Catalyst structure
The catalytic converter addresses pressure fluctuations and thermal stress in honeycomb cores by arranging through holes and brazing strategically, enhancing durability and purification performance.
Patent Information
- Application Number
- JP2023170782
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-09-29
- Publication Date
- 2025-09-12
- Estimated Expiration
- 2043-09-29
AI Technical Summary
Honeycomb cores in catalytic converters with through holes in a grid pattern throughout the metal foil experience large pressure fluctuations, leading to deterioration of brazed parts and reduced durability.
A catalytic converter design with a honeycomb core formed by winding a metal foil, featuring regions with and without through holes, and strategically positioned brazing points to manage pressure and thermal stress, enhancing durability and purification performance.
The design prevents excessive internal pressure and thermal distortion, improving the durability of the honeycomb core while maintaining combustion gas purification efficiency.
Smart Images
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Abstract
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] BACKGROUND ART Conventionally, catalytic converters have been known that purify combustion gases from an internal combustion engine by passing the combustion gases through a honeycomb core made of laminated metal foils carrying a catalyst such as platinum.
[0003] Patent Document 1 discloses a catalytic device in which multiple through holes are provided in the metal foil to suppress two phenomena that tend to occur when used at high temperatures: thermal strain caused by temperature differences inside the honeycomb core, and the phenomenon in which the metal foil itself stretches due to the volume expansion of the oxide film 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 through holes arranged in a grid pattern throughout the entire metal foil, which causes large pressure fluctuations inside the catalytic device when combustion gas flows, and these pressure fluctuations could cause deterioration of the brazed parts of the honeycomb core, posing a problem that measures were needed to address this issue.
[0006] SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a catalytic converter capable of improving the durability of the honeycomb core while maintaining the purification performance of combustion gases. [Means for solving the problem]
[0007] In order to achieve the above object, the present invention provides a catalytic device (30) having a honeycomb core (31) formed by winding a metal foil (40) carrying a catalyst, in which a plurality of through holes (H) are formed in at least a portion of the metal foil (40), and in the flow direction of a combustion gas (G) passing through the honeycomb core (31), a first region (A) in which the through holes (H) are not formed, a second region (B) in which the through holes (H) are formed, and a third region (C) in which the through holes (H) are not formed are arranged in this order from the upstream side, and when the flow direction of the combustion gas (G) is defined as the width direction, the width (TA) of the first region (A) is set smaller than the width (TC) of the third region (C).
[0008] A second feature of the catalytic device (30) is that it has a honeycomb core (31) formed by winding a metal foil (40) carrying a catalyst, and a plurality of through holes (H) are formed in at least a portion of the metal foil (40), and in the flow direction of a combustion gas (G) passing through the honeycomb core (31), there are provided, from the upstream side thereof, a first region (A) in which the through holes (H) are not provided, a second region (B) in which the through holes (H) are provided, and a third region (C) in which the through holes (H) are not provided, from the downstream side thereof, and when the flow direction of the combustion gas (G) is defined as the width direction, the width (TA) of the first region (A) is set smaller than the width (TC) of the third region (C).
[0009] The metal foil (40) is constructed by stacking a flat foil (41) and a corrugated foil (42), and a first brazing portion (51) that joins the flat foil (41) and the corrugated foil (42) is provided at the upstream end of the honeycomb core (31), which is a third feature of the present invention.
[0010] The fourth feature is that the second region (B) is not brazed.
[0011] Furthermore, a fifth feature is that the catalytic converter (30) is provided with a second brazing portion (52) that joins the flat foil (41) and the corrugated foil (42) downstream of the first brazing portion (51), and a third brazing portion (53) that joins the honeycomb core (31) and an outer tube (32) that houses the honeycomb core (31), and the second brazing portion (52) and the third brazing portion (53) overlap each other when viewed from the side of the catalytic converter (30).
[0012] A sixth feature is that the second brazed portion (52) and the third brazed portion (53) are provided at positions closer to the downstream side of the catalytic converter (30).
[0013] A seventh feature is that the width (T2) of the second brazed portion (52) is set smaller than the width (T3) of the third brazed portion (53).
[0014] Furthermore, an eighth feature is that the width (TB) of the second region (B) is set larger than the width (TC) of the third region (C). [Effects of the Invention]
[0015] According to a first feature, a catalytic converter (30) includes a honeycomb core (31) formed by winding a metal foil (40) supporting a catalyst. The metal foil (40) has a plurality of through holes (H) formed in at least a portion thereof. In the flow direction of a combustion gas (G) passing through the honeycomb core (31), a first region (A) without the through holes (H), a second region (B) with the through holes (H), and a third region (C) without the through holes (H) are arranged in this order from upstream to downstream. The width (TA) of the first region (A) is set smaller than the width (TC) of the third region (C) when the flow direction of the combustion gas (G) is defined as the width direction. This allows the combustion gas to diffuse in the upstream first region (A) without the through holes, preventing excessive internal pressure in the catalytic converter, compared to a configuration in which through holes are formed throughout the metal foil. This improves the durability of the honeycomb core while maintaining the combustion gas purification performance.
[0016] According to a second feature, a catalytic converter (30) includes a honeycomb core (31) formed by winding a metal foil (40) supporting a catalyst. The metal foil (40) has a plurality of through holes (H) formed in at least a portion thereof. In the flow direction of a combustion gas (G) passing through the honeycomb core (31), a first region (A) without the through holes (H), a second region (B) with the through holes (H), and a third region (C) without the through holes (H) are formed from the upstream side. The width (TA) of the first region (A) is set smaller than the width (TC) of the third region (C) when the flow direction of the combustion gas (G) is defined as the width direction. This allows the combustion gas to diffuse in the upstream first region without the through holes, preventing excessive internal pressure in the catalytic converter, compared to a configuration in which through holes are formed throughout the metal foil. This improves the durability of the honeycomb core while maintaining the combustion gas purification performance.
[0017] According to the third feature, the metal foil (40) is constructed by stacking a flat foil (41) and a corrugated foil (42), and a first brazing portion (51) that joins the flat foil (41) and the corrugated foil (42) is provided at the upstream end of the honeycomb core (31). This increases the joining strength of the upstream end that is first hit by the combustion gas, and makes it possible to suppress damage to the metal foil.
[0018] According to the fourth feature, since the second region (B) is not brazed, it is possible to avoid pressure fluctuations and stress concentrations that occur when brazing fills the through holes, thereby improving the durability of the catalytic device.
[0019] According to a fifth feature, there is provided a second brazing portion (52) that joins the flat foil (41) and the corrugated foil (42) downstream of the first brazing portion (51), and a third brazing portion (53) that joins the honeycomb core (31) and an outer tube (32) that houses the honeycomb core (31). Since the second brazing portion (52) and the third brazing portion (53) overlap each other in a side view of the catalytic device (30), the second brazing portion suppresses the thermal distortion phenomenon of the honeycomb core at a position closer to the downstream side of the catalytic device, thereby suppressing deformation of the outer tube and increasing the durability of the third brazing portion.
[0020] According to the sixth feature, the second brazing portion (52) and the third brazing portion (53) are provided at a position closer to the downstream side of the catalytic converter (30). By providing the second brazing portion and the third brazing portion at a position closer to the downstream side where the temperature is lower than the upstream side, the third brazing portion can be protected from thermal influences and the honeycomb core can be prevented from coming off the outer tube.
[0021] According to the seventh feature, the width (T2) of the second brazing portion (52) is set smaller than the width (T3) of the third brazing portion (53). Therefore, even if the third brazing portion is affected by thermal distortion, the resulting stress is easily dispersed in the second brazing portion, making it possible to suppress the impact on the honeycomb core.
[0022] According to the eighth feature, the width (TB) of the second region (B) is set larger than the width (TC) of the third region (C), so that the area of the second region in which the through holes are provided can be made sufficiently large, thereby making it possible to maintain the purification performance of the catalytic converter. [Brief explanation of the drawings]
[0023] [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 schematic cross-sectional view showing the structure of a catalytic converter. DETAILED DESCRIPTION OF THE INVENTION
[0024] 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.
[0025] 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. Combustion 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.
[0026] 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 combustion gas G, respectively.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] However, for example, if the through holes H are provided throughout the entire metal foil 40, the pressure fluctuations inside the catalytic device 30 will increase when the combustion gas G flows, and these pressure fluctuations may cause deterioration of the brazed portions of the honeycomb core 31, posing a problem that requires measures to address this issue. To address this problem, the present invention intentionally provides areas where no through holes H are provided, thereby making it possible to increase the durability of the honeycomb core 31 while maintaining the purification performance of the combustion gas G.
[0031] 6 is a schematic cross-sectional view showing the structure of the catalytic device 30. In the honeycomb core 31 according to this embodiment, a first region A where no through holes H are provided, a second region B where the through holes H are provided, and a third region C where no through holes H are provided are arranged in this order from the upstream side of the combustion gas G. When the flow direction of the combustion gas G is taken as the width direction, the honeycomb core 31 is characterized in that the width TA of the first region A is set smaller than the width TC of the third region C.
[0032] As a result, compared to a configuration in which the through holes H are formed throughout the metal foil 40, it is possible to diffuse the combustion gas G in the first region A on the upstream side where the through holes H are not provided, and to prevent the internal pressure of the catalytic device 30 from becoming too high. This makes it possible to improve the durability of the honeycomb core 31 while maintaining the purification performance of the combustion gas G.
[0033] The through holes H may be, for example, 33 rows of 2.2mm diameter circular holes arranged in a staggered pattern. The through holes H may be made smaller in diameter and the number of holes increased, or may have a non-circular shape such as an ellipse. In this embodiment, the width TB of the second region B is set to approximately half the overall width after considering the balance between purification performance and durability.
[0034] Furthermore, the present invention is characterized in that the first brazing portion 51 that joins the flat foil 41 and the corrugated foil 42 is provided at the upstream end of the honeycomb core 31. This increases the joining strength of the upstream end that is first hit by the combustion gas G, making it possible to suppress damage to the metal foil.
[0035] In addition, in this embodiment, no brazing is applied to the second region B where the through-hole H is provided. This makes it possible to avoid pressure fluctuations and stress concentrations that occur when brazing fills the through-hole H, thereby improving the durability of the catalytic device 30.
[0036] The catalytic converter 30 includes a second brazing portion 52 that joins the flat foil 41 and the corrugated foil 42 together at a position closer to the downstream side. The catalytic converter 30 further includes a third brazing portion 53 that joins the honeycomb core 31 to the outer casing 32 that houses the honeycomb core 31. This embodiment is characterized in that the second brazing portion 52 and the third brazing portion 53 overlap each other in a side view of the catalytic converter 30. This allows the second brazing portion 52 to suppress thermal distortion of the honeycomb core 31 at a position closer to the downstream side of the catalytic converter 30, suppress deformation of the outer casing 32, and increase the durability of the third brazing portion 53.
[0037] The second brazed portion 52 and the third brazed portion 53 are provided at positions closer to the downstream side of the catalytic device 30. This prevents the second brazed portion 52 and the third brazed portion 53 from excessively increasing in temperature, and in particular, prevents the second brazed portion 52 from deteriorating and causing the honeycomb core 31 to come off the outer casing 32 of the catalytic device 30.
[0038] Furthermore, the width T2 of the second brazed portion 52 is set smaller than the width T3 of the third brazed portion 53. As a result, even if the third brazed portion 53 is affected by a thermal strain phenomenon, the resulting stress is easily dispersed in the second brazed portion 52, making it possible to protect the honeycomb core 31. Furthermore, since the width TB of the second region B is set larger than the width TC of the third region C, the area of the second region B where the through holes H are provided can be made sufficiently large, making it possible to maintain the purification performance of the catalytic device 30.
[0039] In the above embodiment, the width TA of the first region A and the width T1 of the first brazing portion 51 are set to be the same, but the two widths may be different.
[0040] The configuration 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 honeycomb core metal foil, the widths of the first, second, and third regions, the widths and arrangements of the first, second, and third brazed portions, the shape and size of the through holes, the number of through holes, and other factors are not limited to those described in the above embodiments and can be modified in various ways. For example, the catalytic converter is not limited to a cylindrical shape and may have an elliptical cross section. Furthermore, in the above-described embodiment, the first region without through holes, the second region with through holes, and the third region without through holes are arranged in this order from the upstream side. However, for example, multiple regions without through holes and multiple regions with through holes may be sandwiched between the second and third regions. The catalytic converter according to the present invention can be applied to exhaust systems not only for motorcycles but also for vehicles such as three- and four-wheeled vehicles and various devices powered by internal combustion engines. [Explanation of symbols]
[0041] 1...exhaust device, 30...catalytic device, 31...honeycomb core, 32...outer tube, 40...metal foil, 41...flat foil, 42...corrugated foil, 51...first brazed portion, 52...second brazed portion, 53...third brazed portion, A...first region, B...second region, C...third region, TA...width of first region, TB...width of second region, TC...width of third region, T1...width of first brazed portion, T2...width of second brazed portion, T3...width of third brazed portion, H...through hole, G...combustion gas
Claims
1. A catalyst device (30) having a honeycomb core (31) formed by winding a metal foil (40) carrying a catalyst, A plurality of through holes (H) are formed in at least a part of the metal foil (40), In a flow direction of a combustion gas (G) passing through the honeycomb core (31), a first region (A) in which the through holes (H) are not provided, a second region (B) in which the through holes (H) are provided, and a third region (C) in which the through holes (H) are not provided are arranged in this order from the upstream side, When the flow direction of the combustion gas (G) is defined as a width direction, a width (TA) of the first region (A) is set smaller than a width (TC) of the third region (C), A catalytic converter, wherein the second region (B) is not brazed.
2. A catalyst device (30) having a honeycomb core (31) formed by winding a metal foil (40) carrying a catalyst, A plurality of through holes (H) are formed in at least a part of the metal foil (40), In the flow direction of the combustion gas (G) passing through the honeycomb core (31), a first region (A) in which the through holes (H) are not provided, a second region (B) in which the through holes (H) are provided, and a third region (C) in which the through holes (H) are not provided, are provided from the upstream side, When the flow direction of the combustion gas (G) is defined as a width direction, a width (TA) of the first region (A) is set smaller than a width (TC) of the third region (C), A catalytic converter, wherein the second region (B) is not brazed.
3. The metal foil (40) is constructed by stacking a flat foil (41) and a corrugated foil (42), 3. The catalytic converter according to claim 1, wherein a first brazing portion (51) that joins the flat foil (41) and the corrugated foil (42) is provided at an upstream end of the honeycomb core (31).
4. a second brazing portion (52) that joins the flat foil (41) and the corrugated foil (42) downstream of the first brazing portion (51); a third brazing portion (53) for joining the honeycomb core (31) to an outer cylinder (32) for accommodating the honeycomb core (31); 4. The catalytic converter according to claim 3, wherein the second brazed portion and the third brazed portion overlap each other in the width direction when the flow direction of the combustion gas is defined as the width direction.
5. 5. The catalytic converter according to claim 4, wherein the second brazed portion (52) and the third brazed portion (53) are provided at positions closer to the downstream side of the catalytic converter (30).
6. 5. The catalytic converter according to claim 4, wherein the width (T2) of the second brazed portion (52) is set smaller than the width (T3) of the third brazed portion (53).
7. 3. The catalytic converter according to claim 1, wherein the width (TB) of the second region (B) is set larger than the width (TC) of the third region (C).
Citation Information
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