Metal working – Method of mechanical manufacture – Muffler – manifold or exhaust pipe making
Reexamination Certificate
1999-07-30
2001-05-01
Dang, Khanh (Department: 2837)
Metal working
Method of mechanical manufacture
Muffler, manifold or exhaust pipe making
C181S248000
Reexamination Certificate
active
06223434
ABSTRACT:
This invention relates to a muffler for an internal combustion engine, and also relates to a method of producing the muffler.
BACKGROUND ART
There is known one conventional muffler (particularly sub-muffler) for an internal combustion engine as shown in
FIG. 11
, in which an outer pipe
102
is mounted around an outer periphery of an inner pipe
100
(which forms an exhaust gas passage), with a space
101
formed therebetween, and one end portion
103
of the outer pipe is fixedly secured to the inner pipe
100
through a buffer member
105
such as a wire mesh, and the other end portion
104
thereof is fixedly secured to the inner pipe
100
.
In one known method of producing such a muffler, the one end portion
103
of the outer pipe
102
is first reduced in diameter by a press die
106
as indicated by broken lines in
FIG. 12A
, and then the inner pipe
100
, having the buffer member
105
fitted on one end portion thereof, is inserted into the outer pipe
102
as shown in
FIG. 12B
, and the buffer member
105
is disposed at the inner peripheral surface of the contracted one end portion
103
. Then, as shown in
FIG. 12C
, the other end portion
104
of the outer pipe
102
is reduced in diameter into a tapering shape by a press die
107
, and is fixedly secured to the inner pipe
100
.
In the above muffler, generally, the other end portion
108
of the inner pipe
100
remote from the buffer member
105
projects from the contracted other end portion
104
of the outer pipe
102
, and serves as a welding portion, and the muffler is connected at this welding portion
108
to an exhaust pipe by welding.
In the above conventional production method, however, that portion of the outer pipe
102
, having the buffer member
105
, is first reduced in diameter, thereby connecting the inner and outer pipes
100
and
102
together, and therefore during the contraction of the end portion
104
of the outer pipe remote from the buffer member
105
, which is effected thereafter, there is a possibility that the inner pipe
100
and the outer pipe
102
are displaced relative to each other in the axial direction.
Namely, the reasons for this are that the strength of frictional connection between the outer pipe
102
and the buffer member
105
is low, and that the outer pipe
102
is pushed in the axial direction by the press die
107
.
If the inner and outer pipes are thus displaced relative to each other, a welding area L of the welding portion
108
to be welded to the exhaust pipe is reduced, which results in a problem that it becomes difficult to effect the welding.
Further, the muffler, in which the outer pipe
102
is reduced in diameter by the press die, has a problem that the buffer member
105
can not be compressed uniformly over the entire periphery thereof, and besides in the construction in which the opposite end portions of the outer pipe
102
are reduced in diameter by the press die, the material of the outer pipe can be buckled, and therefore the limit of the contraction rate is about
20
%, which leads to a problem that there can not be produced the muffler in which the volume of the space, formed between the inner and outer pipes, is increased.
DISCLOSURE OF THE INVENTION
It is therefore an object of this invention to provide a muffler which solves the above problems, and also to provide a method of producing this muffler.
In order to solve the above problems, the first invention, recited in claim
1
, provides a muffler wherein one end portion of an outer pipe, which is mounted around an outer periphery of an inner pipe, with a space formed therebetween, is reduced in diameter to be fixedly secured to the inner pipe, and the other end portion of the outer pipe is reduced in diameter, thereby holding a buffer member between the other end portion of the outer pipe and the inner pipe; CHARACTERIZED in that the reduction of the diameter of at least that end portion, having the buffer member, is effected by spinning.
In this invention, by the spinning processing applied to the outer pipe, the buffer member is compressed uniformly over an entire periphery thereof.
The second invention, recited in claim
2
, provides a method of producing a muffler CHARACTERIZED in that the method comprises a first step of holding an inner pipe, having a buffer member fitted on one end portion thereof, within an outer pipe in such a manner that a predetermined gap is formed between the inner and outer pipes; a second step of reducing a diameter of the other end portion of the outer pipe remote from the buffer member, thereby fixedly securing the other end portion to the other end portion of the inner pipe; and a third step of subsequently applying a spinning processing to one end portion of the outer pipe, thereby reducing a diameter of the one end portion until the one end portion is brought into contact with the buffer member, and further radially compresses the buffer member.
In this invention, before that portion, having the buffer member, is reduced in diameter, that portion remote from the buffer member, is reduced in diameter, with the inner and outer pipes held in their respective predetermined positions, thereby fixedly securing the inner and outer pipes to each other, and therefore a welding portion can be accurately formed at this fixed side. And besides, when that portion of the outer pipe, having the buffer member, is to be reduced in diameter by spinning after this fixing operation, the inner and outer pipes can be prevented from being displaced with respect to each other. Furthermore, the reduction of the diameter of that portion of the outer pipe having the buffer member, is effected by the spinning processing in which the outer pipe is rotated, and therefore the outer pipe can be reduced in diameter uniformly over the entire periphery thereof, and also the buffer member is compressed uniformly over the entire periphery thereof.
The third invention, recited in claim
3
, is directed to the muffler-producing method, in which the reduction of the diameter of the outer pipe in the second step of the second invention is also effected by spinning processing.
In this invention, an axial load as produced with the use of a die press is not applied to the outer pipe, and the more accurate welding portion can be formed. And besides, the opposite end portions of the outer pipe are both reduced in diameter by spinning processing, and therefore the material thereof will not be buckled at the opposite end portions.
The fourth invention, recited in claim
4
, is directed to the muffler-producing method, in which the reduction of the diameter of the outer pipe in the third step of the second or the third invention is effected in such a manner that a mandrel is inserted into one end portion of the outer pipe so as to limit the amount of reduction of the diameter of the outer pipe.
In this invention, the amount of reduction of the diameter of the outer pipe is limited, and therefore the accurate contracted configuration of the outer pipe, as well as the amount of compression of the buffer member, can be obtained easily.
In the fifth invention recited in claim
5
, the reduction of the diameter of the outer pipe in the third step is effected in such a manner that a mandrel is inserted into one end portion of the outer pipe so as to limit the amount of reduction of the diameter of the outer pipe and that the mandrel, having a diameter substantially equal to an inner diameter of the inner pipe, is inserted into one end portion of the inner pipe.
In this invention, in addition to the effect of the fourth invention, the inner and outer pipes can be prevented from being crushed and deformed during the reduction of the diameter of the outer pipe.
REFERENCES:
patent: 4993513 (1991-02-01), Inoue et al.
patent: 5100047 (1992-03-01), Nakagawa et al.
patent: 5293743 (1994-03-01), Usleman et al.
patent: 51-028572 (1976-03-01), None
patent: 57-206538 (1982-12-01), None
patent: 2-19820 (1990-02-01), None
patent: 2-137516 (1990-11-01), None
patent: 3-146617 (1991-06-01), None
patent: 4-190919 (1992-0
Dang Khanh
Pillsbury & Winthrop LLP
Sango Co. Ltd.
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