JP6830018B2 - Honeycomb structure - Google Patents

Description

The present invention relates to a honeycomb structure. In particular, the present invention relates to a honeycomb structure that is a catalyst carrier and can also function as a heater by applying a voltage.

Conventionally, a honeycomb structure made of cordierite or silicon carbide with a catalyst supported has been used for treating harmful substances in exhaust gas discharged from an automobile engine (see, for example, Patent Document 1). Such a honeycomb structure generally has a columnar honeycomb structure having a partition wall that serves as a flow path for exhaust gas and partitions a plurality of cells extending from one bottom surface to the other bottom surface.

When treating exhaust gas with a catalyst supported on a honeycomb structure, it is necessary to raise the temperature of the catalyst to a predetermined temperature, but when the engine is started, the catalyst temperature is low, so that the exhaust gas is not sufficiently purified. It was.

Therefore, Patent Document 2 proposes a honeycomb structure which is a catalyst carrier and also functions as a heater by applying a voltage and can suppress a bias of temperature distribution when a voltage is applied. Specifically, in Patent Document 2, a pair of electrode portions are arranged on the side surface of the columnar honeycomb structure in a band shape extending in the extending direction of the cells of the honeycomb structure portion, and in a cross section orthogonal to the extending direction of the cells. By arranging one electrode portion of the pair of electrode portions on the opposite side of the other electrode portion of the pair of electrode portions with the center of the honeycomb structure portion interposed therebetween, the temperature distribution is biased when a voltage is applied. Is suppressed.

Further, in Patent Document 2, in order to enhance the thermal shock resistance of the honeycomb structure, a slit opened on the side surface of the honeycomb structure is provided at the center of each of the pair of electrode portions in a cross section orthogonal to the extending direction of the cell. It has been proposed to form one or more so as not to intersect the straight lines connecting each other.

However, in the technique described in Patent Document 2, since a pair of electrodes are arranged on the side surface of the columnar honeycomb structure portion, heat is generated from the outer peripheral portion to the central portion of the honeycomb structure when energized. Therefore, there is room for improvement in that the time required for "raising the temperature of the central portion to the temperature required for ensuring the purification performance" is shortened.

Therefore, in Patent Document 3, in order to enable the temperature to be raised to the required temperature up to the central portion in a short time, there is a technique for making the opening ratio of the central portion of the honeycomb structure smaller than the opening ratio of the outer peripheral portion. Proposed. By making the opening ratio of the central portion of the honeycomb structure smaller than the opening ratio of the outer peripheral portion, the electrical resistivity of the central portion becomes lower than the electrical resistivity of the outer peripheral portion, so that when a voltage is applied to the honeycomb structure, A large amount of current flows in the central part, and the central part generates heat faster than before. Further, Patent Document 3 describes that it is preferable to make the thickness of the partition wall in the central portion larger than the thickness of the partition wall in the outer peripheral portion in order to make the opening ratio in the central portion smaller than the opening ratio in the outer peripheral portion. ing.

Japanese Patent No. 41363319 International Publication No. 2013/146955 International Publication No. 2015/151823

By combining the techniques of Patent Document 2 and Patent Document 3, it is possible to provide a honeycomb structure having good thermal shock resistance and current-carrying performance. However, if a slit is provided on the side surface of the honeycomb structure, there is a problem that cracks are likely to occur starting from the vicinity of the deepest portion of the slit due to repeated cooling and heating cycles.

The present invention has been made to solve the above problems, and one of the problems is to improve the thermal shock resistance in a columnar honeycomb structure having a pair of electrode portions and one or more slits on the side surfaces. ..

It is considered that the reason why cracks are likely to occur starting from the vicinity of the deepest part of the slit is that stress is generated in the portion. The present inventor has found that the following two points are the main factors that cause stress to be generated around the deepest part of the slit.
(1) When the partition wall thickness around the inner surface of the slit is thin, the partition wall around the deepest part of the slit is easily bent by being pulled from the outer peripheral side wall of the honeycomb structure during heating.
(2) When the ratio of the thickness of the outer peripheral side wall to the thickness of the partition wall around the inner surface of the slit is large, the tension also increases.
Then, the present inventor has found that it is important to adjust the ratio of the thickness of the partition wall around the slit to the thickness of the outer peripheral portion in order to reduce the tensile force from the outer peripheral portion. The present invention has been completed based on such findings, and is specified as follows.

In one aspect, the present invention
A columnar honeycomb structure having an outer peripheral side wall and a partition wall arranged inside the outer peripheral side wall and partitioning a plurality of cells forming a flow path from one bottom surface to the other bottom surface.
A pair of electrode portions extending in a band shape in the cell flow path direction on the outer surface of the outer peripheral side wall with the central axis of the honeycomb structure portion in between, and
One or more slits with openings extending in the cell flow direction on the outer surface of the outer sidewall,
It is a conductive honeycomb structure equipped with
In the cross section orthogonal to the flow path direction of the cells, the average thickness of the outer peripheral side wall is T _1, and the plurality of cells adjacent to the inner surface of each slit are each the first cell, and the first to third cells are in the order of proximity to the inner surface of each slit. Assuming that the thickness of the partition wall portion forming the cells up to the third cell is T ₂ , the conductive honeycomb structure always holds the relational expression of 1.0 ≤ T ₁ / T ₂ ≤ 3.0.

In one embodiment of the conductive honeycomb structure according to the present invention, the relational expression of 1.5 ≦ T ₁ / T ₂ ≦ 2.8 always holds.

In another embodiment of the conductive honeycomb structure according to the present invention, 0.1 mm ≤ T ₁ ≤ 0.5 mm.

In yet another embodiment of the conductive honeycomb structure according to the present invention, 0.1 mm ≤ T ₂ ≤ 0.3 mm.

In yet another embodiment of the conductive honeycomb structure according to the present invention, in a cross section orthogonal to the flow path direction of the cells, a plurality of cells adjacent to the inner surface of each slit are designated as the first cell, respectively. When the thickness of the partition wall portion defining a cell in the distance from the tenth be counted from the inner surface of the slit and T _3, the relational expression of T _2> T ₃ is always satisfied.

In yet another embodiment of the conductive honeycomb structure according to the present invention, 0.08 mm ≤ T ₃ ≤ 0.3 mm.

In yet another embodiment of the conductive honeycomb structure according to the present invention, the relational expression of 1.0 ≤ T ₁ / T ₃ ≤ 2.5 always holds.

In yet another embodiment of the conductive honeycomb structure according to the present invention, in a cross section orthogonal to the flow path direction of the cell, the length from the center to the outer surface of the outer peripheral side wall from the center to the outer surface of the outer peripheral side wall. When the area up to the position of 10% is the central part and the area up to the position of 10% of the length from the outer surface to the center of the outer peripheral side wall toward the center is the outer peripheral part. The opening ratio of the central portion is 0.70 to 0.95 times the opening ratio of the outer peripheral portion.

In yet another embodiment of the conductive honeycomb structure according to the present invention, at least a part of the internal space of the one or more slits is filled with a filler.

According to the present invention, in a columnar honeycomb structure having a pair of electrode portions and one or more slits on the side surface, it is possible to reduce the occurrence of cracks starting from the vicinity of the deepest part of the slits due to thermal shock, and heat resistance is increased. It is possible to increase the impact resistance. Therefore, when the honeycomb structure according to the present invention is used for exhaust gas treatment, it is possible to prevent cracks from being generated due to thermal shock when passing through the exhaust gas, thereby improving mechanical durability and preventing deterioration of purification performance. The effect of extending the service life of the structure can be obtained.

It is a perspective view which shows roughly one Embodiment of the honeycomb structure of this invention. It is a figure which shows roughly the cross section orthogonal to the flow path direction of a cell of one Embodiment of the honeycomb structure of this invention. It is a figure which shows typically the cross section parallel to the flow path direction of a cell of one Embodiment of the honeycomb structure of this invention. In the case of one embodiment of the honeycomb structure of the present invention in which the shape of the cell in the cross section in the direction orthogonal to the flow path of the cell is a regular quadrangle, the partial structure of the honeycomb structure portion is schematically illustrated. In the case of one embodiment of the honeycomb structure of the present invention in which the shape of the cell in the cross section in the direction orthogonal to the flow path of the cell is a regular hexagon, the partial structure of the honeycomb structure portion is schematically illustrated. It is a figure explaining the positional relationship of the electrode part in the cross section orthogonal to the flow path direction of a cell of one Embodiment of the honeycomb structure of this invention. It is a perspective view schematically showing still another embodiment of the honeycomb structure of this invention. It is a perspective view schematically showing still another embodiment of the honeycomb structure of this invention. It is a perspective view schematically showing still another embodiment of the honeycomb structure of this invention. It is a perspective view schematically showing still another embodiment of the honeycomb structure of this invention. It is a perspective view schematically showing still another embodiment of the honeycomb structure of this invention. It is a perspective view schematically showing still another embodiment of the honeycomb structure of this invention. It is a perspective view schematically showing still another embodiment of the honeycomb structure of this invention. It is a perspective view schematically showing still another embodiment of the honeycomb structure of this invention. It is a perspective view schematically showing still another embodiment of the honeycomb structure of this invention.

Next, a mode for carrying out the present invention will be described in detail with reference to the drawings. It is understood that the present invention is not limited to the following embodiments, and design changes, improvements, etc. may be appropriately made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. Should be.

(1) Honeycomb Structure In one embodiment, the honeycomb structure 100 of the present invention includes a columnar honeycomb structure portion 4 and a pair of electrode portions 21 as shown in FIGS. 1 to 3. The columnar honeycomb structure 4 is arranged inside the outer peripheral side wall 3 and the outer peripheral side wall 3, and forms a flow path through from the first bottom surface 11 which is one bottom surface to the second bottom surface 12 which is the other bottom surface. It has a partition wall 1 for partitioning a plurality of cells 2 to be formed. The partition wall 1 can be made porous. A fluid can flow through the flow paths of the plurality of cells 2. Hereinafter, the first bottom surface 11 and the second bottom surface 12 of the honeycomb structure portion 4 may be collectively referred to as “the bottom surface of the honeycomb structure portion 4”. The pair of electrode portions 21 extend in a strip shape in the cell flow path direction on the outer surface 5 of the outer peripheral side wall 3 of the honeycomb structure portion 4 with the central axis of the honeycomb structure portion 4 interposed therebetween. Then, on the outer surface 5 of the outer peripheral side wall 3, one or more slits 6 having an opening extending in the flow path direction of the cell 2 are formed.

The honeycomb structure portion 4 of the honeycomb structure 100 of the present embodiment is made of a conductive material, and when a voltage is applied between the pair of electrode portions 21, it is energized and can generate heat by Joule heat. Therefore, the honeycomb structure portion 4 can be suitably used as a heater. The voltage to be applied is preferably 12 to 900 V, more preferably 64 to 600 V, but the applied voltage can be changed as appropriate. Further, by supporting the catalyst on the honeycomb structure portion 4, the honeycomb structure 100 can be used as a catalyst body.

The isostatic strength of the honeycomb structure 100 of the present embodiment is preferably 1 MPa or more, and more preferably 3 MPa or more. The larger the value of the isostatic strength, the more preferable it is, but considering the material, structure, etc. of the honeycomb structure 100, the upper limit is about 6 MPa. If the isostatic strength is less than 1 MPa, the honeycomb structure may be easily damaged when used as a catalyst carrier or the like. The isostatic strength is a value measured by applying hydrostatic pressure in water.

(1-1 Honeycomb structure)
In the honeycomb structure 100 of the present embodiment, the honeycomb structure portion 4 has a plurality of cells adjacent to the inner surface of each slit 6 in which the average thickness of the outer peripheral side wall 3 is T ₁ in a cross section orthogonal to the flow path direction of the cell 2. With 2 as the first cell, the thickness of the partition wall portion (hereinafter, may be referred to as “partition wall near the inner surface of the slit”) that partitions the first to third cells 2 in the order closer to the inner surface of each slit 6. When is T ₂ , the relational expression of 1.0 ≤ T ₁ / T ₂ ≤ 3.0 always holds. That is, there are a plurality of partition walls in the honeycomb structure portion 4 that partition the first to third cells 2 in the order closer to the inner surface of each slit 6, and all of these partition walls satisfy the above relational expression.

FIG. 4-1 illustrates the partial structure of the honeycomb structure portion 4 in the case where the shape of the cell 2 in the cross section orthogonal to the flow path direction of the cell is square in order to illustrate how to order the cells. There is. Further, FIG. 4-2 illustrates the partial structure of the honeycomb structure portion 4 in the case where the shape of the cell 2 in the cross section orthogonal to the flow path direction of the cell is a regular hexagon. The cells are numbered in ascending order of distance from the inner surface of each slit 6.

As can be understood from FIGS. 4-1 and 4-2, in the place where the first cell and the second cell are adjacent to each other, the partition wall 1 adjacent to both cells is the partition wall forming the first cell. It is also a partition that forms the second cell. Similarly, in the place where the nth cell and the n + 1st cell are adjacent to each other, the partition wall 1 adjacent to both cells is also the partition wall forming the nth cell, and the partition wall forming the n + 1th cell. It is also (n refers to a natural number). If the shape of the cell 2 in the cross section orthogonal to the flow path direction of the cell of the honeycomb structure portion 4 becomes complicated, it is conceivable that a specific partition wall forms a large number of cells, but in the present invention, such a case. , The cell having the smallest number among the cells adjacent to the partition wall (the cell closest to the slit of interest) is treated as a partition wall forming a partition.

By satisfying T ₁ / T ₂ ≤ 3.0, the partition wall 1 near the inner surface of the slit 6 is less likely to be pulled by the outer peripheral side wall 3 of the honeycomb structure portion 4 during heating. As a result, it is possible to reduce the occurrence of cracks starting from the vicinity of the deepest part of the slit due to thermal shock, and it is possible to improve the thermal shock resistance. From the viewpoint of enhancing thermal shock resistance, it is preferable that the relational expression of T ₁ / T ₂ ≤ 2.9 always holds, and more preferably that the relational expression of T ₁ / T ₂ ≤ 2.8 always holds. , T ₁ / T ₂ ≤ 2.5, it is even more preferable that the relational expression always holds.

Further, by satisfying 1.0 ≦ T ₁ / T ₂ , it is possible to prevent the outer peripheral side wall 3 from being pulled by the partition wall 1 in the vicinity of the slit 6 during heating. As a result, it is possible to suppress the occurrence of cracks on the outer peripheral side wall 3 due to thermal shock, and it is possible to enhance the thermal shock resistance. From the viewpoint of enhancing thermal shock resistance, it is preferable that the relational expression of 1.3 ≦ T ₁ / T ₂ always holds, and the relational expression of 1.5 ≦ T ₁ / T ₂ always holds. More preferably, it is even more preferable that the relational expression of 1.8 ≦ T ₁ / T ₂ always holds.

The average thickness T ₁ of the outer peripheral side wall 3 forming the outermost circumference of the honeycomb structure portion 4 is preferably 0.1 to 0.5 mm. By setting the average thickness T ₁ of the outer peripheral side wall 3 to 0.1 mm or more, preferably 0.15 mm or more, more preferably 0.2 mm or more, it is possible to prevent the strength of the honeycomb structure 100 from decreasing. By setting the average thickness T ₁ of the outer peripheral side wall 3 to 0.5 mm or less, preferably 0.45 mm or less, more preferably 0.4 mm or less, there is an advantage that the tensile force due to the outer wall can be suppressed by lowering the rigidity of the outer wall. Is obtained. Here, the thickness of the outer peripheral side wall 3 is a method with respect to the tangent line of the outer surface 5 of the outer peripheral side wall 3 at the measurement point when the portion of the outer peripheral side wall for which the thickness is to be measured is observed in a cross section orthogonal to the flow path direction of the cell. It is defined as the thickness in the line direction, and the average value of multiple measurement points is T ₁ . FIGS. 4-1 and 4-2 show exemplary measurement points of the average thickness T ₁ of the outer peripheral side wall 3.

The thickness T ₂ of the partition wall near the inner surface of the slit is preferably 0.1 to 0.3 mm. By setting the thickness T ₂ of the partition wall near the inner surface of the slit to 0.1 mm or more, preferably 0.11 mm or more, more preferably 0.12 mm or more, the occurrence of cracks starting from the vicinity of the deepest part of the slit 6 is suppressed. The effect can be enhanced. Further, by setting the thickness T ₂ of the partition wall near the inner surface of the slit to 0.3 mm or less, preferably 0.27 mm or less, more preferably 0.25 mm or less, when a fluid such as exhaust gas flows through the flow path of the honeycomb. It is possible to prevent the pressure loss from becoming too large. Here, the thickness of each partition wall 1 of the honeycomb structure portion 4 is the thickness when the centers of gravity of two adjacent cells 2 are connected by a line segment in a cross section orthogonal to the flow path direction of the cell 2 of the honeycomb structure portion 4. A line segment is defined as the length across the partition wall 1.

Further, in the cross section orthogonal to the flow path direction of the cell 2, the plurality of cells 2 adjacent to the inner surface of each slit 6 are each set as the first cell, and are farther than the tenth even when counted from the inner surface of any slit 6. Assuming that the thickness of the partition wall portion (hereinafter, sometimes referred to as “the partition wall away from the inner surface of the slit”) forming the cell partition is T ₃ , it is preferable that the relational expression of T ₂ > T ₃ always holds. it is preferred that the relationship of ₂ ≦ T 2 / T ₃ is always satisfied, always and more preferably satisfied the relational expression 1.5 ≦ T ₂ / T _3. That is, there are a plurality of partition walls separated from the inner surface of the slit in the honeycomb structure portion 4, and it is preferable that all of these partition walls satisfy the above relational expression. The occurrence of cracks starting from the vicinity of the deepest part of the slit 6 due to thermal impact can be prevented by securing the thickness of the partition wall around the inner surface of the slit 6, while increasing the thickness of all the partition walls of the honeycomb structure portion 4. Then, the pressure loss when a fluid such as exhaust gas is passed through the flow path of the cell 2 tends to increase. In order not to increase the pressure loss, it is necessary to increase the cross-sectional area of the honeycomb structure portion 4. Therefore, it is desirable that the thickness of the partition wall is small at a place away from the slit 6 in order to obtain a honeycomb structure that is compact and can secure a high flow rate. However, if the thickness T ₂ of the partition wall near the inner surface of the slit is too large with respect to the thickness T _{3 of} the partition wall away from the inner surface of the slit, an expansion difference based on the difference in rigidity will occur when expanding due to heat when passing exhaust gas or energizing. It is preferable that the relational expression of T ₂ / T ₃ ≤ 2.5 always holds, and the relational expression of T ₂ / T ₃ ≤ 2.0 is preferable because it may occur and cracks may occur inside the honeycomb. Is more preferable to always hold.

Further, it is preferable that the relational expression of 1.0 ≤ T ₁ / T ₃ ≤ 3.0 always holds. By satisfying the relational expression, the balance between T ₁ and T ₃ is improved, and an excessive tensile force is not applied to either of them, so that it is possible to prevent unexpected cracks from occurring during heating. It is more preferable that the relational expression of 1.2 ≤ T ₁ / T ₃ ≤ 2.8 always holds, and it is even more preferable that the relational expression of 1.5 ≤ T ₁ / T ₃ ≤ 2.5 always holds. ..

The thickness T _{3 of} the partition wall away from the inner surface of the slit is preferably 0.08 to 0.3 mm. By setting the thickness T _{3 of} the partition wall away from the inner surface of the slit to 0.08 mm or more, preferably 0.09 mm or more, more preferably 0.1 mm or more, it is possible to suppress a decrease in the strength of the honeycomb structure. Further, when the thickness T _{3 of} the partition wall away from the inner surface of the slit is set to 0.3 mm or less, preferably 0.25 mm or less, more preferably 0.2 mm or less, when a fluid such as exhaust gas flows through the flow path of the honeycomb. It is possible to prevent the pressure loss from becoming too large.

The thickness of the partition wall 1 in the honeycomb structure portion 4 is preferably 0.1 to 0.3 mm at any location regardless of whether the partition wall is near the inner surface of the slit or away from the inner surface of the slit. It is more preferably 0.15 to 0.25 mm. When the thickness of the partition wall 1 is 0.1 mm or more, it is possible to suppress a decrease in the strength of the honeycomb structure. When the thickness of the partition wall 1 is 0.3 mm or less, it is possible to suppress an increase in pressure loss when exhaust gas is flowed when the honeycomb structure 100 is used as a catalyst carrier and a catalyst is supported.

The honeycomb structure portion 4 preferably has a cell density of 40 to 150 cells / cm ² , and more preferably 70 to 100 cells / cm ² in a cross section orthogonal to the flow path direction of the cell 2. By setting the cell density in such a range, the purification performance of the catalyst can be improved while the pressure loss when the exhaust gas is flowed is reduced. If the cell density is lower than 40 cells / cm ² , the catalyst-supporting area may be small. If the cell density is higher than 150 cells / cm ² , when the honeycomb structure 100 is used as a catalyst carrier and the catalyst is supported, the pressure loss when the exhaust gas is flowed may increase.

In the honeycomb structure 100 of the present embodiment, the material of the honeycomb structure portion 4 is not particularly limited as long as it has conductivity, and metal, ceramics, or the like can be used. In particular, from the viewpoint of achieving both heat resistance and conductivity, the material of the honeycomb structure portion 4 is preferably a silicon-silicon carbide composite material or a material containing silicon carbide as a main component, and the silicon-silicon carbide composite material or carbonized material is preferable. Silicon is even more preferred. When the material of the honeycomb structure portion 4 is mainly composed of a silicon-silicon carbide composite material, the honeycomb structure portion 4 uses the silicon-silicon carbide composite material (total mass) as the main component of the honeycomb structure portion 4. It means that it contains 90% by mass or more. Here, the silicon-silicon carbide composite material contains silicon carbide particles as an aggregate and silicon as a binder for bonding the silicon carbide particles, and a plurality of silicon carbide particles are formed between the silicon carbide particles. It is preferably bonded by silicon so as to form pores. When the material of the honeycomb structure portion 4 is mainly composed of silicon carbide, the honeycomb structure portion 4 contains silicon carbide (total mass) in an amount of 90% by mass or more of the entire honeycomb structure portion 4. It means that it is.

The honeycomb structure portion 4 generates heat due to Joule heat, and for example, the electrical resistivity thereof is not particularly limited. For example, the electrical resistivity of the honeycomb structure portion 4 is preferably 0.01 to 200 Ωcm, more preferably 0.05 to 100 Ωcm. Further, the electrical resistivity of the honeycomb structure portion 4 can be selected according to the application in which the honeycomb structure 100 is used. The electrical resistivity of the honeycomb structure is a value measured at 400 ° C. by the four-terminal method.

When the material of the honeycomb structure portion 4 is a silicon-silicon carbide composite material, the "mass of silicon carbide particles as an aggregate" contained in the honeycomb structure portion 4 and the "bonding material" contained in the honeycomb structure portion 4. The ratio of the "mass of silicon as a binder" contained in the honeycomb structure 4 to the total of "mass of silicon as a binder" is preferably 10 to 40% by mass, and is preferably 15 to 35% by mass. Is even more preferable. If it is lower than 10% by mass, the strength of the honeycomb structure may decrease. If it is higher than 40% by mass, the shape may not be retained during firing.

The porosity of the partition wall 1 of the honeycomb structure portion 4 is preferably 35 to 60%, more preferably 35 to 45%. If the porosity is less than 35%, the deformation at the time of firing may be large. If the porosity exceeds 60%, the strength of the honeycomb structure may decrease. The porosity is a value measured by a mercury porosimeter.

The average pore diameter of the partition wall 1 of the honeycomb structure portion 4 is preferably 2 to 15 μm, and more preferably 4 to 8 μm. If the average pore diameter is smaller than 2 μm, the electrical resistivity may become too large. If the average pore diameter is larger than 15 μm, the electrical resistivity may become too small. The average pore diameter is a value measured by a mercury porosimeter.

The shape of the cell 2 in the cross section orthogonal to the flow path direction of the cell 2 is not limited, but is preferably a quadrangle, a hexagon, an octagon, or a combination thereof. Of these, squares and hexagons are preferred. By making the cell shape in this way, the pressure loss when the exhaust gas is passed through the honeycomb structure 100 is reduced, and the purification performance of the catalyst is excellent.

The outer shape of the honeycomb structure portion 4 is not particularly limited as long as it is columnar. For example, the bottom surface is a circular columnar shape (cylindrical shape), the bottom surface is an oval-shaped columnar shape, and the bottom surface is a polygonal shape (quadrangle, pentagon, hexagon, heptagon, etc.) It can have a columnar shape (octagonal shape, etc.). Also, the size of the honeycomb structure portion 4, for reasons of heat resistance (crack entering the outer periphery an outer wall portion), it is preferable that the area of the bottom surface is 2000～20000Mm ^2, and further preferably 4000～10000Mm ² .. Further, the length of the honeycomb structure portion 4 in the central axis direction is preferably 50 to 200 mm, preferably 75 to 150 mm, for the reason of heat resistance (cracks that enter parallel to the central axis direction on the outer peripheral side wall). More preferred.

Referring to FIG. 2, in a cross section orthogonal to the flow path direction of the cell, from the center O toward the outer surface 5 of the outer peripheral side wall 3 to a position of 10% of the length from the center O to the outer surface 5 of the outer peripheral side wall 3. When the region is the central portion and the region from the outer surface 5 of the outer peripheral side wall 3 toward the center O to the position of 10% of the length from the outer surface 5 to the center O of the outer peripheral side wall 3 is the outer peripheral portion. The opening ratio of the central portion is preferably 0.70 to 0.95 times, and more preferably 0.80 to 0.85 times the opening ratio of the outer peripheral portion. As a result, the electrical resistivity in the central portion becomes lower than the electrical resistivity in the outer peripheral portion, and when a voltage is applied to the honeycomb structure 100, a large amount of current flows in the central portion, and the central portion generates heat quickly. As a result, when a voltage is applied to the honeycomb structure 100 to purify the exhaust gas, the temperature can be raised to the required temperature up to the central portion in a short time. Then, the exhaust gas can be effectively treated in the central portion where more exhaust gas flows than in the outer peripheral portion. Further, the amount of heat when raising the temperature of the central portion to the required temperature can be reduced. In addition, thermal shock resistance can be improved.

The preferred aperture ratios of the central portion and the outer peripheral portion are as follows. The aperture ratio of the central portion is preferably 50 to 80%, more preferably 55 to 75%, and particularly preferably 60 to 70%. If it is less than 50%, the pressure loss may increase. If it is larger than 80%, it may be difficult to make the opening ratio of the central portion smaller than the opening ratio of the outer peripheral portion. The aperture ratio of the outer peripheral portion is preferably 55 to 85%, more preferably 60 to 80%, and particularly preferably 65 to 75%. If it is less than 55%, it may be difficult to make the aperture ratio of the outer peripheral portion larger than the opening ratio of the central portion. If it is larger than 85%, the strength of the honeycomb structure 100 may decrease.

Here, the "aperture ratio" is a value (cell area) obtained by dividing the area of the cell by the total area of the partition wall and the cell in the cross section orthogonal to the flow path direction of the cell 2 of the honeycomb structure portion 4. Total / (total cell area + total partition area)) is a value expressed as a percentage. That is, it can be said that the "aperture ratio" of each region is the average value of the "aperture ratio" in the corresponding region.

As a method of making the opening ratio of the central portion smaller than the opening ratio of the outer peripheral portion, there is a method of making the thickness of the partition wall 1 in the central portion thicker than the thickness of the partition wall 1 in the outer peripheral portion. At this time, the thickness of the partition wall 1 in the central portion is preferably greater than 1.0 times and less than 2.0 times the thickness of the partition wall 1 in the outer peripheral portion, and further preferably 1.2 to 1.8 times. It is preferable, and it is particularly preferable that it is 1.4 to 1.7 times. The reason why the upper limit is 2.0 times is that if it is thicker than 2.0 times, the pressure loss in the central portion becomes large and the exhaust gas may become difficult to flow.

As a method of making the opening ratio of the central portion smaller than the opening ratio of the outer peripheral portion, there is also a method of increasing the cell density of the central portion to be larger than the cell density of the outer peripheral portion. At this time, the cell density in the central portion is preferably larger than 1.0 and 1.5 times or less of the cell density in the outer peripheral portion, and more preferably greater than 1.0 and 1.4 times or less. It is particularly preferable that the value is 05 to 1.3 times. The reason why the upper limit is 1.5 times is that if it is larger than 1.5 times, the pressure loss in the central portion becomes large and the exhaust gas may become difficult to flow.

(1-2 slit)
As shown in FIGS. 1 and 2, in the honeycomb structure 100 of the present embodiment, the honeycomb structure portion 4 has a slit 6 having an opening extending in the flow path direction of the cell 2 on the outer surface 5 of the outer peripheral side wall 3. One or more are formed. The slit 6 may have an opening on the outer surface 5 of the outer peripheral side wall 3, and may extend to one or both of the first bottom surface 11 and the second bottom surface 12 and have an opening in them. The filler 7 may be filled in at least one slit 6. In the honeycomb structure 100 of the present embodiment, the filler 7 is filled so as to close at least a part of the internal space of the slit 6. By filling the slit 6 with the filler 7, the thermal shock resistance and isostatic strength of the honeycomb structure 100 can be improved, and the fluid flowing in the flow path of the cell 2 flows through the slit 6 to the honeycomb structure portion 4. It can be prevented from getting out of.

Referring to FIG. 2, at least one slit 6 is a line segment (center line) L connecting the central portions C in the circumferential direction of the pair of electrode portions 21 in a cross section orthogonal to the flow path direction of the cell 2. It is preferable that it is formed so as not to intersect with. By forming at least one slit 6 in this way, it is possible to suppress the bias of the temperature distribution of the honeycomb structure portion 4 when a voltage is applied, and it is possible to further improve the thermal shock resistance. Further, with such a configuration, it is possible to suppress the bias of the temperature distribution when a voltage is applied. Further, a honeycomb structure in which at least one slit 6 is formed so as not to intersect a straight line connecting the central portions C in the circumferential direction of the pair of electrode portions 21 in a cross section orthogonal to the flow path direction of the cell 2. The body 100 is also excellent in mechanical strength. In the honeycomb structure 100 of the present embodiment, each of the six slits 6 connects the central portions C of the pair of electrode portions 21 and 21 in the circumferential direction in a cross section orthogonal to the flow path direction of the cell 2. It is formed so as not to intersect the line segment L.

Hereinafter, in a cross section orthogonal to the flow path direction of the cell 2 of the honeycomb structure 100, a slit 6 formed so as not to intersect the line segment L connecting the central portions C in the circumferential direction of the pair of electrode portions 21 is provided. Sometimes referred to as a "non-crossing slit". Further, in a cross section orthogonal to the flow path direction of the cell 2 of the honeycomb structure 100, a slit 6 formed so as to intersect a line segment L connecting the central portions C in the circumferential direction of the pair of electrode portions 21 is provided. Sometimes referred to as an "intersection slit".

In the honeycomb structure 100 of the present embodiment, it is preferable that two or more slits 6 are formed in the honeycomb structure portion 4, and 50% or more of the two or more slits 6 are non-intersecting slits. .. Further, it is more preferable that all the slits 6 formed in the honeycomb structure portion 4 are non-intersecting slits. When the non-intersecting slits are 50% or more of the entire slits 6, it is possible to prevent the mechanical strength of the honeycomb structure 100 from being lowered. That is, the honeycomb structure 100 of the present embodiment has excellent mechanical strength. If the number of non-intersecting slits is less than 50% of the total number of slits 6, the number of intersecting slits may increase and the mechanical strength of the honeycomb structure 100 may decrease. Further, if the non-intersecting slit is less than 50% of the entire slit 6, the number of intersecting slits increases, so that the flow of the current flowing between the pair of electrodes 21 is greatly obstructed by the slits, and uniform heat generation is hindered. It may generate uniform heat.

In the honeycomb structure 100 of the present embodiment, the depth of the slit 6 may be referred to as a radius (hereinafter, referred to as "radius of the honeycomb structure portion") in the "cross section orthogonal to the flow path direction of the cell 2" of the honeycomb structure portion 4. It is preferably 1 to 80% of the above. The depth of the slit 6 is more preferably 1 to 60% of the radius of the honeycomb structure, and particularly preferably 1 to 30%. If the depth of the slit 6 is smaller than 1% of the radius of the honeycomb structure portion 4, it may be difficult to obtain the effect of improving the thermal shock resistance of the slit 6. When the depth of the slit 6 is larger than 80% of the radius of the honeycomb structure 4, the flow of the current flowing between the pair of electrodes 21 is greatly obstructed by the slit 6, and uniform heat generation is hindered, resulting in non-uniform heat generation. May become. The depth of each slit 6 is the distance from the “opening on the outer surface 5 of the outer peripheral side wall 3” of the slit 6 to the deepest position of the slit 6. When there are a plurality of slits, the depth of the slits 6 may be different depending on the slits, or all may be the same.

In the honeycomb structure 100 of the present embodiment, the opening width of the slit 6 is the length of the outer circumference of the honeycomb structure portion 4 in the “cross section orthogonal to the flow path direction of the cell 2” (hereinafter, “the outer circumference length of the honeycomb structure portion””. It is preferably 0.1 to 5% of (may be referred to as). The opening width of the slit 6 is more preferably 0.1 to 3%, and particularly preferably 0.1 to 1%, of the outer peripheral length of the honeycomb structure portion. If the opening width of the slit 6 is smaller than 0.1% of the outer peripheral length of the honeycomb structure portion, the effect of reducing the thermal shock resistance of the honeycomb structure 100 may be reduced. If the opening width of the slit 6 is larger than 5% of the outer peripheral length of the honeycomb structure portion, the mechanical strength of the honeycomb structure 100 may decrease. The opening width of the slit 6 is the length of the slit 6 in the “circumferential direction of the honeycomb structure portion 4”. The "circumferential direction of the honeycomb structure portion 4" is a direction along the outer circumference in the "cross section orthogonal to the flow path direction of the cell 2" of the honeycomb structure portion 4. When there are a plurality of slits, the opening width of the slits 6 may be different depending on the slits, or all of them may be the same.

In the honeycomb structure 100 of the present embodiment, the length of the slit 6 in the “cell flow path direction” is preferably the same as the length of the honeycomb structure portion in the “cell flow path direction”. That is, it is preferable that the slit 6 is formed between both bottom surfaces of the honeycomb structure portion (over the entire length). It is also preferable that the length of the slit 6 in the “cell flow path direction” is 5 to 70% of the length of the honeycomb structure portion in the “cell flow path direction”. In terms of thermal shock resistance, it is preferable that the entire length is extended, but it is preferable in terms of strength that a part that is not formed remains. If it does not extend over the entire length, one end of the slit is preferably located on the bottom surface of one side of the honeycomb structure. In this case, the slits may be formed only on the bottom surface side of one side of the honeycomb structure portion (see FIG. 10), or may be formed on both bottom surface sides of the honeycomb structure portion (see FIG. 11). ). When the slits are formed on both bottom surfaces of the honeycomb structure, the total length of the slits in the "cell flow path direction" is 5 to 5 of the length of the honeycomb structure in the "cell flow direction". It is preferably 70%. Further, when the slit is formed only on the bottom surface side of one side of the honeycomb structure portion, when the honeycomb structure is used, the bottom surface side on which the slit is formed is used in a direction in which a larger thermal shock is applied. Is preferable. When there are a plurality of slits, the lengths of the slits 6 may differ depending on the slits, or all of them may be the same.

When there are a plurality of slits, the slit formation pattern (including: number), the depth of the slits, the opening width of the slits, and the length of the slits must be line-symmetric with the center line L as the axis of symmetry. Is preferable from the viewpoint of homogeneity.

In the honeycomb structure 100 of the present embodiment, the number of slits 6 is preferably 1 to 20, more preferably 1 to 15, and particularly preferably 1 to 10. If the number of slits 6 exceeds 20, the mechanical strength of the honeycomb structure 100 may decrease. In the honeycomb structure 100 shown in FIGS. 1 and 2, six slits 6 are formed.

In the honeycomb structure 100 of the present embodiment, the slit 6 "the position of the opening (opening of the slit 6) on the outer surface 5 of the outer peripheral side wall 3 is closest to the electrode portion 21" is referred to as the "shortest distance slit" 6a. To. In the "cross section orthogonal to the flow path direction of the cell 2", the shortest distance D along the outer surface 5 of the outer peripheral side wall 3 between the circumferential end of the electrode portion 21 and the circumferential end of the "shortest distance slit" 6a is 0.1 to 30 mm is preferable, 0.5 to 20 mm is more preferable, and 1 to 10 mm is particularly preferable. If the shortest distance D between the electrode portion 21 and the "shortest distance slit" 6a is shorter than 0.1 mm, the current flow may be obstructed and uniform heat generation may be difficult. On the other hand, if the shortest distance D between the electrode portion 21 and the "shortest distance slit" 6a exceeds 30 mm, it may be difficult to obtain the effect of improving the thermal shock resistance of the honeycomb structure 100.

This does not prohibit the formation of the slit 6 in the electrode portion 21, and in order to enhance the thermal shock resistance of the electrode portion 21 and prevent cracks, one or a plurality of slits are provided in each electrode portion 21. You may. When a slit is provided in the electrode portion 21, it is necessary to provide the slit in the central portion C of each of the pair of electrode portions 21 in the circumferential direction in the cross section orthogonal to the flow path direction of the cell 2 of the honeycomb structure 100 to prevent current. Desirable from the perspective of minimizing. In this case, the slit may be formed so as to be covered with the electrode portion 21 inside the electrode portion 21 as described later (see FIG. 13), or may be formed so as to open to the outer surface of the electrode portion 21. It may be (see FIG. 14). From the viewpoint of enhancing the thermal shock resistance of the electrode portion, it is preferable to form a slit that opens on the outer surface of the electrode portion 21. When forming a slit that opens on the outer surface of the electrode portion 21, the slit may have a depth that extends only to the electrode portion 21, or penetrates the electrode portion 21 and extends to the inside of the outer peripheral side wall 3 of the honeycomb structure portion 4. It may be as deep as possible. From the viewpoint of enhancing the thermal shock resistance of the electrode portion, the slit extends between both bottom surfaces of the honeycomb structure portion so that the electrode portion 21 is divided across a slit having an opening extending in the flow path direction of the cell 2. It is preferably formed (over the entire length).

As shown in FIGS. 1 and 2, the honeycomb structure 100 of the present embodiment has two regions (region A and region B) on the side surface 5 of the honeycomb structure portion 4 in which the electrode portion 21 is not arranged. ), Three slits 6 are formed. In the honeycomb structure 100 of the present embodiment, the distance between the opposing slits is longer than the depth of the slits. The distance between the opposing slits is the distance between the slit 6 formed in the region A and the slit 6 formed in the region B.

In the honeycomb structure 100 of the present embodiment, the slit angles of the six slits are all 90 °. Here, the "slit angle" is defined as follows. As shown in FIG. 2, in the cross section orthogonal to the flow path direction of the cell of the honeycomb structure 100 of the present embodiment, the intersection of the slit 6 and the outer periphery of the honeycomb structure portion 4 is defined as a point P. Then, the point P is set as an end point, and a half straight line (or a line segment) extending from the point P toward the outside of the outer periphery of the honeycomb structure portion 4 and parallel to the center line L is defined as a half straight line HL. The center line L is, as described above, a "straight line connecting the central portions of the pair of electrodes". Then, at that time, of the angles formed by the slit 6 and the half straight line HL, the smaller angle (angle of 180 ° or less) is defined as the “slit angle SA”. Here, the "non-large angle" means "the smaller angle, or, if the angles are the same, the same angle". A half straight line is a straight line that has an end on one side and extends infinitely on the other side. Further, "the half straight line HL extends toward the outside of the outer periphery of the honeycomb structure portion 4" means that the half straight line HL extends in a direction that does not pass through the cross section of the honeycomb structure portion 4.

When the filler 7 is filled in the slit 6, the ratio (α2 / α1) of the coefficient of thermal expansion α2 of the filler 7 to the coefficient of thermal expansion α1 of the honeycomb structure 4 is 0.6 to 1.5. preferable. As a result, damage to the honeycomb structure 4 and the filler 7 due to the filler 7 being arranged in the slit 6 can be effectively prevented. For example, if the ratio (α2 / α1) of the coefficient of thermal expansion α2 of the filler 7 to the coefficient of thermal expansion α1 of the honeycomb structure portion 4 is less than 0.6, the honeycomb structure portion 4 is affected by insufficient expansion of the filler. Vertical cracks may occur. When the ratio (α2 / α1) of the coefficient of thermal expansion α2 of the filler 7 to the coefficient of thermal expansion α1 of the honeycomb structure portion 4 is more than 1.5, the bottom surface of the honeycomb structure portion 4 is affected by the excessive expansion of the filler. Cracks may occur. Hereinafter, the "ratio of the coefficient of thermal expansion α2 of the filler 7 to the coefficient of thermal expansion α1 of the honeycomb structure 4 (α2 / α1)" may be referred to as the “coefficient of thermal expansion ratio (α2 / α1)”. In the present invention, unless otherwise specified, the coefficient of thermal expansion means a coefficient of thermal expansion of 25 to 800 ° C.

The filler 7 can contain an aggregate and a neck material. The "neck material" is a material that enters between the aggregate particles and binds and immobilizes the particles. There are no particular restrictions on the material of the neck material. For example, the neck material preferably contains at least one selected from the group consisting of silicon oxide, metal oxides, metals, and metal compounds. Examples of the neck material include the following. The neck material may contain at least one of silicon oxide and a metal oxide, and the neck material may consist of at least one of silicon oxide and a metal oxide. Examples of the metal oxide constituting the neck material include aluminum oxide, titanium oxide, and magnesium oxide.

The filler 7 preferably contains 2 to 90% by mass of the neck material, more preferably 3 to 50% by mass of the neck material, and particularly preferably 5 to 25% by mass of the neck material. If the neck material is less than 2% by mass, the strength of the filler 7 may decrease. If the neck material exceeds 90% by mass, the coefficient of thermal expansion α2 of the filler 7 may increase. Further, if the amount of the neck material is excessive, the strength of the filler 7 may decrease.

The material of the aggregate is also not particularly limited, but preferred components contained in the aggregate include silicon carbide, cordierite, silicon oxide, aluminum titanate, talc, mica, and lithium aluminum titanate, montmorillonite, talc, and boehmite. , At least one component selected from the group consisting of forsterite, kaolin and mullite. The aggregate preferably contains at least one component selected from the above group in a total of 10 to 100% by mass, more preferably 50 to 97% by mass in total, and 75 to 95% by mass in total. It is particularly preferable to include it. A plurality of types of aggregates may be mixed and used.

As shown in FIG. 1, in the honeycomb structure 100 of the present embodiment, the filler 7 is arranged in at least a part of the space of the slit 6. Then, it is preferable that two or more slits 6 are formed in the honeycomb structure portion 4, and a filler is disposed in 50% or more of the two or more slits 6. Further, it is preferable that the filler is arranged in all of the "two or more slits 6" formed in the honeycomb structure portion 4. Further, it is preferable that the filler 7 is arranged in the entire "space of the slit 6". In the honeycomb structure 100 shown in FIG. 1, six slits 6 are formed. Then, in each of the slits 6, the filler 7 is arranged in the entire space of the slit 6. The “arranged in at least a part” may be a “part” in the depth direction of the slit, a “part” in the length direction of the slit, or a combination thereof.

(1-3 Electrode part)
In the honeycomb structure 100 of the present embodiment, the pair of electrode portions 21 have a strip shape on the outer surface 5 of the outer peripheral side wall 3 in the flow path direction of the cell 2 (the direction in which the cell extends) with the central axis of the honeycomb structure portion 4 interposed therebetween. It is extended to. Therefore, when the honeycomb structure 100 of the present embodiment is observed from a cross section orthogonal to the flow path direction of the cell 2, one electrode portion 21 sandwiches the center O of the honeycomb structure portion 4 with respect to the other electrode portion 21. Is arranged on the opposite side (see FIG. 2). As a result, the honeycomb structure 100 can suppress the bias of the current flowing in the honeycomb structure portion 4 when a voltage is applied between the pair of electrode portions 21, and the bias of the temperature distribution in the honeycomb structure portion 4 can be suppressed. It can be suppressed.

"Observing from a cross section orthogonal to the flow path direction of the cell 2, one electrode portion 21 is arranged on the opposite side of the other electrode portion 21 with the center O of the honeycomb structure portion 4 interposed therebetween." The meaning of is as follows. That is, as shown in FIG. 5, first, in the cross section orthogonal to the flow path direction of the cell 2, "the central portion C of one of the electrode portions 21 (the central point in the" circumferential direction of the honeycomb structure portion 4 "). The "line segment connecting the center O of the honeycomb structure portion 4" is defined as the line segment L1. Then, in the cross section orthogonal to the flow path direction of the cell 2, "the central portion C of the other electrode portion 21 (the central point in the" circumferential direction of the honeycomb structure portion 4 ") and the center O of the honeycomb structure portion 4 are connected. Let "line segment" be line segment L2. At that time, a pair of pairs so that the angle β (the angle centered on the “center O”) formed by the line segment L1 and the line segment L2 has a positional relationship in the range of 170 ° to 190 °. It means that the electrode portion 21 is arranged in the honeycomb structure portion 4. In FIG. 5, the partition wall and the slit are omitted.

Further, as shown in FIG. 5, the honeycomb structure 100 of the present embodiment has a cross section orthogonal to the flow path direction of the cell 2, which is 0.5 times the central angle α of each electrode portion 21 (central angle α). The angle θ), which is 0.5 times that of the above, is preferably 15 to 65 °. As a result, the bias of heat generation in the honeycomb structure 4 can be suppressed more effectively. As described above, the shape of the electrode portion 21 in which 0.5 times the central angle α of the electrode portion 21 is 15 to 65 ° and extends in the flow path direction of the cell is one aspect of the “belt shape”. .. Further, as shown in FIG. 5, the “central angle α of the electrode portion 21” is a cross section orthogonal to the flow path direction of the cell, with both ends in the circumferential direction of each electrode portion 21 and the center O of the honeycomb structure portion 4. It is an angle formed by two line segments connecting. In other words, the "central angle α of the electrode portion 21" is a line segment connecting the "electrode portion 21" and "one end of the electrode portion 21 in the circumferential direction and the center O" in a cross section orthogonal to the flow path direction of the cell. It is an internal angle of a portion of the center O in a shape (fan shape, etc.) formed by the “minute” and the “line segment connecting the other end of the electrode portion 21 in the circumferential direction and the center O”.

In the cross section orthogonal to the flow path direction of the cell 2, the upper limit of the “angle θ of 0.5 times the central angle α” of the electrode portion 21 is more preferably 60 °, particularly preferably 55 °. Further, in the cross section orthogonal to the flow path direction of the cell 2, the lower limit value of the "angle θ of 0.5 times the central angle α" of the electrode portion 21 is more preferably 20 °, particularly preferably 30 °. Further, the “angle θ of 0.5 times the central angle α” of one electrode portion 21 is 0.8 to the “angle θ of 0.5 times the central angle α” of the other electrode portion 21. The size is preferably 1.2 times, and more preferably 1.0 times (the same size). As a result, when a voltage is applied between the pair of electrode portions 21, the bias of the current flowing in the honeycomb structure portion 4 can be suppressed, thereby suppressing the bias of the temperature distribution in the honeycomb structure portion 4. it can.

The thickness of the electrode portion 21 is preferably 0.01 to 5 mm, more preferably 0.01 to 3 mm. By setting it in such a range, heat can be generated uniformly. If the thickness of the electrode portion 21 is thinner than 0.01 mm, the electrical resistance becomes high and heat may not be generated uniformly. If it is thicker than 5 mm, it may be damaged during canning. The thickness of the electrode portion 21 is the thickness of the outer surface of the electrode portion 21 in the normal direction with respect to the tangent line at the measurement location when the portion of the electrode portion to be measured is observed in a cross section orthogonal to the flow path direction of the cell. Is defined as.

The electrode portion 21 is preferably made of silicon carbide particles and silicon as main components, and more preferably formed of silicon carbide particles and silicon as raw materials, except for impurities normally contained. Here, "mainly composed of silicon carbide particles and silicon" means that the total mass of the silicon carbide particles and silicon is 90% by mass or more of the total mass of the electrode portion. As described above, since the electrode portion 21 contains silicon carbide particles and silicon as main components, the component of the electrode portion 21 and the component of the honeycomb structure portion 4 are the same or similar components (the material of the honeycomb structure portion is silicon carbide). If there is). Therefore, the coefficients of thermal expansion of the electrode portion 21 and the honeycomb structure portion 4 are the same value or close values. Further, since the materials are the same or similar, the bonding strength between the electrode portion 21 and the honeycomb structure portion 4 is also increased. Therefore, even if thermal stress is applied to the honeycomb structure, it is possible to prevent the electrode portion 21 from peeling off from the honeycomb structure portion 4 and the joint portion between the electrode portion 21 and the honeycomb structure portion 4 from being damaged.

As shown in FIGS. 1 and 2, in the honeycomb structure 100 of the present embodiment, each of the pair of electrode portions 21 is from one bottom surface to the other bottom surface in the flow path direction of the cell of the honeycomb structure portion 4. It is formed in an extending band shape. As described above, since the pair of electrode portions 21 are arranged between both bottom surfaces of the honeycomb structure portion 4, when a voltage is applied between the pair of electrode portions 21, the pair of electrode portions 21 flows in the honeycomb structure portion 4. The bias of the current can be suppressed more effectively. Then, by suppressing the bias of the current flowing in the honeycomb structure portion 4, the bias of the temperature distribution in the honeycomb structure portion 4 can be suppressed more effectively. "Each of the pair of electrode portions 21 is formed in a band shape extending from one bottom surface to the other bottom surface in the direction of the cell flow path of the honeycomb structure portion 4," says one cell flow path of each electrode portion 21. The direction end is in contact with the peripheral edge of the first bottom surface 11 of the honeycomb structure portion 4, and the other end of the electrode portion 21 in the cell flow direction direction is in contact with the peripheral edge of the second bottom surface 12 of the honeycomb structure portion 4. means.

In the honeycomb structure 100 of the present embodiment, it is also preferable that both ends of the electrode portion 21 in the “flow path direction of the cell 2 of the honeycomb structure portion 4” are not in contact with the peripheral edges of both bottom surfaces of the honeycomb structure portion 4. Is. That is, it is also a preferable mode that both ends of the electrode portion 21 do not reach the peripheral edge of the first bottom surface 11 and the peripheral edge of the second bottom surface 12 of the honeycomb structure portion 4. Further, one end in the cell flow path direction of the electrode portion 21 is in contact with the first bottom surface 11 of the honeycomb structure portion 4, and the other end in the cell flow path direction of the electrode portion 21 is the second bottom surface of the honeycomb structure portion 4. A state in which it is not in contact with 12 is also a preferred embodiment. As described above, the form in which the electrode portion 21 is arranged can be variously changed according to the usage form of the honeycomb structure 100.

In the honeycomb structure of the present embodiment, as shown in FIGS. 1 to 3, the electrode portion 21 has a shape in which a planar rectangular member is curved along the outer circumference of the cylindrical shape. There is. Here, the shape when the curved electrode portion 21 is deformed into a non-curved planar member is referred to as the "planar shape" of the electrode portion 21. The "planar shape" of the electrode portion 21 shown in FIGS. 1 to 3 is rectangular. The planar shape of the electrode portion 21 may be a shape in which rectangular corners are formed in a curved shape. Further, the planar shape of the strip-shaped electrode portion 21 may be a shape in which the rectangular corners are chamfered in a straight line.

The electrical resistivity of the electrode portion 21 is preferably lower than that of the honeycomb structure portion 4, and further, the electrical resistivity of the electrode portion 21 is 20% or less of the electrical resistivity of the honeycomb structure portion 4. Is more preferable, and 1 to 10% is particularly preferable. By setting the electrical resistivity of the electrode portion 21 to 20% or less of the electrical resistivity of the honeycomb structure portion 4, the electrode portion 21 functions as an electrode more effectively. Specifically, the electrical resistivity of the electrode portion 21 is preferably 0.1 to 100 Ωcm, more preferably 0.1 to 50 Ωcm. If the electrical resistivity of the electrode portion 21 is smaller than 0.1 Ωcm, the temperature of the honeycomb structure portion near both ends of the electrode portion 21 may easily rise in the cross section orthogonal to the flow path direction of the cell. If the electrical resistivity of the electrode portion 21 is larger than 100 Ωcm, it becomes difficult for current to flow, so that it may be difficult to play a role as an electrode. Here, the electrical resistivity of the electrode portion is a value at 400 ° C. measured by the four-terminal method.

The electrode portion 21 preferably has a porosity of 30 to 60%, more preferably 30 to 55%. When the porosity of the electrode portion 21 is in such a range, a suitable electrical resistivity can be obtained. If the porosity of the electrode portion 21 is lower than 30%, it may be deformed during manufacturing. If the porosity of the electrode portion 21 is higher than 60%, the electrical resistivity may become too high. Porosity is a value measured with a mercury porosimeter.

(1-4 Other Embodiments)
Next, another embodiment of the honeycomb structure of the present invention will be described. As shown in FIG. 6, the honeycomb structure 120 of the present embodiment is different from the honeycomb structure 100 shown in FIG. 1 in that the distance between the opposing slits is shorter than the depth of the slits 6. When the depth of the slit 6 is deepened, the thermal shock resistance is improved, but it becomes difficult for the current to flow, so that uniform heat generation becomes difficult. Therefore, it is preferable to appropriately determine the depth of the slit in consideration of these balances. In the honeycomb structure 120 shown in FIG. 6, all the slits 6 are filled with the filler 7, but the filler 7 may be filled only in a part of the slits 6, or any of the slits 6. It does not have to be filled.

Next, still another embodiment of the honeycomb structure of the present invention will be described. As shown in FIG. 7, the honeycomb structure 130 of the present embodiment has a honeycomb structure shown in FIG. 1 in that the cell shape is hexagonal in a cross section orthogonal to the cell flow path direction. Different from body 100. Hereinafter, the "cell shape" in the cross section orthogonal to the flow path direction of the cell may be simply referred to as "cell shape". When the cell shape is hexagonal, there is an advantage that stress from the outer circumference is dispersed. In the honeycomb structure 130 of the present embodiment, the slit 6 is filled with the filler 7, but the filler 7 may be filled only in a part of the slits 6, or any of the slits 6 is filled. It does not have to be.

Next, still another embodiment of the honeycomb structure of the present invention will be described. As shown in FIG. 8, the honeycomb structure 140 of the present embodiment is the honeycomb structure 130 shown in FIG. 7, in which the slit angle is changed. Specifically, in the cross section orthogonal to the flow path direction of the cell, the depth directions of all six slits are directed toward the central axis of the honeycomb structure portion 4. In the honeycomb structure 140 of the present embodiment, the slit 6 is filled with the filler 7, but the filler 7 may be filled only in a part of the slits 6, or any of the slits 6 is filled. It does not have to be.

Next, still another embodiment of the honeycomb structure of the present invention will be described. As shown in FIG. 9, the honeycomb structure 150 of the present embodiment is the honeycomb structure 130 shown in FIG. 7, in which the depth of the slit is deepened for some of the slits. Specifically, in the honeycomb structure 150 of the present embodiment, the depth of the slit located at the center is deeper among the three slits formed in each of the region A and the region B. is there. In the honeycomb structure 150 of the present embodiment, the slit 6 is filled with the filler 7, but the filler 7 may be filled only in a part of the slits 6, or any of the slits 6 is filled. It does not have to be.

Next, still another embodiment of the honeycomb structure of the present invention will be described. As shown in FIG. 10, the honeycomb structure 160 of the present embodiment is the honeycomb structure 130 shown in FIG. 7 in which the length of the slit 6 in the “flow path direction of the cell 2” is shortened. .. Specifically, the honeycomb structure 160 of the present embodiment is formed so that the slit 6 opens to the side surface 5 and the first bottom surface 11 of the honeycomb structure portion 4 and does not open to the second bottom surface 12. Is. It can also be said that the slit 6 has a structure formed only on one bottom portion of the honeycomb structure portion 4. The length of the slit 6 in the “flow direction of the cell 2” is shorter than the length of the honeycomb structure 4 in the “flow direction of the cell 2”. In the honeycomb structure 160 of the present embodiment, the slit 6 is filled with the filler 7, but the filler 7 may be filled only in a part of the slits 6, or any of the slits 6 is filled. It does not have to be.

Next, still another embodiment of the honeycomb structure of the present invention will be described. As shown in FIG. 11, in the honeycomb structure 170 of the present embodiment, in the honeycomb structure 160 shown in FIG. 10, the slit 6 having a short length in the “flow path direction of the cell 2” is formed in the honeycomb structure portion. It is formed on both bottoms of the cell. In the honeycomb structure 170 of the present embodiment, the slit 6 is filled with the filler 7, but the filler 7 may be filled only in a part of the slits 6, or any of the slits 6 is filled. It does not have to be.

Next, still another embodiment of the honeycomb structure of the present invention will be described. As shown in FIG. 12, the honeycomb structure 190 of the present embodiment is shown in that both ends of the pair of electrode portions 21 in the cell flow path direction are not in contact with the peripheral edge of the bottom surface of the honeycomb structure portion 4. It is different from the honeycomb structure 100 shown in 1. Further, the honeycomb structure 190 shown in FIG. 12 also has a honeycomb structure 100 shown in FIG. 1 in that the planar shape of the strip-shaped electrode portion 21 is a shape in which the rectangular corners are formed in a curved shape. Different from. Further, the honeycomb structure 190 shown in FIG. 12 is different from the honeycomb structure 100 shown in FIG. 1 in that the slit 6 is not filled with the filler 7. The filler 7 may be filled only in a part of the slits 6, or may be filled in all the slits 6.

Next, still another embodiment of the honeycomb structure of the present invention will be described. As shown in FIG. 13, the honeycomb structure 200 of the present embodiment has the electrode portion 21 in the six slits extending in the “cell flow path direction” in the honeycomb structure 140 shown in FIG. The four close slits are formed at positions covered by the electrode portion 21. In the honeycomb structure 200 of the present embodiment, the slit 6 is filled with the filler 7, but the filler 7 may be filled only in a part of the slits 6, or any of the slits 6 is filled. It does not have to be.

Next, still another embodiment of the honeycomb structure of the present invention will be described. As shown in FIG. 14, the honeycomb structure 210 of the present embodiment has an opening extending in the flow path direction of the cell on the outer surface of each electrode portion 21 with respect to the honeycomb structure 140 shown in FIG. It has a configuration in which one or more electrode portion slits 8 are added. In this case, the electrode portion 21 may be divided with the electrode portion slit 8 interposed therebetween. Further, the depth of the slit 8 can extend to the inside of the outer peripheral side wall 3 of the honeycomb structure portion 4. Such an electrode portion slit 8 can be formed after the electrode portion 21 is formed. As a result, the thermal shock resistance of the electrode portion 21 can be improved. In the honeycomb structure 210 of the present embodiment, the slit 8 is filled with the filler 7, but the filler 7 may be filled only in a part of the slits 6, or any of the slits 6 is filled. It does not have to be.

(2) Method for Producing Honeycomb Structure Next, the method for producing the honeycomb structure of the present invention will be exemplified, but the method for producing the honeycomb structure of the present invention is limited to the production method described below. It will not be done. In one embodiment, the method for producing a honeycomb structure of the present invention includes an A1 step of obtaining a honeycomb molded body with an electrode portion raw material, an A2 step of forming a slit, a step A3 of firing the honeycomb molded body, and optional filling. Includes A4 step of filling raw materials for lumber.

The A1 step is a step of applying an electrode portion forming raw material to a honeycomb molded body which is a precursor of a columnar honeycomb structure portion to obtain a honeycomb molded body with an electrode portion raw material. The columnar honeycomb structure includes a partition wall 1 for partitioning a plurality of cells 2 extending from the first bottom surface 11 to the second bottom surface 12, and an outer peripheral side wall 3 located at the outermost periphery, as shown in FIGS. It is a honeycomb structure part 4 having. The honeycomb molded body is a honeycomb structure portion before firing for producing the honeycomb structure portion 4 described above.

The honeycomb molded body can be produced according to the method for producing a honeycomb molded body in the known method for producing a honeycomb structure. For example, first, a molding raw material is prepared by adding metal silicon powder (metal silicon), a binder, a surfactant, a pore-forming material, water, or the like to silicon carbide powder (silicon carbide). It is preferable that the mass of the metallic silicon is 10 to 40% by mass with respect to the total of the mass of the silicon carbide powder and the mass of the metallic silicon. The average particle size of the silicon carbide particles in the silicon carbide powder is preferably 3 to 50 μm, more preferably 3 to 40 μm. The average particle size of metallic silicon (metallic silicon powder) is preferably 2 to 35 μm. The average particle size of silicon carbide particles and metallic silicon (metal silicon particles) refers to the arithmetic mean diameter based on the volume when the frequency distribution of particle size is measured by the laser diffraction method. The silicon carbide particles are fine particles of silicon carbide constituting the silicon carbide powder, and the metallic silicon particles are fine particles of metallic silicon constituting the metallic silicon powder. This is a blending of molding raw materials when the material of the honeycomb structure is silicon-silicon carbide-based composite material, and when the material of the honeycomb structure is silicon carbide, metallic silicon is not added.

Examples of the binder include methyl cellulose, hydroxypropyl methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol and the like. Among these, it is preferable to use methyl cellulose and hydroxypropoxyl cellulose in combination. The binder content is preferably 2.0 to 10.0 parts by mass when the total mass of the silicon carbide powder and the metallic silicon powder is 100 parts by mass.

The water content is preferably 20 to 60 parts by mass when the total mass of the silicon carbide powder and the metallic silicon powder is 100 parts by mass.

As the surfactant, ethylene glycol, dextrin, fatty acid soap, polyalcohol and the like can be used. These may be used individually by 1 type, or may be used in combination of 2 or more type. The content of the surfactant is preferably 0.1 to 2.0 parts by mass when the total mass of the silicon carbide powder and the metallic silicon powder is 100 parts by mass.

The pore-forming material is not particularly limited as long as it becomes pores after firing, and examples thereof include graphite, starch, foamed resin, water-absorbent resin, and silica gel. The content of the pore-forming material is preferably 0.5 to 10.0 parts by mass when the total mass of the silicon carbide powder and the metallic silicon powder is 100 parts by mass. The average particle size of the pore-forming material is preferably 10 to 30 μm. If it is smaller than 10 μm, pores may not be sufficiently formed. If it is larger than 30 μm, it may clog the base during molding. The average particle size of the pore-forming material refers to the arithmetic mean diameter based on the volume when the frequency distribution of particle size is measured by the laser diffraction method. When the pore-forming material is a water-absorbent resin, the average particle diameter of the pore-forming material is the average particle diameter after water absorption.

Next, the obtained molding raw materials are kneaded to form a clay, and then the clay is extruded to produce a honeycomb molded body. In extrusion molding, a mouthpiece having a desired overall shape, cell shape, partition wall thickness, cell density and the like can be used. Although it is necessary to consider expansion and contraction during heating, T ₁ , T ₂ and T ₃ can be basically adjusted by the base structure. Next, it is preferable to dry the obtained honeycomb molded product. Hereinafter, the dried honeycomb molded body may be referred to as a “honeycomb dried body”. When the length in the central axial direction of the honeycomb molded body (or the dried honeycomb body) is not the desired length, both bottom portions of the honeycomb molded body can be cut to obtain the desired length.

Next, a raw material for forming the electrode portion for forming the electrode portion is prepared. When the main components of the electrode portion are silicon carbide and metallic silicon, the electrode portion forming raw material is preferably formed by adding a predetermined additive to the silicon carbide powder and the metallic silicon powder and kneading them. Next, the obtained electrode portion forming raw material is applied to the side surface of the dried honeycomb molded body (honeycomb dried body) to obtain a honeycomb molded body with an electrode portion raw material. The method of blending the electrode portion forming raw material and the method of applying the electrode portion forming raw material to the honeycomb molded body can be performed according to a known method for producing a honeycomb structure, but the electrode portion is compared with the honeycomb structure portion. In order to obtain a low electrical resistance, the content ratio of metallic silicon can be increased or the particle size of the metallic silicon particles can be reduced as compared with the honeycomb structure portion.

As a change example 1 of the method for manufacturing the honeycomb structure, the honeycomb molded body may be fired once before applying the electrode portion forming raw material in the A1 step. That is, in the first modification, the honeycomb molded body is fired to produce a honeycomb fired body, the electrode portion forming raw material is applied to the honeycomb fired body, and the electrode portion raw material is attached instead of the honeycomb molded body with the electrode portion raw material. Obtain a honeycomb fired body.

The A2 step is a step of forming a slit opening on the side surface of the honeycomb molded body with the electrode portion raw material. The slit is preferably formed by using a leutor or the like. The slit is formed so as to open on the side surface of the honeycomb molded body with the electrode portion raw material. As the slit formed in the honeycomb molded body with the electrode portion raw material, a slit similar to the preferred embodiment of the slit formed in the honeycomb structure of the present invention described above is preferable. For example, it is preferable to form a slit similar to the slit 6 formed in the honeycomb structure 100 shown in FIG. 1 in the honeycomb molded body with the electrode portion raw material.

The A3 step is a step of firing a honeycomb molded body with an electrode portion raw material to obtain a honeycomb fired body. Before firing, the honeycomb molded body with the electrode portion raw material may be dried. Further, prior to firing, temporary firing may be performed in order to remove binders and the like in the raw material for the filler. As the firing conditions, it is preferable to heat at 1400 to 1500 ° C. for 1 to 20 hours in an inert atmosphere such as nitrogen or argon. Further, after firing, it is preferable to carry out an oxidation treatment at 1200 to 1350 ° C. for 1 to 10 hours in order to improve durability. The method of tentative firing and firing is not particularly limited, and firing can be performed using an electric furnace, a gas furnace, or the like.

The A4 step is a step of filling the slit formed in the honeycomb fired body with the raw material for the filler. The A4 step is not essential, but it is a necessary step when filling the slit with the filler. In the A4 step, first, a raw material for a filler is prepared. The raw material for the filler is a raw material for producing the filler in the honeycomb structure of the present invention described above. For example, the raw material for a filler can be obtained by kneading a mixture obtained by mixing an aggregate, a neck material, a binder, a surfactant, a pore-forming material, water and the like. The raw material for the filler is preferably in the form of a slurry. It is preferable that the aggregate and the neck material contained in the raw material for the filler are the same as those in the preferred embodiment of the filler in the honeycomb structure of the present invention described so far.

The content ratio of the aggregate in the raw material for the filler and the content ratio of the neck material in the raw material for the filler are preferably the same as those in the preferred embodiment of the filler in the honeycomb structure of the present invention. The content ratio of the aggregate and the content ratio of the neck material can be appropriately adjusted to be in a preferable numerical range at the stage of preparing the raw material for the filler. The average particle size of the aggregate is also preferably the same as that of the preferred embodiment of the filler in the honeycomb structure of the present invention, and when preparing the raw material for the filler, an aggregate having a preferable average particle size is selected. Can be used.

Examples of the binder used as a raw material for a filler include methyl cellulose, hydroxypropyl methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, glycerin and the like. Among these, it is preferable to use methyl cellulose and hydroxypropoxyl cellulose in combination. The binder content is preferably 0 to 25 parts by mass when the total mass of the aggregate and the neck material is 100 parts by mass.

The water content is preferably 15 to 75 parts by mass when the total mass of the aggregate and the neck material is 100 parts by mass.

As the surfactant used as the raw material for the filler, ethylene glycol, dextrin, fatty acid soap, polyalcohol and the like can be used. These may be used individually by 1 type, or may be used in combination of 2 or more type. The content of the surfactant is preferably 0 to 15 parts by mass when the total mass of the aggregate and the neck material is 100 parts by mass.

The pore-forming material used as a raw material for a filler is not particularly limited as long as it becomes pores after firing, and examples thereof include graphite, starch, foamed resin, water-absorbent resin, and silica gel. The content of the pore-forming material is preferably 0 to 85 parts by mass when the total mass of the aggregate and the neck material is 100 parts by mass. The average particle size of the pore-forming material is preferably 3 to 150 μm. If it is smaller than 3 μm, pores may not be sufficiently formed. If it is larger than 150 μm, air pores are likely to be formed, which may cause a decrease in strength. The average particle size of the pore-forming material refers to the arithmetic mean diameter based on the volume when the frequency distribution of particle size is measured by the laser diffraction method.

The method of filling the slit formed in the honeycomb molded body with the electrode portion raw material with the raw material for the filler is not particularly limited, and examples thereof include a method of filling the slit with the raw material for the filler using a syringe or the like. .. According to such a method, the raw material for the filler can be uniformly filled in the slit. Of course, the raw material for the filler may be filled in the slit using a spatula or the like.

By heat-treating the honeycomb structure filled with the raw material for the filler, the filler can be made uniform. The heat treatment conditions can be, for example, 2 to 12 hours at a temperature of 50 to 100 ° C. in an air atmosphere.

Hereinafter, examples for better understanding the present invention and its advantages will be illustrated, but the present invention is not limited to the examples.

<Example 1>
(1) Preparation of Honeycomb Structure A ceramic raw material was prepared by mixing silicon carbide (SiC) powder and metallic silicon (Si) powder at a mass ratio of 80:20. Then, hydroxypropyl methylcellulose as a binder and a water-absorbent resin as a pore-forming material were added to the ceramic raw material, and water was added to prepare a molding raw material. Then, the molding raw material was kneaded with a vacuum clay kneader to prepare a columnar clay. The binder content was 7 parts by mass when the total of the silicon carbide (SiC) powder and the metallic silicon (Si) powder was 100 parts by mass. The content of the pore-forming material was 3 parts by mass when the total of the silicon carbide (SiC) powder and the metallic silicon (Si) powder was 100 parts by mass. The water content was 42 parts by mass when the total of the silicon carbide (SiC) powder and the metallic silicon (Si) powder was 100 parts by mass. The average particle size of the silicon carbide powder was 20 μm, and the average particle size of the metallic silicon powder was 6 μm. The average particle size of the pore-forming material was 20 μm. The average particle size of silicon carbide, metallic silicon, and pore-forming material refers to the arithmetic mean diameter based on the volume when the frequency distribution of particle size is measured by the laser diffraction method.

The obtained columnar clay was molded using an extrusion molding machine to obtain a columnar honeycomb molded body having a regular hexagonal cross-sectional shape of each cell. In extrusion molding, T ₁ , T ₂ , and T ₃ of the honeycomb structure, and a base having a structure in which the aperture ratio in the central portion / the aperture ratio in the outer peripheral portion = the aperture ratio ratio are as shown in Table 1 were used. ..

The obtained honeycomb molded body was dried by high-frequency dielectric heating and then dried at 120 ° C. for 2 hours using a hot air dryer, and both bottom surfaces were cut by a predetermined amount to prepare a dried honeycomb body.

Next, silicon carbide (SiC) powder and metallic silicon (Si) powder were mixed at a mass ratio of 60:40, to which hydroxypropylmethyl cellulose was added as a binder, glycerin as a moisturizer, and a surfactant as a dispersant. At the same time, water was added and mixed. The mixture was kneaded with a vertical stirrer to prepare an electrode portion forming raw material. The binder content is 0.5 parts by mass when the total of silicon carbide (SiC) powder and metallic silicon (Si) powder is 100 parts by mass, and the glycerin content is silicon carbide (SiC) powder and metallic silicon. When the total of the (Si) powder is 100 parts by mass, it is 10 parts by mass, and the content of the surfactant is when the total of the silicon carbide (SiC) powder and the metallic silicon (Si) powder is 100 parts by mass. It was 0.3 parts by mass, and the water content was 42 parts by mass when the total of the silicon carbide (SiC) powder and the metallic silicon (Si) powder was 100 parts by mass. The average particle size of the silicon carbide powder was 10 μm, and the average particle size of the metallic silicon powder was 6 μm. The average particle size of silicon carbide and metallic silicon refers to the arithmetic mean diameter based on the volume when the frequency distribution of particle size is measured by the laser diffraction method.

Next, the electrode portion forming raw material was placed on the side surface (outer surface of the outer peripheral side wall) of the dried honeycomb body with a thickness of 0.15 mm and "0.5 times the central angle is 50 ° in the cross section orthogonal to the flow path direction of the cell". The columnar honeycomb dried body was coated at two locations in a strip shape over the entire length between both bottom surfaces. The two electrode portion-forming raw material coating portions were arranged so as to be on opposite sides of the central axis of the honeycomb dried body.

Next, the electrode portion-forming raw material applied to the dried honeycomb body was dried to obtain a dried honeycomb body with an unfired electrode portion. The drying temperature was 70 ° C.

Next, with respect to the dried honeycomb body with the unfired electrode portion, as shown in FIG. 8, one of the outer surfaces of the two opposite outer peripheral side walls where the electrode portion 21 is not arranged is in the flow path direction of the cell. A total of 6 slits were formed, each having an opening extending from the bottom surface of the honeycomb to the other bottom surface and having a depth in the direction toward the central axis of the dried honeycomb. The slit was formed using a lutor. Next, the dried honeycomb body with the unfired electrode portion on which the slit was formed was degreased (temporarily fired), fired, and further oxidized to obtain a honeycomb structure. The degreasing conditions were 550 ° C. for 3 hours under an oxidizing atmosphere. The firing conditions were 1450 ° C. for 2 hours under an argon atmosphere. The conditions for the oxidation treatment were 1300 ° C. and 1 hour under an oxidizing atmosphere.

(2) Specifications of the obtained honeycomb structure The obtained honeycomb structure had a circular shape with a bottom surface of 93 mm in diameter and a substantially cylindrical shape having a length of 75 mm in the flow path direction of the cell.
The shape of the cell in the cross section orthogonal to the flow path direction of the cell was a regular hexagon.
The cell pitch was 1.11 mm. The cell pitch is the distance between the central portions of adjacent parallel bulkheads (bulkheads constituting the two opposite sides of a regular hexagon) in the thickness (bulkhead thickness) direction. The central portion in the thickness direction of the partition wall is the central position in the thickness direction of the partition wall.
The average thickness T ₁ of the outer peripheral side wall was 0.35 mm.
A plurality of cells adjacent to the inner surface of each slit are set as the first cell, and the thickness T ₂ of the partition wall portion forming the cells from the first to the third cells in the order closer to the inner surface of the slit is 0. It was 15 mm.
In a cross section orthogonal to the flow path direction of the cells, a plurality of cells adjacent to the inner surface of each slit are set as the first cell, and a partition wall forming a cell farther than the tenth from the inner surface of any slit. The thickness T ₃ of the portion was 0.20 mm in all the partition walls.
The depth of each slit was 3 mm. The opening width of the slit was 1 mm. The angle between the three adjacent slits was 30 °. The distance D between the electrode portion 21 and the "shortest distance slit" was 1 mm.
The opening ratio of the central portion of the honeycomb structure was 71.8%, and the opening ratio of the outer peripheral portion was 75.8%. Therefore, the value of the ratio of the opening ratio of the central portion to the opening ratio of the outer peripheral portion (opening ratio of the central portion / opening ratio of the outer peripheral portion = opening ratio ratio) was 0.95. The "aperture ratio" is a value obtained by dividing the cell area by the total area of the partition wall and the cell in the cross section orthogonal to the flow path direction of the cell (total cell area / (total cell area + total partition wall area). )) Indicates a value expressed as a percentage.
0.5 times the central angle of the two electrode portions of the honeycomb structure in the cross section orthogonal to the flow path direction of the cell was 50 °. The thickness of the two electrode portions was 0.15 mm. The electrical resistivity of the electrode portion was 1.3 Ωcm.
In the cross section orthogonal to the flow path direction of the cell, the slit and the "straight line connecting the central portions of the pair of electrode portions" (center line) did not intersect.
The average pore diameter (pore diameter) of the partition wall of the obtained honeycomb structure was 8.6 μm, and the porosity was 45%. The average pore size and porosity are values measured by a mercury porosimeter.
The isostatic strength of the honeycomb structure was 2.5 MPa. Isostatic strength is the fracture strength measured by applying hydrostatic pressure in water.

(3) Heat and Impact Resistance of the Obtained Honeycomb Structure The heat and shock resistance of the obtained honeycomb structure was evaluated by the following method. A heating and cooling test of the honeycomb structure was carried out using a "propane gas burner testing machine equipped with a metal case for storing the honeycomb structure and a propane gas burner capable of supplying heating gas into the metal case". did. The heating gas was a combustion gas generated by burning propane gas with a gas burner (propane gas burner). Then, the thermal shock resistance was evaluated by confirming whether or not cracks were generated in the honeycomb structure by the above heating and cooling test. Specifically, first, the obtained honeycomb structure was stored (canned) in the metal case of the propane gas burner testing machine. Then, the gas (combustion gas) heated by the propane gas burner was supplied into the metal case so as to pass through the honeycomb structure. The temperature conditions (inlet gas temperature conditions) of the heating gas flowing into the metal case were as follows. First, the temperature was raised to 950 ° C. in 5 minutes and held at 950 ° C. for 10 minutes, then cooled to 100 ° C. in 5 minutes and held at 100 ° C. for 10 minutes. A series of such a series of heating, holding, cooling, and holding was repeated 500 times. After that, it was confirmed whether or not cracks were generated on both bottom surfaces and side surfaces of the honeycomb structure. If no cracks are confirmed, the heat and shock resistance test is passed (A evaluation), and if cracks are confirmed, the heat and shock resistance test is rejected. For the honeycomb structure that passed the thermal shock resistance test, the above cooling operation was further repeated. The case where no crack is confirmed even after repeating the operation 1000 times or more from the first cycle is evaluated as AAA, and the case where no crack is confirmed even after repeating the operation 2000 times or more from the first cycle is evaluated as AAA. The case where no crack was confirmed even after repeating the operation 3000 times or more from the cycle was defined as AAAA evaluation. The results are shown in Table 1.

<Examples 2 to 9 (however, Examples 3 to 5, 7 and 8 are reference examples) , Comparative Examples 1 to 5>
By changing the base structure at the time of extrusion molding, T ₁ , T ₂ , and T ₃ , and the aperture ratio ratio are changed according to the test numbers as shown in Table 1, but the same as in Example 1. A honeycomb structure was produced. The heat-resistant impact resistance test was performed on each of the produced honeycomb structures in the same manner as in Example 1. The results are shown in Table 1.

<Example 10>
Raw materials for fillers were prepared. First, a neck material made of silica, an aggregate made of silicon carbide, and an aggregate made of cordierite were mixed. Hereinafter, the aggregate made of silicon carbide may be referred to as "SiC aggregate". An aggregate made of cordierite is sometimes called "Cd aggregate". The neck material, SiC aggregate, and Cd aggregate were mixed so as to have a mass ratio of 12: 6: 82 (neck material: SiC aggregate: Cd aggregate). Hydroxypropyl methylcellulose as a binder, glycerin as a moisturizer, a surfactant as a dispersant, and a pore-forming material were added thereto, and water was added and mixed. The mixture was kneaded with a vertical stirrer to prepare a raw material for a filler. The binder content was 1.0 part by mass when the total of the neck material, SiC aggregate and Cd aggregate was 100 parts by mass. The content of glycerin was 4.0 parts by mass when the total of the neck material, SiC aggregate and Cd aggregate was 100 parts by mass. The content of the surfactant was 0.3 parts by mass when the total of the neck material, the SiC aggregate and the Cd aggregate was 100 parts by mass. The content of the pore-forming material was 6.7 parts by mass when the total of the neck material, the SiC aggregate and the Cd aggregate was 100 parts by mass. The water content was 34.5 parts by mass when the total of the neck material, SiC aggregate and Cd aggregate was 100 parts by mass. The average particle size of the SiC aggregate used as the raw material for the filler was 3 μm. The average particle size of the Cd aggregate used as the raw material for the filler was 8 μm. The average particle size of SiC aggregate and Cd aggregate refers to the arithmetic mean diameter based on the volume when the frequency distribution of particle size is measured by the laser diffraction method.

Next, the obtained raw material for the filler was filled into the slit of the honeycomb structure produced in the same procedure as in Example 1 to obtain a honeycomb structure filled with the raw material for the filler. When filling the raw material for the filler, the raw material for the filler was introduced into a syringe, and the filler was filled (injected) into the slit using this syringe. The raw material for the filler was filled in all six slits. The filling amount of the raw material for the filler was set to be equivalent to the slit volume.

Next, the obtained honeycomb structure filled with the raw material for the filler was heat-treated at a temperature of 1225 ° C. The heat treatment was performed in an atmospheric atmosphere. The heat treatment time was 1 hour. In this way, the honeycomb structure of Example 10 was produced. A thermal shock resistance test was performed on the produced honeycomb structure in the same manner as in Example 1. The results are shown in Table 1.

<Discussion>
Since the ratio of T ₁ to T ₂ was appropriate in Examples 1 to 9, it can be seen that the thermal shock resistance was improved as compared with Comparative Examples 1 to 5. Further, in Examples 1, 9 and 10 in which the ratio of T ₁ to T ₂ was optimized, the thermal shock resistance was further improved. Comparing Example 1 and Example 9, Example 9 was superior in thermal shock resistance because the aperture ratio ratio was optimized. Comparing Example 1 and Example 10, in Example 10, the heat-resistant impact resistance was improved by filling the slit with the filler. In the comparative example, all the cracks generated on the bottom surface started from the vicinity of the deepest part of the slit.

1: Partition, 2: Cell, 3: Outer side wall, 4: Honeycomb structure, 5: Outer surface of outer side wall, 6: Slit, 6a: Shortest distance slit, 7: Filler, 8: Slit, 11: First bottom surface (Bottom surface), 12: Second bottom surface (bottom surface), 21: Electrode part, 100, 120, 130, 140, 150, 160, 170, 190, 200: Honeycomb structure, O: Center, C: (Electronic part ) Circumferential central part, L: center line, L1, L2: line segment, α: central angle, β: angle, θ: angle 0.5 times the central angle, A, B: region, D: distance, P : Intersection, SA: Slit angle, HL: Half straight line

Claims (10)

A columnar honeycomb structure having an outer peripheral side wall and a partition wall arranged inside the outer peripheral side wall and partitioning a plurality of cells forming a flow path from one bottom surface to the other bottom surface.
A pair of electrode portions extending in a band shape in the cell flow path direction on the outer surface of the outer peripheral side wall with the central axis of the honeycomb structure portion in between, and
One or more slits with openings extending in the cell flow direction on the outer surface of the outer sidewall,
It is a conductive honeycomb structure equipped with
In the cross section orthogonal to the flow path direction of the cells, the average thickness of the outer peripheral side wall is T _1, and the plurality of cells adjacent to the inner surface of each slit are each the first cell, and the first to third cells are in the order of proximity to the inner surface of each slit. A conductive honeycomb structure in which the relational expression of 1.8 ≤ T ₁ / T ₂ ≤ 3.0 always holds, where T ₂ is the thickness of the partition wall that partitions the cells up to the third. The conductive honeycomb structure according to claim 1, wherein the relational expression of 1.8 ≤ T ₁ / T ₂ ≤ 2.8 always holds. 1.8 ≤ T ₁ / T ₂ The conductive honeycomb structure according to claim 1, wherein the relational expression of ≤2.5 always holds. The conductive honeycomb structure according to any one of claims 1 to 3, wherein 0.1 mm ≤ T ₁ ≤ 0.5 mm. The conductive honeycomb structure according to any one of claims 1 to 4 , wherein 0.1 mm ≤ T ₂ ≤ 0.3 mm. In a cross section orthogonal to the flow path direction of the cells, a plurality of cells adjacent to the inner surface of each slit are set as the first cell, and a partition wall forming a cell farther than the tenth from the inner surface of any slit. The conductive honeycomb structure according to any one of claims 1 to 5 , wherein the relational expression of T ₂ > T ₃ always holds, where T ₃ is the thickness of the portion. The conductive honeycomb structure according to claim 6 , wherein 0.08 mm ≤ T ₃ ≤ 0.3 mm. The honeycomb structure according to claim 6 or 7 , wherein the relational expression of 1.0 ≤ T ₁ / T ₃ ≤ 2.5 always holds. In the cross section orthogonal to the flow path direction of the cell, the region from the center to the outer surface of the outer peripheral side wall toward the position of 10% of the length from the center to the outer surface of the outer peripheral side wall is the central portion, and the outer surface of the outer peripheral side wall is The opening ratio of the central portion is 0.70 to 0 of the opening ratio of the outer peripheral portion, when the region from the outer surface of the outer peripheral side wall to the position of 10% of the length from the outer surface to the center is defined as the outer peripheral portion. The conductive honeycomb structure according to any one of claims 1 to 8 , which is .95 times. The conductive honeycomb structure according to any one of claims 1 to 9 , wherein at least a part of the internal space of the one or more slits is filled with a filler.