JP3271716B2 - Metal carrier for exhaust gas purification catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal carrier used for an exhaust gas purifying catalyst of an internal combustion engine, and more particularly, to a metal carrier having a honeycomb structure, an intermediate cylinder and an outer cylinder.

[0002]

2. Description of the Related Art As a metal carrier for an exhaust gas purifying catalyst, a carrier composed of a honeycomb body in which a flat plate and a corrugated sheet are stacked and wound into a roll, and an outer cylinder for accommodating the honeycomb body are often used. ing. In this metal carrier, the flat plate and the corrugated plate of the honeycomb body, and the outer cylinder and the honeycomb body are integrally joined by brazing or diffusion joining.

However, in the case of a metal carrier, contact with a high-temperature exhaust gas, heat generation due to a catalytic reaction, release of heat from the outer cylinder to the outside, difference in heat capacity between the honeycomb body and the outer cylinder, etc.
A temperature distribution was generated, and as a result, a thermal stress was generated in the honeycomb body, and a crack was sometimes generated in the honeycomb body. Japanese Patent Application Laid-Open No. 3-157139 discloses a metal carrier having a configuration in which an intermediate cylinder having a bent portion at least at one end is interposed between a honeycomb body and an outer cylinder. According to this metal carrier, the thermal stress generated by the radial expansion and contraction of the honeycomb body and the outer cylinder is absorbed by the deformation of the bending portion of the intermediate cylinder. In addition, since only one end of the honeycomb body is joined to the intermediate tube, the other end is a free end and can be expanded in the axial direction.
The movement of shrinkage is not regulated and there is almost no generation of thermal stress.
Therefore, generation of cracks in the honeycomb body is prevented. It is also disclosed that it is preferable that the coefficient of thermal expansion of the intermediate cylinder be approximately midway between the honeycomb body and the outer cylinder.

[0004]

The exhaust gas flowing into the metal carrier is turbulent and pulsates. For this reason, on the upstream end surface of the honeycomb body, there is a possibility that deformation or breakage of the flat plate and the corrugated plate due to the stress from the exhaust gas may occur. In order to prevent this, it is preferable that the flat plate and the corrugated plate are joined at least in the vicinity of the upstream end face of the honeycomb body to increase the strength. At the center of the honeycomb body, it is desirable that the flat plate and the corrugated plate are not joined from the viewpoint of thermal stress relaxation.

However, in such a metal carrier, when heat is applied due to contact with exhaust gas or the like, the amount of expansion of the honeycomb body in the radial direction is larger at the joined portion where the flat plate and the corrugated plate are joined than at the unjoined portion. It is known to grow. This is because the honeycomb body can be deformed in the circumferential direction at the unjoined portion, and the directions of expansion are dispersed. Therefore, in the metal carrier having the intermediate cylinder, the honeycomb body expands particularly largely in the radial direction near the upstream end face which is the joining portion, and the advantage as the free end in contact with the intermediate cylinder is eliminated, Will receive stress from the intermediate cylinder,
When repeated thermal stress is applied, cracks and the like may occur.

The present invention has been made in view of such circumstances, and an object of the present invention is to further prevent a thermal stress from being applied to a honeycomb body in a metal carrier having an intermediate tube.

[0007]

A metal carrier for an exhaust gas purifying catalyst according to the present invention, which solves the above problems, accommodates a honeycomb body in which a flat plate and a corrugated plate are stacked and wound in a roll shape, and a honeycomb body. An outer cylinder, a metal carrier for an exhaust gas purifying catalyst comprising an intermediate cylinder interposed between the honeycomb body and the outer cylinder, wherein the honeycomb body has a flat plate at least near an upstream end face located on the upstream side of the exhaust gas. The upstream end face near the upstream end of the exhaust gas is joined to the outer cylinder and the downstream end is joined to the honeycomb body, and the intermediate cylinder has an upstream end face near junction where the corrugated plate is joined, The length of the intermediate cylinder in the axial direction is shorter than the length of the honeycomb body in the axial direction, and the joint with the outer cylinder at the upstream end of the intermediate cylinder is located downstream of the joint near the upstream end face of the honeycomb body. It is characterized by having.

The honeycomb body is formed by winding a flat plate and a corrugated plate in a roll shape in a state of being overlapped. The corrugated plate is usually formed by bending a flat plate into a corrugated shape, and is made of the same material as the normal plate and has substantially the same plate thickness. The flat plate and the corrugated plate are formed of, for example, an Al-Cr-Fe alloy, stainless steel, or the like, as in the related art. Since it is preferable to secure as many honeycomb passage areas as possible in a limited volume, a relatively thin plate having a thickness of, for example, 0.05 mm is used. The honeycomb body is formed, for example, in a state where a brazing material is applied to the top of a corrugated sheet and wound on a flat plate in a roll shape, and then brazed by heating to be integrally joined. Further, they can be integrated by diffusion bonding.

As the outer cylinder, for example, a conventional one such as stainless steel can be used, and its thickness is usually about 1 to 2 mm as in the conventional case. The shape of the intermediate cylinder is not particularly limited as long as it has the same thermal expansion coefficient as the honeycomb body and can absorb the thermal stress generated in the honeycomb body. For example, it may be configured to have a bending portion at one end or both ends. The flexible portion may have a comb-like configuration in which grooves are arranged in the circumferential direction, or a configuration in which slits are arranged in the circumferential direction.

The intermediate cylinder has an upstream end joined to the outer cylinder and a downstream end joined to the honeycomb body. Thereby, the stress of the radial expansion of the honeycomb body or the stress of the contraction of the outer cylinder can be absorbed by the deformation of the intermediate cylinder, and the generation of thermal stress can be prevented. The greatest feature of the present invention is that the length of the intermediate cylinder in the axial direction is shorter than the length of the honeycomb body in the axial direction, and the junction with the outer cylinder at the upstream end of the intermediate cylinder is near the upstream end face of the honeycomb body. It is located downstream from the junction. That is, there is no intermediate cylinder on the outer peripheral side of the joined portion near the upstream end face of the honeycomb body, and the honeycomb body directly faces the outer cylinder with an interval. Thereby, a large clearance between the honeycomb body and the outer cylinder can be secured, and the expansion in the radial direction of the honeycomb body is not restricted, so that the generation of thermal stress can be further prevented.

[0011]

The vicinity of the upstream end face located on the upstream side of the exhaust gas of the honeycomb body receives stress due to the pulsation of the exhaust gas, and therefore, it is necessary to join the flat plate and the corrugated plate to have strength. However, when joined in this manner, the thermal expansion of the flat plate and the corrugated sheet is not absorbed by the deformation in the circumferential direction, and most of the expansion is in the radial direction, so that the amount of expansion in the radial direction is larger than the unjoined part. .

Therefore, in the metal carrier for an exhaust gas purifying catalyst of the present invention, the honeycomb body has a joint near the upstream end face where the flat plate and the corrugated plate are joined at least near the upstream end face located on the upstream side of the exhaust gas. The length of the intermediate cylinder in the axial direction is shorter than the length of the honeycomb body in the axial direction, and the joint between the intermediate cylinder and the outer cylinder at the upstream end is located downstream of the joint near the upstream end face of the honeycomb body. It is configured to be.

[0013] With this configuration, the intermediate cylinder does not exist on the outer periphery of the joined portion near the upstream end face of the honeycomb body, so that a large clearance between the honeycomb body and the outer cylinder can be ensured. Therefore, even if the joint near the upstream end face is largely thermally expanded in the radial direction, contact with the outer cylinder can be avoided, and thermal stress is prevented from acting on the joint near the upstream end face.

Further, in the metal carrier for an exhaust gas purifying catalyst according to the present invention, the honeycomb body is basically joined to the outer cylinder at only one position, similarly to the one disclosed in JP-A-3-157139. Therefore, thermal expansion in the axial direction is not hindered,
The generation of axial thermal stress is also prevented.

[0015]

The present invention will be specifically described below with reference to examples. FIG.
FIG. 1 shows a sectional view of a metal carrier according to one embodiment of the present invention. This metal carrier has a honeycomb body 1 formed by laminating a flat plate made of a Fe—Cr—Al alloy having a thickness of 0.05 mm and a corrugated sheet and winding the roll into a roll shape, and a thermal expansion similar to that of the honeycomb body 1. Intermediate cylinder 2 having a thickness of 0.3 to 1 mm and a thickness of 1 to 2
mm ferrite stainless steel outer cylinder 3.

The honeycomb body 1 has a joint 10 near the upstream end face where the flat plate and the corrugated plate are joined near the upstream end face located on the upstream side of the exhaust gas, and the downstream end face near the downstream end face. A near joint 11 is formed. In the middle part between these, the flat plate and the corrugated plate are not joined, so that thermal stress is prevented from acting. The intermediate cylinder 2 is shown in FIG.
As shown in FIG. 3, the plurality of axially extending flexible grooves 20 are arranged at both ends at intervals in the circumferential direction.
The bent portions 21 are formed at both ends due to the presence of the. In the bending portion 21, the diameter of the bending groove 20 is increased or reduced by enlarging or reducing the width of the bending groove 20.
Diameter reduction is easy.

The outer peripheral surface (shaded portion in FIG. 2) of the upstream end portion 22 of the intermediate cylinder 2 and the inner peripheral surface of the outer cylinder 3 are joined by the upstream brazing portion 40, and the downstream side of the honeycomb body 1 The outer peripheral surface of the joint 11 near the end face and the inner peripheral surface of the downstream end 23 of the intermediate cylinder 2 are joined by a downstream brazing part 41. By joining in a cantilever manner in this manner, the expansion and contraction movements of the honeycomb body 1 are not hindered, and the generation of thermal stress is prevented.

The axial length of the honeycomb body 1 and the outer cylinder 3 is the same, and the axial length of the intermediate cylinder 2 is shorter than that of the honeycomb body 1. The downstream end surface of the downstream end 23 of the intermediate tube 2 and the downstream end surfaces of the honeycomb body 1 and the outer tube 3 are flush with each other and coincide with each other. That is, the end face of the upstream end portion 22 of the intermediate cylinder 2 is located inside the upstream end faces of the honeycomb body 1 and the outer cylinder 2, and the outer peripheral surface of the joining portion 10 near the upstream end face of the honeycomb body 1 has the intermediate cylinder 2. Does not exist, and a cylindrical space 5 is formed between the honeycomb body 1 and the outer cylinder 3.

The honeycomb body 1 and the outer cylinder 3 in this space 5
Is obtained by adding the thickness of the upstream brazing portion 40 and the thickness of the downstream brazing portion 41 to the thickness of the intermediate cylinder 2, and the diameter of the joining portion 10 near the upstream end face of the honeycomb body 1 during use is reduced. Even if it is thermally expanded, it has a sufficient size so that it does not come into contact with the outer cylinder 3. That is, according to the metal carrier of the present embodiment,
The honeycomb body 1 has a sufficient strength against the external force such as the pulsation of the exhaust gas by the joint 10 near the upstream end face. Even if the upstream end face vicinity joint 10 is largely thermally expanded in the radial direction, the contact with the outer cylinder 3 is prevented by the presence of the space 5, so that thermal stress acts on the upstream end face vicinity joint 10. Has been prevented.

In the central portion of the honeycomb body 1, since the flat plate and the corrugated plate are not joined to each other, even if the flat plate and the corrugated plate expand and come into contact with the intermediate cylinder 2, the thermal stress is absorbed by the relative movement of the flat plate and the corrugated plate. Is done. Furthermore, although the downstream end surface vicinity joint portion 11 is joined to the intermediate cylinder 2, the thermal expansion of the downstream end surface vicinity joint portion 11 is absorbed by the deformation of the bending portion 21, thereby preventing generation of thermal stress.

The honeycomb body 1 has a downstream brazing portion 4
1 is joined to the intermediate cylinder 2, and the intermediate cylinder 2 is joined to the outer cylinder 3 only at the upstream brazing portion 40. Therefore, since the honeycomb body 1 can freely expand and contract in the axial direction, generation of thermal stress in the axial direction is also prevented.

[0022]

According to the metal carrier for an exhaust gas purifying catalyst of the present invention, since the generation of thermal stress is further prevented as compared with the conventional metal carrier, cracking of the honeycomb body is further prevented. And a longer life.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a metal carrier for an exhaust gas purifying catalyst according to one embodiment of the present invention.

FIG. 2 is a perspective view illustrating a configuration of a metal carrier for an exhaust gas purifying catalyst according to one embodiment of the present invention.

[Explanation of symbols]

1: Honeycomb body 2: Intermediate cylinder
3: Outer cylinder 10: Joint near upstream end face 40, 41: Brazing part

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Keizo Tanaka 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-3-157139 (JP, A) JP-A-4-222636 (JP, A) JP-A-4-27443 (JP, A) JP-A-4-41727 (JP, U) JP-A-3-79838 (JP, U) (58) Fields investigated (Int. Cl. ⁷⁾ B01J 21/00-37/36 B01D 53/86 F01N 3/28

Claims (1)

(57) [Claims] 1. A honeycomb body in which a flat plate and a corrugated sheet are stacked and wound into a roll, an outer cylinder for housing the honeycomb body, an intermediate cylinder interposed between the honeycomb body and the outer cylinder, Wherein the honeycomb body has a joint near the upstream end face where the flat plate and the corrugated sheet are joined at least near the upstream end face located on the upstream side of the exhaust gas. The intermediate cylinder has an upstream end located on the upstream side of the exhaust gas joined to the outer cylinder and a downstream end joined to the honeycomb body. The axial length of the intermediate cylinder is the honeycomb. A joint portion with the outer tube at the upstream end portion of the intermediate tube, which is shorter than a joint portion near the upstream end surface of the honeycomb body, which is shorter than an axial length of the body. Metal carrier for exhaust gas purifying catalyst.