Metal honeycomb body, catalyst converter, and method for producing metal honeycomb body

Abstract

To provide a plug for a core hollow portion that does not disturb light off performance, plug shape retention performance and so on.SOLUTION: A metal honeycomb body has a core hollow portion formed of rolled flat and corrugated metal foils, wherein one end of either the flat foil or the corrugated foil has a notched shape that extends at least partially toward the core hollow portion, and a plug made of a porous material is accommodated at least at one end of the core hollow portion, the plug being supported by the notched shape within the core hollow portion.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a metal honeycomb body having a hollow core. [Background technology]

[0002] A metal honeycomb body, which is formed by winding flat and corrugated metal foils around a predetermined axis, is known as a purification device for purifying vehicle exhaust gases. When the flat and corrugated metal foils are wound, a hollow core is formed in the center of the metal honeycomb body. Because the hollow core has low purification performance, there is a need to reduce the amount of exhaust gas that flows into the hollow core.

[0003] Patent document 1 discloses a technology for a metal catalyst carrier using a metal honeycomb body formed by winding flat and corrugated metal foils, in which a metal plug that obstructs the flow of gas is disposed in the hollow portion of the winding core.

[0004] Patent document 2 discloses a technology for providing a regulating section in a metal honeycomb body formed by winding flat and corrugated metal foils, in which the space between the starting ends of the two metal foils at the axial end of the hollow core is widened to regulate the flow of exhaust gas in the hollow core. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-281118 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-201413 Summary of the Invention [Problem to be solved by the invention]

[0006] The metal honeycomb body of Patent Document 1 uses a dense metal plug, which increases the heat capacity of the metal honeycomb body and deteriorates its light-off performance (the temperature characteristic at which the purification performance of the catalyst is expressed). Although the heat capacity can be reduced by shortening the length of the plug, the joining length of the plug to the hollow part of the winding core is insufficient, making it impossible to maintain the durability of the plug.

[0007] The metal honeycomb body of Patent Document 2 has a method of providing restricting portions by processing metal foil, so the heat capacity does not increase, but the durability of the restricting portions is insufficient due to insufficient strength. [Means for solving the problem]

[0008] In order to solve the above problems, the metal honeycomb body of the present invention is characterized in that (1) in a metal honeycomb body having a hollow portion of a winding core formed by winding flat foil and corrugated foil made of metal foil, a cutout-shaped portion is formed at the end of one of the flat foil and corrugated foil metal foils, at least a portion of which extends toward the hollow portion of the winding core, a plug made of a porous body is placed in at least one end of the hollow portion of the winding core, and the plug is supported by the cutout-shaped portion inside the hollow portion of the winding core.

[0009] (2) The metal honeycomb body described in (1) above, characterized in that the cutout shape portion comprises an internal cutout shape portion located inside the hollow portion of the winding core and an external cutout shape portion located outside the hollow portion of the winding core, and the external cutout shape portion is covered by metal foil other than the end portion of one of the metal foils wound around the hollow portion of the winding core.

[0010] (3) The metal honeycomb body according to (1) or (2) above, wherein the plug has a structure in which a number of metal pieces are joined with a brazing material.

[0011] (4) The metal honeycomb body according to (1) or (2) above, wherein the plug is composed of a number of metal pieces and an inorganic adhesive that bonds adjacent metal pieces together.

[0012] (5) The metal honeycomb body according to (1) or (2) above, wherein the porosity of the plugs is 7% or more and 85% or less.

[0013] (6) The metal honeycomb body described in (3) above, characterized in that the metal pieces are made of the same material as the metal foil, and the brazing material is made of the same material as the brazing material used to join the flat foil and the corrugated foil.

[0014] (7) The metal honeycomb body according to (1) or (2) above, wherein the axial length of the plug is from 1 to 3 times the diameter of the hollow portion of the winding core.

[0015] (8) A catalytic converter comprising: the metal honeycomb body according to claim 1, on which a catalyst is supported; and an outer casing in which the metal honeycomb body is housed.

[0016] (9) A method for manufacturing a metal honeycomb body as described in (1) above, comprising: a base material supply step of supplying a slurry base material containing brazing material and a large number of metal pieces from the end of the hollow portion of the winding core toward the cutout shape portion; and a firing step of firing the metal honeycomb body after the base material supply step, wherein in the base material supply step, when the total content of the metal pieces in the slurry base material is X mass% and the total content of the brazing material is Y mass%, the ratio of X mass% to Y mass%, X:Y, is within the range of 3:7 to 9:1. [Effects of the Invention]

[0017] According to the present invention, by disposing a porous plug at at least one end of the hollow portion of the winding core, it is possible to prevent exhaust gas from escaping from the hollow portion of the winding core, thereby improving the steady-state purification performance of the metal honeycomb body. Furthermore, because the plug placed in the hollow portion of the winding core is made of a porous material, the heat capacity of the metal honeycomb body can be reduced compared to when a dense plug is used. This improves the light-off performance of the metal honeycomb body. Furthermore, the shape retention of the plug can be improved compared to methods that restrict the inflow of exhaust gas by processing metal foil. Furthermore, because the porous body is supported by the cutout portion, it can be prevented from falling out. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 2 is a plan view of the catalytic converter. [Figure 2] FIG. 3 is a cross-sectional view of a hollow portion of the winding core. [Figure 3] FIG. 10 is an explanatory diagram for explaining a method for manufacturing a wound body. [Figure 4] This is a comparative example corresponding to FIG. [Figure 5] 10 is a photograph of a comparative example. [Figure 6] FIG. 1 is a schematic diagram of a porous plug. DETAILED DESCRIPTION OF THE INVENTION

[0019] Figure 1 is a plan view of a catalytic converter according to one embodiment of the present invention, viewed from the axial direction. However, the porous plug disposed in the hollow portion of the winding core is not shown. The axial direction (normal to the paper surface) corresponds to the flow direction of exhaust gas flowing toward the catalytic converter. FIG. 2 is a cross-sectional view of the hollow portion of the winding core of the catalytic converter, showing the position of the porous plug.

[0020] The catalytic converter 1 includes a metal honeycomb body 4 carrying a catalyst and an outer casing 5. However, the outer casing 5 may be omitted. The metal honeycomb body 4 is a wound body formed by overlapping and winding flat foil 2 and corrugated foil 3, and overlapping the flat foil 2 and the corrugated foil 3 forms a gas conduction path for conducting exhaust gas. A winding core hollow portion 6 extending cylindrically in the axial direction is formed in the center of the metal honeycomb body 4. A cutout shape portion 21 (internal cutout shape portion 21a) extends from the winding core hollow portion 6, and this cutout shape portion 21 is positioned away from the axial end of the metal honeycomb body 4. The catalytic converter 1 of this embodiment can be used as a purification device for purifying vehicle exhaust gas.

[0021] The flat foil 2 and the corrugated foil 3 can be made of a metal foil made of a heat-resistant alloy. The lower limit of the foil thickness of the metal foil is preferably 20 μm. The upper limit of the foil thickness of the metal foil is preferably 100 μm, and more preferably 70 μm. By using a metal foil with such a thin foil thickness, the temperature rise rate of the metal honeycomb body 4 can be increased during exhaust gas purification, thereby activating the catalyst and reducing the weight of the catalytic converter 1.

[0022] The lower limit of the metal foil width is preferably three times the diameter of the hollow portion 6 of the winding core, which will be described later. The upper limit of the metal foil width is preferably 500 mm. The size of the metal foil can be changed as appropriate depending on the application of the catalytic converter 1. The corrugated foil 3 can be produced by, for example, corrugating the metal foil.

[0023] For example, various heat-resistant stainless steels containing Al in their alloy composition can be used for the metal foil. Ferritic stainless steel (in other words, Fe-20Cr-5Al alloy) consisting of 20% by mass of Cr, 5% by mass of Al, and the remainder being Fe and unavoidable impurities can be used as the stainless steel. However, stainless steels other than these (for example, stainless steels containing 15-25% by mass of Cr and 2-8% by mass of Al) can also be used.

[0024] A brazing filler metal can be used to join the flat foil 2 and the corrugated foil 3 and to join the metal honeycomb body 4 and the outer casing 5. For example, a Ni-based brazing filler metal with high heat resistance can be used as the brazing filler metal. The brazing filler metal may be foil brazing filler metal or powder brazing filler metal.

[0025] The catalyst can be supported on the metal foil by applying a predetermined washcoat liquid to the surface of the metal foil of the metal honeycomb body 4, and then drying and baking the liquid. The method for applying the washcoat liquid will be described later.

[0026] The outer cylinder 5 can be made of ferritic stainless steel containing 13% by mass or more and 20% by mass or less of Cr, such as SUS436L or SUS430. The lower limit of the wall thickness of the outer cylinder 5 is preferably 0.5 mm, and the upper limit of the wall thickness of the outer cylinder 5 is preferably 3 mm. The lower limit of the cell density of the metal honeycomb body 4 is preferably 15.5 cells per square centimeter (or 100 cells per square inch). The upper limit of the cell density of the metal honeycomb body 4 is preferably 93 cells per square centimeter (or 600 cells per square inch).

[0027] 3 is an explanatory diagram for explaining a method for manufacturing a wound body. A core rod 60 is formed in a cylindrical shape and is used to manufacture a wound body. A slit portion 61 extending in the radial direction is formed in the core rod 60.

[0028] At the end of the flat foil 2, a cutout portion 21 is formed by reducing the width of the metal foil, and a portion of this cutout portion 21 is inserted into the slit portion 61. Of the cutout portion 21, the portion sandwiched between the slit portion 61 is defined as the internal cutout portion 21a, and the portion located outside the slit portion 61 is defined as the external cutout portion 21b. Furthermore, the portion of the flat foil 2 other than the cutout portion 21 is defined as the flat foil main body portion 22. In Figure 3, the starting end where the cutout portion 21 begins is indicated by a dashed line B, and the area of ​​the corrugated foil 3 that is overlapped on the flat foil 2 is indicated by hatching. Note that the "B" in the dashed line B is an abbreviation for "border."

[0029] In the state shown in FIG. 3 , the core rod 60 is rotated around its axis to wrap the outer cutout portion 21b around the core rod 60. The core rod 60 is further rotated around its axis so that the corrugated foil 3 is inside the flat foil 2, and the flat foil main body 22 is wrapped around the outer cutout portion 21b. The distance K between the starting end B and the starting end of the corrugated foil 3 can be set to an appropriate length to cover the cutout portion of the cutout portion 21 (hereinafter also referred to as the non-foil portion S). By satisfying this condition, the entire corrugated foil 3 can be in contact with the flat foil main body 22, and the location where the plug is to be installed can be inside the flat foil main body 22. In other words, if the distance K is too short, the starting end of the corrugated foil 3 will contact the core rod 60 instead of the flat foil 2, thereby reducing the gas conduction path. The distance K is preferably equal to or greater than the circumference of the core rod 60 (diameter D×π). If the corrugated foil 3 is wound on the outside, the distance K may be less than the diameter D x π, but it is more advantageous from a manufacturing standpoint to place the corrugated foil 3 on the inside of the flat foil 2 and wind it, as this allows the corrugated foil 3 to be wound in a manner that sandwiches it between the flat foil 2.

[0030] After the desired wound body is obtained by winding the flat foil 2 and the corrugated foil 3 around the core rod 60, the core rod 60 is removed. This allows the production of a metal honeycomb body 4 having a winding core hollow portion 6 and having the cutout portion 21 extending into the interior of the winding core hollow portion 6.

[0031] A plug slurry (corresponding to a slurry base material) is prepared by mixing a large number of metal pieces 31 (see FIG. 6 ) and a brazing material in fragments or powder form in a liquid with appropriate viscosity, and this plug slurry is poured from one end side of the winding core hollow portion 6 toward the cutout portion 21, followed by drying and firing, thereby providing a porous plug 30 at one end of the winding core hollow portion 6. In this embodiment, the region into which the plug slurry is poured is cylindrical, and the pouring path leading to the cutout portion 21 is not separated by the flat foil 2, so that the plug slurry can be poured uniformly.

[0032] FIG. 4 shows a comparative example and corresponds to FIG. 3. As shown in FIG. 4, in the case of a flat foil 2 without a cutout, the interior of the hollow portion of the winding core is divided into two by the flat foil from the top to the bottom. When a plug slurry liquid was injected into the hollow portion of the winding core in this structure, it was found that a difference in the injection level of the plug slurry liquid occurred on the left and right sides of the flat foil, as shown in FIG. 5(A). This is because the spaces in the hollow portion of the winding core are separated by the flat foil. In other words, the separation of the spaces causes a difference in the amount of slurry liquid injected into each space (see FIG. 5(B)), which is thought to be the cause of the difference between the left and right sides. If the difference between the left and right sides becomes too large, the bonding strength of the shorter plug portion decreases.

[0033] According to this embodiment, the injected plug slurry liquid is blocked by the internal cutout shape portion 21a, facilitating positioning of the porous plug 30. Furthermore, since the porous plug 30 is supported by the internal cutout shape portion 21a, the load-bearing capacity in the punching direction (the direction in which the porous plug 30 is pressed against the internal cutout shape portion 21a) can be improved.

[0034] As is clear from the above process, the porous plug 30 has a structure in which many metal pieces 31 are joined with brazing material. Because many voids are formed in the porous plug 30, the thermal capacity is lower than that of conventional dense plugs, and light-off performance can be improved. Figure 6 is a schematic diagram of the porous plug 30.

[0035] The inventors of the present invention believe that the mechanism by which voids are formed is as follows: A plug slurry containing metal pieces 31 and brazing material is poured into the hollow portion 6 of the winding core, and then the liquid is removed by drying. The brazing material then melts during firing, and the molten brazing material seeps into the gaps between the metal pieces, forming voids.

[0036] The dotted lines in FIG. 6 indicate the positions of both ends of the porous plug 30, and the volume ratio of voids in the region between these dotted lines is the porosity of the porous plug 30. That is, the area surrounded by the surfaces along the upper and lower end faces of the porous plug 30 (surfaces indicated by dotted lines in FIG. 6 ) and the inner surface of the core hollow portion 6 can be defined, and the ratio of the volume occupied by voids to the volume of this area can be taken as the "porosity." The upper and lower end faces of the porous plug 30 define one end and the other end in the longitudinal direction of the core hollow portion 6 in the solid portion of the porous plug 30 excluding the voids, and the plane passing through this one end and the plane passing through this other end can be taken as the "upper and lower end faces." For example, the porous plug 30 can be used as an imaging target, multiple X-ray CT images can be taken, these CT cross-sectional images can be binarized to separate them into solid and void portions, and the area ratio of the voids can be calculated, thereby calculating the porosity of the porous plug 30. Specifically, the arithmetic mean value of the area ratio of voids in each CT cross-sectional image can be taken as the porosity of the porous plug 30.

[0037] The porosity of the porous plug 30 is preferably 7% or more. By increasing the porosity of the porous plug 30 to 7% or more, the heat capacity of the porous plug 30 is sufficiently reduced, and the light-off performance of the metal honeycomb body 4 can be improved.

[0038] The porosity of the porous plug 30 is preferably 85% or less. When the raw materials are the metal pieces 31 and the brazing filler metal, if the porosity is excessively high, solid-state bonding between the metal pieces without the brazing filler metal becomes dominant, and the strength of the porous plug 30 itself (i.e., the shape retention of the plug) cannot be maintained.

[0039] When the diameter of the winding core hollow portion 6 is defined as D, the axial length of the porous plug 30 is preferably equal to or greater than D. By setting the axial length of the porous plug 30 to be equal to or greater than D, a sufficient bonding area between the porous plug 30 and the winding core hollow portion 6 is ensured, thereby preventing the porous plug 30 from falling out of the winding core hollow portion 6. The axial length of the porous plug 30 is preferably 3D or less. By setting the axial length of the porous plug 30 to 3D or less, the effect of reducing the heat capacity by the porous plug 30 can be more effectively exerted.

[0040] The brazing material for the porous plug 30 is preferably the same as the brazing material used to join the flat foil 2 and the corrugated foil 3. For example, if a Ni-based brazing material is used to join the flat foil 2 and the corrugated foil 3, it is preferable to use the same Ni-based brazing material for the porous plug 30. This allows the heat resistance and thermal expansion of the joint between the flat foil 2 and the corrugated foil 3 to be equal to that of the joint between the metal piece 31. Examples of Ni-based brazing materials that can be used include BNi-1 to BNi-7 specified in "JIS Z 3265" and BNi-5a, BNi-8, BNi-9, BNi-10, BNi-11, BNi-12, and BNi-13 published by the American Welding Society (AWS). However, different brazing materials may be used as long as their thermal expansion coefficients are relatively similar.

[0041] It is desirable to use the same metal for the metal piece 31 as for the flat foil 2 and the corrugated foil 3. This makes it possible to equalize the heat resistance and thermal expansion of the metal piece 31, the flat foil 2, and the corrugated foil 3. However, the types of metal may be different as long as the thermal expansion coefficients are relatively close.

[0042] The shape of the metal pieces 31 is not particularly limited, and may be, for example, a disk, a sphere, a triangular pyramid, a cube, or the like. Alternatively, the porous plug 30 may be formed by mixing metal pieces 31 of different shapes. However, forming the metal pieces 31 into a disk shape increases the aspect ratio, making it more likely that voids will form. Therefore, it is preferable to use disk-shaped metal pieces 31.

[0043] Next, a method for disposing the porous plug 30 in the hollow portion 6 of the winding core will be specifically described. A plug slurry (corresponding to a slurry base material) is prepared by mixing a large number of metal pieces 31 and a fragmented or powdered brazing material in a liquid with appropriate viscosity. When the total content of the metal pieces 31 in the plug slurry is X mass % and the total content of the brazing material is Y mass %, the ratio of X mass % to Y mass % (X:Y) is within the range of 3:7 to 9:1. Expressing this blending ratio condition as a fraction, X / Y is 3:7 or more and 9:1 or less. If the ratio X / Y is too small, the plug shape cannot be maintained. In other words, if there is too much brazing material, the brazing material will flow off during firing, making it impossible to obtain a plug-shaped fired body.

[0044] If X / Y becomes excessively large, the strength of the porous plug 30 itself decreases. In other words, the brazing material becomes insufficient, and solid-state bonding between the metal pieces without the brazing material becomes dominant, reducing the brazing strength of the adjacent metal pieces 31, making it impossible to maintain the plug shape.

[0045] A preferable lower limit of X:Y is 4:6. In other words, a preferable lower limit of X / Y is 4 / 6. By setting X / Y to 4 / 6 or more, the porosity of the porous plug 30 is increased, and the light-off performance of the catalytic converter 1 is improved. In other words, the amount of brazing material that fills the voids is reduced, so the porosity of the porous plug 30 can be increased. A preferable upper limit of X:Y is 7:3. In other words, a preferable upper limit of X / Y is 7 / 3. By setting X / Y to 7 / 3 or less, the brazing strength of adjacent metal pieces 31 is improved, and the shape retention of the plug can be further improved.

[0046] A predetermined amount of the prepared plug slurry is poured from the end of the hollow core 6 toward the internal cutout 21a, and then dried. Since the poured plug slurry is blocked by the internal cutout 21a, the porous plug 30 can be easily positioned.

[0047] After the plug slurry is poured into and dried, the metal honeycomb body 4 is fired in a vacuum atmosphere at a temperature of approximately 1200°C (this corresponds to the "firing process" described below). When the metal honeycomb body 4 is fired, the molten brazing material brazes adjacent metal pieces 31 together. The molten brazing material also adheres to the inner surface of the winding core hollow portion 6, allowing the porous plug 30 to be fixed at the intended position in the winding core hollow portion 6. Furthermore, because the porous plug 30 is supported by the internal cutout shape portion 21a, the load-bearing capacity in the punching direction (the direction in which the porous plug 30 is pressed against the internal cutout shape portion 21a) can be improved.

[0048] Next, a method for manufacturing the honeycomb unit and the catalytic converter will be described. The manufacturing process of a honeycomb unit can be divided into a preparation process before firing and a firing process. The preparation process includes a process A of applying a brazing material to the joint portions of the flat foil 2 and the corrugated foil 3, a process B of applying a brazing material to the joint portions of the metal honeycomb body 4 and the outer cylinder 5, and a process C of injecting a plug slurry into the hollow portion 6 of the winding core. There are no particular limitations on the means of applying the brazing material, and the application may be, for example, by applying a powdered brazing material or by temporarily joining the brazing material with foil.

[0049] Step A may be performed when the flat foil 2 and the corrugated foil 3 are wound around a predetermined axis, or may be performed after the winding. When performed after the winding, step A can be performed, for example, by spraying a brazing material from above the metal honeycomb body 4 toward the intended joining portion.

[0050] Step B may be performed after step A. For example, step B can be performed by wrapping a strip of foil brazing material around the intended joining portion of the metal honeycomb body 4 after performing step A, inserting the metal honeycomb body 4 wrapped with the foil brazing material into the outer tube 5, and then reducing the diameter of the outer tube 5 to press it against the metal honeycomb body 4 wrapped with the foil brazing material. The diameter reduction means can be a compression means that compresses the outer tube 5 radially inward. However, step B is not limited to a diameter reduction means. For example, step B can be achieved by press-fitting the metal honeycomb body 4 wrapped with the foil brazing material into the outer tube 5.

[0051] Step B may be performed before step A. For example, after the flat foil 2 and the corrugated foil 3 are wound around a predetermined axis to produce the metal honeycomb body 4, step B may be performed by winding the foil brazing material thereon, and step A may be performed after step B is performed by spraying the brazing material thereon.

[0052] The order of step C is not particularly limited. It may be performed after step A and step B, or before step A and / or step B. However, since step C is a step of injecting a plug slurry into the hollow portion 6 of the winding core, it must be performed at least after the flat foil 2 and the corrugated foil 3 have been wound around the predetermined axis.

[0053] The firing step performed after the preparation step will not be described again. By performing the firing step after steps A to C, the porous plug 30 can be manufactured and installed, the flat foil 2 and the corrugated foil 3 can be joined, and the metal honeycomb body 4 and the outer casing 5 can be joined simultaneously.

[0054] Next, a method for manufacturing a catalytic converter will be described in detail. After the honeycomb unit is manufactured (in other words, after the firing treatment step is performed), the catalyst is supported on the metal honeycomb body 4. The catalyst can be supported by, for example, a dipping method or a suction method. The immersion method involves immersing the metal honeycomb body 4 joined to the outer casing 5, i.e., the honeycomb unit described above, in a washcoat liquid to apply a catalyst to the metal foil that constitutes the metal honeycomb body 4. The washcoat liquid may be, for example, a slurry liquid obtained by stirring gamma alumina powder, lanthanum oxide, zirconium oxide, and cerium oxide in an aqueous solution of palladium nitrate.

[0055] The suction method is a method in which a washcoat liquid containing a catalyst is sucked from the axial direction of the metal honeycomb body 4 to coat the catalyst on the metal foil that constitutes the metal honeycomb body 4.

[0056] When the washcoat liquid is applied to the metal honeycomb body 4, the washcoat liquid also flows into the hollow portion 6 of the winding core. Therefore, through holes may be formed in the porous plug 30 so that the washcoat liquid that has flowed into the hollow portion 6 of the winding core can be discharged through the through holes. This prevents excess catalyst from accumulating in the hollow portion 6 of the winding core. The through holes can be formed by drilling holes in the porous plug 30 after the heat treatment.

[0057] The washcoat liquid is applied to the metal foil of the metal honeycomb body 4, and then the applied catalyst can be supported on the metal foil by drying and firing. The firing conditions are set appropriately depending on the inner diameter of the cells, the axial length of the metal honeycomb body 4, the type of washcoat liquid, etc., and for example, the firing temperature can be set to 400 to 800°C, and the firing time can be set to 1 to 6 hours. After the catalyst has flowed in, the catalyst can be supported by drying and firing.

[0058] Furthermore, when the catalytic converter 1 does not have an outer casing 5, the catalytic converter may be formed by applying a washcoat liquid to the metal honeycomb body 4 by the above-mentioned method, followed by drying and firing.

[0059] (Variation 1) In the above embodiment, the notched portion 21 is formed in the flat foil 2, but the present invention is not limited to this, and the notched portion may be formed in the end portion of the corrugated foil 3.

[0060] (Variation 2) At least one of the flat foil 2 and the corrugated foil 3 may be a perforated metal foil having a large number of through holes formed therein. When the porous plug 30 is disposed on the gas inlet side, it is desirable that a predetermined region on the gas inlet side of the metal honeycomb body 4 (hereinafter also referred to as the gas inlet side non-opening) be a non-opening without through holes. It is desirable that the gas inlet side non-opening is at least 1 mm from the gas inlet side end. This maintains the strength of the metal foil and ensures a sufficient bonding area between the porous plug 30 and the metal foil. Because the plug of this embodiment is porous, if the entire plug is bonded to the region with the openings, the bonding area will be reduced, which may result in a decrease in the bonding strength of the porous plug. By bonding at least a portion of the porous plug to the non-opening portion of the metal foil, this problem can be eliminated. The gas inlet-side non-opening portion is preferably located 10 mm or less from the gas inlet-side end.

[0061] When the porous plug 30 is disposed on the gas outlet side, it is desirable that a predetermined region on the gas outlet side of the metal honeycomb body 4 (hereinafter also referred to as the gas outlet non-opening) be a non-opening with no through holes. The gas outlet non-opening is desirably 1 mm or more from the gas outlet end. The reason for this is the same as for the gas inlet non-opening, and therefore will not be explained here. It is desirable that the gas outlet non-opening is 10 mm or less from the gas outlet end.

[0062] (Variation 3) In the above-described embodiment, the porous plug 30 is disposed at one end of the winding core hollow portion 6, but the present invention is not limited to this, and the porous plug 30 may be disposed at both ends of the winding core hollow portion 6. In this case, since both ends of the winding core hollow portion 6 are closed by the porous plug 30, it is possible to prevent the washcoat liquid from flowing into the inside of the winding core hollow portion 6 when the honeycomb unit is immersed in the washcoat liquid. This reduces the amount of catalyst used, thereby reducing costs.

[0063] (Variation 4) In the above-described embodiments, metal pieces 31 and brazing material are used as raw materials for manufacturing the porous plug 30. However, the present invention is not limited to this, and an inorganic adhesive can be used instead of the brazing material. In this case, a porous plug 30 in which adjacent metal pieces 31 are bonded with an inorganic adhesive is prepared in advance, and this porous plug 30 is supported in the cutout portion 21 and bonded to the inner surface of the hollow portion 6 of the winding core with the inorganic adhesive. As the inorganic adhesive, for example, an inorganic adhesive containing alumina as a main component (for example, Aron Ceramic D manufactured by Toa Gosei Co., Ltd.) can be used.

[0064] (Example) Next, the present invention will be described in detail with reference to examples. A number of samples having different compounding ratios of metal pieces and brazing filler metal were prepared, and the shape retention of the plug, light-off performance, plug uniformity, and cold pressing load resistance of the plug were evaluated. A metal honeycomb body with a hollow core was manufactured by winding a corrugated foil and a flat foil in a stacked state. The metal foil (foil thickness: 50 μm) for the corrugated foil and the flat foil was a ferritic stainless steel composed of 20 mass% Cr, 5 mass% Al, and the remainder Fe and unavoidable impurities. The metal foil used was without holes. The diameter, length, cell density, and diameter of the hollow core of the metal honeycomb body were 33 mm, 60 mm, 300 cpsi, and 5 mm, respectively. BNi-5 (see JIS Z 3265) was used as the bonding material (brazing material) for the corrugated foil and the flat foil.

[0065] In Examples 1 to 5 and Comparative Examples 1 and 2, flat foils were used in which the axial length of the foil-free portion S was 10 mm. In Comparative Examples 3 to 7, flat foils without the foil-free portion S (that is, metal foils without cutout portions) were used.

[0066] The metal pieces used for the porous plugs were made of the same metal composition as the corrugated and flat foils. The brazing filler metal used for joining the corrugated and flat foils was the same composition as the brazing filler metal. The metal pieces were disk-shaped, 0.9 mm in diameter and 0.05 mm thick. A slurry containing the metal pieces and brazing filler metal was poured into the inlet end of the hollow core, then dried. A 1.5 mm thick, 60 mm long outer cylinder made of SUS436L was placed in the core, and the core was fired to form a porous plug. The amount of slurry poured was set to a design amount that would allow a 10 mm porous plug to be placed. Note that no porous plug was placed in the outlet end of the hollow core.

[0067] The blending ratio (X:Y) of the metal flakes and the brazing filler metal was 5:5 for Example 1 and Comparative Example 3, 3:7 for Example 2 and Comparative Example 4, 4:6 for Example 3 and Comparative Example 5, 7:3 for Example 4 and Comparative Example 6, 9:1 for Example 5 and Comparative Example 7, 1:9 for Comparative Example 1, and 9.5:0.5 for Comparative Example 2. For each of Examples 1 to 5 and Comparative Examples 3 to 7, three samples were prepared and the porosity was measured. For Comparative Example 1, the blending ratio of the metal flakes was too low, and none of the samples were in the form of a plug, so the porosity was not measured. The porosity was determined by taking 10 X-ray CT images of the porous plug, binarizing each X-ray CT image, and analyzing the images, as described in the embodiment. The average value of the porosities was used.

[0068] In Comparative Example 8, a dense plug (hereinafter also referred to as an N plug) was disposed instead of the porous plug. The N plug was made of the same material as the metal piece of the porous plug. The axial length of the N plug was 10 mm. In Comparative Example 9, neither a porous plug nor an N plug was disposed. In Comparative Example 10, a restricting portion was provided to restrict the inflow of exhaust gas by pushing a conical jig into the overlapping portion of the flat foil and corrugated foil extending into the hollow portion of the winding core and expanding it (i.e., the central shape processing of Patent Document 2).

[0069] (Plug shape retention) The shape retention of the plug was evaluated by pressing a rod into the porous plug 30 from the top end surface and observing the change in plug shape after unloading. The rod size was φ4 mm, the rod was pressed 20 mm over a distance of 20 mm, and the rod was pressed at a speed of 1.0 mm / sec. If the metal pieces constituting the porous plug are firmly bonded with brazing material, the porous plug will not deform and will maintain its original shape even when a load is applied. On the other hand, if the metal pieces are weakly bonded together, the shape of the porous plug will change under load. This change in shape affects the sealing area of ​​the porous plug. If the metal pieces are weakly bonded together, the porous plug will break apart during use of the metal honeycomb body. Breaking apart will result in the plug losing its original function of suppressing gas inflow into the hollow portion of the winding core (in other words, preventing gas leakage).

[0070] Therefore, in this example, those whose shape after the load test remained the same as their original shape were evaluated as having very good shape retention with a grade of AAA, those whose axial reduction was within 1 mm were evaluated as having good shape retention with a grade of AA, those whose reduction was more than 1 mm but for which the bonding between the metal pieces was ensured and the sealing points were sealed were evaluated as having somewhat good shape retention with a grade of A, and those whose shape changed significantly and for which it was determined that the sealing points were not properly sealed were evaluated as having poor shape retention with a grade of B. Since Comparative Examples 3 to 7 are samples for evaluating the plug uniformity and cold pressing load resistance of Examples 1 to 5, shape retention and light-off performance were not evaluated.

[0071] (Light-off performance) Light-off performance: SV (space velocity): 100,000h -1The simulated gas was passed through a metal honeycomb body under the above conditions, and the gas temperature was gradually increased from room temperature. The HC conversion rate (%) at each temperature was measured, and the time (τ50) at which the conversion rate reached 50% was evaluated from the conversion rate-temperature curve. τ50 was evaluated as AAA for 12 seconds or less, AA for 14 seconds or less, A for 16 seconds or less, and B for more than 16 seconds. The simulated gas used was a simulated gas (simulating diesel exhaust gas) consisting of HC (propane, CH): 550 ppm (1650 ppmC), NO: 500 ppm, CO: 0.5%, O: 1.5%, HO: 10%, and the remainder N.

[0072] (Plug uniformity) After the plug was installed, the axial length of the plug was measured, and the difference between the design value (10 mm) and the longest part and the difference between the design value (10 mm) and the shortest part were calculated, and the larger absolute value of the difference was adopted as the evaluation value. If the evaluation value was 25% or more of the design value (10 mm), the plug uniformity was deemed extremely poor and rated as B. If the evaluation value was 15% or more but less than 25% of the design value (10 mm), the plug uniformity was deemed somewhat poor and rated as A. If the evaluation value was 5% or more but less than 15% of the design value (10 mm), the plug uniformity was deemed good and rated as AA. If the evaluation value was less than 5% of the design value (10 mm), the plug uniformity was deemed extremely good and rated as AAA.

[0073] (Plug cold pressing load resistance) A push-in test was carried out under the same conditions as those for the shape retention of the plug, and the load value was measured. However, for Comparative Examples 3 to 7 (without notched portions), the rod size was set to φ2 mm, and the plug portions located on both sides of the flat foil were pressed in, and the smaller load value was taken as the measured value. The punching load of the N plug (Comparative Example 8) was used as a reference value, and the cold-press load resistance was evaluated by comparing with this reference value. If the measured load value was below the reference value, the cold-press load resistance was deemed poor and rated as B. If the measured load value was less than 25% higher than the reference value (including 0%), the cold-press load resistance was deemed generally good and rated as A. If the measured load value was 25% or more but less than 50% higher than the reference value, the cold-press load resistance was deemed good and rated as AA. If the measured load value was 50% or more higher than the reference value, the cold-press load resistance was deemed extremely good and rated as AAA. [Table 1]

[0074] Examples 1 to 5 showed improved plug shape retention compared to Comparative Example 10, which employed central shape processing as the restricting means. Comparative Example 2 received a rating of B for plug shape retention due to an insufficient amount of brazing material. It was also found that a desired bonding strength was obtained and plug shape retention was further improved by setting X:Y to 7:3 or less, in other words, X / Y to 7 / 3 or less. Examples 1 to 5 showed improved light-off performance compared to Comparative Example 8, which employed an N plug. It was found that setting X:Y to 4:6 or more, in other words, X / Y to 4 / 6 or more, increased the porosity of the porous plug 30 and further improved light-off performance.

[0075] In Comparative Examples 3 to 7, the evaluation of plug uniformity did not exceed A. Furthermore, in Comparative Examples 3 to 7, the evaluation of cold pressing load resistance was poor compared to the Examples.

[0076] (Variation) In the above-described embodiment, the metal pieces 31 and brazing material are used as the raw materials for manufacturing the porous plug 30. However, the present invention is not limited to this, and an inorganic adhesive can be used instead of the brazing material. In this case, a porous plug 30 in which adjacent metal pieces 31 are bonded with an inorganic adhesive is prepared in advance, and this porous plug 30 is then disposed at one end of the winding core hollow portion 6 and bonded to the inner surface of the winding core hollow portion 6 with the inorganic adhesive. As the inorganic adhesive, for example, an inorganic adhesive containing alumina as a main component (for example, Aron Ceramic D manufactured by Toa Gosei Co., Ltd.) can be used. [Explanation of symbols]

[0077] 1 catalytic converter 2 Flat foil 3 wave foil 4 Metal honeycomb body 5 outer cylinder 6. Hollow core 30 Porous plug 31 Metal piece

Claims

1. A metal honeycomb body having a hollow core formed by winding flat foil and corrugated foil made of metal foil, a notch-shaped portion is formed at an end of one of the flat foil and the corrugated foil, the notch-shaped portion at least partially extending toward the hollow portion of the winding core; a plug made of a porous material is placed in at least one end of the hollow portion of the winding core; The plug is supported by the cutout portion inside the hollow portion of the winding core. A metal honeycomb body characterized by:

2. the cutout shape portion includes an inner cutout shape portion located inside the winding core hollow portion and an outer cutout shape portion located outside the winding core hollow portion, the outer cutout portion is covered by the metal foil other than the end portion of the one metal foil wound around the hollow portion of the winding core, 2. The metal honeycomb body according to claim 1.

3. 3. The metal honeycomb body according to claim 1, wherein the plug has a structure in which a number of metal pieces are joined together with a brazing material.

4. 3. The metal honeycomb body according to claim 1, wherein the plug is made of a number of metal pieces and an inorganic adhesive that bonds adjacent metal pieces together.

5. 3. The metal honeycomb body according to claim 1, wherein the porosity of the plugs is 7% or more and 85% or less.

6. the metal piece is made of the same material as the metal foil, 4. The metal honeycomb body according to claim 3, wherein the brazing material is made of the same material as the brazing material used to bond the flat foil and the corrugated foil.

7. 3. The metal honeycomb body according to claim 1, wherein the axial length of the plug is from 1 to 3 times the diameter of the hollow portion of the winding core.

8. The metal honeycomb body according to claim 1, on which a catalyst is supported; an outer cylinder in which the metal honeycomb body is housed; A catalytic converter comprising:

9. The method for manufacturing a metal honeycomb body according to claim 1, a base material supply step of supplying a slurry base material containing a brazing material and a large number of metal pieces from an end of the hollow portion of the winding core toward the cutout shape portion; a firing step of firing the metal honeycomb body after the base material supply step; and A method for manufacturing a metal honeycomb body, characterized in that in the base material supply step, when the total content of the metal pieces in the slurry base material is X mass%, and the total content of the brazing material is Y mass%, the ratio of X mass% to Y mass%, X:Y, is within the range of 3:7 to 9:1.

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