U.S. patent application number 11/452309 was filed with the patent office on 2006-12-21 for method for manufacturing concentric double exhaust pipe for internal combustion engine.
Invention is credited to Yasunori Iwamoto, Masaharu Kuroda, Toshio Murata, Yasuhiro Nobata.
Application Number | 20060283002 11/452309 |
Document ID | / |
Family ID | 37571901 |
Filed Date | 2006-12-21 |
United States Patent
Application |
20060283002 |
Kind Code |
A1 |
Kuroda; Masaharu ; et
al. |
December 21, 2006 |
Method for manufacturing concentric double exhaust pipe for
internal combustion engine
Abstract
A concentric double exhaust pipe for an internal combustion
engine includes an outer pipe 10 and an inner pipe 20. The outer
pipe 10 and inner pipe 20 have basal ends fixed to each other. A
seal member 30 arranged between the two pipes 10 and 20 enable
sliding of distal ends of the outer pipe 10 and the inner pipe 20
during thermal expansion. When manufacturing the concentric double
exhaust pipe, the outer pipe 10 is compressed after attaching the
seal member 30 between an inner surface of the outer pipe 10 and an
outer surface of the inner pipe 20 so as to compress the seal
member 30 to a predetermined outer diameter.
Inventors: |
Kuroda; Masaharu;
(Toyota-shi, JP) ; Nobata; Yasuhiro; (Toyota-shi,
JP) ; Murata; Toshio; (Toyota-shi, JP) ;
Iwamoto; Yasunori; (Toyota-shi, JP) |
Correspondence
Address: |
KENYON & KENYON LLP
1500 K STREET N.W.
SUITE 700
WASHINGTON
DC
20005
US
|
Family ID: |
37571901 |
Appl. No.: |
11/452309 |
Filed: |
June 14, 2006 |
Current U.S.
Class: |
29/508 ;
29/888.01 |
Current CPC
Class: |
Y10T 29/49231 20150115;
B21D 39/04 20130101; F01N 2470/24 20130101; F01N 2470/06 20130101;
Y10T 29/49913 20150115; F01N 2470/26 20130101 |
Class at
Publication: |
029/508 ;
029/888.01 |
International
Class: |
B21D 39/00 20060101
B21D039/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 16, 2005 |
JP |
2005-176833 |
Claims
1. A method for manufacturing a concentric double exhaust pipe for
an internal combustion engine, the exhaust pipe including an outer
pipe and inner pipe having basal ends fixed to each other, with the
inner pipe arranged in the outer pipe, and a seal member arranged
between the outer pipe and the inner pipe and enabling relative
movement of distal ends of the outer pipe and the inner pipe during
thermal expansion, the method comprising: compressing the outer
pipe after attaching the seal member between an inner surface of
the outer pipe and an outer surface of the inner pipe so as to
compress the seal member to a predetermined outer diameter.
2. The method for manufacturing a concentric double exhaust pipe
for an internal combustion engine according to claim 1, wherein the
outer pipe is compressed through a spinning process.
3. The method for manufacturing a concentric double exhaust pipe
for an internal combustion engine according to claim 1, wherein the
outer pipe is compressed through a pressing process.
4. The method for manufacturing a concentric double exhaust pipe
for an internal combustion engine according to claim 1, further
comprising: measuring thickness of the seal member when attached to
the outer surface of the inner pipe and adjusting compression level
of the outer pipe based on the measurement.
5. The method for manufacturing a concentric double exhaust pipe
for an internal combustion engine according to claim 4, further
comprising: calculating a target diameter, which is a compression
target for the outer pipe, based on the outer diameter and
thickness of the outer pipe and a target thickness, which is a
compression target, for the seal member.
6. The method for manufacturing a concentric double exhaust pipe
for an internal combustion engine according to claim 1, wherein the
seal member has an outer diameter measured when attached to the
outer surface of the inner pipe that is set to be smaller than an
inner diameter of the outer pipe.
7. The method for manufacturing a concentric double exhaust pipe
for an internal combustion engine according to claim 1, wherein the
seal member is attached to the outer surface of the inner pipe in a
state in which the seal member is widened in the radial
direction.
8. The method for manufacturing a concentric double exhaust pipe
for an internal combustion engine according to claim 1, further
comprising: fixing a mold inside the inner pipe and pressing a
roller against an outer surface of the outer pipe while rotating
the outer pipe together with the inner pipe.
9. The method for manufacturing a concentric double exhaust pipe
for an internal combustion engine according to claim 8, further
comprising: adjusting moving velocity of the roller in the axial
direction of the outer pipe and feed amount of the roller in the
radial direction of the outer pipe to compress the outer pipe.
10. The method for manufacturing a concentric double exhaust pipe
for an internal combustion engine according to claim 1, wherein the
seal member is a wire mesh formed from fine metal wires.
11. The method for manufacturing a concentric double exhaust pipe
for an internal combustion engine according to claim 1, wherein the
outer pipe is formed from a steel metal.
12. A method for manufacturing a concentric double exhaust pipe for
an internal combustion engine, the exhaust pipe including an outer
pipe and inner pipe having basal ends fixed to each other, with the
inner pipe arranged in the outer pipe, and a seal member arranged
between the outer pipe and the inner pipe and enabling relative
movement of distal ends of the outer pipe and the inner pipe during
thermal expansion, the method comprising: performing a diameter
enlargement process on the inner pipe after attaching the seal
member between an inner surface of the outer pipe and an outer
surface of the inner pipe so as to compress the seal member to a
predetermined outer diameter.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a method for manufacturing
a concentric double exhaust pipe for an internal combustion
engine.
[0002] Japanese Laid-Open Patent Publication No. 6-336921 describes
a concentric double exhaust pipe, which is formed by arranging an
inner pipe inside an outer pipe, used as an exhaust passage for an
internal combustion engine. In the concentric double exhaust pipe,
the two pipes have basal ends that are fixed to each other through
welding or the like and distal ends that are free to tolerate
thermal deformation in the axial direction of the pipes. More
specifically, as shown in FIG. 3, after fixing the basal ends,
which are not shown in the drawings, of an outer pipe 1 and an
inner pipe 20 to each other, a wire mesh 3 is attached in a
compressed state between the inner surface of the outer pipe 1 and
the outer surface of the inner pipe 20 at the distal ends. This
fixes the basal ends of the outer pipe 1 and inner pipe 20 and
seals the distal ends of the outer pipe 1 and inner pipe 20 in a
manner enabling sliding therebetween when thermal expansion
occurs.
[0003] Normally, dimensional tolerance is provided for the inner
diameter of the outer pipe 1 and the outer diameter of the inner
pipe 20. This produces differences in the gap between the inner
surface of the outer pipe 1 and the outer surface of the inner pipe
20. Therefore, if the gap between the inner surface of the outer
pipe 1 and the outer surface of the inner pipe 20 is larger than
the specified value for the thickness of wire mesh 3, the
compression level of the wire mesh becomes too small. This causes
the contact pressure of the wire mesh 3 against the outer pipe 1
and the inner pipe 20 to be less than the designed value. On the
other hand, if the gap between the inner surface of the outer pipe
1 and the outer surface of the inner pipe 20 is smaller than the
specified value for the thickness of the wire mesh 3, the
compression level of the wire mesh becomes too high. This causes
the contact pressure of the wire mesh 3 against the outer pipe 1
and the inner pipe 20 to be greater than the designed value.
Further, when the gap is too small in relation with thickness of
the wire mesh 3, the wire mesh 3 may become crimped. As a result,
the sliding and sealing characteristics may not be
satisfactory.
[0004] Such a problem occurs when manufacturing a concentric double
exhaust pipes for an internal combustion engine enabling sliding
during thermal expansion of the distal ends of the outer pipe and
inner pipe by fixing the basal ends of the outer pipe and inner
pipe and attaching a seal member between the inner surface of the
outer pipe and the outer surface of the inner pipe.
SUMMARY OF THE INVENTION
[0005] It is an object of the present invention to provide a
manufacturing method for a concentric double exhaust pipe for an
internal combustion engine that facilitates attachment of a seal
member between an outer pipe and an inner pipe and facilitates
control of contact pressure of a seal member against an outer pipe
and an inner pipe.
[0006] One aspect of the present invention is a concentric double
exhaust pipe for an internal combustion engine including an outer
pipe and inner pipe having basal ends fixed to each other. A seal
member is arranged between the outer pipe and the inner pipe and
enables relative movement of distal ends of the outer pipe and the
inner pipe during thermal expansion. A method for manufacturing the
concentric double exhaust pipe includes compressing the outer pipe
after attaching the seal member between an inner surface of the
outer pipe and an outer surface of the inner pipe so as to compress
the seal member to a predetermined outer diameter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a cross-sectional diagram of a concentric double
exhaust pipe according to a preferred embodiment of the present
invention prior to compression;
[0008] FIG. 2 is a cross-sectional diagram of the concentric double
exhaust pipe subsequent to compression; and
[0009] FIG. 3 is a cross-sectional diagram of a concentric double
exhaust pipe in the prior art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0010] A process for manufacturing a catalytic converter arranged
in an exhaust passage of an internal combustion engine according to
a preferred embodiment of the present invention will now be
described with reference to FIGS. 1 and 2.
[0011] FIG. 1 is a cross-sectional diagram of a concentric double
exhaust pipe for the catalytic converter showing a state prior to
compression.
[0012] As shown in FIG. 1, the concentric double exhaust pipe of
the catalytic converter includes an outer pipe 10, an inner pipe
20, and a wire mesh 30. The outer pipe 10 is formed from a steel
metal. The outer pipe 10 has an outer diameter and an inner
diameter, which are constant.
[0013] The inner pipe 20 includes a constant diameter portion 22,
an enlarged diameter portion 24, and an end portion 24e. The
constant diameter portion 22 is concentric with the outer pipe 10.
The outer diameter and inner diameter of the inner pipe 20 are each
constant along the constant diameter portion 22. The enlarged
diameter portion 24 has an end located at the upstream side of the
exhaust and is welded to the outer surface of the constant diameter
portion 22. The outer diameter and inner diameter of the inner pipe
20 at the enlarged diameter portion 24 gradually increases in the
downstream direction of the exhaust. The end portion 24e is located
at the downstream side of the enlarged diameter portion. The outer
diameter and inner diameter of the inner pipe 20 at the end portion
24e are each constant.
[0014] The outer pipe 10 and the inner pipe 20 have basal portions
at the upstream side of the exhaust that are welded to a fastening
portion, which is not shown in the drawing. A wire mesh 30, which
functions as a seal member, is arranged between the inner surface
of the outer pipe 10 and the outer surface of the end portion 24e
of the inner pipe 20. The wire mesh 30 is formed from fine metal
wires. The wire mesh 30 seals the gap between the inner surface of
the outer pipe 10 and the outer surface of the end portion 24e of
the inner pipe 20. Further, the wire mesh 30 enables sliding of the
two pipes 10 and 20 in the axial direction when the outer pipe 10
and the inner pipe 20 thermally deform.
[0015] With reference to FIGS. 1 and 2, the manufacturing
procedures for the concentric double exhaust pipe when the wire
mesh 30, which is attached to the end portion 24e of the inner pipe
20, has a diameter d3o smaller than an inner diameter d1i of the
outer pipe 10, that is, when a gap exists between the inner surface
of the outer pipe 10 and the outer surface of the wire mesh 30 will
now be discussed.
[0016] The concentric double exhaust pipe is manufactured in the
following order from (1) to (10).
[0017] (1) As shown in FIG. 1, the basal portion at the exhaust
upstream side of the enlarged diameter portion 24 is welded and
connected to the distal portion at the exhaust downstream side of
the constant diameter portion 22 to assemble the inner pipe 20.
[0018] (2) The outer pipe 10 is arranged concentrically with the
inner pipe 20, and the basal portions at the exhaust upstream side
of the outer pipe 10 and the inner pipe 20 are respectively welded
to the fastening portion (not shown).
[0019] (3) The inner diameter d1i and outer diameter d1o of the
outer pipe 10 are each measured at a section corresponding to the
attachment position of the wire mesh 30. Then, the thickness
.DELTA.d1 of the outer pipe 10 is calculated from the measured
inner diameter d1i and the outer diameter d1o.
[0020] (4) The outer diameter d2o of the end portion 24e is
measured.
[0021] (5) The wire mesh 30 is widened in the radial direction and
attached to the outer surface of the end portion 24e.
[0022] (6) The outer diameter d3o of the wire mesh 30 in a state
attached to the end portion 24e is measured.
[0023] (7) The thickness .DELTA.d3 of the wire mesh 30 is
calculated from the outer diameter d3o of the wire mesh 30 and the
outer diameter d2o of the end portion 24e.
[0024] (8) A target thickness .DELTA.d3t, which is a compression
target for the wire mesh 30, is calculated from the thickness
.DELTA.d3 of the wire mesh 30.
[0025] (9) A target outer diameter d1ot, which is a compression
target for the outer pipe 10, is calculated from the outer diameter
d1o and thickness .DELTA.d1 of the outer pipe 10 and thickness
.DELTA.d3 and target thickness .DELTA.d3t of the wire mesh 30.
[0026] (10) As shown in FIG. 2, a spinning process is performed to
compress the outer pipe 10 until the outer diameter d1o of the
outer pipe 10 becomes equal to the target outer diameter d1ot. More
specifically, a mold (not shown) is fixed to the end portion 24e of
the inner pipe 20. In this state, a roller (not shown) is pressed
against the outer surface of the outer pipe 10 while rotating the
outer pipe 10 together with the inner pipe 20. Further, the moving
velocity of the roller in the axial direction and the feed amount
of the roller in the radial direction are adjusted. The roller is
pressed against the outer surface of the outer pipe 10 to compress
the outer pipe 10 and the wire mesh 30 until the outer diameter d1o
of the outer pipe 10 becomes equal to the outer pipe target outer
diameter d1ot.
[0027] The preferred embodiment has the advantages described
below.
[0028] (1) In the preferred embodiment, after the wire mesh 30 is
attached between the inner surface of the outer pipe 10 and the
outer surface of the inner pipe 20, the outer pipe 10 is compressed
so as to compress the wire mesh 30 to the predetermined outer
diameter. In this case, during the attachment of the wire mesh 30,
the gap between the inner surface of the outer pipe 10 and the
outer surface of the inner pipe 20 may be enlarged. This
facilitates the attachment of the wire mesh 30 between the inner
surface of the outer pipe 10 and the outer surface of the inner
pipe 20. Further, the compression of the outer pipe 10 absorbs the
dimensional tolerances of the outer pipe 10, the inner pipe 20, and
the wire mesh 30. This facilitates control of the contact pressure
of the wire mesh 30 against the outer pipe 10 and the inner pipe
20.
[0029] (2) The spinning process compresses the outer pipe 10. The
spinning process is optimal for processes that require a high
dimensional accuracy. The compression of the outer pipe 10 through
spinning finely adjusts the compression level of the wire mesh 30.
Thus, the sliding and sealing characteristics obtained by the wire
mesh 30 may be finely controlled.
[0030] (3) The thickness .DELTA.d3 of the wire mesh 30 when
attached to the end portion 24e of the inner pipe 20 is measured,
and the compression level of the outer pipe 10 is adjusted based on
the measurement result. In this case, the compression force applied
to the wire mesh 30 by the outer pipe 10 is accurately adjusted.
Thus, the sliding and sealing characteristics obtained by the wire
mesh 30 are improved.
[0031] (4) Due to the requirement for high heat resistance, the
wire mesh 30 is often used as a seal member in a concentric double
exhaust pipe for an internal combustion engine. However, the
elasticity of the wire mesh 30 is not that high. It is thus
difficult to adjust the contact pressure of the wire mesh 30
against the outer pipe 10 and the inner pipe 20 to a predetermined
value. Further, the wire mesh 30 may be crimped when the wire mesh
30 is attached between the outer pipe 10 and the inner pipe 20.
[0032] In the preferred embodiment, even if the wire mesh 30, which
is formed from fine metal wires, is used as the seal member, the
arrangement of the seal member in the gap between the outer pipe 10
and the inner pipe 20 is facilitated. Further, the contact pressure
of the seal member against the outer pipe 10 and the inner pipe 20
is controlled to a predetermined value.
[0033] The above embodiment may be modified as described below.
[0034] In the preferred embodiment, the wire mesh 30 is used as the
seal member. However, a seal member formed from, for example, a
heat resistant resin may also be used.
[0035] In the preferred embodiment, the measurement of the outer
diameter d1o and the inner diameter d1i of the outer pipe 10 may be
eliminated. Further, the measurement of the outer diameter d3o of
the wire mesh 30 and the outer diameter d2o of the inner pipe 20
may be eliminated. This would lower the accuracy of the compression
level of the outer pipe 10 and the wire mesh 30. However, the
attachment of the wire mesh 30 would be facilitated, and the
dimensional tolerances of the outer pipe 10, the inner pipe 20, and
the wire mesh 30 would be absorbed.
[0036] In the preferred embodiment, the spinning process for
compressing the outer pipe 10 and the wire mesh 30 may be changed
to other processes, such as a pressing process.
[0037] The present invention is embodied in a catalytic converter
for eliminating harmful substances from exhaust gas. However, the
present invention may be embodied in a muffler that is arranged in
an exhaust passage. In other words, the present invention may be
applied to any concentric double exhaust pipe having an outer pipe
and inner pipe with fixed basal ends and distal ends allowed to
slide.
[0038] In the preferred embodiment, instead of compressing the
outer pipe 10 after attaching the wire mesh 30 between the inner
surface of the outer pipe 10 and the outer surface of the inner
pipe 20, the inner pipe 20 may undergo a diameter enlargement
process to compress the wire mesh 30. Such processing would be more
difficult than the compression of the outer pipe 10. However, this
would facilitate the attachment of the wire mesh 30 and absorb the
dimensional tolerances of the outer pipe 10, the inner pipe 20, and
the wire mesh 30. Further, the contact pressure of the wire mesh 30
against the outer pipe 10 and the inner pipe 20 may be
controlled.
* * * * *