Catalyst device

Abstract

To provide a catalyst device that can enhance the durability of a honeycomb core while maintaining the purification performance of exhaust gas.SOLUTION: A catalyst device (30) in which exhaust gas (G) is purified by passing through a honeycomb core (31) formed by winding a metal foil (40) carrying a catalyst is provided. A plurality of through holes (H) are formed in a part of the metal foil (40). In an axial direction of the exhaust gas (G) flow in the honeycomb core (31), a boundary region (C) is provided between a dense region (A) in which the through holes (H) are densely formed and a non-formed region (B) in which no through holes (H) are formed. The boundary region (C) is configured such that the total area of the through holes (H) gradually decreases from the dense region (A) side toward the region (B) side. The boundary region (C) is provided only on a downstream side of the exhaust gas (G) with respect to the dense region (A).SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a catalytic converter, and more particularly to a catalytic converter having a honeycomb core formed by laminating metal foils carrying a catalyst. [Background technology]

[0002] Efforts to mitigate or reduce the impact of climate change have been ongoing for some time, and research and development into emissions improvement has been conducted to achieve this. It is known that catalytic converters for purifying exhaust gas from internal combustion engines use honeycomb cores made of laminated metal foils carrying a catalyst such as platinum.

[0003] Patent Document 1 discloses a catalytic device in which a large number of through holes are provided in the metal foil that constitutes the honeycomb core in order to increase the surface area of ​​the honeycomb core and to suppress thermal distortion caused by internal temperature differences and the phenomenon in which the metal foil stretches due to the volume expansion of the oxide coating formed on the surface of the metal foil. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5199291 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the honeycomb core of Patent Document 1 has an area where densely packed through holes arranged in the same checkerboard pattern are adjacent to an area where no through holes are arranged at all, which creates a difference in strength of the metal foil at the boundary, necessitating some ingenuity to maintain the durability of the honeycomb core.

[0006] The object of the present invention is to solve the above-mentioned problems of the conventional technology and to provide a catalytic converter that can improve the durability of the honeycomb core while maintaining the exhaust gas purification performance, thereby contributing to the mitigation or reduction of the impact of climate change. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention has a first feature in that, in a catalytic device (30) that purifies exhaust gas (G) by passing it through a honeycomb core (31) formed by winding a metal foil (40) on which a catalyst is supported, a plurality of through holes (H) are formed in a portion of the metal foil (40), and a boundary region (C) is provided in the axial direction of the flow of the exhaust gas (G) in the honeycomb core (31, 31a, 31b, 31c, 31d) between a dense region (A) in which the through holes (H) are densely formed and an unformed region (B) in which the through holes (H) are not formed, and the boundary region (C) is configured so that the total area of ​​the through holes (H) gradually decreases from the dense region (A) side toward the unformed region (B) side.

[0008] A second feature is that the boundary region (C) is provided only downstream of the exhaust gas (G) with respect to the dense region (A).

[0009] A third feature is that the boundary region (C) is configured to gradually reduce the total area of ​​the through holes (H) by thinning out the number of the through holes (H).

[0010] Furthermore, a fourth feature is that the through holes (H) are arranged in the dense region (A) with the same diameter and at equal intervals, and the boundary region (C) is configured to gradually reduce the total area of ​​the through holes (H) by gradually reducing the diameter of the through holes (H) while maintaining the arrangement of the through holes (H) in the dense region (A).

[0011] Furthermore, the through holes (H) are arranged in the dense region (A) with the same diameter and at equal intervals, and the boundary region (C) is configured to gradually reduce the total area of ​​the through holes (H) by thinning out the through holes (H) while maintaining the arrangement of the through holes (H) in the dense region (A), and a fifth feature is that no through holes (H) are formed around the through hole (H) closest to the non-region (B).

[0012] Furthermore, a sixth feature is that the boundary region (C) is provided on both the upstream side and downstream side of the exhaust gas (G) with respect to the dense region (A). [Effects of the Invention]

[0013] According to a first feature, in a catalytic converter (30) that purifies exhaust gas (G) by passing it through a honeycomb core (31) formed by winding a metal foil (40) on which a catalyst is supported, a plurality of through holes (H) are formed in a part of the metal foil (40), and in the axial direction of the flow of the exhaust gas (G) in the honeycomb core (31, 31a, 31b, 31c, 31d), A boundary region (C) is provided between a dense region (A) in which the through holes (H) are densely formed and an unformed region (B) in which the through holes (H) are not formed, and the boundary region (C) is configured so that the total area of ​​the through holes (H) gradually decreases from the dense region (A) side to the unformed region (B) side.Therefore, by providing a boundary region between the dense region and the unformed region, it is possible to suppress a decrease in strength at the transition portion between the dense region and the unformed region compared to a configuration in which the dense region and the unformed region are in contact, and to increase the durability of the honeycomb core.

[0014] According to the second feature, since the exhaust gas (G) is only provided downstream of the dense region (A), the exhaust gas is diffused in the dense region to increase the purification efficiency, and the decrease in strength of the honeycomb core in the boundary region can be suppressed.

[0015] According to a third feature, the boundary region (C) is configured to gradually reduce the total area of ​​the through holes (H) by thinning out the number of the through holes (H), thereby reducing the number of processing pins used to form through holes in the honeycomb core.

[0016] According to a fourth feature, the through holes (H) have the same diameter and are arranged at equal intervals in the dense region (A), and the boundary region (C) is configured to gradually reduce the total area of ​​the through holes (H) by gradually reducing the hole diameter of the through holes (H) while maintaining the arrangement of the through holes (H) in the dense region (A).Therefore, the diffusion effect of the through holes can be maintained while suppressing a decrease in strength of the honeycomb core in the boundary region.

[0017] According to a fifth feature, the through holes (H) have the same diameter and are arranged at equal intervals in the dense region (A), and the boundary region (C) is configured to gradually reduce the total area of ​​the through holes (H) by thinning out the through holes (H) while maintaining the arrangement of the through holes (H) in the dense region (A).Since the through holes (H) are not formed around the through holes (H) closest to the non-region (B), a decrease in strength of the honeycomb core in the boundary region can be suppressed by not providing through holes around the through holes closest to the non-region.

[0018] According to the sixth feature, the boundary region (C) is provided on both the upstream and downstream sides of the exhaust gas (G) relative to the dense region (A), so that a decrease in strength of the honeycomb core in the boundary region can be suppressed on the upstream and downstream sides of the dense region. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a left side view of an exhaust system to which a catalytic device according to an embodiment of the present invention is applied. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. [Figure 4]FIG. 2 is a front view showing the structure of the honeycomb core. [Figure 5] FIG. 2 is a partially enlarged perspective view showing the structure of a honeycomb core. [Figure 6] FIG. 2 is a side view of a honeycomb core 31 according to one embodiment of the present invention. [Figure 7] FIG. 3 is a side view of a honeycomb core according to a first modified example of the present embodiment. [Figure 8] FIG. 10 is a side view of a honeycomb core according to a second modified example of the present embodiment. [Figure 9] FIG. 10 is a side view of a honeycomb core according to a third modified example of the present embodiment. [Figure 10] FIG. 10 is a partially enlarged side view of a honeycomb core according to a fourth modified example of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Figure 1 is a left side view of an exhaust system 1 to which a catalytic converter 30 according to one embodiment of the present invention is applied. The directional arrows in the figure correspond to the direction of a vehicle, such as a motorcycle, to which the exhaust system 1 is attached.

[0021] The exhaust system 1 has an exhaust pipe 2 attached to the cylinder head of an internal combustion engine (not shown), a catalyst housing section 4 connected to the rear of the exhaust pipe 2, and a muffler 6 connected to the rear of the catalyst housing section 4. The catalyst housing section 4 and the muffler 6 are provided with plate-shaped stays 3, 5 for fixing the exhaust system 1 to the vehicle. Exhaust gas G from the internal combustion engine is sent to the catalyst housing section 4 through the exhaust pipe 2, purified by a catalytic converter 30 housed in the catalyst housing section 4, and then silenced by the muffler 6 before being discharged rearward.

[0022] Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. Fig. 3 is a perspective view of the catalytic converter 30. The same reference numerals as those used above indicate the same or equivalent parts. In Fig. 2, the directional arrows "front" and "rear" correspond to the upstream and downstream sides of the exhaust gas G, respectively.

[0023] The catalytic converter 30, which is substantially cylindrical, has a configuration in which a cylindrical honeycomb core 31 is housed in a cylindrical outer cylinder 32. A front tapered pipe 9, which continues to the exhaust pipe 2, is connected to the front end of the outer cylinder 32. Meanwhile, a rear tapered pipe 11, which continues to a tail pipe 12, is connected to the rear end of the outer cylinder 32. The radial outside of the outer cylinder 32 is wrapped with a heat insulating pipe 10, which constitutes the catalyst storage section 4, and the front end of the heat insulating pipe 10 is connected to the exhaust pipe 2 via an outer tapered pipe 8.

[0024] FIG. 4 is a front view showing the structure of honeycomb core 31. Honeycomb core 31 has a honeycomb structure formed by winding metal foil 40, which is made by overlapping flat foil 41 and corrugated foil 42, each supporting a catalyst such as platinum, multiple times. Flat foil 41 and corrugated foil 42 can be formed, for example, from ferritic stainless steel with a thickness of 30 to 100 μm. Honeycomb core 31 is manufactured by overlapping flat foil 41 and corrugated foil 42, each with a brazing material such as nickel brazing material placed in a predetermined position, to form metal foil 40, and then storing this wound metal foil 40 in outer cylinder 32, which is then heated in a vacuum furnace for vacuum brazing.

[0025] FIG. 5 is a partially enlarged perspective view showing the structure of the honeycomb core 31. The same reference numerals as those used above indicate the same or equivalent parts. The flat foil 41 and the corrugated foil 42 are joined to each other by brazing at the apexes of the peaks and valleys of the corrugated foil 42. A plurality of through holes H are formed in each of the flat foil 41 and the corrugated foil 42. These through holes H are provided to prevent thermal strain caused by temperature differences inside the honeycomb core 31 and to prevent the metal foil 40 itself from stretching due to the volume expansion of the oxide film formed on the surface of the metal foil 40. This structure also increases the surface area of ​​the catalyst that comes into contact with exhaust gas, contributing to an improved purification rate.

[0026] Here, for example, if a region where through holes H are densely formed is adjacent to a region where no through holes H are formed at all, there is a problem that a difference in strength of the metal foil 40 occurs at the boundary between the two regions, and some ingenuity is required to maintain the durability of the honeycomb core 31. To address this problem, the present invention is characterized in that a boundary region is provided between the dense region where through holes H are densely formed and the non-region where no through holes H are formed, and the total area of ​​the through holes H in this boundary region gradually decreases from the dense region side toward the non-region side, thereby increasing the strength of the transition portion between the dense region and the non-region and improving the durability of the honeycomb core.

[0027] 6 is a side view of a honeycomb core 31 according to one embodiment of the present invention. In this embodiment, the cylindrical honeycomb core 31 is provided with a dense region A in which through holes H are densely formed, a non-region B in which no through holes H are formed, and a boundary region C disposed downstream of the dense region A and between the non-region B. In the dense region A, a plurality of through holes H are arranged at equal intervals and each having the same diameter. In the boundary region C, the total area of ​​the through holes H gradually decreases from the dense region A side to the non-region B side.

[0028] More specifically, in the boundary region C, the total area of ​​the through holes H is gradually reduced by thinning out the number of through holes H. This makes it possible to suppress a decrease in strength at the transition portion between the dense region A and the non-region B, and to increase the durability of the honeycomb core 31, compared to a configuration in which the dense region A and the non-region B are adjacent. Furthermore, by providing the boundary region C only downstream of the exhaust gas G relative to the dense region A, it is possible to diffuse the exhaust gas G in the dense region A to increase the purification efficiency and to increase the strength of the honeycomb core 31 in the boundary region C. By thinning out the number of through holes H to gradually reduce the total area of ​​the through holes H, it is possible to reduce the number of machining pins used to form the through holes H in the honeycomb core 31.

[0029] Furthermore, in this embodiment, the boundary region C is configured to gradually reduce the total area of ​​the through holes H by thinning out the through holes H while maintaining the arrangement of the through holes H in the dense region A, and no through holes H are provided around the through hole H closest to the non-region B. This makes it possible to further increase the strength of the honeycomb core 31 in the boundary region C.

[0030] Fig. 7 is a side view of a honeycomb core 31a according to a first modified example of this embodiment. This first modified example differs from the embodiment shown in Fig. 6 in the way in which the through holes H are thinned out in the boundary region C. The way in which the through holes H are thinned out can be modified in various ways, such as thinning out one by one or thinning out two adjacent holes.

[0031] Fig. 8 is a side view of a honeycomb core 31b according to a second modified example of this embodiment. In this second modified example, the method of thinning out the through holes H in the boundary region C is different from the embodiment shown in Fig. 6 and the first modified example shown in Fig. 7. In this second modified example, no through holes H are provided around the through hole H closest to the non-region B. The method of thinning out the through holes H can be modified in various ways, such as linearly increasing the thinning amount for each row from the upstream side to the downstream side when the rows of the through holes H are represented in the left-right direction in the figure, or gradually increasing the thinning amount every two rows.

[0032] 9 is a side view of a honeycomb core 31c according to a third modified example of this embodiment. This third modified example is characterized in that the boundary region C is provided on both the upstream side and downstream side of the exhaust gas G relative to the dense region A. This makes it possible to increase the strength of the honeycomb core 31c in the boundary region C on the upstream side and downstream side of the dense region A.

[0033] 10 is a partially enlarged side view of a honeycomb core 31d according to a fourth modified example of this embodiment. In this fourth modified example, the boundary region C is configured such that the diameters of the through holes H are gradually reduced (H1, H2, H3) while maintaining the arrangement of the through holes H in the dense region A, thereby gradually reducing the total area of ​​the through holes H. This makes it possible to increase the strength of the honeycomb core 31d in the boundary region C while maintaining the diffusion effect of the through holes H. In this modified example, the through holes H have the same diameter and are arranged at equal intervals in the dense region A, but the arrangement of the through holes H in the dense region A can be modified in various ways. Furthermore, the hole diameter reduction pattern may be such that the diameter decreases linearly for each row, or may be such that the diameter decreases stepwise, for example, every two rows.

[0034] The form of the vehicle to which the exhaust system is attached, the shape and structure of the exhaust system, the shape and arrangement of the catalytic converter, the materials of the flat and corrugated foils that make up the metal foil of the honeycomb core, the shape and structure of the honeycomb core, the arrangement pattern of the through holes, the shape and size of the through holes, the number of through holes, etc. are not limited to the above-described embodiment and can be modified in various ways. For example, the catalytic converter is not limited to being cylindrical, but may have an elliptical cross section, etc. The catalytic converter of the present invention can be applied to exhaust systems not only for motorcycles but also for vehicles such as three-wheeled and four-wheeled vehicles, and various devices powered by internal combustion engines. [Explanation of symbols]

[0035] 1...exhaust device, 30...catalytic device, 31, 31a, 31b, 31c, 31d...honeycomb core, 32...outer cylinder, 40...metal foil, 41...flat foil, 42...corrugated foil, A...dense region, B...non-region, C...boundary region, H...through hole, G...exhaust gas

Claims

1. A catalytic converter (30) for purifying exhaust gas (G) by passing it through a honeycomb core (31, 31a, 31b, 31c, 31d) formed by winding a metal foil (40) carrying a catalyst, A plurality of through holes (H) are formed in a part of the metal foil (40), In the axial direction of the honeycomb core (31, 31a, 31b, 31c, 31d) in which the exhaust gas (G) flows, a boundary region (C) is provided between a dense region (A) in which the through holes (H) are densely formed and a no region (B) in which the through holes (H) are not formed, A catalytic device characterized in that the boundary region (C) is configured so that the total area of ​​the through holes (H) gradually decreases from the dense region (A) side to the non-region (B) side.

2. 2. The catalytic converter according to claim 1, wherein the boundary region (C) is provided only downstream of the dense region (A) in the direction of the exhaust gas (G).

3. A catalytic converter according to claim 1 or 2, characterized in that the boundary region (C) is configured to gradually reduce the total area of ​​the through holes (H) by thinning out the number of the through holes (H).

4. The through holes (H) have the same diameter and are arranged at equal intervals in the dense region (A), A catalytic device as described in claim 1 or 2, characterized in that the boundary region (C) is configured to gradually reduce the total area of ​​the through holes (H) by gradually reducing the hole diameter of the through holes (H) while maintaining the arrangement of the through holes (H) in the dense region (A).

5. The through holes (H) have the same diameter and are arranged at equal intervals in the dense region (A), the boundary region (C) is configured to gradually reduce the total area of ​​the through holes (H) by thinning out the through holes (H) while maintaining the arrangement of the through holes (H) in the dense region (A), 4. The catalytic converter according to claim 3, wherein no through holes (H) are formed around the through hole (H) located closest to the non-existent region (B).

6. 2. The catalytic converter according to claim 1, wherein the boundary region (C) is provided both upstream and downstream of the dense region (A) in the direction of the exhaust gas (G).

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