JPH0730314U - Exhaust gas catalytic device - Google Patents

Abstract

(57) [Abstract] [Purpose] The present invention focuses on good temperature rising characteristics of a thin honeycomb body, and prevents the temperature drop by adjusting the axial length of the thin honeycomb body or further. Provided is an exhaust gas catalyst carrier capable of activating a catalytic action and improving efficiency. [Structure] A corrugated foil and a flat foil are alternately laminated and spirally wound or laminated, and a honeycomb body that joins the contact portions of both foils is formed into a thin shape with an axial length of 30 mm or less, An exhaust gas catalyst device comprising a plurality of the honeycomb bodies, each of which is housed and fixed at a predetermined interval in an outer cylinder,
Further, a heat insulating material is attached to the inner peripheral surface of the space between the honeycomb bodies to prevent a temperature drop in the space.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a catalyst device that is installed in an engine exhaust gas system such as an automobile and purifies exhaust gas.

[0002]

[Prior art]

 Metal carriers used for purifying automobile engine exhaust gas have excellent properties such as pressure loss, heat resistance, and mountability, and their use is increasing in recent years.

In a conventional metal carrier, as shown in FIG. 5, a metal flat foil 1 and a corrugated foil 2 obtained by corrugating the same are superposed and spirally wound to form a honeycomb body 3. The honeycomb body 3 is formed by inserting it into an outer cylinder 4 made of metal. The joining 5 of the contact portion between the flat foil 1 and the corrugated foil 2 which form the honeycomb body 3 is performed, for example, by mainly the brazing material at the upper and lower end portions and the outer peripheral portion of the honeycomb body 3, and the outer periphery of the honeycomb body 3 and the outer cylinder 4 are joined together. The inner circumference is also usually joined 6 by brazing material.

A catalytic metal is carried on the surface of the cells (the space divided by the flat foil and the corrugated foil in the axial direction of the honeycomb body) formed in the honeycomb body, and the exhaust gas entering the honeycomb body flows into the communicating cells. While being contacted with the catalytic metal and being reformed, it is discharged while passing through.

The exhaust gas discharged from the engine during operation has a large temperature change depending on the operating condition of the automobile, and the metal carrier in the exhaust gas system is repeatedly subjected to a rapid heat-quench heat cycle. Therefore, in the metal carrier mounted in such an environment, the flat foil and the corrugated foil which compose it are repeatedly expanded and contracted to cause distortion, and in particular, the rigid joint portion between the outer cylinder and the honeycomb body is formed. A long single honeycomb body is likely to be damaged in the radial direction and also in the axial direction depending on the joining method of the flat foil and the corrugated foil due to thermal strain, resulting in a problem that the service life is shortened.

In order to solve such a problem, various proposals have been made to improve the joining method in each of them. On the other hand, the honeycomb body has a short length (thin shape), and the plurality of thin honeycomb body members are respectively held. Japanese Patent Laid-Open No. 2-180624 discloses a metal carrier which is housed in an outer cylinder via the metal tube. In a metal carrier having such a structure that a plurality of thin honeycomb bodies are not directly bonded to the outer cylinder, it is possible to reduce the occurrence of defects due to thermal strain.

Further, a certain temperature (for example, 350 ° C.) is required for the catalyst to start its action. In the metal carrier in which the thin honeycomb bodies are arranged in multiple stages in the outer cylinder, the most upstream honeycomb body has the best contact with the unpurified exhaust gas, so that the temperature rising characteristics are good. Generally, when the engine is started, the temperature of the honeycomb body is not high enough to exert a catalytic action, and the initial exhaust gas purifying ability is low, but the thin honeycomb body has good temperature rising characteristics as described above. The initial purification capacity can be improved.

[0008]

[Problems to be solved by the device]

 However, even a thin honeycomb body has a problem that, depending on the axial length, a nonuniform flow occurs in the cell, the catalytic reaction becomes nonuniform, and the exhaust gas purification efficiency decreases. In order to eliminate such uneven flow in the cells, there is also a method of providing a large number of openings in the flat foil or corrugated foil that constitutes the honeycomb body cells, but stress concentrates near the openings and the honeycomb body Strength is reduced and life is shortened. The present invention is intended to solve such a problem, and by focusing on the good temperature rising characteristics of the above-mentioned thin honeycomb body, by adjusting the axial length of the thin honeycomb body. Alternatively, it is still another object of the present invention to provide an exhaust gas catalyst carrier which can prevent a temperature drop and activate a catalytic action to improve efficiency.

[0009]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention provides a honeycomb body having a corrugated foil and a flat foil which are alternately superposed and spirally wound or laminated, and the contact portions of both foils are joined to each other in an axial length of 30 mm. The exhaust gas catalyst device is characterized in that the honeycomb body is formed in the following thin shape, and a plurality of the honeycomb bodies are housed and fixed in the outer cylinder with a predetermined space, respectively, and a space portion between the honeycomb bodies. The exhaust gas catalyst device according to claim 1, wherein a heat insulating material is attached to the inner surface of the outer periphery of the exhaust gas catalyst device.

The present invention will be described in detail below based on the embodiments shown in the drawings. FIG. 1 shows a cross-section of the present invention. Reference numeral 7 is a thin honeycomb body formed by alternately laminating corrugated foils 2 and flat foils 1 and spirally winding or laminating them, and 8 is a thin honeycomb body 7. The outer cylinder accommodates a plurality of (7a to 7n) with a space s held between the thin honeycomb bodies. The contact portion between the corrugated foil and the flat foil forming the thin honeycomb body 1, and the outer periphery of the thin honeycomb body 7 and the inner periphery of the outer cylinder 8 are joined by means such as brazing or spread joining as is conventionally done. To do.

The honeycomb body 7 used in the present invention is thin so that its axial length is 30 mm or less. Exhaust gas passes through the passage (cell) 9 composed of the flat foil 1 and the corrugated foil 2 when the engine is in operation, but the exhaust gas passing through the cell 9 having a small cross-sectional area forms a laminar flow parallel to the traveling direction. However, as schematically shown in FIG. 2, a stagnation portion of the gas is generated during the progress of the gas, which forms the laminar boundary layer 10 and gradually increases to the downstream side. That is, the laminar flow boundary layer 10 causes the flow gas to flow in a non-uniform manner, resulting in non-uniform contact with the catalyst, which causes reduction in catalyst efficiency. The formation of such a laminar boundary layer depends on the type and temperature of the gas, but the distance from the cell inlet has a great influence, and the degree of development changes depending on the distance. From the results of various experiments conducted by the present inventors, it has been found that the cell length limit for suppressing the formation of such a laminar boundary layer should not exceed 30 mm. However, if the length is made too short, there is a problem in the strength or manufacturing of the honeycomb body itself, so it is preferable to make it 10 mm abnormal.

On the other hand, coupled with the fact that the initial temperature of exhaust gas at the time of engine start is low, it takes time for the carrier to reach the temperature at which the catalyst reaction is activated. It takes more time for the non-thin metal carrier to reach a high temperature in the entire downstream region, and during that time, unpurified exhaust gas is emitted. In particular, due to the gas flow, the temperature rises quickly in the central part of the honeycomb body, but on the outer peripheral side close to the outer cylinder, a temperature gradient is formed that the temperature rise is delayed, and the purification action is delayed.

Since the honeycomb body of the present invention is thin as described above, heat transfer in the radial direction is relatively fast, and a plurality of thin honeycomb bodies 7a to 7n are provided with a space (s) s between each honeycomb body. Since the gas is mixed and homogenized in this space because it is provided, the first honeycomb body 7a particularly plays a role of a header, and the gas is mixed in the space s to promote temperature equalization, so that the honeycomb on the downstream side is promoted. Body temperature is fast. Therefore, the emission of unpurified gas during the engine starting period can be reduced. In order to achieve such an effect, it is necessary to enlarge the space to some extent, and in the present invention, it is preferable that the honeycomb body space is approximately 10 mm or more.

FIG. 3 shows another embodiment of the present invention, in which a heat insulating material 11 is provided at a portion corresponding to each space (space) s on the inner circumference of the outer cylinder 8. That is, since the outer circumference of the outer cylinder 8 is exposed to the outside air, the amount of heat released is large, and in particular, in order to equalize the temperature of the gas in the space, it is effective to prevent the temperature drop in this part. It is preferable to install a heat insulating material. The heat insulating material 11 may be made of the same metal as that of the outer cylinder 8 to form a double structure in this portion, or may be made of a heat-resistant resin having low heat conductivity or another metal, and is not particularly limited.

Further, the present invention can be applied not only to the straight pipe portion but also to the curved pipe portion. FIG. 4 shows an example of use in the curved pipe section 12, in which a plurality of thin honeycomb bodies 7 are arranged in tandem at intervals s. In this way, it is possible to mount it at any position in the exhaust gas system.

[0016]

[Effect of device]

 As described above, according to the present invention, since the honeycomb body is made thin and a plurality of honeycomb bodies are arranged in the outer cylinder at intervals, the uneven flow of the exhaust gas is eliminated, and the unbalanced heat is equalized to purify the exhaust gas. Improve efficiency. Especially, even when the engine is started, the purification effect of exhaust gas is not reduced. In addition, since the uneven flow causes the uneven distribution of thermal stress, the thin structure further reduces the accumulation of thermal stress in the axial direction and significantly extends the life of the carrier. In addition, in the present invention, since a plurality of spaces formed between the honeycomb bodies are formed, it also has an effect of reducing the rubbing sound generated on the walls of the honeycomb body.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an explanatory view schematically showing a gas flow in a honeycomb body cell part.

FIG. 3 is a sectional view showing another embodiment of the present invention.

FIG. 4 is a sectional view showing an example of use of the present invention.

FIG. 5 is an explanatory view of a conventional metal carrier with a partial cross section.

[Explanation of symbols]

 1: Flat foil 2: Corrugated foil 3: Honeycomb body 4, 8: Outer cylinder 5,6: Joined portion 7: Thin honeycomb body 9: Cell 10: Laminar flow boundary portion 11: Heat insulating material 12: Curved pipe portion

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI technical display location B01J 35/04 321 A 8017-4G (72) Creator Toshikazu Nakagawa 5-3 Tokai-cho, Tokai-shi, Aichi Nippon Steel Co., Ltd. Inside the Nagoya Works (72) Inventor Toshihiro Takada 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd.

Claims (2)

[Scope of utility model registration request] 1. A honeycomb body, in which corrugated foils and flat foils are alternately superposed and spirally wound or laminated, and a contact portion of both foils is joined, is formed into a thin shape having an axial length of 30 mm or less. Then
An exhaust gas catalyst device, wherein a plurality of the honeycomb bodies are housed and fixed in an outer cylinder at predetermined intervals. 2. The exhaust gas catalyst device according to claim 1, wherein a heat insulating material is attached to the inner surface of the outer periphery of the space between the honeycomb bodies.