JP7453032B2 - Exhaust gas purification device and electrically heated carrier with conductor - Google Patents

Description

The present invention relates to an exhaust gas purification device and an electrically heated carrier with a conductor.

In recent years, electrically heated catalysts (EHCs) have been proposed to improve the deterioration in exhaust gas purification performance immediately after engine startup. EHC, for example, is a system in which a metal electrode is connected to a columnar honeycomb structure made of conductive ceramics, and the honeycomb structure itself generates heat when energized, thereby raising the temperature to the activation temperature of the catalyst before starting the engine. It is.

2. Description of the Related Art Exhaust gas purification devices are known in which an EHC is provided on the upstream side of an exhaust gas flow path of an automobile or the like, and a honeycomb structure is provided on the downstream side. In the exhaust gas purification device, in order to flow current through the EHC, it is necessary to electrically connect the EHC to external wiring. As a connection method, Patent Document 1 discloses a method of passing a conductor through the surface or inside of a honeycomb structure on the downstream side and wiring it to an EHC on the upstream side. Further, Patent Document 2 discloses a method of wiring from the upstream side of the EHC to the EHC using a conductor.

Patent No. 6248952 Patent No. 5625796

In Patent Document 1, the conductor is passed through the surface or inside of the honeycomb structure on the downstream side and is wired to the EHC on the upstream side, but in such a configuration, the EHC and the downstream honeycomb structure are , because they are individually displaced due to vibration or thermal expansion, there is a risk that the wiring may be deformed and disconnected due to the displacement.

In Patent Document 2, a conductor is used for wiring from the upstream side of the EHC to the EHC, but in such a configuration, soot and water vapor may accumulate on the outer periphery of the EHC due to the pressure loss of the EHC on the upstream side. There is a risk that the EHC and the wiring may be short-circuited from the ends, causing local heat generation and damaging the honeycomb structure of the EHC.

The present invention was created in view of the above circumstances, and provides an exhaust gas purification device and a conductor that can satisfactorily suppress the breakage and short circuit of the conductor electrically connected to the electrically heated carrier. The object of the present invention is to provide an electrically heated carrier.

The above problem is solved by the present invention described below, and the present invention is specified as follows.
(1) An exhaust gas purification device having an exhaust gas flow path inside,
a columnar electrically heated carrier provided on the upstream side of the exhaust gas flow path;
a columnar honeycomb structure provided at a distance from the electrically heated carrier on the downstream side of the exhaust gas flow path;
a can-shaped housing provided to cover the outer peripheral surfaces of the electrically heated carrier and the columnar honeycomb structure;
a conductor electrically connected to the outer peripheral surface of the electrically heated carrier;
Equipped with
The housing has a through hole at a location corresponding to a position where the electrically heated carrier and the columnar honeycomb structure are separated,
The conductor has an extending portion extending from the outer circumferential surface of the electrically heated carrier to a position separated from the electrically heated carrier and the columnar honeycomb structure, and
The extending portion of the conductor connects with the electrical connection terminal when the electrical connection terminal for connection to an external power source is inserted from the outside of the housing through the through hole in the radial direction of the electrically heated carrier. Exhaust gas purification devices located where possible.
(2) A ceramic material having an outer circumferential wall and a partition wall disposed inside the outer circumferential wall and partitioning a plurality of cells penetrating from the first end face to the second end face to form a flow path. A columnar honeycomb structure part,
an electrode layer disposed on the surface of the outer peripheral wall of the columnar honeycomb structure;
an electrically heated carrier with
a conductor electrically connected to the electrode layer of the electrically heated carrier;
Equipped with
the electrical conductor has an extension extending axially outward from the second end surface of the electrically heated carrier;
An electrically heated carrier with a conductor, wherein at least a part of the extending portion of the electrically conductor is inclined from a second end surface of the electrically heated carrier toward the outside in a radial direction of the electrically heated carrier.

According to the present invention, it is possible to provide an exhaust gas purification device and an electrically heated carrier with a conductor that can effectively suppress breakage and short circuit of the conductor electrically connected to the electrically heated carrier. can.

FIG. 2 is a schematic cross-sectional view parallel to the extending direction of the cells of the electrically heated carrier of the exhaust gas purification device in Embodiment 1 of the present invention. 1 is a schematic external view of an electrically heated carrier in Embodiment 1 of the present invention. FIG. 2 is a schematic cross-sectional view perpendicular to the stretching direction of the cells of the electrically heated carrier in Embodiment 1 of the present invention. FIG. 3 is a schematic cross-sectional view parallel to the extending direction of the cells of the electrically heated carrier of the exhaust gas purification device in Embodiment 2 of the present invention. 5 is an enlarged view of the inclined portion of the conductor of the electrically heated carrier of the exhaust gas purification device shown in FIG. 4. FIG. FIG. 7 is a schematic cross-sectional view parallel to the extending direction of the cells of the electrically heated carrier of the exhaust gas purification device in Embodiment 3 of the present invention. FIG. 7 is an enlarged view of the expanded diameter portion of the housing of the exhaust gas purification device shown in FIG. 6;

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

<Embodiment 1>
(Exhaust gas purification device)
FIG. 1 is a schematic cross-sectional view parallel to the extending direction of the cells 18 of the electrically heated carrier 10 of the exhaust gas purification device 100 in Embodiment 1 of the present invention. The exhaust gas purification device 100 has an exhaust gas flow path inside, and includes a columnar electrically heated carrier 10 provided on the upstream side of the exhaust gas flow path, and a columnar electrically heated carrier 10 provided on the downstream side of the exhaust gas flow path. It includes a columnar honeycomb structure 21 provided apart from the electrically heated carrier 10, a housing 15, and a conductor 14.

(1. Electrically heated carrier)
FIG. 2 is a schematic external view of the electrically heated carrier 10 in Embodiment 1 of the present invention. FIG. 3 is a schematic cross-sectional view perpendicular to the stretching direction of the cells 18 of the electrically heated carrier 10 in Embodiment 1 of the present invention. The electrically heated carrier 10 includes an outer circumferential wall 12 and a partition wall 19 that is disposed inside the outer circumferential wall 12 and defines a plurality of cells 18 that penetrate from a first end surface to a second end surface to form a flow path. and electrode layers 13a and 13b disposed on the surface of the outer peripheral wall 12 of the columnar honeycomb structure 11.

(1-1. Columnar honeycomb structure part)
The outer shape of the columnar honeycomb structure 11 is not particularly limited as long as it is columnar; for example, it may be columnar with a circular bottom (cylindrical shape), columnar with an oval bottom, or polygonal with a bottom (quadrilateral, pentagon, hexagon, heptagon). , octagonal, etc.). Further, the size of the columnar honeycomb structure 11 is preferably such that the area of the bottom surface is 2000 to 20000 mm 2 , and 5000 to 15000 mm ² for the reason of increasing heat resistance (suppressing cracks from entering in the circumferential direction of the outer peripheral wall). ² is more preferable.

The columnar honeycomb structure section 11 is made of ceramics and has electrical conductivity. There is no particular restriction on the electrical resistivity of the ceramic, as long as the conductive columnar honeycomb structure 11 is energized and can generate heat by Joule heat, but it is preferably 0.1 to 200 Ωcm, and 1 to 200 Ωcm is preferable. More preferably, it is 10 to 100 Ωcm. In the present invention, the electrical resistivity of the columnar honeycomb structure 11 is a value measured at 400° C. using a four-terminal method.

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

When the columnar honeycomb structure 11 contains a silicon-silicon carbide composite material, the "mass of silicon carbide particles as aggregate" contained in the columnar honeycomb structure 11 and the mass of silicon carbide particles contained in the columnar honeycomb structure 11 It is preferable that the ratio of “mass of silicon as a bonding material” contained in the columnar honeycomb structure portion 11 to the total “mass of silicon as a bonding material” is 10 to 40% by mass, and 15 to 35% by mass. It is more preferable that it is mass %. When the content is 10% by mass or more, the strength of the columnar honeycomb structure portion 11 is sufficiently maintained. When the content is 40% by mass or less, it becomes easier to maintain the shape during firing.

Although there is no restriction on the shape of the cell 18 in a cross section perpendicular to the stretching direction, it is preferably quadrangular, hexagonal, octagonal, or a combination thereof. Among these, quadrilateral and hexagonal shapes are preferred. By configuring the cell shape in this way, the pressure loss when exhaust gas flows through the columnar honeycomb structure 11 is reduced, and the purification performance of the catalyst is improved. A rectangular shape is particularly preferable from the viewpoint of achieving both structural strength and heating uniformity.

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

The cell density of the columnar honeycomb structure 11 in a cross section perpendicular to the flow path direction of the cells 18 is preferably 40 to 150 cells/cm ² , more preferably 70 to 100 cells/cm ² . By setting the cell density within such a range, the purification performance of the catalyst can be improved while reducing the pressure loss when the exhaust gas flows. When the cell density is 40 cells/cm ² or more, a sufficient catalyst supporting area is ensured. When the cell density is 150 cells/cm ² or less, when the columnar honeycomb structure 11 is used as a catalyst carrier to support a catalyst, the pressure loss when exhaust gas flows 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 columnar honeycomb structure 11 excluding the outer peripheral wall 12 portion.

Providing the outer circumferential wall 12 of the columnar honeycomb structure 11 is useful from the viewpoint of ensuring the structural strength of the columnar honeycomb structure 11 and suppressing leakage of fluid flowing through the cells 18 from the outer circumferential wall 12. Specifically, the thickness of the outer peripheral wall 12 is preferably 0.1 mm or more, more preferably 0.15 mm or more, and even more preferably 0.2 mm or more. However, if the outer peripheral wall 12 is made too thick, the strength will be too high, and the strength balance with the partition wall 19 will be disrupted, resulting in a decrease in thermal shock resistance, so the thickness of the outer peripheral wall 12 is preferably 1.0 mm or less. , more preferably 0.7 mm or less, even more preferably 0.5 mm or less. Here, the thickness of the outer peripheral wall 12 is determined by observing the part of the outer peripheral wall 12 whose thickness is to be measured in a cross section perpendicular to the cell stretching direction. Defined as thickness.

The partition wall 19 can be porous. The porosity of the partition wall 19 is preferably 35 to 60%, more preferably 35 to 45%. When the porosity is 35% or more, deformation during firing can be more easily suppressed. When the porosity is 60% or less, the strength of the honeycomb structure is sufficiently maintained. The porosity is a value measured using a mercury porosimeter.

The average pore diameter of the partition walls 19 of the columnar honeycomb structure 11 is preferably 2 to 15 μm, more preferably 4 to 8 μm. When the average pore diameter is 2 μm or more, electrical resistivity is prevented from becoming too large. When the average pore diameter is 15 μm or less, electrical resistivity is prevented from becoming too small. The average pore diameter is a value measured using a mercury porosimeter.

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

Although there is no particular restriction on the formation area of the electrode layers 13a, 13b, from the viewpoint of increasing the uniform heat generation property of the columnar honeycomb structure 11, each electrode layer 13a, 13b is formed on the outer surface of the outer peripheral wall 12. It is preferable to extend in a band shape in the circumferential direction and in the cell stretching direction. Specifically, each electrode layer 13a, 13b extends over 80% or more of the length between the bottom surfaces of the columnar honeycomb structure 11, preferably over 90% of the length, and more preferably over the entire length. It is desirable that the current extend across the electrode layers 13a and 13b from the viewpoint that the current easily spreads in the axial direction of the electrode layers 13a and 13b.

The thickness of each electrode layer 13a, 13b is preferably 0.01 to 5 mm, more preferably 0.01 to 3 mm. By setting it within such a range, uniform heating properties can be improved. When the thickness of each electrode layer 13a, 13b is 0.01 mm or more, electrical resistance can be 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 electrode layer 13a, 13b is measured at the measurement point on the outer surface of each electrode layer 13a, 13b when the location of the electrode layer 13a, 13b 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 normal to the tangent at .

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

As the material of each electrode layer 13a, 13b, a composite material (cermet) of metal and conductive ceramics can be used. Examples of the metal include single metals such as Cr, Fe, Co, Ni, Si, or Ti, or alloys containing at least one metal selected from the group consisting of these metals. Examples of conductive ceramics include, but are not limited to, silicon carbide (SiC) and metal compounds such as metal silicides such as tantalum silicide (TaSi ₂ ) and chromium silicide (CrSi ₂ ). Specific examples of composites (cermets) of metals and conductive ceramics include composites of metal silicon and silicon carbide, composites of metal silicides such as tantalum silicide and chromium silicide, metal silicon and silicon carbide, and the above. Examples include composite materials in which one or more insulating ceramics such as alumina, mullite, zirconia, cordierite, silicon nitride, and aluminum nitride are added to one or more metals from the viewpoint of reducing thermal expansion. Among the various metals and conductive ceramics mentioned above, the material for the electrode layers 13a and 13b is a combination of metal silicides such as tantalum silicide and chromium silicide, and a composite material of metal silicon and silicon carbide, such as columnar honeycomb. This is preferable because it can be fired at the same time as the structural part, which contributes to simplifying the manufacturing process.

(2. Columnar honeycomb structure)
The columnar honeycomb structure 21 is provided at a distance from the electrically heated carrier 10 on the downstream side of the exhaust gas flow path of the exhaust gas purification device 100 . The columnar honeycomb structure 21 can be configured in the same manner as described above for the columnar honeycomb structure portion 11 of the electrically heated carrier 10 in terms of shape, material, size, etc. The columnar honeycomb structure 21 may be the same as or different from the columnar honeycomb structure 11 of the electrically heated carrier 10 in terms of shape, material, size, etc. If different, a columnar honeycomb structure having a shape, material, and size within a conventionally known range can be used. Note that a case where the size of the columnar honeycomb structure 21 is different from the columnar honeycomb structure portion 11 of the electrically heated carrier 10 is exemplified in Embodiment 3, which will be described later.

The distance between the columnar honeycomb structure 21 and the electrically heated carrier 10 is not particularly limited, but it depends on the installation space of the exhaust gas purification device 100, the size of the columnar honeycomb structure 21 and the electrically heated carrier 10, etc. Based on this, it can be designed as appropriate. For example, when the area of the bottom surface of the columnar honeycomb structure 11 and the columnar honeycomb structure 21 of the electrically heated carrier 10 is 2000 to 20000 mm ² and the length is 2 to 10 cm, the columnar honeycomb structure 21 is , the electrically heated carrier 10 can be spaced 2 to 10 cm apart.

By supporting catalysts on the electrically heated carrier 10 provided on the upstream side of the exhaust gas flow path of the exhaust gas purification device 100 and the columnar honeycomb structure 21 provided on the downstream side, electricity is generated. The heated carrier 10 and the columnar honeycomb structure 21 can be used as catalyst bodies. For example, fluid such as automobile exhaust gas can flow through the flow paths of the plurality of cells 18. Examples of the catalyst include noble metal catalysts and catalysts other than these. Examples of noble metal catalysts include three-way catalysts, oxidation catalysts, and alkali catalysts that support noble metals such as platinum (Pt), palladium (Pd), and rhodium (Rh) on the surface of alumina pores, and include promoters such as ceria and zirconia. An example is a NO _x storage reduction catalyst (LNT catalyst) containing an earth metal and platinum as nitrogen oxide (NO _x ) storage components. Examples of catalysts that do not use noble metals include NO _x selective reduction catalysts (SCR catalysts) containing copper-substituted or iron-substituted zeolites. Furthermore, two or more types of catalysts selected from the group consisting of these catalysts may be used. Note that there is no particular restriction on the method of supporting the catalyst, and it can be carried out in accordance with the conventional method of supporting the catalyst on a honeycomb structure.

(3. Housing)
The housing 15 is formed in a can shape and is provided so as to cover the outer peripheral surfaces of the electrically heated carrier 10 and the columnar honeycomb structure 21. As the housing 15, for example, a metal cylindrical member or the like can be used. The housing 15 has a through hole 17 at a location corresponding to a position where the electrically heated carrier 10 and the columnar honeycomb structure 21 are separated from each other. The part of the housing 15 corresponding to the separated position between the electrically heated carrier 10 and the columnar honeycomb structure 21 is the part shown by the dotted line d in FIG. A side view of the housing 15, which constitutes a space within the housing 15 that is formed at a distance, is shown. The through holes 17 may be formed anywhere as long as they correspond to the distance between the electrically heated carrier 10 and the columnar honeycomb structure 21 .

The shape of the through hole 17 is not particularly limited, and can be appropriately designed such as a circular shape or a rectangular shape. The size of the through hole 17 is not particularly limited as long as it is formed to a size that allows the electrical connection terminal 22 to be inserted into the through hole 17 from the outside of the housing 15, and can be designed as appropriate.

A holding mat 16 for holding the electrically heated carrier 10 and the columnar honeycomb structure 21 may be provided between the housing 15 and the electrically heated carrier 10 and between the housing 15 and the columnar honeycomb structure 21. The holding mat 16 can be made of a known material, such as ceramic fiber or glass fiber.

(4. Electric conductor)
The conductor 14 is electrically connected to the outer peripheral surface of the electrically heated carrier 10 . The conductor 14 has an extending portion 14 a extending from the outer circumferential surface of the electrically heated carrier 10 to a position where the electrically heated carrier 10 and the columnar honeycomb structure 21 are separated. The extending portion 14a of the conductor 14 is connected to the electrical connection terminal 22 when the electrical connection terminal 22 for connecting to an external power source is inserted from the outside of the housing 15 through the through hole 17 in the radial direction of the electrically heated carrier 10. It is located in a position where it can be connected. The tip of the extending portion 14a is preferably located adjacent to the through hole 17, as shown in FIG. 1, because it facilitates connection when the electrical connection terminal 22 is inserted. In the first embodiment, the extending portion 14a extends straight from the outer circumferential surface of the electrically heated carrier 10 to a position where the electrically heated carrier 10 and the columnar honeycomb structure 21 are separated from each other without being inclined.

As described above, the conductor 14 is not provided so as to protrude laterally from the outer circumferential surface of the electrically heated carrier 10 , but is connected to the electrically heated carrier 10 and the columnar honeycomb structure from the outer circumferential surface of the electrically heated carrier 10 . It is formed to extend to a position separated from the body 21. According to such a configuration, the conductor 14 can be favorably pressed in the direction of the electrically heated carrier 10 by the holding mat 16 or the like. Therefore, peeling and damage of the conductor 14 can be effectively suppressed. Further, the portion (junction point) where the conductor 14 is joined to the electrical connection terminal 22 can be freely designed. Specifically, for example, unlike this embodiment, the conductor provided so as to protrude laterally from the outer circumferential surface of the electrically heated carrier may be connected to an electrical connection terminal at the front or rear of the electrically heated carrier. If the points are arranged, the exhaust gas will come into direct contact with the joint points, which may cause problems in corrosion resistance. On the other hand, if the part (junction point) where the conductor 14 is joined to the electrical connection terminal 22 can be freely designed as in this embodiment, the holding mat can be wrapped around the entire surface, and such Corrosion resistance problems can be suppressed.

When a voltage is applied to the conductor 14 via the electrode layers 13a and 13b, the conductor 14 is energized and can generate heat in the columnar honeycomb structure 11 by Joule heat. Therefore, the electrically heated carrier 10 can also be suitably used as a heater. The applied voltage is preferably 12 to 900V, more preferably 64 to 600V, but the applied voltage can be changed as appropriate.

As the material of the conductor 14, single metals, alloys, etc. can be adopted, and from the viewpoint of corrosion resistance, electrical resistivity, and coefficient of linear expansion, the material is selected from the group consisting of Cr, Fe, Co, Ni, and Ti, for example. It is preferable to use an alloy containing at least one kind, and stainless steel and Fe--Ni alloy are more preferable. The shape and size of the conductor 14 are not particularly limited, and can be appropriately designed, such as a thin plate shape or a linear shape, depending on the size, current carrying performance, etc. of the electrically heated carrier 10.

As described above, the exhaust gas purification device 100 according to the first embodiment of the present invention has a through-hole 17 provided in a portion of the housing 15 corresponding to the separated position between the electrically heated carrier 10 and the columnar honeycomb structure 21. When the electrical connection terminal 22 is inserted in the radial direction of the electrically heated carrier 10, the extending portion 14a of the conductor 14 is arranged at a position where it can be connected to the electrical connection terminal 22. According to such a configuration, even if the electrically heated carrier 10 and the columnar honeycomb structure 21 are individually displaced due to vibration or thermal expansion of the exhaust gas purification device 100, the conductor 14 is not deformed by the displacement. Disconnection can be well suppressed.

Moreover, since the structure is not such that the conductor 14 is wired from the upstream side of the electrically heated carrier 10 to the electrically heated carrier 10, pressure loss of the electrically heated carrier 10 is suppressed from occurring on the upstream side. Therefore, it is possible to satisfactorily prevent soot and water vapor from accumulating on the outer periphery of the electrically heated carrier 10 and short-circuit between the electrically heated carrier 10 and the conductor 14 from the ends.

The exhaust gas purification device 100 in the first embodiment may include an electrical connection terminal 22 for connection to an external power source as a component. That is, in the configuration shown in FIG. 1, the exhaust gas purification device 100 has an electrical connection terminal 22 that is electrically connected to the tip of the extension portion 14a of the conductor 14 and protrudes from the through hole 17 of the housing 15. You can leave it there.

(5. Manufacturing method of exhaust gas purification device)
Next, a method for manufacturing the exhaust gas purification device 100 according to the present invention will be exemplified. In one embodiment, the method for manufacturing the electrically heated carrier 10 of the present invention includes step A1 of obtaining an unfired honeycomb structure with electrode layer forming paste, and firing the unfired honeycomb structure with electrode layer forming paste to form a columnar honeycomb structure. Step A2 of obtaining the electrically heated carrier by fixing the conductor to the columnar honeycomb structure by welding or thermal spraying, Step B1 of preparing the columnar honeycomb structure, and Step B1 of preparing the columnar honeycomb structure; and a step C1 of accommodating the honeycomb structure in a housing having a through hole.

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

Examples of the binder include methylcellulose, hydroxypropylmethylcellulose, hydroxypropoxylcellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinyl alcohol, and the like. Among these, it is preferable to use methylcellulose and hydroxypropoxylcellulose in combination. The content of the binder is preferably 2.0 to 10.0 parts by mass when the total mass of silicon carbide powder and metal silicon powder is 100 parts by mass.

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

As the surfactant, ethylene glycol, dextrin, fatty acid soap, polyalcohol, etc. can be used. These may be used alone or in combination of two or more. The content of the surfactant is preferably 0.1 to 2.0 parts by mass when the total mass of silicon carbide powder and metal silicon powder is 100 parts by mass.

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

Next, the obtained forming raw materials are kneaded to form a clay, and then the clay is extruded to produce a honeycomb molded body. For extrusion molding, a die having a desired overall shape, cell shape, partition wall thickness, cell density, etc. can be used. Next, it is preferable to dry the obtained honeycomb molded body. If the length of the honeycomb molded body in the central axis direction is not the desired length, it can be made to the desired length by cutting both bottoms of the honeycomb molded body. The honeycomb formed body after drying is called a dried honeycomb body. The formed honeycomb body or dried honeycomb body becomes a columnar honeycomb structure.

Moreover, by producing another columnar honeycomb structure, a columnar honeycomb structure to be installed on the downstream side is obtained (step B1). Note that the columnar honeycomb structure to be installed on the downstream side does not need to be formed of the same material, size, shape, etc. as the honeycomb structure on the upstream side, and can be designed as appropriate.

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

Next, the obtained electrode layer forming paste is applied to the side surface of a formed honeycomb body (typically a dried honeycomb body) to obtain an unfired honeycomb structure with electrode layer forming paste. The method of preparing the electrode layer forming paste and the method of applying the electrode layer forming paste to the honeycomb formed body can be carried out according to the known manufacturing method of honeycomb structure. In order to achieve low electrical resistivity, the content ratio of metal can be made higher than in the honeycomb structure, or the particle size of the metal particles can be made smaller.

As a modification of the method for manufacturing the columnar honeycomb structure, the honeycomb formed body may be fired once in step A1 before applying the electrode layer forming paste. That is, in this modification, a honeycomb formed body is fired to produce a honeycomb fired body, and an electrode layer forming paste is applied to the honeycomb fired body.

In step A2, the unfired honeycomb structure with electrode layer forming paste is fired to obtain a columnar honeycomb structure. Before firing, the unfired honeycomb structure with electrode layer forming paste may be dried. Further, before firing, degreasing may be performed to remove binder and the like. As for the firing conditions, it is preferable to heat at 1400 to 1500° C. for 1 to 20 hours in an inert atmosphere such as nitrogen or argon. Further, after firing, in order to improve durability, it is preferable to perform oxidation treatment at 1200 to 1350°C for 1 to 10 hours. The method of degreasing and firing is not particularly limited, and firing can be performed using an electric furnace, a gas furnace, or the like.

In step A3, an electric conductor made of a metal material or the like is fixed so as to extend beyond one end face from the outer peripheral surface of the columnar honeycomb structure to form an extended portion to obtain an electrically heated carrier. The fixing method is not particularly limited, and known laser welding, ultrasonic welding, thermal spraying, etc. can be used.

In step C1, the electrically heated carrier and the columnar honeycomb structure are housed in a housing having through holes. At this time, the electrically heated carrier and the columnar honeycomb structure are arranged so as to be separated from each other within the housing. Further, the through-hole of the housing is arranged at a position corresponding to a position where the electrically heated carrier and the columnar honeycomb structure are separated from each other. In this way, an exhaust gas purification device can be manufactured.

<Embodiment 2>
FIG. 4 is a schematic cross-sectional view parallel to the extending direction of the cells 18 of the electrically heated carrier 10 of the exhaust gas purification device 200 in Embodiment 2 of the present invention. The exhaust gas purification device 200 can have the same configuration as the exhaust gas purification device 100 in Embodiment 1, except that the configuration of the conductor 24 is different.

The conductor 24 of the exhaust gas purification device 200 has an extending portion 24a extending from the outer peripheral surface of the electrically heated carrier 10 to a position where the electrically heated carrier 10 and the columnar honeycomb structure 21 are separated. The conductor 24 has an inclined portion that extends from the second (downstream side) end surface of the electrically heated carrier 10 toward the outside in the radial direction of the electrically heated carrier 10 . In this way, at least a portion of the extending portion 24a of the conductor 24 is inclined from the downstream end surface of the electrically heated carrier 10 toward the outside in the radial direction of the electrically heated carrier 10. In the conductor 24 of the exhaust gas purification device 200, the extending portion 24a may constitute the inclined portion. According to such a configuration, as described above for the exhaust gas purification device 100 in Embodiment 1, deformation and disconnection of the conductor 24 due to vibration or thermal expansion of the exhaust gas purification device 200 can be effectively prevented. can be suppressed to Moreover, since the pressure loss of the electrically heated carrier 10 is suppressed from occurring on the upstream side, soot and water vapor are deposited on the outer circumference of the electrically heated carrier 10, and the end portions of the electrically heated carrier 10 and the conductor 24 are It is possible to effectively prevent short circuits from occurring. Further, since the conductor 24 is inclined radially outward of the electrically heated carrier 10 from the downstream end face of the electrically heated carrier 10, the columnar honeycomb structure portion 11 of the electrically heated carrier 10 on the upstream side is The passed soot and water vapor are deposited in front of the columnar honeycomb structure 21 on the downstream side without being directly received by the electrical connection terminals 22. Here, even if soot or water vapor is deposited in front of the columnar honeycomb structure 21 on the downstream side, there is a low possibility that it will be deposited on the end face of the electrically heated carrier 10. Therefore, the insulation between the electrically heated carrier 10 and the columnar honeycomb structure 21 is improved.

As the material of the conductor 24 of the exhaust gas purification device 200, the same material as the conductor 14 of the exhaust gas purification device 100 in the first embodiment can be used.

FIG. 5 shows an enlarged view of the inclined portion of the conductor 24 of the electrically heated carrier 20 of the exhaust gas purification device 200. Although the inclination angle θ1 of the inclination portion is not particularly limited, it is preferably 30 degrees or more since this is effective in suppressing the accumulation of soot and water vapor. Further, since the effect of stress relaxation due to vibration can be obtained, it is preferable that the angle is 60 degrees or less. More preferably, the inclination angle θ1 of the inclined portion is 30 to 60 degrees.

<Embodiment 3>
FIG. 6 is a schematic cross-sectional view parallel to the extending direction of the cells 18 of the electrically heated carrier 10 of the exhaust gas purification device 300 in Embodiment 3 of the present invention. The exhaust gas purification device 300 can have the same configuration as the exhaust gas purification device 100 in Embodiment 1, except that the configurations of the columnar honeycomb structure 31, the conductor 34, and the housing 35 are different.

The diameter of the columnar honeycomb structure 31 is larger than the diameter of the electrically heated carrier 10. Although not particularly limited, the diameter of the columnar honeycomb structure 31 can be formed to be 1.1 to 2 times the diameter of the electrically heated carrier 10. The columnar honeycomb structure 31 of the exhaust gas purification device 300 has the same configuration as the columnar honeycomb structure 21 of the exhaust gas purification device 100 in Embodiment 1, except that it is formed larger in diameter than the electrically heated carrier 10. be able to.

The conductor 34 has an extending portion 34a extending from the outer circumferential surface of the electrically heated carrier 10 to a position where the electrically heated carrier 10 and the columnar honeycomb structure 31 are separated. The conductor 34 has an inclined portion 34 b that extends from the second (downstream side) end surface of the electrically heated carrier 10 toward the outside in the radial direction of the electrically heated carrier 10 . In this embodiment, a portion of the extending portion 34a of the conductor 34 in the distal direction constitutes the inclined portion 34b. The inclination angle of the inclination part 34b is not particularly limited, but can be appropriately designed depending on the length of the extension part 34a, the position of the through hole 37 of the housing 35, and the inclination angle θ2 of the enlarged diameter portion of the housing 35.

The housing 35 has a can shape and is provided so as to cover the outer peripheral surfaces of the electrically heated carrier 10 and the columnar honeycomb structure 31. The diameter of the housing 35 increases toward the downstream side of the exhaust gas flow path at a portion corresponding to the electrically heated carrier 10 and the columnar honeycomb structure 31. According to such a configuration, as described above for the exhaust gas purification device 100 in Embodiment 1, deformation and disconnection of the conductor 34 due to vibration or thermal expansion of the exhaust gas purification device 300 can be effectively prevented. can be suppressed to Moreover, since the pressure loss of the electrically heated carrier 10 is suppressed from occurring on the upstream side, soot and water vapor are deposited on the outer periphery of the electrically heated carrier 10, and the end portion of the electrically heated carrier 10 and the conductor 34 are It is possible to effectively prevent short circuits from occurring. In addition, since the portion of the housing 35 corresponding to the electrically heated carrier 10 and the columnar honeycomb structure 31 increases in diameter toward the downstream side of the exhaust gas flow path, the electrically heated The soot and water vapor that have passed through the columnar honeycomb structure 11 of the carrier 10 are deposited in front of the columnar honeycomb structure 31 on the downstream side without being directly received by the electrical connection terminals 22. Here, even if soot or water vapor is deposited in front of the columnar honeycomb structure 31 on the downstream side, there is a low possibility that it will be deposited on the end face of the electrically heated carrier 10. Therefore, the insulation between the electrically heated carrier 10 and the columnar honeycomb structure 31 is improved. Furthermore, since the distance between the downstream columnar honeycomb structure 31 and the electrical connection terminal 22 can be increased, the insulation between the columnar honeycomb structure 31 and the electrical connection terminal 22 is increased.

As the material of the housing 35 of the exhaust gas purification device 300, the same material as the housing 15 of the exhaust gas purification device 100 in the first embodiment can be used.

FIG. 7 shows an enlarged view of the enlarged diameter portion of the housing 35 of the exhaust gas purification device 300. Although the inclination angle θ2 of the enlarged diameter portion of the housing 35 is not particularly limited, it is preferably 30 degrees or more, since this is effective in suppressing the accumulation of soot and water vapor. Further, since the effect of stress relaxation due to vibration can be obtained, it is preferable that the angle is 60 degrees or less. More preferably, the inclination angle θ2 of the enlarged diameter portion of the housing 35 is 30 to 60 degrees.

10 Electrically heated carrier 11 Columnar honeycomb structures 21, 31 Columnar honeycomb structures 12 Outer peripheral walls 13a, 13b Electrode layers 14, 24, 34 Conductor 14a Extended portion 24a Extended portion (slanted portion)
34a Extension part 34b Slanted part 15, 35 Housing 16 Holding mat 17, 37 Through hole 18 Cell 19 Partition wall 22 Electrical connection terminal 100, 200, 300 Exhaust gas purification device

Claims (6)

An exhaust gas purification device having an exhaust gas flow path inside,
a columnar electrically heated carrier provided on the upstream side of the exhaust gas flow path;
a columnar honeycomb structure provided at a distance from the electrically heated carrier on the downstream side of the exhaust gas flow path;
a can-shaped housing provided to cover the outer peripheral surfaces of the electrically heated carrier and the columnar honeycomb structure;
a conductor electrically connected to the outer peripheral surface of the electrically heated carrier;
Equipped with
The housing has a through hole at a location corresponding to a position where the electrically heated carrier and the columnar honeycomb structure are separated,
The conductor has an extending portion extending from the outer circumferential surface of the electrically heated carrier to a position separated from the electrically heated carrier and the columnar honeycomb structure, and
The extending portion of the conductor connects with the electrical connection terminal when the electrical connection terminal for connection to an external power source is inserted from the outside of the housing through the through hole in the radial direction of the electrically heated carrier. It is placed in a possible position,
An exhaust gas purification device, wherein at least a portion of the extending portion of the conductor is inclined from a downstream end face of the electrically heating carrier toward the outside in a radial direction of the electrically heating carrier. The diameter of the columnar honeycomb structure is larger than the diameter of the electrically heated carrier,
The exhaust gas purification according to claim 1, wherein a portion of the housing that corresponds between the electrically heated carrier and the columnar honeycomb structure has a diameter that increases toward the downstream side of the exhaust gas flow path. Device. The exhaust gas purification device has an electrical connection terminal for connecting to an external power source,
The exhaust gas purification device according to claim 1 or 2, wherein the electrical connection terminal is connected to the extending portion of the conductor from the outside of the housing via the through hole. A claim further comprising a holding mat provided between the housing and the electrically heated carrier and between the housing and the columnar honeycomb structure to hold the electrically heated carrier and the columnar honeycomb structure. The exhaust gas purification device according to any one of items 1 to 3. The electrically heated carrier is
A ceramic columnar honeycomb structure having an outer peripheral wall and a partition wall disposed inside the outer peripheral wall and partitioning a plurality of cells penetrating from a first end face to a second end face to form a flow path. Department and
an electrode layer disposed on the surface of the outer peripheral wall of the columnar honeycomb structure;
Equipped with
The exhaust gas purification device according to any one of claims 1 to 4, wherein the conductor is electrically connected to the electrode layer of the electrically heated carrier. An electrode layer disposed on the surface of the outer peripheral wall of the columnar honeycomb structure of the electrically heated carrier faces the surface of the outer peripheral wall of the columnar honeycomb structure with the central axis of the columnar honeycomb structure interposed therebetween. The exhaust gas purification device according to claim 5, wherein the exhaust gas purification device is a pair of electrode layers arranged as shown in FIG.