Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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CATALYZING SYSTEM
The present invention relates to a catalyzing
system to be connected for use with an automotive
engine.
Since an automotive engine exhausts a variety of
noxious contents, various devices have been made to
reduce the noxious contents to a predetermined level.
One method practised for the devices with satisfactory
results is exemplified by using a catalyst. In this
example, as shown in Fig. 7, a catalyzing system 1 is
constructed such that there are arranged in tandem in a
catalyst case 4 (which will be shortly referred to as
the "case") a primary reducing catalyst 5 for mainly
reducing nitrogen oxides,NOx,and a secondary oxidizing
catalyst 6 for mainly oxidizing carbon monoxide CO and
hydrocarbons HCand such that secondary air is supplied
toward the oxidizing catalyst 6 from between the re-
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ducing catalyst 5 and the oxidizing catalyst 6. This
structure is known to give the satisfactory results (as
disclosed in Japanese Utility Model Laid-Open No. Sho 58-
118212).
In order to make this structure, according to the
prior art, the case 4 is connected to an exhaust mani-
fold 3, as shown in Fig. 7, and the reducing catalyst 5
and the oxidizing catalyst 6 are fitted in the case 4
through holding members 7 and 8. Since the oxidizing
catalyst 6 of the two has to be supplied with secondary
air, secondary air passages 9 and 10 are formed for
both the exhaust manifold 3 and the case 4 so that the
secondary air may be supplied through a not-shown se-
condary air supply tube.
When the secondary oxidizing catalyst 6 is fitted
in the case 4 of the catalyzing system of such struc-
ture, the holding member 8 is wound around the oxi-
dizing catalyst 6. Even with elaborate cares for the
working, therefore, the holding member 8 is frequently
caught by the outlet port (i.e., the downstream exist
of the secondary air passage 10) of the secondary air
so that the oxidizing catalyst 6 cannot be well press-
fitted in the case 4. Another problem is that the
holding force of the oxidizing catalyst 6 will drop.
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It is an object of the present invention to provide a system
which obviates or mitigates at least one of the above-mentioned
disadvantages.
According to an aspect of the present invention there is
provided a catalyzing assembly for reducing noxious components from an
engine exhaust manifold, comprising:
(a) a generally cylindrical housing comprising an integral
extension portion of the exhaust manifold, said housing having an inner wall
surface defining a chamber having an open end and including an integral
annular flange extending radially outwardly therefrom;
(b) a primary reducing catalyst arranged and retained within
said housing chamber via said open end and extending between the inner
wall surface of said housing;
(c) a generally cylindrical case having an inner wall surface
defining a chamber having an open end and including an integral annular
flange extending radially outwardly therefrom;
(d) a secondary oxidizing catalyst arranged and retained
within said case chamber via said open end and extending between the inner
wall surface of said case;
(e) means for connecting said case and housing flanges
together with said case and housing open ends facing each other and with
said case and said housing chambers being arranged coaxially in spaced
relation, thereby to define a space between said primary and secondary
catalysts arranged in tandem; and
(f) means for supplying secondary air to the space between
said catalysts for an oxidation reaction of said secondary catalyst.
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According to another aspect of the present invention there is
provided a catalyst system comprising: a primary reducing catalyst and a
secondary oxidizing catalyst arrayed in tandem just downstream of an
exhaust manifold, said primary catalyst being accommodated in said exhaust
manifold; and a space defined between said primary and secondary catalysts
by extending said exhaust manifold at its primary catalyst holding portion to
said secondary catalyst.
Thanks to these structures, when the secondary oxidizing
catalyst is to be accommodated in the (catalyst) case, its accommodated
portion is positioned at end face of the case so that the holding member is
kept away from contact with the outlet port of the secondary air unlike the
prior art. In the second means, on the
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other hand, the exhaust manifold extended to the oxi-
dizing catalyst 6 performs the function of the spacer
of the catalyzing system of the prior art so that the
secondary air can be well distributed without providing
any spacer separately.
Embodiments of the invention will be described
with reference to the accompanying drawings in which:
Fig. 1 is a section showing one embodiment of the
present invention;
Fig. 2 is a section showing another embodiment of
the present invention;
Fig. 3 is a section taken along line III - III of
Fig. 2;
Fig. 4 is a section showing an essential portion
showing a modification of the embodiment of Fig. 3;
Fig. 5 is a section showing still another embodi-
ment of the present invention;
Fig. 6 is a section taken along line VI - VI of
Fig. 5; and
Fig. 7 is a section showing the catalyzing system
of the prior art.
The present invention will be described in the
following in connection with its one embodiment with
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reference to Fig. 1. As is apparent in comparison with
Fig. 7, the primary reducing catalyst 5 is accommodated
in the exhaust manifold 3. A secondary air supply tube
11 has its leading end inlet port lla opened in the
flanged face between the exhaust manifold 3 and the
case 4. In this embodiment, a spacer 13 is formed
between the reducing catalyst 5 at the side of the
exhaust manifold 3 and the oxidizing catalyst 6 at the
side of the case 4 so that secondary air may be blown
to the oxidizing catalyst 6 from pores 13a which are
formed in the spacer 13. Designated at reference nume-
ral 14 are bolts which fasten the exhaust manifold 3
and the case 4 at the flanged portions.
In the catalyzing system 1 thus constructed, the
primary reducing catalyst 5 can be easily mounted from
the opening at the side of the exhaust manifold 3, and
the secondary oxidizing catalyst 6 can also be easily
mounted from the opening at the side of the case 4.
After these two catalysts 5 and 6 have been mounted,
the spacer 13 is sandwiched, and the flanged portions
are fastened by means of the bolts 14. The secondary
air is introduced into the spacer 13 through the inlet
port lla at the leading end of the secondary air supply
tube 11.
Fig. 2 shows another embodiment of the present
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invention. In this embodiment, the primary catalyst 5
is accommodated in the exhaust manifold 3, and this
holding portion of the manifold 3 is extended to the
secondary catalyst 6 to define a space between the two
catalysts 5 and 6. As a result, this embodiment can
dispense with the spacer 13 which was required by the
embodiment of Fig. 1. In this embodiment, the flanged
portion of the case 4 is extended upward, as shown in
Fig. 3, to open a connecting port 15 for the secondary
air supply tube 11 (as shown in Fig. 1). As shown in
Fig. 4, on the other hand, the flanged portion of the
exhaust manifold 3 may be extended to form the connec-
ting portion 15.
Fig. 5 shows still another embodiment of the pre-
sent invention. In this embodiment, the exhaust mani-
fold 3 is extended toward the secondary catalyst 6, and
the case 4 is extended around the extension of the
manifold 3 to form inbetween an annular passage 16 for
the secondary air (as shown in Fig. 6). This passage
16 is connected at the connecting port of the flanged
portions to the secondary air supply tube 11 (as shown
in Fig. 1). With this structure, the secondary air
supplied from the connecting port 15 is swirled, while
it is passing through the annular passage, so that it
is uniformly supplied to the oxidizing catalyst 6.
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Since the first embodiment of the present inven-
tion provides the catalyzing system having the struc-
ture thus far described, the primary reducing catalyst
and secondary oxidizing catalyst can be easily mounted
from the openings at the sides of the exhaust manifold
and the case, respectively, before the exhaust manifold
and the case are connected for the assembly. Unlike
the prior art, the holding member is neither caught nor
peeled because the two catalysts are not sequentially
inserted from the common opening. In addition to the
above-specified effect, according to the second embodi-
ment, the portion of the exhaust manifold extended to
the oxidizing catalyst performs the function of the
spacer of the catalyzing system of the prior art so
that the secondary air can be sufficiently distributed
without providing any spacer separately.
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