Metal working – Method of mechanical manufacture – Fluid pattern dispersing device making – e.g. – ink jet
Patent
1997-04-11
1999-12-07
Tran, Hien
Metal working
Method of mechanical manufacture
Fluid pattern dispersing device making, e.g., ink jet
422179, F01N 328
Patent
active
059962283
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a monolith-holding element, a process for the production of the monolith-holding element, a catalytic converter using a monolith member composed of a monolith and monolith-holding element, and a process for the production of the catalytic converter. The monolith-holding member according to the present invention is maintained in a compressed state by a bonding force of an organic binder upon assembling, and restore its inherent thickness and exhibits a required surface pressure in a both surface-supporting state by the thermal decomposition of the organic binder after heating. In the catalytic converter according to the present invention, the afore-mentioned monolith-holding element stably supports the monolith within a casing for a long period of time.
BACKGROUND ART
In exhaust systems of internal combustion engines, various catalytic converters containing heavy metals or noble metals as a catalyst have been used as an apparatus for cleaning exhaust gases in order to treat and remove harmful components in the exhaust gases, such as carbon monoxide or various hydrocarbons. These catalytic converters are classified into the following two types according to the configuration of catalysts used therein: supporting a metal catalyst on a granular carrier made of ceramics or the like, and a metal casing for accommodating the pellet-like catalyst; and by supporting a metal catalyst on a tubular monolith carrier (hereinafter referred to merely as "monolith") inside of which a plurality of flow paths for passing exhaust gases are provided, and a metal casing accommodating the integrated catalyst and connected with exhaust pipes.
The catalytic converters (2) have been more predominately utilized as compared with those of the catalytic converters (1) because the catalytic converters (2) do not show abrasion due to collision between pellets as observed in the catalytic converters (1) and have relatively miniaturized the apparatus. In the catalytic converters (2), in order to securely mount a monolith member within a metal casing, a monolith-holding element is wound around a monolith.
In many cases, the monoliths made of ceramics or metals have been used in order to impart a heat resistance thereto. Further, in order to reduce a flow resistance during passing of exhaust gases and enhance an efficiency of the catalyst, there have been predominately utilized monoliths having a honeycomb structure, whereby more larger surface area can be assured in flow paths of exhaust gases.
As an appropriate structure of the metal casings, there has been adopted a two-piece clamshell structure in which the monolith member is sandwiched between shell halves of the metal casing and the mating portions of the shell halves are welded together, or a stuffing box structure in which the monolith member is inserted into the metal casing.
In either the clamshell or stuffing box structure, it is required that the thickness of the monolith-holding element is identical with or slightly larger than a clearance between an outer peripheral surface of the monolith and an inner peripheral surface of the metal casing in order to securely fix the monolith within the metal casing. This is because the decrease in retaining force of the monolith-holding element against the monolith causes inconveniences such as separation or displacement of the monolith within the metal casing, leakage of exhaust gases from the outer peripheral surface of the monolith, or the like, during operation. Occurrence of such inconveniences is highly detrimental to the catalytic converters.
Especially, in the case where a ceramic monolith is used in the catalytic converter, the clearance between the outer peripheral surface of the monolith and the inner peripheral surface of the metal casing becomes large during operation because the monolith itself exhibits a small thermal expansion while the metal casing exhibits a large thermal expansion. As a result, there has been a tendency that the retaining force of the monolith-holding ele
REFERENCES:
patent: 4929429 (1990-05-01), Merry
Kasuya Masayuki
Ohta Hitoshi
Sasaki Toshiaki
Shoji Mamoru
Mitsubishi Chemical Corporation
Nippon Steel Corp.
Tran Hien
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