Engine muffler

Details Engine muffler Engine muffler

1999-04-19

2001-06-26

Walberg, Teresa (Department: 3742)

Power plants

Internal combustion engine with treatment or handling of...

By means producing a chemical reaction of a component of the...

C060S302000, C060S308000

Reexamination Certificate

active

06250075

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to improvements in an engine muffler for a small-sized engine, for example, of a brush cutter or a chain saw.
2. Description of the Related Art
As shown in
FIG. 7
, a conventional muffler used for a small-sized engine comprises a first expansion chamber
2
for exhaust gas which includes an exhaust gas inlet
1
to be connected to an exhaust port of the engine, a second expansion chamber
4
which includes an exhaust gas outlet
3
, and an exhaust gas purifier
5
disposed between the first expansion chamber
2
and the second expansion chamber
4
in which a catalyst for purifying exhaust gas is coated on a stainless-steel base body including many pores, for example, a honeycomb stainless-steel base body.
In such an engine muffler containing an exhaust gas purifier, as already known, the distance between an exhaust gas inlet and the exhaust gas purifier of a first expansion chamber is designed to be shorter, so that an unburnt gas is completely combusted in the first expansion chamber heated by exhaust gas, and thus substances such as carbon monoxide and nitrogen oxides contained in exhaust gas are decreased.
However, in an engine muffler used for a small-sized engine, the distance between an exhaust gas inlet and an exhaust gas purifier is extremely difficult to make longer.
With regard to the conventional muffler shown in
FIG. 7
, in order to make as long as possible the distance between the exhaust gas inlet
1
and the exhaust gas purifier
5
, and the distance between the exhaust gas purifier
5
and the exhaust gas outlet
3
and also make it compact, the muffler is constructed such that the exhaust gas which has entered at the exhaust gas inlet
1
disposed in the upper part of the first expansion chamber
2
, passes through the exhaust gas purifier
5
disposed in the lower part of the adjoining first expansion chamber
2
and second expansion chamber
4
, and then is discharged from the exhaust gas outlet
3
disposed in the upper part of the second expansion chamber
4
. In the muffler according to this construction, the distance between the exhaust gas inlet
1
of the first expansion chamber
2
and the exhaust gas purifier
5
and the distance between the exhaust gas purifier
5
and the exhaust gas outlet
3
of the second expansion chamber
4
are designed to be as long as possible. However, the intended effect of purifying exhaust gas could not be sufficiently produced.
For the purpose of solving this problem, as shown in
FIG. 8
, a muffler has been developed which comprises a first expansion chamber
2
for exhaust gas which includes an exhaust gas inlet
1
to be connected to an exhaust port of an engine, a second expansion chamber
4
which includes an exhaust gas outlet
3
, a concave exhaust gas receiving member
6
which has a plurality of vent holes
6
b
passing through a concave surface
6
a
thereof, the exhaust gas receiving member
6
being disposed in the first expansion chamber
2
such that the concave surface
6
a
faces the exhaust gas inlet
1
, and an exhaust gas purifier
5
in which a catalyst for purifying exhaust gas is coated on a stainless-steel base body including many pores, for example, a honeycomb stainless-steel base body, the exhaust gas purifier
5
being disposed between the first expansion chamber
2
and the second expansion chamber
4
.
In the conventional improved muffler shown in
FIG. 8
, the concave exhaust gas receiving member
6
which has the plurality of vent holes
6
b
passing through the concave surface
6
a
is disposed in the first expansion chamber
2
such that the concave surface
6
a
faces the exhaust gas inlet
1
, so that the concave exhaust gas receiving member
6
produces the effect of noise reduction. In addition, the complete combustion of unburnt gas is conducted by the heat of the concave exhaust gas receiving member
6
which has been heated by exhaust gas, so that the emission of harmful gases such as carbon monoxide and nitrogen oxides contained in exhaust gas can be decreased. However, even in the muffler according to this construction, the intended effect of purifying exhaust gas of harmful substances could not be sufficiently produced.
SUMMARY OF THE INVENTION
In consideration of the aforementioned problems, it is an object of the present invention to provide an engine muffler having a greater effect of purifying exhaust gas of harmful substances, which is capable of decreasing more the emission quantity of harmful substances such as carbon monoxide and nitrogen oxides contained in exhaust gas by improving the conventional muffler shown in FIG.
8
.
The engine muffler according to a first aspect of the present invention comprises a first expansion chamber
12
for exhaust gas which includes an exhaust gas inlet
11
to be connected to an exhaust port of an engine; a second expansion chamber
14
which includes an exhaust gas outlet
13
; a first exhaust gas purifier
16
in which a catalyst
16
c
for purifying exhaust gas is coated on at least a concave surface
16
a
of a concave base body which has a plurality of vent holes
16
b
passing through the concave surface
16
a
, the first exhaust gas purifier
16
being disposed in the first expansion chamber
12
such that the concave surface
16
a
faces the exhaust gas inlet
11
; and at least one second exhaust gas purifier
15
in which a catalyst for purifying exhaust gas is coated on a base body including many pores, the second exhaust gas purifier
15
being disposed between the first expansion chamber
12
and the second expansion chamber
14
.
The engine muffler according to a second aspect of the present invention comprises a first expansion chamber
12
for exhaust gas which includes an exhaust gas inlet
11
to be connected to an exhaust port of an engine; a third expansion chamber
19
which includes an exhaust gas outlet
13
; a second expansion chamber
14
which is disposed between the first expansion chamber
12
including the exhaust gas inlet
11
and the third expansion chamber
19
including the exhaust gas outlet
13
; a first exhaust gas purifier
16
in which a catalyst
16
c
for purifying exhaust gas is coated on at least a concave surface
16
a
of a concave base body which has a plurality of vent holes
16
b
passing through the concave surface
16
a
, the first exhaust gas purifier
16
being disposed in the first expansion chamber
12
such that the concave surface
16
a
faces the exhaust gas inlet
11
; at least one second exhaust gas purifier
15
in which a catalyst for purifying exhaust gas is coated on a base body including many pores, the second exhaust gas purifier
15
being disposed between the first expansion chamber
12
and the second expansion chamber
14
; and a third exhaust gas purifier
20
in which a catalyst for purifying exhaust gas is coated on a base body including many pores, the third exhaust gas purifier
20
being disposed between the second expansion chamber
14
and the third expansion chamber
19
.
The engine muffler according to a third aspect of the present invention comprises a first expansion chamber
12
for exhaust gas which includes an exhaust gas inlet
11
to be connected to an exhaust port of an engine; a second expansion chamber
14
which includes an exhaust gas outlet
13
; a first exhaust gas purifier
16
in which a catalyst for purifying exhaust gas is coated on at least a concave surface
16
a
of a concave base body which has a plurality of vent holes
16
b
passing through the concave surface
16
a
, the first exhaust gas purifier
16
being disposed in the first expansion chamber
12
such that the concave surface
16
a
faces the exhaust gas inlet
11
; at least one second exhaust gas purifier
15
in which a catalyst for purifying exhaust gas is coated on a base body including many pores, the second exhaust gas purifier
15
being disposed between the first expansion chamber
12
and the second expansion chamber
14
; and a wire net
21
coated with a catalyst for purifying exhaust g

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