Honeycomb unit and catalytic converter

Abstract

To provide a honeycomb unit which has an axial length longer than the diameter of a honeycomb body and is excellent in vibration resistance in addition to thermal fatigue resistance.SOLUTION: The honeycomb structure has a honeycomb body 10 formed by winding metallic flat and corrugated foils and an outer cylinder 20 surrounding the outer peripheral surface of the honeycomb body 10 and both of them are joined to each other by an outer cylinder-honeycomb body joining part 50 having an axial length 5mm or more. The flat foil-corrugated foil is joined over the whole laminated layers in an end joining part 11 in one end part of the honeycomb body. Further, at the outer peripheral joint portion 12 connected to the other end of the end joint portion, they are joined to each other over the length extending to the other end. Further, the outer peripheral joint part is composed of a first region having the number of layers of N from the outermost periphery of the honeycomb body and a second region of N+1 (N: any of 4 to 7), and the number of layers of the region having a high occupancy rate in the circumferential direction of the honeycomb body out of the first and second regions is any of 5 to 7 layers. Further, the lengths of A to F in the drawing satisfy the following relationship. A> B (1) C <D (2) F ≥ 0. 7E - B (3) SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a honeycomb unit and a catalytic converter. [Background technology]

[0002] A honeycomb unit consisting of a honeycomb body formed by laminating flat foil and corrugated foil and an outer cylinder that houses the honeycomb body is used as a purification device for purifying exhaust gases emitted from an internal combustion engine. Honeycomb bodies are mainly classified into laminated type honeycomb bodies and wound type honeycomb bodies. Laminated type honeycomb bodies are formed by alternately laminating flat foil made of metal foil and corrugated foil made of corrugated metal foil. Wound type honeycomb bodies are formed by spirally winding overlapping flat foil and corrugated foil. By placing a honeycomb unit (also called a catalytic converter) equipped with a honeycomb body carrying a catalyst in the exhaust gas path, the exhaust gas passing through the catalytic converter comes into contact with the catalyst over a wide area, enabling efficient exhaust gas purification.

[0003] However, because this catalytic converter is used in an environment where high-temperature exhaust gas flows, the honeycomb body expands axially and radially due to the heat from the exhaust gas, and stress is concentrated at the joint between the outer casing and the honeycomb body. If this occurs repeatedly, the joint between the outer casing and the honeycomb body will peel off, making the honeycomb body more likely to fall off. Furthermore, because heat is generated when air pollutants in the exhaust gas come into contact with and react with the catalyst, the temperature becomes higher the closer to the inlet end face of the honeycomb unit. Therefore, for example, if the outer cylinder and the honeycomb body are joined near the inlet end in the axial direction of the honeycomb unit, the repeated reaction heat between the air pollutants in the exhaust gas and the catalyst will reduce the joining strength, making the honeycomb body more likely to fall off. In this way, if the honeycomb unit does not have sufficient resistance to repeated heating and cooling due to the heat of exhaust gas and the heat of reaction in the catalyst (hereinafter also referred to as thermal fatigue resistance), the honeycomb unit may be damaged by the falling off of the honeycomb body.

[0004] Therefore, in honeycomb units, the joining position between the outer tube and the honeycomb body is generally set on the outlet side in the axial direction of the honeycomb unit. With this configuration, the joining position between the outer tube and the honeycomb body can be separated from the area of ​​the honeycomb body that is likely to become hot (near the inlet side), thereby reducing the thermal stress applied to the joining portion and the possibility of the honeycomb body falling off.

[0005] For example, Example 5 of Patent Document 1 discloses a honeycomb unit in which an outer cylinder and a honeycomb body are joined from the outlet end to the vicinity of the center in the axial direction. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 1990 / 03842 Summary of the Invention [Problem to be solved by the invention]

[0007] In addition to thermal fatigue resistance, honeycomb units are also required to be vibration resistant so that they can be used in environments where engines and exhaust pipes vibrate violently, such as in diesel engines and motorcycles. Here, the honeycomb unit used in Example 5 of Patent Document 1 has a honeycomb body whose axial length is shorter than its diameter. In such a honeycomb unit, even if the joining position between the outer tube and the honeycomb body is set on the axial outlet side, the axial distance from the joining position to the inlet end of the honeycomb body is short. Therefore, the honeycomb body vibrates little around the joining point between the outer tube and the honeycomb body, resulting in high vibration resistance.

[0008] On the other hand, in the case of a honeycomb unit in which the axial length of the honeycomb body is longer than the diameter of the honeycomb body, if the joint position between the outer tube and the honeycomb body is set on the axial outlet side, the axial distance from the joint position to the inlet end of the honeycomb body is long, so the vibration of the honeycomb body with the joint between the outer tube and the honeycomb body as the fulcrum becomes larger, and therefore the possibility of the honeycomb body falling off from the outer tube increases.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a honeycomb unit in which the axial length of the honeycomb body is longer than the diameter of the honeycomb body, and which has excellent thermal fatigue resistance as well as vibration resistance. [Means for solving the problem]

[0010] In view of the above, the present invention provides (1) a honeycomb unit comprising a honeycomb body formed by winding flat foil and corrugated foil made of metal foil, and an outer cylinder arranged in a position surrounding the outer peripheral surface of the honeycomb body, wherein the axial length of the honeycomb body is longer than the outer diameter of the honeycomb body, the honeycomb body and the outer cylinder are joined to each other by an outer cylinder-honeycomb body joint, the flat foil and the corrugated foil are joined to each other at an end joint at one end of the honeycomb body, and are joined to each other at a peripheral joint that connects to the other end of the end joint, the end joint being formed over all layers in the stacking direction of the flat foil and the corrugated foil, and the peripheral joint being formed from the other end of the end joint to the other end of the honeycomb body, and when a set of the corrugated foil and the flat foil sandwiching it in the stacking direction is defined as one layer, the peripheral joint is a first region having N layers from the outermost periphery of the honeycomb body, and a second region having N+1 layers from the outermost periphery of the honeycomb body (where N is any number from 4 to 7); the number of layers in the region having a high circumferential occupancy of the honeycomb body in the first region and the second region is any number from 5 to 7; the axial length of the outer tube-honeycomb body joint is 5 mm or more; and the honeycomb unit satisfies the following formulas (1), (2), and (3), where A is the outer diameter of the honeycomb body, B is the axial length from one end of the honeycomb body to one end of the outer tube-honeycomb body joint, C is the axial length from the other end of the end joint to one end of the outer tube-honeycomb body joint, D is the axial length of the honeycomb body, E is the axial length of the honeycomb body, and F is the axial length from the other end of the outer tube-honeycomb body joint to the other end of the honeycomb body. A>B···(1) C <D···(2) F≧0.7EB (3)

[0011] (2) In a racetrack-type honeycomb unit having a honeycomb body formed by winding flat foil and corrugated foil made of metal foil, and an outer cylinder arranged in a position surrounding the outer peripheral surface of the honeycomb body, the axial length of the honeycomb body is longer than the minor axis of the honeycomb body when viewed in the axial direction, the honeycomb body and the outer cylinder are joined to each other by an outer cylinder-honeycomb body joint, the flat foil and the corrugated foil are joined to each other at an end joint at one end of the honeycomb body, and are joined to each other at a peripheral joint connected to the other end of the end joint, the end joint is formed over all layers in the stacking direction of the flat foil and the corrugated foil, and the peripheral joint is formed from the other end of the end joint to the other end of the honeycomb body, and when a set of the corrugated foil and the flat foil sandwiching it in the stacking direction is defined as one layer, the peripheral joint is formed over all layers of the honeycomb The honeycomb body is made up of a first region having N layers from the outermost periphery thereof, and a second region having N+1 layers from the outermost periphery thereof (where N is any of 4 to 7), and the number of layers in the region having a high occupancy rate in the circumferential direction of the honeycomb body in the first region and the second region is any of 5 to 7 layers, the axial length of the outer tube-honeycomb body joint is 5 mm or more, and the minor axis of the honeycomb body as viewed in the axial direction is A A honeycomb unit that satisfies the following formulas (1'), (2'), and (3'), where B' is the axial length from one end of the honeycomb body to one end of the outer tube-honeycomb body joint, C' is the axial length of the end joint, D' is the axial length from the other end of the end joint to one end of the outer tube-honeycomb body joint, E' is the axial length of the honeycomb body, and F' is the axial length from the other end of the outer tube-honeycomb body joint to the other end of the honeycomb body. A´>B´···(1´) C´ <D´···(2´) F´≧0.7E´-B´···(3´)

[0012] (3) The honeycomb unit according to (1), further satisfying the following formula (4): E≧1.4A (4)

[0013] (4) The honeycomb unit according to (2), further satisfying the following formula (4'): E´≧1.4A´···(4´)

[0014] (5) A honeycomb unit according to any one of (1) to (4), characterized in that the number of layers in the first region and the second region, which have a high circumferential occupancy rate of the honeycomb body, is six.

[0015] (6) A catalytic converter, characterized in that a catalyst is supported on the honeycomb body according to any one of (1) to (4).

[0016] (7) A catalytic converter characterized in that a catalyst is carried on the honeycomb body according to (5). [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a honeycomb unit in which the axial length of the honeycomb body is longer than the diameter of the honeycomb body, and which has excellent thermal fatigue resistance as well as vibration resistance. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a perspective view of a honeycomb unit 1 according to a first embodiment. [Figure 2] 2 is a cross-sectional view of the honeycomb unit shown in FIG. 1 taken along line XX. [Figure 3] FIG. 2 is a cross-sectional view of the honeycomb unit 1 shown in FIG. 1, cut in a direction perpendicular to the axial direction in a region where the peripheral bonding layer 12 exists. [Figure 4] FIG. 2 is a vertical cross-sectional view of the honeycomb unit shown in FIG. [Figure 5] FIG. 10 is a plan view of a honeycomb unit 1′ according to a second embodiment. [Figure 6] FIG. 6 is a YY cross-sectional view of the honeycomb unit 1′ shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0019] (First embodiment) A first embodiment of a honeycomb unit of the present invention will be described below with reference to the drawings. Fig. 1 is a perspective view of a honeycomb unit 1 in the first embodiment. Referring to the figure, the honeycomb unit 1 includes a honeycomb body 10 and an outer cylinder 20 formed in a cylindrical shape and disposed in a position surrounding the outer surface of the honeycomb body 10 in the radial direction. In the honeycomb unit 1 of this embodiment, the axial length of the honeycomb body 10 is longer than the outer diameter of the honeycomb body 10, and is preferably 1.4 times or more the outer diameter of the honeycomb body 10.

[0020] The honeycomb body 10 is constructed by winding the corrugated foil 30 and the flat foil 40 in an overlapping state around the axial direction and bonding the corrugated foil 30 and the flat foil 40 together with a brazing material. Therefore, the honeycomb body 10 has a configuration in which the corrugated foil 30 and the flat foil 40 are alternately stacked in the radial direction. That is, the radial direction of the honeycomb body 10 coincides with the stacking direction of the corrugated foil 30 and the flat foil 40. This configuration allows for the formation of numerous gas flow channels (cells) extending in the axial direction within the honeycomb body 10. The "axial direction" coincides with the flow direction of the exhaust gas entering the honeycomb body 10. The honeycomb body 10 is inserted into an outer cylinder 20, and the outermost peripheral surface of the honeycomb body 10 is bonded to the inner peripheral surface of the outer cylinder 20 with a brazing material, thereby constructing the honeycomb unit 1. The bonding between the corrugated foil 30 and the flat foil 40 and the bonding between the honeycomb body 10 and the outer cylinder 20 will be described later. The cell density of the honeycomb body 10 is preferably set to 100 to 600 cells per square inch, more preferably 300 to 400 cells per square inch.

[0021] Heat-resistant alloys can be used for the corrugated foils 30 and flat foils 40 that make up the honeycomb body 10. Examples of heat-resistant alloys include alloys containing 15% to 25% by mass of Cr and 2% to 8% by mass of Al, such as Fe-20Cr-5Al alloys. The thickness of the corrugated foils 30 and flat foils 40 is preferably 20 μm to 100 μm, more preferably 30 μm to 50 μm. Ferritic stainless steel containing 13% to 20% by mass of Cr, such as SUS436L, SUS430, or EN Standard 1.4509, can be used for the outer cylinder 20. However, austenitic stainless steels, such as SUS315J1, can also be used. The thickness of the outer cylinder 20 is preferably 0.5 mm to 3 mm, more preferably 1 mm to 2 mm.

[0022] (Regarding bonding of honeycomb unit 1) Fig. 2 is a cross-sectional view taken along line XX of the honeycomb unit shown in Fig. 1. Referring to Fig. 2, the honeycomb body 10 is formed with an inlet-side joint 11 extending axially from the inlet-side end of the honeycomb body 10, a peripheral joint 12 extending from the outlet-side end of the inlet-side joint 11 to the outlet-side end of the honeycomb body 10, and an outlet-side joint 13. The honeycomb body 10 and the outer cylinder 20 are joined by an outer cylinder-honeycomb body joint 50.

[0023] The entry-side joint 11, the outer peripheral joint 12, the exit-side joint 13 and the outer cylinder-honeycomb body joint 50 are formed by brazing (indicated by thick lines in the drawing) using a highly heat-resistant Ni-based brazing material (for example, BNi-5). That is, the corrugated foil 30 and the flat foil 40 are wound around the axial direction in a stacked state to form a wound body, and then a brazing material is disposed on the outer peripheral surface of the wound body or on the inner peripheral surface of the outer tube 20 at the intended joining position of the honeycomb body 10 and the outer tube 20. After inserting this wound body into the outer tube 20, the brazing material is disposed at the intended joining position of the corrugated foil 30 and the flat foil 40, and heated in a vacuum atmosphere, thereby joining the corrugated foil 30 and the flat foil 40 (i.e., forming the entry-side joining portion 11, the outer peripheral joining portion 12, and the exit-side joining portion 13) and joining the honeycomb body 10 and the outer tube 20 (i.e., forming the outer tube-honeycomb body joining portion 50), thereby producing the honeycomb unit 1. Note that the timing for disposing the brazing material that joins the honeycomb body 10 and the outer tube 20 and the brazing material that joins the corrugated foil 30 and the flat foil 40 is not limited to this.

[0024] The inlet-side joint 11 joins the corrugated foil 30 and the flat foil 40 over the entire radial direction of the honeycomb body 10. By providing the inlet-side joint 11, sufficient joint strength can be ensured in the inlet region, which is prone to high temperatures when exhaust gas passes through and is exposed to exhaust gas pulsation, thereby improving the thermal fatigue resistance of the honeycomb unit 1.

[0025] The peripheral bonding portion 12 bonds a predetermined number of layers of corrugated foils 30 and flat foils 40 from the outermost periphery of the honeycomb body 10 toward the inside in the radial direction. Here, the number of layers bonded by the peripheral bonding portion 12 will be explained in more detail. Figure 3 is a cross-sectional view of the honeycomb unit 1 shown in Figure 1, cut in a direction perpendicular to the axial direction in the region where the peripheral bonding layer 12 exists. In Figure 3, the parts indicated by black dots correspond to the bonding locations, and the region where the black dots exist corresponds to the peripheral bonding portion 12.

[0026] 3, when a set of a corrugated foil 30 and a flat foil 40 sandwiching it is defined as one layer in the radial direction of the honeycomb body 10, the peripheral joint portion 12 is composed of a first region 121 having N layers from the outermost periphery of the honeycomb body 10, and a second region 122 having N+1 layers from the outermost periphery of the honeycomb body 10 (where N is any value from 4 to 7). Of the first region 121 and the second region 122, the number of layers in the region with a high occupancy rate in the circumferential direction of the honeycomb body 10 (hereinafter also referred to as the representative number of layers of the peripheral joint portion 12) is any value from 5 to 7. The reason for this will be explained later.

[0027] As an example, in this embodiment, N is set to 5. That is, the first region 121 in the peripheral bonding portion 12 has five layers from the outermost periphery of the honeycomb body 10, and the second region 122 in the peripheral bonding portion 12 has six layers from the outermost periphery of the honeycomb body 10. Then, of the occupation ratio L1 of the first region 121 to the outermost periphery bonding portion 12 and the occupation ratio L2 of the second region 122 to the outermost periphery bonding portion 12 in the circumferential direction of the honeycomb body 10, the number of layers in the higher region (the second region 122 in this embodiment) is six, which is the representative layer number.

[0028] (Overall configuration of honeycomb unit 1) The overall configuration of the honeycomb unit 1 will be described with reference to Fig. 4. Fig. 4 is a vertical cross-sectional view of the honeycomb unit shown in Fig. 1. For ease of explanation, only the entry-side bonding portion 11, the outer peripheral bonding portion 12, and the exit-side bonding portion 13 of the honeycomb body 10 in Fig. 4 are shown, and the corrugated foil 30 and the flat foil 40 are not shown.

[0029] The present inventors have conducted extensive research to manufacture a honeycomb unit having an axial length of the honeycomb body longer than the diameter of the honeycomb body, which is excellent in both thermal fatigue resistance and vibration resistance. (i) The representative number of layers in the peripheral joint 12 is any one of 5 to 7 layers; (ii) The axial length of the outer tube-honeycomb body joint 50 is 5 mm or more; (iii) The outer diameter of the honeycomb body 10 is A, the axial length from the inlet end 14 of the honeycomb body 10 (corresponding to "one end of the honeycomb body" in claim 1) to the inlet end 51 of the outer tube-honeycomb body joint 50 (corresponding to "one end of the outer tube-honeycomb body joint" in claim 1) is B, the axial length of the inlet joint 11 (corresponding to "end joint" in claim 1) is C, the outlet end 111 of the inlet joint 11 (corresponding to "end joint" in claim 1) is D, When the axial length from the outer cylinder-honeycomb body joint portion 50 (corresponding to the "other end of the outer cylinder-honeycomb body joint portion" in claim 1) to the inlet end 51 of the outer cylinder-honeycomb body joint portion 50 is defined as D, the axial length of the honeycomb body 10 is defined as E, and the axial length from the outlet end 52 of the outer cylinder-honeycomb body joint portion 50 (corresponding to the "other end of the outer cylinder-honeycomb body joint portion" in claim 1) to the outlet end 15 of the honeycomb body 10 (corresponding to the "other end of the honeycomb body" in claim 1) is defined as F, all of the following formulas (1) to (3) must be satisfied: A>B···(1) C <D···(2) F≧0.7EB (3) It has been discovered that by satisfying all of the above requirements (i) to (iii), it is possible to achieve both thermal fatigue resistance and vibration resistance. Each requirement is explained below.

[0030] (Regarding the representative number of layers of the peripheral joint 12) The present inventors have focused on the number of representative layers of the outer peripheral joint portion 12 and conducted extensive research in order to manufacture a honeycomb unit that is excellent in vibration resistance as well as thermal fatigue resistance. If the representative number of layers in the outer peripheral joint 12 is four or less, the number of joint layers is too small, and cracks that occur in the honeycomb body 10 due to vibrations of the engine or exhaust pipe in which the honeycomb unit 1 is installed are likely to penetrate radially through the outer peripheral joint 12, increasing the risk that the honeycomb body 10 will be separated from the outer tube 20 and fall off. Furthermore, if the number of representative layers in the peripheral joint 12 is eight or more, the number of joint layers becomes excessive, making it difficult to release the thermal stress that occurs in the honeycomb body 10 when the honeycomb body 10 thermally expands, increasing the risk that the corrugated foil near the joint point of the peripheral joint 12 will break and the honeycomb body 10 will fall off from the outer tube 20. In view of these points, the inventors discovered that in order to achieve both thermal fatigue resistance and vibration resistance of the honeycomb unit 1, the representative number of layers in the outer peripheral joint 12 needs to be between 5 and 7 layers.

[0031] (Axial length of outer cylinder-honeycomb body joint 50) The axial length of the outer tube-honeycomb body joint 50 is 5 mm or more. If the axial length of the outer tube-honeycomb body joint 50 is less than 5 mm, cracks that occur in the honeycomb body 10 due to vibrations of the engine or exhaust pipe in which the honeycomb unit 1 is installed are likely to penetrate the corrugated foil near the outer peripheral joint 12 in the axial direction due to thermal stress, increasing the risk of the honeycomb body 10 being severed from the outer tube 20 and falling off. Furthermore, while the thermal stress increases as the axial length of the outer tube-honeycomb body joint 50 increases, the axial temperature gradient decreases as the axial length of the honeycomb body 10 increases. Therefore, the upper limit of the axial length of the outer tube-honeycomb body joint 50 depends on the axial length of the honeycomb body 10. For example, the axial length of the outer tube-honeycomb body joint 50 is limited to 30% or less of the axial length of the honeycomb body 10.

[0032] (A>B, F≧0.7EB) In the honeycomb unit used in Example 5 of Patent Document 1, the axial length of the honeycomb body is shorter than the diameter of the honeycomb body. In such a honeycomb unit, even if the outer tube-honeycomb body joint is provided on the axial outlet side, the vibration of the honeycomb body around the outer tube-honeycomb body joint is small, and therefore the vibration resistance is high. On the other hand, in the case of a honeycomb unit (honeycomb unit 1 in this embodiment) in which the axial length of the honeycomb body is longer than the diameter of the honeycomb body, if the outer tube-honeycomb body joint 50 is provided at the outlet end 15 of the honeycomb body 10, the vibration of the honeycomb body 10 around the outer tube-honeycomb body joint 50 as a fulcrum increases. In this case, even a honeycomb unit that satisfies the above conditions (i) and (ii) cannot sufficiently reduce the possibility of the honeycomb body 10 falling off from the outer tube 20. Therefore, by setting F≧0.7EB and moving the outer casing-honeycomb body joint 50 away from the outlet end 15 of the honeycomb body 10 toward the inlet end, the axial distance from the outer casing-honeycomb body joint 50 to the inlet end 14 of the honeycomb body 10 is narrowed, and vibration of the honeycomb body 10 with the outer casing-honeycomb body joint 50 as a fulcrum can be reduced. However, even when F≧0.7EB is satisfied, if A≦B, the axial distance from the inlet end 14 of the honeycomb body 10 to the outer casing-honeycomb body joint 50 is not sufficiently short, and therefore sufficient vibration resistance may not be obtained. Therefore, by setting A>B and further narrowing the distance between the inlet end 14 of the honeycomb body 10 and the outer casing-honeycomb body joint 50, the vibration of the honeycomb body 10 can be further reduced and vibration resistance can be sufficiently improved.

[0033] (C <Dについて) As described above, if only the vibration resistance is considered and the separation distance between the inlet end portion 14 of the honeycomb body 10 and the outer cylinder-honeycomb body joint portion 50 is reduced, the inlet joint portion 11 and the outer cylinder-honeycomb body joint portion 50 may overlap, or the inlet joint portion 11 and the outer cylinder-honeycomb body joint portion 50 may be close to each other in the axial direction. However, in these configurations, due to the expansion and contraction of the inlet joint portion 11 accompanying the repeated heating and cooling by the heat of the exhaust gas and the reaction heat in the catalyst, thermal stress concentrates on the outer cylinder-honeycomb body joint portion 50, and the honeycomb body 10 is likely to fall off. Therefore, by setting C < D and separating the inlet joint portion 11 and the outer cylinder-honeycomb body joint portion 50 by a predetermined degree in the axial direction, it is possible to suppress the concentration of thermal stress on the outer cylinder-honeycomb body joint portion 50, enhance the heat fatigue resistance, and reduce the possibility of the honeycomb body 10 falling off.

[0034] As described above, the honeycomb unit 1 that satisfies all of the above requirements (i) to (iii) can achieve both heat fatigue resistance and vibration resistance.

[0035] Referring to FIG. 3, the representative number of layers of the outer peripheral joint portion 12 is preferably 6 layers as in the present embodiment. Thereby, the balance between the heat fatigue resistance and the vibration resistance of the honeycomb unit 1 becomes better.

[0036] Referring to FIG. 4, the axial length C of the inlet joint portion 11 is preferably 5 mm or more and (1 / 3)E or less. By setting C to 5 mm or more, breakage of the corrugated foil 30 and the flat foil 40 due to the pulsating flow of the exhaust gas is more suppressed. By setting C to (1 / 3)E or less, the axial length of the inlet joint portion 11 can be appropriately shortened, and the thermal stress generated in the honeycomb body 10 can be more easily released, so that the possibility of the joint portion of the outer peripheral joint portion 12 breaking and the honeycomb body 10 being damaged can be further reduced.

[0037] 2 and 4, the outlet joint 13 is formed in the outlet region of the honeycomb body 10. The outlet joint 13 joins the corrugated foil 30 and the flat foil 40, which are located radially inward of the outer peripheral joint 12, across the entire radial direction of the honeycomb body 10. By providing the outlet joint 13, not only the inlet region but also the outlet region of the honeycomb body 10 are joined, thereby further suppressing damage to the corrugated foil 30 and the flat foil 40 due to exhaust gas pulsation. Note that because exhaust gas pulsation at the outlet end 15 of the honeycomb body 10 is less severe than at the inlet end 14, the inlet joint 11 must include the inlet end 14 of the honeycomb body 10, but the outlet joint 13 does not necessarily include the outlet end 15. However, the outlet end of the outlet joint 13 is preferably located in a region up to 15 mm axially from the outlet end 15 of the honeycomb body 10. Moreover, it is desirable that the axial length of the outlet-side joint portion 13 be set to half or less of the axial length of the inlet-side joint portion 12 .

[0038] To use the honeycomb unit 1 manufactured in this manner as a catalytic converter, a catalyst (not shown) is supported on the corrugated foil 30 and the flat foil 40. The catalyst can be supported by supplying a washcoat liquid (a solution containing gamma alumina, additives, and a precious metal catalyst) to the gas flow passage of the honeycomb body 10 and baking it onto the foil surface by heat treatment.

[0039] A honeycomb unit carrying a catalyst (i.e., a catalytic converter) can be installed in the exhaust gas path of a vehicle. Vehicles include motorcycles, automobiles, and off-road vehicles. When exhaust gas that flows into the gas flow path of the honeycomb body comes into contact with the catalyst, CO, hydrocarbons, and NO contained in the exhaust gas are converted into CO, hydrocarbons, and NO. X is rendered harmless, and clean gas can be discharged outside the vehicle.

[0040] (Second embodiment) The second embodiment differs from the first embodiment in that the shapes of the honeycomb body and the outer cylinder are racetrack shaped (hereinafter also referred to as RT shape) when viewed in the axial direction. Fig. 5 is a plan view of a honeycomb unit 1' in the second embodiment. Note that components that share functions with the first embodiment are given the same names and symbols as in the first embodiment, and explanations thereof will be omitted as appropriate.

[0041] Referring to Figure 5, as described above, the honeycomb body 10' and outer cylinder 20' included in the honeycomb unit 1' in the second embodiment have a racetrack shape when viewed in the axial direction. Here, the "racetrack shape" refers to a shape that imitates a racetrack on a sports field, and is formed by drawing two parallel lines of equal length, connecting one end of each line with an arc, and connecting the other end of each line with an arc. In the honeycomb unit 1' of this embodiment, the axial length of the honeycomb body 10' is longer than the minor axis A' of the honeycomb body 10', and is preferably 1.4 times or more the minor axis A' of the honeycomb body 10'.

[0042] (Overall structure of honeycomb unit 1') The overall configuration of the honeycomb unit 1' will be described with reference to Fig. 6. Fig. 6 is a YY cross-sectional view of the honeycomb unit 1' shown in Fig. 5. For ease of explanation, Fig. 6 shows only an entry-side bonding portion 11', a peripheral bonding portion 12', and an exit-side bonding portion 13' of the honeycomb body 10', and the corrugated foil 30 and the flat foil 40 are not shown.

[0043] The present inventors have conducted extensive research to manufacture a honeycomb unit having an axial length of the honeycomb body longer than the diameter of the honeycomb body, which is excellent in both thermal fatigue resistance and vibration resistance. (i') The representative number of layers in the peripheral joint 12' is any one of 5 to 7 layers, (ii') The axial length of the outer tube-honeycomb body joint 50' is 5 mm or more; (iii') In addition to the above A', the axial length from the inlet end 14' of the honeycomb body 10' (corresponding to "one end of the honeycomb body" in claim 1) to the inlet end 51' of the outer tube-honeycomb body joint 50' (corresponding to "one end of the outer tube-honeycomb body joint" in claim 1) is B', the axial length of the inlet joint 11' (corresponding to "end joint" in claim 1) is C', the axial length of the outlet end 111' of the inlet joint 11' (corresponding to "end joint" in claim 1) is C', the axial length from the outer cylinder-honeycomb body joint portion 50' (corresponding to "the other end of the outer cylinder-honeycomb body joint portion" in claim 1) to the inlet end 51' of the outer cylinder-honeycomb body joint portion 50' is D', the axial length of the honeycomb body 10' is E', and the axial length from the outlet end 52' of the outer cylinder-honeycomb body joint portion 50' (corresponding to "the other end of the outer cylinder-honeycomb body joint portion" in claim 1) to the outlet end 15' of the honeycomb body 10' (corresponding to "the other end of the honeycomb body" in claim 1) is F', the following formulas (1') to (3') are satisfied: A´>B´···(1´) C´ <D´···(2´) F´≧0.7E´-B´···(3´) It has been discovered that by satisfying all of the above requirements (i') to (iii'), it is possible to achieve both thermal fatigue resistance and vibration resistance.

[0044] The reasons for the above (i') to (iii') have already been explained in the corresponding (i) to (iii) in the first embodiment, and therefore will not be explained in this embodiment.

[0045] (Example) Each of the above-described embodiments will be described in more detail by showing examples. In the following examples and comparative examples, SUS436L was used for the outer cylinder. BNi-5 (JIS Z 3265) powder brazing material was used to join the corrugated foil and flat foil. BNi-5a (AWS standard) foil brazing material with a thickness of 25 μm was used to join the honeycomb body and outer cylinder. The width of the foil brazing material was the value shown in each table.

[0046] (First Example) The first examples (Examples 1 to 42, Comparative Examples 1 to 109) correspond to the first embodiment described above. Two flat foils made of Fe-20Cr-5Al ferritic stainless steel were prepared. One flat foil was corrugated and the other flat foil was used as is. The corrugated and flat foils were overlapped and wound axially to form a wound body. Then, a brazing foil was applied to the outer surface of the wound body or the inner surface of the outer cylinder at a position corresponding to the planned joining location of the honeycomb body and the outer cylinder. The wound body was then inserted into the outer cylinder. Brazing foil powder was applied to the planned joining locations of the corrugated and flat foils. The wound body was then heat-treated at 1200°C in a vacuum atmosphere. This bonded the corrugated and flat foils (i.e., formed the entry-side joining portion 11 and the outer peripheral joining portion 12 in the first embodiment) to produce a honeycomb body. Furthermore, the honeycomb body was bonded to the outer cylinder (i.e., formed the outer cylinder-honeycomb body joining portion 50 in the first embodiment) to produce a honeycomb unit.

[0047] The honeycomb body of the manufactured honeycomb unit was then passed through a washcoat solution containing ceria-zirconia-lanthana-alumina as its main components and 1.25 g of palladium per 100 g, and after removing excess washcoat solution, it was dried at 180°C for 1 hour and then fired at 500°C for 2 hours to manufacture a honeycomb unit (catalytic converter) carrying a catalyst. The washcoat layer was carried on the corrugated foil and flat foil of this catalytic converter in an amount of 200 g / L of dried weight per volume of the honeycomb body.

[0048] (Evaluation method) The thermal fatigue resistance and vibration resistance of the catalytic converter were evaluated using a heating / cooling cycle test using a burner test device (not shown). More specifically, the catalytic converter was set in the burner test device, and the number of heating / cooling cycles was measured until the honeycomb body fell off the outer casing (e.g., core displacement). The burner gas piping and the outer casing were welded via a cone (not shown). The heating / cooling cycle pattern repeatedly varied the inlet gas temperature of the catalytic converter between 1000°C and 100°C. Specifically, one cycle consisted of raising the inlet gas temperature to 1000°C in 10 seconds, holding it for 1 minute, and then cooling it to 100°C in 30 seconds. During the test, the catalytic converter was tilted at a 45° angle and continuously subjected to random vibration with an effective acceleration of 60G with a constant acceleration spectral density in the range of 100Hz to 1000Hz. Observation continued up to 2000 cycles, and if the honeycomb body did not fall off up to 2000 cycles, it was rated as "◎", if the honeycomb body fell off between 1000 and 2000 cycles, it was rated as "◯", and if the honeycomb body fell off less than 1000 cycles, it was rated as "×".

[0049] (Second Example) The second examples (Examples 43 to 84, Comparative Examples 110 to 218) correspond to the second embodiment described above. The test conditions and evaluation methods were the same as those of the first example, except that the honeycomb unit constituting the catalytic converter had an RT shape when viewed in the axial direction.

[0050] (Evaluation results) The parameters and evaluation results of the honeycomb units in each of the examples and comparative examples are shown in the table. [Table 1] [Table 2] [Table 3] [Table 4] [Table 5] [Table 6] [Table 7] [Table 8] [Table 9] [Table 10] [Table 11] [Table 12]

[0051] In the first embodiment, all catalytic converters that used honeycomb units in which (i) the number of representative layers at the outer peripheral joint was between 5 and 7, (ii) the axial length of the outer tube-honeycomb body joint was 5 mm or more, and (iii) all satisfied the following formulas (1) to (3) were evaluated as "○" or better (Examples 1 to 42 of the first embodiment). A>B···(1) C <D···(2) F≧0.7EB (3) In particular, among the above examples, examples in which the representative number of layers in the peripheral joint portion was six (Examples 2, 4 to 8, 10, 12 to 17, 19, 21 to 26, 28, 30 to 34, 36, and 38 to 42 of the first example) were evaluated as "Excellent."

[0052] On the other hand, in the examples (Comparative Examples 1 to 109 of the first example) that did not satisfy at least one of the requirements (i) to (iii) above, the honeycomb body fell off from the outer tube in less than 1000 cycles, and was therefore rated as "X".

[0053] In the second example, all catalytic converters that used honeycomb units in which (i') the number of representative layers at the outer peripheral joint was between 5 and 7, (ii') the axial length of the outer tube-honeycomb body joint was 5 mm or more, and (iii') all satisfied the following formulas (1') to (3') were evaluated as "○" or better (Examples 43 to 84 of the second example). A´>B´···(1´) C´ <D´···(2´) F´≧0.7E´-B´···(3´) In particular, among the above examples, examples in which the representative number of layers in the peripheral joint portion was six (Examples 44, 46 to 50, 52, 54 to 59, 61, 63 to 68, 70, 72 to 76, 78, and 80 to 84 of the second example) were evaluated as "Excellent."

[0054] On the other hand, in examples (comparison examples 110 to 218 of the second example) that did not satisfy at least one of the requirements (i') to (iii') above, the honeycomb body fell off from the outer tube in less than 1000 cycles, and was therefore rated as "X".

[0055] (Variation) In the first embodiment described above, the honeycomb body 10 is formed with the outlet-side joints 13, but the honeycomb body 10 may also be configured without the outlet-side joints 13. Similarly, in the second embodiment described above, the honeycomb body 10' is formed with the outlet-side joints 13', but the honeycomb body 10' may also be configured without the outlet-side joints 13'. [Explanation of symbols]

[0056] 1, 1': Honeycomb unit 10, 10': Honeycomb body 11, 11': Inlet joint 12, 12': Peripheral joint 20, 20': Outer cylinder 30: Corrugated foil 40: Flat foil 50, 50': Outer cylinder-honeycomb body joint 121: First region 122: Second region

Claims

1. A honeycomb unit comprising: a honeycomb body formed by winding flat and corrugated metal foils; and an outer cylinder arranged in a position surrounding the outer peripheral surface of the honeycomb body, wherein the axial length of the honeycomb body is longer than the outer diameter of the honeycomb body, the honeycomb body and the outer cylinder are joined to each other by an outer cylinder-honeycomb body joint, The flat foil and the corrugated foil are joined to each other at an end joint at one end of the honeycomb body, and are joined to each other at an outer periphery joint connected to the other end of the end joint, The end joint portion is formed over all layers of the flat foil and the corrugated foil in the stacking direction, the outer peripheral joint portion is formed from the other end of the end joint portion to the other end of the honeycomb body, When a set of the corrugated foil and the flat foil sandwiching it in the lamination direction is defined as one layer, The peripheral joint portion comprises a first region having N layers from the outermost periphery of the honeycomb body, and a second region having N+1 layers from the outermost periphery of the honeycomb body (where N is any one of 4 to 7), the number of layers in the first region and the second region, which are regions with a high occupancy rate in the circumferential direction of the honeycomb body, is any one of 5 layers to 7 layers, The axial length of the outer cylinder-honeycomb body joint is 5 mm or more, A honeycomb unit that satisfies the following formulas (1), (2), and (3), where A is the outer diameter of the honeycomb body, B is the axial length from one end of the honeycomb body to one end of the outer tube-honeycomb body joint, C is the axial length of the end joint, D is the axial length from the other end of the end joint to one end of the outer tube-honeycomb body joint, E is the axial length of the honeycomb body, and F is the axial length from the other end of the outer tube-honeycomb body joint to the other end of the honeycomb body. A>B...(1) C < D... (2) F≧0.7E-B...(3)

2. A racetrack-type honeycomb unit includes a honeycomb body formed by winding flat and corrugated metal foils, and an outer cylinder arranged in a position surrounding the outer peripheral surface of the honeycomb body, wherein the axial length of the honeycomb body is longer than the minor axis of the honeycomb body when viewed in the axial direction, the honeycomb body and the outer cylinder are joined to each other by an outer cylinder-honeycomb body joint, The flat foil and the corrugated foil are joined to each other at an end joint at one end of the honeycomb body, and are joined to each other at an outer periphery joint connected to the other end of the end joint, The end joint portion is formed over all layers of the flat foil and the corrugated foil in the stacking direction, the outer peripheral joint portion is formed from the other end of the end joint portion to the other end of the honeycomb body, When a set of the corrugated foil and the flat foil sandwiching it in the lamination direction is defined as one layer, The peripheral joint portion comprises a first region having N layers from the outermost periphery of the honeycomb body, and a second region having N+1 layers from the outermost periphery of the honeycomb body (where N is any one of 4 to 7), the number of layers in the first region and the second region, which are regions with a high occupancy rate in the circumferential direction of the honeycomb body, is any one of 5 layers to 7 layers, The axial length of the outer cylinder-honeycomb body joint is 5 mm or more, A honeycomb unit that satisfies the following formulas (1'), (2'), and (3'), where A' is the minor axis of the honeycomb body when viewed in the axial direction, B' is the axial length from one end of the honeycomb body to one end of the outer tube-honeycomb body joint, C' is the axial length of the end joint, D' is the axial length from the other end of the end joint to one end of the outer tube-honeycomb body joint, E' is the axial length of the honeycomb body, and F' is the axial length from the other end of the outer tube-honeycomb body joint to the other end of the honeycomb body. A'>B'...(1') C'<D'...(2') F'≧0.7E'−B' (3')

3. Further satisfying the following formula (4): The honeycomb unit according to claim 1 , E≧1.4A...(4)

4. Further satisfying the following formula (4'): The honeycomb unit according to claim 2 . E'≧1.4A' (4')

5. The number of layers in the first region and the second region, which are regions with a high occupancy rate in the circumferential direction of the honeycomb body, is six.

5. The honeycomb unit according to claim 1, wherein the honeycomb unit is a honeycomb unit having a thickness of 100 nm or less.

6. The honeycomb body according to any one of claims 1 to 4, wherein a catalyst is supported on the honeycomb body. A catalytic converter comprising:

7. The honeycomb body according to claim 5, wherein a catalyst is supported on the honeycomb body. A catalytic converter comprising:

Images