Muffler structure

Details Muffler structure Muffler structure

1999-08-23

2001-02-20

Dang, Khanh (Department: 2837)

Acoustics

Sound-modifying means

Muffler, fluid conducting type

C181S265000, C181S272000

Reexamination Certificate

active

06189650

ABSTRACT:

BACKGROUND OF THE INVENTION
(i) Field of the Invention
The present invention relates to a muffler structure in which at least one pipe is disposed in a muffler.
(ii) Description of the Related Art
A muffler structure has been heretofore known in which an exhaust gas flow path inside a muffler is changed in accordance with an engine operation state in order to reduce back pressure during high-rate rotation of an internal combustion engine.
For example, in a muffler disclosed in Japanese Utility Model Application Laid-Open No.5-42624, as shown in
FIG. 8
, an inner pipe
103
is provided with a pivotably supported valve
105
. In the valve
105
, a pressure receiving portion
105
a
is formed opposite to a downstream end of an inlet pipe
101
, while a closing portion
105
b
is formed opposite to an upstream end of an inner pipe
103
.
In the muffler, when engine exhaust gas has a relatively low pressure, the inner pipe
103
is closed by the closing portion
105
b
of the valve
105
via the biasing force of a spring
108
. Therefore, exhaust gas introduced via the inlet pipe
101
is passed through another inner pipe
104
and exhausted to the outside via an outlet pipe
102
.
On the other hand, when the pressure of the engine exhaust gas is relatively high, the exhaust gas introduced via the inlet pipe
101
exerts force against the pressure receiving portion
105
a
of the valve
105
, and opens the valve
105
against the biasing force of the spring
108
, whereby the closing portion
105
b
of the valve
105
opens the upstream end of the inner pipe
103
. Therefore, the exhaust gas introduced via the inlet pipe
101
passes through the inner pipe
103
in addition to the inner pipe
104
, and the back pressure can be inhibited from rising.
However, when the muffler structure of
FIG. 8
is used, exhaust gas exerts pressure on the pressure receiving portion
105
a
of the valve
105
from a substantially orthogonal direction. As a result, when pulsation is generated in the exhaust gas, a cracking or chattering noise may be generated by the contact of the valve
105
in the downstream end of the inlet pipe
101
and the upstream end of the inner pipe
103
.
Moreover, when the pressure of the exhaust gas is high, the increase of back pressure is prevented by opening the valve
105
to pass the exhaust gas through the inner pipe
103
. However, in some muffler designs, the increase of the back pressure cannot sufficiently be prevented simply by increasing gas path area.
Furthermore, in accordance with the length of the outlet pipe
102
, when the number of revolutions of the engine reaches or exceeds a certain value, sound pressure level rapidly increases by columnar resonance. Such a problem cannot be solved by the muffler structure of FIG.
8
.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a muffler structure which inhibits a valve, opened/closed in accordance with pressure inside a pipe, from chattering.
Another object of the present invention is to prevent back pressure from increasing beyond a desirable magnitude.
A further object of the present invention is to suppress columnar resonance.
To attain these and other objects, according to one aspect of the present invention there is provided a muffler structure in which one or more pipes are disposed in a muffler. The muffler structure is provided with a side hole formed in a side surface of the at least one of these pipes, and a valve for opening or closing the side hole in accordance with a pressure of gas passing through the pipe having the side hole.
In the muffler structure, when engine exhaust gas passes through the pipe provided with the side hole, and exhaust gas pressure is low, the side hole remains closed by the valve. On the other hand, when the pressure of the exhaust gas is high, the valve is pushed open by the pressure, and the side hole is opened. Therefore, the exhaust gas passing through the pipe flows to the outside from the side hole. In this case, different from a case where the side hole is closed, the resistance is reduced, and the back pressure is inhibited from rising.
Furthermore, since a direction in which the exhaust gas flows is substantially parallel with a face of the valve closing the side hole, there is only a small possibility that chattering occurs, even if pulsation is caused in the pressure of the exhaust gas. Therefore, according to the muffler structure, abnormal noise is effectively prevented from being generated by chattering.
According to another aspect of the present invention there is provided a muffler structure in which first and second pipes are arranged in a muffler, and exhaust gas passes through the second pipe via the first pipe. The muffler structure is provided with a first side hole formed in a side surface of the first pipe, a second side hole formed in a side surface of the second pipe, and a valve for opening or closing both the first and second side holes in accordance with a pressure of the gas passing through the first pipe.
In such a muffler structure, when the pressure of engine exhaust gas is low, both the first and second side holes are closed by the valve. Therefore, for example, when the second pipe has an introductory inlet other than the second side hole, the exhaust gas flows out of an opening on the downstream side of the first pipe, then enters the second pipe via the introductory inlet. Moreover, when the second pipe has no introductory inlet except the second side hole, the exhaust gas flows out of the opening on the downstream side of the first pipe, then takes another route without passing through the second pipe.
On the other hand, when the pressure of the engine exhaust gas is high, the first and second side holes are both opened by the valve. Therefore, when the exhaust gas passes through the first and second pipes, it goes out of the first side hole before reaching the opening on the downstream side of the first pipe, then enters the second pipe via the second side hole. Specifically, a new route which can be taken by the exhaust gas is formed.
Therefore, according to the muffler structure, when the pressure of the exhaust gas is increased, a new route through which the exhaust gas can pass is formed, so that when the exhaust gas passes through the muffler, the resistance is remarkably reduced, and the rising of the back pressure can sufficiently be inhibited.
Here, it is preferred that the first side hole should be provided in the vicinity of the upstream end of the first pipe, while the second side hole should be provided in the vicinity of the downstream end of the second pipe. In this case, for the newly formed route, since a passing distance between the pipes is shortened, the rising of the back pressure can further effectively be suppressed.
Moreover, an outlet pipe may be used as the second pipe. In general, the outlet pipe has a problem, in accordance with its length, that when the number of revolutions of the engine reaches a certain value or more, the sound pressure level is abruptly raised by columnar resonance. In the present invention, however, when the number of revolutions of the engine is increased, the pressure of the exhaust gas is raised, and a new route through which the exhaust gas can pass is formed. Therefore, the above-mentioned problem can be prevented from arising.
In this case, the first and second pipes are preferably inlet and outlet pipes, respectively. For example, the first and second pipes may be upstream and downstream inner pipes, respectively. In this case, however, the new route is formed between the inner pipes. On the other hand, when the first and second pipes are inlet and outlet pipes, respectively, the new route is formed between the inlet and outlet pipes. Therefore, immediately after the exhaust gas is introduced into the muffler, it is exhausted to the outside of the muffler. The rising of the back pressure can effectively be suppressed further.
Additionally, in the present invention, when the pipe is disposed in the muffler, it may be disposed entirely or partly in the

Affiliated with

Also associated with

Rating

Muffler structure does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Muffler structure, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Muffler structure will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2576835