WO2021176757A1 - Electrically heated carrier and exhaust gas purification device - Google Patents

Electrically heated carrier and exhaust gas purification device Download PDF

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Publication number
WO2021176757A1
WO2021176757A1 PCT/JP2020/037481 JP2020037481W WO2021176757A1 WO 2021176757 A1 WO2021176757 A1 WO 2021176757A1 JP 2020037481 W JP2020037481 W JP 2020037481W WO 2021176757 A1 WO2021176757 A1 WO 2021176757A1
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Prior art keywords
honeycomb structure
electrode
cross
electrode terminals
electrically heated
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PCT/JP2020/037481
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French (fr)
Japanese (ja)
Inventor
尚哉 高瀬
博紀 高橋
幸春 森田
達士 市川
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日本碍子株式会社
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Priority to JP2022504964A priority Critical patent/JP7261934B2/en
Publication of WO2021176757A1 publication Critical patent/WO2021176757A1/en

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters

Definitions

  • the present invention relates to an electrically heated carrier and an exhaust gas purifying device.
  • Patent Document 1 As the ceramic carrier used for the electric heating catalyst (EHC), in Patent Document 1 below, a carrier having PTC characteristics is used, and more specifically, a matrix composed of a borosilicate containing an alkaline atom is used. Is disclosed.
  • the PTC characteristic is a characteristic in which the electrical resistance increases as the temperature rises.
  • the EHC is provided with an electrode for applying a voltage to the ceramic carrier.
  • the electrode includes an electrode layer provided on the outer peripheral wall of the ceramic carrier and a columnar electrode terminal provided so as to stand up from the electrode layer.
  • Patent Document 2 discloses that a metal body is bonded to an electrode terminal made of a columnar ceramic body.
  • the electrode terminals are columnar, more specifically, when the cross-sectional shape of the electrode terminals is circular, the surface area of the electrode terminals is small and the current density is high. It was found that there is a problem that the desired current cannot flow when the current is energized and heated. If the diameter of the electrode terminal is increased, the connection area of the connecting portion can be increased, but the larger metal electrode deteriorates the mountability of the electrically heated carrier on the vehicle.
  • the present invention has been made to solve the above problems, and one of the purposes thereof is an electrically heated carrier having an electrode terminal capable of passing a desired current during energization heating and exhaust gas purification. To provide the device.
  • One aspect of the electroheated carrier according to the present invention is a partition wall that is disposed inside the outer peripheral wall and partitions a plurality of cells that penetrate from one end face to the other end face to form a flow path.
  • a columnar honeycomb structure having a The diameter of the portion is 30 mm or less, and the circularity of at least a part of the cross section of the connecting portion on the plane orthogonal to the length direction of the electrode terminal is 0.95 or less.
  • One aspect of the exhaust gas purification device comprises the above-mentioned electrically heated carrier, a metal electrode connected to an electrode terminal of the electrically heated carrier, and a metal can body holding the electrically heated carrier. Be prepared.
  • an electrically heated carrier having an electrode terminal capable of passing a desired current during energization heating and an exhaust gas purifying device.
  • FIG. 2 It is a perspective view which shows the electric heating type carrier in embodiment of this invention. It is sectional drawing which is orthogonal to the stretching direction of the cell of the electroheating type carrier of FIG. It is an enlarged cross-sectional view which shows the electrode terminal of FIG. 2 in an enlarged manner. It is explanatory drawing which shows the 1st aspect of the connection part of FIG. It is explanatory drawing which shows the 2nd aspect of the connection part of FIG. It is explanatory drawing which shows the 3rd aspect of the connection part of FIG. It is explanatory drawing which shows the exhaust gas purification apparatus which concerns on embodiment of this invention.
  • FIG. 1 is a perspective view showing an electrically heated carrier 1 according to an embodiment of the present invention
  • FIG. 2 is a cross-sectional view orthogonal to the extending direction of the cell of the electrically heated carrier 1 of FIG. 1
  • FIG. 3 is a view. It is an enlarged cross-sectional view which shows the electrode terminal of 2 in an enlarged manner.
  • the electrically heated carrier 1 of the present embodiment has a honeycomb structure 2 and a pair of electrodes 3a and 3b.
  • the honeycomb structure 2 is a columnar structure, and partitions the outer peripheral wall 20 and a plurality of cells 21a arranged inside the outer peripheral wall 20 and penetrating from one end face to the other end face to form a flow path. It has a partition wall 21 to be formed.
  • the honeycomb structure 2 is made of ceramics, and borosilicate containing an alkaline atom can be used as the ceramics.
  • the alkaline atom include Na, Mg, K, Ca, Li, Be, Sr, Cs, and Ba.
  • the borosilicate may contain one or more kinds of alkali metal atoms, may contain one or more kinds of alkaline earth metal atoms, or may contain a combination thereof.
  • the alkaline atom is more preferably Na, Mg, K, or Ca.
  • the honeycomb structure 2 may have a matrix composed of the above-mentioned borosilicate containing an alkaline atom and a domain composed of a conductive filler.
  • the matrix is a portion that serves as a base material for the honeycomb structure 2.
  • the matrix may be amorphous or crystalline. According to such a configuration, the region that controls the electric resistance when the EHC is energized and heated becomes the matrix that is the base material.
  • the matrix has a smaller temperature dependence of electrical resistivity than the SiC material, and the electrical resistivity exhibits PTC characteristics (characteristics in which the electrical resistance increases as the temperature rises).
  • the total content of alkaline atoms may be 10% by mass or less. More preferably, it may be 5% by mass or less, or 2% by mass or less. According to such a configuration, it becomes easy to reduce the electric resistance of the matrix, and the electrical resistivity of the matrix shows more PTC characteristics. Further, it is possible to suppress the formation of an insulating glass film due to the segregation of alkaline atoms on the surface side of the honeycomb structure 2 during firing in an oxidizing atmosphere.
  • the lower limit is not particularly limited, but the total content of alkaline atoms may be 0.01% by mass or more, or 0.2% by mass or more. Alkaline atoms may be intentionally added to suppress the oxidation of the conductive filler.
  • honeycomb structure 2 since it is an element that is relatively easily mixed from the raw material of the honeycomb structure 2, it complicates the manufacturing process to completely remove it, and therefore, it is usually included within the above range.
  • the honeycomb structure 2 it is possible to reduce alkaline atoms by using boric acid instead of using borosilicate glass containing alkaline atoms as a raw material.
  • total content of alkaline atoms indicates the mass% of one alkaline atom when the borosilicate contains one alkaline atom.
  • the total content (mass%) with the content (mass%) of each of the plurality of alkaline atoms is shown.
  • the content of each of the B (boron) atom, Si (silicon) atom, and O (oxygen) atom constituting the borosilicate is preferably in the following range, for example.
  • the content of B atom in borosilicate is 0.1% by mass or more and 5% by mass or less.
  • the content of Si atom in borosilicate is 5% by mass or more and 40% by mass or less.
  • the content of O atom in borosilicate is 40% by mass or more and 85% by mass or less. According to such a configuration, it is possible to easily show the PTC characteristics in the honeycomb structure 2.
  • borosilicate aluminoborosilicate or the like can be used. According to such a configuration, it is possible to obtain a honeycomb structure 2 in which the temperature dependence of the electrical resistivity is small, the electrical resistivity exhibits PTC characteristics, or the temperature dependence of the electrical resistivity is suppressed.
  • the content of Al atom in the aluminum borosilicate may be, for example, 0.5% by mass or more and 10% by mass or less.
  • Examples of the atoms contained in the borosilicate constituting the matrix in addition to the atoms in the above-mentioned borosilicate include Fe and C.
  • the contents of alkaline atoms, Si, O, and Al can be measured using an electron probe microanalyzer (EPMA) analyzer.
  • the B content can be measured using an inductively coupled plasma (ICP) analyzer. According to the ICP analysis, the B content in the entire honeycomb structure 2 is measured, so that the obtained measurement result is converted into the B content in the borosilicate.
  • ICP inductively coupled plasma
  • the electrical resistivity of the entire honeycomb structure 2 is determined by adding the electrical resistivity of the matrix and the electrical resistivity of the conductive filler. .. Therefore, the electrical resistivity of the honeycomb structure 2 can be controlled by adjusting the conductivity of the conductive filler and the content of the conductive filler.
  • the electrical resistivity of the conductive filler may exhibit either PTC characteristics or NTC characteristics (characteristics in which the electrical resistance decreases as the temperature rises), and the electrical resistivity may not be temperature-dependent.
  • the conductive filler may contain Si atoms. According to such a configuration, it is possible to improve the shape stability of the honeycomb structure 2.
  • Examples of the conductive filler containing Si atoms include Si particles, Fe—Si particles, SiW particles, SiC particles, Si—Mo particles, Si—Ti particles and the like. These can be used alone or in combination of two or more.
  • the Si particles may be Si particles doped with a dopant.
  • Dopants include boron (B), aluminum (Al), gallium (Ga), indium (In), nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi) and the like. Can be mentioned.
  • the dopant concentration may be contained as a dopant in the silicon particles in the range of 1 ⁇ 10 16 to 5 ⁇ 10 20 pieces / cm 3.
  • the volume resistivity of the honeycomb structure 2 decreases as the concentration of the dopant in the Si particles increases, and the volume resistivity of the honeycomb structure 2 increases as the concentration of the dopant in the Si particles decreases.
  • the amount of dopant in the silicon particles contained in the honeycomb structure 2 is preferably 5 ⁇ 10 16 to 5 ⁇ 10 20 pieces / cm 3 , and 5 ⁇ 10 17 to 5 ⁇ 10 20 pieces / cm 3. More preferred.
  • the dopant in the Si particles contained in the honeycomb structure 2 is a homologous element, it may contain a plurality of types of elements because it can exhibit conductivity without being affected by counterdoping. Further, it is more preferable that the dopant is one or two selected from the group consisting of B and Al. It is also preferable that it is one or two selected from the group consisting of N and P.
  • the honeycomb structure 2 may have a configuration in which the matrix and the conductive filler are contained in a total of 50 vol% or more.
  • the rate of increase in electrical resistance of the honeycomb structure 2 is preferably 1 ⁇ 10 -8 to 5 ⁇ 10 -4 ⁇ ⁇ m / K.
  • the rate of increase in electrical resistance of the honeycomb structure 2 is 1 ⁇ 10 -8 ⁇ ⁇ m / K or more, it becomes easy to suppress the temperature distribution during energization and heating.
  • the rate of increase in electrical resistance of the honeycomb structure 2 is 5 ⁇ 10 -4 ⁇ ⁇ m / K or less, the change in resistance during energization and heating can be reduced.
  • the rate of increase in electrical resistance of the honeycomb structure 2 is more preferably 5 ⁇ 10 -8 to 1 ⁇ 10 -4 ⁇ ⁇ m / K, and 1 ⁇ 10 -7 to 1 ⁇ 10 -4 ⁇ ⁇ m / K. It is even more preferable to have it.
  • the electrical resistivity increase rate of the honeycomb structure 2 first, the electrical resistivity at two points at 50 ° C. and 400 ° C. is measured by the four-terminal method, and the electrical resistivity at 50 ° C. is subtracted from the electrical resistivity at 400 ° C. It can be obtained by dividing the value derived in this manner by the temperature difference of 350 ° C. between 400 ° C. and 50 ° C. to calculate the rate of increase in electrical resistance.
  • the outer shape of the honeycomb structure 2 is not particularly limited as long as it is columnar. It can have a columnar shape (octagonal shape, etc.).
  • the honeycomb structure 2 has conductivity.
  • the honeycomb structure 2 is not particularly limited in electrical resistivity as long as it can be energized and generate heat by Joule heat , but it is preferably 1 ⁇ 10 -5 to 2 ⁇ ⁇ m, and 5 ⁇ 10 -5 to It is more preferably 1 ⁇ ⁇ m, and even more preferably 1 ⁇ 10 -4 to 0.5 ⁇ ⁇ m.
  • the electrical resistivity of the honeycomb structure 2 is a value measured at 25 ° C. by the four-terminal method.
  • the shape of the cell in the cross section perpendicular to the extending direction of the cell 21a is preferably a quadrangle, a hexagon, an octagon, or a combination thereof. Among these, a quadrangle and a hexagon are preferable.
  • a quadrangle is particularly preferable from the viewpoint of easily achieving both structural strength and heating uniformity.
  • the thickness of the partition wall 21 forming the cell 21a is preferably 0.1 to 0.3 mm, more preferably 0.1 to 0.2 mm.
  • the thickness of the partition wall 21 is 0.1 mm or more, it is possible to suppress a decrease in the strength of the honeycomb structure 2.
  • the thickness of the partition wall 21 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 2 is used as a catalyst carrier and a catalyst is supported.
  • the thickness of the partition wall 21 is defined as the length of the portion of the line segment connecting the centers of gravity of the adjacent cells 21a that passes through the partition wall 21 in the cross section perpendicular to the extending direction of the cell 21a.
  • the honeycomb structure 2 preferably has a cell density of 40 to 150 cells / cm 2 , and more preferably 60 to 100 cells / cm 2 in a cross section perpendicular to the flow path direction of the cells 21a.
  • the cell density is 40 cells / cm 2 or more, a sufficient catalyst-supporting area is secured.
  • the cell density is 150 cells / cm 2 or less, when the honeycomb structure 2 is used as a catalyst carrier and the catalyst is supported, the pressure loss when the exhaust gas is flowed is suppressed 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 honeycomb structure 2 excluding the outer peripheral wall 20 portion.
  • the thickness of the outer peripheral wall 20 is preferably 0.1 mm or more, more preferably 0.15 mm or more, and even more preferably 0.2 mm or more.
  • the thickness of the outer peripheral wall 20 is preferably 1 mm or less, and more. It is preferably 0.7 mm or less, and even more preferably 0.5 mm or less.
  • the thickness of the outer peripheral wall 20 is the normal direction with respect to the tangent line of the outer peripheral wall 20 at the measurement location when the portion of the outer peripheral wall 20 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 21 preferably has a porosity of 30% or less. When the porosity of the partition wall 21 is 30% or less, the risk of damage during canning is reduced.
  • the porosity of the partition wall 21 is more preferably 20% or less, and even more preferably 10% or less.
  • the porosity is a value calculated by binarizing the pores and the non-pores (specifically, the ceramic material portion) in the SEM observation image of the partition wall 13.
  • the partition wall 21 has a porosity of 0.1% or more in order to suppress peeling between the partition wall 21 and the catalyst. It is preferably 1% or more, more preferably 2% or more, and even more preferably 5% or more.
  • the honeycomb structure 2 is provided with columnar electrode terminals 31a and 31b for applying a voltage to the honeycomb structure 2.
  • the electrode terminals 31a and 31b are provided so as to stand up against the surface of the outer peripheral wall 20.
  • the electrode terminals 31a and 31b are arranged so as to face each other with the central axis of the honeycomb structure 2 interposed therebetween.
  • the positions of the electrode terminals 31a and 31b related to the circumferential direction of the honeycomb structure 2 are arbitrary.
  • the electroheated carrier 1 may have electrodes 3a and 3b having the above.
  • the electrode layers 30a and 30b are made of a conductive material.
  • the electrode layers 30a and 30b are preferably an oxide ceramic, a metal or a mixture of a metal compound and an oxide ceramic, or carbon.
  • the metal may be either a simple substance metal or an alloy, and for example, silicon, aluminum, iron, stainless steel, titanium, tungsten, Ni—Cr alloy and the like can be preferably used.
  • the metal compound include those other than oxide ceramics, such as metal oxides, metal nitrides, metal carbides, metal siliceates, metal borides, and composite oxides. For example, FeSi 2 , CrSi 2 , alumina, etc. Silica, titanium oxide and the like can be preferably used.
  • Both the metal and the metal compound may be one kind alone, or two or more kinds may be used in combination.
  • Specific examples of the oxide ceramic include glass, cordierite, and mullite.
  • the glass may further contain an oxide consisting of at least one component selected from the group consisting of B, Mg, Al, Si, P, Ti and Zr. It is more preferable that at least one selected from the above group is further contained in that the strength of the electrode layers 30a and 30b is further improved.
  • each of the electrode layers 30a and 30b is on the surface of the outer peripheral wall 20 and is the circumference of the outer peripheral wall 20. It is preferable to extend the cells in a strip shape in the direction and the extending direction of the cell. Specifically, each of the electrode layers 30a and 30b 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 honeycomb structure 2. It is desirable from the viewpoint that the current easily spreads in the axial direction of the electrode layers 30a and 30b.
  • the thickness of each of the electrode layers 30a and 30b 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 30a and 30b 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 30a and 30b is relative to the tangent line of the outer surface of each of the electrode layers 30a and 30b at the measurement point when the portion of the electrode layer whose thickness is to be measured is observed in a cross section perpendicular to the stretching direction of the cell. It is defined as the thickness in the normal direction.
  • the electrical resistivity of the electrode layers 30a and 30b is not particularly limited, but is preferably 1 ⁇ 10 -7 to 5 ⁇ 10 -1 ⁇ ⁇ m. When the electrical resistivity of the electrode layers 30a and 30b is 5 ⁇ 10 -1 ⁇ ⁇ m or less, the resistance at the time of energization heating can be reduced.
  • the electrical resistivity of the electrode layers 30a and 30b is more preferably 5 ⁇ 10 -7 to 2.5 ⁇ 10 -1 ⁇ ⁇ m, and 1 ⁇ 10 -6 to 1.25 ⁇ 10 -1 ⁇ ⁇ m. Is even more preferable.
  • the electrical resistivity of the electrode layers 30a and 30b is a value measured at 25 ° C. by the four-terminal method.
  • the electrode terminals 31a and 31b are provided so as to stand up from the surfaces of the electrode layers 30a and 30b, and are electrically joined to the electrode layers 30a and 30b.
  • the applied voltage is preferably 12 to 900 V, more preferably 48 to 600 V, but the applied voltage can be changed as appropriate.
  • the electrode layers 30a and 30b may be omitted. When the electrode layers 30a and 30b are omitted, the electrode terminals 31a and 31b are provided so as to stand up from the surface of the outer peripheral wall 20 of the honeycomb structure 2.
  • Electrode terminal The sizes of the electrode terminals 31a and 31b are not limited, but for example, they are formed in a columnar shape having an area of both end faces of 10 to 800 mm 2 and a length of 10 to 100 mm in the direction in which the electrode terminals 31a and 31b stand up. can do.
  • the cross-sectional area of the electrode terminals 31a and 31b on the plane orthogonal to the length direction 31L of the electrode terminals 31a and 31b may be uniform in the length direction 31L of the electrode terminals 31a and 31b, but in the length direction 31L. It may change.
  • the cross-sectional area of the ends (bases) of the electrode terminals 31a and 31b on the honeycomb structure 2 side may be wider than the cross-sectional area on the tip side of the electrode terminals 31a and 31b. Further, in the electrode terminals 31a and 31b, at least at the base of the electrode terminals 31a and 31b, the cross-sectional area of the electrode terminals 31a and 31b becomes the bottom area of the electrode terminals 31a and 31b (on the honeycomb structure 2 side) as the distance from the honeycomb structure 2 increases. It may have a shape that gradually (continuously or stepwise) decreases from the end face (bottom surface) area). For example, the bases of the electrode terminals 31a and 31b may have a truncated cone shape. The areas of both end faces of the electrode terminals 31a and 31b may be different from each other.
  • the material of the electrode terminals 31a and 31b is made of ceramics or carbon. More preferably, it may be ceramics. When the electrode terminals 31a and 31b are made of ceramic, electrical connection to the honeycomb structure 2 is possible. Further, metal terminals may be joined to the tips of the electrode terminals 31a and 31b, respectively. Joining of ceramic or carbon electrode terminals to metal terminals can be performed by caulking, welding, conductive adhesive, or the like. As the material of the metal terminal, a conductive metal such as an iron alloy or a nickel alloy can be adopted.
  • the ceramics constituting the electrode terminals 31a and 31b include, but are not limited to, silicon carbide (SiC), and metal compounds such as metal silicates such as cermet tantalum (TaSi 2 ) and chromium silicate (CrSi 2). Further, a composite material (cermet) containing 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.
  • 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.
  • carbon constituting the electrode terminals 31a and 31b it is preferable that carbon is the main component.
  • the fact that carbon is the main component means that the carbon content is 50% by mass or more with respect to all the components constituting the electrode terminals 31a and 31b.
  • the carbon content is more preferably 80% by mass or more, and even more preferably 90% by mass or more.
  • the material of the electrode terminal may be the same as the material of the electrode layer.
  • Metal electrodes 4a and 4b are connected to the electrode terminals 31a and 31b, respectively. As particularly shown in FIG. 3, each of the electrode terminals 31a and 31b is provided with a connecting portion 32 for connecting to the metal electrodes 4a and 4b.
  • the metal electrodes 4a and 4b have, for example, a cap-like shape. In other words, the metal electrodes 4a and 4b have a circular top plate 40 and a peripheral wall 41 protruding from the outer edge of the top plate 40 in the plate thickness direction of the top plate 40.
  • the metal electrodes 4a and 4b are placed on the upper parts of the electrode terminals 31a and 31b.
  • the connection portion 32 of the present embodiment can be understood as a columnar portion provided above the electrode terminals 31a and 31b.
  • the outer surface of the connecting portion 32 and the inner surface of the metal electrodes 4a and 4b may be in close contact with each other as a whole, but the outer surface of the connecting portion 32 and the metal electrodes 4a and 4b are at least partly related to the circumferential direction of the connecting portion 32.
  • a gap 31G may be provided between the inner surface and the inner surface of the surface.
  • a bonding material made of, for example, a conductive brazing material is provided between the metal electrodes 4a and 4b and the electrode terminals 31a and 31b. Depending on the conductive bonding material, the metal electrodes 4a and 4b and the electrode terminals 31a and 31b Can be joined with.
  • the diameter of the connecting portion 32 of the present embodiment is uniform in the length direction 31L of the electrode terminals 31a and 31b. However, the diameter of the connecting portion 32 may change along the length direction 31L of the electrode terminals 31a and 31b.
  • the diameter of the connecting portion 32 is 30 mm or less. When the diameter is 30 mm or less, it is possible to avoid deterioration of the mountability of the electrically heated carrier 1 on the vehicle. From the viewpoint of lowering the resistance of the connecting portion, the diameter of the connecting portion 32 is preferably 5 mm or more, more preferably 10 mm or more, and even more preferably 15 mm or more. As will be described later, in the embodiment, the shape of at least a part of the cross section of the connecting portion 32 is non-circular (non-circular).
  • the diameter of the connecting portion 32 is the diameter of the minimum inclusion circle in the cross section of the connecting portion 32 on the surface 31S orthogonal to the length direction 31L of the electrode terminals 31a and 31b.
  • the minimum inclusion circle is the smallest virtual circle (perfect circle) that includes a cross section.
  • the cross section of the connecting portion 32 on the surface 31S orthogonal to the length direction 31L of the electrode terminals 31a and 31b is circular (perfect circle)
  • the surface area of the connecting portion 32 of the electrode terminals 31a and 31b is small and the current density is high. Since it becomes high, a desired current may not flow when the electrically heated carrier 1 is energized and heated.
  • the circularity of at least a part of the cross section of the connecting portion 32 on the surface 31S orthogonal to the length direction 31L of the electrode terminals 31a and 31b is 0.95 or less.
  • the circularity is 0.95 or less, the surface area of the connecting portion 32 can be increased and the current density can be reduced as compared with the case where the cross section of the connecting portion 32 is circular. As a result, a desired current can be more reliably passed when the electrically heated carrier 1 is energized and heated.
  • the circularity is more preferably 0.9 or less.
  • the circularity of the cross section of the connecting portion 32 is preferably 0.3 or more, and more preferably 0.5 or more.
  • the circularity can be calculated by the following formula (1).
  • Circularity 4 ⁇ ⁇ A / P 2 ...
  • A is the area of the cross section of the connecting portion 32 on the surface 31S orthogonal to the length direction 31L of the electrode terminals 31a and 31b
  • P is the peripheral length of the cross section.
  • the value of circularity is 1. The more complicated the shape of the cross section, the lower the circularity and the larger the surface area of the connecting portion 32.
  • FIG. 4 is an explanatory view showing a first aspect of the connection portion 32 of FIG. 3
  • FIG. 5 is an explanatory view showing a second aspect of the connection portion 32 of FIG. 3
  • FIG. 6 is an explanatory view of the connection portion 32 of FIG. It is explanatory drawing which shows the 3rd aspect.
  • the method of setting the circularity of the cross section of the connecting portion 32 to 0.95 or less is arbitrary.
  • the cross-sectional shape of the connecting portion 32 may be an ellipse as shown in FIG. 4, a circular shape having a notch 32a as shown in FIG. 5, or a convex portion 32b as shown in FIG. It may be a circular shape having the above, or it may be a more complicated shape.
  • the elliptical shape, the notch 32a, and the convex portion 32b are shown for easy understanding.
  • the shape of the cross section of the connecting portion 32 is not limited to the shape itself of FIGS. 4 to 6.
  • the ratio of the minor axis to the major axis is preferably 0.5 or more.
  • the ratio of the short axis to the long axis is preferably 0.5 or more.
  • the ellipse referred to here is not limited to a mathematical ellipse as shown in FIG. 4 (a), and is a convex curve having no corners as shown in FIGS. 4 (b) to 4 (d). Also includes shapes consisting of ellipses.
  • An ellipse can also be understood as an axisymmetric shape centered on each of two axes of symmetry that are orthogonal to each other. A perfect circle is not included in the ellipse.
  • the major axis refers to the longer axis of symmetry among the two axes orthogonal to each other, and the minor axis refers to the shorter axis of symmetry among the two axes orthogonal to each other. Since the ratio of the minor axis to the major axis is elliptical, it is less than 1, preferably 0.95 or less.
  • the notch 32a is formed into a triangular shape (see FIG. 5A) or a rectangular shape (see FIG. 5A), although it is not limited. It can be in the shape of a circle (see FIG. 5 (c)) or a circular shape (see FIG. 5 (c)).
  • FIGS. 5A to 5C one notch 32a is provided in the cross section of the connecting portion 32, but the number and arrangement of the notches 32a are arbitrary. Similarly, the size of the notch 32a is arbitrary.
  • the convex portion 32b is formed into a triangular shape (see FIG. 6A) or a rectangular shape (see FIG. 6A), although it is not limited. It can be in the shape of a circle (see FIG. 6 (c)) or a circular shape (see FIG. 6 (c)).
  • FIGS. 6A to 6C one convex portion 32b is provided in the cross section of the connecting portion 32, but the number and arrangement of the convex portions 32b are arbitrary. Similarly, the size of the convex portion 32b is also arbitrary.
  • the cross section of the connecting portion 32 may be elliptical with at least one of the notch 32a and the convex portion 32b.
  • the shape of the cross section of the connecting portion 32 may be uniform or changed in the length direction 31L of the electrode terminals 31a and 31b.
  • the notch 32a or the convex portion 32b may extend over the entire length of the connecting portion 32, or the notch 32a or the convex portion may extend to a part of the connecting portion 32.
  • 32b may be provided.
  • the electrically heated carrier 1 By supporting the catalyst on the electrically heated carrier 1, the electrically heated carrier 1 can be used as a catalyst.
  • a fluid such as automobile exhaust gas can flow through the flow paths of the plurality of cells 21a.
  • the catalyst include noble metal-based catalysts and catalysts other than these.
  • 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).
  • LNT catalyst NO x storage reduction catalyst
  • 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.
  • the step A1 for obtaining an unfired honeycomb structure with electrode terminals and the unfired honeycomb structure with electrode terminals are fired to obtain a honeycomb structure with electrode terminals.
  • the electrode layer forming paste and the electrode terminal forming paste may be attached to the honeycomb structure after calcination.
  • the electrode terminals made of carbon may be attached to the honeycomb structure.
  • step A1 a columnar honeycomb molded body that is a precursor of the honeycomb structure is produced, and an electrode layer forming paste is applied to the side surface of the honeycomb molded body to obtain an unfired honeycomb structure with the electrode layer forming paste.
  • This is a step of providing an electrode terminal on the electrode layer forming paste to obtain an unfired honeycomb structure with an electrode terminal.
  • boric acid a conductive filler containing Si atoms, and kaolin are mixed.
  • a borosilicate containing an alkaline atom, a conductive filler containing a Si atom, and kaolin are mixed.
  • the borosilicate may have a fibrous or particulate shape, and is preferably fibrous because it improves the extrudability of the mixture.
  • the mass ratio of boric acid is preferably 4 or more and 8 or less in order to facilitate obtaining the honeycomb structure 2 having a small temperature dependence of electrical resistivity.
  • the content of boron contained in the borosilicate can be increased by increasing the firing temperature described later. As the amount of boron doped in the silicate is increased, the electrical resistance of the honeycomb structure 2 can be further reduced.
  • binder examples include methyl cellulose, hydroxypropyl methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol and the like.
  • the binder content can be, for example, about 2% by mass.
  • the clay is extruded to produce a honeycomb molded body.
  • a mouthpiece having a desired overall shape, cell shape, partition wall thickness, cell density and the like can be used.
  • both bottom portions of the honeycomb molded body can be cut to obtain the desired length.
  • the dried honeycomb molded body is called a columnar honeycomb dried body.
  • the electrode layer forming paste for forming the electrode layer is prepared.
  • the electrode layer forming paste can be prepared by mixing silicon carbide and silicon at a mass ratio of 20:80 and mixing them with a binder and water.
  • the silicon carbide powder contained in the electrode layer forming raw material it is preferable to use a powder having an average particle size of 3 to 50 ⁇ m.
  • the average particle size of the silicon carbide powder is less than 3 ⁇ m, the number of interfaces increases and the resistance tends to be high. Further, when the average particle size of the silicon carbide powder is more than 50 ⁇ m, the strength is low and the heat impact resistance tends to be inferior.
  • the obtained electrode layer forming paste is applied to the side surface of the honeycomb molded body (typically, the columnar honeycomb dried body) to obtain an unfired honeycomb structure with the electrode layer forming paste.
  • 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.
  • 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 columnar honeycomb fired body, and the electrode layer forming paste is applied to the columnar honeycomb fired body.
  • the electrode terminal forming material for forming the electrode terminal is prepared.
  • the electrode terminal forming material can be kneaded by appropriately adding various additives to the ceramic powder blended according to the required characteristics of the electrode terminals.
  • the prepared and kneaded electrode terminal forming material is formed into a predetermined shape by press molding, and dried and / or fired. Since the electrode terminals are deformed by shrinkage during drying and / or firing, it is preferable to perform cutting and / or polishing after drying and / or firing.
  • the notch or the convex portion may be provided in advance in the mold for forming the electrode terminal, or grinding may be performed after drying and / or firing. ..
  • an electrode layer forming paste can be used.
  • the unfired honeycomb structure with electrode terminals is fired to obtain a honeycomb structure with electrode terminals.
  • the firing conditions can be under an inert gas atmosphere or an atmospheric atmosphere, below atmospheric pressure, a firing temperature of 1150 to 1350 ° C., and a firing time of 0.1 to 50 hours.
  • the firing atmosphere may be, for example, an inert gas atmosphere, and the firing pressure may be normal pressure.
  • it is preferable to reduce the residual oxygen from the viewpoint of preventing oxidation, and it is not possible after the atmosphere at the time of firing is set to a high vacuum of 1.0 ⁇ 10 -4 Pa or more. It is preferable to purge the active gas and fire it.
  • the inert gas atmosphere examples include an N 2 gas atmosphere, a helium gas atmosphere, and an argon gas atmosphere.
  • the unfired honeycomb structure with the electrode terminal forming paste may be dried before firing. Further, before firing, degreasing may be performed in order to remove the binder and the like. In this way, an electrically heated carrier in which the electrode terminals are electrically connected to the electrode layer is obtained.
  • FIG. 7 is an explanatory diagram showing an exhaust gas purification device according to an embodiment of the present invention.
  • the electrically heated carrier 1 according to the embodiment of the present invention described above can be used in an exhaust gas purification device.
  • the exhaust gas purifying device includes an electric heating type carrier 1, metal electrodes 4a and 4b connected to electrode terminals 31a and 31b of the electric heating type carrier 1, and a metal can body 5 holding the electric heating type carrier 1. And have.
  • the electrically heated carrier is installed in the middle of the exhaust gas flow path for flowing the exhaust gas from the engine.

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Abstract

This electrically heated carrier 1 is provided with: a columnar honeycomb structure 2 having an outer circumferential wall 20 and partition walls 21, which are arranged on the inside of the outer circumferential wall 20, and which demarcate a plurality of cells 21a that penetrate from one end surface to the other end surface, and form a flow passage; and columnar electrode terminals 31a and 31b for applying a voltage to the honeycomb structure. The electrode terminals 31a and 31b are provided with a connection part to be connected respectively to metal electrodes 4a and 4b. The diameter of the connection parts is 30 mm or less, and the circularity of a cross section of at least a portion of the connection parts in a plane orthogonal to the lengthwise direction of the electrode terminals is 0.95 or less.

Description

電気加熱式担体及び排気ガス浄化装置Electric heating type carrier and exhaust gas purification device
　本発明は、電気加熱式担体及び排気ガス浄化装置に関する。 The present invention relates to an electrically heated carrier and an exhaust gas purifying device.
　電気加熱触媒（ＥＨＣ）に用いられるセラミックス担体として、下記の特許文献１には、ＰＴＣ特性を有する担体を用いること、より具体的にはアルカリ系原子を含むホウケイ酸塩で構成されるマトリックスを用いることが開示されている。ＰＴＣ特性とは、温度が高くなるにつれて電気抵抗が上昇する特性である。ＰＴＣ特性を有する担体を用いることで、通電加熱時に電流が集中して流れることによる局所的な発熱に起因する偏った温度分布を改善することが図られている。 As the ceramic carrier used for the electric heating catalyst (EHC), in Patent Document 1 below, a carrier having PTC characteristics is used, and more specifically, a matrix composed of a borosilicate containing an alkaline atom is used. Is disclosed. The PTC characteristic is a characteristic in which the electrical resistance increases as the temperature rises. By using a carrier having PTC characteristics, it is possible to improve the uneven temperature distribution caused by local heat generation due to the concentrated flow of current during energization heating.
　一般的に、ＥＨＣには、セラミックス担体に電圧を印加するための電極が設けられる。電極は、セラミックス担体の外周壁上に設けられた電極層と、その電極層から起立するように設けられた円柱状の電極端子とが含まれる。下記の特許文献２には、円柱状のセラミックス体からなる電極端子に金属体を接合することが開示されている。 Generally, the EHC is provided with an electrode for applying a voltage to the ceramic carrier. The electrode includes an electrode layer provided on the outer peripheral wall of the ceramic carrier and a columnar electrode terminal provided so as to stand up from the electrode layer. Patent Document 2 below discloses that a metal body is bonded to an electrode terminal made of a columnar ceramic body.
特開２０１９－０１２６８２号公報Japanese Unexamined Patent Publication No. 2019-012682 特許第５８６２６３０号公報Japanese Patent No. 5862630
　本発明者らの検討の結果、電極端子が円柱状であると、より具体的には電極端子の断面の形状が円形であると、電極端子の表面積が小さく電流密度が高くなるため、セラミックス担体の通電加熱時に所望する電流が流せない課題があることが分かった。電極端子の径を大きくすれば接続部の接続面積を大きくできるが、金属電極が大きくなることで電気加熱式担体の車輛への搭載性が悪化する。 As a result of the studies by the present inventors, when the electrode terminals are columnar, more specifically, when the cross-sectional shape of the electrode terminals is circular, the surface area of the electrode terminals is small and the current density is high. It was found that there is a problem that the desired current cannot flow when the current is energized and heated. If the diameter of the electrode terminal is increased, the connection area of the connecting portion can be increased, but the larger metal electrode deteriorates the mountability of the electrically heated carrier on the vehicle.
　本発明は、上記のような課題を解決するためになされたものであり、その目的の一つは、通電加熱時に所望する電流を流すことができる電極端子を有する電気加熱式担体及び排気ガス浄化装置を提供することである。 The present invention has been made to solve the above problems, and one of the purposes thereof is an electrically heated carrier having an electrode terminal capable of passing a desired current during energization heating and exhaust gas purification. To provide the device.
　本発明に係る電気加熱式担体の一態様は、外周壁と、外周壁の内側に配設され、一方の端面から他方の端面まで貫通して流路を形成する複数のセルを区画形成する隔壁とを有する柱状のハニカム構造体と、ハニカム構造体に電圧を印加するための柱状の電極端子とを備え、電極端子には、金属電極と接続されるための接続部が設けられており、接続部の径が３０ｍｍ以下であり、電極端子の長さ方向に直交する面における接続部の少なくとも一部の断面の円形度が０．９５以下である。 One aspect of the electroheated carrier according to the present invention is a partition wall that is disposed inside the outer peripheral wall and partitions a plurality of cells that penetrate from one end face to the other end face to form a flow path. A columnar honeycomb structure having a The diameter of the portion is 30 mm or less, and the circularity of at least a part of the cross section of the connecting portion on the plane orthogonal to the length direction of the electrode terminal is 0.95 or less.
　本発明に係る排気ガス浄化装置の一態様は、上述の電気加熱式担体と、電気加熱式担体の電極端子と接続された金属電極と、電気加熱式担体を保持する金属製の缶体とを備える。 One aspect of the exhaust gas purification device according to the present invention comprises the above-mentioned electrically heated carrier, a metal electrode connected to an electrode terminal of the electrically heated carrier, and a metal can body holding the electrically heated carrier. Be prepared.
　本発明によれば、通電加熱時に所望する電流を流すことができる電極端子を有する電気加熱式担体及び排気ガス浄化装置を提供することができる。 According to the present invention, it is possible to provide an electrically heated carrier having an electrode terminal capable of passing a desired current during energization heating and an exhaust gas purifying device.
本発明の実施の形態における電気加熱式担体を示す斜視図である。It is a perspective view which shows the electric heating type carrier in embodiment of this invention. 図１の電気加熱式担体のセルの延伸方向に直交する断面図である。It is sectional drawing which is orthogonal to the stretching direction of the cell of the electroheating type carrier of FIG. 図２の電極端子を拡大して示す拡大断面図である。It is an enlarged cross-sectional view which shows the electrode terminal of FIG. 2 in an enlarged manner. 図３の接続部の第１態様を示す説明図である。It is explanatory drawing which shows the 1st aspect of the connection part of FIG. 図３の接続部の第２態様を示す説明図である。It is explanatory drawing which shows the 2nd aspect of the connection part of FIG. 図３の接続部の第３態様を示す説明図である。It is explanatory drawing which shows the 3rd aspect of the connection part of FIG. 本発明の実施形態に係る排気ガス浄化装置を示す説明図である。It is explanatory drawing which shows the exhaust gas purification apparatus which concerns on embodiment of this invention.
　以下、本発明を実施するための形態について、図面を参照して説明する。本発明は各実施の形態に限定されるものではなく、その要旨を逸脱しない範囲で構成要素を変形して具体化できる。また、各実施形態に開示されている複数の構成要素の適宜な組み合わせにより、種々の発明を形成できる。例えば、実施の形態に示される全構成要素からいくつかの構成要素を削除してもよい。さらに、異なる実施形態の構成要素を適宜組み合わせてもよい。 Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The present invention is not limited to each embodiment, and the components can be modified and embodied without departing from the gist thereof. In addition, various inventions can be formed by appropriately combining the plurality of components disclosed in each embodiment. For example, some components may be removed from all the components shown in the embodiments. Furthermore, the components of different embodiments may be combined as appropriate.
＜電気加熱式担体＞
　図１は本発明の実施の形態における電気加熱式担体１を示す斜視図であり、図２は図１の電気加熱式担体１のセルの延伸方向に直交する断面図であり、図３は図２の電極端子を拡大して示す拡大断面図である。 <Electric heating type carrier>
FIG. 1 is a perspective view showing an electrically heated carrier 1 according to an embodiment of the present invention, FIG. 2 is a cross-sectional view orthogonal to the extending direction of the cell of the electrically heated carrier 1 of FIG. 1, and FIG. 3 is a view. It is an enlarged cross-sectional view which shows the electrode terminal of 2 in an enlarged manner.
　図１～図３に示すように、本実施の形態の電気加熱式担体１は、ハニカム構造体２、一対の電極３ａ，３ｂを有している。 As shown in FIGS. 1 to 3, the electrically heated carrier 1 of the present embodiment has a honeycomb structure 2 and a pair of electrodes 3a and 3b.
（１．ハニカム構造体）
　ハニカム構造体２は、柱状の構造体であり、外周壁２０と、外周壁２０の内側に配設され、一方の端面から他方の端面まで貫通して流路を形成する複数のセル２１ａを区画形成する隔壁２１とを有する。 (1. Honeycomb structure)
The honeycomb structure 2 is a columnar structure, and partitions the outer peripheral wall 20 and a plurality of cells 21a arranged inside the outer peripheral wall 20 and penetrating from one end face to the other end face to form a flow path. It has a partition wall 21 to be formed.
　ハニカム構造体２は、セラミックスで構成されており、当該セラミックスとしては、アルカリ系原子を含むホウケイ酸塩を用いることができる。当該アルカリ系原子としては、例えば、Ｎａ、Ｍｇ、Ｋ、Ｃａ、Ｌｉ、Ｂｅ、Ｓｒ、Ｃｓ、およびＢａなどが挙げられる。ホウケイ酸塩は、アルカリ金属原子を１種または２種以上含んでいてもよく、アルカリ土類金属原子を１種または２種以上含んでいてもよく、これらの組み合わせを含んでいてもよい。アルカリ系原子として、より好ましくは、Ｎａ、Ｍｇ、Ｋ、またはＣａである。 The honeycomb structure 2 is made of ceramics, and borosilicate containing an alkaline atom can be used as the ceramics. Examples of the alkaline atom include Na, Mg, K, Ca, Li, Be, Sr, Cs, and Ba. The borosilicate may contain one or more kinds of alkali metal atoms, may contain one or more kinds of alkaline earth metal atoms, or may contain a combination thereof. The alkaline atom is more preferably Na, Mg, K, or Ca.
　詳細は後述するが、ハニカム構造体２は、上述のアルカリ系原子を含むホウケイ酸塩から構成されるマトリックスと、導電性フィラーから構成されるドメインとを有してもよい。マトリックスは、ハニカム構造体２の母材となる部位である。なお、マトリックスは、非晶質であってもよいし、結晶質であってもよい。このような構成によれば、ＥＨＣへの通電加熱時に電気抵抗を支配する領域が、母材であるマトリックスとなる。マトリックスは、ＳｉＣ材質と比べて電気抵抗率の温度依存性が小さく、かつ、電気抵抗率がＰＴＣ特性（温度が高くなるにつれて電気抵抗が上昇する特性）を示す。 Although details will be described later, the honeycomb structure 2 may have a matrix composed of the above-mentioned borosilicate containing an alkaline atom and a domain composed of a conductive filler. The matrix is a portion that serves as a base material for the honeycomb structure 2. The matrix may be amorphous or crystalline. According to such a configuration, the region that controls the electric resistance when the EHC is energized and heated becomes the matrix that is the base material. The matrix has a smaller temperature dependence of electrical resistivity than the SiC material, and the electrical resistivity exhibits PTC characteristics (characteristics in which the electrical resistance increases as the temperature rises).
　ホウケイ酸塩において、アルカリ系原子の合計含有量は、１０質量％以下であってもよい。より好ましくは５質量％以下であってもよく、２質量％以下であってもよい。このような構成によれば、マトリックスを低電気抵抗化させやすくなり、マトリックスの電気抵抗率が、よりＰＴＣ特性を示すようになる。また、酸化雰囲気での焼成時におけるハニカム構造体２の表面側へのアルカリ系原子の偏析による絶縁性ガラス被膜の形成を抑制することができる。下限については、特に限定はないが、アルカリ系原子の合計含有量は、０．０１質量％以上であってもよく、０．２質量％以上であってもよい。アルカリ系原子は、導電性フィラーの酸化抑制のために、意図的に添加されてもよい。また、ハニカム構造体２の原料から比較的混入しやすい元素であるため、完全に除去するには製造工程を複雑化してしまうため、通常は、上記の範囲内で含まれる。なお、ハニカム構造体２において、原料として、アルカリ系原子を含むホウケイ酸ガラスを使用せずに、ホウ酸を用いることで、アルカリ系原子を低減することも可能である。 In borosilicate, the total content of alkaline atoms may be 10% by mass or less. More preferably, it may be 5% by mass or less, or 2% by mass or less. According to such a configuration, it becomes easy to reduce the electric resistance of the matrix, and the electrical resistivity of the matrix shows more PTC characteristics. Further, it is possible to suppress the formation of an insulating glass film due to the segregation of alkaline atoms on the surface side of the honeycomb structure 2 during firing in an oxidizing atmosphere. The lower limit is not particularly limited, but the total content of alkaline atoms may be 0.01% by mass or more, or 0.2% by mass or more. Alkaline atoms may be intentionally added to suppress the oxidation of the conductive filler. Further, since it is an element that is relatively easily mixed from the raw material of the honeycomb structure 2, it complicates the manufacturing process to completely remove it, and therefore, it is usually included within the above range. In the honeycomb structure 2, it is possible to reduce alkaline atoms by using boric acid instead of using borosilicate glass containing alkaline atoms as a raw material.
　ここで、「アルカリ系原子の合計含有量」とは、ホウケイ酸塩がアルカリ系原子を１種含む場合には、その１種のアルカリ系原子の質量％を示す。また、ホウケイ酸塩がアルカリ系原子を複数種含む場合には、その複数の各アルカリ系原子の各含有量（質量％）との合計の含有量（質量％）を示す。 Here, the "total content of alkaline atoms" indicates the mass% of one alkaline atom when the borosilicate contains one alkaline atom. When the borosilicate contains a plurality of alkaline atoms, the total content (mass%) with the content (mass%) of each of the plurality of alkaline atoms is shown.
　ホウケイ酸塩を構成する、Ｂ（ホウ素）原子、Ｓｉ（シリコン）原子、Ｏ（酸素）原子のぞれぞれの含有量としては、例えば、以下の範囲であることが好ましい。ホウケイ酸塩におけるＢ原子の含有量は、０．１質量％以上５質量％以下である。ホウケイ酸塩におけるＳｉ原子の含有量は、５質量％以上４０質量％以下である。ホウケイ酸塩におけるＯ原子の含有量は、４０質量％以上８５質量％以下である。このような構成によれば、ハニカム構造体２において、ＰＴＣ特性を示しやすくすることができる。 The content of each of the B (boron) atom, Si (silicon) atom, and O (oxygen) atom constituting the borosilicate is preferably in the following range, for example. The content of B atom in borosilicate is 0.1% by mass or more and 5% by mass or less. The content of Si atom in borosilicate is 5% by mass or more and 40% by mass or less. The content of O atom in borosilicate is 40% by mass or more and 85% by mass or less. According to such a configuration, it is possible to easily show the PTC characteristics in the honeycomb structure 2.
　ホウケイ酸塩としては、アルミノホウケイ酸塩などを用いることができる。このような構成によれば、電気抵抗率の温度依存性が小さく、かつ、電気抵抗率がＰＴＣ特性を示す、または、電気抵抗率の温度依存性が抑制されたハニカム構造体２を得ることができる。アルミノホウケイ酸塩におけるＡｌ原子の含有量は、例えば、０．５質量％以上１０質量％以下であってよい。 As the borosilicate, aluminoborosilicate or the like can be used. According to such a configuration, it is possible to obtain a honeycomb structure 2 in which the temperature dependence of the electrical resistivity is small, the electrical resistivity exhibits PTC characteristics, or the temperature dependence of the electrical resistivity is suppressed. can. The content of Al atom in the aluminum borosilicate may be, for example, 0.5% by mass or more and 10% by mass or less.
　上述したホウケイ酸塩における各原子の他にマトリックスを構成するホウケイ酸塩に含まれる原子としては、例えば、Ｆｅ、Ｃなどが挙げられる。上述した各原子のうち、アルカリ系原子、Ｓｉ、Ｏ、Ａｌの含有量については、電子線マイクロアナライザ（ＥＰＭＡ）分析装置を用いて測定することができる。上述した各原子のうち、Ｂの含有量については、誘導結合プラズマ（ＩＣＰ）分析装置を用いて測定することができる。ＩＣＰ分析によると、ハニカム構造体２全体におけるＢ含有量が測定されるため、得られた測定結果は、ホウケイ酸塩におけるＢ含有量に換算される。 Examples of the atoms contained in the borosilicate constituting the matrix in addition to the atoms in the above-mentioned borosilicate include Fe and C. Of the above-mentioned atoms, the contents of alkaline atoms, Si, O, and Al can be measured using an electron probe microanalyzer (EPMA) analyzer. Of the above-mentioned atoms, the B content can be measured using an inductively coupled plasma (ICP) analyzer. According to the ICP analysis, the B content in the entire honeycomb structure 2 is measured, so that the obtained measurement result is converted into the B content in the borosilicate.
　ハニカム構造体２が、マトリックスと導電性フィラーとを有していると、マトリックスの電気抵抗率と導電性フィラーの電気抵抗率との足し合わせによってハニカム構造体２全体の電気抵抗率が決定される。このため、導電性フィラーの導電性、導電性フィラーの含有量を調整することで、ハニカム構造体２の電気抵抗率の制御が可能になる。導電性フィラーの電気抵抗率は、ＰＴＣ特性、ＮＴＣ特性（温度が高くなるにつれて電気抵抗が小さくなる特性）のいずれを示してもよいし、電気抵抗率の温度依存性がなくてもよい。 When the honeycomb structure 2 has a matrix and a conductive filler, the electrical resistivity of the entire honeycomb structure 2 is determined by adding the electrical resistivity of the matrix and the electrical resistivity of the conductive filler. .. Therefore, the electrical resistivity of the honeycomb structure 2 can be controlled by adjusting the conductivity of the conductive filler and the content of the conductive filler. The electrical resistivity of the conductive filler may exhibit either PTC characteristics or NTC characteristics (characteristics in which the electrical resistance decreases as the temperature rises), and the electrical resistivity may not be temperature-dependent.
　導電性フィラーは、Ｓｉ原子を含んでいてもよい。このような構成によれば、ハニカム構造体２の形状安定性を向上させることが可能である。 The conductive filler may contain Si atoms. According to such a configuration, it is possible to improve the shape stability of the honeycomb structure 2.
　Ｓｉ原子を含む導電性フィラーとしては、例えば、Ｓｉ粒子、Ｆｅ－Ｓｉ系粒子、Ｓｉ－Ｗ系粒子、Ｓｉ－Ｃ系粒子、Ｓｉ－Ｍｏ系粒子、Ｓｉ－Ｔｉ系粒子などが挙げられる。これらは１種または２種以上を併用することができる。 Examples of the conductive filler containing Si atoms include Si particles, Fe—Si particles, SiW particles, SiC particles, Si—Mo particles, Si—Ti particles and the like. These can be used alone or in combination of two or more.
　Ｓｉ粒子は、ドーパントによりドープされているＳｉ粒子であってもよい。ドーパントとしては、ホウ素（Ｂ）、アルミニウム（Ａｌ）、ガリウム（Ｇａ）、インジウム（Ｉｎ）、窒素（Ｎ）、リン（Ｐ）、ヒ素（Ａｓ）、アンチモン（Ｓｂ）、ビスマス（Ｂｉ）等が挙げられる。ドーパント濃度としては、１×１０16～５×１０20個／ｃｍ3という範囲でケイ素粒子中にドーパントとして含まれてもよい。ここで、一般に、Ｓｉ粒子中のドーパントの濃度が高くなるとハニカム構造体２の体積抵抗率が下がり、Ｓｉ粒子中のドーパントの濃度が低くなるとハニカム構造体２の体積抵抗率が上がる。ハニカム構造体２に含まれるケイ素粒子におけるドーパント量は、５×１０16～５×１０20個／ｃｍ3であるのが好ましく、５×１０17～５×１０20個／ｃｍ3であるのがより好ましい。 The Si particles may be Si particles doped with a dopant. Dopants include boron (B), aluminum (Al), gallium (Ga), indium (In), nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi) and the like. Can be mentioned. The dopant concentration may be contained as a dopant in the silicon particles in the range of 1 × 10 16 to 5 × 10 20 pieces / cm 3. Here, in general, the volume resistivity of the honeycomb structure 2 decreases as the concentration of the dopant in the Si particles increases, and the volume resistivity of the honeycomb structure 2 increases as the concentration of the dopant in the Si particles decreases. The amount of dopant in the silicon particles contained in the honeycomb structure 2 is preferably 5 × 10 16 to 5 × 10 20 pieces / cm 3 , and 5 × 10 17 to 5 × 10 20 pieces / cm 3. More preferred.
　ハニカム構造体２に含まれるＳｉ粒子中のドーパントは同族元素であれば、カウンタードーピングの影響を受けずに導電性を発現できるため、複数の種類の元素を含んでいてもよい。また、ドーパントが、Ｂ及びＡｌからなる群から選択される一種または二種であるのがより好ましい。また、Ｎ及びＰからなる群から選択される一種または二種であるのも好ましい。 If the dopant in the Si particles contained in the honeycomb structure 2 is a homologous element, it may contain a plurality of types of elements because it can exhibit conductivity without being affected by counterdoping. Further, it is more preferable that the dopant is one or two selected from the group consisting of B and Al. It is also preferable that it is one or two selected from the group consisting of N and P.
　ハニカム構造体２がマトリックスと導電性フィラーとを有する場合、ハニカム構造体２は、マトリックスと導電性フィラーとを合計で５０ｖｏｌ％以上含有する構成であってもよい。 When the honeycomb structure 2 has a matrix and a conductive filler, the honeycomb structure 2 may have a configuration in which the matrix and the conductive filler are contained in a total of 50 vol% or more.
　ハニカム構造体２の電気抵抗上昇率は、１×１０-8～５×１０-4Ω・ｍ／Ｋであるのが好ましい。ハニカム構造体２の電気抵抗上昇率が１×１０-8Ω・ｍ／Ｋ以上であると、通電加熱時の温度分布の抑制がしやすくなる。ハニカム構造体２の電気抵抗上昇率が５×１０-4Ω・ｍ／Ｋ以下であると、通電加熱時の抵抗変化を小さくすることができる。ハニカム構造体２の電気抵抗上昇率が５×１０-8～１×１０-4Ω・ｍ／Ｋであるのがより好ましく、１×１０-7～１×１０-4Ω・ｍ／Ｋであるのが更により好ましい。ハニカム構造体２の電気抵抗上昇率は、まず、四端子法により、５０℃及び４００℃での２点の電気抵抗率を測定し、４００℃の電気抵抗率から５０℃の電気抵抗率を引き算して導出した値を、４００℃と５０℃の温度差３５０℃で割り算して電気抵抗上昇率を算出することで求めることができる。 The rate of increase in electrical resistance of the honeycomb structure 2 is preferably 1 × 10 -8 to 5 × 10 -4 Ω · m / K. When the rate of increase in electrical resistance of the honeycomb structure 2 is 1 × 10 -8 Ω · m / K or more, it becomes easy to suppress the temperature distribution during energization and heating. When the rate of increase in electrical resistance of the honeycomb structure 2 is 5 × 10 -4 Ω · m / K or less, the change in resistance during energization and heating can be reduced. The rate of increase in electrical resistance of the honeycomb structure 2 is more preferably 5 × 10 -8 to 1 × 10 -4 Ω ・ m / K, and 1 × 10 -7 to 1 × 10 -4 Ω ・ m / K. It is even more preferable to have it. For the electrical resistivity increase rate of the honeycomb structure 2, first, the electrical resistivity at two points at 50 ° C. and 400 ° C. is measured by the four-terminal method, and the electrical resistivity at 50 ° C. is subtracted from the electrical resistivity at 400 ° C. It can be obtained by dividing the value derived in this manner by the temperature difference of 350 ° C. between 400 ° C. and 50 ° C. to calculate the rate of increase in electrical resistance.
　ハニカム構造体２の外形は柱状である限り特に限定されず、例えば、底面が円形の柱状（円柱形状）、底面がオーバル形状の柱状、底面が多角形（四角形、五角形、六角形、七角形、八角形等）の柱状等の形状とすることができる。また、ハニカム構造体２の大きさは、耐熱性を高める（外周壁の周方向に入るクラックを抑制する）という理由により、底面の面積が２０００～２００００ｍｍ2であることが好ましく、５０００～１７０００ｍｍ2であることがより好ましい。 The outer shape of the honeycomb structure 2 is not particularly limited as long as it is columnar. It can have a columnar shape (octagonal shape, etc.). The size of the honeycomb structure 2, for the reason of enhancing the heat resistance (suppress crack entering the circumferential direction of the outer peripheral wall), it is preferable that the area of the bottom is 2000 ~ 20000mm 2, 5000 ~ 17000mm 2 Is more preferable.
　ハニカム構造体２は、導電性を有する。ハニカム構造体２は、通電してジュール熱により発熱可能である限り、電気抵抗率については特に制限はないが、１×１０-5～２Ω・ｍであることが好ましく、５×１０-5～１Ω・ｍであることがより好ましく、１×１０-4～０．５Ω・ｍであることが更により好ましい。本発明において、ハニカム構造体２の電気抵抗率は、四端子法により２５℃で測定した値とする。 The honeycomb structure 2 has conductivity. The honeycomb structure 2 is not particularly limited in electrical resistivity as long as it can be energized and generate heat by Joule heat , but it is preferably 1 × 10 -5 to 2Ω · m, and 5 × 10 -5 to It is more preferably 1 Ω · m, and even more preferably 1 × 10 -4 to 0.5 Ω · m. In the present invention, the electrical resistivity of the honeycomb structure 2 is a value measured at 25 ° C. by the four-terminal method.
　セル２１ａの延伸方向に垂直な断面におけるセルの形状に制限はないが、四角形、六角形、八角形、又はこれらの組み合わせであることが好ましい。これ等のなかでも、四角形及び六角形が好ましい。セル形状をこのようにすることにより、ハニカム構造体２に排気ガスを流したときの圧力損失が小さくなり、触媒の浄化性能が優れたものとなる。構造強度及び加熱均一性を両立させやすいという観点からは、四角形が特に好ましい。 There is no limitation on the shape of the cell in the cross section perpendicular to the extending direction of the cell 21a, 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 cell shape in this way, the pressure loss when the exhaust gas is passed through the honeycomb structure 2 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.
　セル２１ａを区画形成する隔壁２１の厚みは、０．１～０．３ｍｍであることが好ましく、０．１～０．２ｍｍであることがより好ましい。隔壁２１の厚みが０．１ｍｍ以上であることで、ハニカム構造体２の強度が低下するのを抑制可能である。隔壁２１の厚みが０．３ｍｍ以下であることで、ハニカム構造体２を触媒担体として用いて、触媒を担持した場合に、排気ガスを流したときの圧力損失が大きくなるのを抑制できる。本発明において、隔壁２１の厚みは、セル２１ａの延伸方向に垂直な断面において、隣接するセル２１ａの重心同士を結ぶ線分のうち、隔壁２１を通過する部分の長さとして定義される。 The thickness of the partition wall 21 forming the cell 21a is preferably 0.1 to 0.3 mm, more preferably 0.1 to 0.2 mm. When the thickness of the partition wall 21 is 0.1 mm or more, it is possible to suppress a decrease in the strength of the honeycomb structure 2. When the thickness of the partition wall 21 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 2 is used as a catalyst carrier and a catalyst is supported. In the present invention, the thickness of the partition wall 21 is defined as the length of the portion of the line segment connecting the centers of gravity of the adjacent cells 21a that passes through the partition wall 21 in the cross section perpendicular to the extending direction of the cell 21a.
　ハニカム構造体２は、セル２１ａの流路方向に垂直な断面において、セル密度が４０～１５０セル／ｃｍ2であることが好ましく、６０～１００セル／ｃｍ2であることがより好ましい。セル密度をこのような範囲にすることにより、排気ガスを流したときの圧力損失を小さくした状態で、触媒の浄化性能を高くすることができる。セル密度が４０セル／ｃｍ2以上であると、触媒担持面積が十分に確保される。セル密度が１５０セル／ｃｍ2以下であるとハニカム構造体２を触媒担体として用いて、触媒を担持した場合に、排気ガスを流したときの圧力損失が大きくなりすぎることが抑制される。セル密度は、外周壁２０部分を除くハニカム構造体２の一つの底面部分の面積でセル数を除して得られる値である。 The honeycomb structure 2 preferably has a cell density of 40 to 150 cells / cm 2 , and more preferably 60 to 100 cells / cm 2 in a cross section perpendicular to the flow path direction of the cells 21a. 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 honeycomb structure 2 is used as a catalyst carrier and the catalyst is supported, the pressure loss when the exhaust gas is flowed is suppressed 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 honeycomb structure 2 excluding the outer peripheral wall 20 portion.
　ハニカム構造体２の外周壁２０を設けることは、ハニカム構造体２の構造強度を確保し、また、セル２１ａを流れる流体が外周壁２０から漏洩するのを抑制する観点で有用である。具体的には、外周壁２０の厚みは好ましくは０．１ｍｍ以上であり、より好ましくは０．１５ｍｍ以上、更により好ましくは０．２ｍｍ以上である。但し、外周壁２０を厚くしすぎると高強度になりすぎてしまい、隔壁２１との強度バランスが崩れて耐熱衝撃性が低下することから、外周壁２０の厚みは好ましくは１ｍｍ以下であり、より好ましくは０．７ｍｍ以下であり、更により好ましくは０．５ｍｍ以下である。ここで、外周壁２０の厚みは、厚みを測定しようとする外周壁２０の箇所をセルの延伸方向に垂直な断面で観察したときに、当該測定箇所における外周壁２０の接線に対する法線方向の厚みとして定義される。 Providing the outer peripheral wall 20 of the honeycomb structure 2 is useful from the viewpoint of ensuring the structural strength of the honeycomb structure 2 and suppressing the fluid flowing through the cell 21a from leaking from the outer peripheral wall 20. Specifically, the thickness of the outer peripheral wall 20 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 20 is made too thick, the strength becomes too high, the strength balance with the partition wall 21 is lost, and the heat impact resistance is lowered. Therefore, the thickness of the outer peripheral wall 20 is preferably 1 mm or less, and more. It is preferably 0.7 mm or less, and even more preferably 0.5 mm or less. Here, the thickness of the outer peripheral wall 20 is the normal direction with respect to the tangent line of the outer peripheral wall 20 at the measurement location when the portion of the outer peripheral wall 20 whose thickness is to be measured is observed in a cross section perpendicular to the extending direction of the cell. Defined as thickness.
　隔壁２１は、気孔率が３０％以下であることが好ましい。隔壁２１の気孔率が３０％以下であると、キャニング時に破損する恐れが低減される。隔壁２１の気孔率は２０％以下であることがより好ましく、１０％以下であるのが更により好ましい。気孔率は、隔壁１３のＳＥＭ観察画像を気孔と気孔以外（具体的にはセラミックス材料部分）とを二値化して算出した値である。ハニカム構造体２を触媒担体として用いて、隔壁２１に触媒を担持した場合に、隔壁２１と触媒との剥離を抑制するために、隔壁２１は、気孔率が０．１％以上であることが好ましく、１％以上であることが好ましく、２％以上であることがより好ましく、５％以上であることが更により好ましい。 The partition wall 21 preferably has a porosity of 30% or less. When the porosity of the partition wall 21 is 30% or less, the risk of damage during canning is reduced. The porosity of the partition wall 21 is more preferably 20% or less, and even more preferably 10% or less. The porosity is a value calculated by binarizing the pores and the non-pores (specifically, the ceramic material portion) in the SEM observation image of the partition wall 13. When the honeycomb structure 2 is used as a catalyst carrier and the catalyst is supported on the partition wall 21, the partition wall 21 has a porosity of 0.1% or more in order to suppress peeling between the partition wall 21 and the catalyst. It is preferably 1% or more, more preferably 2% or more, and even more preferably 5% or more.
（２．電極及び金属電極）
　ハニカム構造体２には、ハニカム構造体２に電圧を印加するための柱状の電極端子３１ａ，３１ｂが設けられている。電極端子３１ａ，３１ｂは、外周壁２０の表面に対して起立するように設けられている。電極端子３１ａ，３１ｂは、ハニカム構造体２の中心軸を挟んで対向するように配設されている。しかしながら、ハニカム構造体２の周方向に係る電極端子３１ａ，３１ｂの配置位置は任意である。 (2. Electrodes and metal electrodes)
The honeycomb structure 2 is provided with columnar electrode terminals 31a and 31b for applying a voltage to the honeycomb structure 2. The electrode terminals 31a and 31b are provided so as to stand up against the surface of the outer peripheral wall 20. The electrode terminals 31a and 31b are arranged so as to face each other with the central axis of the honeycomb structure 2 interposed therebetween. However, the positions of the electrode terminals 31a and 31b related to the circumferential direction of the honeycomb structure 2 are arbitrary.
　図１に示すように、セル２１ａの延伸方向に伸びるように外周壁２０上に設けられた一対の電極層３０ａ，３０ｂと、電極層３０ａ，３０ｂ上に設けられた電極端子３１ａ，３１ｂと、を有する電極３ａ，３ｂを電気加熱式担体１が有してもよい。 As shown in FIG. 1, a pair of electrode layers 30a and 30b provided on the outer peripheral wall 20 so as to extend in the extending direction of the cell 21a, and electrode terminals 31a and 31b provided on the electrode layers 30a and 30b. The electroheated carrier 1 may have electrodes 3a and 3b having the above.
　電極層３０ａ，３０ｂは導電性を有する材料で形成される。電極層３０ａ，３０ｂは、酸化物セラミック、金属若しくは金属化合物と酸化物セラミックとの混合物、又はカーボンであることが好ましい。金属として、単体金属又は合金のいずれでもよく、例えばシリコン、アルミニウム、鉄、ステンレス、チタン、タングステン、Ｎｉ－Ｃｒ合金などを好適に用いることができる。金属化合物として、酸化物セラミック以外の物であって、金属酸化物、金属窒化物、金属炭化物、金属珪化物、金属ホウ化物、複合酸化物等が挙げられ、例えばＦｅＳｉ2、ＣｒＳｉ2、アルミナ、シリカ、酸化チタンなどを好適に用いることができる。金属と金属化合物は、いずれも、単独一種でもよく、二種以上を併用しても良い。酸化物セラミックとしては、具体的には、ガラス、コージェライト、ムライトなどがある。ガラスは、Ｂ、Ｍｇ、Ａｌ、Ｓｉ、Ｐ、Ｔｉ及びＺｒからなる群から選択される少なくとも一種の成分からなる酸化物を更に含んでも良い。上記群より選択される少なくとも一種を更に含んでいると、電極層３０ａ，３０ｂの強度がより向上する点でより好ましい。 The electrode layers 30a and 30b are made of a conductive material. The electrode layers 30a and 30b are preferably an oxide ceramic, a metal or a mixture of a metal compound and an oxide ceramic, or carbon. The metal may be either a simple substance metal or an alloy, and for example, silicon, aluminum, iron, stainless steel, titanium, tungsten, Ni—Cr alloy and the like can be preferably used. Examples of the metal compound include those other than oxide ceramics, such as metal oxides, metal nitrides, metal carbides, metal siliceates, metal borides, and composite oxides. For example, FeSi 2 , CrSi 2 , alumina, etc. Silica, titanium oxide and the like can be preferably used. Both the metal and the metal compound may be one kind alone, or two or more kinds may be used in combination. Specific examples of the oxide ceramic include glass, cordierite, and mullite. The glass may further contain an oxide consisting of at least one component selected from the group consisting of B, Mg, Al, Si, P, Ti and Zr. It is more preferable that at least one selected from the above group is further contained in that the strength of the electrode layers 30a and 30b is further improved.
　電極層３０ａ，３０ｂの形成領域に特段の制約はないが、ハニカム構造体２の均一発熱性を高めるという観点からは、各電極層３０ａ，３０ｂは外周壁２０の表面上で外周壁２０の周方向及びセルの延伸方向に帯状に延設することが好ましい。具体的には、各電極層３０ａ，３０ｂは、ハニカム構造体２の両底面間の８０％以上の長さに亘って、好ましくは９０％以上の長さに亘って、より好ましくは全長に亘って延びていることが、電極層３０ａ，３０ｂの軸方向へ電流が広がりやすいという観点から望ましい。 There are no particular restrictions on the formation regions of the electrode layers 30a and 30b, but from the viewpoint of enhancing the uniform heat generation of the honeycomb structure 2, each of the electrode layers 30a and 30b is on the surface of the outer peripheral wall 20 and is the circumference of the outer peripheral wall 20. It is preferable to extend the cells in a strip shape in the direction and the extending direction of the cell. Specifically, each of the electrode layers 30a and 30b 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 honeycomb structure 2. It is desirable from the viewpoint that the current easily spreads in the axial direction of the electrode layers 30a and 30b.
　各電極層３０ａ，３０ｂの厚みは、０．０１～５ｍｍであることが好ましく、０．０１～３ｍｍであることがより好ましい。このような範囲とすることにより均一発熱性を高めることができる。各電極層３０ａ，３０ｂの厚みが０．０１ｍｍ以上であると、電気抵抗が適切に制御され、より均一に発熱することができる。５ｍｍ以下であると、キャニング時に破損する恐れが低減される。各電極層３０ａ，３０ｂの厚みは、厚みを測定しようとする電極層の箇所をセルの延伸方向に垂直な断面で観察したときに、各電極層３０ａ，３０ｂの外面の当該測定箇所における接線に対する法線方向の厚みとして定義される。 The thickness of each of the electrode layers 30a and 30b 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 30a and 30b 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 30a and 30b is relative to the tangent line of the outer surface of each of the electrode layers 30a and 30b at the measurement point when the portion of the electrode layer whose thickness is to be measured is observed in a cross section perpendicular to the stretching direction of the cell. It is defined as the thickness in the normal direction.
　電極層３０ａ，３０ｂの電気抵抗率については特に制限はないが、１×１０-7～５×１０-1Ω・ｍであることが好ましい。電極層３０ａ，３０ｂの電気抵抗率が５×１０-1Ω・ｍ以下であると、通電加熱時の抵抗を小さくすることができる。電極層３０ａ，３０ｂの電気抵抗率は、５×１０-7～２．５×１０-1Ω・ｍであることがより好ましく、１×１０-6～１．２５×１０-1Ω・ｍであることが更により好ましい。本発明において、電極層３０ａ，３０ｂの電気抵抗率は、四端子法により２５℃で測定した値とする。 The electrical resistivity of the electrode layers 30a and 30b is not particularly limited, but is preferably 1 × 10 -7 to 5 × 10 -1 Ω · m. When the electrical resistivity of the electrode layers 30a and 30b is 5 × 10 -1 Ω · m or less, the resistance at the time of energization heating can be reduced. The electrical resistivity of the electrode layers 30a and 30b is more preferably 5 × 10 -7 to 2.5 × 10 -1 Ω · m, and 1 × 10 -6 to 1.25 × 10 -1 Ω · m. Is even more preferable. In the present invention, the electrical resistivity of the electrode layers 30a and 30b is a value measured at 25 ° C. by the four-terminal method.
　図１において、電極端子３１ａ，３１ｂは、電極層３０ａ，３０ｂの表面から起立するように設けられており、電気的に電極層３０ａ，３０ｂに接合されている。これにより、電極端子３１ａ，３１ｂに電圧を印加するとジュール熱によりハニカム構造体２を発熱させることが可能である。このため、ハニカム構造体２はヒーターとしても好適に用いることができる。印加する電圧は１２～９００Ｖが好ましく、４８～６００Ｖがより好ましいが、印加する電圧は適宜変更可能である。なお、電極層３０ａ，３０ｂを省略してもよい。電極層３０ａ，３０ｂを省略する場合は、電極端子３１ａ，３１ｂは、ハニカム構造体２の外周壁２０の表面から起立するように設けられる。 In FIG. 1, the electrode terminals 31a and 31b are provided so as to stand up from the surfaces of the electrode layers 30a and 30b, and are electrically joined to the electrode layers 30a and 30b. As a result, when a voltage is applied to the electrode terminals 31a and 31b, the honeycomb structure 2 can be heated by Joule heat. Therefore, the honeycomb structure 2 can be suitably used as a heater. The applied voltage is preferably 12 to 900 V, more preferably 48 to 600 V, but the applied voltage can be changed as appropriate. The electrode layers 30a and 30b may be omitted. When the electrode layers 30a and 30b are omitted, the electrode terminals 31a and 31b are provided so as to stand up from the surface of the outer peripheral wall 20 of the honeycomb structure 2.
（３．電極端子）
　電極端子３１ａ，３１ｂの大きさは、限定的ではないが、例えば、両端面の面積が１０～８００ｍｍ2であり、電極端子３１ａ，３１ｂが起立する方向の長さが１０～１００ｍｍの柱状に形成することができる。電極端子３１ａ，３１ｂの長さ方向３１Ｌに直交する面における電極端子３１ａ，３１ｂの断面積は、電極端子３１ａ，３１ｂの長さ方向３１Ｌに一様であってもよいが、長さ方向３１Ｌに変化してもよい。ハニカム構造体２側の電極端子３１ａ，３１ｂの端部（基部）の断面積を電極端子３１ａ，３１ｂの先端側における断面積よりも広くしてもよい。また、電極端子３１ａ，３１ｂは、少なくとも電極端子３１ａ，３１ｂの基部において、ハニカム構造体２から離れるにつれて電極端子３１ａ，３１ｂの断面積が電極端子３１ａ，３１ｂの底面積（ハニカム構造体２側の端面（底面）の面積）から徐々に（連続的又は段階的に）減少する形状を有していてもよい。例えば電極端子３１ａ，３１ｂの基部を円錐台形状としてもよい。電極端子３１ａ，３１ｂの両端面の面積は互いに異なっていてもよい。 (3. Electrode terminal)
The sizes of the electrode terminals 31a and 31b are not limited, but for example, they are formed in a columnar shape having an area of both end faces of 10 to 800 mm 2 and a length of 10 to 100 mm in the direction in which the electrode terminals 31a and 31b stand up. can do. The cross-sectional area of the electrode terminals 31a and 31b on the plane orthogonal to the length direction 31L of the electrode terminals 31a and 31b may be uniform in the length direction 31L of the electrode terminals 31a and 31b, but in the length direction 31L. It may change. The cross-sectional area of the ends (bases) of the electrode terminals 31a and 31b on the honeycomb structure 2 side may be wider than the cross-sectional area on the tip side of the electrode terminals 31a and 31b. Further, in the electrode terminals 31a and 31b, at least at the base of the electrode terminals 31a and 31b, the cross-sectional area of the electrode terminals 31a and 31b becomes the bottom area of the electrode terminals 31a and 31b (on the honeycomb structure 2 side) as the distance from the honeycomb structure 2 increases. It may have a shape that gradually (continuously or stepwise) decreases from the end face (bottom surface) area). For example, the bases of the electrode terminals 31a and 31b may have a truncated cone shape. The areas of both end faces of the electrode terminals 31a and 31b may be different from each other.
　電極端子３１ａ，３１ｂの材質は、セラミックスまたはカーボンで構成されている。より好ましくは、セラミックスであってよい。電極端子３１ａ，３１ｂの材質がセラミックスであると、ハニカム構造体２への電気的な接続が可能となる。また、電極端子３１ａ，３１ｂの先端に金属端子がそれぞれ接合されていてもよい。セラミックスまたはカーボン製の電極端子と金属端子との接合は、かしめ加工、溶接、導電性接着剤等により行うことができる。金属端子の材質としては、鉄合金やニッケル合金等の導電性金属を採用することができる。 The material of the electrode terminals 31a and 31b is made of ceramics or carbon. More preferably, it may be ceramics. When the electrode terminals 31a and 31b are made of ceramic, electrical connection to the honeycomb structure 2 is possible. Further, metal terminals may be joined to the tips of the electrode terminals 31a and 31b, respectively. Joining of ceramic or carbon electrode terminals to metal terminals can be performed by caulking, welding, conductive adhesive, or the like. As the material of the metal terminal, a conductive metal such as an iron alloy or a nickel alloy can be adopted.
　電極端子３１ａ，３１ｂを構成するセラミックスとしては、限定的ではないが、炭化珪素（ＳｉＣ）が挙げられ、珪化タンタル（ＴａＳｉ2）及び珪化クロム（ＣｒＳｉ2）等の金属珪化物等の金属化合物が挙げられ、更には、一種以上の金属を含む複合材（サーメット）を挙げることができる。サーメットの具体例としては、金属珪素と炭化珪素の複合材、珪化タンタルや珪化クロム等の金属珪化物と金属珪素と炭化珪素の複合材、更には上記の一種又は二種以上の金属に熱膨張低減の観点から、アルミナ、ムライト、ジルコニア、コージェライト、窒化珪素及び窒化アルミ等の絶縁性セラミックスを一種又は二種以上添加した複合材が挙げられる。電極端子３１ａ，３１ｂを構成するカーボンとしては、カーボンを主成分とすることが好ましい。カーボンを主成分とするとは、電極端子３１ａ，３１ｂを構成する全成分に対してカーボンの含有量が５０質量％以上であることを意味する。カーボンの含有量は、より好ましくは、８０質量％以上であり、更により好ましくは９０質量％以上である。電極端子の材質は、電極層の材質と同質のものを用いてもよい。 Examples of the ceramics constituting the electrode terminals 31a and 31b include, but are not limited to, silicon carbide (SiC), and metal compounds such as metal silicates such as cermet tantalum (TaSi 2 ) and chromium silicate (CrSi 2). Further, a composite material (cermet) containing 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. As the carbon constituting the electrode terminals 31a and 31b, it is preferable that carbon is the main component. The fact that carbon is the main component means that the carbon content is 50% by mass or more with respect to all the components constituting the electrode terminals 31a and 31b. The carbon content is more preferably 80% by mass or more, and even more preferably 90% by mass or more. The material of the electrode terminal may be the same as the material of the electrode layer.
（４．金属電極及び電極端子の接続部）
　各電極端子３１ａ，３１ｂには、金属電極４ａ，４ｂがそれぞれ接続されている。図３に特に示すように、各電極端子３１ａ，３１ｂには、金属電極４ａ，４ｂと接続されるための接続部３２が設けられている。金属電極４ａ，４ｂは、例えば、キャップ状の形状を有している。換言すると、金属電極４ａ，４ｂは、円形の天板４０と、天板４０の外縁から天板４０の板厚方向に突出された周壁４１とを有している。金属電極４ａ，４ｂは電極端子３１ａ，３１ｂの上部に被せられている。本実施の形態の接続部３２は、電極端子３１ａ，３１ｂの上部に設けられた柱状部分と理解できる。 (4. Connection between metal electrode and electrode terminal)
Metal electrodes 4a and 4b are connected to the electrode terminals 31a and 31b, respectively. As particularly shown in FIG. 3, each of the electrode terminals 31a and 31b is provided with a connecting portion 32 for connecting to the metal electrodes 4a and 4b. The metal electrodes 4a and 4b have, for example, a cap-like shape. In other words, the metal electrodes 4a and 4b have a circular top plate 40 and a peripheral wall 41 protruding from the outer edge of the top plate 40 in the plate thickness direction of the top plate 40. The metal electrodes 4a and 4b are placed on the upper parts of the electrode terminals 31a and 31b. The connection portion 32 of the present embodiment can be understood as a columnar portion provided above the electrode terminals 31a and 31b.
　接続部３２の外面と金属電極４ａ，４ｂの内面とは全体的に互いに密着されていてもよいが、接続部３２の周方向に係る少なくとも一部において接続部３２の外面と金属電極４ａ，４ｂの内面との間に隙間３１Ｇが設けられていてもよい。金属電極４ａ，４ｂと電極端子３１ａ，３１ｂとの間には例えば導電性のろう材等からなる接合材料が設けられ、その導電性の接合材料により、金属電極４ａ，４ｂと電極端子３１ａ，３１ｂとを接合することができる。 The outer surface of the connecting portion 32 and the inner surface of the metal electrodes 4a and 4b may be in close contact with each other as a whole, but the outer surface of the connecting portion 32 and the metal electrodes 4a and 4b are at least partly related to the circumferential direction of the connecting portion 32. A gap 31G may be provided between the inner surface and the inner surface of the surface. A bonding material made of, for example, a conductive brazing material is provided between the metal electrodes 4a and 4b and the electrode terminals 31a and 31b. Depending on the conductive bonding material, the metal electrodes 4a and 4b and the electrode terminals 31a and 31b Can be joined with.
　本実施の形態の接続部３２の径は、電極端子３１ａ，３１ｂの長さ方向３１Ｌに一様である。しかしながら、電極端子３１ａ，３１ｂの長さ方向３１Ｌに沿って接続部３２の径が変化していてもよい。 The diameter of the connecting portion 32 of the present embodiment is uniform in the length direction 31L of the electrode terminals 31a and 31b. However, the diameter of the connecting portion 32 may change along the length direction 31L of the electrode terminals 31a and 31b.
　接続部３２の径は、３０ｍｍ以下である。径が３０ｍｍ以下であることで、電気加熱式担体１の車輛への搭載性が悪化することを避けることができる。接続部抵抗を低くするとの観点から、接続部３２の径は、５ｍｍ以上であることが好ましく、１０ｍｍ以上であることがより好ましく、１５ｍｍ以上であることが更により好ましい。後述のように、実施の形態では接続部３２の少なくとも一部の断面の形状が非円形（非真円形）とされる。接続部３２の径とは、電極端子３１ａ，３１ｂの長さ方向３１Ｌに直交する面３１Ｓにおける接続部３２の断面における最小包含円の直径である。最小包含円とは、断面を包含する最小の仮想円（真円）である。電極端子３１ａ，３１ｂの長さ方向３１Ｌに沿って接続部３２の径が変化している場合は、最も大きな値を接続部３２の径とする。 The diameter of the connecting portion 32 is 30 mm or less. When the diameter is 30 mm or less, it is possible to avoid deterioration of the mountability of the electrically heated carrier 1 on the vehicle. From the viewpoint of lowering the resistance of the connecting portion, the diameter of the connecting portion 32 is preferably 5 mm or more, more preferably 10 mm or more, and even more preferably 15 mm or more. As will be described later, in the embodiment, the shape of at least a part of the cross section of the connecting portion 32 is non-circular (non-circular). The diameter of the connecting portion 32 is the diameter of the minimum inclusion circle in the cross section of the connecting portion 32 on the surface 31S orthogonal to the length direction 31L of the electrode terminals 31a and 31b. The minimum inclusion circle is the smallest virtual circle (perfect circle) that includes a cross section. When the diameter of the connecting portion 32 changes along the length direction 31L of the electrode terminals 31a and 31b, the largest value is taken as the diameter of the connecting portion 32.
　ここで、電極端子３１ａ，３１ｂの長さ方向３１Ｌに直交する面３１Ｓにおける接続部３２の断面が円形（真円）であるとき、電極端子３１ａ，３１ｂの接続部３２の表面積が小さく電流密度が高くなるため、電気加熱式担体１の通電加熱時に所望する電流が流せないことがある。本実施の形態では、電極端子３１ａ，３１ｂの長さ方向３１Ｌに直交する面３１Ｓにおける接続部３２の少なくとも一部の断面の円形度が０．９５以下とされている。円形度が０．９５以下であることで、接続部３２の断面が円形である場合と比較して、接続部３２の表面積を大きくでき電流密度を下げることができる。これによって、より確実に電気加熱式担体１の通電加熱時に所望する電流を流すことができる。円形度は、０．９以下であることがより好ましい。電極端子３１ａ，３１ｂの製造容易性及び強度の観点から、接続部３２の断面の円形度は０．３以上であることが好ましく、０．５以上がより好ましい。 Here, when the cross section of the connecting portion 32 on the surface 31S orthogonal to the length direction 31L of the electrode terminals 31a and 31b is circular (perfect circle), the surface area of the connecting portion 32 of the electrode terminals 31a and 31b is small and the current density is high. Since it becomes high, a desired current may not flow when the electrically heated carrier 1 is energized and heated. In the present embodiment, the circularity of at least a part of the cross section of the connecting portion 32 on the surface 31S orthogonal to the length direction 31L of the electrode terminals 31a and 31b is 0.95 or less. When the circularity is 0.95 or less, the surface area of the connecting portion 32 can be increased and the current density can be reduced as compared with the case where the cross section of the connecting portion 32 is circular. As a result, a desired current can be more reliably passed when the electrically heated carrier 1 is energized and heated. The circularity is more preferably 0.9 or less. From the viewpoint of ease of manufacture and strength of the electrode terminals 31a and 31b, the circularity of the cross section of the connecting portion 32 is preferably 0.3 or more, and more preferably 0.5 or more.
　なお、円形度は、以下の式（１）により求めることができる。
　円形度＝４π×Ａ／Ｐ2・・・（１）
　式（１）において、Ａは電極端子３１ａ，３１ｂの長さ方向３１Ｌに直交する面３１Ｓにおける接続部３２の断面の面積であり、Ｐはその断面の周囲長である。仮に断面が真円であるとすると、円形度の値は１となる。断面の形状が複雑になるほど、円形度が低くなり、接続部３２の表面積が増える。 The circularity can be calculated by the following formula (1).
Circularity = 4π × A / P 2 ... (1)
In the formula (1), A is the area of the cross section of the connecting portion 32 on the surface 31S orthogonal to the length direction 31L of the electrode terminals 31a and 31b, and P is the peripheral length of the cross section. Assuming that the cross section is a perfect circle, the value of circularity is 1. The more complicated the shape of the cross section, the lower the circularity and the larger the surface area of the connecting portion 32.
　次に、図４～図６を参照しながら接続部３２の断面の具体例について説明する。図４は図３の接続部３２の第１態様を示す説明図であり、図５は図３の接続部３２の第２態様を示す説明図であり、図６は図３の接続部３２の第３態様を示す説明図である。 Next, a specific example of the cross section of the connecting portion 32 will be described with reference to FIGS. 4 to 6. 4 is an explanatory view showing a first aspect of the connection portion 32 of FIG. 3, FIG. 5 is an explanatory view showing a second aspect of the connection portion 32 of FIG. 3, and FIG. 6 is an explanatory view of the connection portion 32 of FIG. It is explanatory drawing which shows the 3rd aspect.
　接続部３２の断面の円形度を０．９５以下とする方法は任意である。接続部３２の断面の形状は、図４に示すように楕円とされてもよいし、図５に示すように切り欠き３２ａを有する円形状としてもよいし、図６に示すように凸部３２ｂを有する円形状としてもよいし、さらに複雑な形状であってもよい。図４～図６では、楕円形状、切り欠き３２ａ及び凸部３２ｂを理解しやすいように表している。接続部３２の断面の形状は、図４～図６の形状そのものに限定されない。 The method of setting the circularity of the cross section of the connecting portion 32 to 0.95 or less is arbitrary. The cross-sectional shape of the connecting portion 32 may be an ellipse as shown in FIG. 4, a circular shape having a notch 32a as shown in FIG. 5, or a convex portion 32b as shown in FIG. It may be a circular shape having the above, or it may be a more complicated shape. In FIGS. 4 to 6, the elliptical shape, the notch 32a, and the convex portion 32b are shown for easy understanding. The shape of the cross section of the connecting portion 32 is not limited to the shape itself of FIGS. 4 to 6.
　図４に示すように接続部３２の断面の形状が楕円とされるとき、短軸と長軸との比（短軸／長軸）を０．５以上とすることが好ましい。短軸と長軸との比を０．５以上とすることで、接続部３２の強度を保つことができる。ここでいう楕円とは、図４（ａ）に示すような数学的な楕円に限定されるものではなく、図４（ｂ）～（ｄ）に示すような角部を有しない凸状の曲線のみからなる形状も含む。楕円は、互いに直交する２つの対称軸のそれぞれを中心に線対称な形状と理解することもできる。真円は楕円に含まれない。長軸とは、互いに直交する２つの対称軸のうち、より長い対称軸を指し、短軸とは互いに直交する２つの対称軸のうち、より短い対称軸を指す。なお、短軸と長軸との比は、楕円であることから、１未満であり、好ましくは、０．９５以下である。 When the cross-sectional shape of the connecting portion 32 is elliptical as shown in FIG. 4, the ratio of the minor axis to the major axis (minor axis / major axis) is preferably 0.5 or more. By setting the ratio of the short axis to the long axis to 0.5 or more, the strength of the connecting portion 32 can be maintained. The ellipse referred to here is not limited to a mathematical ellipse as shown in FIG. 4 (a), and is a convex curve having no corners as shown in FIGS. 4 (b) to 4 (d). Also includes shapes consisting of ellipses. An ellipse can also be understood as an axisymmetric shape centered on each of two axes of symmetry that are orthogonal to each other. A perfect circle is not included in the ellipse. The major axis refers to the longer axis of symmetry among the two axes orthogonal to each other, and the minor axis refers to the shorter axis of symmetry among the two axes orthogonal to each other. Since the ratio of the minor axis to the major axis is elliptical, it is less than 1, preferably 0.95 or less.
　図５に示すように接続部３２の断面の形状が切り欠き３２ａを有する円形状とされるとき、限定はされないが、切り欠き３２ａを、三角形状（図５（ａ）参照）、矩形状（図５（ｂ）参照）、又は円形状（図５（ｃ）参照）とすることができる。図５の（ａ）～（ｃ）では接続部３２の断面に１つの切り欠き３２ａが設けられるように示しているが、切り欠き３２ａの数及び配置は任意である。同様に、切り欠き３２ａの大きさも任意である。 As shown in FIG. 5, when the shape of the cross section of the connecting portion 32 is a circular shape having the notch 32a, the notch 32a is formed into a triangular shape (see FIG. 5A) or a rectangular shape (see FIG. 5A), although it is not limited. It can be in the shape of a circle (see FIG. 5 (c)) or a circular shape (see FIG. 5 (c)). In FIGS. 5A to 5C, one notch 32a is provided in the cross section of the connecting portion 32, but the number and arrangement of the notches 32a are arbitrary. Similarly, the size of the notch 32a is arbitrary.
　図６に示すように接続部３２の断面の形状が凸部３２ｂを有する円形状とされるとき、限定はされないが、凸部３２ｂを、三角形状（図６（ａ）参照）、矩形状（図６（ｂ）参照）、又は円形状（図６（ｃ）参照）とすることができる。図６の（ａ）～（ｃ）では接続部３２の断面に１つの凸部３２ｂが設けられるように示しているが、凸部３２ｂの数及び配置は任意である。同様に、凸部３２ｂの大きさも任意である。 As shown in FIG. 6, when the cross-sectional shape of the connecting portion 32 is a circular shape having the convex portion 32b, the convex portion 32b is formed into a triangular shape (see FIG. 6A) or a rectangular shape (see FIG. 6A), although it is not limited. It can be in the shape of a circle (see FIG. 6 (c)) or a circular shape (see FIG. 6 (c)). In FIGS. 6A to 6C, one convex portion 32b is provided in the cross section of the connecting portion 32, but the number and arrangement of the convex portions 32b are arbitrary. Similarly, the size of the convex portion 32b is also arbitrary.
　図４～図６に示す各態様を組み合わせて実施してもよい。例えば、接続部３２の断面は、切り欠き３２ａ及び凸部３２ｂの少なくとも一方を有する楕円形であってもよい。接続部３２の断面の形状は、電極端子３１ａ，３１ｂの長さ方向３１Ｌに一様であってもよいし変化していてもよい。例えば、電極端子３１ａ，３１ｂの長さ方向３１Ｌに関して、接続部３２の全長にわたって切り欠き３２ａ又は凸部３２ｂが延在されていてもよいし、接続部３２の一部に切り欠き３２ａ又は凸部３２ｂが設けられていてもよい。 Each aspect shown in FIGS. 4 to 6 may be combined and carried out. For example, the cross section of the connecting portion 32 may be elliptical with at least one of the notch 32a and the convex portion 32b. The shape of the cross section of the connecting portion 32 may be uniform or changed in the length direction 31L of the electrode terminals 31a and 31b. For example, with respect to the length direction 31L of the electrode terminals 31a and 31b, the notch 32a or the convex portion 32b may extend over the entire length of the connecting portion 32, or the notch 32a or the convex portion may extend to a part of the connecting portion 32. 32b may be provided.
＜触媒体＞
　電気加熱式担体１に触媒を担持することにより、電気加熱式担体１を触媒体として使用することができる。複数のセル２１ａの流路には、例えば、自動車排気ガス等の流体を流すことができる。触媒としては、例えば、貴金属系触媒又はこれら以外の触媒が挙げられる。貴金属系触媒としては、白金（Ｐｔ）、パラジウム（Ｐｄ）、ロジウム（Ｒｈ）といった貴金属をアルミナ細孔表面に担持し、セリア、ジルコニア等の助触媒を含む三元触媒や酸化触媒、又は、アルカリ土類金属と白金を窒素酸化物（ＮＯx）の吸蔵成分として含むＮＯx吸蔵還元触媒（ＬＮＴ触媒）が例示される。貴金属を用いない触媒として、銅置換又は鉄置換ゼオライトを含むＮＯx選択還元触媒（ＳＣＲ触媒）等が例示される。また、これらの触媒からなる群から選択される２種以上の触媒を用いてもよい。なお、触媒の担持方法についても特に制限はなく、従来、ハニカム構造体に触媒を担持する担持方法に準じて行うことができる。 <Catalyst>
By supporting the catalyst on the electrically heated carrier 1, the electrically heated carrier 1 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 21a. 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.
＜電気加熱式担体の製造方法＞
　次に、本発明に係る電気加熱式担体を製造する方法について例示的に説明する。本発明の電気加熱式担体の製造方法は一実施形態において、電極端子付き未焼成ハニカム構造体を得る工程Ａ１と、電極端子付き未焼成ハニカム構造体を焼成して電極端子付きハニカム構造体を得る工程Ａ２とを含む。また、他の実施形態としては、電極層形成用ペースト、電極端子形成用ペーストを仮焼成後に、ハニカム構造体に貼り付けてもよい。また、カーボンで構成された電極端子については、カーボン製の電極端子をハニカム構造体に貼り付けてもよい。 <Manufacturing method of electrically heated carrier>
Next, a method for producing the electroheated carrier according to the present invention will be exemplified. In one embodiment of the method for producing an electrically heated carrier of the present invention, the step A1 for obtaining an unfired honeycomb structure with electrode terminals and the unfired honeycomb structure with electrode terminals are fired to obtain a honeycomb structure with electrode terminals. Includes step A2. Further, as another embodiment, the electrode layer forming paste and the electrode terminal forming paste may be attached to the honeycomb structure after calcination. Further, for the electrode terminals made of carbon, the electrode terminals made of carbon may be attached to the honeycomb structure.
　工程Ａ１は、ハニカム構造体の前駆体である柱状のハニカム成形体を作製し、ハニカム成形体の側面に電極層形成ペーストを塗布して、電極層形成ペースト付き未焼成ハニカム構造体を得た後、電極層形成ペースト上に電極端子を設けて電極端子付き未焼成ハニカム構造体を得る工程である。 In step A1, a columnar honeycomb molded body that is a precursor of the honeycomb structure is produced, and an electrode layer forming paste is applied to the side surface of the honeycomb molded body to obtain an unfired honeycomb structure with the electrode layer forming paste. This is a step of providing an electrode terminal on the electrode layer forming paste to obtain an unfired honeycomb structure with an electrode terminal.
　ハニカム成形体の作製としては、まず、ホウ酸と、Ｓｉ原子を含む導電性フィラーと、カオリンとを混合する。あるいは、アルカリ系原子を含むホウケイ酸塩と、Ｓｉ原子を含む導電性フィラーと、カオリンとを混合する。ホウケイ酸塩は、繊維状、粒子状などの形状を有してもよく、混合物の押し出し性が向上するため、繊維状であるのが好ましい。当該混合物において、電気抵抗率の温度依存性が小さいハニカム構造体２を得やすくするために、ホウ酸の質量比を、４以上８以下とするのが好ましい。ホウケイ酸塩に含まれるホウ素の含有量は、後述する焼成温度を高くすることで増加させることができる。ケイ酸塩にドープされるホウ素量を多くするほど、ハニカム構造体２の電気抵抗をより低下させることができる。 To prepare the honeycomb molded product, first, boric acid, a conductive filler containing Si atoms, and kaolin are mixed. Alternatively, a borosilicate containing an alkaline atom, a conductive filler containing a Si atom, and kaolin are mixed. The borosilicate may have a fibrous or particulate shape, and is preferably fibrous because it improves the extrudability of the mixture. In the mixture, the mass ratio of boric acid is preferably 4 or more and 8 or less in order to facilitate obtaining the honeycomb structure 2 having a small temperature dependence of electrical resistivity. The content of boron contained in the borosilicate can be increased by increasing the firing temperature described later. As the amount of boron doped in the silicate is increased, the electrical resistance of the honeycomb structure 2 can be further reduced.
　次に、当該混合物に、バインダ及び水を加える。バインダとしては、例えば、メチルセルロース、ヒドロキシプロピルメチルセルロース、ヒドロキシプロポキシルセルロース、ヒドロキシエチルセルロース、カルボキシメチルセルロース、ポリビニルアルコール等を挙げることができる。また、バインダの含有量は、例えば、２質量％程度とすることができる。 Next, add a binder and water to the mixture. Examples of the binder include methyl cellulose, hydroxypropyl methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol and the like. The binder content can be, for example, about 2% by mass.
　次に、得られた成形原料を混練して坏土を形成した後、坏土を押出成形してハニカム成形体を作製する。押出成形に際しては、所望の全体形状、セル形状、隔壁厚み、セル密度等を有する口金を用いることができる。次に、得られたハニカム成形体について、乾燥を行うことが好ましい。ハニカム成形体の中心軸方向長さが、所望の長さではない場合は、ハニカム成形体の両底部を切断して所望の長さとすることができる。乾燥後のハニカム成形体を柱状ハニカム乾燥体と呼ぶ。 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 columnar honeycomb dried body.
　次に、電極層を形成するための電極層形成ペーストを調合する。電極層形成ペーストは、炭化珪素及びシリコンを、質量比２０：８０で混合し、バインダ及び水と混合することで作製することができる。電極層形成原料に含まれる炭化珪素粉末として、平均粒子径が３～５０μｍの粉末を用いることが好ましい。炭化珪素粉末の平均粒子径が、３μｍ未満であると、界面が多くなり高抵抗となる傾向にある。また、炭化珪素粉末の平均粒子径が、５０μｍ超であると、低強度となり、耐熱衝撃性に劣る傾向にある。 Next, the electrode layer forming paste for forming the electrode layer is prepared. The electrode layer forming paste can be prepared by mixing silicon carbide and silicon at a mass ratio of 20:80 and mixing them with a binder and water. As the silicon carbide powder contained in the electrode layer forming raw material, it is preferable to use a powder having an average particle size of 3 to 50 μm. When the average particle size of the silicon carbide powder is less than 3 μm, the number of interfaces increases and the resistance tends to be high. Further, when the average particle size of the silicon carbide powder is more than 50 μm, the strength is low and the heat impact resistance tends to be inferior.
　次に、得られた電極層形成ペーストを、ハニカム成形体（典型的には柱状ハニカム乾燥体）の側面に塗布し、電極層形成ペースト付き未焼成ハニカム構造体を得る。電極層形成ペーストをハニカム成形体に塗布する方法については、公知のハニカム構造体の製造方法に準じて行うことができる。 Next, the obtained electrode layer forming paste is applied to the side surface of the honeycomb molded body (typically, the columnar honeycomb dried body) to obtain an unfired honeycomb structure with the electrode layer forming paste. 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.
　ハニカム構造体の製造方法の変更例として、工程Ａ１において、電極層形成ペーストを塗布する前に、ハニカム成形体を一旦焼成してもよい。すなわち、この変更例では、ハニカム成形体を焼成して柱状ハニカム焼成体を作製し、当該柱状ハニカム焼成体に、電極層形成ペーストを塗布する。 As an example of changing the manufacturing method of the 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 columnar honeycomb fired body, and the electrode layer forming paste is applied to the columnar honeycomb fired body.
　次に、電極端子を形成するための電極端子形成材料を調合する。電極端子形成材料は、電極端子の要求特性に応じて配合したセラミックス粉末に各種添加剤を適宜添加して混練することでできる。次に、調合・混錬した電極端子形成材料を、プレス成型にて所定形状に形成し、乾燥及び／又は焼成を行う。電極端子は乾燥時及び／又は焼成時の収縮により変形するので、乾燥後及び／又は焼成後に切断及び／又は研磨加工を行うことが好ましい。電極端子に切り欠き又は凸部を形成する方法としては、電極端子を形成する型に予め切り欠き又は凸部を設けておいてもよいし、乾燥及び／又は焼成後に研削加工を行ってもよい。ハニカム構造体上の電極層の表面から起立するように設ける方法については、電極層形成ペーストを用いることができる。 Next, the electrode terminal forming material for forming the electrode terminal is prepared. The electrode terminal forming material can be kneaded by appropriately adding various additives to the ceramic powder blended according to the required characteristics of the electrode terminals. Next, the prepared and kneaded electrode terminal forming material is formed into a predetermined shape by press molding, and dried and / or fired. Since the electrode terminals are deformed by shrinkage during drying and / or firing, it is preferable to perform cutting and / or polishing after drying and / or firing. As a method of forming a notch or a convex portion in the electrode terminal, the notch or the convex portion may be provided in advance in the mold for forming the electrode terminal, or grinding may be performed after drying and / or firing. .. As a method of providing the honeycomb structure so as to stand up from the surface of the electrode layer, an electrode layer forming paste can be used.
　工程Ａ２では、電極端子付き未焼成ハニカム構造体を焼成して、電極端子付きハニカム構造体を得る。焼成条件は、不活性ガス雰囲気下または大気雰囲気下、大気圧以下、焼成温度１１５０～１３５０℃、焼成時間０．１～５０時間とすることができる。なお、焼成雰囲気は、例えば、不活性ガス雰囲気、焼成時圧力は、常圧などとすることができる。ハニカム構造体２の電気抵抗を低下させるためには、酸化防止の観点から残存酸素を低減することが好ましく、焼成時の雰囲気内を１．０×１０-4Ｐａ以上の高真空にした後に不活性ガスをパージして焼成することが好ましい。不活性ガス雰囲気としては、Ｎ2ガス雰囲気、ヘリウムガス雰囲気、アルゴンガス雰囲気などが挙げられる。焼成を行う前に、電極端子形成ペースト付き未焼成ハニカム構造体を乾燥してもよい。また、焼成の前に、バインダ等を除去するため、脱脂を行ってもよい。このようにして、電極端子が電極層に電気的に接続された電気加熱式担体が得られる。 In step A2, the unfired honeycomb structure with electrode terminals is fired to obtain a honeycomb structure with electrode terminals. The firing conditions can be under an inert gas atmosphere or an atmospheric atmosphere, below atmospheric pressure, a firing temperature of 1150 to 1350 ° C., and a firing time of 0.1 to 50 hours. The firing atmosphere may be, for example, an inert gas atmosphere, and the firing pressure may be normal pressure. In order to reduce the electrical resistance of the honeycomb structure 2, it is preferable to reduce the residual oxygen from the viewpoint of preventing oxidation, and it is not possible after the atmosphere at the time of firing is set to a high vacuum of 1.0 × 10 -4 Pa or more. It is preferable to purge the active gas and fire it. Examples of the inert gas atmosphere include an N 2 gas atmosphere, a helium gas atmosphere, and an argon gas atmosphere. The unfired honeycomb structure with the electrode terminal forming paste may be dried before firing. Further, before firing, degreasing may be performed in order to remove the binder and the like. In this way, an electrically heated carrier in which the electrode terminals are electrically connected to the electrode layer is obtained.
＜排気ガス浄化装置＞
　次に、図７は、本発明の実施形態に係る排気ガス浄化装置を示す説明図である。上述した本発明の実施形態に係る電気加熱式担体１は、排気ガス浄化装置に用いることができる。当該排気ガス浄化装置は、電気加熱式担体１と、電気加熱式担体１の電極端子３１ａ，３１ｂと接続された金属電極４ａ，４ｂと、電気加熱式担体１を保持する金属製の缶体５とを有する。排気ガス浄化装置において、電気加熱式担体は、エンジンからの排気ガスを流すための排気ガス流路の途中に設置される。 <Exhaust gas purification device>
Next, FIG. 7 is an explanatory diagram showing an exhaust gas purification device according to an embodiment of the present invention. The electrically heated carrier 1 according to the embodiment of the present invention described above can be used in an exhaust gas purification device. The exhaust gas purifying device includes an electric heating type carrier 1, metal electrodes 4a and 4b connected to electrode terminals 31a and 31b of the electric heating type carrier 1, and a metal can body 5 holding the electric heating type carrier 1. And have. 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.
　１　　　　　　　電気加熱式担体
　２　　　　　　　ハニカム構造体
　２０　　　　　　外周壁
　２１　　　　　　隔壁
　２１ａ　　　　　セル
　３ａ，３ｂ　　　電極
　３０ａ，３０ｂ　電極層
　３１ａ，３１ｂ　電極端子
　３２　　　　　　接続部
　３２ａ　　　　　切り欠き
　３２ｂ　　　　　凸部
　４ａ，４ｂ　　　金属電極
　５　　　　　　　缶体 1 Electric heating type carrier 2 Honeycomb structure 20 Outer wall 21 Partition wall 21a Cell 3a, 3b Electrode 30a, 30b Electrode layer 31a, 31b Electrode terminal 32 Connection part 32a Notch 32b Convex part 4a, 4b Metal electrode 5 Can body

Claims (7)

  1. 　外周壁と、前記外周壁の内側に配設され、一方の端面から他方の端面まで貫通して流路を形成する複数のセルを区画形成する隔壁とを有する柱状のハニカム構造体と、
    　前記ハニカム構造体に電圧を印加するための柱状の電極端子と
    　を備え、
    　前記電極端子には、金属電極と接続されるための接続部が設けられており、
    　前記接続部の径が３０ｍｍ以下であり、
    　前記電極端子の長さ方向に直交する面における前記接続部の少なくとも一部の断面の円形度が０．９５以下である、
    　電気加熱式担体。     A columnar honeycomb structure having an outer peripheral wall and a partition wall arranged inside the outer peripheral wall and partitioning a plurality of cells forming a flow path from one end face to the other end face.
    A columnar electrode terminal for applying a voltage to the honeycomb structure is provided.
    The electrode terminal is provided with a connection portion for connecting to a metal electrode.
    The diameter of the connecting portion is 30 mm or less, and the diameter is 30 mm or less.
    The circularity of at least a part of the cross section of the connection portion on the plane orthogonal to the length direction of the electrode terminal is 0.95 or less.
    Electric heating type carrier.
  2. 　前記断面の形状が、楕円である、
    　請求項１に記載の電気加熱式担体。     The shape of the cross section is elliptical.
    The electrically heated carrier according to claim 1.
  3. 　前記断面の形状が、切り欠きを有する円形状である、
    　請求項１又は請求項２に記載の電気加熱式担体。     The shape of the cross section is a circular shape having a notch.
    The electroheated carrier according to claim 1 or 2.
  4. 　前記断面の形状が、凸部を有する円形状である、
    　請求項１から請求項３までのいずれか一項に記載の電気加熱式担体。     The shape of the cross section is a circular shape having a convex portion.
    The electrically heated carrier according to any one of claims 1 to 3.
  5. 　前記ハニカム構造体は、アルカリ系原子を含むホウケイ酸塩から構成されるマトリックスと、導電性フィラーから構成されるドメインと、を有する
    　請求項１から請求項４までのいずれか一項に記載の電気加熱式担体。     The electricity according to any one of claims 1 to 4, wherein the honeycomb structure has a matrix composed of a borosilicate containing an alkaline atom and a domain composed of a conductive filler. Heated carrier.
  6. 　前記外周壁の表面上に設けられた帯状の電極層をさらに備え、
    　前記電極端子が、前記電極層上に設けられている、
    　請求項１から請求項５までのいずれか一項に記載の電気加熱式担体。     A band-shaped electrode layer provided on the surface of the outer peripheral wall is further provided.
    The electrode terminal is provided on the electrode layer.
    The electrically heated carrier according to any one of claims 1 to 5.
  7. 　請求項１から請求項６までのいずれか一項に記載の電気加熱式担体と、
    　前記電気加熱式担体の電極端子と接続された金属電極と、
    　前記電気加熱式担体を保持する金属製の缶体と
    　を備える、
    　排気ガス浄化装置。     The electrically heated carrier according to any one of claims 1 to 6,
    A metal electrode connected to the electrode terminal of the electroheating carrier and
    A metal can body that holds the electroheated carrier.
    Exhaust gas purification device.
PCT/JP2020/037481 2020-03-04 2020-10-01 Electrically heated carrier and exhaust gas purification device WO2021176757A1 (en)

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Citations (6)

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JP2014105694A (en) * 2012-11-30 2014-06-09 Toyota Motor Corp Electrification heating type catalyst device and manufacturing method thereof
WO2019003984A1 (en) * 2017-06-30 2019-01-03 株式会社デンソー Electrical resistor, honeycomb structure and electrically heated catalyst device
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JP2019171229A (en) * 2018-03-26 2019-10-10 日本碍子株式会社 Electric heating type catalyst carrier

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JP2014062476A (en) * 2012-09-20 2014-04-10 Toyota Motor Corp Composite material, electrode film and manufacturing method thereof, electrode terminal and manufacturing method thereof, base material and manufacturing method thereof, and joint material and manufacturing method of base material in which division body is joined by joint material
JP2014105694A (en) * 2012-11-30 2014-06-09 Toyota Motor Corp Electrification heating type catalyst device and manufacturing method thereof
WO2019003984A1 (en) * 2017-06-30 2019-01-03 株式会社デンソー Electrical resistor, honeycomb structure and electrically heated catalyst device
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