阅读说明：本技术 电加热式载体及废气净化装置 (Electric heating type carrier and exhaust gas purification device ) 是由 高濑尚哉 吉田信也 金子公久 于 2020-02-25 设计创作，主要内容包括：本发明提供能够良好地抑制因通电加热时的电极层破损及电极层劣化所导致的电阻增大的电加热式载体及废气净化装置。电加热式载体具备蜂窝结构体和一对金属端子,蜂窝结构体具备：柱状蜂窝结构部,该柱状蜂窝结构部具有外周壁和多孔质的隔壁,该多孔质的隔壁配设于外周壁的内侧,并区划形成从一个端面贯通至另一个端面而形成流路的多个隔室；一对电极层,该一对电极层按隔着柱状蜂窝结构部的中心轴而对置的方式配设于柱状蜂窝结构部的外周壁的表面；及保护层,该保护层按将电极层的至少一部分暴露出来的方式对电极层进行覆盖,一对金属端子设置于一对电极层上,电极层由金属－陶瓷混合材料构成,电极层中的自保护层暴露出来的部分与金属端子电连接。(The invention provides an electrically heated carrier and an exhaust gas purifying apparatus, which can well inhibit resistance increase caused by electrode layer damage and electrode layer deterioration during electric heating. The electrically heated carrier includes a honeycomb structure and a pair of metal terminals, and the honeycomb structure includes: a columnar honeycomb structure portion having an outer peripheral wall and porous partition walls which are arranged inside the outer peripheral wall and partition a plurality of cells which form flow paths by penetrating from one end face to the other end face; a pair of electrode layers disposed on the surface of the outer peripheral wall of the columnar honeycomb structure portion so as to face each other with the central axis of the columnar honeycomb structure portion interposed therebetween; and a protective layer covering the electrode layer in such a manner that at least a part of the electrode layer is exposed, the pair of metal terminals being provided on the pair of electrode layers, the electrode layer being made of a metal-ceramic mixture, the exposed part of the electrode layer from the protective layer being electrically connected to the metal terminals.)

1. An electrically heated carrier characterized in that,

the disclosed device is provided with: a honeycomb structural body and a pair of metal terminals,

the honeycomb structure is provided with:

a columnar honeycomb structure portion having an outer peripheral wall and porous partition walls which are arranged inside the outer peripheral wall and partition a plurality of cells which form flow paths by penetrating from one end face to the other end face;

a pair of electrode layers disposed on a surface of an outer peripheral wall of the columnar honeycomb structure portion so as to face each other with a central axis of the columnar honeycomb structure portion interposed therebetween; and,

A protective layer covering the electrode layer so as to expose at least a part of the electrode layer,

the pair of metal terminals are disposed on the pair of electrode layers,

the electrode layer is made of a metal-ceramic hybrid material,

the portion of the electrode layer exposed from the protective layer is electrically connected to the metal terminal.

2. The electrically heated carrier according to claim 1,

the electrode layer is made of a metal-ceramic mixed material in which the metal content is 30-75 vol%.

3. The electrically heated carrier according to claim 1 or 2,

the maximum thickness of the protective layer is 1.5 times or more the average thickness of the electrode layer.

4. An electrically heated carrier as claimed in any one of claims 1 to 3,

the electrode layer is composed of a support portion on the surface side of the outer peripheral wall of the columnar honeycomb structural portion and a protruding portion rising from the support portion,

and the protective layer is provided in such a manner as to expose at least a part of the surface of the protruding portion.

5. The electrically heated carrier according to claim 4,

the support portion is formed of a plurality of linear portions extending radially along the surface of the outer peripheral wall of the columnar honeycomb structural portion with a point directly below the protruding portion as a center.

6. The electrically heated carrier according to claim 5,

the support portion further includes at least one branch portion branched from the plurality of linear portions extending radially.

7. The electrically heated carrier as claimed in any one of claims 1 to 6,

the pair of electrode layers are each configured to be divided into a plurality of regions.

8. An electrically heated carrier as claimed in any one of claims 1 to 7,

the portion of the electrode layer exposed from the protective layer is a portion joined to the metal terminal.

9. An exhaust gas purification apparatus, comprising:

the electrically heated carrier as claimed in any one of claims 1 to 8, and

a tank for holding the electrically heated carrier.

10. An electrically heated carrier characterized in that,

a honeycomb structure is provided with a honeycomb structure,

the honeycomb structure is provided with:

a columnar honeycomb structure portion having an outer peripheral wall and porous partition walls which are arranged inside the outer peripheral wall and partition a plurality of cells which form flow paths by penetrating from one end face to the other end face;

a pair of electrode layers disposed on a surface of an outer peripheral wall of the columnar honeycomb structure portion so as to face each other with a central axis of the columnar honeycomb structure portion interposed therebetween; and,

A protective layer covering the electrode layer so as to expose at least a part of the electrode layer,

the electrode layer is made of a metal-ceramic hybrid material,

the electrode layer has a portion exposed from the protective layer for electrical connection with a metal terminal.

Technical Field

The present invention relates to an electrically heated carrier and an exhaust gas purification apparatus. In particular, the present invention relates to an electrically heated carrier and an exhaust gas purifying apparatus capable of satisfactorily suppressing an increase in resistance due to electrode layer breakage and electrode layer deterioration at the time of energization heating.

Background

Conventionally, the exhaust gas is used for HC, CO and NO contained in exhaust gas discharged from an engine of an automobile or the like_xThe catalyst is supported on a columnar honeycomb structure having a plurality of partition walls that partition a plurality of cells that form flow paths extending from one bottom surface to another bottom surface. In this way, when the exhaust gas is treated with the catalyst supported on the honeycomb structure, the catalyst needs to be heated to its activation temperature, but the catalyst does not reach the activation temperature at the time of engine start, and therefore, there is a problem that the exhaust gas cannot be sufficiently purified. In particular, since the travel using only the motor is included in the travel of the plug-in hybrid vehicle (PHEV) or the Hybrid Vehicle (HV), the engine start frequency is low, the catalyst temperature at the time of engine start is low, and the exhaust gas purification performance immediately after the engine start is likely to deteriorate.

In order to solve this problem, an Electrically Heated Catalyst (EHC) has been proposed in which a pair of terminals are connected to a columnar honeycomb structure made of a conductive ceramic, and the honeycomb structure itself generates heat by energization, thereby raising the temperature of the catalyst to an activation temperature before the engine is started. For the EHC, it is desirable to reduce the temperature unevenness in the honeycomb structure to be uniform in temperature distribution in order to sufficiently obtain the catalytic effect.

In order to connect terminals of the honeycomb structure and generate heat in the honeycomb structure by energization, a surface electrode needs to be provided on the outer periphery of the honeycomb structure. However, if the current is repeatedly applied, the surface electrode may be damaged by thermal stress.

In order to solve the above problem, patent document 1 discloses a configuration in which a ceramic surface electrode (electrode layer) is provided on an outer peripheral surface of a carrier of an EHC, and a metal extension member is embedded in the surface electrode. Further, it is described that: according to this configuration, even if the surface electrode is damaged, the entire carrier can be electrically heated by the embedded metal spreading member.

Disclosure of Invention

However, the inventors of the present invention have conducted studies and found that, in the structure disclosed in patent document 1, a metal extension member embedded in a ceramic surface electrode is easily oxidized, and if the surface electrode is not dense, oxidation may occur and the function may be lost due to an increase in resistance or the like. In addition, it was found that: since the metal has a high thermal expansion coefficient, if a metal extension member is embedded in the ceramic surface electrode, the surface electrode may be damaged when thermally expanded by energization heating.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an electrically heated carrier and an exhaust gas purifying apparatus capable of satisfactorily suppressing an increase in resistance due to electrode layer breakage and electrode layer deterioration at the time of energization heating.

The present inventors have made extensive studies and as a result, have found that the above problems can be solved by employing a structure in which an electrode layer is made of a metal-ceramic mixture and the electrode layer is covered with a protective layer so that at least a part of the electrode layer is exposed. Namely, the present invention is determined as follows.

(1) An electrically heated carrier characterized in that,

the disclosed device is provided with: a honeycomb structural body and a pair of metal terminals,

the honeycomb structure is provided with:

a columnar honeycomb structure portion having an outer peripheral wall and porous partition walls which are arranged inside the outer peripheral wall and partition a plurality of cells which form flow paths by penetrating from one end face to the other end face;

a pair of electrode layers disposed on a surface of an outer peripheral wall of the columnar honeycomb structure portion so as to face each other with a central axis of the columnar honeycomb structure portion interposed therebetween; and a protective layer covering the electrode layer so as to expose at least a part of the electrode layer,

the pair of metal terminals are disposed on the pair of electrode layers,

the electrode layer is made of a metal-ceramic hybrid material,

the portion of the electrode layer exposed from the protective layer is electrically connected to the metal terminal.

(2) An exhaust gas purification apparatus, comprising:

(1) the electrically heated carrier, and

a tank for holding the electrically heated carrier.

(3) An electrically heated carrier characterized in that,

a honeycomb structure is provided with a honeycomb structure,

the honeycomb structure is provided with:

a columnar honeycomb structure portion having an outer peripheral wall and porous partition walls which are arranged inside the outer peripheral wall and partition a plurality of cells which form flow paths by penetrating from one end face to the other end face;

a pair of electrode layers disposed on a surface of an outer peripheral wall of the columnar honeycomb structure portion so as to face each other with a central axis of the columnar honeycomb structure portion interposed therebetween; and,

A protective layer covering the electrode layer so as to expose at least a part of the electrode layer,

the electrode layer is made of a metal-ceramic hybrid material,

the electrode layer has a portion exposed from the protective layer for electrical connection with a metal terminal.

Effects of the invention

According to the present invention, it is possible to provide an electrically heated carrier and an exhaust gas purifying apparatus that can favorably suppress an increase in resistance due to electrode layer breakage and electrode layer deterioration during electrical heating.

Drawings

Fig. 1 is a schematic cross-sectional view of an electrically heated carrier in embodiment 1 of the present invention, the cross-sectional view being perpendicular to the direction in which compartments extend.

Fig. 2 is a schematic external view of the honeycomb structure according to embodiment 1 of the present invention or the electrically heated support according to embodiment 2 of the present invention.

Fig. 3 is a schematic cross-sectional view of the columnar honeycomb structure portion, the electrode layer, and the protective layer in embodiment 1 of the present invention, the cross-sectional view being perpendicular to the cell extension direction.

Fig. 4 is a schematic plan view of an electrode layer having a plurality of linear portions extending radially from the center in embodiment 1 of the present invention.

Fig. 5 is a schematic plan view of the electrode layer having the structure shown in fig. 4 provided in a plurality of regions on the columnar honeycomb structure portion.

Description of the symbols

10 … honeycomb structure, 11 … columnar honeycomb structure part, 12 … peripheral wall, 13 … partition wall, 14a, 14b … electrode layer, 15 … cell, 17a, 17b … protection layer, 18 … exposed part, 20, 30 … electric heating carrier, 21a, 21b … metal terminal, 22 … support part, 23 … protruding part, 24 … straight part and 29 … straight part.

Detailed Description

Next, specific embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments, and it should be understood that: modifications, improvements and the like can be appropriately designed based on the general knowledge of those skilled in the art without departing from the scope of the present invention.

< embodiment 1 >

(1. electric heating type carrier)

Fig. 1 is a schematic cross-sectional view of an electrically heated support 20 in embodiment 1 of the present invention, the cross-sectional view being perpendicular to the direction in which the compartments extend. The electrically heated carrier 20 includes: a honeycomb structure 10, and a pair of metal terminals 21a, 21 b.

(1-1. Honeycomb Structure)

Fig. 2 is a schematic external view of the honeycomb structure 10 according to embodiment 1 of the present invention. The honeycomb structure 10 includes a columnar honeycomb structure portion 11, and the columnar honeycomb structure portion 11 has an outer peripheral wall 12 and porous partition walls 13, and the porous partition walls 13 are arranged inside the outer peripheral wall 12 and partition a plurality of cells 15 that form flow paths penetrating from one end face to the other end face.

The outer shape of the columnar honeycomb structural portion 11 is not particularly limited, and may be, for example, a columnar shape (columnar shape) having a circular bottom surface, a columnar shape having an elliptical bottom surface, a columnar shape having a polygonal bottom surface (quadrangular, pentagonal, hexagonal, heptagonal, octagonal, or the like), or the like. In addition, the size of the columnar honeycomb structural portion 11 is preferably 2000 to 20000mm in area of the bottom surface for the reason of improving heat resistance (suppressing generation of cracks in the circumferential direction of the outer circumferential wall)²More preferably 5000 to 15000mm²。

The columnar honeycomb structure portion 11 is made of ceramic having electrical conductivity. The honeycomb structure 10 may be heated by joule heat when energized, and the specific resistance of the ceramic is not particularly limited, but is preferably 1 to 200 Ω cm, and more preferably 10 to 100 Ω cm. In the present invention, the resistivity of the columnar honeycomb structural portion 11 is a value measured at 400 ℃ by a four-terminal method.

The ceramics constituting the columnar honeycomb structural portion 11 are not limited, and examples thereof include: oxide-based ceramics such as alumina, mullite, zirconia, and cordierite; non-oxide ceramics such as silicon carbide, silicon nitride, and aluminum nitride. In addition, a silicon carbide-metal silicon composite material, a silicon carbide/graphite composite material, or the like may also be used. Among these, from the viewpoint of achieving both heat resistance and electrical conductivity, the material of the columnar honeycomb structural portion 11 is preferably a silicon-silicon carbide composite material or a ceramic containing silicon carbide as a main component, and more preferably a silicon-silicon carbide composite material or silicon carbide. When the material of the columnar honeycomb structural portion 11 is a silicon-silicon carbide composite material as a main component, it means that the columnar honeycomb structural portion 11 contains 90 mass% or more (total mass) of the silicon-silicon carbide composite material of the entire columnar honeycomb structural portion. Here, the silicon-silicon carbide composite material contains silicon carbide particles as an aggregate and silicon as a binder for binding the silicon carbide particles, and preferably a plurality of silicon carbide particles are bound together with silicon so that fine pores are formed between the silicon carbide particles. When the material of the honeycomb structure 10 contains silicon carbide as a main component, it means that the honeycomb structure 10 contains 90 mass% or more (total mass) of silicon carbide in the entire honeycomb structure.

When the material of the columnar honeycomb structural portions 11 is a silicon-silicon carbide composite material, the ratio of the "mass of silicon as a binder" contained in the columnar honeycomb structural portions 11 to the sum of the "mass of silicon carbide particles as an aggregate" contained in the columnar honeycomb structural portions 11 and the "mass of silicon as a binder" contained in the columnar honeycomb structural portions 11 is preferably 10 to 40 mass%, and more preferably 15 to 35 mass%. If the content is 10% by mass or more, the strength of the columnar honeycomb structural portion 11 can be sufficiently maintained. If the content is 40% by mass or less, the shape is easily maintained during firing.

The shape of the cells in a cross section perpendicular to the direction of extension of the cells 15 is not limited, and is preferably quadrangular, hexagonal, octagonal or a combination thereof. Among them, a quadrangle and a hexagon are preferable. By forming the cell shape in the above-described shape, the pressure loss when the exhaust gas flows through the honeycomb structure 10 is reduced, and the purification performance of the catalyst is excellent. In particular, a rectangular shape is preferable from the viewpoint of easy combination of structural strength and heating uniformity.

The thickness of the partition wall 13 partitioning the compartment 15 is preferably 0.1 to 0.3mm, and more preferably 0.15 to 0.25 mm. By setting the thickness of the partition walls 13 to 0.1mm or more, the strength of the honeycomb structure can be suppressed from being lowered. When the thickness of the partition walls 13 is 0.3mm or less, an increase in pressure loss when exhaust gas flows can be suppressed when the honeycomb structure is used as a catalyst carrier and a catalyst is supported thereon. In the present invention, the thickness of the partition wall 13 is defined as: the length of a portion passing through the partition wall 13 in a line segment connecting the centers of gravity of the adjacent compartments 15 in a cross section perpendicular to the extending direction of the compartments 15.

In the honeycomb structure 10, the cell density is preferably 40 to 150 cells/cm in a cross section perpendicular to the flow path direction of the cells 15²More preferably 70 to 100 compartments/cm². By setting the cell density in the above range, the purification performance of the catalyst can be improved in a state where the pressure loss when the exhaust gas flows through is reduced. If the cell density is lower than 40 cells/cm²The catalyst supporting area may decrease. If the cell density is higher than 150 cells/cm²When the honeycomb structure 10 is used as a catalyst carrier and carries a catalyst, the pressure loss when exhaust gas flows may increase. The cell density is: the number of cells divided by the area of one bottom surface portion of the columnar honeycomb structural portion 11 excluding the outer side wall 12 portion.

The outer peripheral wall 12 of the honeycomb structure 10 is useful in terms of ensuring the structural strength of the honeycomb structure 10 and preventing the fluid flowing through the cells 15 from leaking from the outer peripheral wall 12. Specifically, the thickness of the outer peripheral wall 12 is preferably 0.1mm or more, more preferably 0.15mm or more, and further preferably 0.2mm or more. However, if the outer peripheral wall 12 is too thick, the strength is too high, and the strength balance with the partition wall 13 is broken, so that the thermal shock resistance is lowered, and therefore, the thickness of the outer peripheral wall 12 is preferably 1.0mm or less, more preferably 0.7mm or less, and further preferably 0.5mm or less. Here, the thickness of the outer peripheral wall 12 is defined as: the thickness in the normal direction of the tangent line of the outer peripheral wall 12 at the measurement site when the site of the outer peripheral wall 12 whose thickness is to be measured is observed at the cross section perpendicular to the extending direction of the compartment.

The partition walls 13 may be porous. The porosity of the partition wall 13 is preferably 35 to 60%, more preferably 35 to 45%. If the porosity is 35% or more, the deformation during firing is more easily suppressed. If the porosity is 60% or less, the strength of the honeycomb structure can be sufficiently maintained. The porosity is a value measured by a mercury porosimeter.

The average pore diameter of the partition walls 13 of the columnar honeycomb structure portion 11 is preferably 2 to 15 μm, and more preferably 4 to 8 μm. If the average pore diameter is 2 μm or more, the resistivity can be suppressed from becoming excessively large. If the average pore diameter is 15 μm or less, the resistivity can be suppressed to be excessively small. The average pore diameter is a value measured by a mercury porosimeter.

The honeycomb structure 10 has a pair of electrode layers 14a and 14b, and the pair of electrode layers 14a and 14b are arranged on the surface of the outer peripheral wall 12 of the columnar honeycomb structure 11 so as to face each other with the center axis of the columnar honeycomb structure 11 interposed therebetween.

The formation region of the electrode layers 14a and 14b is not particularly limited, and from the viewpoint of improving the uniform heat generation property of the columnar honeycomb structure portion 11, the electrode layers 14a and 14b are preferably provided on the outer surface of the outer peripheral wall 12 so as to extend in a band-like shape along the circumferential direction of the outer peripheral wall 12 and the extending direction of the cells 15. Specifically, from the viewpoint of facilitating the axial diffusion of the current to the electrode layers 14a and 14b, it is desirable that the respective electrode layers 14a and 14b extend over 80% or more, preferably 90% or more, and more preferably the entire length between both bottom surfaces of the columnar honeycomb structural portion 11. In addition, the electrode layers 14a, 14b may be scattered on the outer surface of the outer peripheral wall 12. In the case where the electrode layers 14a and 14b are scattered, it is preferable to provide the outer surface of the outer peripheral wall 12 at equal intervals in the circumferential direction of the outer peripheral wall 12 and in the extending direction of the cells 15, since the uniform heat generation property of the columnar honeycomb structural portion 11 can be improved. The electrode layers 14a and 14b shown in fig. 1 and 2 are provided such that the pair of electrode layers 14a and 14b are scattered on the surface of the columnar honeycomb structure 11. Specifically, an example is given in which a pair of electrode layers 14a, 14b are provided at 2 positions in the circumferential direction of the columnar honeycomb structural portion 11, respectively, and further, at 5 positions in the extending direction of the cells 15, at 10 positions in total.

The electrode layers 14a, 14b are made of a metal-ceramic hybrid material. With the electrically heated carrier 20 according to embodiment 1 of the present invention, it is not necessary to embed a metal extension member in the ceramic electrode layer in order to suppress breakage of the electrode layer. That is, since the electrode layers 14a and 14b themselves are made of ceramic containing metal, it is not necessary to form the electrode layers separately from the ceramic and the metal extension member having a large difference in thermal expansion coefficient as described above. Therefore, breakage of the electrode layer due to a difference in thermal expansion at the time of energization heating can be favorably suppressed.

Examples of the metal contained in the metal-ceramic mixture material of the electrode layers 14a and 14b include: a simple metal of Cr, Fe, Co, Ni, Si, or Ti, or an alloy containing at least one metal selected from the group consisting of these metals. The ceramic contained in the metal-ceramic mixture of the electrode layers 14a and 14b is not limited, and silicon carbide (SiC) or tantalum silicide (TaSi) may be used as an example₂) And chromium silicide (CrSi)₂) Examples of the metal compound such as metal silicide include a composite material (cermet) composed of a combination of one or more kinds of the above ceramics and one or more kinds of the above metals. Specific examples of the cermet include a composite material of silicon metal and silicon carbide, a metal silicide such as tantalum silicide or chromium silicide, and a composite material of silicon metal and silicon carbide, and further, from the viewpoint of reducing thermal expansion, a composite material obtained by adding one or two or more of insulating ceramics such as alumina, mullite, zirconia, cordierite, silicon nitride, and aluminum nitride to one or two or more of the above metals is included. The material of the electrode layers 14a and 14b is preferably a combination of a metal silicide such as tantalum silicide or chromium silicide, a composite material of metal silicon and silicon carbide, among the various metals and ceramics described above, because the metal and ceramics can be fired simultaneously with the columnar honeycomb structural portion to contribute to simplification of the manufacturing process.

The electrode layers 14a and 14b are preferably made of a metal-ceramic mixture material in which the metal content is 30 to 75 vol%. If the metal content is 30 vol% or more, the external metal terminal such as a power supply line can be joined by welding or welding. If the metal content is 75 vol% or less, the protective layer can be prevented from cracking due to thermal expansion becoming more severe than the protective layer. The ratio of the metal in the electrode layers 14a and 14b is more preferably 40 to 75 vol%, and still more preferably 60 to 75 vol%, from the viewpoint of reduction in electric resistance.

The honeycomb structure 10 has protective layers 17a, 17b, and the protective layers 17a, 17b cover the electrode layers 14a, 14b so that at least a part of the electrode layers 14a, 14b is exposed. As will be described later, the portions 18 of the electrode layers 14a and 14b, which are exposed from the protective layers 17a and 17b, are electrically connected to the metal terminals 21a and 21 b. According to this configuration, the electrode layers 14a and 14b are protected by the protective layers 17a and 17b, and an increase in resistance due to deterioration of the electrode layers 14a and 14b can be favorably suppressed. The protective layers 17a and 17b have a function of protecting the electrode layers 14a and 14b from deterioration, and for example, have a function of preventing the electrode layers 14a and 14b from oxidation.

As the material of the protective layers 17a and 17b, ceramics, glass, or a composite material of ceramics and glass can be used. For example, a material containing 50% by volume or more, more preferably 60% by volume or more, and still more preferably 70% by volume or more of glass can be used as the composite material. Examples of the ceramics constituting the protective layers 17a and 17b include: SiO 2₂System, Al₂O₃SiO 2₂－Al₂O₃SiO 2₂－ZrO₂SiO 2₂－Al₂O₃－ZrO₂And (d) a ceramic. Examples of the glass constituting the protective layers 17a and 17b include: b of lead-free system₂O₃－Bi₂O₃System, B₂O₃－ZnO－Bi₂O₃System, B₂O₃-ZnO based, V₂O₅－P₂O₅System, SnO-P₂O₅System, SnO-ZnO-P₂O₅SiO 2₂－B₂O₃－Bi₂O₃SiO 2₂－Bi₂O₃－Na₂O-based glass, etc.

The thickness of each electrode layer 14a, 14b is preferably 0.01 to 5mm, more preferably 0.01 to 3 mm. By setting the thickness within the above range, the uniform heat generation property can be improved. If the thickness of each of the electrode layers 14a and 14b is 0.01mm or more, the resistance can be appropriately controlled to generate heat more uniformly. If the thickness of each of the electrode layers 14a and 14b is 5mm or less, the possibility of breakage at the time of can filling is reduced. The thickness of each electrode layer 14a, 14b is defined as: when a portion of the electrode layer whose thickness is to be measured is observed at a cross section perpendicular to the extending direction of the cell, the thickness of the outer surface of each of the electrode layers 14a and 14b in the direction of the normal to the tangent line at the measurement portion is measured.

The maximum thickness of the protective layers 17a and 17b is preferably 1.5 times or more, respectively, the average thickness of the electrode layers 14a and 14 b. That is, the maximum thickness of the protective layers 17a and 17b covering the electrode layers 14a and 14b is preferably 1.5 times or more of the average value (average thickness of the electrode layer 14 a) when the thicknesses of the electrode layers 14a and 14b are measured at arbitrary multiple points. The electrode layers 14a and 14b made of the metal-ceramic mixture material have a larger thermal expansion at the time of energization heating than the protective layers 17a and 17 b. However, by setting the maximum thickness of the protective layers 17a, 17b to 1.5 times or more the average thickness of the electrode layers 14a, 14b, deformation due to thermal expansion of the electrode layers 14a, 14b can be suppressed well. Therefore, breakage and the like of the electrode layers 14a and 14b can be favorably suppressed. Since the protective layers 17a and 17b have higher strength as they are thicker, the maximum thicknesses of the protective layers 17a and 17b are more preferably 2 times or more, and still more preferably 3 times or more, respectively, the average thicknesses of the electrode layers 14a and 14 b.

When the maximum thicknesses of the protective layers 17a and 17b are each 1.5 times or more the average thickness of the electrode layers 14a and 14b, for example, only a part of the electrode layers 14a and 14b may be formed to have the same thickness as the maximum thicknesses of the protective layers 17a and 17b, and the part having the part of the thicknesses of the electrode layers 14a and 14b may be a part 18 of the electrode layers 14a and 14b, which is exposed from the protective layers 17a and 17 b. The electrode layers 14a and 14b may be buried in the protective layers 17a and 17b, and the exposed portions 18 may be formed by processing a part of the protective layers 17a and 17b as necessary to dig out the electrode layers 14a and 14 b.

By making the resistivity of each of the electrode layers 14a and 14b lower than the resistivity of the columnar honeycomb structure portion 11, current can easily flow preferentially through the electrode layers, and the current can easily diffuse in the flow path direction and the circumferential direction of the cells when energized. The resistivity of the electrode layers 14a and 14b is preferably 1/10 or less, more preferably 1/20 or less, and still more preferably 1/30 or less, of the resistivity of the columnar honeycomb structure 11. However, if the difference in resistivity between the two is too large, the current concentrates between the ends of the opposing electrode layers, and heat generation in the columnar honeycomb structure portion is biased, and therefore, the resistivity of the electrode layers 14a and 14b is preferably 1/200 or more, more preferably 1/150 or more, and still more preferably 1/100 or more of the resistivity of the columnar honeycomb structure portion 11. In the present invention, the resistivity of the electrode layers 14a and 14b is a value measured at 400 ℃ by a four-terminal method.

As shown in fig. 3, the electrode layers 14a and 14b may be constituted by a support portion 22 on the surface side of the outer peripheral wall 12 of the columnar honeycomb structural portion 11 and a protruding portion 23 rising from the support portion 22. In the configuration of fig. 3, the protective layers 17a and 17b cover the electrode layers 14a and 14b so as to expose at least a part of the surface of the protruding portion 23. The shapes of the support portion 22 and the protruding portion 23 are not particularly limited, and may be, for example, flat plates having a plane such as a circle, an ellipse, or a polygon, or bars extending over a predetermined length. The sizes of the support portion 22 and the protruding portion 23 are not particularly limited, and for example, the thickness of the support portion 22 may be 50 to 300 μm, and the thickness of the protruding portion 23 may be 100 to 200 μm.

The electrode layers 14a and 14b may have a shape shown in a schematic plan view of fig. 4. That is, the support portion 22 of the electrode layers 14a and 14b may be formed of a plurality of linear portions 24, and the plurality of linear portions 24 may extend radially along the surface of the outer peripheral wall 12 of the columnar honeycomb structural portion 11 with a point directly below the protruding portion 23 as a center. In this configuration, the protruding portion 23 may be formed in a cylindrical shape, an elliptic cylindrical shape, a prismatic shape, or the like. In fig. 4, the plurality of linear portions 24 radially extending around a point directly below the protruding portion 23 are composed of 6 linear portions in total, and the angles θ formed by the 6 linear portions (the angles formed by the center lines 29 of the adjacent 2 linear portions 24) are each substantially 60 °. The angles θ formed by the plurality of linear portions 24 do not need to be the same, and may be different. The number of the linear portions 24 is not particularly limited, and may be 3, 4, or 5 or more. The length L1 and the width d of the straight portion 24 are not particularly limited, and may be appropriately designed in accordance with the relationship with the number of electrode layers 14a and 14b provided in the columnar honeycomb structural portion 11, the size of the protruding portion 23, and the like. For example, in the case of the electrode layers 14a and 14b having the shape shown in FIG. 4, the cross-section of the electrode layers 14a and 14b perpendicular to the direction in which the protruding portion 23 protrudes may be a circle having a diameter of 0.5 to 2 μm, the length L1 of the linear portion 24 may be 5 to 30 μm, and the width d may be 0.5 to 2 μm. The support portions 22 of the electrode layers 14a and 14b may further include at least one branch portion branched from a plurality of linear portions 24 extending radially.

As shown in fig. 5, the electrode layers 14a and 14b configured as shown in fig. 4 are preferably provided in a plurality of regions on the columnar honeycomb structural portion 11 with an interval L2. With this configuration, the uniform heat generation property of the columnar honeycomb structural portion 11 can be further improved. The interval L2 is not particularly limited, and can be appropriately designed in accordance with the relationship with the number, size, and the like of the electrode layers 14a and 14b provided in the columnar honeycomb structural portion 11. For example, when the length L1 of the straight portion 24 of the electrode layers 14a and 14b is 5 to 30 μm, the distance L2 may be 15 to 60 mm.

(1-2. Metal terminal)

The pair of metal terminals 21a, 21b are arranged such that: one metal terminal 21a of the pair of metal terminals is opposed to the other metal terminal 21b with the center axis of the columnar honeycomb structural portion 11 of the honeycomb structure 10 interposed therebetween, and is provided on each of the pair of electrode layers 14a and 14 b. The metal terminals 21a, 21b are electrically connected to the electrode layers 14a, 14b at the portions 18 of the electrode layers 14a, 14b where the self- protective layers 17a, 17b are exposed. Thus, if a voltage is applied to the metal terminals 21a and 21b through the electrode layers 14a and 14b, electricity can be passed through the metal terminals to generate heat in the honeycomb structure 10 by joule heat. Therefore, the honeycomb structure 10 can also be preferably used as a heater. The voltage to be applied is preferably 12 to 900V, more preferably 64 to 600V, and the voltage to be applied can be changed as appropriate. The portions 18 of the electrode layers 14a, 14b exposed from the protective layers 17a, 17b may be portions joined to the metal terminals 21a, 21 b. In addition, the metal terminals 21a and 21b may be electrically connected to the electrode layers 14a and 14b through another conductive material at portions 18 of the electrode layers 14a and 14b, which are exposed from the protective layers 17a and 17 b.

The material of the metal terminals 21a, 21b is not particularly limited, and a metal simple substance, an alloy, or the like may be used, and from the viewpoint of corrosion resistance, resistivity, and linear expansion coefficient, for example, an alloy containing at least one selected from the group consisting of Cr, Fe, Co, Ni, and Ti is preferably used, and stainless steel and an Fe — Ni alloy are more preferably used. The shape and size of the metal terminals 21a and 21b are not particularly limited, and can be appropriately designed according to the size and current carrying performance of the electrically heated carrier 20.

By supporting the catalyst on the electrically heated carrier 20, the electrically heated carrier 20 can be used as a catalyst. For example, a fluid such as automobile exhaust gas may be passed through the flow paths of the plurality of cells 15. Examples of the catalyst include a noble metal-based catalyst and a catalyst other than these. Examples of the noble metal-based catalyst include: a three-way catalyst, an oxidation catalyst, or a three-way catalyst comprising a co-catalyst such as ceria or zirconia having a noble metal such as platinum (Pt), palladium (Pd) or rhodium (Rh) supported on the surface of alumina pores, or a three-way catalyst, an oxidation catalyst, or a three-way catalyst comprising an alkaline earth metal and platinum as a Nitrogen Oxide (NO)_x) NO of the storage component_xA trap reduction catalyst (LNT catalyst). Examples of the catalyst not using a noble metal include: NO containing copper-or iron-substituted zeolite_xSelective reduction catalysts (SCR catalysts), and the like. In addition, 2 or more catalysts selected from the group consisting of these catalysts may be used. The method for supporting the catalyst is also not particularly limited, and the catalyst may be supported by a conventional method for supporting the catalyst on the honeycomb structure.

(2. method for producing Electrical heating Carrier)

Next, a method for manufacturing the electrically heated carrier 20 according to the present invention will be exemplarily described. In one embodiment, the method for manufacturing the electrically heated carrier 20 of the present invention includes: a step a1 of obtaining an unfired honeycomb structure portion with an electrode layer forming paste attached thereto; a step a2 of firing the unfired honeycomb structure portion with the electrode layer forming paste attached thereto to obtain a honeycomb fired body; a step a3 of providing a protective layer on the honeycomb fired body to obtain a honeycomb structure; and a step a4 of welding the metal terminals to the honeycomb structure.

The process a1 is: and a step of preparing a honeycomb formed body which is a precursor of the honeycomb structure portion, and applying an electrode layer forming paste to a side surface of the honeycomb formed body to obtain an unfired honeycomb structure portion with the electrode layer forming paste attached thereto. The honeycomb formed body can be produced by a known method for producing a honeycomb formed body in the method for producing a honeycomb structure. For example, first, a metal silicon powder (metal silicon), a binder, a surfactant, a pore former, water, and the like are added to a silicon carbide powder (silicon carbide) to prepare a molding material. The mass of the metal silicon is preferably 10 to 40% by mass relative to the total mass of the silicon carbide powder and the metal silicon. The average particle diameter of the silicon carbide particles in the silicon carbide powder is preferably 3 to 50 μm, and more preferably 3 to 40 μm. The average particle diameter of the metal silicon (metal silicon powder) is preferably 2 to 35 μm. The average particle diameter of the silicon carbide particles and the metal silicon (metal silicon particles) is: an arithmetic average particle diameter on a volume basis when the frequency distribution of particle sizes is measured by a laser diffraction method. The silicon carbide particles are fine particles of silicon carbide constituting the silicon carbide powder, and the metal silicon particles are fine particles of metal silicon constituting the metal silicon powder. In addition, the above is the compounding of the molding material when the material of the honeycomb structural portion is a silicon-silicon carbide composite material, and when the material of the honeycomb structural portion is silicon carbide, metallic silicon is not added.

Examples of the binder include methyl cellulose, hydroxypropylmethyl cellulose, hydroxypropoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol. Of these binders, it is preferable to use both methylcellulose and hydroxypropyloxycellulose. The content of the binder is preferably 2.0 to 10.0 parts by mass when the total mass of the silicon carbide powder and the metal silicon powder is 100 parts by mass.

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

As the surfactant, ethylene glycol, dextrin, fatty acid soap, polyhydric alcohol, and the like can be used. The surfactant may be used alone in 1 kind, or may be used in combination with 2 or more kinds. 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 metal silicon powder is 100 parts by mass.

The pore-forming material is not particularly limited as long as it forms pores after firing, and examples thereof include graphite, starch, a foaming resin, a water-absorbent resin, and silica gel. The pore former is preferably contained in an amount of 0.5 to 10.0 parts by mass, based on 100 parts by mass of the total of the silicon carbide powder and the metal silicon powder. The average particle diameter of the pore-forming material is preferably 10 to 30 μm. If the average particle diameter of the pore-forming material is less than 10 μm, pores may not be sufficiently formed. If the average particle diameter of the pore-forming material is larger than 30 μm, the die may be clogged during molding. The average particle size of the pore-forming material is: an arithmetic average particle diameter on a volume basis when the frequency distribution of particle sizes is measured by a 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 material was kneaded to form a kneaded material, and then, the kneaded material was extrusion-molded to produce a honeycomb molded body. In the extrusion molding, a die having a desired overall shape, cell shape, partition wall thickness, cell density, and the like may be used. Next, the obtained honeycomb formed body is preferably dried. In the case where the center axial length of the honeycomb formed body is not a desired length, both bottom portions of the honeycomb formed body may be cut to form a desired length. The honeycomb formed body after drying is referred to as a honeycomb dried body.

Next, an electrode layer forming paste for forming an electrode layer was prepared. The electrode layer forming paste can be formed by appropriately adding and kneading various additives to raw material powders (metal powders, ceramic powders, and the like) blended in accordance with the required characteristics of the electrode layer. When the electrode layer is formed in a stacked structure, the average particle size of the metal powder in the paste for the second electrode layer is larger than the average particle size of the metal powder in the paste for the first electrode layer, and thus the bonding strength between the metal terminal and the electrode layer tends to be improved. The average particle diameter of the metal powder means: an arithmetic average particle diameter on a volume basis when the frequency distribution of particle sizes is measured by a laser diffraction method.

Next, the obtained electrode layer forming paste was applied to the side surface of a honeycomb formed body (typically, a dried honeycomb body) to obtain an unfired honeycomb structure portion with the electrode layer forming paste attached thereto. The method of preparing the electrode layer forming paste and the method of applying the electrode layer forming paste to the honeycomb formed body can be performed according to a known method of manufacturing a honeycomb structure, but the content ratio of the metal in the electrode layer forming paste may be made higher than the content ratio of the metal in the honeycomb structure portion, or the particle diameter of the metal particles may be reduced so that the resistivity of the electrode layer is lower than the resistivity of the honeycomb structure portion.

As a modification of the method for producing a honeycomb structure, in step a1, the honeycomb formed body may be fired once before the electrode layer forming paste is applied. That is, in this modification, a honeycomb fired body is prepared by firing a honeycomb formed body, and an electrode layer forming paste is applied to the honeycomb fired body.

In step a2, the unfired honeycomb structure portion with the electrode layer forming paste attached thereto was fired to obtain a honeycomb structure. The unfired honeycomb structure portion with the electrode layer forming paste attached thereto may be dried before firing. Further, degreasing may be performed before firing to remove a binder and the like. The firing conditions are preferably heating at 1400 to 1500 ℃ for 1 to 20 hours in an inert atmosphere such as nitrogen or argon. Further, it is preferable to perform oxidation treatment at 1200 to 1350 ℃ for 1 to 10 hours after firing in order to improve durability. The method of degreasing and firing is not particularly limited, and firing may be performed using an electric furnace, a gas furnace, or the like.

In step a3, a protective layer is provided so as to cover the electrode layer of the honeycomb fired body, thereby obtaining a honeycomb structure. At this time, the protective layer may be provided to expose at least a portion of the electrode layer. Alternatively, the protective layer may be formed so as to cover the entire electrode layer, and then a part of the protective layer may be removed to expose at least a part of the electrode layer. The protective layer may be formed by a sputtering method or by applying or spraying a material and then heating, although the method depends on the material. The electrode layer and the protective layer may be formed in the same step, or may be formed by simultaneous firing. Specifically, a honeycomb structure provided with an electrode layer and a protective layer can be produced by further providing a protective layer on the unfired honeycomb structure portion to which the electrode layer forming paste is applied and then firing the resultant.

In step a4, metal terminals are welded to the exposed surfaces of the electrode layers of the honeycomb structure. As the welding method, a method of performing laser welding from the metal terminal side is preferable from the viewpoint of control of the welding area and production efficiency.

< embodiment 2 >

The electrically heated carrier 30 according to embodiment 2 of the present invention has the same configuration as the electrically heated carrier 20 according to embodiment 1, except that it does not include a metal terminal. That is, the electrically heated carrier 30 according to embodiment 2 has the same configuration as the honeycomb structure 10 of the electrically heated carrier 20 according to embodiment 1 shown in fig. 2. The electrically heated carrier 30 can be used as an electrically heated carrier having a metal terminal in the same manner as in embodiment 1 by disposing a metal terminal in a portion of the electrode layer exposed from the protective layer and electrically connecting the metal terminal.

(3. exhaust gas purifying apparatus)

The electrically heated vehicle according to the embodiment of the present invention described above can be used for an exhaust gas purification apparatus. The exhaust gas purification device includes an electrically heated carrier and a tank for holding the electrically heated carrier. In the exhaust gas purification device, an electrically heated carrier is provided in the middle of an exhaust gas flow path through which exhaust gas from an engine flows. As the can body, a metal cylindrical member or the like that houses the electrically heated carrier can be used.