Catalytic converter

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 catalyst device, and more particularly to a catalyst device having a honeycomb core formed by laminating metal foils carrying a catalyst.

Background Art

[0002] Conventionally, efforts aimed at mitigating or reducing the impact of climate change have been continued, and research and development regarding emission improvement have been conducted towards its realization. Here, in a catalyst device for purifying exhaust gas of an internal combustion engine, it is known to use a honeycomb core formed by laminating metal foils carrying a catalyst such as platinum.

[0003] In Patent Document 1, in addition to increasing the surface area of the honeycomb core, in order to suppress the thermal strain phenomenon caused by the internal temperature difference and the phenomenon in which the metal foil extends due to the volume expansion of the oxide film formed on the surface of the metal foil, a catalyst device in which a large number of through-holes are provided in the metal foil constituting the honeycomb core is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the honeycomb core of Patent Document 1, since a region where through-holes are densely provided in the same pattern in a grid pattern and a region where no through-holes are provided are in contact with each other, there is a problem that a difference in strength of the metal foil occurs at the boundary portion and a device for maintaining the durability of the honeycomb core is required.

[0006] The object of the present invention is to solve the problems of the prior art described above and to provide a catalytic converter that can improve the durability of the honeycomb core while maintaining exhaust gas purification performance. Ultimately, this will contribute to mitigating or reducing the impact of climate change. [Means for solving the problem]

[0007] To achieve the above objective, the present invention provides a catalytic device (30) for purifying exhaust gas (G) by passing it through a honeycomb core (31) formed by winding a metal foil (40) on which a catalyst is supported, wherein a plurality of through holes (H) are formed in a part of the metal foil (40), and a boundary region (C) is provided between a dense region (A) in which the through holes (H) are densely formed and a non-dense region (B) in which the through holes (H) are not formed, in the axial direction of the flow of the exhaust gas (G) in the honeycomb core (31, 31a, 31b, 31c, 31d), and the boundary region (C) is configured such that the total area of ​​the through holes (H) gradually decreases from the dense region (A) side to the non-dense region (B) side.

[0008] Furthermore, a second characteristic is that the boundary region (C) is provided only on the downstream side of the exhaust gas (G) relative to the dense region (A).

[0009] Furthermore, a third feature is that the boundary region (C) is configured to gradually reduce the total area of ​​the through holes (H) by reducing the number of 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 from one another, and the boundary region (C) is configured to gradually reduce the total area of ​​the through holes (H) by gradually decreasing 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 from one another, 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-holes (H) that are closest to the empty region (B).

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

[0013] According to the first feature, 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 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 a non-dense region (B) in which the through-holes (H) are not 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 to the non-dense region (B) side. By providing a boundary region between the dense region and the non-dense region, it is possible to suppress the decrease in strength at the transition point between the dense region and the non-dense region, and to improve the durability of the honeycomb core, compared to a configuration in which the dense region and the non-dense region are in contact.

[0014] According to the second feature, since it is provided only downstream of the exhaust gas (G) with respect to the dense region (A), it is possible to diffuse the exhaust gas in the dense region to improve the purification efficiency, while suppressing the reduction in the strength of the honeycomb core in the boundary region.

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

[0016] According to the fourth feature, the through-holes (H) are arranged in the dense region (A) with the same diameter and at equal intervals from one another, and the boundary region (C) is configured to gradually reduce the total area of ​​the through-holes (H) by gradually decreasing the diameter of the through-holes (H) while maintaining the arrangement of the through-holes (H) in the dense region (A). This makes it possible to suppress the reduction in strength of the honeycomb core in the boundary region while maintaining the diffusion effect by the through-holes.

[0017] According to the fifth feature, the through holes (H) are arranged in the dense region (A) with the same diameter and at equal intervals from one another, 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 no through holes (H) are formed around the through holes (H) closest to the empty region (B). Therefore, by not providing through holes around the through holes closest to the empty region, a reduction in the strength of the honeycomb core in the boundary region can be suppressed.

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

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

Embodiments for Carrying Out the Invention

[0020] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a left side view of an exhaust device 1 to which a catalyst device 30 according to an embodiment of the present invention is applied. The direction arrows in the figure correspond to the direction of a vehicle such as a motorcycle to which the exhaust device 1 is attached.

[0021] The exhaust device 1 has an exhaust pipe 2 attached to the cylinder head of an internal combustion engine (not shown), a catalyst housing portion 4 connected to the rear portion of the exhaust pipe 2, and a muffler 6 connected to the rear portion of the catalyst housing portion 4. Plate-like stays 3 and 5 for fixing the exhaust device 1 to the vehicle are provided on the catalyst housing portion 4 and the muffler 6. The exhaust gas G of the internal combustion engine passes through the exhaust pipe 2 and is sent to the catalyst housing portion 4, purified by the catalyst device 30 housed in the catalyst housing portion 4, and then silenced by the muffler 6 and discharged rearward.

[0022] FIG. 2 is a sectional view taken along line II-II of FIG. 1. Further, FIG. 3 is a perspective view of the catalyst device 30. The same reference numerals as above indicate the same or equivalent parts as above. In FIG. 2, the “front” and “rear” of the direction arrows respectively correspond to the upstream side and the downstream side of the exhaust gas G.

[0023] The catalytic converter 30, which is roughly cylindrical in shape, has a cylindrical honeycomb core 31 housed in a cylindrical outer cylinder 32. A front tapered pipe 9, which is connected to the exhaust pipe 2, is connected to the front end of the outer cylinder 32. On the other hand, a rear tapered pipe 11, which is connected to the tailpipe 12, is connected to the rear end of the outer cylinder 32. The radially outer side of the outer cylinder 32 is wrapped with a heat shield pipe 10 that constitutes the catalytic converter housing section 4, and the front end of the heat shield pipe 10 is connected to the exhaust pipe 2 via an outer tapered pipe 8.

[0024] Figure 4 is a front view showing the structure of the honeycomb core 31. The honeycomb core 31 is formed by winding multiple times a metal foil 40, which is made up of flat foils 41 and corrugated foils 42 supporting a catalyst such as platinum, onto each other. The flat foils 41 and corrugated foils 42 can be made from, for example, ferritic stainless steel with a thickness of 30 to 100 μm. The honeycomb core 31 is manufactured by stacking flat foils 41 and corrugated foils 42 with brazing material such as nickel brazing material placed in predetermined positions to form the metal foil 40, winding this metal foil 40 and housing it in an outer cylinder 32, and then heating it in a vacuum furnace to perform vacuum brazing.

[0025] Figure 5 is a partially enlarged perspective view showing the structure of the honeycomb core 31. The same reference numerals indicate the same or equivalent parts. The flat foil 41 and the corrugated foil 42 are joined to each other by brazing at the peaks and valleys of the corrugated foil 42. Multiple through holes H are formed in both 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 volume expansion of the oxide film formed on the surface of the metal foil 40. Furthermore, this structure allows for a larger surface area of ​​the catalyst that comes into contact with the exhaust gas, contributing to an improved purification rate.

[0026] Here, for example, if a region with densely packed through-holes H is in contact with a region with no through-holes H at all, there is a problem that a difference in strength of the metal foil 40 occurs at the boundary between the two regions, requiring measures to maintain the durability of the honeycomb core 31. In response to this problem, the present invention features a boundary region between a dense region where through-holes H are densely formed and a region where through-holes H are not formed, and in this boundary region, the total area of ​​through-holes H gradually decreases from the dense region side to the region without through-holes. This increases the strength of the transition area between the dense region and the region without through-holes, thereby improving the durability of the honeycomb core.

[0027] Figure 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 in the axial direction of the flow of exhaust gas G, a non-dense region B in which no through holes H are formed, and a boundary region C disposed between the dense region A and the non-dense region B on the downstream side of the dense region A. In the dense region A, multiple through holes H are arranged, each with the same diameter and at equal intervals from one another. In the boundary region C, the total area of ​​the through holes H is configured to gradually decrease from the dense region A side to the non-dense region B side.

[0028] More specifically, in boundary region C, the total area of ​​through-holes H is reduced by thinning out the number of through-holes H. This suppresses the decrease in strength at the transition point between dense region A and non-dense region B, compared to a configuration where dense region A and non-dense region B are in contact, thereby increasing the durability of the honeycomb core 31. Furthermore, by providing boundary region C only on the downstream side of the exhaust gas G relative to dense region A, it is possible to diffuse the exhaust gas G in dense region A to improve purification efficiency, while also increasing the strength of the honeycomb core 31 in boundary region C. By thinning out the number of through-holes H to gradually reduce the total area of ​​through-holes H, the number of processing pins required to form through-holes H in the honeycomb core 31 can be reduced.

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

[0030] Figure 7 is a side view of the honeycomb core 31a according to the first modified example of this embodiment. This first modified example differs from the embodiment shown in Figure 6 in how the through-holes H in the boundary region C are thinned out. Various variations are possible in how the through-holes H are thinned out, such as thinning them out one by one or thinning out two adjacent holes.

[0031] Figure 8 is a side view of a honeycomb core 31b according to a second modification of this embodiment. In this second modification, the method of thinning out the through-holes H in the boundary region C is different from the embodiment shown in Figure 6 and the first modification shown in Figure 7. In this second modification, through-holes H are not provided around the through-hole H that is closest to the non-existent region B. When the left-right direction in the figure is considered as a row of through-holes H, various modifications are possible, such as linearly increasing the thinning amount for each row from the upstream side to the downstream side, or gradually increasing the thinning amount every two rows.

[0032] Figure 9 is a side view of a honeycomb core 31c according to a third modification of this embodiment. This third modification is characterized in that the boundary region C is provided on both the upstream and downstream sides 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 both the upstream and downstream sides of the dense region A.

[0033] Figure 10 is a partially enlarged side view of the honeycomb core 31d according to a fourth modified example of this embodiment. In this fourth modified example, the boundary region C is configured to gradually reduce the total area of ​​the through-holes H by gradually decreasing the diameter of the through-holes H (H1, H2, H3) while maintaining the arrangement of the through-holes H in the dense region A. This makes it possible to increase the strength of the honeycomb core 31d in the boundary region C while maintaining the diffusion effect by the through-holes H. In this modified example as well, the through-holes H are arranged in the dense region A with the same diameter and at equal intervals from one another, but the arrangement of the through-holes H in the dense region A can be modified in various ways. In addition, the pattern of decreasing the diameter of the holes can be linearly reduced row by row, or for example, gradually reduced 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 constituting 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 embodiment and can be modified in various ways. For example, the catalytic converter is not limited to a cylindrical shape, but may have a shape with an elliptical cross-section, etc. The catalytic converter according to the present invention is not limited to motorcycles, but can be applied to vehicles such as three-wheeled vehicles and four-wheeled vehicles, and to exhaust systems of various devices powered by internal combustion engines. [Explanation of symbols]

[0035] 1... Exhaust system, 30... Catalytic converter, 31, 31a, 31b, 31c, 31d... Honeycomb core, 32... Outer cylinder, 40... Metal foil, 41... Flat foil, 42... Corrugated foil, A... Dense region, B... Undense region, C... Boundary region, H... Through hole, G... Exhaust gas

Claims

1. In a catalytic converter (30) that purifies exhaust gas (G) by passing it through a honeycomb core (31, 31a, 31b, 31c, 31d) formed by winding a metal foil (40) on which a catalyst is supported, A portion of the metal foil (40) has multiple through holes (H) formed in it. 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 a region (B) in which the through holes (H) are not formed. The dense region (A) is located downstream in the flow direction of the exhaust gas (G), and the non-dense region (B) is located upstream. The catalyst device is characterized in that the boundary region (C) is configured such that the sum of the pore areas for each cross-section along the axial direction gradually decreases, and the total area of ​​the through-holes (H) in the boundary region (C) decreases.

2. The catalytic converter according to claim 1, characterized in that the boundary region (C) is provided only on the downstream side of the exhaust gas (G) with respect to the dense region (A).

3. The catalyst apparatus 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 reducing the number of through holes (H).

4. The through holes (H) are arranged in the dense region (A) with the same diameter and at equal intervals from one another. The catalyst apparatus 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 gradually decreasing the 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) are arranged in the dense region (A) with the same diameter and at equal intervals from one another. 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). The catalyst apparatus according to claim 3, characterized in that no through-hole (H) is formed around the through-hole (H) that is closest to the non-existent region (B).

6. The catalyst device according to claim 1, characterized in that the boundary region (C) is provided both upstream and downstream of the exhaust gas (G) with respect to the dense region (A).

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