阅读说明：本技术 蜂窝结构体及废气净化装置 (Honeycomb structure and exhaust gas purifying device ) 是由 木俣贵文 宫入由纪夫 桝田昌明 细田和也 于 2020-02-12 设计创作，主要内容包括：一种蜂窝结构体,其是柱状的蜂窝结构体,具有外周壁和多孔质的隔壁,该隔壁配设于外周壁的内侧,且区划形成从一个端面贯通至另一个端面而形成流路的多个隔室,其中,在隔室内的隔壁的表面具有平均细孔径小于隔壁的平均细孔径的捕集层,在隔壁的表面与捕集层之间及捕集层上这两者中的一者或两者具备居里点为700℃以上的磁性体粒子。(A honeycomb structure which is a columnar honeycomb structure and has an outer peripheral wall and porous partition walls which are disposed inside the outer peripheral wall and partition a plurality of cells which form flow paths penetrating from one end face to the other end face, wherein the partition walls in the cells have a trapping layer having an average pore diameter smaller than that of the partition walls on the surface thereof, and magnetic particles having a Curie point of 700 ℃ or higher are provided between the surfaces of the partition walls and the trapping layer and/or on the trapping layer.)

1. A honeycomb structure body, which is a columnar honeycomb structure body, comprising:

an outer peripheral wall; and

a porous partition wall which is disposed inside the outer peripheral wall and partitions the outer peripheral wall to form a plurality of compartments, the plurality of compartments penetrating from one end surface to the other end surface to form flow paths,

the honeycomb structure is characterized in that,

the surfaces of the partition walls in the compartments are provided with a trap layer having an average pore diameter smaller than that of the partition walls,

magnetic particles having a Curie point of 700 ℃ or higher are provided between the surfaces of the partition walls and the trapping layer or on the trapping layer.

2. The honeycomb structure according to claim 1,

the average particle diameter D50 on the volume basis of the magnetic particles is 10 to 3000 μm.

3. The honeycomb structure according to claim 1 or 2,

the magnetic particles contain at least one element selected from the group consisting of Fe, Co, and Ni.

4. The honeycomb structure according to any one of claims 1 to 3,

the surfaces of the magnetic particles are covered with a protective layer.

5. The honeycomb structure according to any one of claims 1 to 4,

the trap layer includes a compound containing an oxide of at least one or two or more elements selected from the group consisting of Si, Al, Mg, and Ti.

6. The honeycomb structure according to any one of claims 1 to 5,

the porosity of the trapping layer is 40-80%.

7. The honeycomb structure according to any one of claims 1 to 6,

the average pore diameter of the trapping layer is 1-10 mu m.

8. The honeycomb structure according to any one of claims 1 to 7,

the thickness of the trapping layer is 10-80 μm.

9. The honeycomb structure according to any one of claims 1 to 8,

the thermal conductivity of the trap layer is lower than that of the porous partition walls.

10. The honeycomb structure according to any one of claims 1 to 9,

the separator further includes, between a surface of the partition wall in the compartment and the trap layer: a thermal insulation layer having a thermal conductivity lower than that of the trap layer.

11. The honeycomb structure according to any one of claims 1 to 9,

the separator further includes, between a surface of the partition wall in the compartment and the trap layer: a heat insulating layer having a thermal conductivity lower than that of the partition wall.

12. The honeycomb structure according to claim 10 or 11,

the porosity of the heat-insulating layer is higher than that of the trapping layer and is 60-98%.

13. The honeycomb structure according to any one of claims 10 to 12,

the average pore diameter of the heat insulation layer is smaller than that of the partition wall and is 0.005-1 μm.

14. The honeycomb structure according to any one of claims 1 to 13,

the partition wall and the outer peripheral wall are made of a ceramic material.

15. The honeycomb structure according to claim 14,

the ceramic material includes a compound containing at least one or two or more elements selected from the group consisting of Si, Al, and Mg.

16. The honeycomb structure according to any one of claims 1 to 15,

the compartment comprises:

a plurality of cells a having an opening on the one end surface side and a hole sealing portion on the other end surface; and

and a plurality of cells B arranged alternately with the cells A, respectively, the other end surface side being open and having a hole sealing portion on the one end surface.

17. An exhaust gas purification apparatus, comprising:

the honeycomb structure according to any one of claims 1 to 16;

a coil wire spirally wound around an outer periphery of the honeycomb structure; and

and a metal pipe that houses the honeycomb structure and the coil wiring.

Technical Field

The present invention relates to a honeycomb structure and an exhaust gas purifying apparatus. In particular, the present invention relates to a honeycomb structure and an exhaust gas purifying apparatus that have good combustion efficiency in which carbon particles and the like are burned by induction heating and that suppress an increase in pressure loss.

Background

Reducing harmful components (HC, NO) in automobile exhaust_xCO), however, the harmful components currently discharged are discharged during a period in which the catalytic temperature immediately after the engine start is low and the activity is insufficient. As a countermeasure, patent document 1 discloses a technique in which magnetic wires are inserted into some cells of a cordierite honeycomb widely used as a catalyst carrier honeycomb, a current is passed through a coil on the outer periphery of the honeycomb, and the temperature of the wires is raised by induction heating. According to this technique, the honeycomb is heated by induction heating to raise the temperature of the honeycomb, thereby catalyzing the reactionThe agent is supported on the honeycomb itself to maintain catalytic activity, or the gas flowing through the heating honeycomb is heated to heat the catalyst honeycomb located at the subsequent stage.

Exhaust gas carbon particles from diesel engines and gasoline engines also have an effect on human health, and therefore, the reduction demand is high. As a countermeasure, patent document 2 discloses a technique of using a wall-flow type filter having a honeycomb structure and alternately provided with plugged portions, and providing a trapping layer for trapping particulate matter on the surfaces of the partition walls of the honeycomb structure filter.

The carbon particulates (soot) trapped by the filter are burned and removed by raising the temperature of the exhaust gas. However, if the time taken for the combustion removal is long, there arises a problem that the fuel consumption required for raising the temperature of the exhaust gas is increased. As a countermeasure, patent document 3 discloses a technique of dispersing and disposing magnetic fine particles on the surfaces of partition walls of a filter and heating the filter by electromagnetic induction heating.

Documents of the prior art

Patent document

Patent document 1 U.S. patent application publication No. 2017/0022868

Patent document 2, Japanese patent laid-open publication No. 2016-175045

Patent document 3 International publication No. 2016/021186

Disclosure of Invention

However, the inventors of the present invention found, as a result of their studies: when the technique disclosed in patent document 1 is applied to a catalyst carrier honeycomb or a honeycomb structure filter, the heating efficiency increases as the number of cells into which wires are inserted increases, but the number of cells that can be used as gas flow paths decreases, and the fluid flow path area decreases, thereby causing a significant increase in pressure loss.

In the technique described in patent document 2 or 3, the carbon particulates trapped by the honeycomb filter may enter the honeycomb substrate from the surfaces of the partition walls, which may deteriorate the combustion efficiency of the carbon particulates and increase the pressure loss of the filter.

The subject of the invention is: in view of the above, a honeycomb structure and an exhaust gas purifying apparatus are provided in which combustion efficiency is improved by burning carbon particulates and the like by induction heating, and an increase in pressure loss is suppressed.

The present inventors have conducted intensive studies and, as a result, have found that the above problems can be solved by adopting a configuration in which: a honeycomb structure having a trapping layer with an average pore diameter smaller than that of a partition wall on the surface of the partition wall in a cell to be a fluid flow path, wherein magnetic particles with a Curie point of 700 ℃ or higher are provided on one or both of the surfaces of the partition wall, the space between the trapping layer and the trapping layer, and the surface on the trapping layer. Namely, the present invention is determined as follows.

(1) A honeycomb structure body, which is a columnar honeycomb structure body, comprising:

an outer peripheral wall; and

a porous partition wall which is disposed inside the outer peripheral wall and partitions the outer peripheral wall to form a plurality of compartments, the plurality of compartments penetrating from one end surface to the other end surface to form flow paths,

the honeycomb structure is characterized in that,

the surfaces of the partition walls in the compartments are provided with a trap layer having an average pore diameter smaller than that of the partition walls,

magnetic particles having a Curie point of 700 ℃ or higher are provided between the surfaces of the partition walls and the trapping layer or on the trapping layer.

(2) An exhaust gas purification apparatus, comprising:

(1) the honeycomb structure of (3);

a coil wire spirally wound around an outer periphery of the honeycomb structure; and

and a metal pipe that houses the honeycomb structure and the coil wiring.

Effects of the invention

According to the present invention, it is possible to provide a honeycomb structure and an exhaust gas purifying apparatus that have good combustion efficiency in which carbon particles and the like are burned by induction heating, and in which an increase in pressure loss is suppressed.

Drawings

Fig. 1 is a perspective view schematically showing a honeycomb structure according to an embodiment of the present invention.

In fig. 2, (a), (b), and (c) are cross-sectional views schematically showing cross-sections parallel to the extending direction of the cells in the cells and the partition walls of the honeycomb structure according to the embodiment of the present invention, respectively.

In fig. 3, (a), (b), and (c) are partially enlarged views of the vicinity of the surface of the partition in the sectional views of fig. 2(a), (b), and (c), respectively.

Fig. 4 is a cross-sectional view schematically showing cells and partitions of a honeycomb structure having a heat insulating layer according to an embodiment of the present invention, the cross-section being parallel to the direction in which the cells extend.

Fig. 5 is a perspective view schematically showing a honeycomb structure having plugged portions according to an embodiment of the present invention.

Fig. 6 is a cross-sectional view schematically showing a cross section parallel to the cell extending direction of the honeycomb structure having plugged portions according to the embodiment of the present invention.

Fig. 7 is a schematic view of an exhaust gas flow path of an exhaust gas purifying apparatus incorporating a honeycomb structure.

Detailed Description

The embodiments of the honeycomb structure of the present invention will be described below with reference to the drawings, but the present invention is not limited to the description, and various changes, modifications, and improvements can be made based on the knowledge of those skilled in the art without departing from the scope of the present invention.

< 1. Honeycomb Structure

Fig. 1 is a perspective view schematically showing a honeycomb structure 1 according to an embodiment of the present invention. The honeycomb structure 1 shown in the figure has a columnar shape and has an outer peripheral wall 11 located at the outermost periphery. The honeycomb structure 1 shown in the drawings has porous cell walls 12, the cell walls 12 are disposed inside the outer peripheral wall 11 and partition a plurality of cells 15, and the plurality of cells 15 penetrate from one end surface 13 to the other end surface 14 to form flow paths.

The material of the cell walls 12 and the outer peripheral wall 11 of the honeycomb structure 1 is not particularly limited, and is usually formed of a ceramic material because it is necessary to be a porous body having a large number of pores. The ceramic material may be a compound containing at least one or two or more elements selected from the group consisting of Si, Al, and Mg. Examples thereof include: SiO 2₂、Al₂O₃MgO, cordierite (2 MgO.2SiO)₂·5SiO₂) Silicon carbide (SiC), aluminum titanate (Al)₂O₃·TiO₂) Silicon nitride (Si)₃N₄) Mullite (3 Al)₂O₃·2SiO₂) Alumina (Al)₂O₃) Silicon-silicon carbide-based composite materials and silicon carbide-cordierite-based composite materials. Particularly, a sintered body containing cordierite as a main component (50 mass% or more of cordierite) is preferable. In the present specification, "silicon carbide-based" means: the honeycomb structure 1 contains silicon carbide in an amount of 50 mass% or more of the entire honeycomb structure 1. The honeycomb structure 1 mainly composed of a silicon-silicon carbide composite material means that: the honeycomb structure 1 contains a silicon-silicon carbide composite material (total mass) in an amount of 90 mass% or more of the entire honeycomb structure 1. Here, the silicon-silicon carbide composite material contains: the silicon carbide particles as the aggregate and the silicon as the binder for binding the silicon carbide particles are preferably bound together by the silicon so that pores are formed between the silicon carbide particles. In addition, the honeycomb structure 1 mainly containing silicon carbide means: the honeycomb structure 1 contains silicon carbide (total mass) in an amount of 90 mass% or more of the entire honeycomb structure 1.

The cell shape of the honeycomb structure 1 is not particularly limited, but in a cross section perpendicular to the central axis, a polygonal shape such as a triangle, a quadrangle, a pentagon, a hexagon, an octagon, a circle, or an ellipse is preferable, and other irregular shapes may be used.

The outer shape of the honeycomb structure 1 is not particularly limited, and may be a columnar shape (cylindrical shape) having a circular end face, a columnar shape having an elliptical end face, a columnar shape having a polygonal end face (quadrangular, pentagonal, hexagonal, heptagonal, octagonal, etc.), or the like. The size of the honeycomb structure 1 is not particularly limited, and the length in the central axis direction is preferably 40 to 500 mm. For example, when the honeycomb structure 1 has a cylindrical outer shape, the end face diameter is preferably 50 to 500 mm.

The thickness of the partition walls 12 of the honeycomb structure 1 is preferably 0.10 to 0.50mm, and more preferably 0.25 to 0.45mm in terms of ease of production. For example, if the thickness is 0.20mm or more, the strength of the honeycomb structure 1 is further improved, and if the thickness is 0.50mm or less, the pressure loss can be further reduced when the honeycomb structure 1 is used as a filter. The thickness of the partition wall 12 and the thicknesses of the trap layer 23 and the heat insulating layer 24 described later are: the average value obtained by the method of observing the cross section of the honeycomb structure 1 in the central axis direction with a microscope was measured.

The porosity of the cell walls 12 constituting the honeycomb structure 1 is preferably 30 to 70%, and more preferably 40 to 65% in terms of ease of production. If the ratio is 30% or more, the pressure loss is easily reduced, and if the ratio is 70% or less, the strength of the honeycomb structure 1 can be maintained. Here, the porosity of the partition wall 12, the trap layer 23 described later, and the heat insulating layer 24 can be measured by the following method. First, a honeycomb structure in which partition walls, a trapping layer, or a heat insulating layer are disposed on the surface of a partition wall master batch is embedded in a resin. Next, the honeycomb structure embedded in the resin is cut perpendicularly to the direction in which the cells extend. The cut surface of the honeycomb structure obtained by cutting was polished, and the trap layer in the cut surface was observed by a Scanning Electron Microscope (SEM). The ratio of pores formed in the partition wall, the trap layer, or the thermal insulation layer was measured by Image processing software (Image-Pro Plus 7.0 (trade name) manufactured by japanese Visual Science) using the observed SEM Image (5000 × magnification). The "ratio of pores" thus measured is the porosity of the partition wall, the trap layer or the heat insulating layer.

The average pore diameter of the porous partition walls 12 is preferably 5 to 30 μm, and more preferably 10 to 25 μm. If the thickness is 5 μm or more, the pressure loss can be further reduced when the honeycomb structure 1 is used as a filter, and if the thickness is 30 μm or less, the strength of the honeycomb structure 1 can be maintained. In the present specification, the terms "average pore diameter" and "porosity" mean: the average pore diameter and porosity obtained were measured by mercury porosimetry.

The cell density of the honeycomb structure 1 is not particularly limited, and is preferably 5 to 93 cells/cm²More preferably 5 to 63 cells/cm²More preferably 31 to 54 cells/cm²The range of (1).

Fig. 2(a), (b), and (c) are cross-sectional views schematically showing cross sections parallel to the extending direction of the cells 15 at the cells 15 and the partition walls 12 of the honeycomb structure 1, respectively.

In the honeycomb structure 1, the collection layer 23 having an average pore diameter smaller than that of the partition walls 12 is provided on the surfaces of the partition walls 12 in the cells 15. Magnetic particles 21 having a curie point of 700 ℃ or higher are provided on one or both of the surfaces of the partition walls of the honeycomb structure 1 and the trap layer 23 and on the trap layer 23. According to such a configuration, since the trap layer 23 having an average pore diameter smaller than that of the partition walls 12 is provided, when the honeycomb structure 1 is used as a filter, carbon particles and the like contained in the exhaust gas can be suppressed from entering the honeycomb substrate from the surfaces of the partition walls 12. Therefore, the combustion efficiency of the carbon particulates and the like is good, and the increase in the pressure loss of the filter can be suppressed. Further, since the magnetic particles having a curie point of 700 ℃ or higher are provided on one side or both sides of the trapping layer 23, the honeycomb temperature sufficient for raising the catalytic temperature to the catalyst activation temperature or higher can be achieved by induction heating, and the honeycomb filter can be easily regenerated by burning and removing the carbon particles and the like trapped in the cells 15. Further, since the magnetic particles 21 are provided on one side or both sides of the trap layer 23, the carbon microparticles trapped in the trap layer 23 can be burned with good equivalence by inductively heating the magnetic particles 21 located nearby. Therefore, the combustion efficiency of the carbon particulates and the like is good, and the increase in the pressure loss of the filter can be more favorably suppressed.

The average pore diameter of the collection layer 23 and the thermal insulation layer 24 can be measured by mercury intrusion method. In this measurement method, the difference between the mercury intrusion curve (pore volume frequency) with the trap layer or the thermal insulation layer attached and the mercury intrusion curve of the base material with only the trap layer or the thermal insulation layer cut off is used as the mercury intrusion curve of the trap layer or the thermal insulation layer in the form of a peak value in the mercury intrusion meter, and the peak value is set as the average pore diameter. Further, SEM images of the cross section of the honeycomb structure were taken, and by image analysis of the trap layer or the heat insulating layer portion, 2-valued voids and solid portions were obtained, and voids of 20 or more were randomly selected, and the average value of inscribed circles thereof was defined as the average pore diameter.

The arrangement form of the trapping layer 23 and the magnetic particles 21 is not particularly limited, and the magnetic particles 21 may be provided between the surface of the partition wall 12 and the trapping layer 23 or on the trapping layer 23, or on both of them. For example, as shown in fig. 2(a), a trapping layer 23 may be provided on the surface of the partition wall 12 in the cell 15, and the magnetic particles 21 may be provided on the surface of the trapping layer 23 (on the flow path side of the cell 15). As shown in fig. 2(b), magnetic particles 21 may be provided on the surfaces of the partition walls 12 in the cells 15, and a trapping layer 23 may be provided on the surfaces of the magnetic particles 21 (on the flow path side of the cells 15). As shown in fig. 2 c, the magnetic particles 21 may be provided on the surfaces of the partition walls 12 in the cells 15, the trapping layer 23 may be provided on the surfaces of the magnetic particles 21 (on the flow path side of the cells 15), and the magnetic particles 21 may be provided on the surfaces of the trapping layer 23 (on the flow path side of the cells 15). In the configuration of fig. 2(c), since the magnetic particles 21 are provided on both sides (the partition wall 12 side and the flow path side of the cells 15) on the trapping layer 23, the combustion efficiency of the carbon particles and the like trapped by the trapping layer 23 is better than that of the configurations of fig. 2(a) and (b). In the configuration of fig. 2(a) and (b), the cross-sectional area of the flow path of the compartment 15 is wider and the pressure loss of the filter is smaller than that of the configuration of fig. 2 (c).

In fig. 2(a), (b), and (c), the magnetic particles 21 are described as being layered for convenience, but actually, as shown in fig. 3(a), (b), and (c), they are in the form of particles. As shown in fig. 3(a), (b), and (c), the trap layer 23 is a layer formed by the group of particles 22. The particles 22 constituting the trapping layer 23 may be separated from each other, may be in contact with each other, or may be in contact with each other and sintered. Fig. 3(a) is a partially enlarged view of the vicinity of the surface of the partition wall 12 in the cross-sectional view of fig. 2(a), fig. 3(b) is a partially enlarged view of the vicinity of the surface of the partition wall 12 in the cross-sectional view of fig. 2(b), and fig. 3(c) is a partially enlarged view of the vicinity of the surface of the partition wall 12 in the cross-sectional view of fig. 2 (c).

The average pore diameter of the trap layer 23 is preferably 1 to 10 μm, more preferably 1 to 8 μm, and still more preferably 1 to 5 μm. If the average pore diameter of the trapping layer 23 is 1 μm or more, the pressure loss can be further reduced when the honeycomb structure 1 is used as a filter. When the honeycomb structure 1 is used as a filter, it is possible to favorably prevent carbon particles and the like contained in the exhaust gas from leaking to the outside of the honeycomb structure 1 through the pores of the partition walls 12 if the average pore diameter of the trapping layer 23 is 10 μm or less. The material of the trap layer 23 may be a compound containing an oxide of at least one element or two or more elements selected from the group consisting of Si, Al, Mg, and Ti. The material of the trap layer 23 may include one selected from the group consisting of SiO₂、Al₂O₃、MgO、TiO₂Cordierite (2 MgO.2SiO)₂·5SiO₂) Aluminum titanate (Al)₂O₃·TiO₂) And magnesium titanate (MgO. TiO)₂) At least one or two or more of the group.

The porosity of the trap layer 23 is preferably 40 to 80%, more preferably 50 to 80%, and still more preferably 60 to 80%. If the porosity of the trapping layer 23 is 40% or more, the pressure loss can be further reduced when the honeycomb structure 1 is used as a filter. If the porosity of the trap layer 23 is 80% or less, when the honeycomb structure 1 is used as a filter, it is possible to favorably prevent carbon particles and the like contained in the exhaust gas from leaking to the outside of the honeycomb structure 1 through the pores of the partition walls 12.

The thickness of the trap layer 23 is preferably 10 to 80 μm, more preferably 10 to 50 μm, and still more preferably 10 to 30 μm. When the honeycomb structure 1 is used as a filter, it is possible to suppress leakage of carbon particles and the like contained in the exhaust gas to the outside of the honeycomb structure 1 through the pores of the partition walls 12 if the thickness of the trapping layer is 10 μm or more. If the thickness of the trapping layer 23 is 80 μm or less, the pressure loss can be further reduced when the honeycomb structure 1 is used as a filter.

The thermal conductivity of the trap layer 23 is preferably lower than that of the porous partition walls 12. With such a configuration, the heat release from the magnetic particles 21 subjected to induction heating into the partition walls 12 can be suppressed, and the combustion efficiency of the carbon microparticles and the like trapped by the trapping layer 23 is improved. The thermal conductivity of the trap layer 23 is preferably 2W/mK or less, more preferably 1W/mK or less, further preferably 0.5W/mK or less, and typically 0.1 to 1W/mK. When the trap layer 23 does not have the heat insulating layer 24 described later but the trap layer 23 has a heat insulating function, the thermal conductivity is typically 0.01 to 1W/mK.

The thermal conductivity of the trap layer 23, the porous partition walls 12, and the thermal insulation layer 24 described later can be measured as follows. That is, the density of the material itself constituting each of the trap layer 23, the porous partition walls 12, and the heat insulating layer 24 was measured by a mercury porosimeter, the specific heat was measured by a dsc (differential Scanning calorimeter) method, and the thermal diffusivity was measured by a laser flash method. Next, the thermal conductivity of this material was calculated from a relational expression of thermal diffusivity × specific heat × density, which is thermal conductivity.

As described above, the curie point of the magnetic particles 21 is 700 ℃. The magnetic body having a curie point of 700 ℃ or higher may be made of a material containing at least one element selected from the group consisting of Fe, Co, and Ni, and examples thereof include: the balance of Co-20 mass% Fe, the balance of Co-25 mass% Ni-4 mass% Fe, the balance of Fe-15-35 mass% Co, the balance of Fe-17 mass% Co-2 mass% Cr-1 mass% Mo, the balance of Fe-49 mass% Co-2 mass% V, the balance of Fe-18 mass% Co-10 mass% Cr-2 mass% Mo-1 mass% Al, the balance of Fe-27 mass% Co-1 mass% Nb, the balance of Fe-20 mass% Co-1 mass% Cr-2 mass% V, the balance of Fe-35 mass% Co-1 mass% Cr, the balance of Fe-17 mass% Cr, pure cobalt, pure iron, soft electromagnetic iron, the balance of Fe-0.1-0.5 mass% Mn, the balance of Fe-3 mass% Si, etc. Here, the curie point of the magnetic particles 21 is a temperature at which the ferromagnetic property is lost.

The average particle diameter D50 based on the volume of the magnetic particles 21 is preferably 10 to 3000 μm. When the average particle diameter D50 based on the volume of the magnetic particles 21 is 10 μm or more, the heating efficiency is good. When the average particle diameter D50 based on the volume of the magnetic particles 21 is 3000 μm or less, the magnetic particles can be easily supported on the honeycomb. The average particle diameter D50 based on the volume of the magnetic particles 21 is more preferably 10 to 1000. mu.m, and still more preferably 10 to 300. mu.m.

The volume ratio of the magnetic particles 21 is preferably 1 to 30% with respect to the volume of the entire outer peripheral wall 11 and the cell walls 12 of the honeycomb structure 1. If the volume ratio of the magnetic particles 21 is 1% or more with respect to the volume of the entire outer peripheral wall 11 and the cell walls 12 of the honeycomb structure 1, the honeycomb structure 1 can be heated efficiently. If the volume ratio of the magnetic particles 21 is 30% or less with respect to the volume of the entire outer peripheral wall 11 and the cell walls 12 of the honeycomb structure 1, more carbon fine particles and the like can be trapped, and when the honeycomb structure 1 is used as a filter, the pressure loss can be further reduced. The volume ratio of the magnetic particles 21 can be controlled by controlling the total mass of the magnetic particles 21 used in the production of the honeycomb structure 1 and the mass of the entire outer peripheral wall 11 and the partition walls 12. The volume ratio of the magnetic particles 21 can be calculated by measuring the density of the raw material of the magnetic particles 21 and the densities of the raw material of the outer peripheral wall 11 and the partition walls 12 used in the production of the honeycomb structure 1 in advance using a pycnometer or the like and using the densities and the respective masses. The volume ratio of the magnetic particles 21 can be measured by performing image analysis on the honeycomb structure 1 to obtain the ratio of the total area or volume of the magnetic particles 21 to the area or volume of the entire outer peripheral wall 11 and the entire partition walls 12.

The surfaces of the magnetic particles 21 are preferably covered with a protective layer. With such a configuration, the magnetic particles 21 are protected by the protective layer, and an increase in resistance due to deterioration of the magnetic particles 21 can be favorably suppressed. The protective layer has a function of protecting the magnetic particles 21 from deterioration, for example, a function of preventing oxidation of the magnetic particles 21.

As a material of the protective layer, ceramics, glass, or a composite material of ceramics and glass can be used. The composite material may contain glass in an amount of, for example, 50 vol% or more, more preferably 60 vol% or more, and still more preferably 70 vol% or more. Examples of the ceramic constituting the protective layer include: SiO 2₂System, Al₂O₃SiO 2₂－Al₂O₃SiO 2₂－ZrO₂SiO 2₂－Al₂O₃－ZrO₂And (d) a ceramic. Examples of the glass constituting the protective layer include: b of lead-free system₂O₃－Bi₂O₃System, B₂O₃－ZnO－Bi₂O₃System, B₂O₃-ZnO based, V₂O₅－P₂O₅System, SnO-P₂O₅System, SnO-ZnO-P₂O₅SiO 2₂－B₂O₃－Bi₂O₃SiO 2₂－Bi₂O₃－Na₂O-based, SiO₂－Al₂O₃MgO-based glass and the like.

Fig. 4 is a cross-sectional view schematically showing a cross section parallel to the extending direction of the cells 15 in the cells 15 and the partition walls 12 of the honeycomb structure 1 having the heat insulating layer 24 according to the embodiment of the present invention. In fig. 4, when the trap layer 23 and the magnetic particles 21 are in the form shown in fig. 2(a), a heat insulating layer 24 is further provided between the surface of the partition wall 12 and the trap layer 23. The heat insulating layer 24 is not limited to this, and when the trap layer 23 and the magnetic particles 21 are in the form shown in fig. 2(b), they may be further provided between the surfaces of the partition walls 12 and the magnetic particles 21. In the case where the trap layer 23 and the magnetic particles 21 are in the form shown in fig. 2(c), the heat insulating layer 24 may be further provided between the surfaces of the partition walls 12 and the magnetic particles 21. In these configurations, by making the thermal conductivity of the heat insulating layer 24 lower than the thermal conductivity of the trap layer 23 or making the thermal conductivity of the heat insulating layer 24 lower than the thermal conductivity of the partition walls 12, it is possible to suppress the release of heat from the magnetic particles 21 subjected to induction heating into the partition walls 12, and the combustion efficiency of the carbon microparticles and the like trapped by the trap layer 23 is better. The thermal conductivity of the thermal insulation layer 24 is preferably 2W/mK or less, more preferably 1W/mK or less, further preferably 0.5W/mK or less, and typically 0.01 to 1W/mK.

The porosity of the heat-insulating layer 24 is preferably higher than that of the trap layer 23 and is 60 to 98%. Since the porosity of the heat insulating layer 24 is higher than that of the trapping layer 23, the heat release from the magnetic particles 21 subjected to induction heating into the partition walls 12 can be suppressed, and the combustion efficiency of the carbon particles and the like trapped by the trapping layer 23 is better. If the porosity of the heat insulating layer 24 is 60% or more, the gas permeability is good, and the pressure loss is further reduced. If the porosity of the heat insulating layer 24 is 98% or less, the heat release from the magnetic particles 21 subjected to induction heating into the partition walls 12 can be suppressed, and the combustion efficiency of the carbon microparticles and the like trapped by the trapping layer 23 is better. The porosity of the heat insulating layer 24 is preferably 60 to 98%, more preferably 65 to 98%.

The average pore diameter of the heat insulating layer 24 is preferably smaller than the average pore diameter of the partition wall 12 and is 0.005 to 1 μm. Since the average pore diameter of the heat insulating layer 24 is smaller than the average pore diameter of the partition walls 12, the heat release from the magnetic particles 21 subjected to induction heating into the partition walls 12 can be suppressed, and the combustion efficiency of the carbon microparticles and the like trapped by the trapping layer 23 is improved. If the average pore diameter of the heat insulating layer 24 is 0.005 μm or more, the gas permeability is good, and the pressure loss is further reduced. If the average pore diameter of the heat insulating layer 24 is 1 μm or less, the heat release from the magnetic particles 21 subjected to induction heating into the partition walls 12 can be suppressed, and the combustion efficiency of the carbon microparticles and the like trapped by the trapping layer 23 is better. The average pore diameter of the heat insulating layer 24 is more preferably 0.005 to 1 μm, and still more preferably 0.005 to 0.5. mu.m.

The material of the heat insulating layer 24 includes: ZrO (ZrO)₂、SiO₂、TiO₂Or glass, etc.

Such a honeycomb structure 1 is produced by forming a raw material containing a ceramic raw material into a honeycomb shape having partition walls 12, forming a honeycomb formed body by partitioning the partition walls 12 into a plurality of cells 15 each of which penetrates from one end face to the other end face to form a fluid flow path, drying the honeycomb formed body, and then firing the dried honeycomb formed body to produce the honeycomb structure 1. When such a honeycomb structure is used as the honeycomb structure 1 of the present embodiment, the outer peripheral wall may be extruded integrally with the honeycomb structure portion and directly used as the outer peripheral wall, or after molding or firing, the outer periphery of the honeycomb molded body (honeycomb structure) may be ground into a predetermined shape, and a coating material may be applied to the honeycomb structure after the outer periphery grinding to form an outer peripheral coating layer. In the honeycomb structure 1 of the present embodiment, for example, a honeycomb structure having an outer periphery may be used without grinding the outermost periphery of the honeycomb structure, and the outer peripheral coating layer may be formed by further applying the coating material to the outer peripheral surface of the honeycomb structure having the outer periphery (that is, the outer side of the outer periphery of the honeycomb structure). That is, in the former case, only the outer peripheral coating layer made of the coating material is the outer peripheral wall located at the outermost periphery on the outer peripheral surface of the honeycomb structure. On the other hand, in the latter case, an outer peripheral wall having a two-layer structure located at the outermost periphery, which is obtained by further laminating an outer peripheral coating layer made of a coating material, is formed on the outer peripheral surface of the honeycomb structure. The outer peripheral wall may be extruded integrally with the honeycomb structure portion, directly fired, and used as the outer peripheral wall without processing the outer periphery.

The composition of the coating material is not particularly limited, and various known coating materials can be suitably used. The coating material may further contain colloidal silica, organic binders, clays, and the like. The organic binder is preferably used in an amount of 0.05 to 0.5% by mass, more preferably 0.1 to 0.2% by mass. The clay is preferably used in an amount of 0.2 to 2.0% by mass, more preferably 0.4 to 0.8% by mass.

The honeycomb structure 1 is not limited to the honeycomb structure 1 of an integral type in which the partition walls 12 are integrally formed, and may be, for example, a honeycomb structure 1 (hereinafter, may be referred to as a "joined honeycomb structure") having a structure in which a plurality of columnar honeycomb cells having porous partition walls 12 are combined with a joining material layer interposed therebetween, and a plurality of cells 15 forming fluid flow paths are partitioned by the partition walls 12.

The honeycomb structure 1 of the present embodiment may be a honeycomb structure in which a catalyst is supported on the surfaces of porous partition walls 12 forming the inner walls of the plurality of cells 15 and/or in pores of the partition walls 12. As described above, the honeycomb structure 1 of the present embodiment may be configured such that: a catalyst carrier carrying a catalyst.

The kind of the catalyst is not particularly limited, and may be appropriately selected according to the purpose and use of the honeycomb structure 1. For example, a noble metal-based catalyst or a catalyst other than a noble metal-based catalyst may be mentioned. Examples of the noble metal-based catalyst include: a three-way catalyst in which a noble metal such as platinum (Pt), palladium (Pd), rhodium (Rh) is supported on the surface of alumina pores and which contains a co-catalyst such as cerium oxide or zirconium dioxide, an oxidation catalyst, or a Nitrogen Oxide (NO) containing an alkaline earth metal and platinum_x) NO of the storage component_xA trap reduction catalyst (LNT catalyst). Examples of the catalyst not using a noble metal include: NO containing copper-or iron-substituted zeolite_xSelective reduction catalysts (SCR catalysts), and the like. In addition, 2 or more catalysts selected from the group consisting of these catalysts may be used. The method for supporting the catalyst is also not particularly limited, and the catalyst may be supported by a conventional method for supporting the catalyst on the honeycomb structure.

The fired honeycomb structure may be used as a honeycomb unit, and the side surfaces of the plurality of honeycomb units may be joined together with a joining material to be integrated into a honeycomb structure in which the honeycomb units are joined together. The honeycomb structure in a state where the honeycomb cells are joined can be manufactured, for example, as follows. The bonding material is applied to the bonding surface (side surface) in a state where masks for preventing the bonding material from adhering are attached to both bottom surfaces of each honeycomb unit.

Next, these honeycomb cells are adjacently arranged so that the side surfaces of the honeycomb cells face each other, and the adjacent honeycomb cells are pressure-bonded to each other, followed by heating and drying. In this manner, a honeycomb structure was produced in which the side surfaces of the adjacent honeycomb units were joined to each other by a joining material. The outer peripheral portion of the honeycomb structure may be ground into a desired shape (for example, a cylindrical shape), and the outer peripheral surface may be coated with a coating material and then heated and dried to form the outer peripheral wall 11.

The material of the bonding material adhesion preventing mask is not particularly limited, and for example, synthetic resin such as polypropylene (PP), polyethylene terephthalate (PET), polyimide, or teflon (registered trademark) can be preferably used. The mask preferably includes an adhesive layer, and the material of the adhesive layer is preferably an acrylic resin, a rubber (for example, a rubber containing natural rubber or synthetic rubber as a main component), or a silicone resin.

As the mask for preventing adhesion of the bonding material, for example, an adhesive film having a thickness of 20 to 50 μm can be preferably used.

As the bonding material, for example, a material prepared by mixing ceramic powder, a dispersion medium (e.g., water, etc.), and additives such as a binder, a peptizer, and a foaming resin added as necessary can be used. The ceramic is preferably a ceramic containing at least one selected from the group consisting of cordierite, mullite, zircon, aluminum titanate, silicon carbide, silicon nitride, zirconium dioxide, spinel, indian stone, sapphirine, corundum, and titanium dioxide, and is more preferably the same material as the honeycomb structure. Examples of the binder include: polyvinyl alcohol, methyl cellulose, CMC (carboxymethyl cellulose), and the like.

Next, a method for manufacturing the honeycomb structure 1 will be described. First, a honeycomb structure having porous partition walls and a plurality of cells partitioned by the partition walls is prepared. For example, when a honeycomb structure including cordierite is produced, first, a cordierite forming raw material is prepared as a material for a green body. The cordierite forming raw material contains a silica source component, a magnesia source component, an alumina source component, and the like because each component is mixed in accordance with the theoretical composition of cordierite crystal. Among them, quartz and fused silica are preferably used as the silica source component, and the particle diameter of the silica source component is preferably 100 to 150 μm.

Examples of the magnesium oxide source component include: talc, magnesite, etc. Among them, talc is preferable. The content of talc in the cordierite forming raw material is preferably 37 to 43 mass%. The particle diameter (average particle diameter) of talc is preferably 5 to 50 μm, and more preferably 10 to 40 μm. In addition, the magnesium oxide (MgO) source component may contain Fe as an impurity₂O₃、CaO、Na₂O、K₂O, and the like.

The alumina source component preferably contains at least one of alumina and aluminum hydroxide in terms of a small amount of impurities. In addition, the cordierite forming raw material preferably contains 10 to 30 mass% of aluminum hydroxide and 0 to 20 mass% of alumina.

Next, a material for a green body (additive) to be added to the cordierite forming raw material is prepared. As additives, at least a binder and a pore former are used. In addition, a dispersant or a surfactant may be used in addition to the binder and the pore-forming agent.

As the pore-forming agent, a substance that can be oxidized and removed by reacting with oxygen at a temperature not higher than the firing temperature of cordierite, a low-melting-point reaction substance having a melting point at a temperature not higher than the firing temperature of cordierite, or the like can be used. Examples of the substance that can be removed by oxidation include: resins (particularly, particulate resins), graphite (particularly, particulate graphite), and the like. As the low melting point reactant, at least one metal selected from the group consisting of iron, copper, zinc, lead, aluminum, and nickel, an alloy containing these metals as a main component (for example, in the case of iron, carbon steel, cast iron, stainless steel), or an alloy containing two or more kinds of these metals as a main component can be used. Among them, the low melting point reaction substance is preferably a powdery or fibrous iron alloy. Further, the particle diameter or fiber diameter (average particle diameter) is preferably 10 to 200. mu.m. The shape of the low melting point reaction substance is preferably spherical, rhomboidal, or candy-like, because the shape of the fine pores can be easily controlled.

Examples of the binder include: hydroxypropyl methylcellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, and the like. Examples of the dispersant include: dextrin, polyhydric alcohols, and the like. Examples of the surfactant include fatty acid soaps. One additive may be used alone, or two or more additives may be used.

Then, the raw material for the green body is kneaded by mixing 3 to 8 parts by mass of a binder, 3 to 40 parts by mass of a pore-forming agent, 0.1 to 2 parts by mass of a dispersant, and 10 to 40 parts by mass of water with respect to 100 parts by mass of the cordierite forming raw material to prepare a green body.

Next, the prepared preform is molded into a honeycomb shape by extrusion molding, injection molding, press molding, or the like, to obtain a green honeycomb molded body. The extrusion molding method is preferably used in view of ease of continuous molding and the ability to orient the cordierite crystals, for example. The extrusion molding can be carried out by using a vacuum pug mill, a plunger type extrusion molding machine, a twin-screw type continuous extrusion molding machine or the like.

Next, the honeycomb formed body was dried and adjusted to a predetermined size to obtain a dried honeycomb body. The honeycomb formed body can be dried by hot air drying, microwave drying, dielectric drying, drying under reduced pressure, vacuum drying, freeze drying, or the like. In addition, from the viewpoint of being able to dry the whole quickly and uniformly, it is preferable to dry the whole by combining hot air drying and microwave drying or dielectric drying.

In addition, a material for forming a trapping layer, a material for forming magnetic particles, and a material for forming a heat insulating layer, which may be necessary, are separately prepared. As the material for forming the trap layer, a material containing a metal selected from the group consisting of SiO₂、Al₂O₃MgO and TiO₂At least 1 material of the group. As the magnetic particle-forming raw material, particles containing at least 1 element selected from the group consisting of Fe, Co, and Ni can be used. As the material for forming the heat-insulating layer, ZrO can be used₂、SiO₂、TiO₂Particles, alkoxides of the above metals, gels, glasses, or the like.

Next, as necessary, first, the heat insulating layer forming material is applied to the surfaces of the partition walls of the cells of the honeycomb dried body. Next, the collection layer-forming material and the magnetic particle-forming material are applied to the surfaces of the partition walls of the cells or the surfaces of the thermal insulation layer-forming material in a desired order.

When the honeycomb structure 20 having the plugging portions shown in fig. 5 and 6 is manufactured, a raw material of the plugging portions is prepared here. The material for the plugging portion (plugging slurry) may be the same material as that for the partition wall (honeycomb dried body), or may be a different material. Specifically, the raw material for the plugging portion can be obtained by mixing a ceramic raw material, a surfactant, and water, adding a sintering aid, a pore-forming agent, and the like as necessary, making the mixture into a slurry, and kneading the slurry using a mixer or the like. Next, a mask was applied to a part of the cell openings of one end face of the honeycomb dried body, the end face was immersed in a storage container storing a plugging slurry, and the cells to which the mask was not applied were filled with the plugging slurry. Similarly, a mask was applied to a part of the cell openings of the other end face of the honeycomb dried body, the end face was immersed in a storage vessel storing the plugging slurry, the cells to which the mask was not applied were filled with the plugging slurry, and then the cells were dried to obtain a honeycomb dried body having plugged portions. As a method of sealing pores, it is a relatively simple method to squeeze a paste-like material into a blade such as a squeegee member. The depth control by the squeezing times of the pulp scraping component is simple. The number of times of squeezing is increased for a portion of the compartment where the magnetic substance is to be inserted deeply, and the number of times of squeezing is decreased for a shallow portion in the periphery.

Next, the honeycomb dried body is fired to obtain a honeycomb structure. The drying conditions may be the same as those for drying the honeycomb formed body. In the case of using a cordierite forming raw material, the firing conditions may be generally such that the firing is carried out at 1410 to 1440 ℃ for 3 to 15 hours in an atmospheric atmosphere.

When the honeycomb structure obtained in this way is manufactured in a state in which the outer peripheral wall is formed on the outer peripheral surface thereof, the outer peripheral surface thereof may be ground to remove the outer peripheral wall. In the subsequent step, the outer periphery of the honeycomb structure from which the outer peripheral wall is removed is coated with a coating material to form an outer peripheral coating layer. In the case of grinding the outer peripheral surface, a part of the outer peripheral wall may be ground and removed, and the outer peripheral coating may be formed on the part by the coating material.

In the case of preparing the coating material, it can be prepared, for example, by using a double-shaft rotary type vertical mixer.

In addition, the coating material may further contain colloidal silica, organic binders, clay, and the like. The organic binder is preferably used in an amount of 0.05 to 0.5% by mass, more preferably 0.1 to 0.2% by mass. The clay is preferably used in an amount of 0.2 to 2.0% by mass, more preferably 0.4 to 0.8% by mass.

A coating material was applied to the outer peripheral surface of the honeycomb structure prepared in the foregoing, and the applied coating material was dried to form an outer peripheral coating layer. With such a configuration, the occurrence of cracking in the outer peripheral coating layer during drying or heat treatment can be effectively suppressed.

As a method for applying the coating material, for example, a method in which the honeycomb structure is placed on a rotary table, rotated, and the coating material is discharged from a blade-shaped coating nozzle, and the coating nozzle is pressed so as to be along the outer peripheral portion of the honeycomb structure, thereby applying the coating material is given. With such a configuration, the coating material can be applied with a uniform thickness. In addition, the outer peripheral coating layer formed can have a small surface roughness, an excellent appearance, and is less likely to be broken by thermal shock.

When the outer peripheral wall of the honeycomb structure is removed by grinding, the outer peripheral coating layer is formed by applying a coating material to the entire outer peripheral surface of the honeycomb structure. On the other hand, when the outer peripheral wall exists on the outer peripheral surface of the honeycomb structure or a part of the outer peripheral wall is removed, the outer peripheral coating layer may be formed by applying the coating material partially or entirely on the outer peripheral surface of the honeycomb structure.

The method of drying the applied coating material (i.e., the undried outer circumferential coating layer) is not particularly limited, and for example, from the viewpoint of preventing drying cracking, it is preferable to use a method of drying 25% or more of the moisture in the coating material by holding at room temperature for 24 hours or more and then holding at 600 ℃ for 1 hour or more in an electric furnace to remove the moisture and organic matter.

In addition, in the case where the openings of the cells of the honeycomb structure are not sealed in advance, the openings of the cells may be sealed after the outer peripheral coat layer is formed.

Fig. 5 is a perspective view schematically showing a honeycomb structure 20 having a plugging portion 19 according to an embodiment of the present invention. Fig. 6 is a cross-sectional view schematically showing a cross section parallel to the extending direction of the cells 15 in the cells 15 and the partition walls 12 of the honeycomb structure 20 having the plugging portions 19 according to the embodiment of the present invention. The honeycomb structure 20 is formed in a columnar shape, and includes an outer peripheral wall 11 and porous cell walls 12, the cell walls 12 are disposed inside the outer peripheral wall 11 and partition a plurality of cells 15, and the plurality of cells 15 penetrate from one end surface 13 to the other end surface 14 to form flow paths. In the illustrated honeycomb structure 20, the cells 15 include: a plurality of cells A having an opening on one end surface 13 side and a plugging portion 19 on the other end surface 14; and a plurality of cells B arranged alternately with the cells A, each of which has a hole-closing portion 19 on one end surface 13 and is open on the other end surface 14 side. The cells a and B are alternately arranged adjacent to each other with the partition walls 12 interposed therebetween, and both end surfaces thereof form a checkered pattern. The number, arrangement, shape, etc. of the compartments a and B and the thickness of the partition wall 12 are not limited, and can be appropriately designed as necessary. The honeycomb structure 20 having such a configuration can be used as a filter (for example, a diesel particulate filter (hereinafter, also referred to as "DPF")) provided with the plugging portion 19 for burning and removing particulate matter (carbon particulates) in the exhaust gas by induction heating. The plugged portions 19 can be configured as the plugged portions used as the plugged portions of a conventionally known honeycomb structure. The arrangement may be performed after the outer peripheral coat layer is formed, or may be performed in a state before the outer peripheral coat layer is formed, that is, at a stage of manufacturing the honeycomb structure 20.

< 2. exhaust gas purifying apparatus

The exhaust gas purifying device can be configured by using the honeycomb structure according to each embodiment of the present invention. Fig. 7 shows, as an example, a schematic view of an exhaust gas flow path of the exhaust gas purifying device 6 in which the honeycomb structure 1 is incorporated. The exhaust gas purifying device 6 has a honeycomb structure 1 and a coil wiring 4 spirally wound around the outer periphery of the honeycomb structure 1. The exhaust gas purifying device 6 includes a metal pipe 2 that houses the honeycomb structure 1 and the coil wiring 4. The exhaust gas purifying device 6 may be disposed in the enlarged diameter portion 2a of the metal pipe 2. The coil wiring 4 can be fixed inside the metal pipe 2 by a fixing member 5. The fixing member 5 is preferably a heat-resistant member such as ceramic fiber. The honeycomb structure 1 may carry a catalyst.

The coil wiring 4 is spirally wound around the outer periphery of the honeycomb structure 1. It is assumed that 2 or more coil wires 4 are used. In response to the ON (ON) of the switch SW, an ac current supplied from the ac power supply CS flows through the coil wiring 4, and as a result, a magnetic field that periodically changes is generated around the coil wiring 4. The on/off of the switch SW is controlled by the control unit 3. The control unit 3 can turn on the switch SW in synchronization with the start of the engine so that the alternating current flows through the coil wiring 4. Note that, the control unit 3 is assumed to be configured to turn on the switch SW regardless of the start of the engine (for example, in response to the operation of the heating switch pressed by the driver).

In the present invention, the temperature of the honeycomb structure 1 is raised in accordance with a change in the magnetic field corresponding to the alternating current flowing through the coil wiring 4. Thereby, the carbon particulates and the like trapped by the honeycomb structure 1 are burned. When the honeycomb structure 1 carries a catalyst, the temperature of the honeycomb structure 1 is raised to increase the temperature of the catalyst carried on the catalyst carrier included in the honeycomb structure 1, thereby promoting the catalytic reaction. In general, carbon monoxide (CO), Nitrogen Oxides (NO)_x) The hydrocarbon (CH) is oxidized or reduced to carbon dioxide (CO)₂) Nitrogen (N)₂) Water (H)₂O)。

Description of the symbols

1. 20 honeycomb structure

2 Metal tube

3 control part

4 coil wiring

5 fixing part

6 exhaust gas purification device

11 outer peripheral wall

12 partition wall

13. 14 end face

15 Compartment (Compartment A + Compartment B)

19 hole sealing part

21 magnetic particles

22 particles constituting the trapping layer

23 trapping layer

And 24, an insulating layer.