JPH10180043A - Exhaust gas purifying device for automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To absorb compressive force by thermal expansion and to prevent deformation by specifying the thicknesses of flat foil and corrugated foil wound one to several turns on the outer peripheral side where a honeycomb body is wound and the number of cells per area composed of both foil and specifying likewise the flat foil and corrugated foil wound around the inner side thereof and the number of the cells per area. SOLUTION: The honeycomb body is formed by superposing the flat metallic foil (flat foil) 4 and the corrugated foil 5 formed by working the flat foil to a corrugated shape on each other and spirally winding the foil. One to several turns from the outermost peripheral of the honeycomb body are formed of a soft structure having the rigidity smaller than the that of the inner peripheral side thereof and the larger elastic deformation rate than that of this side. The thicknesses of the flat foil 4 and corrugated foil 5 of the one to several turns on the outer peripheral side 7 are made as small as <=30μm and the number of the cells 6 composed of both foil is specified to 50 to 300cells/in<2> . The thickness of the flat foil 4 and corrugated foil 5 wound on the inner side 8 thereof is specified to 40 to 60μm and the number of the cells composed of both foil is specified to >=400cells/in<2> . As a result, the compression of the honeycomb body by the thermal expansion are absorbed and the deformation thereof are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying exhaust gas of an automobile by mounting and supporting a metal honeycomb body on a casing via an elastic holder without using an outer cylinder.
The present invention relates to a highly durable purifier connected to an exhaust gas system.

[0002]

2. Description of the Related Art As a catalyst carrier installed in an exhaust system for purifying exhaust gas from automobiles, a honeycomb body supporting a catalyst is made of metal instead of ceramic, and recently the amount of the catalyst used has been reduced. Increasing.

A ceramic honeycomb body is mainly composed of cordierite, has high heat resistance and a low coefficient of thermal expansion, but has a mechanical strength of at most 40 kgf / cm ² and is weak against impact. The honeycomb wall thickness which forms becomes as thick as approximately 170 μm, and therefore, the cell opening ratio is only 70%, so that the pressure loss to the exhaust also increases.

On the other hand, the metal honeycomb body is a ferritic stainless steel containing Al and having a thickness of about 50 μm.
It is composed of foil. That is, a flat foil and a corrugated corrugated foil are overlapped and wound to form a honeycomb body. The flat foil and corrugated foil forming the cell have a large cell opening ratio (more than 90%) because of the thin foil. Therefore, the pressure loss is also reduced. Conventionally, a metal carrier is manufactured by loading a metal honeycomb body into a thick metal outer cylinder, bonding and fixing it appropriately with a brazing material or the like, and then carrying a catalyst, and installing and connecting to an exhaust gas system. During operation, heating during operation and cooling during shutdown are repeated, and the amount of heat released from the metal outer cylinder is large, so that the temperature rise of the honeycomb body at startup is delayed and the activation temperature of the catalyst may be delayed. In some cases, inconveniences such as generation of thermal distortion based on a temperature difference in the honeycomb body radial direction may occur.

[0005] In order to solve such inconvenience, it has been proposed to interpose a heat insulating material between the honeycomb body and the casing when loading the metal honeycomb body into the casing without using an outer cylinder. For example, JP-A-1-
Japanese Patent No. 240715 discloses a catalyst in which a catalyst element formed of metal monolithic is positioned in a metal casing, and an elastic body (insulation mat) is interposed between the metal casing and the catalyst element to absorb mechanical and thermal shocks. A converter is disclosed.

Incidentally, such an elastic body has a characteristic of thermally expanding. Therefore, when the temperature becomes high during use, the honeycomb body is thermally expanded to compress the honeycomb body. The body may undergo plastic deformation. The diameter of the honeycomb body that has been plastically deformed at a high temperature is further reduced when it is cooled, and the elastic body also contracts by cooling, so that the adherence of the elastic body supporting the honeycomb body becomes extremely weak. Therefore, it is necessary to prevent the deformation of the honeycomb body due to the thermal expansion and contraction.

In general, the following means have been proposed as a method for preventing deformation of a honeycomb body due to heat. For example, in Japanese Patent Application Laid-Open No. Hei 2-265563, at least a portion of a metal honeycomb structure which is in contact with a case is described.
By increasing the wall thickness, the difference in the amount of expansion and contraction deformation between the honeycomb structure and the case is gradually reduced, and a supporting base material that is excellent in heat resistance strength and has improved thermal fatigue characteristics to prevent damage is disclosed. Have been. Japanese Patent Application Laid-Open No. Hei 3-296420 discloses that the high-temperature strength of a flat plate material of a honeycomb structure is increased by forming the central portion of the structure to be thicker than a corrugated sheet material. It is disclosed that even if a thermal expansion difference occurs due to a temperature difference between the case side / outside and the center part / inside, the flat plate does not buckle and cracks due to thermal fatigue can be prevented. However, in each of these methods, in order to prevent buckling deformation of the honeycomb body due to thermal stress, rigidity is increased by increasing the thickness of a plate (foil) constituting the honeycomb body, and durability is improved. However, it is not specified how much the thickness should be increased. If the thickness is too large, the area of the cell (the space defined by the corrugated plate and the flat plate) becomes small, causing a problem of pressure loss of the exhaust gas flow and a honeycomb. Increased heat capacity due to increased body weight,
As a result, the temperature raising performance is reduced, so that the purification performance is reduced and the cost is increased.

On the other hand, JP-A-4-48934 discloses that
FIG. 7 shows a honeycomb body in which the number of cells per unit area of the outer peripheral part is larger than that of the inner peripheral part by making both the interval between the layers of the honeycomb body and the magnitude of the wave smaller in the outer peripheral part and larger in the inner peripheral part. It is shown that the temperature of the outer peripheral portion is reduced by the heat radiation, and the thermal stress generated in the honeycomb is reduced by eliminating the temperature difference from the inner peripheral portion by utilizing the effect of increasing the catalytic reaction by increasing the number of cells. It is disclosed to prevent and improve durability. However, the amount of exhaust gas flowing into the converter is large in the inner peripheral portion of the honeycomb body, and the amount of gas flowing in the outer peripheral portion is small. It is impossible to achieve this by simply increasing the number. On the other hand, if the number of cells is excessively increased, the state becomes “clogged”, the “back pressure” increases, and the gas stops flowing.

[0009]

In the conventional catalyst carrier as described above, the rigidity of the honeycomb body is improved by increasing the plate thickness of the honeycomb body structure to prevent deformation, and to reduce the number of cells in the outer peripheral portion. The purpose of the present invention is to increase the temperature difference in the honeycomb body to a large extent, to eliminate the occurrence of thermal stress, and to prevent the honeycomb from being deformed. Instead of being fixed to the honeycomb body, the honeycomb body is loaded and supported on the casing via an elastic body (insulation mat).
As a result, the temperature of the honeycomb body is prevented from lowering due to heat radiation, the temperature difference in the honeycomb body is made uniform, the occurrence of thermal stress is prevented, and the compressive force to the honeycomb body due to the thermal expansion of the elastic body is reduced. An object of the present invention is to provide an automobile exhaust gas purifying apparatus that absorbs a honeycomb body by making the structure easily elastically deformed without increasing the rigidity of the body and prevents the honeycomb body from being deformed.

[0010]

According to the present invention, a flat foil made of a heat-resistant metal foil and a corrugated foil obtained by processing a flat foil into a corrugated shape are superposed and spirally wound. In an exhaust gas purifying apparatus, the formed honeycomb body is inserted into a casing via an elastic holding material having a thermal expansion property.
(1) The thickness of the flat foil and corrugated foil of one to several windings (layers) on the outer circumferential side around which the honeycomb body is wound is 30 μm or less, and the number of cells constituted by both foils is 50 to 300 cells /
and in ^2, the plate thickness of the flat foil and the corrugated foil are wound on the inside and 40 to 60 [mu] m, and the number of cells constituted by Ryohaku is characterized by a 400 cell / in ² or more. (2) The flat foil and corrugated foil around which the honeycomb body is wound have a thickness of 30 μm or less, and the number of cells formed by both foils is 50 to 300 cells / in ^2. It is an automobile exhaust gas purification device. The above
In (1) and (2), it is preferable that the corrugated foil wound around the honeycomb body is formed into an asymmetric trapezoidal corrugated shape that is easily elastically deformed.

[0011] The holding material used in the present invention is wound around a honeycomb body in advance and coated, and is then loaded into a casing, or the casing is divided and filled into a gap with the honeycomb body (the casing is then closed). The exhaust gas is prevented from flowing into the gap between the casing and the honeycomb body. This holding body is a heat insulating material, but has a thermal expansion property, and expands by heat transfer from the honeycomb body, so that the honeycomb body is compressed. In the present invention, the honeycomb body is partially flexible and has a large elastic deformation rate as described above, so that the compressive strain is absorbed and buffered by the elastic deformation of the honeycomb body to prevent the deformation of the honeycomb body. Even if the elastic body contracts during cooling, the supporting force (surface pressure) of the honeycomb body of the elastic body does not decrease, and the honeycomb body can be stably held over the entire temperature range.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 shows an example of the invention based on claim 1 of the present invention, wherein 1 is a casing made of heat-resistant steel and connected to an exhaust gas system, 2 is a honeycomb body inserted in a casing 1, and 1 The gap between the honeycomb body 2 and the honeycomb body 2 is filled with the holding material 3. In order to insert the honeycomb body into the casing, the outer periphery of the honeycomb body is coated with a mat-shaped holding material in advance, and the honeycomb body is inserted into a cylindrical casing material, and the front and rear portions thereof are connected to an exhaust gas system. Formed into a structure (not shown, molding of cone and connection flange) or split casing formed in such a structure, loaded holding material and honeycomb body, and fixed split casing by welding It can be carried out by such a method. As the holding material, a ceramic fiber containing “Hirushi”, for example, a heat-expandable mat such as an Intram (trade name: manufactured by 3M) mat is used.

The present invention is characterized by the structure of the honeycomb body 2. That is, the honeycomb body is formed by laminating a flat metal foil (hereinafter, referred to as a flat foil) 4 and a corrugated foil 5 obtained by processing the flat foil into a corrugated shape and spirally winding the same. This foil has heat resistance and excellent corrosion resistance, for example, 5% Al-
A 25% Cr—Fe-based steel having a thickness of about 50 μm is usually used. However, in the present invention, the steel is elastically absorbed by being compressed by the expansion of the holding material at the time of high-temperature heating and reduced in diameter. In addition, a spirally wound body, that is, a honeycomb body 2
One to several layers (layers) from the outermost periphery of the above-mentioned layer have a flexible structure having a smaller rigidity and a higher elastic deformation rate than the inner peripheral layer. Specifically, as shown in the partial cross-sectional view of FIG. 2, the flat foil 4 and the corrugated foil 5 of one to several windings (layers) on the outer peripheral side 7 around which the honeycomb body is wound have a thickness of 30 μm. The number of cells 6 constituted by both foils is set to be 50 to 300 cells / in ² as described below. Then, the plate thickness of the flat foil and corrugated foil wound on the inner side 8 is 40 to 60 μm.
m, and the number of cells constituted by both foils is preferably 400 cells / in ² or more. The inner configuration is substantially conventional.

The preferred range is limited as described above for the following reasons. The thickness of the foil and the number of cells at the center of the honeycomb body are determined based on the purification performance and back pressure (horsepower) required for the catalyst carrier. This is because 80% to 90% of the exhaust gas flows through the central honeycomb body (depending on the shape of the inlet cone).

That is, (a) When a honeycomb body having a foil thickness of 40 μm to 60 μm and a cell number of 400 cells / in ² or more is required, the elastic deformation rate of the honeycomb body becomes smaller than the original honeycomb diameter. 1.0% or less. (B) 3
When a honeycomb body having a foil thickness of 0 μm and a cell number of 50 to 300 cells / in ² is required, the elastic deformation rate of the honeycomb body becomes 3% or more with respect to the original honeycomb diameter. on the other hand,
The coefficient of thermal expansion of the elastic body depends on its material and operating temperature.
Generally speaking, considering the honeycomb diameter as a base, 3 to 6
Used in%.

This coefficient of thermal expansion becomes a compressive force for compressing the honeycomb body. In particular, when the honeycomb body is a metal honeycomb, the honeycomb body is inferior in rigidity to the elastic body, so that the honeycomb body is compressed in the radial direction. Deformation rate.

From the above, considering the deformation rate and the amount of buckling of the honeycomb body in the case of the above (a) or (b),
In the case of the thermal expansion coefficient of 6%, the plastic deformation occurs in the case (a) at a deformation amount (strain) of 1% or more and in the case of (b) case at 3% or more.

Therefore, when the honeycomb body is a metal honeycomb, the plastic deformation rate (if the amount of honeycomb buckling becomes 3% or more of the honeycomb diameter, cell collapse occurs, insufficient elastic body holding force occurs, and It shifts or slips in the direction.

Therefore, if the honeycomb structure according to the second aspect is used and the elastic deformation rate is increased, the amount of honeycomb buckling can be reduced, and cell crushing and displacement in the axial direction can be prevented. From the viewpoint of performance, when a honeycomb body having a foil thickness of 40 μm to 60 μm and a cell number of 400 cells / in ² or more is required,
As described in claim 1, the outer peripheral portion of the honeycomb which is easily affected by the thermal expansion deformation of the elastic body, preferably for 5 layers (rolls), has a large elastic deformation rate of 30 μm, and has 50 to 30 cells.
The same effect can be obtained by coating and holding at 0 cells / in ² .

In the present invention, more preferably, FIG. 2 and FIG.
As shown in the enlarged view of FIG. As a result, the flat foil 4 and the corrugated foil 5 come into linear contact with each other at the one apex 52 of the asymmetric trapezoid 51, and the area of the joint 9 can be reduced, so that the elasticity and the elasticity can be increased.

FIG. 4 shows another embodiment of the present invention (Claim 2). The flat foil 4 and the corrugated foil 5 around which the honeycomb body is wound have a total foil thickness of 30 μm or less (preferably 30 to 20 μm).
m), and the number of cells constituted by both foils is 50 to
By setting the cell density to 300 cells / in ² , the same effect as described above can be obtained by making the entire honeycomb body flexible. Moreover, the shape of the corrugated foil may be an asymmetric trapezoid, and the flexible structure can be further improved by the same as described above.

[0022]

【Example】

[Example 1] As shown in FIG.
A flat foil having a width of 113 μm and a corrugated foil in which the flat foil is formed into a sine-curve mountain shape are superposed and spirally wound, and the inside of a honeycomb body having a cell number of 400 cells / in ² and a diameter of 89 mm is formed. Then, a flat foil having a thickness of 30 μm and a width of 113 mm and a corrugated foil obtained by forming the flat plate into an asymmetric trapezoidal corrugated shape are laminated on the outer periphery of the inner layer portion. The outer peripheral portion was wound so as to be cells / in ² to produce a honeycomb body having a diameter of 99 mm and a length of 113 mm. This honeycomb body was inserted into a vacuum heating furnace and heated to 1250 ° C. to perform diffusion bonding. Next, thickness 1.5mm, outer diameter φ
A ferrite-based stainless steel casing having a length of 108 × 120 mm was prepared, and a 4 mm-thick heat-expansion mat was previously wound around the above-mentioned honeycomb body to cover the casing.
A metal carrier was made by insertion using a press-fitting method.

Example 2 A flat foil having a thickness of 30 μm and a width of 113 mm and a corrugated foil obtained by forming this flat foil into an asymmetric trapezoidal corrugated shape are spirally wound so that the number of cells becomes 200 cells / in ^2. To produce a honeycomb body having a diameter of φ99 and a length of 113 mm. This honeycomb body was inserted into a vacuum heating furnace and 12
Diffusion bonding was performed by heating to 50 ° C. Next, a heat-expandable mat having the same specifications as in Example 1 was wound around a honeycomb body in a casing having the same specifications as in Example 1, and inserted by a press-fitting method to produce a metal carrier.

COMPARATIVE EXAMPLE A flat foil having a thickness of 50 μm and a width of 113 mm and a corrugated foil obtained by forming the flat foil into a sine-curve-shaped mountain shape are spirally wound, and the number of cells is 400 cells / in ² . A honeycomb body was manufactured, and diffusion bonding was performed in the same manner as described above. Next, the same casing as that in Example 1 was integrated with the same casing by a press-fitting method using a heat-expandable mat to produce a metal carrier.

[0025] The above three metal carriers are treated with an exhaust gas at 800 ° C.
Table 1 shows the results of the evaluation of the samples subjected to the thermal endurance test.

[0026]

[Table 1]

[0027]

As described above, according to the present invention, a honeycomb body is loaded and supported on a casing via an elastic body without using an outer cylinder. An automobile exhaust gas purifying apparatus capable of absorbing the compression of the body by making the structure easily elastically deformable and preventing the honeycomb body from being deformed in a severe exhaust gas purifying atmosphere can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross section of an embodiment of the present invention.

FIG. 2 is a diagram showing a partial cross section of an embodiment of the present invention.

FIG. 3 is an enlarged partial cross-sectional view of an outer portion in the embodiment of the present invention.

FIG. 4 is a diagram showing a cross section of another embodiment of the present invention.

[Explanation of symbols]

 1: Casing 2: Honeycomb 3: Holding material 4: Flat foil 5: Corrugated foil 6: Cell 7: Outer side 8: Inside 9: Joint

Claims (2)

[Claims] 1. A honeycomb body formed by laminating a flat foil made of a heat-resistant metal foil and a corrugated foil obtained by processing the flat foil into a corrugated shape, and holding the honeycomb body in a resilient manner having a thermal expansion property. In an exhaust gas purifying apparatus which is inserted into a casing via a material, the thickness of a flat foil and a corrugated foil of one to several turns (layers) on the outer peripheral side around which a honeycomb body is wound is set to 30 μm or less. The number of cells constituted by foil is 50 to 300 cells /
automobile exhaust gas and in ^2, the plate thickness of the flat foil and the corrugated foil are wound on the inside and 40 to 60 [mu] m, and the number of cells constituted by Ryohaku is characterized in that at 400 cells / in ² or more Purification device. 2. A honeycomb body formed by laminating a flat foil made of a heat-resistant metal foil and a corrugated foil obtained by processing a flat foil into a corrugated shape, and holding the honeycomb body in a resilient manner having a thermal expansion property. In an exhaust gas purifying apparatus loaded in a casing via a material, the flat foil and the corrugated foil around which the honeycomb body is wound have a thickness of 30 μm or less, and the number of cells constituted by both foils is 50 to 300. An automobile exhaust gas purifying device characterized by having cells / in ² .