阅读说明：本技术 蜂窝结构体、废气净化装置、排气系统及蜂窝结构体的制造方法 (Honeycomb structure, exhaust gas purifying apparatus, exhaust system, and method for manufacturing honeycomb structure ) 是由 宫入由纪夫 下田岳秀 青木崇志 坂本浩文 桝田昌明 近藤厚男 泉有仁枝 加藤恭平 胁 于 2019-04-17 设计创作，主要内容包括：本发明提供蜂窝结构体及废气净化装置,能够利用电加热将碳微粒等燃烧除去,并且,即便在产生冷凝水的位置也能够使用,不存在由冷凝水或碳堆积所引起的短路问题,压力损失也较低。蜂窝结构体是具有多孔质的隔壁和位于最外周的外周壁的柱状的蜂窝结构体,该多孔质的隔壁区划形成多个隔室,该多个隔室形成流体的流路,并从流体的流入侧的端面即流入端面延伸至流体的流出侧的端面即流出端面,其中,在隔壁的表面的至少一部分具有表面层,表面层包含磁性体粒子且具有通气性。(The invention provides a honeycomb structure and an exhaust gas purifying apparatus, which can burn and remove carbon particles and the like by electric heating, can be used even at a position where condensed water is generated, has no short circuit problem caused by the condensed water or carbon accumulation, and has low pressure loss. The honeycomb structure is a columnar honeycomb structure having porous cell walls and an outer peripheral wall located on the outermost periphery, the porous cell walls defining a plurality of cells which form flow paths for a fluid and extend from an inflow end face, which is an end face on the inflow side of the fluid, to an outflow end face, which is an end face on the outflow side of the fluid, wherein at least a part of the surfaces of the cell walls has a surface layer containing magnetic particles and having air permeability.)

1. A honeycomb structure having porous cell walls and a columnar honeycomb structure having an outer peripheral wall located at the outermost periphery,

the porous partition walls define a plurality of cells which form flow paths for the fluid and extend from an inflow end face, which is an end face on the fluid inflow side, to an outflow end face, which is an end face on the fluid outflow side,

the honeycomb structure is characterized in that,

the partition walls have a surface layer on at least a part of the surface thereof, the surface layer containing magnetic particles and having air permeability.

2. The honeycomb structure according to claim 1,

at least one surface of the partition is covered with the surface layer.

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

the Curie temperature of the magnetic particles exceeds 450 ℃.

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

the porosity of the surface layer is 50% or more.

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

the surface layer has an average pore diameter of 10 [ mu ] m or less.

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

the magnetic particles have a weight-average particle diameter of 20 [ mu ] m or less.

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

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

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

the honeycomb structure is formed of a ceramic material.

9. The honeycomb structure according to claim 8,

the ceramic material is at least 1 selected from the group consisting of cordierite, silicon carbide, aluminum titanate, silicon nitride, mullite, and alumina.

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

the shortest diameter d of the magnetic particles is 0.1 to 5 μm,

l/d is not less than 3, where L [ mu ] m represents the longest diameter of the magnetic particles.

11. The honeycomb structure according to claim 10,

the magnetic particles are needle-shaped or scaly.

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

a stress relaxation layer having a thermal expansion coefficient between a thermal expansion coefficient of the surface layer and a thermal expansion coefficient of the partition wall is provided between the surface layer and the partition wall.

13. The honeycomb structure according to any one of claims 1 to 12,

the compartment comprises: the fluid flow control device includes a plurality of first cells having an opening on a fluid inflow side and a sealing portion on an end surface on a fluid outflow side, and a plurality of second cells having an opening on a fluid outflow side and a sealing portion on an end surface on a fluid inflow side.

14. A honeycomb structure having porous cell walls and a columnar honeycomb structure having an outer peripheral wall located at the outermost periphery,

the porous partition walls define a plurality of cells which form flow paths for the fluid and extend from an inflow end face, which is an end face on the fluid inflow side, to an outflow end face, which is an end face on the fluid outflow side,

the honeycomb structure is characterized in that,

the partition walls have a surface layer on at least a part of the surface thereof, and the surface layer contains needle-like or scale-like magnetic particles.

15. An exhaust gas purification apparatus, comprising:

the honeycomb structure according to any one of claims 1 to 14;

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

and a fixing member for fixing the coil wiring in the exhaust gas flow path outside the coil wiring.

16. An exhaust system is characterized by comprising:

an exhaust silencing silencer;

the exhaust gas purifying device according to claim 15, which is provided in the exhaust muffler silencer; and

and the silencer is arranged in the exhaust silencing silencer.

17. A method for manufacturing a honeycomb structure having a columnar shape and having porous cell walls and an outer peripheral wall located at the outermost periphery,

the porous partition walls define a plurality of cells which form flow paths for the fluid and extend from an inflow end face, which is an end face on the fluid inflow side, to an outflow end face, which is an end face on the fluid outflow side,

the method for manufacturing a honeycomb structure is characterized in that,

the method comprises a step of forming a surface layer containing magnetic particles and having air permeability on at least a part of the surface of the partition wall.

18. The method of manufacturing a honeycomb structure according to claim 17,

in the step of forming a surface layer containing magnetic particles and having air permeability, at least one surface of the partition wall is covered with the surface layer.

19. The method of manufacturing a honeycomb structure according to claim 17 or 18,

the step of forming a surface layer containing magnetic particles and having air permeability includes the steps of:

a step of forming a coating film by flowing a slurry containing magnetic particles and a binder mainly composed of metal or glass into the compartment, and

and heating the coating film at a temperature not lower than the melting point of the metal or the softening point of the glass to form the surface layer.

20. The method of manufacturing a honeycomb structure according to claim 17 or 18,

the step of forming a surface layer containing magnetic particles and having air permeability includes the steps of:

a step of forming a coating film by flowing a slurry containing magnetic particles and a binder mainly composed of silica or alumina into the compartment, and

and a step of heating the coating film to cure the silica or the alumina to form the surface layer.

21. The method of manufacturing a honeycomb structure according to claim 17 or 18,

the step of forming a surface layer containing magnetic particles and having air permeability includes a step of flowing a gas containing magnetic particles into the compartment.

22. The method of manufacturing a honeycomb structure according to any one of claims 17 to 21,

the Curie temperature of the magnetic particles exceeds 450 ℃.

23. The method of manufacturing a honeycomb structure according to any one of claims 17 to 22,

the porosity of the surface layer is 50% or more.

24. The method of manufacturing a honeycomb structure according to any one of claims 17 to 23,

the surface layer has an average pore diameter of 10 [ mu ] m or less.

25. The method of manufacturing a honeycomb structure according to any one of claims 17 to 24,

the magnetic particles have a weight-average particle diameter of 20 [ mu ] m or less.

26. The method of manufacturing a honeycomb structure according to any one of claims 17 to 25,

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

27. The method of manufacturing a honeycomb structure according to claim 26,

the honeycomb structural body is formed of a ceramic material,

the ceramic material is at least 1 selected from the group consisting of cordierite, silicon carbide, aluminum titanate, silicon nitride, mullite, and alumina.

28. The method of manufacturing a honeycomb structure according to any one of claims 17 to 27, wherein the honeycomb structure is a honeycomb structure,

the shortest diameter d of the magnetic particles is 0.1 to 5 μm,

l/d is not less than 3, where L [ mu ] m represents the longest diameter of the magnetic particles.

29. The method of manufacturing a honeycomb structure according to claim 27,

the magnetic particles are needle-shaped or scaly.

Technical Field

The present invention relates to a honeycomb structure, an exhaust gas purifying apparatus, an exhaust system, and a method for manufacturing the honeycomb structure. In particular, the present invention relates to a honeycomb structure, an exhaust gas purification device, an exhaust system, and a method for manufacturing a honeycomb structure, in which carbon particles and the like can be burned and removed by electric heating, and which can be used even at a position where condensed water is generated, and which does not have a short-circuit problem due to condensed water or carbon deposition, and which has a low pressure loss.

Background

Generally, as a result of incomplete combustion, exhaust gas of an automobile contains fine particles of carbon and the like. From the viewpoint of reducing the harm to human health, there is an increasing demand for reduction of fine particles in automobile exhaust gas. At present, a reduction to an infinite approach to 0 of the particulates discharged from a gasoline engine, which is the mainstream of an automobile power source, is also required. In addition, the same is true for exhaust particulates from diesel engines.

In order to meet the above-described demand, patent document 1 proposes a honeycomb structure including a honeycomb structure portion having porous partition walls defining a plurality of cells forming flow paths of a fluid and an outer peripheral wall located on an outermost periphery, and plugging portions disposed at openings of predetermined cells in an end surface on an inlet side of the fluid of the honeycomb structure portion and openings of remaining cells in an end surface on an outlet side of the fluid. Patent document 2 proposes a technique of providing a surface layer on the surface of the cell walls of the honeycomb filter to solve the problem of pressure loss during PM deposition.

When the filter is mounted on a vehicle, it is preferable to mount the filter at an underfloor position where there is a relatively large space from the viewpoint of securing a mounting space, from the viewpoint of securing a degree of freedom in design of the exhaust system configuration. However, if the filter is disposed under the floor, there is a problem that the temperature of exhaust gas from the engine is lowered, particles (carbon particles) accumulated in the filter are not combusted, the carbon particles are accumulated, the pressure loss is excessively increased, and the output of the engine is lowered. In order to avoid the above problem, as disclosed in patent document 3, a method is proposed in which a current is passed through a conductive honeycomb structure itself, and the honeycomb structure itself is heated by joule heat generated by the current. As a heating technique that can be used even in an environment where condensed water is generated and can be used even under conditions where carbon fine particles are deposited, patent document 4 discloses a method of performing dielectric heating using a coil configured such that an electric current is not passed through the honeycomb structure itself, and the coil is configured such that: a wire is inserted into the non-conductive honeycomb cells and around the outer periphery of the honeycomb structure.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 4920752

Patent document 2: japanese patent No. 5616059

Patent document 3: japanese patent No. 5261256

Patent document 4 U.S. patent publication No. 2017/0022868

Disclosure of Invention

The inventor of the present invention found, as a result of research, that: the technique disclosed in patent document 3 has a problem that, if condensed water is generated in exhaust gas in an exhaust pipe due to the passage of electricity to the honeycomb structure, an electrical short circuit occurs. Further, it is known that an electrical short circuit occurs due to the deposition of carbon fine particles.

In addition, it was found that: if the technique disclosed in patent document 4 is applied to a honeycomb filter, some cells cannot be used as gas flow paths, and the filter filtration area is reduced, which may cause a significant increase in pressure loss.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a honeycomb structure and an exhaust gas purifying apparatus, which can burn and remove carbon particles and the like by electric heating, can be used even at a position where condensed water is generated, does not have a short-circuit problem due to condensed water or carbon deposition, and has a low pressure loss. Another object of the present invention is to provide a method for manufacturing the above honeycomb structure.

The inventors of the present invention have made extensive studies and as a result have found that the above problems can be solved by providing a surface layer containing magnetic particles and having air permeability on at least a part of the surface of the cell walls of the honeycomb structure. Namely, the present invention is determined as follows.

(1) A honeycomb structure having porous cell walls and a columnar honeycomb structure having an outer peripheral wall located at the outermost periphery,

the porous partition walls define a plurality of cells which form flow paths for the fluid and extend from an inflow end face, which is an end face on the fluid inflow side, to an outflow end face, which is an end face on the fluid outflow side,

the honeycomb structure is characterized in that,

the partition walls have a surface layer on at least a part of the surface thereof, the surface layer containing magnetic particles and having air permeability.

(2) A honeycomb structure having porous cell walls and a columnar honeycomb structure having an outer peripheral wall located at the outermost periphery,

the porous partition walls define a plurality of cells which form flow paths for the fluid and extend from an inflow end face, which is an end face on the fluid inflow side, to an outflow end face, which is an end face on the fluid outflow side,

the honeycomb structure is characterized in that,

the partition walls have a surface layer on at least a part of the surface thereof, and the surface layer contains needle-like or scale-like magnetic particles.

(3) An exhaust gas purification apparatus, comprising:

(1) the honeycomb structure according to (1) or (2);

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

and a fixing member for fixing the coil wiring in the exhaust gas flow path outside the coil wiring.

(4) An exhaust system is characterized by comprising:

an exhaust silencing silencer;

(3) the waste gas purification device is arranged in the exhaust silencing and sound reducing device; and

and the silencer is arranged in the exhaust silencing silencer.

(5) A method for manufacturing a honeycomb structure having a columnar shape and having porous cell walls and an outer peripheral wall located at the outermost periphery,

the porous partition walls define a plurality of cells which form flow paths for the fluid and extend from an inflow end face, which is an end face on the fluid inflow side, to an outflow end face, which is an end face on the fluid outflow side,

the method for manufacturing a honeycomb structure is characterized in that,

the method comprises a step of forming a surface layer containing magnetic particles and having air permeability on at least a part of the surface of the partition wall.

Effects of the invention

According to the present invention, there can be provided a honeycomb structure and an exhaust gas purifying apparatus, which can burn and remove carbon particles and the like by electric heating, can be used even at a position where condensed water is generated, do not have a short-circuit problem due to condensed water or carbon deposition, and have a low pressure loss. Further, according to the present invention, a method for manufacturing the above honeycomb structure can be provided.

Drawings

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

Fig. 2 is a schematic view of an exhaust gas flow path of an exhaust gas purifying apparatus in which a honeycomb structure according to an embodiment of the present invention is mounted.

Fig. 3 is a schematic view showing a state in which a surface layer is formed on the surface of the partition walls of the honeycomb structure.

FIG. 4 is a graph showing the relationship between time (seconds) and temperature (. degree. C.) at dielectric heating frequencies of 30kHz, 85kHz and 350kHz in the heating test of example 7.

FIG. 5 is a graph showing the relationship between time (seconds) and temperature (. degree. C.) in the heating test in examples 7 and 12.

Fig. 6 is a schematic view of an exhaust system in which a honeycomb structure according to an embodiment of the present invention is provided in an exhaust muffler.

Fig. 7 is a schematic view of an exhaust gas purifying device according to an embodiment of the present invention provided in an exhaust muffler.

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 these embodiments and can be variously modified, corrected, and improved 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 according to an embodiment of the present invention. The illustrated honeycomb structure 1 includes an outer peripheral wall 102 located at the outermost periphery, and a plurality of cells (in the illustration, a plurality of first cells 108 having a first end surface 104 open and a protruding plugged portion at a second end surface 106, and a plurality of second cells 110 having a protruding plugged portion at a first end surface 104 and an opening at a second end surface 106) arranged inside the outer peripheral wall 102 and extending in parallel between the first end surface 104 (an inflow end surface that is an end surface on the inflow side of a fluid) and the second end surface 106 (an outflow end surface that is an end surface on the outflow side of a fluid). Each of the plurality of cells constitutes a flow path of the fluid in the honeycomb structure 1. In the honeycomb structure 1 shown in the drawing, porous partition walls 112 partitioning the first cells 108 and the second cells 110 are provided, the first cells 108 and the second cells 110 are alternately arranged adjacent to each other with the partition walls 112 interposed therebetween, and both end surfaces form a checkered pattern. In the honeycomb structure according to the illustrated embodiment, all of the first cells 108 are adjacent to the second cells 110, and all of the second cells 110 are adjacent to the first cells 108. However, the plurality of compartments need not necessarily have a hole-sealing portion. Further, not all of the first compartments 108 may be adjacent to the second compartments 110, or not all of the second compartments 110 may be adjacent to the first compartments 108. The number, arrangement, shape, etc. of the compartments 108 and 110 and the thickness of the partition wall 112 are not limited, and may be appropriately designed as needed.

The material of the honeycomb structure is not particularly limited, but it is usually made of a ceramic material because it needs to be a porous body having a large number of pores, and examples thereof include: a sintered body containing cordierite, silicon carbide, aluminum titanate, silicon nitride, mullite, alumina, a silicon-silicon carbide composite material, or a silicon carbide-cordierite composite material as a main component, particularly a sintered body containing a silicon-silicon carbide composite material or silicon carbide as a main component. In the present specification, the term "silicon carbide-based" means: the honeycomb structure contains 50 mass% or more of silicon carbide in the entire honeycomb structure. The honeycomb structure body takes the silicon-silicon carbide composite material as a main component, and the main components are as follows: the honeycomb structure contains 90 mass% or more (total mass) of the silicon-silicon carbide composite material in the entire honeycomb structure. Here, the silicon-silicon carbide composite material contains silicon carbide particles as an aggregate and silicon as a binder for binding the silicon carbide particles, and it is preferable that a plurality of silicon carbide particles are bound with silicon so that pores are formed between the silicon carbide particles. The honeycomb structure mainly containing silicon carbide means that: the honeycomb structure 1 contains 90 mass% or more (total mass) of silicon carbide in the entire honeycomb structure.

Preferably, the honeycomb structure is formed of at least 1 ceramic material selected from the group consisting of cordierite, silicon carbide, aluminum titanate, silicon nitride, mullite, and alumina.

The cell shape of the honeycomb structure is not particularly limited, and 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 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, or a columnar shape having a polygonal end face (such as a quadrangle, a pentagon, a hexagon, a heptagon, or an octagon). The size of the honeycomb structure is not particularly limited, and the length in the central axis direction is preferably 40 to 500 mm. For example, when the honeycomb structure has a cylindrical outer shape, the radius of the end face is preferably 50 to 500 mm.

The thickness of the partition walls of the honeycomb structure is preferably 0.20 to 0.50mm, and more preferably 0.25 to 0.45mm in view of ease of production. For example, if the thickness of the partition walls is 0.20mm or more, the strength of the honeycomb structure is further improved; if the thickness of the partition walls is 0.50mm or less, the pressure loss can be further reduced when the honeycomb structure is used as a filter. The thickness of the partition wall is an average value measured by a method of observing a cross section in the central axis direction with a microscope.

The porosity of the cell walls constituting the honeycomb structure is preferably 30 to 70%, and more preferably 40 to 65% in view of ease of production. If the porosity of the partition wall is 30% or more, the pressure loss is easily reduced; if the porosity of the cell walls is 70% or less, the strength of the honeycomb structure can be maintained.

The average pore diameter of the porous partition walls is preferably 5 to 30 μm, and more preferably 10 to 25 μm. When the partition walls have an average pore diameter of 5 μm or more, the pressure loss can be reduced when the partition walls are used as a filter; if the average pore diameter of the partition walls is 30 μm or less, the strength of the honeycomb structure can be maintained. In the present specification, the terms "average pore diameter" and "porosity" mean the average pore diameter and the porosity measured by the mercury intrusion method.

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

Such a honeycomb structure is produced by forming a green body containing a ceramic material into a honeycomb shape having partition walls partitioning a plurality of cells to form a honeycomb formed body, drying the honeycomb formed body, and then firing the dried honeycomb formed body to produce the honeycomb structure, wherein the plurality of cells penetrate from one end face to the other end face to form fluid flow paths. When this honeycomb structure is used as the honeycomb structure of the present embodiment, the outer peripheral wall may be extruded integrally with the honeycomb structure portion and used as it is, or the outer peripheral wall may be formed by grinding the outer periphery of the honeycomb formed body (honeycomb structure) into a predetermined shape after molding or firing and applying a coating material to the honeycomb structure having the ground outer periphery to form an outer peripheral coating layer. In the honeycomb structure 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 formed of the coating material is formed as the outer peripheral wall positioned at the outermost periphery on the outer peripheral surface of the honeycomb structure, whereas in the latter case, the outer peripheral wall of the two-layer structure positioned at the outermost periphery on which the outer peripheral coating layer formed of the coating material is further laminated is formed on the outer peripheral surface of the honeycomb structure. The outer peripheral wall and the honeycomb structure portion may be extruded integrally and directly fired, and the outer peripheral wall may be used without processing the outer peripheral wall.

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 mass%, more preferably 0.1 to 0.2 mass%. Further, it is preferable to use 0.2 to 2.0 mass% of clay, and more preferable to use 0.4 to 0.8 mass% of clay.

The honeycomb structure is not limited to an integral honeycomb structure in which partitions are integrally formed, and for example, although not shown, a honeycomb structure (hereinafter, sometimes referred to as a "junction-type honeycomb structure") having a structure in which a plurality of columnar honeycomb cells each having a porous partition are combined with a junction material layer therebetween to define a plurality of cells, and the cells form flow paths for a fluid may be used.

In addition, the honeycomb structure may be: one open end of a predetermined cell among the plurality of cells and the other open end of the remaining cells are sealed by a sealing portion. The honeycomb structure can be used as a filter (honeycomb filter) for purifying exhaust gas. The plugged portions may be disposed after the outer peripheral coat layer is formed, or may be disposed in a state before the outer peripheral coat layer is formed, that is, in a stage of manufacturing the honeycomb structure.

The plugged portions may be configured in the same manner as the plugged portions used as the plugged portions of the conventionally known honeycomb structure.

In addition, the honeycomb structure of the present embodiment may be: the catalyst is supported on at least one of the surfaces of the partition walls and the insides of the pores of the partition walls. As described above, the honeycomb structure of the present embodiment may be configured as a catalyst carrier carrying a catalyst, or a filter (for example, a diesel particulate filter (hereinafter also referred to as "DPF")) provided with plugging portions for purifying particulate matter (carbon particulates) in exhaust gas.

The kind of the catalyst is not particularly limited, and may be appropriately selected depending on the purpose and use of the honeycomb structure. 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, an oxidation catalyst, or a three-way catalyst comprising a co-catalyst such as ceria or zirconia having a noble metal such as platinum (Pt), palladium (Pd) or rhodium (Rh) supported on the surface of alumina pores, or comprising an alkaline earth metal and platinumIs Nitrogen Oxide (NO)_x) NO of the storage component_xAbsorbing and storing the reduction catalyst. Examples of the catalyst not using a noble metal include: NO including copper-substituted zeolite or iron-substituted zeolite_xA selective reduction catalyst, and the like. 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 structures are used as honeycomb cells, and the side surfaces of the plurality of honeycomb cells are joined together with a joining material to form an integrated honeycomb structure in which the honeycomb cells are joined. The honeycomb structure in a state where the honeycomb units 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 end surfaces of each honeycomb unit.

Next, these honeycomb cells are adjacently disposed so that the side surfaces of the honeycomb cells face each other, and after the adjacent honeycomb cells are pressure-bonded to each other, heating and drying are performed. In this way, a honeycomb structure was produced in which the side surfaces of the adjacent honeycomb cells were joined to each other by a joining material. The honeycomb structure may be formed by grinding the outer peripheral portion to a desired shape (for example, a cylindrical shape), applying a coating material to the outer peripheral surface, and then heating and drying the coating material.

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 a ceramic powder, a dispersion medium (e.g., water), and additives such as a binder, a peptizer, and a foaming resin, which are added as necessary, can be used. The ceramic is preferably a ceramic containing at least 1 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.

Fig. 2 is a schematic view of an exhaust gas flow path of an exhaust gas purifying apparatus to which a honeycomb structure is attached. The flow path of the exhaust gas is defined by the metal pipe 2. An exhaust gas purifying device 6 is disposed in the enlarged diameter portion 2a of the metal pipe 2. The exhaust gas purification device 6 includes: a honeycomb structure 1; a coil wiring 4 spirally surrounding the outer periphery of the honeycomb structure 1; and a fixing member 5 for fixing the coil wiring 4 inside the metal pipe 2. The honeycomb structure 1 may carry a catalyst.

The coil wiring 4 is spirally wound around the outer periphery of the honeycomb structure 1. A configuration using 2 or more coil wires 4 is also conceivable. In response to the ON (ON) of the switch SW, the ac current supplied from the ac power supply CS flows to the coil wiring 4, and as a result, a magnetic field that periodically changes is generated around the coil wiring 4. The on and 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 to allow the ac current to flow to the coil wiring 4. It is also assumed that the control unit 3 turns on the switch SW regardless of the start of the engine (for example, in response to the operation of a heating switch pressed by a driver). The fixing member 5 is a heat-resistant member, and the fixing member 5 is provided for fixing the catalyst-carrying honeycomb structure 1 and the coil wiring 4 in the metal pipe 2.

The input power to be applied to the exhaust gas purifying device is preferably in the range of 1kW to 10kW from the viewpoint of heating performance. The heating frequency is preferably in the range of 10 to 500 kHz.

In this specification, the temperature of the honeycomb structure 1 is raised by a change in the magnetic field corresponding to the alternating current flowing through the coil wiring 4. Thereby, the carbon fine particles and the like trapped by the honeycomb structure 1 are burnedAnd (6) burning. In addition, 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 by the catalyst carrier included in the honeycomb structure 1, thereby promoting the catalytic reaction. Briefly, 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)。

Fig. 6 is a schematic diagram of the exhaust system 20 including the exhaust muffler 22 and the exhaust gas purification device 26 provided in the exhaust muffler 22. The exhaust muffler 22 is provided with a muffler. The muffler may be composed of a plurality of mufflers such as a main muffler and a sub-muffler. The exhaust gas purifying device 26 is mounted with the honeycomb structure 1, and has a coil wiring spirally wound around the outer periphery of the honeycomb structure 1 and a fixing member for fixing the coil wiring in the exhaust gas flow path. The exhaust system 20 includes an exhaust pipe 21, and the exhaust pipe 21 constitutes a flow path of the exhaust gas supplied to the exhaust muffler 22 or a flow path of the exhaust gas discharged from the exhaust muffler 22.

Fig. 7 shows a schematic view of an exhaust gas purification device 26 provided in the exhaust muffler 22 of the exhaust system 20. Fig. 7 is a partially enlarged view of the vicinity of the coil wiring 24 embedded in the holding mat 25 of the exhaust gas purifying device 26 for explaining the sound deadening function. In the exhaust system 20, the lower the temperature of the gas passing through the honeycomb structure 1, the smaller the deposition flow rate of the gas, and the smaller the gas velocity passing through the partition walls of the honeycomb structure 1. Therefore, from the viewpoint of ensuring the soot trapping efficiency, it is preferable to dispose the honeycomb structure 1 on the downstream side of the exhaust system 20 as much as possible. Further, it is preferable that the honeycomb structure 1 is provided inside a main muffler located at the most downstream side of the exhaust system 20 or an auxiliary muffler located at the front side thereof. When a conventional honeycomb structure is mounted in an exhaust muffler, only small pores of the partition walls of the honeycomb structure are blocked by liquid water due to capillary phenomenon due to condensation of water. As a result, there are problems that the high-speed gas concentrates on the large pores and flows, which deteriorates the soot trapping efficiency, and that the exhaust gas temperature is too low, which makes soot regeneration impossible. In contrast, since the honeycomb structure 1 can evaporate and remove water by electromagnetic dielectric heating, it can be heated to a temperature necessary for soot regeneration at the time of soot regeneration while maintaining a high soot trapping efficiency. Therefore, the problem that soot cannot be regenerated is unlikely to occur. The honeycomb structure 1 has pressure loss factors such as expansion and contraction of gas, passage of a porous body of gas, passage of cell channels, and the like, and these factors have a noise reduction effect. Thus, a part of the sound-deadening function in the muffler can be replaced. In order to enhance the effect of reducing high-frequency sound, it is more effective to enclose and attenuate high-frequency sound in the vicinity of the outer periphery of the exhaust muffler 22 as shown in fig. 7. As shown in fig. 7, the cells near the outer periphery of the honeycomb structure have a structure in which both ends are sealed, and the sound waves are less likely to leak in the axial direction. As shown in the enlarged portion of fig. 7, the sound wave propagating through the honeycomb structure 1 in the exhaust muffler 22 of the exhaust system 20 propagates through the gaps between the partition walls 112 and the partition walls 112 of the honeycomb structure 1, travels while being attenuated by the partition walls, and bounces off the outermost partition wall 112 in contact with the holding mat 25. This suppresses propagation of the sound wave to the outside. As shown in fig. 7, the honeycomb structure may be a honeycomb structure in which cells that are not sealed are penetrated, or may be a wall-flow filter in which both ends are alternately sealed. From the viewpoint of noise reduction effect, a wall-flow filter in which both ends are alternately sealed is more preferable.

(2. surface layer)

As shown in fig. 3, the honeycomb structure 1 has a surface layer 114 on at least a part of the surface of the partition walls 112. The surface layer 114 contains magnetic particles 116 and has air permeability.

Here, having air permeability means: the permeability of the surface layer was 1.0X 10^-13m²The above. From the viewpoint of further reducing the pressure loss, the permeability is preferably 1.0 × 10^-12m²The above. Since the surface layer has air permeability, pressure loss caused by the surface layer can be suppressed.

In the present specification, "permeability" refers to a physical property value calculated by the following formula (1), and indicates the passage of a predetermined gas through a substance (partition wall) when the gas passes through the substanceValue of an indicator of over-resistance. Here, in the following formula (1), C represents permeability (m)²) And F represents the gas flow rate (cm)³(s); T is the sample thickness (cm), and V is the gas viscosity (dynes sec/cm)²) D represents the sample diameter (cm), and P represents the gas Pressure (PSI). Note that, as for the numerical values in the following formula (1), 13.839(PSI) ═ 1(atm), 68947.6(dynes · sec/cm)²)＝1(PSI)。

[ mathematical formula 1]

In the case of measuring the permeability, the partition wall with the surface layer is cut out, the permeability is measured in the state with the surface layer attached, then the permeability is measured in the state with the surface layer cut out, and the permeability of the surface layer is calculated from the ratio between the surface layer and the thickness of the partition wall substrate and the result of the permeability measurement.

By containing the magnetic particles 116 in the surface layer 114, the honeycomb structure 1 is heated by electromagnetic induction. Therefore, it is not necessary to flow a current through the honeycomb structure 1 itself, and the occurrence of short circuits can be suppressed even in an environment where condensed water is generated. In addition, short-circuiting due to carbon deposition can be suppressed. In order to obtain the above-described effects, the surface layer 114 needs to be provided on at least a part of the surface of the partition walls 112 of the honeycomb structure 1. In fig. 3, both surfaces of the partition wall 112 are covered with the surface layer 114, but the surface layer 114 is not necessarily formed on both surfaces, and may be formed only on the surface where the first compartment 108 or the second compartment 110 is formed, for example. That is, the surface layer 114 preferably covers at least one side of the partition wall 112.

The surface layer 114 containing the magnetic particles 116 may be provided only at a portion where the soot regeneration effect is most likely to be exerted. For example, initial soot accumulation of gasoline particles often occurs near the outlet of the honeycomb structure 1. Therefore, the surface layer 114 may be provided only in the downstream side region of the honeycomb structural body 1. According to this configuration, only the portion where a large amount of soot is accumulated is heated, so soot combustion can be efficiently performed, and power consumption can be suppressed. It is particularly suitable for regenerating soot under a condition where no gas flows through the honeycomb structure 1 like when the vehicle is stopped. Further, since soot combustion is efficiently performed even in a situation where gas flows through the honeycomb structure 1, the surface layer 114 may be provided only in the central portion in the gas flow direction (the axial direction of the honeycomb structure 1). By heating the central portion in the gas flow direction, the soot in the downstream region of the honeycomb structure 1 having a large soot accumulation amount can be efficiently burned by utilizing the heat transfer effect by the gas.

The magnetic particles 116 are preferably formed of a magnetic material having a curie temperature. The curie temperature of the magnetic particles 116 is not particularly limited, and preferably exceeds 450 ℃. More preferably 800 ℃ or higher. If the curie temperature of the magnetic particles 116 exceeds 450 ℃, the honeycomb temperature sufficient for raising the catalyst temperature to the catalyst activation temperature or higher can be achieved. Examples of the composition of the magnetic particles 116 having a Curie temperature of more than 450 ℃ include Cr 18% Fe (Cr18 mass% stainless steel), Fe-Cr-Al alloy, Fe-Cr-Si alloy, Fe-Si-Ti alloy, Co-Fe-V alloy, Co-Ni-Fe alloy, Fe-Co-Nb alloy, Fe-Co-Cr-Mo alloy, FeOOF₂O₃、NiOFe₂O₃、CuOFe₂O₃、MgOFe₂O₃、MnBi、Ni、MnSb、MnOFe₂O₃、Y₃Fe₅O₁₂And the like. Examples of the magnetic particles having a curie temperature of 800 ℃ or higher include: Co-Fe alloy, Co-Fe-V alloy, Co-Ni-Fe alloy, Fe-Co-Nb alloy, Fe-Co-Cr-Mo alloy, and the like. The concrete components are as follows: 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, and the balance of Fe-20 mass% Co-1 mass% Cr-2 mass% V, the balance Fe-35 mass% Co-1 mass% Cr, pure cobalt, pure iron, electromagnetic soft iron, the balance Fe-0.1-0.5 mass% Mn, and the like. Preferably, a metal containing Co with a higher curie temperature is used.

The porosity of the surface layer 114 is preferably 50% or more, more preferably 60% or more, and still more preferably 70% or more. By having a porosity of 50% or more, the pressure loss can be suppressed. However, if the porosity is too high, the surface layer becomes brittle and easily peels off, and therefore, it is preferably 90% or less.

As a method for measuring the porosity of the surface layer 114 by the mercury intrusion method, the difference between the mercury porosity curve of the base material on which the surface layer is formed and the mercury porosity curve of the base material alone from which only the surface layer is scraped off is regarded as the mercury porosity curve of the surface layer, and the porosity of the surface layer is calculated from the scraped-off mass and the mercury porosity curve. The porosity of the surface layer may be calculated from the area ratio of the voids and the individual portions by taking SEM images and analyzing the images of the surface layer portion.

The average pore diameter of the surface layer 114 is preferably 10 μm or less, more preferably 5 μm or less, still more preferably 4 μm or less, and particularly preferably 3 μm or less. By setting the average pore diameter to 10 μm or less, a high particle collection efficiency can be achieved. However, if the average pore diameter of the surface layer 114 is too small, the pressure loss increases, and therefore, it is preferably 0.5 μm or more.

As a method for measuring the average pore diameter of the surface layer 114 by the mercury intrusion method, a peak value in a mercury porosimeter is used, and a difference between a mercury porosity curve (pore volume frequency) of a substrate on which the surface layer is formed and a mercury porosity curve unique to the substrate from which only the surface layer 114 is scraped is defined as a mercury porosity curve of the surface layer, and the peak thereof is defined as the average pore diameter. Alternatively, an SEM image of a cross section of the honeycomb structure may be taken, and image analysis of the surface layer portion may be performed to binarize the void portion and the individual portion, and voids of 20 or more may be randomly selected, and the average value of inscribed circles thereof may be set as the average pore diameter.

The weight average particle diameter of the magnetic particles 116 in the surface layer 114 is preferably 20 μm or less. By setting the weight average particle diameter to 20 μm or less, it is possible to fall within a range that all of the target average pore diameter, thickness, and porosity of the surface layer satisfy, in combination with other design factors that can be controlled. The lower limit of the weight average particle diameter of the magnetic particles 116 is not particularly limited, and may be, for example, 0.5 μm or more. The weight average particle diameter was measured by a laser diffraction particle size distribution measuring apparatus.

In fig. 3, the thicknesses of the surface layer 114 and the partition walls 112 are the same, but the thickness of the surface layer 114 is not particularly limited. However, in order to obtain the effect of the surface layer 114 more remarkably, the thickness of the surface layer 114 is preferably 10 μm or more. On the other hand, the thickness of the surface layer 114 is preferably 80 μm or less from the viewpoint of avoiding an increase in pressure loss. The thickness of the surface layer 114 is more preferably 50 μm or less. As a method for measuring the thickness of the surface layer, for example, the honeycomb structure having the surface layer formed thereon is cut in a direction perpendicular to the direction in which the cells extend, and the thickness of the surface layer is measured from the cross section thereof, and an average value of the thickness measurement values at arbitrary 5 points is obtained.

In addition, the magnetic particles are preferably: the shortest diameter d of the magnetic particles 116 is 0.1 to 5 μm, and L/d is not less than 3 when the longest diameter of the magnetic particles 116 is L μm. This can ensure sufficient air permeability while maintaining electrical conductivity, and can ensure a microstructure of the surface layer having high soot trapping efficiency. The shortest diameter d can be obtained by analyzing an image of the SEM captured image, and for 50 particles, the longest line segment among line segments orthogonal to the longest diameter of the particle is defined as the shortest diameter of the particle, and the shortest diameter d is obtained by averaging the number of particles. The length can be calculated by averaging the longest diameters of 50 or more particles by the number of particles in the SEM image, thereby obtaining the longest diameter L. Preferably, the magnetic particles 116 are needle-shaped or scaly. Acicular means L/d.gtoreq.5. The scale-like shape means that the ratio L/t of the thickness t to the longest diameter L of the magnetic particles 116 is greater than 5. The thickness t of the magnetic particles 116 can be obtained by analyzing the image of the SEM captured image, measuring the thickness of the portion where the thickness of the particles is the largest for 50 particles, and averaging the thicknesses by the number of particles.

A stress relaxation layer having a thermal expansion coefficient between the thermal expansion coefficient of the surface layer 114 and the thermal expansion coefficient of the partition wall 112 is preferably provided between the surface layer 114 and the partition wall 112. This can prevent cracking or the like due to the difference in thermal expansion coefficient between the surface layer 114 and the partition wall 112, and improve thermal shock resistance. The composition of the stress relaxation layer is not particularly limited, and for example, a low expansion glass layer, an alumina layer, a silicon dioxide layer, or a ceria layer can be preferably used.

(3. method for producing Honeycomb Structure)

Hereinafter, a method for manufacturing the honeycomb structure 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 containing cordierite is manufactured, a cordierite forming raw material is first prepared as a raw material for a body. The cordierite forming raw material contains silica source component, magnesia source component, 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 and magnesite. Among them, talc is preferable. Preferably, 37 to 43 mass% of talc powder is contained in the cordierite forming raw material. The particle diameter (average particle diameter) of the talc powder 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. The cordierite forming raw material preferably contains 10 to 30 mass% of aluminum hydroxide and 0 to 20 mass% of alumina.

Next, a material (additive) for clay 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 a resin (particularly, a particulate resin), 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 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 diameter) is preferably 10 to 200 μm. The shape of the low melting point reaction substance is preferably spherical, rhomboidal, or flattened, because the shape of the fine pores can be easily controlled.

Examples of the binder include hydroxypropylmethylcellulose, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, and polyvinyl alcohol. Examples of the dispersant include dextrin and polyol. Examples of the surfactant include fatty acid soaps. The additive may be used singly or in combination of two or more.

Then, a binder, a pore-forming agent, a dispersant, and water are mixed in a ratio of 3 to 8 parts by mass of the binder, 3 to 40 parts by mass of the pore-forming agent, 0.1 to 2 parts by mass of the dispersant, and 10 to 40 parts by mass of water to 100 parts by mass of the cordierite forming raw material, and these materials for the clay are kneaded to prepare a clay.

Next, the prepared clay is molded into a honeycomb shape by extrusion molding, injection molding, press molding, or the like to obtain a green honeycomb molded article. The extrusion molding method is preferably used because continuous molding is easy and, for example, cordierite crystal orientation can be achieved. The extrusion molding method can be carried out by using a vacuum pug mill, a ram-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 order to dry the entire product quickly and uniformly, it is preferable to dry the product by combining hot air drying with microwave drying or dielectric drying.

Next, a material for the plugging portion is prepared. The plugging portion may be made of the same clay material as the partition walls (dried honeycomb body) or may be made of a different material (plugging slurry). 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 needed, making a slurry, and kneading the slurry using a mixer or the like.

Next, a mask was applied to a part of the cell openings on 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 no mask was applied were filled with the plugging slurry. Similarly, a mask is applied to a part of the cell openings on the other end face of the honeycomb dried body, the end face is immersed in a storage container storing the plugging slurry, and the cells to which the mask is not applied are filled with the plugging slurry. Then, the honeycomb structure is dried and fired to obtain a honeycomb structure having plugged portions. The drying conditions may be the same as those for drying the honeycomb formed body. In addition, the firing conditions are generally such that when a cordierite forming raw material is used, firing is performed at 1410 to 1440 ℃ for 3 to 15 hours in an atmospheric atmosphere.

In the case where the honeycomb structure obtained 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 a state in which the outer peripheral wall is removed. In the subsequent step, a coating material is applied to the outer periphery of the honeycomb structure from which the outer peripheral wall has been removed, thereby forming 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 layer may be formed on the part by the coating material.

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

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

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 the drying heat treatment can be effectively suppressed.

As a method for applying the coating material, for example, a method of applying the coating material by placing the honeycomb structure on a rotary table and rotating the rotary table while pressing the coating nozzle along the outer peripheral portion of the honeycomb structure while ejecting the coating material from the blade-shaped coating nozzle is given. With such a configuration, the coating material can be applied in a uniform thickness. In addition, the surface roughness of the formed outer peripheral coating layer is reduced, and an outer peripheral coating layer which is excellent in appearance and is less likely to be broken by thermal shock can be formed.

When the outer peripheral wall of the honeycomb structure is removed by grinding the outer peripheral surface, a coating material is applied to the entire outer peripheral surface of the honeycomb structure to form an outer peripheral coating layer. On the other hand, when the outer peripheral wall is present on the outer peripheral surface of the honeycomb structure or a partial outer peripheral wall is removed, the outer peripheral coat layer may be formed by applying the coating material partially, or the outer peripheral coat layer may be formed by applying the coating material over the entire 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 removing the moisture and organic substances by holding at 600 ℃ for 1 hour or more in an electric furnace.

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 forming the outer peripheral coating layer.

In addition, since the obtained honeycomb structure is colored by irradiating the outer peripheral surface thereof with laser light, the outer peripheral coating layer of the obtained honeycomb structure can be irradiated with laser light to print (mark) product information and the like.

Examples of the laser light used for marking with laser light include carbon dioxide gas (CO)₂) Laser, YAG laser, and YVO4 laser are preferable examples. The laser conditions for irradiating the laser beam may be appropriately selected depending on the type of the laser beam used, and for example, CO is used₂In the case of laser, the marking is preferably performed at an output power of 15 to 25W and a scanning speed of 400 to 600 mm/s. By performing labeling in this manner, the irradiated portion is colored so as to appear a dark color of black to green, and the contrast due to the color development between the non-irradiated portion is very good.

When a catalyst is supported on the honeycomb structure, the printed portion does not deteriorate even after the printing by the laser, and the printed portion can be recognized well even after the catalyst is supported. The method for supporting the catalyst is not particularly limited, and the method for supporting the catalyst may be performed according to a method for supporting the catalyst performed in a conventional method for producing a honeycomb structure.

A surface layer containing magnetic particles and having air permeability is formed on at least a part of the surface of a cell of a honeycomb structure. As described above, the surface layer preferably covers at least one surface of the partition wall. As a method of forming the surface layer, there are mainly the following 3 methods.

A method of forming a coating film by flowing a slurry containing magnetic particles and a binder mainly composed of metal or glass into a cell of a honeycomb structure, and heating the coating film at a temperature equal to or higher than the melting point of the metal or the softening point of the glass to form a surface layer.

A method of forming a coating film by flowing a slurry containing magnetic particles and a binder mainly composed of silica or alumina into a cell of a honeycomb structure, and heating the coating film to cure the silica or alumina to form a surface layer.

A method of forming a coating film by flowing a gas containing magnetic particles and the binder or the binder into a cell of the honeycomb structure or flowing a gas containing only magnetic particles into a cell of the honeycomb structure, and heating the coating film to form a surface layer.

The slurry may be flowed into the cells of the honeycomb structure, for example, by flowing the slurry into the cells of the honeycomb structure or by immersing the slurry in the cells of the honeycomb structure. When a binder mainly composed of metal or glass is used, the honeycomb substrate is preferably melted or softened once at the heat-resistant temperature or lower during production, and therefore the coating film is preferably heated at a temperature equal to or higher than the melting point or softening point of the binder. In addition, in the use environment of the honeycomb structure, the maximum temperature reaches about 700 ℃, and therefore, it is more preferable to use a metal or glass having a melting point or a softening point of the temperature or higher. The specific melting point or softening point is, for example, 800 to 1200 ℃. On the other hand, when an adhesive material containing silica or alumina as a main component is used, it is preferable that the adhesive material be cured by heat drying during production. Examples of the substance capable of curing the binder by heating and drying include colloidal dispersions of silica and alumina, and colloidal dispersions containing silica and alumina.

Further, since the highest temperature in the use environment of the honeycomb structure reaches about 700 ℃, it is more preferable to use silica or alumina having a heat resistance temperature higher than that. After the slurry is poured into the cells of the honeycomb structure, a suction tool is attached to the downstream of the honeycomb structure, and suction is performed from the downstream of the honeycomb structure, that is, the other open end side, to remove excess water, thereby forming a coating film. The condition for heating the coating film is preferably heating at 800 to 1200 ℃ for 0.5 to 3 hours.

In the case of using a binder mainly composed of alumina or silica, the step of flowing the slurry into the cell may be performed at the stage of forming and drying the honeycomb. In this case, after the slurry is poured into the cells, the honeycomb structure before the formation of the surface layer is dried, and then, in the firing step of the honeycomb structure, the step of fixing the magnetic particles to the binder to form the surface layer is performed simultaneously. The silica or alumina preferably exhibits an effect of curing by drying.

In addition to the above-described binder mainly composed of metal or glass, the magnetic particles may be coated with a binder mainly composed of metal or glass in advance. Further, a step of forming composite particles including the magnetic particles and the binder may be provided.

For example, a slurry can be obtained by mixing magnetic particles, the binder or the binder, an organic binder, and water or alcohol. Further, fats and oils and surfactants may be further added to the slurry, and the mixture may be mixed and emulsified. In addition, a pore former for controlling the porosity of the surface layer may be mixed into the slurry. As the pore-forming agent, for example, resin particles, starch particles, carbon particles, etc. having a particle diameter of 0.5 to 10 μm can be used.

As a method for making the gas containing magnetic particles and the binding material or the binding material flow into the honeycomb structure, for example, the gas containing magnetic particles is made to flow at 0.005-0.4L/cm²The magnetic particles are blown into the cells, thereby depositing the magnetic particles in a floating state on the surfaces of the partition walls. Then, the magnetic particles are thermally bonded and fixed to the surfaces of the partition walls by heat treatment at 800 to 1200 ℃ for 0.5 to 3 hours, for example, to form a surface layer. In addition, only the magnetic body is includedWhen the gas containing particles flows into the cells of the honeycomb structure, the gas containing magnetic particles is supplied at a rate of 0.005 to 0.4 liter/cm²Blowing the magnetic particles into the compartment, depositing the magnetic particles in a floating state on the surface of the partition wall, and then performing heat treatment at 1280 to 1330 ℃ for 0.5 to 3 hours to thermally bond and fix the magnetic particles on the surface of the partition wall, thereby forming a surface layer.

In the above-described method of flowing the slurry or gas into the cells of the honeycomb structure, including the method of flowing only the magnetic particles into the cells without using the binder or the adhesive, the organic binder may be mixed with the slurry or the gas. By adding the organic binder, the coating film can be preliminarily fixed at a stage prior to the step of forming the surface layer by heating. The organic binder is preferably a material that is removed by oxidation in an oxidizing atmosphere at a temperature not higher than the temperature of the step of forming the surface layer by heating, that is, not higher than 800 ℃. In addition, it is preferable to use the same binder as the binder used as the pore-forming agent in the production of the honeycomb structure.

Examples

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(preparation of Honeycomb Structure)

[ production of plugged Honeycomb Structure ]

Alumina, aluminum hydroxide, kaolin, talc and silica were used as cordierite raw materials, and 13 parts by mass of a pore-forming agent, 35 parts by mass of a dispersion medium, 6 parts by mass of an organic binder and 0.5 part by mass of a dispersant were added to 100 parts by mass of the cordierite raw material, and the mixture was mixed and kneaded to prepare a clay.

Water was used as a dispersion medium, coke having an average particle diameter of 10 μm was used as a pore-forming agent, hydroxypropylmethylcellulose was used as an organic binder, and ethylene glycol was used as a dispersant. Next, the kneaded material was extrusion-molded using a predetermined mold, thereby obtaining a honeycomb molded body having a rectangular cell shape and a cylindrical (cylindrical) overall shape.

Then, the honeycomb formed body was dried by a microwave dryer, further completely dried by a hot air dryer, and then both end surfaces were cut to adjust to a predetermined size, thereby obtaining a honeycomb dried body. Next, masks are alternately applied in a checkered pattern to the cell openings on one end face of the honeycomb dried body, and the end portion on the side to which the masks are applied is immersed in a sealing slurry containing a cordierite forming raw material, thereby forming sealing portions alternately arranged in a checkered pattern. In the other end portion, a mask is applied to the cells having one end portion sealed, and the sealed portion is formed by the same method as the method for forming the sealed portion at one end portion. Then, the honeycomb structure is dried by a hot air dryer and fired at 1410 to 1440 ℃ for 5 hours to obtain a plugged honeycomb structure (honeycomb carrier).

(example 1)

Magnetic particles, resin particles having a weight average particle size of 3 μm, and a glass containing silica having a weight average particle size of 5 μm as a main component as a binder were prepared by mixing 80: 10: 10 mass ratio of the resulting powder. In the honeycomb structure produced in the above-described procedure, the powder is allowed to flow through the honeycomb structure with the air flow from one end surface side of the honeycomb structure, and deposited on the surfaces of the partition walls thereof to form a coating film. The coating film was heat-treated at 950 ℃ for 1hr in the air at a temperature equal to or higher than the softening point of the glass, whereby resin particles were burned off, and glass mainly composed of silica was melted to fix the particles to the partition wall surface, thereby forming a surface layer.

(example 2)

A needle-like magnetic material having a length L of 10 μm and a length L/d of 1.00, a silica-based adhesive material which is a dry-cured adhesive material, an organic binder, and water were mixed at a mass ratio of 85: 10: 5: 500, and mixing to prepare slurry. The slurry is atomized by spraying and sucked together with air from the end of the honeycomb structure, so that the slurry is deposited on the surfaces of the partition walls and dried to form a coating film. Then, heat treatment was performed at 600 ℃ for 1hr in the atmosphere to burn off the organic binder, and heat treatment was performed at 1000 ℃ for 1hr in the atmosphere to cure the silica or alumina to form a surface layer.

(example 3)

A needle-like magnetic material having a length L of 20 μm and a length L/d of 4.00, a binder composed mainly of silica solidified by drying as a binder, an organic binder, water, a fat and oil, and a surfactant were mixed at a mass ratio of 85: 10: 5: 500: 10: 2, mixing to prepare the emulsified raw materials. The emulsified material is atomized by spraying, and sucked together with air from the end of the honeycomb structure, thereby being deposited on the surfaces of the partition walls and dried to form a coating film. Then, heat treatment was performed at 600 ℃ for 1hr in the atmosphere to burn off the organic binder, and heat treatment was performed at 1000 ℃ for 1hr in the atmosphere to cure the silica or alumina to form a surface layer.

(example 4)

One open end of the honeycomb structure as an inlet end face was faced upward, a slurry tank for storing slurry was installed above the inlet end face, and slurry for forming a surface layer (magnetic particles as aggregate, SiO as binder particles) was put in the slurry tank₂、Al₂O₃And glass powder containing MgO as a main component). Then, the slurry is allowed to enter the honeycomb structure, and thereafter, the slurry is sucked from the other opening end side, which is downstream of the honeycomb structure, to remove excess water, thereby forming a coating film. Then, the coating film was dried and bonded at 950 ℃ to a temperature equal to or higher than the softening point of the glass powder, thereby forming a surface layer.

(example 5)

0.5 part by mass of carboxymethylcellulose as an organic binder was dissolved in 95 parts by mass of water, and 2.5 parts by mass of magnetic particles (Cr18 mass% stainless steel) having a shortest diameter d of 10 μm and a longest diameter L of 10 μm as an aggregate powder and SiO as a binder were added to the aqueous solution in this order₂、Al₂O₃5 parts by mass of a colloidal dispersion (solid content: 40%) of a glass powder containing MgO as a main component was stirred to prepare a slurry for forming a surface layer. Then, the inlet side of the honeycomb structure was faced downward to leave a height corresponding to the depth of the outlet plugging materialThe slurry for forming the surface layer is dipped in the slurry for forming the surface layer, and then lifted up to form a coating film. Thereby, the inner surface of the inlet open compartment is dip coated with slurry. After drying, the coating film was heat-treated at 900 ℃ for 0.5 hour at a temperature equal to or higher than the softening point of the glass powder, thereby forming a surface layer.

(example 6)

Magnetic particles having a longest diameter of L10 μm were supplied to the honeycomb structure together with air, a pore-forming agent, and a glass powder containing silica as a main component as a binder, and deposited on the partition walls to form a coating film. In this case, the porosity and average pore diameter of the surface layer can be controlled by appropriately setting conditions such as the particle size and particle size distribution of the pore former, the amount of addition, and the amount of supplied air. Here, starch was used as the pore former. Further, by making the partition wall portions in a predetermined region such as an upstream region and a downstream region of the honeycomb structure contain alcohol, water, resin, or the like, the permeation resistance of air can be increased, and thereby the deposition region of the supplied surface layer forming raw material and pore-forming agent can be controlled. For example, the porosity and average pore diameter of the surface layer are changed by adjusting the amount of the pore-forming agent to 3 to 45 parts by mass, the median particle diameter D50 of the pore-forming agent to 0.7 to 8.0. mu.m, the sharpness index of the particle size distribution as the pore-forming agent to 0.4 to 1.9, and the flow rate of the fluid to 2000 to 8000L/min. The coating film was heat-treated at 950 ℃ for 1hr in the air at a temperature equal to or higher than the softening point of the glass powder, thereby forming a surface layer.

(examples 7 and 8)

A surface layer was formed on the honeycomb structure in the same manner as in example 6, except that magnetic particles having the longest diameter L and the shortest diameter d shown in table 1 were used.

(example 9)

A surface layer was formed on the honeycomb structure in the same manner as in example 1 except that magnetic particles having the compositions shown in table 1 were used.

(examples 10, 11, 12, 13 and 14)

A surface layer was formed on the honeycomb structure in the same manner as in example 6 except that the flaky magnetic particles having the thicknesses of the longest diameter L and the shortest diameter d shown in table 1 were used.

Table 1 shows the characteristics of the honeycomb structure obtained in each example.

[ Table 1]

The honeycomb structure of example 7 was subjected to a heating test using a dielectric heating apparatus. The temperature raising performance of the honeycomb structure was compared with each other by using 4kW of power and 30kHz, 85kHz, and 350kHz of dielectric heating frequency. When the dielectric heating frequency was 30kHz or 85kHz, the coil was wound around the outer periphery of the honeycomb structure for 6 cycles; when the dielectric heating frequency was 350kHz, the coil was wound around the outer periphery of the honeycomb structure for 3 cycles. The unloaded inductance of the coil used at 30kHz and 85kHz was 2.5 muH, and the unloaded inductance of the coil used at 350kHz was 1.0 muH. The capacitor combined with the coil was selected to have a capacitance of 10 μ F in the 30kHz test, 1.3 μ F in the 85kHz test, and 0.2 μ F in the 350kHz test. For the transformer, a turn ratio of 20 was used at the test of 30kHz and 85 kHz: 1, using a turns ratio of 7: 1 transformer.

Although a sufficient heating rate could not be obtained at a dielectric heating frequency of 30kHz, heating to 500 ℃ in 90 seconds was confirmed at a dielectric heating frequency of 350 kHz. Fig. 4 shows graphs showing the relationship between time (seconds) and temperature (deg.c) at dielectric heating frequencies of 30kHz, 85kHz, and 350kHz in the heating test.

A heating test was performed on the honeycomb structure of example 12 by using a dielectric heating apparatus in the same manner. The power input was 4kW, the dielectric heating frequency was 350kHz, and the temperature raising performance of the honeycomb structure was compared with that of example 7. The combination of the coil, the capacitor and the transformer in the dielectric heating test of 350kHz in example 12 is the same as that in example 7. Fig. 5 shows a graph showing a relationship between time (seconds) and temperature (deg.c) in the heating test.

Confirming that: by using an alloy having a high curie point (Fe-49 Co-2V alloy), the honeycomb structure can be heated to 700 ℃ even in the absence of the heat of oxidation of the catalyst.

In any of the embodiments, heating can be performed by using the exhaust gas purification apparatus shown in fig. 2. In addition, no short circuit occurred during heating.

In light of the foregoing, those skilled in the art will be able to make various modifications to the embodiments.

Description of the symbols

1 Honeycomb Structure

2 Metal tube

3 control part

4. 24 coil wiring

5 fixing part

6. 26 exhaust gas purifying device

13 hole sealing part

20 exhaust system

21 exhaust pipe

22 exhaust silencing and sound reducing device

25 holding pad

102 peripheral wall

104 first end face

106 second end face

108 first compartment

110 second compartment

112 bulkhead

114 surface layer

116 magnetic particles