Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Waste gas purifier
Reexamination Certificate
2000-03-06
2004-02-10
Tran, Hien (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Waste gas purifier
C422S177000, C502S439000, C029S890000, C428S593000, C228S181000, C228S193000
Reexamination Certificate
active
06689328
ABSTRACT:
TECHNICAL FIELD
This invention relates to a metal honeycomb body for supporting a catalyst for purifying an exhaust gas emitted from an internal combustion engine such as an automobile engine, and a method for producing the same.
BACKGROUND ART
A metal support having excellent initial purification performance of an exhaust gas and a small exhaust resistance has been used recently, in many cases, for a catalyst device of an automobile. The metal support of this kind uses a cylindrical honeycomb body produced by superposing a metal flat foil with a metal corrugated foil, that is obtained by subjecting the metal flat foil to plastic processing into a corrugation form, with one another, and winding them into a spiral shape, or a honeycomb body produced by superposing alternately plane-wise the flat foil and the corrugated foil. The metal honeycomb body is then assembled into a casing such as a metal outer cylinder and the two parts are mutually bonded. After a catalyst is fitted to and supported by the metal honeycomb body, the resulting catalyst device is used as an exhaust gas purification apparatus for the automobile.
As shown in
FIG. 1
, for example, a conventional metal support
1
is produced by assembling a metal honeycomb body
2
formed of heat-resistant stainless steel foils into an outer cylinder
3
made of a metal. The metal honeycomb body
2
is produced mainly by superposing an about 50 &mgr;m-thick belt-like flat foil
5
with a belt-like corrugated foil
6
, that is obtained by subjecting the flat foil
5
to corrugation shaping, and winding these foils into a spiral shape round a take-up axis S indicated by arrow B in a direction as shown in FIG.
2
. A ridgeline
7
of each corrugation is formed on the belt-like corrugated foil
6
in a width-wise direction. The circular cylindrical metal honeycomb body
2
wound into the spiral shape has a large number of vent holes
4
in the axial direction of the circular cylinder. The catalyst is supported by these vent holes, forming a catalyst converter.
The catalyst support must have excellent durability in order to withstand severe heat cycles, due to a high temperature exhaust gas from an engine, and also to withstand vigorous vibration from the engine. Therefore, in the metal support
1
according to the prior art, the contact portions between the flat foil
5
and the corrugated foil
6
of the honeycomb body
2
are bonded, and the outer periphery of the metal honeycomb body
2
and the inner periphery of the outer cylinder
3
are bonded, too.
Generally, the metal foil that constitutes the metal honeycomb body mostly uses a high heat-resistant stainless steel formed of Cr—Al—Fe. For, aluminum (Al) in the foil is selectively oxidized on the surface to form Al
2
O
3
, improving thereby the oxidation resistance. Therefore, the Al amount in the metal foil exerts significant influences on durability of the metal support.
Bonding inside the metal honeycomb body is executed by fixing a Ni type powdery brazing material to the contact portions between the flat metal foil and the corrugated metal foil through an organic material such as a binder, and conducting a brazing treatment inside a vacuum furnace. In this case, Al in the metal foils tends to combine extremely strongly and firmly with Ni in the brazing material, and Al segregates near the brazing portion. On the other hand, Al in the proximity of the segregation portion becomes lean. In consequence, the oxidation resistance is deteriorated locally and invites a problem in durability. Furthermore, the brazing material is extremely expensive from the aspect of the production cost, and impedes the supply of economical metal supports to users.
Therefore, several methods of producing the metal support without using the brazing material have been proposed. For example, Japanese Unexamined Patent Publication (Kokai) No.1-266978 discloses a method of producing a metal honeycomb body by bonding a metal flat foil and a metal corrugated foil by a solid phase diffusion bonding method at a treating temperature of 1,200° C. (850 to 1,200° C. in claims) and a vacuum of 10
−6
Torr (10
−2
to 10
−6
Torr in claims). However, this method has failed to secure durability that is required for an exhaust gas. Since this reference does not describe the treating time and the Al amount after the treatment, the relationship of these factors to an exhaust gas purification performance is not clear, either. On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 5-168947 proposes a method that conducts the treatment at a high temperature (1,400° C.). However, since this method uses a jig for preventing Al evaporation, the method is not completely free from problems from the aspects of productivity and production cost.
Generally when diffusion bonding is executed, materials to be bonded are brought into close contact with each other, and a surface pressure is always applied to them during heating, too, by using a press device or a weight. However, it is not possible to apply, from the outside, such a surface pressure to the metal honeycomb body
2
wound spirally as described above. Therefore, the surface pressure is applied during winding by applying a back-tension to the flat foil
5
in a direction of arrow A as shown in
FIG. 2
, or by inserting the honeycomb body
2
into the outer cylinder
3
and then reducing the diameter of the outer cylinder
3
.
However, back-tension during the-winding operation cannot apply a sufficient surface pressure to the outer peripheral portion of the metal honeycomb body
2
, and contraction of the diameter of the outer cylinder
3
cannot provide a sufficient surface pressure, either. Even when they are used in combination, the surface pressure cannot be applied sufficiently to the intermediate portion between the center of the honeycomb body
2
and its outer peripheral portion. If the back-tension is raised in order to impart the surface pressure. necessary for the intermediate portion, the vent holes
4
at the center undergo buckling. If the contraction ratio is raised, on the other hand, the vent holes at the outer peripheral portion undergo buckling.
To solve this problem, the inventors of the present invention have found that diffusion bonding can be achieved satisfactorily from the center to the outer peripheral portion by reducing the surface coarseness of the flat foil
5
and the corrugated foil
6
, and applying the back-tension and conducting contraction of the outer cylinder diameter to such a range in which the intermediate portion of the metal honeycomb body
2
does not undergo buckling. Consequently, the present invention sets the surface coarseness of the flat foil
5
and the corrugated foil
6
to 0.001 &mgr;m to 0.2 &mgr;m in terms of the mean coarseness (Ra). The present inventors have described this proposal in Japanese Unexamined Patent Publication (Kokai) No. 8-38912.
This prior art reference limits the surface coarseness of the flat foil
5
and the corrugated foil
6
to 0.001 to 0.2 &mgr;m in terms of mean coarseness Ra, but does not mention the measuring direction of the surface coarseness. The reference also limits the contact width of the flat foil
5
and the corrugated foil
6
to at least 30 &mgr;m in the length-wise direction. According to an Example of this reference, when the contact width of the flat foil and the corrugated foil is 20 &mgr;m, contact defects occur even when Ra is 0.1 &mgr;m.
According to observations by the present inventors, durability of the diffusion bond portion is not sufficient if the surface coarseness measured in the crossing direction (D direction) is great even though the surface coarseness measured in the longitudinal direction of the belt-like flat foil
5
and the corrugated foil
6
is within the range described above.
Japanese Unexamined Patent Publication (Kokai) No. 5-131144 proposes the construction in which each of the peak and the valley of each corrugation of the corrugated foil
6
defines a parallel portion having a width greater than the foil thic
Egami Toshihiro
Imai Atuhiko
Iwami Kazutoshi
Kasuya Masayuki
Noda Tamio
Nippon Steel Corporation
Tran Hien
LandOfFree
Metal honeycomb body for exhaust gas purification catalyst... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Metal honeycomb body for exhaust gas purification catalyst..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Metal honeycomb body for exhaust gas purification catalyst... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3283174