Gas duct having honeycomb structure

Details Gas duct having honeycomb structure Gas duct having honeycomb structure

1999-06-21

2002-01-15

Tran, Hien (Department: 1764)

Chemical apparatus and process disinfecting, deodorizing, preser

Chemical reactor

Waste gas purifier

C422S171000, C422S177000, C422S179000, C422S173000

Reexamination Certificate

active

06338826

ABSTRACT:

BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a gas duct having a honeycomb structure, used mainly in an automobile exhaust gas purification system.
(2) Description of Related Art
Currently, gas ducts with honeycomb structure are in extensive use because they have low pressure loss (when a gas is passed therethrough) owing to their high open frontal area, and the structures show an excellent exhaust gas purifiability. As an example of such gas ducts, a widely known ceramic honeycomb catalytic converters are used in exhaust gas purification systems for automobiles.
To produce such a ceramic honeycomb catalytic converter, a ceramic honeycomb catalyst is held in a converter casing (this operation is called “canning”) for easy handling of the honeycomb catalyst.
For example, as shown in FIGS.
4
(
a
) and
4
(
b
), in order to reliably hold a honeycomb catalyst
12
in a metal case
11
and further lessen the impact applied to the catalyst
12
from outside, a ceramic fiber mat
13
is inserted, under pressure, between the outer surface of the honeycomb catalyst
12
and the inner surface of the metal case
11
, after which the honeycomb catalyst
12
is held in the metal case
11
in the axial direction of the metal case
11
. Specifically, a hook
14
, which is fitted to one end of the metal case
11
and projects toward the center of a circle formed by the one end of the metal case
11
, and a retainer ring
15
welded to the other end of the metal case
11
or a plurality of projections
16
(see FIGS.
5
(
a
) and
5
(
b
)) extending from the other end of the metal case
11
, but bent towards the center of a circle formed by the other end of the metal case
11
, are allowed to abut on the honeycomb catalyst
12
; then, each one cone (not shown), which is a metal member enabling easier incoming and discharging of exhaust gas, is fitted to the both ends of the metal case
11
by welding, or the like.
When the honeycomb catalyst
12
is held in the metal case
11
as above, however, the hook
14
and the retainer ring
15
both fitted to the metal case
11
block part of the passages of the honeycomb catalyst
12
, which makes impossible the effective utilization of the whole volume of the honeycomb catalyst
12
, and moreover incurs an increase in pressure loss. This leads to an increase in emission or a reduction in engine performance when the metal case
11
holding the honeycomb catalyst
12
is used as a honeycomb catalytic converter.
Further, since the hook
14
and the retainer ring
15
are fitted to the metal case
11
, there arises an increase in processing cost and material cost of honeycomb catalytic converter.
SUMMARY OF THE INVENTION
In order to alleviate the above-mentioned problems of the related art, the present invention aims at providing a gas duct having a honeycomb structure, which utilizes the whole volume of the honeycomb structure, which is lower in pressure loss, and which is lower in cost.
According to the present invention, there is provided a gas duct having a honeycomb structure, which comprises:
a metal case,
a honeycomb structure accommodated in the metal case,
a holding member placed between the outer surface of the honeycomb structure and the inner surface of the metal case, and
a cone(s) fitted to the inner surface of the metal case at one or both openings of the metal case, wherein the circumference(s) of one or both end faces of the honeycomb structure is (are) allowed to abut on the cone(s).
In the gas duct comprising a honeycomb structure, of the present invention, it is preferable that the circumference(s) of the end face(s) of the honeycomb structure abuts (abut) on the cone(s) at an angle of 45° to 85°.
In the gas duct having a honeycomb structure, of the present invention, it is also preferable that the circumference(s) of the end face(s) of the honeycomb structure is (are) chamfered and the size or radius of chamfering is 0.1 to 1 mm.
The gas duct having a honeycomb structure, of the present invention preferably takes the following form:
the honeycomb structure is made of a ceramic or a metal, and is a catalyst for exhaust gas purification, a filter for capturing the particulate substances present in exhaust gas, or a heat exchanger;
the holding member is a ceramic fiber mat or a metal-made wire mesh; and
the metal case has a stuffing structure, a tourniquet structure, or a clam-shell structure.


REFERENCES:
patent: 3801289 (1974-04-01), Wiley
patent: 5693295 (1997-12-01), Foster
patent: 5866079 (1999-02-01), Machida et al.
patent: 2 324 866 (1973-11-01), None
patent: 35 06 219 (1986-09-01), None
patent: 2-126016 (1990-10-01), None
patent: 7-77036 (1995-03-01), None

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