JPH04235717A - Metal carrier for exhaust gas purification catalyst - Google Patents

Abstract

PURPOSE:To prevent occurrence of fracture by preventing thermal stresses in diametrical or longitudinal directions of a honeycomb body. CONSTITUTION:Two pieces of elastic holding members 3, 3 are employed, wherein each of said members is secured to the inner periphery of an outer cylinder 2 and to the outer periphery of each end of a honeycomb body 1 to hold the honeycomb body 1 within the outer cylinder 2 in an elastically deformable manner in the diametrical and longitudinal directions of the body 1.

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 in an exhaust gas purification catalyst for an internal combustion engine.

0002

[Prior art] As a metal carrier for exhaust gas purification catalyst,
It is known that a flat plate and a corrugated plate are stacked and rolled to form a honeycomb body, and the honeycomb body is housed in a metal outer cylinder. In this metal carrier, the flat plate and corrugated plate of the honeycomb body, the outer cylinder, and the honeycomb body are usually integrally joined by brazing. With this metal carrier,
A catalyst support layer made of alumina or the like is formed on the surface of the honeycomb passages of the honeycomb body, and a noble metal catalyst is supported on the catalyst support layer to form an exhaust gas purification catalyst. The exhaust gas purification catalyst is disposed in the exhaust passage of the internal combustion engine and purifies HC, CO, NOx, etc. in the exhaust gas. Note that since it is desirable to secure as much area as possible for honeycomb passages in a limited volume, the thicknesses of the flat plates and corrugated plates are made as thin as possible within a range that maintains strength.

[0003] Incidentally, the flow velocity of exhaust gas passing through a honeycomb body is greater at the center than at the outer periphery of the honeycomb body. For this reason, metal carriers have higher temperatures at the center due to contact with high-temperature exhaust gas and heat generated by catalytic reactions.
A temperature distribution occurs in which the temperature becomes lower toward the outer periphery. Furthermore, since heat is released from the outer cylinder to the outside, the difference is further increased at the outer peripheral portion that is in contact with the outer cylinder. Therefore, the amount of expansion due to heat and the amount of contraction during cooling are larger at the center of the honeycomb body, and the amount of expansion and contraction of the outer tube is the smallest. here,
The thicknesses of the flat plates and corrugated plates that make up the honeycomb body are generally much smaller than the thickness of the outer cylinder. Therefore, the stress generated due to the difference in the amount of expansion and contraction (hereinafter referred to as thermal stress) is concentrated at the boundary between the honeycomb body and the outer cylinder, and may cause cracks or buckling in the honeycomb body at that area. Ta. When a break occurs in the honeycomb portion in this way, not only does the catalyst performance deteriorate, but the honeycomb body and the outer cylinder move relative to each other, increasing pressure loss, which may lead to a decrease in engine output.

In order to prevent such problems, Japanese Patent Publication No. 57-55886 discloses a metal carrier in which a gap is provided between the honeycomb body and the outer cylinder. According to this metal carrier, the honeycomb body and the outer cylinder are thermally insulated due to the heat insulating effect of the air layer existing in the gap, and the honeycomb body can freely expand and contract within the gap. The generation and concentration of thermal stress can be prevented to some extent, and the above-mentioned breakage can be prevented to some extent.

[0005]

[Problems to be Solved by the Invention] However, in the metal carrier of the above publication, the honeycomb body and the outer cylinder are joined by welding between both ends, so that the radial expansion and contraction of the honeycomb body is prevented at both ends. Movement is restricted and radial thermal stress is still concentrated at both ends. Further, in this metal carrier, since the axial expansion and contraction movements of the honeycomb body are also restricted, axial thermal stress is likely to occur. Therefore, this metal carrier could not completely prevent the honeycomb body from breaking.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to further prevent the generation of thermal stress in the radial and axial directions of a honeycomb body, and to further prevent the occurrence of breakage. .

[0007]

[Means for Solving the Problems] The metal carrier for an exhaust gas purification catalyst of the present invention includes a honeycomb body formed by stacking a flat plate and a corrugated plate and winding them into a roll, and a radial direction around the outer periphery of the honeycomb body. An outer cylinder arranged with a predetermined gap therebetween, and fixed to the inner peripheral surface of the outer cylinder and the outer peripheral surface of the honeycomb body, and the honeycomb body is inserted into the outer cylinder so as to be elastically deformable in the radial and axial directions. It is characterized by comprising a ring-shaped elastic holding member for holding.

A honeycomb body is formed by stacking a flat plate and a corrugated plate and winding them into a roll. A corrugated plate is usually formed by bending a flat plate into a wave shape, and is made of the same material as the flat plate and has the same thickness. The flat plate and corrugated plate are made of, for example, stainless steel foil, as in the conventional case. Since it is preferable to secure as much area as possible for honeycomb passages in a limited volume as described above, a relatively thin plate having a thickness of, for example, 0.05 mm is used. This honeycomb body is formed by, for example, applying a brazing material to the top of a corrugated sheet, stacking it on a flat sheet, rolling it up into a roll, and heating the corrugated sheet. As a result, the flat plate and the corrugated plate are brazed and integrally joined. Alternatively, they can be integrated by diffusion bonding.

[0009] The outer cylinder may be made of stainless steel or the like as in the past, and its plate thickness is usually about 1 to 2 mm, as in the past. The greatest feature of the present invention is
It has a ring-shaped elastic holding member. The elastic holding members are fixed to the inner circumferential surface of the outer cylinder and the outer circumferential surface of the honeycomb body, respectively, and hold the honeycomb body within the outer cylinder so as to be elastically deformable in the radial direction and the axial direction. The elastic holding member may have, for example, a substantially U-shaped cross section, a substantially question mark-shaped cross section, a substantially S-shaped cross section, or the like. This elastic holding member shall be made of the same material as the honeycomb body, a material with the same coefficient of thermal expansion as the material of the honeycomb body, or a material with a coefficient of thermal expansion substantially equal to the material of the honeycomb body. is preferred. This elastic holding member can be obtained by subjecting a plate-shaped member to plastic working such as bending and drawing.

0010

[Function] In the metal carrier for exhaust gas purification catalyst of the present invention,
Since the elastic holding member holds the honeycomb body within the outer cylinder so as to be elastically deformable in the radial and axial directions, the radial expansion and contraction movements of the honeycomb body are absorbed by the radial elastic deformation of the elastic holding member. The movement of expansion and contraction in the axial direction is absorbed by the elastic deformation of the elastic holding member in the axial direction. Therefore, radial thermal stress and axial thermal stress are not concentrated on the honeycomb body.

Furthermore, since there is a gap between the outer cylinder and the honeycomb body, the honeycomb body becomes thermally insulated due to the heat insulating effect of the air in the gap. Therefore, the temperature distribution within the honeycomb body becomes uniform, and this also prevents the generation of thermal stress. Furthermore, in this metal carrier, the honeycomb body is held by the ring-shaped elastic holding member on the outer cylinder and is sealed on the entire surface at the same time, so that exhaust gas is easily guided into the honeycomb body.

0012

Embodiments 1 to 3 embodying the present invention will be described below with reference to the drawings. (Example 1) As shown in FIGS. 1 to 3, this metal carrier includes a honeycomb body 1, an outer cylinder 2 disposed around the outer circumference of the honeycomb body 1, and a honeycomb body 1 held in the outer cylinder 2. It consists of two pieces of elastic holding members 3, 3.

As shown in FIG. 2, the honeycomb body 1 is made up of a flat plate 10 made of stainless steel foil or the like with a thickness of 0.05 mm, and a corrugated plate 11 made of the same material as the flat plate 10 and formed by bending into a wave shape. It is configured. This honeycomb body 1 is formed by stacking a flat plate 10 and a corrugated plate 11 and rolling it into a roll with the flat plate 10 facing up, thereby forming honeycomb passages inside. Note that the top of the corrugated plate 11 and the flat plate 10
A solder is interposed between them, and the flat plate 10 and the corrugated plate 11 are integrally joined by brazing.

The outer cylinder 2 is made of stainless steel and has a cylindrical shape with a plate thickness of 1.5 mm. Between the inner circumferential surface of the outer cylinder 2 and the outer circumferential surface of the honeycomb body 1, two pieces of elastic holding members 3, 3 are fixed as shown in FIGS. 1 and 3. Each elastic holding member 3, 3 is made of the same material as the honeycomb body 1, and as shown in FIG. 3, has a long end 3a, a short end 3b, and a single curvature R. It is a ring-shaped member formed with a substantially U-shaped cross section and a bent portion 3c connected at a . Each elastic holding member 3, 3 has a respective elongated end 3
a, 3a are brazed to the outer circumferential surface of each end of the honeycomb body 1, and each short end 3b, 3b is fixed by brazing the entire surface to the inner circumferential surface of the outer cylinder 2. In this way, each elastic holding member 3, 3 holds the honeycomb body 1 in the outer cylinder 2 so as to be elastically deformable in the radial and axial directions, and holds the honeycomb body 1 and the outer cylinder 2.
A gap 6 corresponding to the thickness of the elastic holding members 3, 3 is formed between them. Each elastic holding member 3, 3 is obtained by plastic working a plate-shaped member.

[0015] In this metal carrier, a catalyst supporting layer made of activated alumina is formed to cover the honeycomb passage surface of the honeycomb body 1, and a noble metal catalyst is supported on the catalyst supporting layer to be used as an exhaust gas purification catalyst. And the exhaust gas purification catalyst is
As shown in FIG. 1, a catalytic converter is formed with conical cones 4 and 5 having mounting flanges 41 and 51 and forming an inlet and an outlet for exhaust gas. And the catalytic converter is
It is placed in the exhaust passage of an internal combustion engine to remove HC and C in the exhaust gas.
Purifies O, NOx, etc.

In this metal carrier, when the honeycomb body 1 expands in the radial direction due to heat during purification, the bent portions 3c, 3c of the elastic holding members 3, 3 shown in FIG. 3 reduce the curvature R, and the diameter increases. Absorbs stress due to directional expansion. If the honeycomb body 1 contracts in the radial direction during cooling due to stopping of purification, the respective bent portions 3c, 3c of the respective elastic holding members 3, 3 increase the curvature R, and absorb the stress due to the radial contraction. Further, in this metal carrier, when the honeycomb body 1 expands or contracts in the axial direction, the long ends 3a, 3a and the short ends 3b, 3b of the elastic holding members 3, 3 are bent at the bent portions 3c, 3c. They have different lengths to absorb stress in the axial direction. Therefore, the thermal stress in the radial direction and the thermal stress in the axial direction are reduced to the honeycomb body 1.
I don't concentrate on it. Further, since a gap 6 exists between the outer cylinder 2 and the honeycomb body 1, the honeycomb body 1 becomes thermally insulated due to the heat insulating effect of the air in the gap 6. Therefore, the temperature distribution within the honeycomb body 1 becomes uniform, and this also prevents the generation of thermal stress. therefore,
This metal carrier can further prevent the occurrence of thermal stress in the radial and axial directions of the honeycomb body 1, and further prevent the occurrence of cracks and buckling. (Example 2) In this metal carrier, as shown in FIG.
Long end 7a, short end 7b, long end 7a and short end 7
a ring-shaped elastic holding member 7 formed in a substantially U-shaped cross section, consisting of a bent portion 7c connecting b with two curvatures R;
7 is adopted. The other configurations are the same as in the first embodiment.

In this metal carrier, when the honeycomb body 1 expands or contracts in the radial direction, each bending portion 7c, 7c of each elastic holding member 7, 7 decreases or increases the curvature R of at least one of them, and the diameter Absorb directional stress. Moreover, in this metal carrier, if the honeycomb body 1 expands or contracts in the axial direction, each of the long ends 7a, 7a of each elastic holding member 7, 7
and the short ends 7b, 7b have different lengths via the respective bent portions 7c, 7c to absorb stress in the axial direction.

[0018] Therefore, also in this metal carrier,
Effects similar to those of Example 1 can be obtained. (Example 3) In this metal carrier, as shown in FIG.
Long end 8a, short end 8b, long end 8a and short end 8
a ring-shaped elastic holding member 8 formed into a substantially question mark-shaped cross section, and consisting of a bent portion 8c connecting b with three curvatures R;
, 8 is adopted. The other configurations are the same as in the first embodiment.

In this metal carrier, when the honeycomb body 1 expands or contracts in the radial direction, each bent portion 8c, 8c of each elastic holding member 8, 8 decreases or increases the curvature R of at least one of them, and the diameter Absorb directional stress. Moreover, in this metal carrier, if the honeycomb body 1 expands or contracts in the axial direction, each of the long ends 8a, 8a of each elastic holding member 8, 8
and the short ends 8b, 8b have different lengths via the respective bent portions 8c, 8c, and absorb stress in the axial direction.

[0020] Therefore, also in this metal carrier,
Effects similar to those of Example 1 can be obtained. In particular, in this metal carrier, since the respective long ends 8a, 8a of the respective elastic holding members 8, 8 are connected to the respective bent portions 8c, 8c with a step due to the curvature R, the honeycomb body 1 is held in the axial direction. Superior in strength. In addition, the above Examples 1 to 3
Here, elastic holding members of the same shape are combined, but it goes without saying that elastic holding members of different shapes can be combined. For example, since the suction side of exhaust gas tends to be higher in temperature and the honeycomb body is more likely to expand on the suction side, an elastic holding member that is more easily deformed elastically may be provided at the end of the honeycomb body on the suction side.

[0021]

As described in detail above, in the metal carrier of the present invention, the elastic holding member holds the honeycomb body within the outer cylinder so as to be elastically deformable in the radial and axial directions. It is possible to further prevent the occurrence of thermal stress in the axial direction, and further prevent the occurrence of cracks and buckling. Therefore, catalyst performance can be further maintained, pressure loss can be prevented from increasing, and engine output can be maintained more favorably.

Furthermore, in this metal carrier, the elastic holding member can absorb not only the deformation of the honeycomb body due to heat, but also the vibration during use. Therefore, the honeycomb body has excellent holding power, and its durability as an exhaust gas purification catalyst can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a catalytic converter to which a metal carrier of Example 1 is fixed.

FIG. 2 is a sectional view taken along line AA in FIG. 1;

FIG. 3 is an enlarged cross-sectional view of the main part of FIG. 1;

FIG. 4 is an enlarged sectional view of a main part of a metal carrier of Example 2.

FIG. 5 is an enlarged sectional view of a main part of a metal carrier of Example 3.

[Explanation of symbols]

1...honeycomb body 10...flat plate
11...Corrugated plate

Claims (1)

[Claims] Claims: 1. A honeycomb body formed by stacking a flat plate and a corrugated plate and winding them into a roll; an outer cylinder disposed on the outer periphery of the honeycomb body with a predetermined gap in the radial direction; A ring-shaped elastic holding member is fixed to an inner circumferential surface and an outer circumferential surface of the honeycomb body, and holds the honeycomb body within the outer cylinder so as to be elastically deformable in the radial and axial directions. Metal carrier for exhaust gas purification catalyst.