WO2021176757A1 - Support chauffé électriquement et dispositif d'épuration de gaz d'échappement - Google Patents

Support chauffé électriquement et dispositif d'épuration de gaz d'échappement 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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English (en)
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/ja
Publication of WO2021176757A1 publication Critical patent/WO2021176757A1/fr

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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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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Catalysts (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)

Abstract

L'invention concerne un support chauffé électriquement (1) qui est pourvu : d'une structure en nid d'abeilles en colonne (2) ayant une paroi circonférentielle externe (20) et des parois de séparation (21), qui sont disposées sur l'intérieur de la paroi circonférentielle externe (20), et qui délimitent une pluralité de cellules (21a) qui pénètrent d'une surface d'extrémité à l'autre surface d'extrémité, et forment un passage d'écoulement ; et des bornes d'électrode en colonne (31a et 31b) pour appliquer une tension à la structure en nid d'abeilles. Les bornes d'électrode (31a et 31b) sont pourvues d'une partie de connexion destinée à être connectée respectivement aux électrodes métalliques (4a et 4b). Le diamètre des parties de liaison est inférieur ou égal à 30 mm, et la circularité d'une section transversale d'au moins une partie des parties de connexion dans un plan orthogonal à la direction longitudinale des bornes d'électrode est de 0,95 ou moins.
PCT/JP2020/037481 2020-03-04 2020-10-01 Support chauffé électriquement et dispositif d'épuration de gaz d'échappement WO2021176757A1 (fr)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014062476A (ja) * 2012-09-20 2014-04-10 Toyota Motor Corp 複合材料、電極膜とその製造方法、電極端子とその製造方法、基材とその製造方法、および、接合材と接合材によって分割体が接合されてなる基材の製造方法
JP2014105694A (ja) * 2012-11-30 2014-06-09 Toyota Motor Corp 通電加熱式触媒装置及びその製造方法
WO2019003984A1 (fr) * 2017-06-30 2019-01-03 株式会社デンソー Résistance électrique, structure en nid d'abeilles et dispositif catalyseur chauffé électriquement
WO2019065381A1 (fr) * 2017-09-29 2019-04-04 株式会社デンソー Catalyseur chauffé électriquement
WO2019065378A1 (fr) * 2017-09-29 2019-04-04 株式会社デンソー Catalyseur chauffé électriquement
JP2019171229A (ja) * 2018-03-26 2019-10-10 日本碍子株式会社 電気加熱型触媒用担体

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014062476A (ja) * 2012-09-20 2014-04-10 Toyota Motor Corp 複合材料、電極膜とその製造方法、電極端子とその製造方法、基材とその製造方法、および、接合材と接合材によって分割体が接合されてなる基材の製造方法
JP2014105694A (ja) * 2012-11-30 2014-06-09 Toyota Motor Corp 通電加熱式触媒装置及びその製造方法
WO2019003984A1 (fr) * 2017-06-30 2019-01-03 株式会社デンソー Résistance électrique, structure en nid d'abeilles et dispositif catalyseur chauffé électriquement
WO2019065381A1 (fr) * 2017-09-29 2019-04-04 株式会社デンソー Catalyseur chauffé électriquement
WO2019065378A1 (fr) * 2017-09-29 2019-04-04 株式会社デンソー Catalyseur chauffé électriquement
JP2019171229A (ja) * 2018-03-26 2019-10-10 日本碍子株式会社 電気加熱型触媒用担体

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