JP2512622B2 - Metal carrier for automobile exhaust gas catalyst with good durability - Google Patents

Description

The present invention relates to a metal carrier for supporting a catalyst for purifying automobile exhaust gas.

[Conventional technology]

As a carrier for supporting a catalyst for purifying exhaust gas from automobiles, a metal carrier of a honeycomb body made of heat-resistant stainless steel has been attracting attention. It is important that these metal carriers not only have heat resistance and oxidation resistance to withstand high-temperature exhaust gas, but also withstand thermal cycles of heating and cooling by exhaust gas and thermal stress and thermal fatigue due to temperature difference in the honeycomb body.

When the metal carrier is heated and cooled, a large temperature difference occurs between the center of the carrier and its outer peripheral side, and thermal stress is generated. When the central portion of the honeycomb body is heated by the exhaust gas and the temperature of the central portion becomes higher than the outer peripheral temperature, thermal expansion causes the central portion to extend beyond the outer peripheral portion. When the foil is cooled from the outer peripheral portion during the cooling process, the fully expanded central foil cannot be fully shrunk to its original length, and the foil is plastically deformed in the axial direction. When such a heat cycle is repeated, the foil gradually extends in the axial direction. Further, as described in Japanese Patent Publication No. 1-54090,
The carrier has the problem that at high temperatures it expands, especially in the longitudinal direction, with increasing operating time. When the flow of exhaust gas has a drift, the temperature of the honeycomb body becomes higher than that of its surroundings and exposed to a high temperature especially in a place where the flow rate is large. That is, the axial expansion phenomenon of the foil occurs in the honeycomb portion exposed to the high temperature due to the two factors of the plastic elongation of the honeycomb body due to the repeated thermal stress and the expansion of the honeycomb body due to the high temperature.
When such axial foil and phenomenon occur, the Japanese Patent Publication No. 63-
In a metal carrier having a structure in which both ends of a metal honeycomb body as shown in FIGS. 1a, 1b, 1c, 1d, etc. of 44466 publication are axially bonded at a certain length and the both ends are fixed by bonding. , The flat foil and the corrugated foil are buckled in the axial direction inside the boundary of the bonded portion of the honeycomb body, and the honeycomb body is broken. This is because the joint portions at both ends suppress the foil from freely extending in the axial direction. Also, in FIG. 1 of Japanese Utility Model Laid-Open No. 62-194436, the cross section of the exhaust gas inlet side end of the honeycomb core part is joined, and the outer cylinder is joined to the core part only at the joined cross section. Although the example to do is disclosed,
This example is performed in order to prevent peeling of the joint portion between the core portion and the outer cylinder. However, in this joint structure, the joint boundary between the core portion and the outer cylinder portion coincides with the joint boundary inside the core portion to form a stress concentration portion, and the foil starts to break from that portion. As a result, the core portion is separated from the outer cylinder and is displaced.

As measures against thermal stress and thermal fatigue due to thermal cycles, only the end portions of the foil as disclosed in JP-A-62-273050 and JP-A-62-273051 are joined to the outer cylinder in the axial direction. However, the flat foil and corrugated foil of the honeycomb body are not joined,
As disclosed in Japanese Patent Publication No. 83044, the flat foil is also deformed with a large period, and a wave of a small wavelength is added to the corrugated foil to give an extra deformation allowance to the cell formed at the junction point to heat the foil. There is a method of relieving stress. In the former of these methods, since the edge of the foil is joined only to the outer cylinder,
The flat foil and the corrugated foil of the honeycomb body may be displaced by the high-speed exhaust gas. Further, in the latter method, it is difficult to corrugate the foil, and at the same time, it is difficult to wind the foil and it is also difficult to stably join the contacts. Therefore, it is easy to cause the bonding failure of each cell, and the structural stability of the honeycomb body is lacking. There is also a method of mechanically fixing the honeycomb body as described in Japanese Utility Model Laid-Open No. 62-160728, but since the honeycomb body is separated from the outer cylinder, the honeycomb body vibrates inside the outer cylinder and the supported catalyst is It falls off and the purification capacity decreases.

As described above, the conventional measures against thermal stress and thermal fatigue due to thermal cycles are not sufficient to prevent the foil elongation that occurs in the axial direction, and buckling occurs in the honeycomb body, resulting in partial loss of the metal honeycomb body. Or the outermost layer portion on the metal honeycomb body side is broken at the joint between the metal honeycomb body and the outer cylinder, and the metal honeycomb body is separated from the outer cylinder and is displaced.

[Problems to be Solved by the Invention]

The present invention is a buckling in a metal honeycomb body caused by an axial elongation phenomenon of the foil due to both elongation of the metal foil due to thermal stress generated in the metal honeycomb body and elongation of the metal foil due to exposure to high temperature, and a metal honeycomb body. The present invention aims to solve the deviation of the metal honeycomb body from the outer cylinder due to the breakage occurring at the joint between the outer cylinder and the outer cylinder.

[Means for solving the problem]

The gist of the present invention is that the flat foil and the corrugated foil are bonded to each other in a predetermined length in the axial direction at only one position in the axial direction of the metal honeycomb body, and the axial direction is within 5 layers from the outermost layer to the inner side. Has a region to be joined (hereinafter referred to as an outer layer reinforced region),
By preventing the buckling phenomenon in the metal honeycomb body and the displacement phenomenon occurring at the joint portion between the metal honeycomb body and the outer cylinder by joining the outer cylinder and the metal honeycomb body within a range overlapping with the outer layer reinforced region in the axial direction. Is.

[Work]

While the metal foil expands when exposed to the thermal stress and high temperature applied to the metal honeycomb body, when two or more foils are bonded in the axial direction, the foil is compressed in the axial direction while being bonded due to the binding constraint. It is stressed and causes buckling. In order to prevent this, the bonded portion of the honeycomb body may be set at one arbitrary position in the axial direction and the elongation of the foil may be released toward the free end. The shorter the joint length at that time, the smaller the thermal stress generated, but the strength of the joint portion that can withstand the external force decreases. Therefore, a predetermined joint length is required to withstand the vibration of the engine, the pressure of exhaust gas, and the like. 100 ° C to 850 ° C according to engine test
As a result of examining the required joining length by repeating the thermal cycle of 5% to 5% of the axial length of the metal honeycomb body,
It has been found that it is sufficient to join about%. Bonding for a longer time has no great effect, and conversely, if it is too long, thermal stress in the bonded part itself becomes large, which may lead to destruction. From the above, in order to prevent axial buckling in the metal honeycomb body, the joining of the honeycomb bodies should be limited to only one location in the axial direction, and should not be joined at two or more locations.

In addition, in order to prevent the occurrence of displacement at the outermost layer portion of the metal honeycomb body at the joint portion between the metal honeycomb body and the outer cylinder, a portion from the outermost layer portion of the honeycomb body to the inside is joined to the portion joined to the outer cylinder. An outer layer reinforced region that is joined within 5 layers in the axial direction is provided. The reason why the joint between the outer cylinder and the metal honeycomb body is easily destroyed is that the metal honeycomb body bonded to the outer cylinder is 50 μm.
The outer cylinder and the metal honeycomb body are bonded to each other with a thickness of 50 μm at the bonding portion. In that case, the foil is so thin that it easily breaks and the honeycomb body shifts from the outer cylinder. In order to prevent this, even if the outermost layer of the honeycomb body breaks, there is a concern that the honeycomb body will not be separated from the outer cylinder if it is provided with a joint part between the corrugated foil and the flat foil inside it. There is no. However, it is preferable to keep the number of layers joining from the outermost layer to the inner side within 5 layers. If the number of layers to be joined is increased, the radial direction between the joining part of the honeycomb body and the joining part of the outer cylinder becomes larger than the merit of obtaining the effect of preventing the honeycomb body from being displaced from the outer cylinder even if the number is larger than that. There is a possibility that the tensile stress and the shear stress in the axial direction will act and the outermost corrugated foil will break in the axial direction for the length of the joint with the outer cylinder, and the metal honeycomb body will shift from the outer cylinder. Is getting stronger. For this reason, if the outer cylinder is bonded to the outer portion of the honeycomb body at the same position as the joint portion of the metal honeycomb body so as to overlap in the axial direction, the corrugated foil of the outermost layer of the honeycomb body is broken in the axial direction, and the honeycomb body becomes the outer cylinder. It will fall off. In addition, the joint end with the outer cylinder and the joint boundary in the axial direction of the joint portion of the honeycomb body coincide with each other to cause stress concentration, which further facilitates the fracture. Therefore, it is desirable that the joining portion between the outer cylinder and the metal honeycomb body does not overlap with the joining portion of the honeycomb body. In the case of joining in an overlapping manner, the axial joining length with the outer cylinder is made longer than the axial joining length of the honeycomb body, and the outer layer reinforced region is provided so that it is performed within the axial length range of the outer layer reinforced region. Is good. The reason why the outer tube is joined to the outer tube within the axial length range of the outer layer is to avoid coincidence between the joining end of the outer tube and the outer layer strengthened area.

From the above, in order to prevent buckling in the metal honeycomb body and prevent the honeycomb body from being displaced from the outer cylinder,
The flat foil and the corrugated foil of the honeycomb body are bonded to each other at an arbitrary position in the axial direction of the metal honeycomb body with a length of 5% to 20% of the axial length of the honeycomb body, and 5 from the outermost layer to the inside. This can be prevented by providing an axial joining portion within the layers, that is, an outer layer reinforced region and joining the outer cylinder and the honeycomb body within the axial length range of the outer layer reinforced region.

Further, the effect of performing the joining portion of the metal honeycomb body, the outer layer strengthening region, and the joining of the outer cylinder and the metal honeycomb body at the axial center portion 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 joint structure symmetrical with respect to both end faces, there is an advantage that mistakes can be prevented in assembling and mounting parts of the automobile.

Furthermore, the effect of joining the flat foil and the corrugated foil in the axial direction on the surface layer of the exhaust gas inlet side end surface or both end surfaces of the metal honeycomb body of about 1 mm to 5 mm is to prevent the end surface foil from being agitated and broken by the exhaust gas. is there. The joint length may be short because it is for preventing the fanned foil from chipping and scattering. A method of joining only the inner peripheral side of the corrugated foil and the outer peripheral side of the flat foil in pairs is also effective in preventing the foil from scattering.

Joining that can embody the gist of the present invention can be achieved by a joining method such as brazing, diffusion joining, resistance welding, laser welding, or electron beam welding. Especially with brazing, a binder for adhering the brazing material is applied in advance to the part to be brazed with a roller-like material, then the flat foil and the corrugated foil are wound to form a metal honeycomb body, and then the brazing material is applied. By spreading the material and adhering the brazing material at a predetermined position, the bonding position can be easily controlled and the materialization is easy. Further, the joining structure of the present invention is not limited to the circular cross section because it is for preventing buckling in the axial direction, and the race track having an elliptical shape or a parallel portion and an arc portion. It may be the cross section of the mold.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings. First,
FIG. 1 is a perspective view of a metal carrier. FIG. 1 shows a metal honeycomb body 2 and an outer cylinder 2. The drawings from FIG. 2 onward are schematic views of the axial cross section of the metal carrier. The upper part of the paper shows the exhaust gas inlet side. The shaded area in the figure is the area where the flat foil and the corrugated foil are joined together. These examples and comparative examples are all examples of joining using brazing. FIG. 2 is a first embodiment according to the present invention. Place a honeycomb body 1 consisting of a flat foil and corrugated foil of ferritic heat-resistant stainless steel with a width of 100 mm and a thickness of 50 μm wound on a stainless steel outer cylinder 2 with an outer diameter of 80 mm, a thickness of 1.5 mm, and a length of 100 mm. is there. FIG. 3 shows a joint portion of the honeycomb body 1, that is, a brazed region of the flat foil and the corrugated foil, and the joint length thereof is 15 mm. FIG. 4 shows the outer layer reinforced region in which up to 5 layers are joined from the outermost layer to the inner side, and the length thereof is 60 including the joining length of the honeycomb body 1 of 60 mm.
mm. In FIG. 5, the region where the honeycomb body 1 and the outer cylinder 2 are brazed has an axial length of 35 mm. As a result of subjecting the above metal carrier to an exhaust gas heating / cooling cycle (repeating heating up to 850 ° C or higher and cooling down to 100 ° C or lower) by an actual engine, inside the honeycomb body at the end of 100 cycles And the buckling phenomenon did not occur. In the stress concentration portion at the joint end of the outer tube 2 and the honeycomb body 1, cracks were propagated to the outermost flat foil and the corrugated foil inside thereof,
In the outer layer strengthened region 4, the progress of the crack had stopped. Third
The figure shows the second embodiment. In Example 2, the outer layer reinforced region 4 was joined by the same number of layers as in Example 1, but was separated from the joining portion 3 of the honeycomb body 1, and the joining length was 45.
mm. In Example 2, as a result of performing the engine test under the same conditions, no buckling occurred inside the honeycomb body. In Example 2, the honeycomb body joint portion 3 and the outer layer reinforced region 4 were joined at two locations in the axial direction, that is, the outermost layer of 5 layers was joined in two transverse sections. However, no buckling occurred. The reason for this is that since only the outermost layer of 5 layers is bonded at two locations, no large compressive stress was applied and because it was near the outer layer of the metal carrier, the temperature did not rise above the center and the foil It is believed that this is because the hot strength did not decrease. Although the breakage occurred at the joint end with the outer cylinder 2, the breakage stopped at the outer layer reinforced region 4.

FIG. 7 shows Comparative Example 1. 15mm each on both ends of the honeycomb
Are joined together. There is no outer layer reinforced region, the joint length with the outer cylinder 2 is 80 mm, and the joint portions 3 and 3 at both ends are overlapped by 5 mm in the axial direction. In Comparative Example 1, the same engine test results showed that the inner side of the end joint boundary, that is, 15 mm from the end face.
At that point, buckling occurred and the flat foil and the corrugated foil were broken. At the same time, the part joined to the outer cylinder 2 is broken,
The outer cylinder 2 and the honeycomb body 1 were separated and the honeycomb body 1 was disengaged from the outer cylinder 2 at the end of 600 cycles due to the fracture caused by buckling. In Comparative Example 2 shown in FIG. 8, the honeycomb body 1 is bonded at 15 mm at one axial position, and the outer tube 2 and the honeycomb body 1 are bonded at the same position as at 15 mm for bonding. . There is no outer layer reinforced area. As a result of the engine test of Comparative Example 2, the honeycomb body was displaced from the outer cylinder at the time of 900 cycles. At the rupture point, a crack progresses from the joint end of the outer cylinder and the honeycomb body, and the fracture from the exhaust gas inlet side and the fracture from the exhaust gas outlet side rupture the fractured foil of the outermost layer of the joint portion, resulting in misalignment. It was Comparative example 3 in FIG.
The honeycomb body 1 is bonded by 15 mm at one position in the axial direction so that the bonding with the outer cylinder 2 does not overlap with the honeycomb body bonding portion 3 in the axial direction. However, there is no outer layer reinforced area. In Comparative Example 3, the deviation occurred at the time of 150 cycles of the engine test. In Comparative Example 3, since the outer layer reinforced region does not exist, the outer cylinder 2 is only connected to the flat foil having a thickness of 50 μm, so that the joint portion with the outer cylinder 2 is easily broken due to stress concentration. Even if the outermost layer is a corrugated foil, the corrugated foil is easily displaced by only one layer being broken. In Comparative Example 4 of FIG. 10, the outer layer reinforced region 4 has 10 layers, and other junction structures are the same as those in Example 1. When the engine test of the comparative example 4 was carried out, it shifted | deviated at the time of 900 cycles. The cause of the shift was that a crack progressed axially in the outermost corrugated foil from the joint end of the outer cylinder 2 and was displaced from the outer cylinder 2 by the same breakage as in Comparative Example 2.

FIG. 4 shows the third embodiment. All the joints are brought to the central part of the honeycomb body 1. As a result, the carrier becomes symmetrical with respect to the inlet side and the outlet side of the exhaust gas, and when the carrier is mounted on the engine, the carrier is not mounted in the wrong direction, and reliability and production efficiency are improved. In Example 3, the bonding length of the honeycomb body 1 was 15 mm, and the outer layer reinforced region 4 was bonded to the outermost flat foil, the inner corrugated foil, and the outermost layer to the second flat foil. Its axial joint length is 60 mm. The joint length with the outer cylinder 2 was 37.5 mm, and the joint end with the outer cylinder 2 was positioned midway between the joint boundary of the honeycomb body 1 and the joint boundary of the outer layer reinforced region 4. This is to disperse the stress concentration parts as much as possible. Engine test results
Even after 1000 cycles, buckling did not occur in the honeycomb body, and the fracture at the joint end of the outer cylinder stopped at the outer peripheral strengthening region. FIG. 5 shows Example 4. The bonding structure of Example 4 is exactly the same as that of Example 3, except that only the surface layer 6 of the honeycomb end face is reduced.
It is a 1mm joint. For this bonding, not only brazing but also laser or electron beam irradiating the end face like a shower can be used. This is to prevent the foil from scattering due to the exhaust gas. It was confirmed by engine tests that buckling did not occur in the honeycomb body with this degree of joining. FIG. 6 shows the fifth embodiment, and the joint portions 7, 7 at the ends of the embodiment are the inner peripheral side of the corrugated foil 8 and the flat foil 9 as shown in FIG.
5 mm joining 10 was made in the axial direction only on the outer peripheral side. 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 joints is reduced, and the engine test results are shown. No buckling occurred, and foil scattering on the end face was prevented.

〔The invention's effect〕

As described above, according to the present invention, the flat foil and the corrugated foil of the honeycomb body are bonded at one axial position and the outer layer reinforced region is formed against the buckling in the honeycomb body and the displacement of the honeycomb body from the outer cylinder. By providing it, it was possible to prevent buckling and displacement. Further, by joining the surface layer portions of the end faces, there is also an effect of preventing foil scattering on the end faces. As a result, there was no reduction in purification efficiency and the possibility of engine trouble was eliminated.

[Brief description 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 present invention,
Figures 7, 8, 9, and 10 show comparative examples.
FIG. 11 is a partially enlarged plan view of the joined portion of the end portions of the honeycomb body of FIG. DESCRIPTION OF SYMBOLS 1 ... Metal honeycomb body, 2 ... Outer cylinder, 3 ... Honeycomb body joining portion, 4 ... Outer layer reinforced region, 5 ... Joining portion between outer cylinder and honeycomb body, 6 ... Honeycomb body surface layer joining portion , 7 ...... Joining part of corrugated foil inner peripheral part and flat foil outer peripheral part at the end of honeycomb body, 8 …… corrugated foil, 9 …… flat foil, 10 …… bonding corrugated foil inner peripheral part and flat foil outer peripheral part Department.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shigeru Ogawa Shigeru Ogawa 1-1-1 Edamitsu, Hachimanto-ku, Kitakyushu, Fukuoka Prefecture Inside the 3rd Technical Research Laboratory, Nippon Steel Corporation (72) Masao Yatsushiro Tokai, Aichi Prefecture Tokai City 5-3 Machi Nippon Steel Co., Ltd. Nagoya Works (72) Inventor Toshihiro Takada 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Hiroshi Hirayama 1 Toyota Town, Toyota City, Aichi Prefecture Address Toyota Motor Co., Ltd. (56) Reference JP-A-2-273549 (JP, A)

Claims (3)

(57) [Claims] 1. A metal carrier for an automobile exhaust gas catalyst comprising a metal honeycomb body obtained by stacking and winding flat foil and corrugated foil and a metal outer cylinder surrounding the side surface of the metal honeycomb body, and at an arbitrary position in the axial direction of the metal honeycomb body. And the axial length of the metal honeycomb body is 5
% To 20% in length, and one area where the flat foil and the corrugated foil are bonded in the axial direction, and the outer layer reinforced area is bonded in the axial direction within 5 layers from the outermost layer to the inside of the honeycomb body. And a metal honeycomb body bonded to the outer cylinder in the axial range of the outer layer reinforced region. 2. The metal carrier for an automobile exhaust gas catalyst according to claim 1, wherein the joint 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, wherein only the end face of the exhaust gas inlet side of the metal honeycomb body or the flat foil and the corrugated foil of the surface layer of the end face at both ends of the exhaust gas inlet and outlet sides are joined.