WO2021106261A1 - Electrical heating-type carrier, and exhaust gas purification device - Google Patents

Abstract

An electrical heating-type carrier, provided with: a columnar honeycomb structure made of a ceramic, the columnar honeycomb structure having an outer peripheral wall, and partition walls provided on the inner side of the outer peripheral wall, the partition walls defining and forming a plurality of cells which penetrate from one end surface to the other end surface and form channels; an electrode layer provided on the surface of the outer peripheral wall of the columnar honeycomb structure; an electroconductive base layer provided on the electrode layer; a metal electrode connected on the base layer by a joint portion; and an anti-oxidation layer for protecting the joint portion from exhaust gas.

Description

Electric heating type carrier and exhaust gas purification device

The present invention relates to an electrically heated carrier and an exhaust gas purifying device.

In recent years, an electric heating catalyst (EHC) has been proposed in order to improve the deterioration of exhaust gas purification performance immediately after starting the engine. In EHC, for example, a metal electrode is connected to a columnar honeycomb structure made of conductive ceramics, and the honeycomb structure itself is heated by energization so that the temperature can be raised to the active temperature of the catalyst before starting the engine. Is. In EHC, in order to obtain a sufficient catalytic effect, it is desired to reduce temperature unevenness in the honeycomb structure to obtain a uniform temperature distribution.

In order to pass an electric current through the EHC, it is necessary to join the metal electrode connected to the external wiring to the EHC. The joining method includes fixing by thermal spraying, laser welding, brazing and the like.

Further, Patent Document 1 discloses a technique of applying thermal energy from the metal terminal (metal electrode) side to join the metal electrode on the electrode layer of the honeycomb structure by welding. Then, it is described that according to such a configuration, it is possible to provide a conductive honeycomb structure having improved bonding reliability with a metal electrode.

Japanese Unexamined Patent Publication No. 2018-172258

In Patent Document 1, a stress relaxation layer (base layer) is provided in the electrode layer to reduce repeated fatigue of the ceramic honeycomb structure due to breakage during welding and thermal cycle. However, since EHC is usually used at a high temperature (800 to 1000 ° C.) in an exhaust gas atmosphere of an automobile or the like, its physical properties change depending on the energy at the time of joining at a joining part such as a welded part. When the joint part is exposed to the exhaust gas of an automobile or the like, the oxidation resistance tends to decrease. As a result, stress relaxation is possible by the base layer, but there is a possibility that the material strength due to oxidation is lowered and the joint portion is damaged.

The present invention has been created in view of the above circumstances, and provides an electrically heated carrier and an exhaust gas purifying device capable of satisfactorily suppressing oxidation of a joint portion connecting a base layer and a metal electrode. Is the subject. Another object of the present invention is to provide an electrically heated carrier and an exhaust gas purifying device capable of satisfactorily suppressing the oxidation of the fixed layer that fixes the metal electrode to the electrode layer.

As a result of diligent studies, the present inventor has found that the above problems can be solved by providing an antioxidant layer for protecting the joint portion connecting the base layer and the metal electrode from exhaust gas. That is, the present invention is specified as follows.
(1) A columnar honeycomb made of ceramics having an outer peripheral wall and a partition wall which is disposed inside the outer peripheral wall and forms a plurality of cells which form a flow path from one end face to the other end face. Structure and
An electrode layer arranged on the surface of the outer peripheral wall of the columnar honeycomb structure and
A conductive base layer provided on the electrode layer and
A metal electrode connected to the base layer by a joint site and
An antioxidant layer for protecting the joint site from exhaust gas,
An electroheated carrier equipped with.
(2) A columnar honeycomb made of ceramics having an outer peripheral wall and a partition wall which is disposed inside the outer peripheral wall and forms a plurality of cells which form a flow path from one end face to the other end face. Structure and
An electrode layer arranged on the surface of the outer peripheral wall of the columnar honeycomb structure and
A metal electrode provided on the electrode layer and
A fixed layer provided so as to cover the metal electrode and fixing the metal electrode to the electrode layer,
An antioxidant layer provided so as to cover the fixed layer and
An electroheated carrier equipped with.
(3) With the electrically heated carrier according to (1) or (2),
A metal tubular member for holding the electrically heated carrier, and
Exhaust gas purification device with.

According to the present invention, it is possible to provide an electrically heated carrier and an exhaust gas purifying device capable of satisfactorily suppressing oxidation of a joint portion connecting a base layer and a metal electrode. Further, according to the present invention, it is possible to provide an electrically heated carrier and an exhaust gas purifying device capable of satisfactorily suppressing oxidation of a fixed layer that fixes a metal electrode to an electrode layer.

FIG. 5 is a schematic cross-sectional view perpendicular to the stretching direction of the cell of the electrically heated carrier according to the embodiment of the present invention. It is a schematic appearance figure of the columnar honeycomb structure and the electrode layer in embodiment of this invention. It is a top view which shows the arrangement example of the base layer of the electric heating type carrier in embodiment of this invention. FIG. 5 is a schematic cross-sectional view of a columnar honeycomb structure, an electrode layer, a base layer, a joint portion, a metal electrode, and an antioxidant layer according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view of a columnar honeycomb structure, an electrode layer, a base layer, a joint portion, a metal electrode, and an antioxidant layer according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view of a columnar honeycomb structure, an electrode layer, a base layer, a joint portion, a metal electrode, and an antioxidant layer according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view of a columnar honeycomb structure, an electrode layer, a base layer, a joint portion, a metal electrode, and an antioxidant layer according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view of a columnar honeycomb structure, an electrode layer, a base layer, a joint portion, a metal electrode, and an antioxidant layer according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view of a columnar honeycomb structure, an electrode layer, a base layer, a joint portion, a metal electrode, and an antioxidant layer according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view of a columnar honeycomb structure, an electrode layer, a base layer, a joint portion, a metal electrode, and an antioxidant layer according to an embodiment of the present invention. It is a schematic diagram which shows the state of joining the base layer of the columnar honeycomb structure and the metal electrode in the embodiment of this invention by laser welding or the like. FIG. 5 is a schematic cross-sectional view of a columnar honeycomb structure, an electrode layer, a fixed layer, a metal electrode, and an antioxidant layer according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view of a columnar honeycomb structure, an electrode layer, a base layer, a joint portion, a metal electrode, and an antioxidant layer according to an embodiment of the present invention.

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

(1. Electric heating type carrier)
FIG. 1 is a schematic cross-sectional view of the electrically heated carrier 10 according to the embodiment of the present invention, which is perpendicular to the stretching direction of the cell 18. The electrically heated carrier 10 includes a columnar honeycomb structure 11, electrode layers 13a and 13b arranged on the surface of the outer peripheral wall 12 of the columnar honeycomb structure 11, and a base layer 16 provided on the electrode layers 13a and 13b. And metal electrodes 14a and 14b connected to the base layer 16 by the joint portion 20, and an antioxidant layer 21 for protecting the joint portion 20 from exhaust gas. In FIG. 1, the joining portion 20 and the antioxidant layer 21 for protecting the joining portion 20 from exhaust gas are simplified, but the electrically heated carrier 10 according to the embodiment of the present invention has various forms. In each embodiment described later, the details will be described together with the drawings.

(1-1. Columnar honeycomb structure)
FIG. 2 shows a schematic external view of the columnar honeycomb structure 11 and the electrode layers 13a and 13b according to the embodiment of the present invention. The columnar honeycomb structure 11 includes an outer peripheral wall 12 and a partition wall 19 which is arranged inside the outer peripheral wall 12 and which partitions a plurality of cells 18 which penetrate from one end face to the other end face to form a flow path. Have.

The outer shape of the columnar honeycomb structure 11 is not particularly limited as long as it is columnar. For example, the bottom surface is a circular columnar shape (cylindrical shape), the bottom surface is an oval-shaped columnar shape, and the bottom surface is a polygonal shape (quadrangle, pentagon, hexagon, heptagon). , Octagon, etc.) can be shaped like a columnar shape. ^{Further, the size of the columnar honeycomb structure 11 is preferably 2000 to 20000 mm 2} and preferably 5000 to 15000 mm for the reason of improving heat resistance (suppressing cracks entering the circumferential direction of the outer peripheral wall). it is more preferably ^2.

The columnar honeycomb structure 11 is made of ceramics and has conductivity. As long as the conductive columnar honeycomb structure 11 is energized and can generate heat by Joule heat, the electrical resistivity of the ceramic is not particularly limited, but is preferably 1 to 200 Ωcm, and is preferably 10 to 100 Ωcm. Is more preferable. In the present invention, the electrical resistivity of the columnar honeycomb structure 11 is a value measured at 400 ° C. by the four-terminal method.

The material of the columnar honeycomb structure 11 is not limited, but includes a group consisting of oxide-based ceramics such as alumina, mullite, zirconia and cordierite, and non-oxide ceramics such as silicon carbide, silicon nitride and aluminum nitride. You can choose. Further, a silicon carbide-metal silicon composite material, a silicon carbide / graphite composite material, or the like can also be used. Among these, from the viewpoint of achieving both heat resistance and conductivity, the material of the columnar honeycomb structure 11 preferably contains a silicon-silicon carbide composite material or ceramics containing silicon carbide as a main component. When the material of the columnar honeycomb structure 11 is mainly composed of a silicon-silicon carbide composite material, the columnar honeycomb structure 11 contains the silicon-silicon carbide composite material (total mass) for a total of 90 masses. It means that it contains% or more. 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 a plurality of silicon carbide particles are formed between the silicon carbide particles. It is preferably bonded by silicon so as to form pores. When the material of the columnar honeycomb structure 11 is mainly composed of silicon carbide, it means that the columnar honeycomb structure 11 contains silicon carbide (total mass) in an amount of 90% by mass or more of the whole. means.

When the columnar honeycomb structure 11 contains a silicon-silicon carbide composite material, the “mass of silicon carbide particles as aggregate” contained in the columnar honeycomb structure 11 and the columnar honeycomb structure 11 are contained. The ratio of the "mass of silicon as a binder" contained in the columnar honeycomb structure 11 to the total of the "mass of silicon as a composite" is preferably 10 to 40% by mass, preferably 15 to 35. It is more preferably mass%. When it is 10% by mass or more, the strength of the columnar honeycomb structure 11 is sufficiently maintained. When it is 40% by mass or less, it becomes easy to maintain the shape at the time of firing.

The shape of the cell in the cross section perpendicular to the extending direction of the cell 18 is not limited, but it is preferably a quadrangle, a hexagon, an octagon, or a combination thereof. Among these, a quadrangle and a hexagon are preferable. By making the shape of the cell in this way, the pressure loss when the exhaust gas is passed through the columnar honeycomb structure 11 is reduced, and the purification performance of the catalyst is excellent. A quadrangle is particularly preferable from the viewpoint of easily achieving both structural strength and heating uniformity.

The thickness of the partition wall 19 for partitioning the cell 18 is preferably 0.1 to 0.3 mm, more preferably 0.15 to 0.25 mm. When the thickness of the partition wall 19 is 0.1 mm or more, it is possible to suppress a decrease in the strength of the honeycomb structure. When the thickness of the partition wall 19 is 0.3 mm or less, it is possible to suppress an increase in pressure loss when exhaust gas is flowed when the honeycomb structure is used as a catalyst carrier and the catalyst is supported. In the present invention, the thickness of the partition wall 19 is defined as the length of a portion of a line segment connecting the centers of gravity of adjacent cells 18 that passes through the partition wall 19 in a cross section perpendicular to the extending direction of the cell 18.

^{The columnar honeycomb structure 11 preferably has a cell density of 40 to 150 cells / cm 2} , and more preferably 70 to 100 cells / cm ² in a cross section perpendicular to the flow path direction of the cells 18. By setting the cell density in such a range, the purification performance of the catalyst can be improved while the pressure loss when the exhaust gas is passed is reduced. When the cell density is 40 cells / cm ² or more, a sufficient catalyst-supporting area is secured. When the cell density is 150 cells / cm ² or less, when the columnar honeycomb structure 11 is used as a catalyst carrier and the catalyst is supported, it is possible to prevent the pressure loss when the exhaust gas is flowed from becoming too large. The cell density is a value obtained by dividing the number of cells by the area of one bottom surface portion of the columnar honeycomb structure 11 excluding the outer peripheral wall 12 portion.

Providing the outer peripheral wall 12 of the columnar honeycomb structure 11 is useful from the viewpoint of ensuring the structural strength of the columnar honeycomb structure 11 and suppressing the fluid flowing through the cell 18 from leaking from the outer peripheral wall 12. Specifically, the thickness of the outer peripheral wall 12 is preferably 0.1 mm or more, more preferably 0.15 mm or more, and even more preferably 0.2 mm or more. However, if the outer peripheral wall 12 is made too thick, the strength becomes too high, the strength balance with the partition wall 19 is lost, and the heat impact resistance is lowered. Therefore, the thickness of the outer peripheral wall 12 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 12 is the normal direction with respect to the tangent line of the outer peripheral wall 12 at the measurement location when the portion of the outer peripheral wall 12 whose thickness is to be measured is observed in a cross section perpendicular to the extending direction of the cell. Defined as thickness.

The partition wall 19 can be made porous. The porosity of the partition wall 19 is preferably 35 to 60%, more preferably 35 to 45%. When the porosity is 35% or more, it becomes easier to suppress deformation during firing. When the porosity is 60% or less, the strength of the honeycomb structure is sufficiently maintained. Porosity is a value measured by a mercury porosimeter.

The average pore diameter of the partition wall 19 of the columnar honeycomb structure 11 is preferably 2 to 15 μm, more preferably 4 to 8 μm. When the average pore diameter is 2 μm or more, it is suppressed that the electrical resistivity becomes too large. When the average pore diameter is 15 μm or less, it is suppressed that the electrical resistivity becomes too small. The average pore diameter is a value measured by a mercury porosimeter.

(1-2. Electrode layer)
Electrode layers 13a and 13b are arranged on the surface of the outer peripheral wall 12 of the columnar honeycomb structure 11. The electrode layers 13a and 13b may be a pair of electrode layers 13a and 13b arranged so as to face each other with the central axis of the columnar honeycomb structure 11 interposed therebetween.

There are no particular restrictions on the formation regions of the electrode layers 13a and 13b, but from the viewpoint of enhancing the uniform heat generation of the columnar honeycomb structure 11, each of the electrode layers 13a and 13b is formed on the outer surface of the outer peripheral wall 12 of the outer peripheral wall 12. It is preferable to extend the cells in a strip shape in the circumferential direction and the extending direction of the cell. Specifically, each of the electrode layers 13a and 13b has a length of 80% or more, preferably a length of 90% or more, and more preferably a total length between both bottom surfaces of the columnar honeycomb structure 11. It is desirable that the current extends over the electrode layers 13a and 13b from the viewpoint that the current easily spreads in the axial direction.

The thickness of each of the electrode layers 13a and 13b is preferably 0.01 to 5 mm, more preferably 0.01 to 3 mm. By setting it in such a range, uniform heat generation can be enhanced. When the thickness of each of the electrode layers 13a and 13b is 0.01 mm or more, the electric resistance is appropriately controlled and heat can be generated more uniformly. If it is 5 mm or less, the risk of damage during canning is reduced. The thickness of each of the electrode layers 13a and 13b is such that when the portion of the electrode layer 13a and 13b whose thickness is to be measured is observed in a cross section perpendicular to the stretching direction of the cell, the measurement portion on the outer surface of each of the electrode layers 13a and 13b. Is defined as the thickness in the normal direction with respect to the tangent line in.

By making the electrical resistivity of each of the electrode layers 13a and 13b lower than the electrical resistivity of the columnar honeycomb structure 11, electricity can easily flow to the electrode layers 13a and 13b preferentially, and electricity flows in the cell flow path direction when energized. And it becomes easy to spread in the circumferential direction. The electrical resistivity of the electrode layers 13a and 13b is preferably 1/10 or less, more preferably 1/20 or less, and preferably 1/30 or less of the electrical resistivity of the columnar honeycomb structure 11. Even more preferable. However, if the difference between the electrical resistivitys of the two becomes too large, the current is concentrated between the ends of the opposing electrode layers 13a and 13b, and the heat generation of the columnar honeycomb structure is biased. Therefore, the electrical resistivity of the electrode layers 13a and 13b The ratio is preferably 1/200 or more, more preferably 1/150 or more, and even more preferably 1/100 or more of the electrical resistivity of the columnar honeycomb structure 11. In the present invention, the electrical resistivity of the electrode layers 13a and 13b is a value measured at 400 ° C. by the four-terminal method.

As the material of each of the electrode layers 13a and 13b, a metal, a conductive ceramic, or a composite material (cermet) of the metal and the conductive ceramic can be used. Examples of the metal include elemental metals of Cr, Fe, Co, Ni, Si and Ti, and alloys containing at least one metal selected from the group consisting of these metals. Examples of the conductive ceramics include, but are not limited to, silicon carbide (SiC), and examples thereof include metal compounds such as metal _{siliceates such as tantalum silicate (TaSi 2} ) and chromium _{silicate (CrSi 2).} Specific examples of the composite material (cermet) of metal and conductive ceramics include a composite material of metallic silicon and silicon carbide, a composite material of metal siliceous material such as tantalum silicate and chromium silicate, and a composite material of metallic silicon and silicon carbide, and further described above. From the viewpoint of reducing thermal expansion, a composite material obtained by adding one or more kinds of insulating ceramics such as alumina, mulite, zirconia, cordierite, silicon nitride and aluminum nitride to one or more kinds of metals can be mentioned. Among the various metals and conductive ceramics described above, the material of the electrode layers 13a and 13b is a columnar honeycomb that is a combination of a metal siliceate such as tantalum silicate or chromium silicate and a composite material of metallic silicon and silicon carbide. It is preferable because it can be fired at the same time as the structural part, which contributes to simplification of the manufacturing process.

(1-3. Base layer)
In the electroheating carrier 10 according to the embodiment of the present invention, the base layer 16 is provided on the electrode layers 13a and 13b. The base layer 16 can be formed on the surfaces of the electrode layers 13a and 13b, and is formed in a substantially flat plate shape (specifically, a curved shape along the outer surface of the electrode layers 13a and 13b). The base layer 16 has conductivity. The base layer 16 has the coefficient of thermal expansion of the electrode layers 13a and 13b (the coefficient of linear expansion of the electrode layers 13a and 13b is relatively small) and the coefficient of thermal expansion of the metal electrodes 14a and 14b (the coefficient of linear expansion of the metal electrodes 14a and 14b). May have a coefficient of thermal expansion between the two, and in this case, it has a function of absorbing the difference in thermal expansion that occurs between the electrode layers 13a and 13b and the metal electrodes 14a and 14b. There is.

The base layer 16 can be made of conductive ceramics. Examples of the ceramics constituting the base layer 16 include, but are not limited to, silicon carbide (SiC), and metal compounds such as metal _{silicates such as tantalum silicate (TaSi 2} ) and chromium _{silicate (CrSi 2).} Further, a composite material (cermet) composed of a combination of one or more ceramics and one or more metals can be mentioned. Specific examples of the cermet include a composite material of metallic silicon and silicon carbide, a composite material of metallic siliceous material such as tantalum silicate and chromium silicate, and a composite material of metallic silicon and silicon carbide, and further, thermal expansion to the above-mentioned one or more kinds of metals. From the viewpoint of reduction, a composite material to which one or more kinds of insulating ceramics such as alumina, mullite, zirconia, cordierite, silicon carbide and aluminum nitride are added can be mentioned.

The number and arrangement of the base layers 16 are not limited, and can be appropriately set within the range necessary for fixing the metal electrodes 14a and 14b. Further, the shape of the base layer 16 can be formed into any shape such as a circular shape, an elliptical shape, and a polygonal shape in a plan view. The shape of the base layer 16 is preferably circular or rectangular from the viewpoint of productivity and practicality.

(1-4. Metal electrode)
The metal electrodes 14a and 14b are connected to the base layer 16 by a joining portion 20. The metal electrodes 14a and 14b may be a pair of metal electrodes in which one metal electrode 14a is arranged so as to face the other metal electrode 14b with the central axis of the columnar honeycomb structure 11 interposed therebetween. Good. When a voltage is applied to the metal electrodes 14a and 14b via the electrode layers 13a and 13b, the metal electrodes 14a and 14b are energized and the columnar honeycomb structure 11 can be heated by Joule heat. Therefore, the electrically heated carrier 10 can be suitably used as a heater. The applied voltage is preferably 12 to 900 V, more preferably 64 to 600 V, but the applied voltage can be changed as appropriate.

As the material of the metal electrodes 14a and 14b, there are no particular restrictions as long as it is a metal, and a single metal, an alloy, or the like can be adopted. However, from the viewpoint of corrosion resistance, electrical resistance, and linear expansion rate, for example, Cr, Fe. , Co, Ni and Ti are preferably used as alloys containing at least one selected from the group, and stainless steel and Fe—Ni alloys are more preferable. The shapes and sizes of the metal electrodes 14a and 14b are not particularly limited, and can be appropriately designed according to the size of the electrically heated carrier 10 and the energization performance.

The metal electrodes 14a and 14b may have two or more electrode portions 15. Each electrode portion 15 may be fixed to the outer surface of the base layer 16. Here, the electrode portion 15 may be fixed to the base layer 16 by welding, or may be fixed to the electrode layers 13a and 13b by a fixing layer formed by thermal spraying.

In the embodiment shown in FIG. 3, the metal electrodes 14a and 14b each have three comb-shaped electrode portions 15, and each of the electrode portions 15 is fixed to two base layers 16. As described above, the electrical connection between the comb-shaped electrode portion 15 and the electrode layers 13a and 13b may be realized by two or more base layers 16 that are separated from each other.

Although the electrode portion 15 is formed in a comb shape in FIG. 3, it is fixed to the electrode layers 13a and 13b as long as it is fixed to the base layer 16 and can be electrically connected to the electrode layers 13a and 13b, or by spraying. Any shape can be adopted as long as it is possible.

(1-5. Antioxidant layer)
The electroheated carrier 10 according to the embodiment of the present invention includes an antioxidant layer 21 for protecting the joint portion 20 from exhaust gas. In the present invention, the structure of the joint portion 20 and the antioxidant layer 21 that protects the joint portion 20 has various forms. Hereinafter, each embodiment will be described in detail together with the drawings.

[Embodiment 1]
FIG. 4 shows a schematic cross-sectional view of the columnar honeycomb structure 11, the electrode layers 13a and 13b, the base layer 16, the joint portion 20, the metal electrodes 14a and 14b, and the antioxidant layer 21a according to the first embodiment of the present invention. In the first embodiment shown in FIG. 4, a second base layer or a second electrode layer 17 is provided between the electrode layers 13a and 13b and the base layer 16 for further relaxation of thermal stress. The second base layer or the second electrode layer 17 may not be provided, or a third layer for further relaxation of thermal stress may be provided on the second base layer or the second electrode layer 17. , Further may be provided.

The joint portion 20 connecting the base layer 16 and the metal electrodes 14a and 14b is, for example, when the metal electrodes 14a and 14b are provided on the base layer 16 and laser welding or the like is performed from the metal electrodes 14a and 14b. In addition, it is a joint portion formed between the base layer 16 and the metal electrodes 14a and 14b by melting a part of the metal electrodes 14a and 14b. In the example shown in FIG. 4, a configuration in which columnar bonding portions 20 are provided at three positions apart from each other between the base layer 16 and the metal electrodes 14a and 14b is schematically shown. The joint portion 20 having such a shape is formed by, for example, spot welding at three locations from the metal electrodes 14a and 14b side by laser welding with the metal electrodes 14a and 14b provided on the base layer 16. be able to. The size, shape, number, and the like of the joint portion 20 are not particularly limited.

The antioxidant layer 21a of the columnar honeycomb structure 11 according to the first embodiment of the present invention seals the gap 22 from the side surface of the metal electrodes 14a and 14b and extends over the base layer 16 as in the example of FIG. The layers 13a and 13b are continuously provided up to the surface. The antioxidant layer 21a is not limited to this, and as shown in FIG. 5, the antioxidant layer 21a may be provided from the side surface of the metal electrodes 14a and 14b to the middle of the side surface of the base layer 16 by sealing the gap 22. .. As described above, the antioxidant layer 21a may have any form as long as it is provided so as to seal the gap 22 between the base layer 16 and the metal electrodes 14a and 14b.

Further, when the metal electrodes 14a and 14b are provided on the base layer 16 and the base layer 16 and the metal electrodes 14a and 14b are connected by ultrasonic welding from the metal electrodes 14a and 14b side, the figure is shown in the figure. As shown in 6, a bonding portion 20a is formed over the entire surface between the base layer 16 and the metal electrodes 14a and 14b. Similarly in this case, the antioxidant layer 21a is provided so as to seal the gap 22 between the base layer 16 and the metal electrodes 14a and 14b.

The portion of the antioxidant layer 21a that seals the gap 22 between the base layer 16 and the metal electrodes 14a and 14b is particularly likely to be loaded due to thermal expansion of the metal electrodes 14a and 14b. Therefore, in order to increase the strength and suppress the occurrence of cracks, it is preferable to form the antioxidant layer 21a with a thickness of 10 μm or more. Further, the thickness of the antioxidant layer 21a is more preferably 10 to 100 μm.

The antioxidant layer 21a of the columnar honeycomb structure 11 according to the first embodiment of the present invention is formed from the outer surface of the electrode layers 13a and 13b so as to seal the gap 22 between the base layer 16 and the metal electrodes 14a and 14b. , 14b is provided over the outer surface. Here, the gap 22 between the base layer 16 and the metal electrodes 14a and 14b is a gap of, for example, about several tens of μm between the base layer 16 and the metal electrodes 14a and 14b. Generally, the joint portions 20 and 20a may be oxidized by being exposed to the exhaust gas diffused from the gap 22 between the base layer 16 and the metal electrodes 14a and 14b. On the other hand, in the columnar honeycomb structure 11 according to the first embodiment of the present invention, the antioxidant layer 21a is outside the electrode layers 13a and 13b so as to seal the gap 22 between the base layer 16 and the metal electrodes 14a and 14b. It is provided from the surface to the outer surface of the metal electrodes 14a and 14b. Therefore, the intrusion of the exhaust gas from the gap 22 can be suppressed, and as a result, the oxidation of the joint portions 20 and 20a can be satisfactorily suppressed.

As the material of the antioxidant layer 21a, ceramics, glass, or a composite material of ceramics and glass can be used. As the composite material, for example, a material containing 50% by volume or more of glass, more preferably 60% by volume or more, and even more preferably 70% by volume or more can be used. Examples of the ceramics constituting the antioxidant layer 21a include SiO ₂ system, Al ₂ O ₃ system, SiO _2- Al ₂ O ₃ system, SiO _2- ZrO ₂ system, and SiO _2- Al ₂ O _3- ZrO ₂ system. Ceramics such as. As the glass constituting the oxidation preventing layer 21a, for example, lead-free of B ₂ O ₃ -Bi ₂ O _{3 system, B 2 O 3 -ZnO-Bi} 2 O 3 system, B ₂ O ₃ -ZnO system, V ₂ O ₅ -P ₂ O ₅ series, SnO-P ₂ O ₅ series, SnO-ZnO-P ₂ O ₅ series, SiO _2- B ₂ O _3- Bi ₂ O ₃ series, SiO _2- Bi ₂ O ₃ Examples of glass include -Na ₂ O type and SiO _2- Al ₂ O _{3-MgO type.}

[Embodiment 2]
FIG. 7 shows a schematic cross-sectional view of the columnar honeycomb structure 11, the electrode layers 13a and 13b, the base layer 16, the joint portion 20, the metal electrodes 14a and 14b, and the antioxidant layer 21b according to the second embodiment of the present invention.

The antioxidant layer 21b of the columnar honeycomb structure 11 according to the second embodiment of the present invention is provided on the surface of the joint portion 20. By providing the antioxidant layer 21b on the surface of the joint portion 20 in this way, it is possible to suppress the exposure of the joint portion 20 to the exhaust gas. As a result, the oxidation of the joint portion 20 can be satisfactorily suppressed. Further, with such a configuration, since the antioxidant layer 21b is provided on the surface of the joint portion 20, the thermal stress on the antioxidant layer 21b due to thermal expansion of the metal electrodes 14a and 14b can be reduced. As a result, the occurrence of cracks can be suppressed more satisfactorily.

In the example shown in FIG. 7, the antioxidant layer 21b is provided so as to fill the space from the surface of the joint portion 20 to the ends of the metal electrodes 14a and 14b, but the present invention is not limited to this. For example, as shown in FIG. 8, the antioxidant layer 21b may be provided so as to fill the space from the surface of the joint portion 20 to the middle of the ends of the metal electrodes 14a and 14b. The antioxidant layer 21b can be formed by using the same material as the antioxidant layer 21a shown in the first embodiment of the present invention. Further, the bonding portion 20 may be a bonding portion 20a formed by ultrasonic welding as shown in FIG.

[Embodiment 3]
FIG. 9 shows a schematic cross-sectional view of the columnar honeycomb structure 11, the electrode layers 13a and 13b, the base layer 16, the joint portion 20, the metal electrodes 14a and 14b, and the antioxidant layer 21c according to the third embodiment of the present invention.

The antioxidant layer 21c of the columnar honeycomb structure 11 according to the third embodiment of the present invention is provided between the base layer 16 and the metal electrodes 14a and 14b apart from the joint portion 20. In this way, by providing the antioxidant layer 21c between the base layer 16 and the metal electrodes 14a and 14b at a distance from the joint portion 20, it is possible to suppress the exposure of the joint portion 20 to the exhaust gas. Can be done. As a result, the oxidation of the joint portion 20 can be satisfactorily suppressed. Further, in such a configuration, since the antioxidant layer 21c is provided between the base layer 16 and the metal electrodes 14a and 14b, thermal stress on the antioxidant layer 21c due to thermal expansion of the metal electrodes 14a and 14b or the like is performed. Can be reduced. As a result, the occurrence of cracks can be satisfactorily suppressed.

The antioxidant layer 21c can be formed by using the same material as the antioxidant layer 21a shown in the first embodiment of the present invention. Further, the bonding portion 20 may be a bonding portion 20a formed by ultrasonic welding as shown in FIG.

[Embodiment 4]
FIG. 10 shows a schematic cross-sectional view of the columnar honeycomb structure 11, the electrode layers 13a and 13b, the base layer 16, the joint portion 20b, the metal electrodes 14a and 14b, and the antioxidant layer 21d according to the fourth embodiment of the present invention.

The antioxidant layer 21d of the columnar honeycomb structure 11 according to the fourth embodiment of the present invention is filled between the base layer 16 and the metal electrodes 14a and 14b. By filling the antioxidant layer 21d between the base layer 16 and the metal electrodes 14a and 14b in this way, it is possible to prevent the joint portion 20b from being exposed to the exhaust gas. As a result, the oxidation of the joint portion 20b can be satisfactorily suppressed. Further, in such a configuration, since the antioxidant layer 21d is provided between the base layer 16 and the metal electrodes 14a and 14b, thermal stress on the antioxidant layer 21d due to thermal expansion of the metal electrodes 14a and 14b and the like is performed. Can be reduced. As a result, the occurrence of cracks can be satisfactorily suppressed.

FIG. 11 shows a schematic view showing a state in which the base layer 16 of the columnar honeycomb structure 11 and the metal electrodes 14a and 14b according to the fourth embodiment of the present invention are joined by laser welding or the like. As shown in the upper part of FIG. 11, first, a coat layer 23 made of an antioxidant layer forming material is provided on the base layer 16. Next, the metal electrodes 14a and 14b are arranged on the coat layer 23. Next, spot welding is performed from above the metal electrodes 14a and 14b by laser welding or the like. At this time, by applying energy by laser welding or the like, the metal electrodes 14a and 14b are melted to form a mixture with the antioxidant layer forming material of the lower coat layer 23. The mixture becomes the joint site 20b. The antioxidant layer forming material constituting the coat layer 23 can be formed by using the same material as the antioxidant layer 21a shown in the first embodiment of the present invention. Therefore, the joint portion 20b is a mixture of metal and an inorganic substance such as glass.

Further, by forming the joint portion 20b as shown in FIG. 11, even if there are minute pores between the joint portions 20b, the pores are filled with the antioxidant layer forming material, so that the acid resistance of the joint portion 20b is formed. It is possible to further improve the chemistry.

[Embodiment 5]
FIG. 12 shows a schematic cross-sectional view of the columnar honeycomb structure 11, the electrode layers 13a and 13b, the fixed layer 24, the metal electrodes 14a and 14b and the antioxidant layer 21e according to the fifth embodiment of the present invention.

In the electroheating carrier according to the fifth embodiment of the present invention, the electrode layers 13a and 13b are arranged on the surface of the outer peripheral wall of the columnar honeycomb structure 11 shown in the first embodiment, and the metal electrodes 14a are arranged on the electrode layers 13a and 13b. , 14b are provided. Further, the fixing layer 24 is provided so as to cover the metal electrodes 14a and 14b, and the antioxidant layer 21e is provided so as to cover the fixing layer 24. The fixing layer 24 fixes the metal electrodes 14a and 14b to the electrode layers 13a and 13b.

In this way, by providing the fixed layer 24 so as to cover the metal electrodes 14a and 14b and further providing the antioxidant layer 21e so as to cover the fixed layer 24, the fixed layer 24 which is a joint portion becomes exhaust gas. Exposure can be suppressed. As a result, the oxidation of the fixed layer 24 can be satisfactorily suppressed. Further, in such a configuration, since the antioxidant layer 21e is provided on the fixed layer 24 covering the metal electrodes 14a and 14b, thermal stress on the antioxidant layer 21e due to thermal expansion of the metal electrodes 14a and 14b is applied. Can be reduced. As a result, the occurrence of cracks can be satisfactorily suppressed.

The fixed layer 24 in the fifth embodiment can be formed by thermal spraying, for example. After the metal electrodes 14a and 14b are provided on the electrode layers 13a and 13b, the fixed layer 24 is provided by spraying a material composed of a mixed spraying material of NiCrAlY and mullite so as to cover the metal electrodes 14a and 14b. Can be formed. Further, the antioxidant layer 21e can be formed so as to cover the fixed layer 24 by using the same material as the antioxidant layer 21a shown in the first embodiment of the present invention.

[Embodiment 6]
13 (a), 13 (b), 13 (c) and 13 (d) show the columnar honeycomb structure 11, electrode layers 13a and 13b of the electrically heated carrier according to the sixth embodiment of the present invention. 2 shows a schematic cross-sectional view of the base layer or electrode layer 17, the base layer 16, the joint portion 20d, the metal electrodes 14a and 14b, and the antioxidant layers 21f, 21g, 21h and 21i.

In the electroheating carrier according to the fifth embodiment of the present invention, the electrode layers 13a and 13b are arranged on the surface of the outer peripheral wall of the columnar honeycomb structure 11 shown in the first embodiment, and the second electrode layers 13a and 13b are covered with the second electrode layers 13a and 13b. An underlayer or an electrode layer 17 and an underlayer 16 are provided. The base layer 16 is joined to the metal electrodes 14a and 14b at the joining portion 20d by brazing the metal electrodes 14a and 14b.

In the embodiment shown in FIG. 13A, the antioxidant layer 21f is continuously provided from the side surface of the metal electrodes 14a and 14b to the outer surface of the electrode layers 13a and 13b, and the base layer 16 and the metal electrode 14a are provided. , 14b is configured to seal the gap. In the embodiment shown in FIG. 13B, the antioxidant layer 21g is continuously provided from the bottom surface of the metal electrodes 14a and 14b to the outer surface of the electrode layers 13a and 13b, and the base layer 16 and the metal electrode 14a are provided. , 14b is configured to seal the gap. In the embodiment shown in FIG. 13 (c), a gap having no joint portion 20d is provided between the metal electrodes 14a and 14b and the base layer 16, and the gap is oxidized so as to be in contact with the joint portion 20d. The prevention layer 21h is provided. In the embodiment shown in FIG. 13 (d), a gap having no joint portion 20d is provided between the metal electrodes 14a and 14b and the base layer 16, and the gap is oxidized at a distance from the joint portion 20d. The prevention layer 21i is provided.

According to the embodiments shown in FIGS. 13 (a), 13 (b), 13 (c) and 13 (d), the bonding portion 20d is formed by providing the antioxidant layers 21f, 21g, 21h and 21i. Exposure to exhaust gas can be suppressed. As a result, the oxidation of the joint portion 20d can be satisfactorily suppressed.

By supporting the catalyst on the electrically heated carrier 10, the electrically heated carrier 10 can be used as a catalyst. For example, a fluid such as automobile exhaust gas can flow through the flow paths of the plurality of cells 18. Examples of the catalyst include noble metal-based catalysts and catalysts other than these. As the noble metal catalyst, a noble metal such as platinum (Pt), palladium (Pd), or rhodium (Rh) is supported on the surface of the alumina pores, and a three-way catalyst containing a co-catalyst such as ceria or zirconia, an oxidation catalyst, or an alkali. _{An example is a NO x} storage reduction catalyst (LNT catalyst) containing earth metal and platinum as storage components of _{nitrogen oxide (NO x).} Examples of catalysts that do not use noble metals include NO _x selective reduction catalysts (SCR catalysts) containing copper-substituted or iron-substituted zeolites. Further, two or more kinds of catalysts selected from the group consisting of these catalysts may be used. The method of supporting the catalyst is also not particularly limited, and can be carried out according to the conventional method of supporting the catalyst on the honeycomb structure.

(2. Method for manufacturing electrically heated carrier)
Next, a method for producing the electrically heated carrier 10 according to the present invention will be exemplified. The method for producing the electroheating carrier 10 of the present invention is, in one embodiment, a step A1 for obtaining an unfired honeycomb structure portion with an electrode layer forming paste and a columnar honeycomb structure by firing the unfired honeycomb structure portion with an electrode layer forming paste. The step A2 for obtaining the body and the step A3 for welding the metal electrode to the columnar honeycomb structure are included.

Step A1 is a step of producing a honeycomb molded body which is a precursor of the honeycomb structure portion, applying an electrode layer forming paste to the side surface of the honeycomb molded portion, and obtaining an unfired honeycomb structure portion with the electrode layer forming paste. The honeycomb molded body can be produced according to the method for producing a honeycomb molded body in the known method for producing a honeycomb structure portion. For example, first, a metal silicon powder (metal silicon), a binder, a surfactant, a pore-forming material, water, or the like is added to silicon carbide powder (silicon carbide) to prepare a molding raw material. It is preferable that the mass of the metallic silicon is 10 to 40% by mass with respect to the total of the mass of the silicon carbide powder and the mass of the metallic silicon. The average particle size of the silicon carbide particles in the silicon carbide powder is preferably 3 to 50 μm, more preferably 3 to 40 μm. The average particle size of metallic silicon (metallic silicon powder) is preferably 2 to 35 μm. The average particle size of silicon carbide particles and metallic silicon (metal silicon particles) refers to the arithmetic mean diameter based on the volume when the frequency distribution of particle size is measured by the laser diffraction method. The silicon carbide particles are fine particles of silicon carbide constituting the silicon carbide powder, and the metallic silicon particles are fine particles of metallic silicon constituting the metallic silicon powder. This is a blending of molding raw materials when the material of the honeycomb structure is silicon-silicon carbide-based composite material, and when the material of the honeycomb structure is silicon carbide, metallic silicon is not added.

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

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

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

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

Next, after kneading the obtained molding raw materials to form a clay, the clay is extruded to produce a honeycomb molded body. In extrusion molding, a mouthpiece having a desired overall shape, cell shape, partition wall thickness, cell density and the like can be used. Next, it is preferable to dry the obtained honeycomb molded product. When the length in the central axis direction of the honeycomb molded body is not the desired length, both bottom portions of the honeycomb molded body can be cut to obtain the desired length. The dried honeycomb molded body is called a honeycomb dried body.

Next, the electrode layer forming paste for forming the electrode layer is prepared. The electrode layer forming paste can be formed by appropriately adding various additives to the raw material powder (metal powder, ceramic powder, etc.) blended according to the required characteristics of the electrode layer and kneading. When the electrode layer has a laminated structure, the average particle size of the metal powder in the paste for the second electrode layer is made larger than the average particle size of the metal powder in the paste for the first electrode layer. , The bonding strength between the metal terminal and the electrode layer tends to improve. The average particle size of the metal powder refers to the arithmetic mean diameter based on the volume when the frequency distribution of the particle size is measured by the laser diffraction method.

Next, the obtained electrode layer forming paste is applied to the side surface of the honeycomb molded body (typically, the honeycomb dried body) to obtain an unfired honeycomb structure portion with the electrode layer forming paste. The method of preparing the electrode layer forming paste and the method of applying the electrode layer forming paste to the honeycomb molded body can be performed according to a known method for producing a honeycomb structure, but the electrode layer is compared with the honeycomb structure portion. In order to obtain a low electrical resistance, the metal content ratio can be increased or the particle size of the metal particles can be reduced as compared with the honeycomb structure portion.

As an example of changing the manufacturing method of the columnar honeycomb structure, in step A1, the honeycomb molded body may be fired once before applying the electrode layer forming paste. That is, in this modified example, the honeycomb molded body is fired to produce a honeycomb fired body, and the 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 is fired to obtain a columnar honeycomb structure. Before firing, the unfired honeycomb structure with the electrode layer forming paste may be dried. Further, before firing, degreasing may be performed in order to remove the binder and the like. As the firing conditions, it is preferable to heat at 1400 to 1500 ° C. for 1 to 20 hours in an inert atmosphere such as nitrogen or argon. Further, after firing, it is preferable to carry out an oxidation treatment at 1200 to 1350 ° C. for 1 to 10 hours in order to improve durability. The method of degreasing and firing is not particularly limited, and firing can be performed using an electric furnace, a gas furnace, or the like.

In step A3, a paste of a conductive material for forming a base layer is applied to the surface of the electrode layer on the columnar honeycomb structure. The paste of the conductive material thus prepared is applied by a curved surface printing machine or the like so as to have a predetermined arrangement, dried, and then fired to form an underlayer. As a paste of a conductive material, first of all, a metal powder (NiCr-based material, a metal powder such as stainless steel) and an oxide powder (an oxide powder such as Cd, alumina, mullite) are mixed in a volume ratio of 20 to 85. A ceramic raw material is prepared by mixing 15 to 80% by volume of oxide powder. Next, a base layer forming paste can be prepared by adding 1% by mass of a binder, 1% by mass of a surfactant, and 20 to 40% by mass of water to the ceramic raw material. Further, the base layer may be formed by spraying a conductive material so as to have a predetermined arrangement and shape.

Next, the metal electrode is fixed on the base layer by welding. The welding method will be described in detail below. First, a comb-shaped electrode is arranged on the honeycomb structure on which the base layer is formed, and laser welding or ultrasonic welding is performed on the portion where each comb-shaped electrode and the base layer overlap. The laser spot diameter when performing laser welding includes a range of 0.5 to 3.0 mm. The vibration frequency when ultrasonic welding is performed is 20 kHz to 40 kHz, and the pressing force is in the range of 10 N to 30 N.

At this time, the joint portion 20 as shown in FIG. 4 can be formed by performing a plurality of spot welds by laser welding. Further, by performing ultrasonic welding, a bonding portion 20a as shown in FIG. 6 can be formed.

Next, the antioxidant layer 21a as shown in FIGS. 4 to 6 is provided by providing an antioxidant layer from the outer surface of the base layer to the outer surface of the metal electrode so as to seal the gap between the base layer and the metal electrode. Can be formed. At this time, after joining the base layer and the metal electrode, an antioxidant is sprayed by spraying or the like, and the antioxidant layer 21a is formed by firing at 800 to 1100 ° C. for 4 to 8 hours, preferably in a vacuum atmosphere. be able to.

Further, by performing a plurality of spot welds by laser welding, it is possible to form the antioxidant layers 21b and 21c as shown in FIGS. 7 to 9 after forming the joint portion 20 as shown in FIGS. 7 to 9. .. At this time, an antioxidant is applied to a portion of the base layer other than the joint portion, and the metal electrodes are bonded by a method such as laser welding, and then preferably in a vacuum atmosphere, 800 to 1100 ° C., 4 to 8 Antioxidant layers 21b and 21c can be formed by firing for a long time.

Further, as shown in FIG. 11, a coat layer made of an antioxidant layer forming material is provided between the base layer and the metal electrode, and laser welding is performed from the metal electrode side, as shown in FIG. Such an antioxidant layer 21d can be formed.

(3. Exhaust gas purification device)
The electrically heated carrier according to the embodiment of the present invention described above can be used in an exhaust gas purification device. The exhaust gas purifying device has an electrically heated carrier and a can body that holds the electrically heated carrier. In the exhaust gas purification device, the electrically heated carrier is installed in the middle of the exhaust gas flow path for flowing the exhaust gas from the engine. As the can body, a metal tubular member or the like accommodating an electrically heated carrier can be used.

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

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

(2. Preparation of dried honeycomb)
The obtained columnar clay was molded using an extrusion molding machine having a grid-like base structure to obtain a columnar honeycomb molded body in which each cell shape is square in a cross section perpendicular to the cell flow path direction. It was. This honeycomb molded body was dried by high frequency dielectric heating and then dried at 120 ° C. for 2 hours using a hot air dryer, and both bottom surfaces were cut by a predetermined amount to prepare a honeycomb dried body.

(3. Preparation of electrode layer forming paste)
Metallic silicon (Si) powder, silicon carbide (SiC) powder, methyl cellulose, glycerin, and water were mixed with a rotating and revolving stirrer to prepare an electrode layer forming paste. The Si powder and the SiC powder were blended so that the volume ratio was Si powder: SiC powder = 40:60. Further, when the total of Si powder and SiC powder was 100 parts by mass, methyl cellulose was 0.5 parts by mass, glycerin was 10 parts by mass, and water was 38 parts by mass. The average particle size of the metallic silicon powder was 6 μm. The average particle size of the silicon carbide powder was 35 μm. These average particle diameters refer to the arithmetic mean diameters based on the volume when the frequency distribution of particle size is measured by the laser diffraction method.

(4. Application and firing of electrode layer forming paste)
Next, this electrode layer forming paste is applied to the honeycomb dried body with an appropriate area and film thickness by a curved surface printing machine, further dried at 120 ° C. for 30 minutes with a hot air dryer, and then Ar atmosphere together with the honeycomb dried body. Was fired at 1400 ° C. for 3 hours to obtain a columnar honeycomb structure.

(5. Preparation of base layer forming paste)
Metal powder (NiCr-based material, metal powder such as stainless steel) and oxide powder (oxide powder such as Cd, alumina, mulite) are mixed in a volume ratio of 20 to 85%, and oxide powder is mixed in a volume ratio of 15 to 80%. Then, a ceramic raw material was prepared. A paste raw material was prepared by adding 1% by mass of a binder, 1% by mass of a surfactant, and 20 to 40% by mass of water to the ceramic raw material. The average particle size of the metal powder measured by the laser diffraction method was 10 μm, and the average particle size of the oxide powder was 5 μm.

(6. Application and firing of base layer forming paste)
The above base layer forming paste was applied to the electrode layer of the columnar honeycomb structure by a curved surface printing machine. Subsequently, it was dried at 120 ° C. for 30 minutes in a hot air dryer, and then fired at 1100 ° C. for 1 hour in an Ar atmosphere.

The bottom surface of the honeycomb structure was circular with a diameter of 100 mm, and the height (length in the flow path direction of the cell) was 100 mm. The cell density was 93 cells / cm ² , the thickness of the partition was 101.6 μm, the porosity of the partition was 45%, and the average pore diameter of the partition was 8.6 μm. The thickness of the electrode layer was 0.3 mm, and the thickness of the base layer was 0.2 mm. When the electrical resistivity at 400 ° C. was measured by the four-terminal method using a test piece made of the same material as the honeycomb structure, the electrode layer and the base layer, it was 5 Ωcm, 0.01 Ω cm and 0.001 Ω cm, respectively.

(7. Fixing electrodes)
Comb-shaped electrodes are arranged on the honeycomb structure on which the base layer is formed, and the lasers have a diameter of φ0.5 mm in Examples 1 to 6 and Comparative Example 1 for the portion where each comb-shaped electrode and the base layer overlap. Welded. Further, in Examples 7 to 11 and Comparative Example 2, ultrasonic welding was performed. Further, in Examples 12 to 16 and Comparative Example 3, joining was performed by brazing.
Next, for Examples 1 to 16, an antioxidant layer was formed in the following form.
The antioxidant layers of Examples 1 to 3 are provided as shown in FIG. 4 (Embodiment 1), and the antioxidant layers of Examples 7 to 9 are provided as shown in FIG. 6 (Embodiment 1). The antioxidant layers of Examples 12 to 14 were provided as shown in FIG. 13 (a).
The antioxidant layers of Examples 4 and 10 were provided as shown in FIG. 7 (Embodiment 2), and the antioxidant layers of Example 15 were provided as shown in FIG. 13 (b).
The antioxidant layers of Examples 5 and 11 were provided as shown in FIG. 9 (Embodiment 3), and the antioxidant layers of Example 16 were provided as shown in FIG. 13 (d).
The antioxidant layer of Example 6 was provided as shown in FIG. 10 (Embodiment 4).
As the material of the antioxidant layer used in Examples 1 to 16, SiO _2- Al ₂ O _3- MgO was used. The thickness of each antioxidant layer is shown in Table 1 below.

(8. Oxidation resistance evaluation test)
An oxidation resistance evaluation test was performed on a honeycomb structure in which a pair of metal electrodes were fixed by the above method. In the oxidation resistance evaluation test, a disk-shaped base layer having a diameter of 5 mm and a thickness of 0.3 mm was provided in a heating furnace with a sample arranged in 5 × 4 rows with the distance between the centers of adjacent base layers set to 5 mm. Heating was carried out at 1000 ° C. for 50 hours in an air atmosphere. The rate of increase in resistance with respect to the initial resistance value of the sample was used as an index of the oxidation state, and it was judged that the smaller the rate of increase in resistance, the greater the effect of suppressing oxidation of the present invention. As the resistance value, the resistance between the two points of the base layer was measured at a total of 12 points by the 4-wire resistance measurement method using the Kelvin probe, and the average value of these was calculated. The conduction path of the sample was (1) the surface of the base layer, (2) the base layer, (3) the electrode layer, (4) the base layer, and (5) the surface of the base layer. The evaluation results are shown in Table 1.

(9. Consideration)
Regardless of the bonding method, in all of Examples 1 to 16, the effect of suppressing oxidation of the bonding portion connecting the base layer and the metal electrode could be obtained. Among them, the magnitude of the oxidation-suppressing effect differs depending on the form of the antioxidant layer, and further, among the forms of the antioxidant layer shown in the first embodiment (Examples 1 to 3, 7 to 9, 12 to 14), the oxidation-suppressing effect The results were different from each other.
In the form of the antioxidant layer shown in the first embodiment (Examples 1 to 3, 7 to 9, 12 to 14), Examples 3 and 14 having a thickness of the antioxidant layer of 200 μm have the smallest antioxidant effect and are oxidized. It is considered that the reason is that the antioxidant layer is cracked due to the difference in thermal expansion between the base layer and the metal electrode due to the thick thickness of the prevention layer. For the same reason, when the crack state was confirmed, the cracks were smaller in Examples 1 and 12 in which the thickness of the antioxidant layer was 10 μm than in Examples 2 and 13 in which the thickness of the antioxidant layer was 100 μm. Therefore, it is considered that the difference in the antioxidant effect depending on the thickness of the antioxidant layer is due to cracks.
Next, when the forms of the antioxidant layer shown in Examples 2 to 4 are compared in Examples 4 to 6, the antioxidant effect is as follows: The form of the antioxidant layer shown in Example 3 of Example 5 <Example 4 The result was that the form of the antioxidant layer shown in the second embodiment <the form of the antioxidant layer shown in the fourth embodiment of the sixth embodiment. As described above, the second embodiment of the fourth embodiment is provided with an antioxidant layer as shown in FIG. 7, and the third embodiment of the fifth embodiment is provided with an antioxidant layer as shown in FIG. Therefore, it is considered that the amount of the antioxidant film filled between the metal electrode and the base layer affected the oxygen blocking ability.
Further, as described above, in the fourth embodiment of the sixth embodiment, the antioxidant layer is provided as shown in FIG. 10, and the antioxidant layer completely covers the periphery of the joint portion, so that cracks or the like may occur. Even when oxygen invades from a part of the antioxidant layer, the oxidation-suppressing effect can be maintained, so that the oxidation-suppressing effect is considered to be the largest.

10 Electric heating type carrier 11 Columnar honeycomb structure 12 Outer wall 13a, 13b Electrode layer 14a, 14b Metal electrode 15 Electrode part 16 Base layer 17 Second base layer or electrode layer 18 Cell 19 Partitions 20, 20a, 20b, 20c, 20d Joint site 21, 21a, 21b, 21c, 21d, 21e, 21f, 21g, 21h, 21i Antioxidant layer 22 Gap 23 Coat layer 24 Fixed layer

Claims (9)

1. A ceramic columnar honeycomb structure having an outer peripheral wall and a partition wall that is disposed inside the outer peripheral wall and partitions a plurality of cells that form a flow path from one end face to the other end face. ,
   An electrode layer arranged on the surface of the outer peripheral wall of the columnar honeycomb structure and
   A conductive base layer provided on the electrode layer and
   A metal electrode connected to the base layer by a joint site and
   An antioxidant layer for protecting the joint site from exhaust gas,
   An electroheated carrier equipped with.
2. The electroheating type according to claim 1, wherein the antioxidant layer is provided from the outer surface of the electrode layer to the outer surface of the metal electrode so as to seal the gap between the base layer and the metal electrode. Carrier.
3. The electrically heated carrier according to claim 1, wherein the antioxidant layer is provided between the base layer and the metal electrode.
4. The electroheated carrier according to claim 3, wherein the antioxidant layer is provided on the surface of the joint portion.
5. The electroheated carrier according to claim 3, wherein the antioxidant layer is provided between the base layer and the metal electrode so as to be separated from the joint portion.
6. The electroheated carrier according to claim 3, wherein the antioxidant layer is filled between the base layer and the metal electrode.
7. A ceramic columnar honeycomb structure having an outer peripheral wall and a partition wall that is disposed inside the outer peripheral wall and partitions a plurality of cells that form a flow path from one end face to the other end face. ,
   An electrode layer arranged on the surface of the outer peripheral wall of the columnar honeycomb structure and
   A metal electrode provided on the electrode layer and
   A fixed layer provided so as to cover the metal electrode and fixing the metal electrode to the electrode layer,
   An antioxidant layer provided so as to cover the fixed layer and
   An electroheated carrier equipped with.
8. The electrode layer disposed on the surface of the outer peripheral wall of the columnar honeycomb structure is disposed so as to face the surface of the outer peripheral wall of the columnar honeycomb structure with the central axis of the columnar honeycomb structure interposed therebetween. The electrically heated carrier according to any one of claims 1 to 7, which is a pair of electrode layers.
9. The electrically heated carrier according to any one of claims 1 to 8.
   A metal tubular member for holding the electrically heated carrier, and
   Exhaust gas purification device with.

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