JPH04148016A - Metallic carrier excellent in durability for vehicle exhaust gas catalyst - Google Patents

Abstract

PURPOSE:To prevent a honeycomb body from being buckled and also from being dislocated from the outer cylinder by joining the plane foil of the honeycomb body with the waved foil of the body at one place in the axial direction against possible dislocation within the honeycomb body with respect to the outer cylinder, and thereby concurrently providing an outer layer reinforcing area. CONSTITUTION:In a metallic carrier for vehicle exhaust gas catalyst, a metallic honeycomb body 1 where a plane foil 9 and a waved foil 8 are piled up while being rolled in, is joined with a metallic outer cylinder 2 which encloses the side surface of the honeycomb body. In this case, one area is provided, wherein the plane foil 9 is joined with the waved foil 8 equivalent in length to 5% to 20%, the axial length of the metallic honeycomb body 1 at the given position of the metallic honeycomb body 1 in the axial direction. And an outer layer reinforcing area 4 joined in the axial direction is provided for an area within five layers from the outermost layer of the honeycomb body 1. Furthermore, the outer cylinder 2 is joined 5 with the metallic honeycomb 1 within the range of direction of the outer layer reinforcing area 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a metal carrier for supporting a catalyst for purifying automobile exhaust gas.

[Conventional technology]

Honeycomb metal carriers made of heat-resistant stainless steel are attracting attention as carriers for supporting catalysts for purifying automobile exhaust gas. It is important that these metal carriers not only have heat resistance and oxidation resistance that can withstand high-temperature exhaust gases, but also withstand thermal cycles of heating and cooling caused by exhaust gases and thermal stress and thermal fatigue due to temperature differences within the honeycomb body. .

When a metal carrier is heated and cooled, a large temperature difference occurs between the center of the carrier and its outer periphery, generating thermal stress. When the center of the honeycomb body is heated by the exhaust gas and the temperature of the center becomes higher than the temperature of the outer circumference, the center tends to expand more than the outer circumference due to thermal expansion. As it cools from the outer periphery during the cooling process, it stretches.

The foil at the center can be sufficiently shrunk to its original length, and the mesh 9 is plastically deformed in the axial direction. When such thermal cycles are repeated, the foil gradually stretches in the axial direction. Tokuho 1-54
As stated in Japanese Patent No. 090, there is a problem that the carrier expands especially in the longitudinal direction when the operating time increases at high temperatures.2 If there is a drift in the flow of exhaust gas,
In the case of the two rollers where the flow rate is high, the honeycomb body in particular is exposed to a high temperature that is 1 degree higher than the surrounding area. That is, the honeycomb body is exposed to high temperatures due to two factors: plastic elongation of the honeycomb body due to repeated thermal force and expansion of the honeycomb body due to high temperatures.

In the honeycomb part, the foil expands in the axial direction, and when the axial foil elongation phenomenon like this occurs,
Fig, la, lb, lc of Publication No. 466.

In a metal carrier with a structure in which both ends of a metal honeycomb body are joined for a certain length in the axial direction and fixed with a joint, as shown in Figure ld, there is a flat surface inside the boundary of the joined part of the honeycomb body. The foil and corrugated foil undergo search bending in the axial direction, leading to destruction of the honeycomb body. This is because the joints at both ends hold down the foil from freely extending in the axial direction.

Also, in Figure 1 of Utility Model Application Publication No. 62-194436,
An example has been disclosed in which the cross-sectional parts of the exhaust gas inlet end of the honeycomb core part are joined, and the outer cylinder is joined to the core part only at the joined cross-sectional part. This is done to prevent peeling of the bonded parts.

However, in this bonding structure, the bonding boundary between the core portion and the outer cylinder portion coincides with the bonding boundary within the core portion, forming a stress concentration area, and the failure of the foil begins at that location. As a result, the core is separated from the outer cylinder and displaced.

As a countermeasure against thermal stress and thermal fatigue caused by thermal cycles, only the ends of the foil are joined to the outer cylinder in the axial direction, as disclosed in Japanese Patent Application Laid-Open Nos. 62-273050 and 62-273051. In some cases, the flat foil and corrugated foil of the honeycomb body are not bonded together, or as disclosed in JP-A No. 62-83044, the flat foil is deformed at large cycles, and the corrugated foil is deformed at small wavelengths. There is a method of alleviating thermal stress by adding extra deformation to the cells formed at the junction point. In the former method, since the ends of the foil are joined only to the outer cylinder, the flat foil and corrugated foil of the honeycomb body may become displaced due to high-temperature and high-speed exhaust gas. Furthermore, in the latter method, it is difficult to process the corrugated foil, and at the same time, it is difficult to wind the foil and to stably join the contacts.

Therefore, it is easy to cause poor bonding of each cell, and the honeycomb body lacks structural stability. There is also a method of fixing the honeycomb body mechanically as described in Japanese Utility Model Application Publication No. 62-160728, but since it is separated from the outer cylinder, the honeycomb body vibrates inside the outer periphery and the supported catalyst falls off. and the purification ability decreases.

As mentioned above, conventional countermeasures against thermal stress and thermal fatigue due to thermal cycles are insufficient to prevent foil elongation that occurs in the axial direction, and buckling occurs within the honeycomb body, resulting in partial loss of the metal honeycomb body. or breakage occurs in the outermost layer on the metal honeycomb body side at the joint between the metal honeycomb body and the outer cylinder, resulting in a problem that the metal honeycomb body is separated from the outer cylinder and shifted.

[Problem to be solved by the invention]

The present invention deals with buckling inside a metal honeycomb body caused by the axial elongation phenomenon of the foil due to both the elongation of the metal foil due to thermal stress generated inside the metal honeycomb body and the elongation of the metal foil due to exposure to high temperature, and the buckling inside the metal honeycomb body. This is an attempt to solve the problem of displacement of the metal honeycomb body from the outer cylinder due to fracture occurring at the joint between the metal honeycomb body and the outer cylinder.

[Means to solve the problem]

The gist of the present invention is to join a flat foil and a corrugated foil to a predetermined length in the axial direction at only one location in the axial direction of a metal honeycomb body, and to connect the flat foil and the corrugated foil in the axial direction within five layers from the outermost layer to the inside. By joining the outer cylinder and the metal honeycomb body within a range that overlaps with the outer layer reinforcement area in the axial direction, the buckling phenomenon within the metal honeycomb body and the metal This prevents the phenomenon of displacement occurring at the joint between the honeycomb body and the outer cylinder.

[For production]

The metal foil stretches due to the thermal stress applied to the metal honeycomb body and is exposed to high temperatures, but when foils are joined at two or more locations in the axial direction, the foil between the joints is compressed in the axial direction due to the restraint caused by the joining. It is stressed and causes buckling. In order to prevent this, the honeycomb body may be joined at one arbitrary position in the axial direction to allow the elongation of the foil to escape toward the free end. The shorter the bonding length at that time, the smaller the thermal stress generated, but the strength of the bonded portion that can withstand external force decreases. Therefore, engine vibration,
A predetermined bond length is required to withstand the pressure of exhaust gas. Engine test from 100℃ to 850℃
As a result of examining the necessary bonding length by repeatedly subjecting the metal honeycomb to thermal cycles, it was found that it is sufficient to bond approximately 5% to 20% of the axial length of the metal honeycomb body. Bonding for longer than that will not have a great effect; on the other hand, if it is too long, thermal stress will increase within the bond itself, which may lead to breakage. From the above, in order to prevent buckling in the axial direction within the metal honeycomb body, the honeycomb body must be joined only at one location in the axial direction and must not be joined at two or more locations.

In addition, in order to prevent the outermost layer of the metal honeycomb body from breaking and shifting at the joint between the metal honeycomb body and the outer cylinder, a Provide axially bonded outer layer reinforced regions within five layers. The reason why the joint between the outer cylinder and the metal honeycomb body is easily destroyed is that the metal honeycomb body joined to the outer cylinder is made of foil with a thickness of approximately 50 mm. The outer cylinder and the metal honeycomb body are joined to a thickness of #l. In this case, the foil is so thin that it easily breaks and the honeycomb body is displaced from the outer cylinder. In order to prevent this, even if the outermost layer of the honeycomb body breaks, if there is a joint between the corrugated foil and the flat foil on the inner side, the honeycomb body will not be separated from the outer cylinder and will not shift. There isn't.

However, it is best to keep the number of layers joined from the outermost layer to the inside within five layers. Even if the number is larger than that, the effect of preventing the honeycomb body from shifting from the outer cylinder is greater than the advantage of obtaining the effect of preventing the honeycomb body from shifting from the outer cylinder. The tensile stress and axial shear stress will cause the outermost layer of corrugated foil to break in the axial direction along the length where it is joined to the outer cylinder, potentially causing the metal honeycomb body to shift from the outer cylinder. This is because it becomes stronger. For this reason, if the metal honeycomb body is joined to the outer cylinder so that it overlaps in the axial direction at the same location as the joint, the outermost layer of corrugated foil of the honeycomb body will break in the axial direction, and the honeycomb body will not fit into the outer cylinder. It deviates from the Moreover, the joint boundary in the axial direction of the joint end with the outer cylinder and the joint part of the honeycomb body coincides, causing stress concentration, which makes it even easier for fracture to proceed.

Therefore, it is desirable that the joint between the outer cylinder and the metal honeycomb body does not overlap with the joint between the honeycomb body and the honeycomb body.

When joining in an overlapping manner, make the axial joining length with the outer cylinder longer than the axial joining length of the honeycomb body, provide an outer layer reinforced region, and perform the joining within the axial length range of the outer layer reinforced region. Good. The reason why the outer cylinder is joined to the outer cylinder within the axial length range of the outer layer reinforced area is to avoid coincidence of the joint end with the outer cylinder and the joint boundary of the outer layer reinforced area.

The above prevents buckling inside the metal honeycomb body,
In order to prevent the honeycomb body from slipping from the outer cylinder, the flat foil and corrugated foil of the honeycomb body should be bonded in the axial direction of the metal honeycomb body at a length of 5% to 20% of the axial length of the honeycomb body. At any one point, and an axial joint within five layers from the outermost layer to the inner side, that is, an outer layer reinforced region is provided, and the outer cylinder and the honeycomb body are joined within the axial length of the outer layer reinforced region. This can be prevented by doing this.

In addition, the effect of joining the metal honeycomb body, the outer layer reinforced region, and the outer cylinder to the metal honeycomb body at the axial center of the metal honeycomb body is to prevent buckling of the honeycomb body and displacement from the outer cylinder. Since the metal carrier has a symmetrical joining structure with respect to both end faces, it is advantageous in that mistakes can be prevented when assembling and mounting parts of an automobile.

Furthermore, the effect of joining flat foil and corrugated foil in the axial direction from about 1 mm to 5 fins on the exhaust gas inlet end face or both end faces of the metal honeycomb body is to prevent the end face foil from being agitated and chipped by exhaust gas. It is.

Since this is to prevent the fanned foil from chipping and scattering, the joining length may be short. A method of joining only the inner circumferential side of the corrugated foil and the outer circumferential side of the flat foil as a pair is also effective in preventing the foil from scattering.

The gist of the present invention can be achieved by joining methods such as brazing, diffusion joining, resistance welding, laser welding, and electron beam welding. In particular, when using brazing metal, a binder is applied in advance to the parts to be brazed using something like a roller, and then flat foil and corrugated foil are wound to form a metal honeycomb body. By scattering the brazing material and adhering the brazing material to predetermined locations, the joint locations can be easily controlled and implementation is easy.

Furthermore, since the joint structure of the present invention is intended to prevent bending in the axial direction, it is not necessary to limit the cross section to a circle, and it is not necessary to limit the cross section to a race track having an elliptical shape or a parallel part and a circular arc part. It may also be a cross section of a mold.

〔Example〕

Next, embodiments of the present invention will be described using the drawings.

First, FIG. 1 is a perspective view of a metal carrier. FIG. 1 shows a metal honeycomb body, and 2 shows an outer cylinder. The drawings after FIG. 2 are schematic axial cross-sectional views of the metal carrier. The upper part of the paper represents the exhaust gas inlet side. The shaded area in the figure is the area where the flat foil and corrugated foil are joined. These Examples and Comparative Examples are all examples of joining using a brazing material. FIG. 2 is Embodiment 1 based on the present invention. Width 100IIlII11
A honeycomb body 1 made by overlapping and wrapping ferritic heat-resistant stainless steel flat foil and corrugated foil with a thickness of 50 jal, with an outer diameter of 80 jal,
It is housed in a stainless steel outer cylinder 2 with a thickness of 1.5 mm and a length of 100 m.

FIG. 3 shows the joining part of the honeycomb body 1, that is, the brazing area between the flat foil and the corrugated foil, and the joining length thereof is 15 mm. FIG. 4 shows an outer layer reinforced region in which five layers are joined from the outermost layer to the inside, and the length thereof is 60 am, including the joining length 15a of the honeycomb body 1. 5 shows a region where the honeycomb body 1 and the outer cylinder 2 are brazed, and the axial length thereof is 35a.

The above-mentioned metal carrier is heated to over 850°C and subjected to an exhaust gas heating and cooling cycle using an actual engine.
Repeat cooling until the temperature drops below ℃. ) As a result, no bending phenomenon occurred inside the honeycomb body at the end of 1000 cycles. At the stress concentration area at the joint end of the outer cylinder 2 and the honeycomb body l, cracks had progressed to the outermost circumferential flat foil and the corrugated foil inside thereof, but the cracks had stopped progressing in the outer layer reinforced region 4.

FIG. 3 shows a second embodiment. In Example 2, the outer layer reinforced region 4 is bonded with the same number of layers as in Example 1, but is separated from the bonded portion 3 of the honeycomb body 1, and the bonded length is 45 mm. As a result of carrying out the engine test under the same conditions in Example 2, no bending occurred inside the honeycomb body. In Example 2, the honeycomb body joint 3 and the outer layer reinforced region 4 have two locations in the axial direction, that is, the outermost layer 5 in two cross sections.
The layers are joined. However, no bending occurred. The reason for this is that because only the outermost five layers are bonded in two places, no large compressive stress is applied, and because it is near the outer layer of the metal carrier, the temperature does not rise above the center and the foil We believe that this is because the hot strength did not decrease.

Although destruction had occurred at the joint end with the outer cylinder 2, the progress of the destruction had stopped in the outer layer reinforced region 4.

FIG. 7 shows Comparative Example 1. 15m each on both ends of the honeycomb
+e are joined. There is no outer layer reinforced region, the length of the joint with the outer cylinder 2 is 80u, and the joints at both ends 3. a and 5fi in the axial direction, respectively.

In Comparative Example 1, as a result of the same engine test, bending occurred on the inside side of the end joining boundary, that is, 15 mm from the end face, and the flat foil and the corrugated foil were broken. At the same time, the part joined to the outer cylinder 2 was fractured, and as a result of the fracture caused by bending, the outer cylinder 2 and the honeycomb body 1 were separated from each other at the end of 600 cycles, and the honeycomb body 1 was separated from the outer cylinder 2. was. Comparative example 2 in Fig. 8 has honeycomb body 1 joined by 15 mm at one location in the axial direction, and the outer cylinder 2 and honeycomb body 1 are joined by 15 m at the same location where they were joined to the honeycomb body. . There are no outer reinforced areas. The results of the engine test for Comparative Example 2 showed that the honeycomb body was displaced from the outer cylinder at the 900th cycle. At the fracture point, the crack progresses from the joint end of the outer cylinder and honeycomb body, and the fracture from the exhaust gas inlet side and the fracture from the exhaust gas outlet side break the corrugated foil of the outermost layer of the joint in the axial direction, causing displacement. Ta.

In Comparative Example 3 in FIG. 9, the honeycomb body 1 is joined by 15 points at one point in the axial direction, and the connection with the outer cylinder 2 is made such that it does not overlap with the honeycomb body joint 3 in the axial direction. . but,
There are no outer reinforced areas. In Comparative Example 3, a deviation occurred at the 150th cycle of the engine test. In Comparative Example 3, since there is no outer reinforced region, the outer cylinder 2 is connected only to a flat foil having a thickness of 50 m, and therefore easily breaks due to stress concentration at the joint with the outer cylinder 2. Even if the outermost layer is made of corrugated foil, it will easily shift if just one layer of corrugated foil breaks.

In Comparative Example 4 in FIG. 10, the outer layer reinforced region 4 is made up of 10 layers, and the other bonding structures are those of Example 1.
is the same as When Comparative Example 4 was subjected to an engine test, it shifted at 900 cycles. The cause of the shift was that a crack propagated through the outermost layer of corrugated foil in the axial direction from the joint end of the outer cylinder 2, causing the same fracture as in Comparative Example 2 and causing it to shift from the outer cylinder 2.

FIG. 4 shows Example 3. All joints are brought to the center of the honeycomb body 1. As a result, the carrier becomes symmetrical with respect to the exhaust gas inlet and outlet sides, and when the carrier is attached to the engine, it will not be attached in the wrong direction, improving reliability and production efficiency. In Example 3, the bonding length of the honeycomb body 1 is 15 mm, and the outer layer reinforced region 4 consists of an outermost layer flat foil, an inner corrugated foil, and two layers from the outermost layer.
Even the flat foil layers are joined. Its axial joining length is 6
0 wholesale. The joining length with the outer cylinder 2 was 37.5 mm, and the joining end with the outer cylinder 2 was positioned between the joining boundary of the honeycomb body 1 and the joining boundary of the outer layer reinforced region 4. This is to disperse stress concentration areas as much as possible. engine·
As a result of the test, no bending occurred within the honeycomb body even after 1000 cycles, and the fracture at the joint end of the outer cylinder stopped at the reinforced outer periphery region.

FIG. 5 shows Example 4. The joining structure of Example 4 was the same as that of Example 3, except that only the surface layer 6 of the end face of the honeycomb was joined by approximately one anus. For this joining, in addition to brazing, it is also possible to perform joining by irradiating the end faces with a laser or electron beam like a shower.

This is to prevent the foil from scattering due to exhaust gas.

Engine tests confirmed that with this level of bonding, no bending occurred within the honeycomb body. Figure 6 shows Example 5
As shown in FIG. 11, the joint 7°7 at the end of this embodiment is a 5U+ joint 10 in the axial direction only between the inner circumferential side of the corrugated foil 8 and the outer circumferential side of the flat foil 9. be. In such a joint 10, since the flat foil 8 and the corrugated foil 9 are only joined as a pair, the ends are not integrated in the radial direction and the rigidity of the end joint is small, resulting in engine test results. , bending did not occur, and furthermore, it was possible to prevent the foil from scattering on the end face.

〔Effect of the invention〕

As explained above, the present invention solves the bending inside the honeycomb body and the displacement of the honeycomb body from the outer cylinder by joining the flat foil and corrugated foil of the honeycomb body at one point in the axial direction and by strengthening the outer layer. By providing the area, bending and displacement could be prevented. Furthermore, by bonding the surface layer portions of the end faces, there is an effect of preventing the foil from scattering on the end faces. As a result, there was no drop in purification efficiency and the possibility of engine trouble was eliminated.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a metal carrier, and FIGS. 2, 3, 4, 5 and 6 show embodiments according to the invention,
7, 8, 9 and 10 show comparative examples,
FIG. 11 is a partially enlarged plan view of the end joint portion of the honeycomb body shown in FIG. 6. FIG. 1... Metal honeycomb body, 2... Outer cylinder, 3...
Honeycomb body joint, 4... Outer layer reinforced region, 5...
Joint between the outer cylinder and the honeycomb body, 6... Joint between the surface layer of the honeycomb body, 7... Joint between the inner periphery of the corrugated foil and the outer periphery of the flat foil at the end of the honeycomb body, 8... The corrugated foil , 9... Flat foil, 10.
・Joining area between the inner periphery of the corrugated foil and the outer periphery of the flat foil.

Claims (1)

[Scope of Claims] 1. In a metal carrier for an automobile exhaust gas catalyst, which is formed by joining a metal honeycomb body formed by overlapping and rolling together a flat foil and a corrugated foil and a metal outer cylinder surrounding the side surface of the metal honeycomb body, the axial direction of the metal honeycomb body is At any position, 5% to 20% of the axial length of the metal honeycomb body
It has one area where the flat foil and the corrugated foil are joined in the axial direction with a length of 5% from the outermost layer of the honeycomb body to the inside.
A metal carrier for an automobile exhaust gas catalyst, characterized in that the outer layer reinforced region is joined in the axial direction within the layers, and further, an outer cylinder and a metal honeycomb body are joined within the axial direction range of the outer layer reinforced region. . 2. The metal carrier for an automobile exhaust gas catalyst according to claim 1, wherein the bonding structure has symmetry with respect to both end faces of the metal carrier. 3. The metal carrier for an automobile exhaust gas catalyst according to claim 1 or 2, which is formed by joining a flat foil and a corrugated foil on the surface layer of the end face of the metal honeycomb body only on the exhaust gas inlet side or both ends on the exhaust gas inlet and outlet sides.