined intervals, including the tip and end) perpendicular to the extending direction of the cells of the obtained honeycomb structure was measured by laser length measurement. Measurements were made at six points (30 points in total) at equal intervals in the circumferential direction of each cross section using a machine, and the difference between the maximum and minimum values of the obtained measurement values was determined to evaluate the variation in the thickness of the electrode layer.
6. Uneven heat generation After applying 1.5 kW of direct current to four locations at predetermined intervals (in the length direction) of the obtained honeycomb structure for 20 seconds, the temperature of the honeycomb structure was measured using a thermo camera. The heat generation unevenness was evaluated by measuring from the length direction and calculating the difference between the temperature of the highest temperature part and the lowest temperature part.

The present invention is not limited to the above embodiments, and various modifications are possible. For example, it can be replaced with a configuration that is substantially the same as the configuration shown in the above embodiment, a configuration that has the same effect, or a configuration that can achieve the same purpose.

The honeycomb structure of the embodiment of the present invention can be suitably used for treating (purifying) exhaust gas of an internal combustion engine.

DESCRIPTION OF SYMBOLS 10 honeycomb structure part, 12 cell, 14 partition wall, 16 outer peripheral wall, 20 electrode layer, 30 honeycomb structure body, 31 center part, 32 outer peripheral part, 33 intermediate part, 50 mouthpiece, 60 mouthpiece body, 65 introduction part, 65a back hole , 66 molding section, 66a slit, 70 back plate, 70a communication hole.

Claims (11)

A honeycomb structure comprising: a forming step for obtaining a honeycomb formed body by extrusion molding a forming material containing a ceramic raw material; and a firing step for obtaining a honeycomb structure by firing a dried honeycomb body obtained by drying the honeycomb formed body. A manufacturing method,
The honeycomb structure includes a honeycomb structure having an outer circumferential wall and a partition wall disposed inside the outer circumferential wall, and a pair of electrode layers disposed on a side surface of the honeycomb structure,
The honeycomb structure has a center portion and an outer peripheral portion surrounding the center portion in a plane perpendicular to the extending direction of the honeycomb structure, and the thickness of the partition wall in the center portion and the thickness of the partition wall in the outer peripheral portion are the same. Unlike,
In the forming step, an introduction part for the molding material is formed with a plurality of back holes extending in the thickness direction, and a slit communicating with the back holes is formed, and the molding material that has passed through the introduction part is transferred to the honeycomb molded body. In a state where a back plate in which a plurality of communication holes communicating with the back hole are formed is disposed on the introduction part side of the plate-shaped cap body having a molding part to be molded, the molding is performed from the back plate side. Including the step of introducing and extruding the material,
The pore diameters of the plurality of communication holes of the back plate change stepwise in a plane, and a first region where communication holes with relatively large diameters are arranged side by side and a first region where communication holes with relatively small hole diameters are arranged side by side. and a second region,
A method for manufacturing a honeycomb structure. According to claim 1, when the molding material is extruded at an extrusion speed of 10 mm/sec to 40 mm/sec for 3 seconds to 25 seconds, a variation in the amount of extrusion within the plane of the molding part of the die body is 2 mm or less. A method for manufacturing a honeycomb structure. 1 or 2, wherein slits having different slit widths are formed in the molding part, and the slit width of the slit located in the center of the molding part is larger than the slit width of the slit located in the outer peripheral part of the molding part. 2. The method for manufacturing a honeycomb structure according to 2. The method for manufacturing a honeycomb structure according to claim 3, wherein the first region is located at an outer peripheral portion of the back plate, and the second region is located at a central portion of the back plate. A method for adjusting the shape of a honeycomb formed body having an outer peripheral wall and partition walls arranged inside the outer peripheral wall, the method comprising:
The honeycomb formed body has a center portion and an outer peripheral portion surrounding the center portion in a plane perpendicular to the extending direction of the honeycomb formed body, and the thickness of the partition wall in the center portion and the thickness of the partition wall in the outer peripheral portion are Unlike,
The shape adjustment method includes a molding material introduction part in which a plurality of back holes extending in the thickness direction are formed, and a slit communicating with the back holes, and the molding material that has passed through the introduction part is transferred to the honeycomb molded body. In a state where a back plate in which a plurality of communication holes communicating with the back hole are formed is disposed on the introduction part side of the plate-shaped cap body having a molding part to be molded, the molding is performed from the back plate side. Including the step of introducing and extruding the material,
The pore diameters of the plurality of communication holes of the back plate change stepwise in a plane, and a first region where communication holes with relatively large diameters are arranged side by side and a first region where communication holes with relatively small hole diameters are arranged side by side. and a second region,
A method for adjusting the shape of a honeycomb molded body. a honeycomb structure having a partition wall that extends from a first end surface to a second end surface and defines a plurality of cells that serve as fluid flow paths; and an outer peripheral wall located on the outer periphery;
a pair of electrode layers disposed on the side surfaces of the honeycomb structure,
The honeycomb structure has a central portion and an outer peripheral portion surrounding the central portion in a plane perpendicular to the extending direction of the cells, and the thickness of the partition wall in the central portion and the thickness of the partition wall in the outer peripheral portion are Unlike,
The cell pitch of the cells in a plane perpendicular to the extending direction of the cells of the honeycomb structure is 1.0 mm or more and 1.2 mm or less, and the variation in the cell pitch is 0.1 mm or less.
honeycomb structure. 6. The thickness of the outer peripheral wall in a plane perpendicular to the extending direction of the cells of the honeycomb structure is 0.1 mm or more and 0.5 mm or less, and the variation in the thickness of the outer peripheral wall is 0.2 mm or less. Honeycomb structure described in. The honeycomb structure according to claim 6 or 7, wherein the degree of curvature in the extending direction of the cells of the honeycomb structure is 1 mm or less. The honeycomb structure according to any one of claims 6 to 8, wherein the circularity of a surface of the honeycomb structure section perpendicular to the direction in which the cells extend is 1 mm or less. The honeycomb structure according to any one of claims 6 to 9, wherein the electrode layer has a thickness of 0.1 mm or more and 0.5 mm or less, and a variation in the thickness of the electrode layer is 0.092 mm or less. The honeycomb structure according to any one of claims 6 to 10, wherein the ratio of the thickness of the partition wall in the outer peripheral part to the thickness of the partition wall in the central part of the honeycomb structure part is 0.6 or more and 0.9 or less. body.

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