Honeycomb structure and manufacturing method thereof

Abstract

To provide a honeycomb structure capable of reducing the risk of cracking in the honeycomb structure when heated and a method for producing the same.SOLUTION: There is provided a honeycomb structure 1 which has a honeycomb structure part 2 having an outer peripheral wall 20 and a partition wall 21 which is arranged inside the outer peripheral wall 20 and dividedly forms a plurality of cells 21a forming a flow channel extending from one end face to the other end face and further has a plurality of slits 3 extending radially inwardly from an outer peripheral surface of the honeycomb structure 1 and extending in the extension direction of the cells 21a and a filler 4 filled in the plurality of slits 3, wherein when the difference between a width Y of the filler 4 and a width X of the slit 3 represented by the following expression (1) is determined for each slit 3, the difference between a maximum value A of the difference and a minimum value B of the difference represented by the following expression (2) is 0.4 mm or less. In the expression (1), X represents the width of the slit 3 on the outer peripheral surface of the honeycomb structure 1 and Y represents the width of filler 4 when looking at the filler 4 from the outside in the radial direction. Expression (1) Y-X. Expression (2) A-B.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a honeycomb structure and a method for manufacturing the same. [Background technology]

[0002] Generally, electrically heated catalysts (EHCs) are known in which electrodes are placed on a honeycomb structure made of conductive ceramics, and the honeycomb structure itself is heated by passing electricity through it, thereby raising the temperature of the catalyst supported on the honeycomb structure to its activation temperature before the engine (internal combustion engine) is started, with the aim of purifying exhaust gases emitted when the engine is cold immediately after starting.

[0003] Patent Document 1 listed below discloses a honeycomb structure in which one or more slits opening to the side surface are formed in a honeycomb structure portion in order to improve the thermal shock resistance of the honeycomb structure. It also proposes filling at least one slit with a filler material to prevent gas passing through the honeycomb structure from leaking out of the slit to the outer periphery of the honeycomb structure while maintaining the thermal shock resistance. Patent Document 1 discloses a method of using a syringe or a spatula to fill the slit with the filler material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-174011 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, when filling slits with filler, the outer peripheral surface of the honeycomb structure part where the slits are formed is masked, and then the filler is filled into the slits. At this time, the masking is performed so as to exclude the slits to be filled with the filler. In other words, unmasked areas (masking slits) corresponding to the slits are formed on the outer peripheral surface of the honeycomb structure part.

[0006] As a result of the inventors' investigations, it was found that the method of masking can cause variations in the width of the filler, which in turn causes variations in the stress relaxation performance in the circumferential direction of the honeycomb structure, and may be a factor in the generation of cracks in the honeycomb structure when the honeycomb structure is heated.

[0007] The present invention has been made to solve the above-mentioned problems, and one of its objects is to provide a honeycomb structure and a method for manufacturing the same that can reduce the risk of cracks occurring in the honeycomb structure when heated. [Means for solving the problem]

[0008] In one embodiment, the honeycomb structure according to the present invention is a honeycomb structure comprising a honeycomb structure portion having an outer peripheral wall and partition walls arranged inside the outer peripheral wall and defining a plurality of cells that form flow paths extending from one end face to the other end face, and further comprising a plurality of slits extending radially inward from the outer peripheral surface of the honeycomb structure and extending in the extension direction of the cells, and a filler material filled in the plurality of slits, wherein when the difference between the width Y of the filler and the width X of the slit, as shown in the following formula (1), is determined for each slit, the difference between the maximum difference A and the minimum difference B, as shown in the following formula (2), is 0.4 mm or less. (YX) (1) (AB) (2) In formula (1), X represents the width of the slit on the outer peripheral surface of the honeycomb structure, and Y represents the width of the filler when viewed from the outside in the radial direction of the honeycomb structure.

[0009] The method for manufacturing a honeycomb structure according to the present invention includes a masking step of masking the outer surface of a honeycomb structure body, in which the honeycomb structure body has a honeycomb structure portion having an outer peripheral wall and partition walls arranged inside the outer peripheral wall and defining a plurality of cells that form flow paths extending from one end face to the other end face; a slit forming step of processing the honeycomb structure body from the radially outer side after the masking step to form a plurality of slits in the honeycomb structure body that extend radially inward from the outer peripheral surface of the honeycomb structure body and in the extension direction of the cells; a filling step of filling the plurality of slits with a filler material after the slit forming step; and a removal step of removing the masking after filling the filler material. [Effects of the Invention]

[0010] According to one embodiment of the honeycomb structure and the manufacturing method thereof of the present invention, it is possible to reduce the risk of cracks occurring in the honeycomb structure when heated. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view showing a honeycomb structure according to an embodiment of the present invention; [Figure 2] FIG. 2 is an explanatory view showing details of the filler in FIG. [Figure 3] 1A to 1C are explanatory views showing a method for manufacturing a honeycomb structure according to an embodiment of the present invention. [Figure 4] FIG. 10 is an explanatory diagram showing a strength test. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to each embodiment, and the components can be modified and embodied without departing from the spirit of the present invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in each embodiment. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components of different embodiments may be appropriately combined.

[0013] 1 is a perspective view showing a honeycomb structure 1 according to an embodiment of the present invention. The honeycomb structure 1 shown in FIG. 1 includes a honeycomb structure portion 2, a plurality of slits 3, a filler 4, and a pair of electrode layers 5.

[0014] The honeycomb structure portion 2 is a columnar member made of ceramics, and has an outer peripheral wall 20 and partition walls 21 arranged inside the outer peripheral wall 20 and defining a plurality of cells 21a that form flow paths extending from one end face to the other end face.

[0015] The outer shape of the honeycomb structure part 2 is not particularly limited as long as it is columnar, and may be other shapes such as a columnar shape with circular end faces (cylindrical shape), a columnar shape with oval end faces, or a columnar shape with polygonal end faces (quadrangle, pentagon, hexagon, heptagon, octagon, etc.). A columnar shape can be understood as a three-dimensional shape having a thickness in the extension direction of the cells 21a (axial direction of the honeycomb structure 1). The ratio (aspect ratio) of the axial length of the honeycomb structure part 2 to the diameter or width of the end face of the honeycomb structure part 2 is arbitrary. The columnar shape may also include a shape (flat shape) in which the axial length of the honeycomb structure part 2 is shorter than the diameter or width of the end face.

[0016] The size of the honeycomb structure portion 2 is set to an end surface area of ​​2000 to 20000 mm for the reason of increasing heat resistance (suppressing cracks in the circumferential direction of the outer peripheral wall 20). 2 It is preferable that the thickness is 5000 to 15000 mm 2 It is more preferable that:

[0017] Although there is no limitation on the shape of the cells 21a in a cross section perpendicular to the extension direction of the cells 21a, a square, a hexagon, an octagon, or a combination thereof is preferable. Among these, a square and a hexagon are preferable. By using such a cell shape, the pressure loss when exhaust gas flows through the honeycomb structure 1 is reduced, and the purification performance of the catalyst is improved.

[0018] The thickness of the partition walls 21 that define the cells 21a is preferably 0.07 to 0.3 mm, and more preferably 0.1 to 0.2 mm. When the thickness of the partition walls 21 is 0.1 mm or more, it is possible to prevent a decrease in the strength of the honeycomb structure 1. When the thickness of the partition walls 21 is 0.3 mm or less, it is possible to prevent an increase in pressure loss when exhaust gas flows through the honeycomb structure 1 when the honeycomb structure 1 is used as a catalyst carrier and a catalyst is loaded thereon. In the present invention, the thickness of the partition walls 21 is defined as the length of a portion that passes through the partition walls 21, of a line segment that connects the centers of gravity of adjacent cells 21a in a cross section perpendicular to the extension direction of the cells 21a.

[0019] The honeycomb structure portion 2 has a cell density of 40 to 150 cells / cm in a cross section perpendicular to the extending direction of the cells 21a. 2 It is preferable that the number of cells is 70 to 100. 2 By setting the cell density in this range, it is possible to increase the purification performance of the catalyst while minimizing the pressure loss when exhaust gas flows through it. 2 If the cell density is 150 cells / cm or more, a sufficient catalyst carrying area is ensured. 2 If the cell density is less than this value, when the honeycomb structure part 2 is used as a catalyst carrier to support a catalyst, excessive pressure loss during the flow of exhaust gas is suppressed. The cell density is a value obtained by dividing the number of cells by the area of ​​one end face part of the honeycomb structure part 2 excluding the outer wall 20 part.

[0020] Providing the outer peripheral wall 20 of the honeycomb structure portion 2 is useful from the viewpoint of ensuring the structural strength of the honeycomb structure portion 2 and suppressing leakage of the fluid flowing through the cells 21a from the outer peripheral wall 20. Specifically, the thickness of the outer peripheral wall 20 is preferably 0.05 mm or more, more preferably 0.10 mm or more, and even more preferably 0.15 mm or more. However, if the outer peripheral wall 20 is made too thick, the strength becomes too high, which disrupts the strength balance with the partition walls 21 and reduces thermal shock resistance. Therefore, the thickness of the outer peripheral wall 20 is preferably 1.0 mm or less, more preferably 0.7 mm or less, and even more preferably 0.5 mm or less. Here, the thickness of the outer peripheral wall 20 is defined as the thickness in the direction normal to the tangent of the outer peripheral wall 20 at the measurement point when the portion of the outer peripheral wall 20 where the thickness is to be measured is observed in a cross section perpendicular to the extension direction of the cells 21a.

[0021] The honeycomb structure part 2 is preferably made of ceramics and has electrical conductivity. There are no particular restrictions on the volume resistivity of the honeycomb structure part 2 as long as it can generate heat by Joule heat when current is applied, but it is preferably 0.1 to 200 Ωcm, and more preferably 1 to 200 Ωcm. In the present invention, the volume resistivity of the honeycomb structure part 2 is a value measured at 25°C by a four-terminal method.

[0022] The material of the honeycomb structure member 2 is not limited, but can be selected from the group consisting of oxide ceramics such as alumina, mullite, zirconia, and cordierite, and non-oxide ceramics such as silicon carbide, silicon nitride, and aluminum nitride. Silicon carbide-metal silicon composites and silicon carbide / graphite composites can also be used. Among these, from the viewpoint of achieving both heat resistance and electrical conductivity, it is preferable that the material of the honeycomb structure member 2 contains a silicon-silicon carbide composite or a ceramic containing silicon carbide as the main component. When the material of the honeycomb structure member 2 is said to contain a silicon-silicon carbide composite as the main component, it means that the honeycomb structure member 2 contains 90 mass% or more of the silicon-silicon carbide composite (total mass) of the entire honeycomb structure member 2. Here, the silicon-silicon carbide composite material contains silicon carbide particles as aggregate and silicon as a binder that bonds the silicon carbide particles, and it is preferable that a plurality of silicon carbide particles are bonded by the silicon so as to form pores between the silicon carbide particles. When the material of the honeycomb structure part 2 is said to be mainly composed of silicon carbide, it means that the honeycomb structure part 2 contains silicon carbide (total mass) in an amount of 90 mass% or more of the entire material.

[0023] When the honeycomb structure part 2 contains a silicon-silicon carbide composite material, the ratio of the "mass of silicon as a binder" contained in the honeycomb structure part 2 to the sum of the "mass of silicon carbide particles as aggregate" contained in the honeycomb structure part 2 and the "mass of silicon as a binder" contained in the honeycomb structure part 2 is preferably 10 to 40 mass%, and more preferably 15 to 35 mass%.

[0024] The partition walls 21 may be porous. When the partition walls 21 are porous, the porosity of the partition walls 21 is preferably 35 to 60%, and more preferably 35 to 45%. The porosity is a value measured by a mercury porosimeter.

[0025] The average pore diameter of the partition walls 21 of the honeycomb structure portion 2 is preferably 2 to 15 μm, and more preferably 4 to 8 μm. The average pore diameter is a value measured by a mercury porosimeter.

[0026] The multiple slits 3 extend radially inward from the outer peripheral surface of the honeycomb structure 1 and in the extension direction of the cells 21a. The slits 3 extend in the extension direction of the cells 21a from one end face to the other end face of the honeycomb structure section 2. The depth of the slits 3 is preferably 60% or less of the radius of the honeycomb structure section 2 in a cross section perpendicular to the extension direction of the cells 21a, and more preferably 0.5% to 25%. The width of the slits 3 may be 0.2 mm or more to 2.0 mm or less, and more preferably 0.2 mm or more to 1.0 mm or less. The depth of the slits 3 may be understood as the distance from the outer peripheral surface of the outer wall 20 to the tip of the slits 3.

[0027] The outer peripheral surface of the outer wall 20 constitutes at least a part of the outer peripheral surface of the honeycomb structure 1. More specifically, at a position where the outer peripheral surface of the outer wall 20 is exposed, i.e., at a position where the outer peripheral surface of the outer wall 20 is not covered with the electrode layer 5, the outer peripheral surface of the outer wall 20 constitutes the outer peripheral surface of the honeycomb structure 1. On the other hand, at a position where a pair of electrode layers 5 is provided, the outer peripheral surfaces of the pair of electrode layers 5 constitute the outer peripheral surface of the honeycomb structure 1. From another perspective, when observing the appearance of the honeycomb structure 1, the surface where the multiple slits 3 appear may be considered as the outer peripheral surface of the honeycomb structure 1. It may be understood that the outer peripheral surface of the honeycomb structure 1 does not include the end faces of the honeycomb structure portion 2 where the cells 21a open.

[0028] The filler 4 is filled in the slits 3. The filler 4 is preferably filled in at least a part of the space of the slits 3. The filler 4 is preferably filled in 50% or more of the space of the slits 3, and more preferably filled in the entire space of the slits 3. In the embodiment shown in FIG. 1 , the filler 4 is filled in the entire space of the slits 3, forming flat surfaces integral with both end faces of the honeycomb structure section 2 and forming curved surfaces integral with the outer peripheral surface of the honeycomb structure 1. However, the filler 4 may be filled up to a position axially inward from the end faces of the honeycomb structure section 2, or may be filled up to a position radially inward from the outer peripheral surface of the honeycomb structure 1.

[0029] When the main component of the honeycomb structure portion 2 is silicon carbide or a metal silicon-silicon carbide composite, the filler 4 preferably contains 20 mass % or more, and more preferably 20 to 70 mass % of silicon carbide. This allows the thermal expansion coefficient of the filler 4 to be close to that of the honeycomb structure portion 2, thereby improving the thermal shock resistance of the honeycomb structure portion 2. The filler 4 may contain 30 mass % or more of silica, alumina, etc.

[0030] The pair of electrode layers 5 are provided on the outer surface of the outer wall 20, sandwiching the central axis of the honeycomb structure section 2, so as to extend in a strip shape in the extension direction of the cells 21a. Although not shown, electrode terminals can be provided on the electrode layers 5. A voltage can be applied to the honeycomb structure section 2 through these electrode terminals and electrode layers 5, causing the honeycomb structure section 2 to generate heat.

[0031] Each of the pair of electrode layers 5 has first and second partial electrode layers 51, 52 separated by a slit 3. That is, at the position where the electrode layer 5 is provided, the slit 3 extends radially inward from the electrode layer 5 and opens at the outer circumferential surface of the electrode layer 5. The filler material 4 may also be filled in the slit 3 between the first and second partial electrode layers 51, 52.

[0032] From the viewpoint of making it easier for electricity to flow through the electrode layers 5 , the volume resistivity of the electrode layers 5 is preferably 1 / 200 or more and 1 / 10 or less of the electrical resistivity of the honeycomb structure portion 2 .

[0033] The material of the electrode layer 5 can be a conductive ceramic, a metal, or a composite material (cermet) of a metal and a conductive ceramic. Examples of the metal include a single metal such as Cr, Fe, Co, Ni, Si, or Ti, or an alloy containing at least one metal selected from the group consisting of these metals. Examples of the conductive ceramic include, but are not limited to, silicon carbide (SiC), and metal compounds such as metal silicides such as tantalum silicide (TaSi2) and chromium silicide (CrSi2).

[0034] In a manufacturing method of the honeycomb structure 1 having the electrode layers 5, first, an electrode layer forming raw material containing ceramic raw materials is applied to the side surface of the dried honeycomb body, and then dried to form a pair of unfired electrode layers extending in a band shape in the extension direction of the cells 21a on the outer surface of the peripheral wall 20, sandwiching the central axis of the dried honeycomb body, thereby producing a dried honeycomb body with unfired electrode layers. Next, the dried honeycomb body with the unfired electrode layers is fired to produce a fired honeycomb body having the pair of electrode layers 5. In this way, the honeycomb structure 1 having the electrode layers 5 is obtained. Note that the pair of electrode layers 5 are not essential components, and the honeycomb structure 1 does not necessarily have to have the pair of electrode layers 5.

[0035] Next, Fig. 2 is an explanatory diagram showing details of the filler 4 in Fig. 1. The lower side of each of Fig. 2(a) to (c) shows a cross section of the filler 4 in a plane perpendicular to the extension direction of the cells 21a. Moreover, the upper side of each of Fig. 2(a) to (c) shows the outer surface of the filler 4 when viewed from the radial outside of the honeycomb structure 1.

[0036] As shown in Figures 2(a) to 2(c), when the filler 4 is viewed from the radially outer side of the honeycomb structure 1, the width Y of the filler 4 may differ for each slit 3. Figure 2(b) shows a state in which the width Y of the filler 4 is larger than the width Y in Figure 2(a). Figure 2(c) shows a state in which the width Y of the filler 4 is smaller than the width Y in Figure 2(a).

[0037] 2(a) and 2(b) show a state in which the width Y of the filler 4 is larger than the width X of the slit 3 on the outer peripheral surface 1a of the honeycomb structure 1. On the other hand, FIG. 2(c) shows a state in which the width Y of the filler 4 is the same as the width X of the slit 3 on the outer peripheral surface 1a of the honeycomb structure 1.

[0038] As described above, the outer peripheral surface 1a of the honeycomb structure 1 can be understood as the outer peripheral wall 20 of the honeycomb structure portion 2 or the outer peripheral surface of the electrode layer 5. The widths X and Y of the slits 3 and the filler 4 can be understood as the dimensions of the slits 3 and the filler 4 in the circumferential direction of the honeycomb structure 1 (honeycomb structure portion 2). The difference in the widths X and Y of the slits 3 and the filler 4 may be due to the filler 4 slightly protruding radially outward from the outer peripheral surface 1a of the honeycomb structure 1. The portion of the filler 4 protruding from the outer peripheral surface 1a of the honeycomb structure 1 may be referred to as a protruding portion 4a. The protruding portion 4a may be due to masking applied to the outer peripheral surface 1a of the honeycomb structure 1 when the filler 4 is filled into the slits 3. In other words, the thickness of the protruding portion 4a may correspond to the thickness of the masking.

[0039] Variation in the width Y of the filler 4 for each slit 3 causes variation in the stress relaxation performance of the honeycomb structure 1, which may cause cracks to occur in the honeycomb structure 1 when the honeycomb structure 1 is heated. Therefore, it is believed that by reducing the variation in the width Y of the filler 4, it is possible to reduce the risk of cracks occurring in the honeycomb structure 1 when heated.

[0040] In the honeycomb structure 1 of this embodiment, when the difference between the width Y of the filler 4 and the width X of the slit 3 (width difference per slit) expressed by the following formula (1) is determined for each slit 3, the difference between the maximum value A of the difference and the minimum value B of the difference expressed by the following formula (2) is set to 0.4 mm or less. As will be explained later with reference to examples, by setting the value of the following formula (2) to 0.4 mm or less, it is possible to reduce the risk of cracks occurring in the honeycomb structure 1 when heated. More preferably, the difference between the maximum value A of the difference and the minimum value B of the difference is 0.2 mm or less, and even more preferably 0.1 mm or less. (YX) (1) (AB) (2) In formula (1), X represents the width of the slit 3 on the outer peripheral surface 1a of the honeycomb structure 1, and Y represents the width of the filler 4 when viewed from the outside in the radial direction of the honeycomb structure 1.

[0041] The effect of controlling the variation in the difference (the difference between the maximum value A and the minimum value B) between the width Y of the filler 4 and the width X of the slit 3, which is calculated for each slit, within the above range, as shown in the formula (1), to reduce the risk of cracks occurring in the honeycomb structure 1 when heated, is presumed as follows: When filling the slits 3 with the filler 4, the outer peripheral surface 1a of the honeycomb structure 1 on which the slits 3 are formed is masked, and then the filler 4 is filled into the slits 3. If the width of the masking slits varies depending on the masking arrangement method, the width Y of the filler 4 when viewed from the radial outside of the honeycomb structure 1 after filling the slits 3 also varies. This variation in the width Y of the filler 4 causes variation in the stress relaxation performance in the circumferential direction of the honeycomb structure 1. For example, cracks may occur in areas of the honeycomb structure 1 with low stress relaxation performance when the honeycomb structure 1 is heated. In contrast to this, by suppressing the variation in the difference between the width Y of the filler 4 and the width X of the slit 3 as described above, it is thought that the variation in the width Y of the filler 4 is suppressed, and the variation in the circumferential stress relaxation performance of the honeycomb structure 1 is suppressed.

[0042] The width X of each slit 3 can be determined as the average value of measurements made by using a microscope to measure both ends of the slit 3 in the extension direction of the cells 21a from the end face side of the honeycomb structure 1. The width Y of each filler 4 can be determined as the average value of measurements made by using a microscope to measure both ends of the width of the filler 4 in the extension direction of the cells 21a from the end face side of the honeycomb structure 1.

[0043] The width X of each of the slits 3 is not limited to, but may be 0.2 mm to 1.0 mm. When the width X of the slits 3 is 0.2 mm or more, the filler 4 can be smoothly filled into the slits 3. When the width X of the slits 3 is 1.0 mm or less, the risk of damaging the partition walls 21 that define adjacent cells 21a during the formation of the slits 3 can be reduced. More preferably, the width X of each of the slits 3 is 0.4 mm to 0.7 mm.

[0044] Furthermore, from the viewpoint of stress relaxation effect, the honeycomb structure 1 may have two or more slits 3, and more preferably has six or more slits 3. There is no particular upper limit on the number of slits 3, but it can be 12 or less.

[0045] Next, Fig. 3 is an explanatory view showing a manufacturing method of the honeycomb structure 1 according to the embodiment of the present invention. Although not limited thereto, the honeycomb structure 1 in which the variation in the difference between the width Y of the filler 4 and the width X of the slit 3 is reduced as described above can be manufactured by the manufacturing method shown in Fig. 3.

[0046] The manufacturing method shown in FIG. 3 includes a preparation step (step S1), a masking step (step S2), a slit forming step (step S3), a filling step (step S4), and a removal step (step S5).

[0047] The preparation step (step S1) is a step of preparing a honeycomb structure element 10 including a honeycomb structure portion 2 having an outer peripheral wall 20 and partition walls 21 arranged inside the outer peripheral wall 20 and partitioning a plurality of cells 21a that form flow paths extending from one end face to the other end face. The honeycomb structure element 10 may have the same configuration as the honeycomb structure 1 described above with reference to FIG. 1, except that it does not have the slits 3 and the fillers 4. The honeycomb structure element 10 may have a pair of electrode layers 5. In the preparation step, a honeycomb structure element 10 manufactured by a third party may be obtained. That is, the preparation step does not have to involve the manufacture of the honeycomb structure element 10.

[0048] The masking step (step S2) is a step of applying a masking 6 to the outer peripheral surface 10a of the honeycomb structure element 10. The outer peripheral surface 10a of the honeycomb structure element 10 may be understood as the outer peripheral wall 20 of the honeycomb structure section 2 or the outer peripheral surface of the electrode layer 5, similar to the outer peripheral surface 1a of the honeycomb structure 1 described above. The masking 6 can be applied by wrapping a masking sheet around the outer peripheral surface 10a of the honeycomb structure element 10, although this is not limited thereto. The masking 6 covers the entire outer peripheral surface 10a. For example, a common masking tape with a Japanese paper base and a rubber-based adhesive can be used as the masking 6.

[0049] The slit forming step (step S3) is a step of processing the honeycomb structure element 10 from the radially outer side after applying the masking 6, to form a plurality of slits 3 in the outer peripheral surface 10a of the honeycomb structure element 10, the slits 3 extending radially inward from the outer peripheral surface 10a of the honeycomb structure element 10 and extending in the extension direction of the cells 21a. The processing for forming the slits 3 may include relatively inserting a processing tool into the inside of the outer peripheral surface 10a of the honeycomb structure element 10 from the radially outer side, and relatively moving the processing tool in the extension direction of the cells 21a. The insertion and movement of the processing tool can be performed by moving at least one of the honeycomb structure element 10 and the processing tool relative to the other. As the processing tool, a disc-shaped cutting tool having abrasive grains attached to the outer edge can be used.

[0050] In this slit forming process, masking slits 60 are formed in the masking 6 in accordance with the formation of the slits 3. The slits 3 and the masking slits 60 are formed at substantially the same time using the same processing tool. The masking slits 60 have the same width as the slits 3. The masking slits 60 are located at the same position as the slits 3.

[0051] The filling step (step S4) is a step of filling the slits 3 with the filler 4 after forming a plurality of slits 3. The filling of the filler 4 into the slits 3 is carried out through the masking slits 60. Although not limited to this, the filler 4 can be filled into the slits 3 by supplying the filler 4 onto the masking 6 and then rotating the honeycomb structure element 10 while pressing the tip of a spatula (not shown) against the outer surface of the masking 6. As another method, the filler 4 may be filled into the slits 3 through the masking slits 60 using a syringe (not shown), and then the filler 4 on the masking 6 may be leveled using a spatula (not shown).

[0052] The removal step (step S5) is a step of removing the masking 6 after filling with the filler 4. The masking 6 may be removed after the filler 4 has solidified. The honeycomb structure element 10 from which the masking 6 has been removed can be treated as the honeycomb structure 1. By removing the masking 6, the outer peripheral surface 1a of the honeycomb structure 1 appears.

[0053] When the filler 4 on the outer peripheral surface 1a of the honeycomb structure 1 is observed after the masking 6 is removed, it is considered to be in a state roughly similar to that shown in FIG. 2(c). That is, it is considered that the width Y of the filler 4 is the same as the width X of the slit 3 on the outer peripheral surface 1a of the honeycomb structure 1. This is because the slits 3 and the masking slits 60 are formed together in the same process, and the masking slits 60 have the same width as the slits 3. The difference between the width Y of the filler 4 and the width X of the slit 3 can be reduced in all slits 3. It is considered that the difference between the width Y of the filler 4 and the width X of the slit 3 is substantially zero in all slits 3. Therefore, it is expected that the value shown by the above formula (2) for each slit 3 (the difference between the maximum value A and the minimum value B) will also be 0.4 mm or less.

[0054] In addition to the above-mentioned manufacturing method, the value shown in the formula (2) (the difference between the maximum value A and the minimum value B) can also be set to 0.4 mm or less by a method in which, after the masking step (step S2) is performed, the masking is removed from the portion corresponding to the slit formation portion, and then the slit 3 is formed and filled with the filler 4. Furthermore, the value shown in the formula (2) (the difference between the maximum value A and the minimum value B) can also be set to 0.4 mm or less by a method in which a masking tape provided with slits 3 of a predetermined width is attached to the slits 3 of the honeycomb structure element 10 with high precision positioning.

[0055] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Example]

[0056] Next, an example will be given. (1. Preparation of clay and honeycomb molded body) A ceramic raw material was prepared by mixing silicon carbide (SiC) powder and metallic silicon (Si) powder in an 80:20 mass ratio. Hydroxypropyl methylcellulose was added as a binder, a water-absorbent resin as a pore-forming material, and water to the ceramic raw material to form a molding raw material. The molding raw material was then kneaded using a vacuum kneader to produce cylindrical clay. The binder content was controlled to 7 parts by mass per 100 parts by mass of the silicon carbide (SiC) powder and metallic silicon (Si) powder. The pore-forming material content was controlled to 3 parts by mass per 100 parts by mass of the silicon carbide (SiC) powder and metallic silicon (Si) powder. The water content was controlled to 42 parts by mass per 100 parts by mass of the silicon carbide (SiC) powder and metallic silicon (Si) powder.

[0057] The cylindrical clay was molded using an extruder with a checkerboard die structure to produce a cylindrical honeycomb molded body in which each cell shape in the cross section perpendicular to the cell flow direction is hexagonal. The honeycomb molded body was then dried by high-frequency dielectric heating and then dried in a hot air dryer at 120°C for 2 hours to produce a dried honeycomb body.

[0058] (2. Preparation and application of electrode forming paste) Metallic silicon (Si) powder, silicon carbide (SiC) powder, methyl cellulose, glycerin, and water were mixed in a planetary centrifugal mixer to prepare an electrode-forming paste. The Si powder and SiC powder were blended in a volume ratio of Si powder:SiC powder = 40:60. The amount of methyl cellulose was controlled to be 0.5 parts by mass, glycerin to be 10 parts by mass, and water to be 38 parts by mass, assuming a total of 100 parts by mass of the Si powder and SiC powder. Next, this electrode portion forming paste was applied to the dried honeycomb body in an appropriate area and film thickness using a curved surface printing machine.

[0059] (3. Preparation of honeycomb fired body) Next, the dried honeycomb body with the electrode part forming paste was fired in an Ar atmosphere at 1400°C for 3 hours, and then oxidized in an air atmosphere at 1300°C for 1 hour to produce a columnar honeycomb fired body (honeycomb structure element 10). The above steps correspond to the preparation steps described with reference to Fig. 3.

[0060] (4. Masking and slit formation) A masking 6 (product name: masking tape, manufactured by Nichiban Co., Ltd.) was applied to the honeycomb structure element 10 manufactured as described above so as to cover the entire outer peripheral surface 10a (the outer peripheral surfaces of the outer peripheral wall 20 and the electrode layer 5) of the honeycomb structure element 10, and then a plurality of slits 3 were formed at intervals in the circumferential direction of the honeycomb structure element 10. The slits 3 were formed by inserting a processing tool from the outside of the masking 6 to the inside of the outer peripheral wall 20 and moving the processing tool in the extension direction of the cells 21a. As the processing tool, a disk-shaped cutting tool (product name: diamond rim saw, manufactured by Noritake Co., Limited) having abrasive grains attached to its outer edge was used.

[0061] The filler used was prepared as follows. First, silicon carbide powder (average particle size 8 μm) and silica powder (colloidal silica) were mixed in a mass ratio of 68:32 in terms of solid content. The mass of silica was calculated as the mass of oxide (SiO2). Carboxymethyl cellulose as a binder, glycerin as a humectant, and water were added and mixed to obtain a mixture. Next, this mixture was kneaded to obtain a filler. The binder content was 1.0 part by mass when the total solid content of the silicon carbide powder and silica powder was 100 parts by mass. The glycerin content was 4 parts by mass when the total solid content of the silicon carbide powder and silica powder was 100 parts by mass. The water content was 30 parts by mass when the total solid content of the silicon carbide powder and silica powder was 100 parts by mass.

[0062] (5. Filling and masking removal) After the slits 3 were formed, the filler 4 was filled into the slits 3 through the masking slits 60 of the masking 6. The filling of the filler 4 was carried out by supplying the filler 4 onto the masking 6, and then rotating the honeycomb structure element 10 while pressing the tip of a spatula against the outer surface of the masking 6. Thereafter, the honeycomb structure element 10 was dried at 120°C for 1 hour to solidify the filler 4 filled into the slits 3, and the masking 6 was removed.

[0063] (6. Dimensional measurement and strength test) A plurality of honeycomb structures 1 (Examples) manufactured through the above-described steps were subjected to dimensional measurement and strength tests.

[0064] In the dimensional measurement, the width Y of the filler 4 and the width X of the slit 3 were measured for each slit 3. Furthermore, the difference between the width Y of the filler 4 and the width X of the slit 3, as shown in the following formula (1), was calculated for each slit 3, and the difference between the maximum value A of the difference and the minimum value B of the difference, as shown in the following formula (2), was calculated. The width X of each slit 3 was calculated by measuring both ends of the slit 3 in the extension direction of the cells 21a from the end face side of the honeycomb structure 1 using a microscope (manufactured by Keyence Corporation, device name VHX-7000) and averaging the measured values. The width Y of each filler 4 was calculated by measuring both ends of the width of the filler 4 in the extension direction of the cells 21a from the end face side of the honeycomb structure 1 using the microscope and averaging the measured values. (YX) (1) (AB) (2)

[0065] In the strength test, a three-point bending strength test was performed as shown in FIG. 4 . Specifically, a plurality of test pieces 100 were prepared from the honeycomb structure 1 by cutting the outer peripheral portion of the honeycomb structure 1 in an arc shape so as to include the slits 3 and the fillers 4. The test pieces 100 were cut by cutting the honeycomb structure 1 along a straight line parallel to the radial direction of the honeycomb structure 1. More specifically, the honeycomb structure 1 was cut along the straight line at a position radially inward by one cell 21a from the tip (partition wall 21 located at the radially inner end) of the slits 3 (and the fillers 4). Then, the partition wall 21 defining the excess cell 21a was scraped off so that the tip of the slit 3 was exposed. At this time, the tip of the slit 3 was made flat. The slit 3 and the fillers 4 were located at the center of the width of the test piece 100. The test piece 100 was a rectangular shape with a thickness of approximately 3.7 mm in the direction in which the slit 3 extended, a depth of approximately 10 mm in the direction in which the cell 21a extended, and a width of approximately 25 mm in the direction perpendicular to the thickness. These dimensions were measured using a vernier caliper. The measurement device used was an Instron 5569 compression tester. For each test piece 100, with the linear cut surface of the test piece 100 facing upward, the curved outer surface of the test piece 100 was supported from below by two supports 101 and 102 (with a distance between the supports of 10 mm). A pressing body 103 placed above the test piece 100 was pressed against the center of the test piece 100 in the width direction. The pressing body 103 was fixed to a load cell. The pressing body 103 was pressed against the test piece 100 with a load of 1 kN and a load application rate of 0.5 mm / min, and the strength was calculated from the maximum load measured by the load cell. More specifically, the pressing body 103 has a semicircular tip 103a with a radius of 0.5 mm, and the tip 103a of the pressing body 103 is pressed against the tip of the flat shaped slit 3. This strength measurement was carried out for each slit 3, and the maximum value A and minimum value B, as well as the strength variation, which is the difference between the maximum and minimum strength values, were determined.

[0066] For comparison, a honeycomb structure 1 (comparative example) was also produced in which, after the slits 3 were formed, a masking 6 was manually applied to the outer peripheral surface of the honeycomb structure element 10 so as to exclude the slits 3, and then the slits 3 were filled with a filler 4. Then, the above-mentioned dimensional measurement and strength test were also carried out on such a comparative example. The results of the dimensional measurement and strength test in the example and comparative example are shown in Table 1 below.

[0067] [Table 1]

[0068] As shown in Table 1, in the comparative example, the difference between the maximum value A and the minimum value B was 1.0 mm, and the variation in strength (the difference between the maximum and minimum strength values) was 0.3 MPa. In contrast, in all of the examples, the difference between the maximum value A and the minimum value B was 0.4 mm or less, and the variation in strength was 0.1 MPa or less. From these results, it can be seen that by making the difference between the maximum value A and the minimum value B 0.4 mm or less, it is possible to reduce the risk of cracks occurring in the honeycomb structure 1 when heated. It can also be seen that by forming the slits 3 after applying the masking 6, it is possible to reduce the difference between the maximum value A and the minimum value B. [Explanation of symbols]

[0069] 1: Honeycomb structure 1a: Outer surface 10: Honeycomb structure element 2: Honeycomb structure 20:Outer wall 21: Bulkhead 21a: Cell 3: Slit 4: Filling material 5: Electrode layer 6: Masking

Claims

1. A honeycomb structure including a honeycomb structure part having an outer peripheral wall and partition walls disposed inside the outer peripheral wall and defining a plurality of cells that form flow paths extending from one end face to the other end face, a plurality of slits extending radially inward from the outer peripheral surface of the honeycomb structure and extending in the extension direction of the cells; A filler material filled in the plurality of slits; Furthermore, the filler has a protruding portion protruding from the outer peripheral surface of the honeycomb structure, When the difference between the width Y of the filler and the width X of the slit, which is expressed by the following formula (1), is calculated for each slit, the difference between the maximum value A of the difference and the minimum value B of the difference, which is expressed by the following formula (2), is 0.4 mm or less. (Y-X) ...(1) (A-B) ...(2) (In formula (1), X represents the width of the slit on the outer peripheral surface of the honeycomb structure, and Y represents the width of the filler when viewed from the radially outer side of the honeycomb structure.) Honeycomb structure.

2. Each of the slits has a width X of 0.2 mm to 1.0 mm. The honeycomb structure according to claim 1 .

3. The honeycomb structure portion has two or more of the slits. The honeycomb structure according to claim 1 or 2.

4. The outer peripheral surface of the outer peripheral wall constitutes at least a part of the outer peripheral surface of the honeycomb structure. The honeycomb structure according to any one of claims 1 to 3.

5. a pair of electrode layers are provided on the outer surface of the outer wall, with the central axis of the honeycomb structure section in between, so as to extend in a strip-like shape in the extension direction of the cells; At the positions where the pair of electrode layers are provided, the outer peripheral surfaces of the pair of electrode layers constitute the outer peripheral surface of the honeycomb structure. The honeycomb structure according to any one of claims 1 to 4.

6. In a honeycomb structure element having a honeycomb structure part having an outer peripheral wall and partition walls disposed inside the outer peripheral wall and defining a plurality of cells forming flow paths extending from one end face to the other end face, a masking step of masking an outer peripheral surface of the honeycomb structure element is performed; a slit forming step of processing the honeycomb structure body from a radially outer side after the masking step, and forming a plurality of slits in the honeycomb structure body, the slits extending radially inward from an outer peripheral surface of the honeycomb structure body and extending in an extension direction of the cells; a filling step of filling the plurality of slits with a filler material after the slit forming step; a removing step of removing the masking after filling the filling material; Including, A method for manufacturing a honeycomb structure.

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