Honeycomb structure and exhaust gas purification device

Abstract

To provide a honeycomb structure and an exhaust gas purification device capable of suppressing displacement of a honeycomb structure from a can body due to shear displacement of a buffer member while avoiding a reduction in strength of a honeycomb structure.SOLUTION: There is provided a honeycomb structure 1 comprising a honeycomb structure part 10 which has an outer peripheral wall and a partition wall for partitioning a plurality of cells forming a flow channel extending from one end face to the other end face and at least one electrode layer 11 provided on an outer surface of the outer peripheral wall, wherein the electrode layer 11 is formed so that the thickness varies in the extension direction of the cells and the honeycomb structure 1 is formed so that the outer diameter varies in the extension direction of the cells due to the variation in thickness of the electrode layer 11.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a honeycomb structure and an exhaust gas purification device. [Background technology]

[0002] For example, methods of suppressing slippage of a honeycomb structure from a can body have been studied, as disclosed in the following Patent Documents 1 and 2. Patent Document 1 discloses a configuration in which the surface roughness of the outer peripheral wall is increased to increase the friction coefficient of the outer peripheral wall surface and effectively suppress slippage of the honeycomb structure within the can body. Patent Document 2 discloses a configuration in which the outer peripheral surface of the outer peripheral wall has a reference surface with an external tolerance of within ±1.0 mm and an uneven portion that is concave or convex with respect to the reference surface to suppress slippage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-130184 A [Patent Document 2] JP 2005-125182 A Summary of the Invention [Problem to be solved by the invention]

[0004] Between the honeycomb structure and the can body, a cushioning member such as a non-expanding ceramic fiber mat or a thermally expandable mineral material mat is disposed. When the honeycomb structure is mounted on a vehicle, a specific portion of the honeycomb structure repeatedly undergoes thermal expansion, and loads are concentrated at corresponding portions of the cushioning member, which may cause shear displacement of the cushioning member. When shear displacement occurs in the cushioning member, the gripping force of the honeycomb structure by the cushioning member decreases, increasing the possibility that the honeycomb structure will shift and fall off the can body.

[0005] Patent Documents 1 and 2 do not take into consideration the shear displacement of the buffer member caused by thermal expansion of the honeycomb structure. Although it may be possible to suppress the shear displacement of the buffer member by adjusting the position of the uneven portion in Patent Document 2, when the thickness of the outer peripheral wall is partially changed, there is a risk that deformation will occur in the cells on the inside of the outer peripheral wall during the manufacture of the honeycomb structure, resulting in a decrease in the strength of the honeycomb structure.

[0006] The present invention has been made to solve the above-mentioned problems, and one of its objectives is to provide a honeycomb structure and an exhaust gas purification device that can suppress displacement of the honeycomb structure from the can body due to shear displacement of the cushioning member while avoiding a decrease in the strength of the honeycomb structure. [Means for solving the problem]

[0007] Item 1. In one embodiment, the present invention relates to a honeycomb structure including: a honeycomb structure portion having an outer peripheral wall; partition walls disposed inside the outer peripheral wall and defining a plurality of cells forming flow paths extending from one end face to the other end face; and at least one electrode layer provided on an outer surface of the outer peripheral wall, wherein the electrode layer is formed so that its thickness varies in the extension direction of the cells, and the honeycomb structure is formed so that its outer diameter varies in the extension direction of the cells due to the variation in the thickness of the electrode layer.

[0008] Item 2. The present invention may relate to the honeycomb structure according to Item 1, wherein the honeycomb structure includes a first region, a second region, and a third region aligned in an extension direction of the cells, the first region being disposed on one end face side, the third region being disposed on the other end face side, and the second region being disposed between the first region and the third region, and one of an outer diameter of the first region, an outer diameter of the second region, and an outer diameter of the third region being different from the other one or two due to a variation in thickness of the electrode layer.

[0009] Item 3. The present invention provides a method for manufacturing a gyro having a smallest outer diameter (R min ) for the maximum outer diameter (R max ) ratio (R max / R min) is greater than 1.000 and less than 1.061.

[0010] Item 4. The present invention relates to a ratio (R max / R min ) is 1.001 or more and 1.052 or less.

[0011] Item 5. The present invention relates to a ratio (R max / R min 5. The honeycomb structure according to claim 4, wherein the ratio of the surface area to the surface area of ​​the honeycomb structure is 1.010 or more and 1.048 or less.

[0012] Item 6. The present invention relates to a ratio (R max / R min ) is 1.014 or more and 1.042 or less.

[0013] Item 7. The present invention provides a method for forming a first region having an outer diameter R A The outer diameter of the second region is R B The outer diameter of the third region is R C Then, R A ≦R C <R B or R C ≦R A <R B The present invention may relate to a honeycomb structure according to any one of items 2 to 6.

[0014] Item 8. The present invention relates to an exhaust gas purification device comprising: the honeycomb structure according to any one of Items 1 to 7; a metal electrode connected to an electrode layer of the honeycomb structure; a metal can body that holds the honeycomb structure; and a buffer member disposed between the honeycomb structure and the can body, wherein an inner diameter of the can body at an outer periphery of the honeycomb structure is constant in an extension direction of the cells. Effect of the Invention

[0015] According to one embodiment of the honeycomb structure and exhaust gas purification device of the present invention, the honeycomb structure is formed so that its outer diameter varies in the extension direction of the cells due to variations in the thickness of the electrode layer, thereby making it possible to suppress displacement of the honeycomb structure from the can body due to shear displacement of the cushioning member while avoiding a decrease in strength of the honeycomb structure. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view showing a honeycomb structure of an electrically heated carrier according to an embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view of an exhaust gas purification device including the honeycomb structure of FIG. 1. [Diagram 3] FIG. 2 is an explanatory view showing a first embodiment of the honeycomb structure of FIG. [Figure 4] FIG. 2 is an explanatory view showing a second embodiment of the honeycomb structure of FIG. [Diagram 5] FIG. 2 is an explanatory view showing a third embodiment of the honeycomb structure of FIG. [Figure 6] 10 is an explanatory diagram showing thermal expansion of a honeycomb structure having a constant outer diameter as a comparative example when the honeycomb structure is mounted on a hybrid vehicle or a plug-in hybrid vehicle. FIG. [Figure 7] 4 is an explanatory view showing thermal expansion of a honeycomb structure such as the drum-shaped honeycomb structure of FIG. 3 when it is mounted on a hybrid vehicle or a plug-in hybrid vehicle. FIG. [Figure 8] 1 is a graph showing the relationship between the ratio Rmax / Rmin of the maximum outer diameter Rmax to the minimum outer diameter Rmin and the amount of displacement of the honeycomb structure in a displacement test of the honeycomb structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, the embodiments for carrying out the present invention will be described with reference to the drawings. The present invention is not limited to each embodiment, and the components can be modified and embodied without departing from the gist of the present invention. In addition, various inventions can be formed by appropriately combining multiple components disclosed in each embodiment. For example, some components may be deleted from all the components shown in the embodiments. Furthermore, components of different embodiments may be appropriately combined.

[0018] FIG. 1 is a perspective view showing a honeycomb structure 1 of an electrically heated carrier according to an embodiment of the present invention. The honeycomb structure 1 shown in FIG. 1 constitutes a part of the electrically heated carrier. The electrically heated carrier is capable of raising the temperature of a catalyst supported on the honeycomb structure 1 to an active temperature before starting the engine by causing the honeycomb structure 1 to generate heat when electricity is passed through it. The electrically heated carrier is provided, for example, in the exhaust path of an automobile or the like, and can be used to purify exhaust gas discharged from the engine.

[0019] The honeycomb structure 1 has a honeycomb structure part 10 and at least one electrode layer 11.

[0020] The honeycomb structure section 10 is a columnar member made of ceramics, and has an outer peripheral wall 100 and partition walls 101 disposed inside the outer peripheral wall 100 and partitioning a plurality of cells 101a that form flow paths extending from one end face to the other end face. The columnar shape can be understood as a three-dimensional shape having a thickness in the extension direction of the cells 101a (axial direction of the honeycomb structure section 10). The ratio (aspect ratio) of the axial length of the honeycomb structure section 10 to the diameter or width of the end face of the honeycomb structure section 10 is arbitrary. The columnar shape may include a shape (flat shape) in which the axial length of the honeycomb structure section 10 is shorter than the diameter or width of the end face.

[0021] The outer shape of the honeycomb structure 10 is not particularly limited as long as it is columnar, and may be, for example, a columnar shape with a circular end face (cylindrical shape), a columnar shape with an oval end face, or a columnar shape with a polygonal end face (quadragonal, pentagonal, hexagonal, heptagonal, octagonal, etc.). The size of the honeycomb structure 10 is set to an end face area of ​​2000 to 20000 mm for the reason of increasing heat resistance (suppressing cracks in the circumferential direction of the outer peripheral wall 100). 2 It is preferable that the thickness is 5000 to 15000 mm. 2 It is more preferable that:

[0022] Although there is no limitation on the shape of the cells 101a in a cross section perpendicular to the extending direction of the cells 101a, a square, a hexagon, an octagon, or a combination of these is preferable. Among these, a square and a hexagon are more preferable. By using such a cell shape, the pressure loss when exhaust gas flows through the honeycomb structure portion 10 is reduced, and the purification performance of the catalyst is improved.

[0023] The thickness of the partition walls 101 that define the cells 101a is preferably 0.1 to 0.3 mm, and more preferably 0.1 to 0.2 mm. When the thickness of the partition walls 101 is 0.1 mm or more, it is possible to suppress a decrease in the strength of the honeycomb structure section 10. When the thickness of the partition walls 101 is 0.3 mm or less, it is possible to suppress an increase in pressure loss when exhaust gas flows through the honeycomb structure section 10 when the honeycomb structure section 10 is used as a catalyst carrier to support a catalyst. In the present invention, the thickness of the partition walls 101 is defined as the length of a portion that passes through the partition walls 101, of a line segment that connects the centers of gravity of adjacent cells 101a, in a cross section perpendicular to the extension direction of the cells 101a.

[0024] The honeycomb structure 10 has a cell density of 40 to 150 cells / cm in a cross section perpendicular to the extending direction of the cells 101a. 2 Preferably, the cell density is 70 to 100 cells / cm. 2 By setting the cell density in this range, it is possible to increase the purification performance of the catalyst while reducing the pressure loss when exhaust gas flows through it.2 If the cell density is 150 cells / cm or more, the catalyst carrying area is sufficiently secured. 2 When the honeycomb structure section 10 is used as a catalyst carrier to support a catalyst, the pressure loss caused when exhaust gas flows through the honeycomb structure section 10 is prevented from becoming too large if the honeycomb structure section 10 is used as a catalyst carrier to support a catalyst, and the cell density is a value obtained by dividing the number of cells by the area of ​​one end face portion of the honeycomb structure section 10 excluding the outer peripheral wall 100 portion.

[0025] Providing the outer peripheral wall 100 on the honeycomb structure 10 is useful from the viewpoint of ensuring the structural strength of the honeycomb structure 10 and suppressing leakage of the fluid flowing through the cells 101a from the outer peripheral wall 100. Specifically, the thickness of the outer peripheral wall 100 is preferably 0.05 mm or more, more preferably 0.10 mm or more, and even more preferably 0.15 mm or more. However, if the outer peripheral wall 100 is made too thick, it becomes too strong, and the strength balance with the partition walls 101 is lost, resulting in a decrease in thermal shock resistance. Therefore, the thickness of the outer peripheral wall 100 is preferably 1.0 mm or less, more preferably 0.7 mm or less, and even more preferably 0.5 mm or less. Here, the thickness of the outer peripheral wall 100 is defined as the thickness in the normal direction to the tangent of the outer peripheral wall 100 at the measurement point when the portion of the outer peripheral wall 100 to be measured for thickness is observed in a cross section perpendicular to the extension direction of the cells 101a.

[0026] The honeycomb structure section 10 is preferably made of ceramics and has electrical conductivity. There is no particular limitation on the volume resistivity of the honeycomb structure section 10 as long as it can generate heat by Joule heat when electricity is applied, but it is preferably 0.1 to 200 Ωcm, and more preferably 1 to 200 Ωcm. In the present invention, the volume resistivity of the honeycomb structure section 10 is a value measured at 25°C by a four-terminal method.

[0027] The material of the honeycomb structure part 10 is not limited, and may be selected from the group consisting of oxide ceramics such as alumina, mullite, zirconia, and cordierite, and non-oxide ceramics such as silicon carbide, silicon nitride, and aluminum nitride. A silicon-silicon carbide composite material, a silicon carbide / graphite composite material, and the like may also be used. Among these, from the viewpoint of achieving both heat resistance and electrical conductivity, it is preferable that the material of the honeycomb structure part 10 contains a silicon-silicon carbide composite material or a ceramic containing silicon carbide as a main component. When the material of the honeycomb structure part 10 is said to contain a silicon-silicon carbide composite material as a main component, it means that the honeycomb structure part 10 contains 90 mass% or more of the silicon-silicon carbide composite material (total mass) of the entirety. Here, the silicon-silicon carbide composite material contains silicon carbide particles as aggregate and silicon as a binder for binding the silicon carbide particles, and it is preferable that a plurality of silicon carbide particles are bound by silicon so as to form pores between the silicon carbide particles. When it is said that the material of the honeycomb structure part 10 is mainly composed of silicon carbide, it means that the honeycomb structure part 10 contains silicon carbide (total mass) in an amount of 90 mass% or more of the entire material.

[0028] When the honeycomb structure 10 contains a silicon-silicon carbide composite material, the ratio of the "mass of silicon as a binder" contained in the honeycomb structure 10 to the sum of the "mass of silicon carbide particles as aggregate" contained in the honeycomb structure 10 and the "mass of silicon as a binder" contained in the honeycomb structure 10 is preferably 10 to 40 mass%, and more preferably 15 to 35 mass%.

[0029] The outer peripheral wall 100 and the partition walls 101 may be porous. If they are porous, the porosity of the outer peripheral wall 100 and the partition walls 101 is preferably 35 to 60%, and more preferably 35 to 45%. The porosity is a value measured by a mercury porosimeter. Furthermore, the outer peripheral wall 100 and the partition walls 101 may be dense, and if they are dense, the porosity of the outer peripheral wall 100 and the partition walls 101 may be 10% or less, or 5% or less.

[0030] The average pore diameter of the outer peripheral wall 100 and the partition walls 101 of the honeycomb structure portion 10 is preferably 2 to 15 μm, and more preferably 4 to 8 μm. The average pore diameter is a value measured by a mercury porosimeter.

[0031] At least one electrode layer 11 is provided on the outer surface of the peripheral wall 100. The electrode layer 11 may extend from one end to the other end of the honeycomb structure section 10 in the extending direction of the cells 101a. The electrode layer 11, together with the peripheral wall 100, constitutes the outer peripheral surface of the honeycomb structure 1.

[0032] Although one electrode layer 11 may be provided on the entire outer peripheral surface of the honeycomb structure 1, in this embodiment, a pair of electrode layers 11 are provided that are spaced apart from each other in the circumferential direction of the honeycomb structure section 10 and extend in a strip-like shape in the extension direction of the cells 101a. In a cross section of the honeycomb structure section 10 perpendicular to the extension direction of the cells 101a, one of the pair of electrode layers 11 is disposed on the opposite side of the center of the honeycomb structure section 10 with respect to the other electrode layer 11 of the pair of electrode layers 11. In FIG. 1, only one of the pair of electrode layers 11 is shown. In a cross section perpendicular to the extension direction of the cells 101a, 0.5 times the central angle of each electrode layer 11 may be 15 to 89°. The central angle of the electrode layer 11 may be an angle formed by two line segments connecting both ends of the electrode layer 11 and the center of the honeycomb structure section 10 in a cross section of the honeycomb structure section 10 perpendicular to the extension direction of the cells 101a. When the honeycomb structure 10 is cylindrical, this angle may be the interior angle of a sector formed by two line segments and the electrode layer 11 .

[0033] The thickness of the electrode layer 11 is preferably 0.01 to 5 mm, and more preferably 0.01 to 3 mm. By setting the thickness in such a range, it is possible to generate heat uniformly. If the thickness of the electrode layer 11 is thinner than 0.01 mm, the electrical resistance may be high and heat may not be generated uniformly. If it is thicker than 5 mm, it may be damaged during canning. If the electrode layer 11 is too thin, the effect of adjusting the outer diameter when varying the outer diameter of the honeycomb structure 1 in the extension direction of the cells 101a due to the variation in the thickness of the electrode layer 11 as described later is weak, and if the electrode layer 11 is too thick, the holding force of the part without the electrode layer 11 does not work, and it is likely to fall off during a vibration test. If the electrode layer 11 is too thin, the resistance value of the electrode layer 11 is insufficient, and current easily flows through the base material (honeycomb structure part 10), which makes the heat generation distribution unstable, leading to a decrease in purification performance and damage to the base material. On the other hand, if the electrode layer 11 is too thick, a current will easily flow through the electrode layer 11 and the electrode layer 11 will easily generate heat, leading to unstable heat distribution, deterioration of the purification performance, and damage to the substrate.

[0034] The pair of electrode layers 11 in this embodiment each have a separator 110 and a first partial electrode layer 111 and a second partial electrode layer 112 separated by the separator 110. The separator 110 may be a slit provided between the first partial electrode layer 111 and the second partial electrode layer 112. The slit may be filled with a material having a higher volume resistivity than the first partial electrode layer 111 and the second partial electrode layer 112. The first partial electrode layer 111 and the second partial electrode layer 112 are strip-shaped having a predetermined width in the circumferential direction of the honeycomb structure section 10, and the separator 110 is linear and narrower than the first partial electrode layer 111 and the second partial electrode layer 112. However, the arrangement method of the separator 110 and the first partial electrode layer 111 and the second partial electrode layer 112 is not limited to this form as long as they can be connected to the metal electrode 20 described later.

[0035] As described below, a metal electrode 20 (see FIG. 2) is fixed on the electrode layer 11. The honeycomb structure 1 to which the metal electrode 20 is connected can be called an electrically heated carrier. Although not shown, an external power source such as a battery can be connected to the metal electrode 20 via a power cable. By applying a voltage to the honeycomb structure section 10 through the metal electrode 20 and the electrode layer 11, the honeycomb structure section 10 can generate heat.

[0036] From the viewpoint of making it easy for electricity to flow through the electrode layers 11, the volume resistivity of the electrode layers 11 is preferably 1 / 200 or more and 1 / 10 or less of the volume resistivity of the honeycomb structure section .

[0037] The material of the electrode layer 11 may be a conductive ceramic, a metal, or a composite material (cermet) of a metal and a conductive ceramic. Examples of the metal include a single metal such as Cr, Fe, Co, Ni, Si, or Ti, or an alloy containing at least one metal selected from the group consisting of these metals. Examples of the conductive ceramic include, but are not limited to, silicon carbide (SiC), and metal compounds such as metal silicides such as tantalum silicide (TaSi2) and chromium silicide (CrSi2).

[0038] In the manufacturing method of the honeycomb structure 1 having the electrode layer 11, first, an electrode layer forming raw material containing a ceramic raw material is applied to the side surface of the dried honeycomb body, and then dried to form a pair of unfired electrode layers extending in a band shape in the extension direction of the cells 101a on the outer surface of the outer peripheral wall 100, sandwiching the central axis of the dried honeycomb body, to produce a dried honeycomb body with unfired electrode layers. Next, the dried honeycomb body with the unfired electrode layers is fired to produce a fired honeycomb body having a pair of electrode layers 11. As a result, the honeycomb structure 1 having the electrode layers 11 is obtained.

[0039] By supporting a catalyst on the honeycomb structure 10, the electrically heated carrier can be used as a catalyst body. Examples of the catalyst include precious metal catalysts and other catalysts. Examples of the precious metal catalyst include three-way catalysts and oxidation catalysts in which precious metals such as platinum (Pt), palladium (Pd), and rhodium (Rh) are supported on the surface of alumina pores and contain co-catalysts such as ceria and zirconia, and NOx storage reduction catalysts (LNT catalysts) containing alkaline earth metals and platinum as nitrogen oxide (NOx) storage components. Examples of catalysts that do not use precious metals include NOx selective reduction catalysts (SCR catalysts) containing copper-substituted or iron-substituted zeolite. Two or more catalysts selected from these catalysts may be used. There is no particular restriction on the method of supporting the catalyst, and it can be performed in accordance with the conventional method of supporting the catalyst on the honeycomb structure 1.

[0040] 2 is a cross-sectional view of an exhaust gas purification device 2 including the honeycomb structure 1 of Fig. 1. The exhaust gas purification device 2 in the embodiment of the present invention includes the honeycomb structure 1, a metal electrode 20, a can body 21, and a buffer member 22.

[0041] The honeycomb structure 1 is as described above.

[0042] The metal electrode 20 is connected to the electrode layer 11 of the honeycomb structure 1. The honeycomb structure 1 to which the metal electrode 20 is connected can be called an electrically heated carrier. Although not limited thereto, the metal electrode 20 may have a connection portion 201 arranged on the electrode layer 11 and an extraction portion 202 extracted from the connection portion 201. Although not shown in detail, the connection portion 201 may be configured in a comb shape having a plurality of teeth, and some of the teeth may be connected to the first partial electrode layer 111 (see FIG. 1), and the other teeth may be connected to the second partial electrode layer 112 (see FIG. 1). The connection portion 201 may be formed in an arc shape along the outer peripheral surface of the honeycomb structure 1. The extraction portion 202 may be erected from one end of the connection portion 201 and extracted to the outside of the can body 21, and a power cable may be connected to the extraction portion 202.

[0043] The can body 21 is a metal member that holds the honeycomb structure 1. The can body 21 surrounds the honeycomb structure 1 in the circumferential direction of the honeycomb structure 1. The inner diameter of the can body 21 at the outer periphery of the honeycomb structure 1 may be constant in the extension direction of the cells 101a. The outer periphery of the honeycomb structure 1 may be understood as a position outside the honeycomb structure 1 in the radial direction of the honeycomb structure 1 and between the end faces of the honeycomb structure 1 in the extension direction of the cells 101a.

[0044] An outlet opening 210 corresponding to the outlet portion 202 is provided on the outer peripheral surface of the can body 21 , and a power cable can be connected to the outlet portion 202 from outside the can body 21 through the outlet opening 210 .

[0045] The can body 21 is provided with a first end opening 211 and a second end opening 212 spaced apart in the extending direction of the cells 101a. Exhaust gas is introduced into the can body 21 from one of the first end opening 211 and the second end opening 212, and the exhaust gas that has passed through the cells 101a of the honeycomb structure 1 inside the can body 21 can be discharged to the outside of the can body 21 from the other of the first end opening 211 and the second end opening 212. One of the first end opening 211 and the second end opening 212 into which the exhaust gas is introduced can be called an inlet opening, and the other of the first end opening 211 and the second end opening 212 from which the exhaust gas is discharged can be called an outlet opening. In addition, one end face of the honeycomb structure 1 into which the exhaust gas is introduced can be called an inlet end face, and the other end face of the honeycomb structure 1 from which the exhaust gas exits can be called an outlet end face.

[0046] The buffer member 22 is disposed between the honeycomb structure 1 and the can body 21. The buffer member 22 may be wrapped around the outer periphery of the honeycomb structure 1. The buffer member 22 is provided with a through hole 220 corresponding to the drawn-out portion 202, and a power cable can be connected to the drawn-out portion 202 from outside the can body 21 through the through hole 220. The buffer member 22 may be made of a material that is compressible in the radial direction of the honeycomb structure 1. There is no particular limitation on the material of the buffer member 22, but a non-expanding ceramic fiber mat, a thermally expandable mineral material mat, or the like can be used.

[0047] Next, the honeycomb structure 1 according to the embodiment of the present invention will be described in more detail with reference to Fig. 3 to Fig. 5. Fig. 3 is an explanatory view showing a first embodiment of the honeycomb structure 1 in Fig. 1, Fig. 4 is an explanatory view showing a second embodiment of the honeycomb structure 1 in Fig. 1, and Fig. 5 is an explanatory view showing a third embodiment of the honeycomb structure 1 in Fig. 1.

[0048] As shown in Figures 3 to 5, in the honeycomb structure 1 according to the embodiment of the present invention, the electrode layers 11 are formed so that their thickness varies in the extension direction of the cells 101a (the vertical direction in Figures 3 to 5), and the honeycomb structure 1 is formed so that its outer diameter varies in the extension direction of the cells 101a due to the variation in thickness of the electrode layers 11. In Figures 3 to 5, the variation in thickness of the electrode layers 11 is shown exaggerated for ease of understanding.

[0049] When exhaust gas is passed through the cells 101a of the honeycomb structure 1, specific locations of the honeycomb structure 1 repeatedly undergo thermal expansion, and loads are concentrated on corresponding locations of the buffer members 22, which may cause shear displacement in the buffer members 22. When shear displacement occurs in the buffer members 22, the gripping force of the buffer members 22 on the honeycomb structure 1 decreases, and the honeycomb structure 1 becomes more likely to slip from the can body 21.

[0050] The location where the load of the buffer member 22 is concentrated may vary depending on the exhaust gas introduction mode (exhaust gas temperature and / or the duration of exhaust gas introduction, etc.). For example, as will be described later with reference to Figs. 6 and 7, in a mode in which high-temperature exhaust gas for a short period of time and low-temperature gas for a short period of time are repeatedly introduced into the honeycomb structure 1, the load tends to be concentrated on the buffer member 22 at the inlet and outlet locations of the honeycomb structure 1. By making the outer diameter of the honeycomb structure 1 smaller at the location where the load of the buffer member 22 is concentrated than other portions, the load of the buffer member 22 can be reduced, and the displacement of the honeycomb structure 1 from the can body 21 due to shear displacement of the buffer member 22 can be suppressed. The location of the honeycomb structure 1 where the outer diameter is made smaller than other portions can be arbitrarily changed depending on the usage mode of the honeycomb structure 1.

[0051] Furthermore, when the thickness of the peripheral wall 100 is partially changed, the cells 101a may be deformed during the manufacture of the honeycomb structure 1, which may reduce the strength of the honeycomb structure 1. As in the honeycomb structure 1 according to the embodiment of the present invention, the thickness of the peripheral wall 100 can be made constant by adjusting the outer diameter of the honeycomb structure 1 by varying the thickness of the electrode layer 11, thereby making it possible to avoid a reduction in the strength of the honeycomb structure 1. In other words, it is preferable that the thickness of the peripheral wall 100 is constant in the extension direction of the cells 101a.

[0052] As shown in Figs. 3 to 5, the honeycomb structure 1 may include a first region A, a second region B, and a third region C aligned in the extending direction of the cells 101a. The first region A may be disposed on one end face side of the honeycomb structure 1, the third region C may be disposed on the other end face side of the honeycomb structure 1, and the second region B may be disposed between the first region A and the third region C. In the honeycomb structure 1 according to the embodiment of the present invention, the outer diameter R of the first region A may vary due to the variation in thickness of the electrode layer 11. A , outer diameter R of second region B B and the outer diameter R of the third region C C One of them may be different from the other one or two.

[0053] The first region A may be a region that is 1 / 3 of the total length of the honeycomb structure 1 in the extension direction of the cells 101a from one end face of the honeycomb structure 1, and the third region C may be a region that is 1 / 3 of the total length of the honeycomb structure 1 in the extension direction of the cells 101a from the other end face of the honeycomb structure 1. The one end face on which the first region A is provided may be an inlet end face in the flow direction of the exhaust gas, and the other end face on which the third region C is provided may be an outlet end face in the flow direction of the exhaust gas.

[0054] Outer diameter R of first area A A , outer diameter R of second region B B and the outer diameter R of the third region C C The outer diameter R of the regions A to C can be measured by the same method. A ~R Cmay be the outer diameter of the honeycomb structure 1 measured at a plurality of positions separated from each other in the extending direction of the cells 101a in the regions A to C. In addition, the outer diameter R A ~R C Each of the outer diameters R of the honeycomb structure 1 may be measured at a plurality of positions spaced apart from each other in the circumferential direction of the honeycomb structure 1 within the region where the electrode layer 11 is provided. A ~R C Each of these may be the maximum value of the outer diameter of the honeycomb structure 1 measured in each of the regions A to C.

[0055] More specifically, in the extension direction of the cells 101a, a plurality of measurement points were set on the outer peripheral surface of the honeycomb structure 1 at equal intervals in the circumferential direction of the honeycomb structure 1 within the region where the electrode layer 11 is provided at three positions in total, namely, the central position of each of the regions A to C and two positions at a distance of 5% of the total length of each of the regions A to C from both ends of each of the regions A to C, and the coordinates of each measurement point were calculated by a laser displacement meter, and the outer diameter R of each of the regions A to C was calculated from the coordinates of a pair of measurement points located on either side of the central axis of the honeycomb structure 1. A ~R C can be calculated.

[0056] Ten pairs of measurement points may be set at equal intervals in the circumferential direction of the honeycomb structure 1. When a pair of electrode layers 11 is provided on the honeycomb structure 1 as in the present embodiment, ten measurement points may be set on each electrode layer 11.

[0057] The outer diameter of the honeycomb structure 1 can be measured in the same manner even in the region where the electrode layer 11 is not provided. That is, a plurality of measurement points are set on the outer peripheral surface of the honeycomb structure 1 at equal intervals in the circumferential direction of the honeycomb structure 1 in the region where the electrode layer 11 is not provided at three positions in total, namely, the central position of each of the regions A to C and two positions at a distance of 5% of the total length of each of the regions A to C from both ends of each of the regions A to C, and the coordinates of each measurement point are calculated by a laser displacement meter, and the outer diameter of the honeycomb structure 1 can be calculated from the coordinates of a pair of measurement points located on either side of the central axis of the honeycomb structure 1. Even in the region where the electrode layer 11 is not provided, ten pairs of measurement points may be set at equal intervals in the circumferential direction of the honeycomb structure 1. When a pair of electrode layers 11 is provided on the honeycomb structure 1 as in the present embodiment, ten measurement points may be set in each of the two regions between the electrode layers 11. The maximum value of the measured outer diameter is taken as the outer diameter of the honeycomb structure 1. The outer diameter of the honeycomb structure 1 measured in this manner corresponds to the outer diameter of the honeycomb structure portion 10 or the outer peripheral wall 100. A ~R C By subtracting the outer diameter of the honeycomb structure section 10 from the thickness, the thickness of the electrode layer 11 in each of the regions A to C can be calculated.

[0058] Even when the electrode layer 11 is provided over the entire periphery of the honeycomb structure 1, the outer diameter R of each of the regions A to C can be determined by the above method. A ~R C On the other hand, the outer diameter of the honeycomb structure part 10 may be obtained by setting a plurality of equally spaced points in the circumferential direction on the outer peripheral surface of the honeycomb structure part 10 at the end face or cross section of the honeycomb structure 1, and calculating the coordinates of each measurement point using a microscope or the like.

[0059] When a pair of electrode layers 11 is provided on the honeycomb structure 1, the outer diameter R of the regions A to C from the outer surface A ~R C In the manufacturing process of the honeycomb structure 1, the outer diameter R A ~R CThe outer diameters R of the honeycomb structure portion 10 and the outer diameter R of the honeycomb structure portion 10 may be measured together in one step. Also, these measurements may be performed for all the honeycomb structures 1. On the other hand, when the electrode layer 11 is provided over the entire circumference of the honeycomb structure 1, the outer diameter R of the regions A to C from the outer surface A ~R C and the outer diameter of the honeycomb structure part 10, but the outer diameter of the honeycomb structure part 10 in the region B located in the center is determined from a sample divided (sliced ​​into rings) from the honeycomb structure 1. For the outer diameter of the honeycomb structure part 10 in the region B, a value measured from a sample randomly extracted from a plurality of honeycomb structures 1 may be used as a representative value for the whole.

[0060] Outer diameter R A From outer diameter R B and outer diameter R B From outer diameter R C The change in the outer diameter to may be stepwise or continuous, and when the change in the outer diameter is continuous, the change may be linear or nonlinear.

[0061] As shown in FIG. 3, the outer diameter R B The outer diameter R of the first area A A and the outer diameter R of the third region C C In this case, the relationship between the outer diameters is R A ≦R C <R B or R C ≦R A <R B The outer shape of such a honeycomb structure 1 can be called a drum shape or a barrel shape (hereinafter, collectively referred to as a "drum shape, etc."). The honeycomb structure 1 having a drum shape, etc. is useful in an embodiment in which there is a concern about shear displacement of the buffer member 22 in the first region A and the third region C located on the inlet side and the outlet side, as compared with the second region B located in the center.

[0062] As shown in FIG. 4, the outer diameter R B The outer diameter R of the first area A A and the outer diameter R of the third region C CIn this case, the relationship between the outer diameters is R B <R A ≦R C or R B <R C ≦R A Such an external shape of the honeycomb structure 1 can be called a drum-shaped shape. The drum-shaped honeycomb structure 1 is useful in an embodiment in which there is a concern about shear displacement of the buffer member 22 in the second region B located at the center, compared with the first region A and the third region C located at the inlet and outlet sides. For example, when the honeycomb structure 1 is electrically heated before the exhaust gas is introduced, the temperatures of the inlet and outlet sides drop due to heat dissipation through contact with air, and the temperature of the central portion may become relatively high. When exhaust gas is introduced in this state, shear displacement of the buffer member 22 in the second region B located at the center may occur.

[0063] As shown in FIG. 5, the outer diameter R A The outer diameter R of the second region B B and the outer diameter R of the third region C C Conversely, the outer diameter R C The outer diameter R of the first area A A and the outer diameter R of the second region B B In this case, the relationship between the outer diameters is R A ≦R B <R C It is said that R C ≦R B <R A It is said that R A <R B ≦R C or R C <R B ≦R A The outer shape of such a honeycomb structure 1 can be called a stepped shape, a tapered shape, or a wedge shape (hereinafter collectively referred to as a "step shape, etc."). Compared to other types, the stepped honeycomb structure 1 is useful in an embodiment in which shear displacement of the buffer member 22 in the first region A located on the inlet side or the third region C located on the outlet side is a concern.

[0064] Outer diameter R of first area A A , outer diameter R of second region B B and the outer diameter R of the third region C C The minimum outer diameter R min Maximum outer diameter R max Ratio R max / R min For example, in the honeycomb structure 1 having a drum shape or the like shown in FIG. A and / or the outer diameter R of the third region C C is the minimum outer diameter R min and the outer diameter R of the second region B B is the maximum outer diameter R max As will be shown later as an example, the ratio R max / R min When the ratio R is within this range, it is possible to more reliably suppress the displacement of the honeycomb structure 1 from the can body 21 due to the shear displacement of the buffer member 22. max / R min However, it is more preferable that the ratio is 1.001 or more and 1.052 or less, even more preferable that the ratio is 1.010 or more and 1.048 or less, and even more preferable that the ratio is 1.014 or more and 1.042 or less. The displacement of the honeycomb structure 1 can be suppressed more reliably.

[0065] Next, Figure 6 is an explanatory diagram showing the thermal expansion of a honeycomb structure 1 having a constant outer diameter for comparison when it is mounted on a hybrid vehicle or a plug-in hybrid vehicle, and Figure 7 is an explanatory diagram showing the thermal expansion of a honeycomb structure 1 having a drum shape such as that of Figure 3 when it is mounted on a hybrid vehicle or a plug-in hybrid vehicle.

[0066] A hybrid vehicle or a plug-in hybrid vehicle (hereinafter simply referred to as a "hybrid vehicle") alternates between running on an engine and running on a motor, and high-temperature exhaust gas for a short period of time and low-temperature gas for a short period of time may be repeatedly introduced into the honeycomb structure 1. For example, immediately after the engine is started, exhaust gas concentrates on the inlet side of the honeycomb structure 1, causing the inlet side to warm up and expand. Thereafter, when the vehicle is stopped at a traffic light or the like, low-temperature gas is introduced into the honeycomb structure 1, causing the inlet side of the honeycomb structure 1 to cool rapidly, while the heat accumulated up until that point causes the outlet side of the honeycomb structure 1 to relatively expand.

[0067] Figures 6 and 7(a) show the state before exhaust gas is introduced into the honeycomb structure 1, Figures 6 and 7(b) show the state after exhaust gas is introduced into the honeycomb structure 1 and the inlet side of the honeycomb structure 1 expands, Figures 6 and 7(c) show the state after the entire honeycomb structure 1 expands due to the heat of the exhaust gas, and Figures 6 and 7(d) show the state after low-temperature gas is introduced into the honeycomb structure 1 and the inlet side of the honeycomb structure 1 is cooled and the outlet side expands relatively. The shaded parts of the honeycomb structure 1 indicate the expansion, and the dashed circle indicates the point where the load is concentrated on the buffer member 22.

[0068] In the case of a honeycomb structure 1 having a constant outer diameter as shown in FIG. 6, the load tends to be concentrated on the buffer member 22 at the inlet and outlet sides of the honeycomb structure 1 as indicated by the dashed circles in (b) and (d) of FIG.

[0069] In contrast, in a honeycomb structure 1 having a drum shape or the like as shown in Figure 7, although a load is applied to the buffer member 22 at the inlet and outlet points of the honeycomb structure 1 as shown by the dashed circles in (b) and (d) of Figure 7, the outer diameters of the inlet and outlet sides are smaller than the outer diameter at the center, so that the load can be reduced.

[0070] In addition, in the honeycomb structure 1 having a drum shape or the like, when the entire honeycomb structure 1 is thermally expanded as shown in Fig. 7(c), it seems that the load is concentrated on the buffer member 22 at the center of the honeycomb structure 1. However, when a hybrid vehicle runs in an urban area, exhaust gas and low-temperature gas are sequentially introduced into the honeycomb structure 1, so that the period during which the entire honeycomb structure 1 is thermally expanded uniformly is short, and it is considered that the effect of the load of the buffer member 22 at the center of the honeycomb structure 1 is smaller than the effect of the load of the buffer member 22 at the inlet and outlet sides. In addition, as shown in Fig. 2, the honeycomb structure 1 is often provided at its center with a metal electrode 20 and an extraction opening 210 and a through hole 220 for extracting the metal electrode 20 to the outside, and it is also considered that the effect of the load of the buffer member 22 at the center of the honeycomb structure 1 is smaller than the effect of the load of the buffer member 22 at the inlet and outlet sides due to heat radiation from them.

[0071] Furthermore, in a honeycomb structure 1 having a drum shape or the like, even when the honeycomb structure 1 is not thermally expanded as shown in Fig. 7(a), it appears that the load is concentrated on the buffer member 22 at the center of the honeycomb structure 1. However, when not thermally expanded, the external shape of the honeycomb structure 1 is relatively small compared to when it is thermally expanded, and the load at this time is smaller than the load during thermal expansion, so it is considered that the effect of the load when not thermally expanded on the shear displacement of the buffer member 22 is relatively small.

[0072] When the honeycomb structure 1 is not thermally expanded as shown in (a) of Figure 7, the pressure compressing the buffer member 22 between the can body 21 and the honeycomb structure 1 may be smaller at the inlet and outlet sides of the honeycomb structure 1 compared to the center of the honeycomb structure 1.

[0073] Although the preferred embodiment of the present invention has been described in detail above with reference to the accompanying drawings, the present invention is not limited to such an example. It is clear that a person having ordinary knowledge in the technical field to which the present invention pertains can conceive of various modified or altered examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally belong to the technical scope of the present invention. EXAMPLES

[0074] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0075] The present inventors prepared test specimens of honeycomb structure 1 having a drum shape as shown in FIG. 3, and placed these test specimens together with cushioning member 22 inside a can body 21 to carry out a displacement test of honeycomb structure 1.

[0076] Each of the test specimens (embodiments) had an outer diameter R of the first region A as shown in Table 1 below. A , outer diameter R of second region B B and the outer diameter R of the third region C C The combination of the first region A and the third region C is changed. The second region B is sometimes called the center. In the examples 1 to 8, the outer diameter R A is the outer diameter R of the output side C The same example is used, and Examples 9 to 14 are the inlet outer diameter R A is the outer diameter R of the output side CThis is a different example from the above. The outer diameter of the honeycomb structure 1 excluding the electrode layer 11 (i.e., the outer diameter of the honeycomb structure portion 10) is constant in the extending direction of the cells 101a, and the outer diameter of the honeycomb structure 1 is varied by varying the thickness of the electrode layer 11. In Table 1, the description below each outer diameter indicates the outer diameter of the honeycomb structure portion 10 and the thickness of the electrode layer 11. For example, the notation "base material diameter 80" means that the outer diameter of the honeycomb structure portion 10 is 80 mm. Also, for example, the notation "electrode layer 0.25×2" means that there are two electrode layers 11 with a thickness of 0.25 mm in the cross section of the honeycomb structure portion 10 perpendicular to the extending direction of the cells 101a. Each specimen is provided with a pair of electrode layers 11 that are spaced from each other in the circumferential direction of the honeycomb structure portion 10 and extend in a strip shape in the extending direction of the cells 101a. In a cross section of the honeycomb structure section 10 perpendicular to the extending direction of the cells 101a, one of a pair of electrode layers 11 is disposed on the opposite side of the center of the honeycomb structure section 10 with respect to the other of the pair of electrode layers 11. The inner diameter of the can body 21 at the outer periphery of the honeycomb structure 1 is constant at 88 mm, and a non-thermally expandable ceramic mat (product name: MAFTEC) manufactured by Mitsubishi Plastics, Inc. having a thickness of 6.2 mm is used as the buffer member 22.

[0077] The honeycomb structure 1 was subjected to a displacement test as follows. That is, a test specimen was placed inside the can body 21 together with the buffer member 22, and the specimen was placed in a vibration tester, and a vibration test was performed on the honeycomb structure 1. The vibration conditions in the vibration test were acceleration: 30G, and frequency: 100Hz. Gas discharged from a gas burner was passed through the can body 21. In the vibration test, the temperature at the center 10 mm upstream from the inlet end face of the honeycomb structure 1 was 700°C during heating and 150°C during cooling, and heating and cooling were repeated in a 3-minute cycle, and the honeycomb structure 1 was vibrated in the gas flow direction under the above vibration conditions for 30 hours. After this vibration test, the state of the honeycomb structure 1 placed inside the can body 21 was confirmed. The distance that the honeycomb structure 1 moved in the gas flow direction inside the can body 21 was measured with a scale. In addition, as a comparative example, as shown in Table 1 below, the outer diameter R A , outer diameter R of second region B (center) Band the outer diameter R of the third area C (exit side) C A honeycomb structure 1 having a constant thickness was also prepared and tested in the same manner. The test results of the examples and comparative examples are shown in Table 1 below.

[0078] [Table 1]

[0079] FIG. 8 shows the minimum outer diameter R of the honeycomb structure 1 in a slippage test. min Maximum outer diameter R max Ratio R max / R min 8 is a graph showing the relationship between the ratio (R max / R min When the ratio (R max / R min ) increases, the deviation decreases and then increases again.

[0080] From the trend of the deviation, the ratio (R max / R min It can be seen that when the ratio (R ) is greater than 1.000 and less than 1.061, the displacement of the honeycomb structure 1 can be suppressed as compared to the comparative example. max / R min It can be seen that when the ratio (R max / R min If the ratio (R max / R min ) is 1.014 or more and 1.042 or less, the amount of deviation of the honeycomb structure 1 can be made 1 mm or less, and it can be seen that the deviation of the honeycomb structure 1 can be suppressed more reliably. [Explanation of symbols]

[0081] 1: Honeycomb structure 10: Honeycomb structure 100: Outer wall 101: Bulkhead 101a: Cell 11: Electrode layer 2: Exhaust gas purification device 20: Metal electrode 21:Can body 22: Cushioning material

Claims

1. a honeycomb structure having an outer peripheral wall and partition walls disposed inside the outer peripheral wall and defining a plurality of cells that form flow paths extending from one end face to the other end face; At least one electrode layer provided on an outer surface of the outer circumferential wall; A honeycomb structure comprising: The electrode layer is formed so as to vary in thickness in an extension direction of the cell, The honeycomb structure is formed such that an outer diameter varies in an extending direction of the cells due to a variation in thickness of the electrode layer. Honeycomb structure.

2. the honeycomb structure includes a first region, a second region, and a third region aligned in an extension direction of the cells, the first region being disposed on the one end face side, the third region being disposed on the other end face side, and the second region being disposed between the first region and the third region, Due to a variation in thickness of the electrode layer, one of the outer diameter of the first region, the outer diameter of the second region, and the outer diameter of the third region is different from the other one or two. The honeycomb structure according to claim 1 .

3. The minimum outer diameter (R min ) to the maximum outer diameter (R max ) ratio (R max / R min ) is greater than 1.000 and less than 1.061; The honeycomb structure according to claim 2 .

4. The ratio (R max / R min ) is 1.001 or more and 1.052 or less; The honeycomb structure according to claim 3 .

5. The ratio (R max / R min ) is 1.010 or more and 1.048 or less; The honeycomb structure according to claim 4.

6. The ratio (R max / R min ) is 1.014 or more and 1.042 or less; The honeycomb structure according to claim 5 .

7. The outer diameter of the first region is R A and the outer diameter of the second region is R B and the outer diameter of the third region is R C When R A ≦R C <R B or R C ≦R A <R B It is said that, The honeycomb structure according to any one of claims 2 to 6.

8. A honeycomb structure according to any one of claims 1 to 6, a metal electrode connected to the electrode layer of the honeycomb structure; a metal case body for holding the honeycomb structure; a buffer member disposed between the honeycomb structure and the can body; Equipped with The inner diameter of the can body at the outer periphery of the honeycomb structure is constant in the extension direction of the cells. Exhaust gas purification device.

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