U.S. patent application number 12/078131 was filed with the patent office on 2009-01-15 for engine exhaust structure.
This patent application is currently assigned to Kokusan Parts Industry Co., Ltd.. Invention is credited to Yoshitaka Abe, Tomoji Mashio.
Application Number | 20090013679 12/078131 |
Document ID | / |
Family ID | 39912236 |
Filed Date | 2009-01-15 |
United States Patent
Application |
20090013679 |
Kind Code |
A1 |
Abe; Yoshitaka ; et
al. |
January 15, 2009 |
Engine exhaust structure
Abstract
A temperature regulating material 31 for regulating a
temperature of an exhaust manifold 11 is provided such that
individual parts of the exhaust manifold 11 are uniformed in
temperature. Heat transfer materials 31A with high thermal
conductivity are layered as the temperature regulating material 31
on a cover member 25 at an area corresponding to a high-temperature
area HT of the exhaust manifold 11. Heat shield materials 31B are
layered as the temperature regulating material 31 on the cover
member 25 at an area corresponding to the low-temperature area LT
of the exhaust manifold 11. A heat dissipation material 31C as the
temperature regulating material 31 coats an outer surface of the
area of the cover member 25 corresponding to the high-temperature
area of the exhaust manifold 11.
Inventors: |
Abe; Yoshitaka; (Osaka,
JP) ; Mashio; Tomoji; (Maebashi-shi, JP) |
Correspondence
Address: |
Edwards Angell Palmer &Dodge LLP
P. O. Box 55874
Boston
MA
02205
US
|
Assignee: |
Kokusan Parts Industry Co.,
Ltd.
Osaka
JP
|
Family ID: |
39912236 |
Appl. No.: |
12/078131 |
Filed: |
March 27, 2008 |
Current U.S.
Class: |
60/321 ;
60/323 |
Current CPC
Class: |
F01N 13/1872 20130101;
F01N 13/102 20130101; F01N 13/18 20130101 |
Class at
Publication: |
60/321 ;
60/323 |
International
Class: |
F01N 7/10 20060101
F01N007/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 27, 2007 |
JP |
2007-080513 |
Claims
1. An engine exhaust structure provided with a temperature
regulating material for regulating a temperature of an exhaust
manifold such that individual parts of the exhaust manifold are
uniformed in temperature.
2. The engine exhaust structure according to claim 1, wherein a
cover member is provided to cover the exhaust manifold, and heat
transfer materials with high thermal conductivity are layered as
the temperature regulating material on the cover member at an area
corresponding to a high-temperature area of the exhaust
manifold.
3. The engine exhaust structure according to claim 1, wherein a
cover member is provided to cover the exhaust manifold, and heat
shield materials are layered as the temperature regulating material
on the cover member at an area corresponding to a low-temperature
area of the exhaust manifold.
4. The engine exhaust structure according to claim 1, wherein a
cover member is provided to cover the exhaust manifold, and
temperature regulating materials are layered as the temperature
regulating material on the cover member, an area of each of the
temperature regulating materials corresponding to the
high-temperature area of the exhaust manifold being made higher in
thermal conductivity than an area of each of the temperature
regulating materials corresponding to the low-temperature area of
the exhaust manifold.
5. The engine exhaust structure according to claim 1, wherein a
cover member is provided to the exhaust manifold and a heat
dissipation material as the temperature regulating material coats
an outer surface of the area of the cover member corresponding to
the high-temperature area of the exhaust manifold.
6. The engine exhaust structure according to claim 1, wherein a
cover is provided to cover the exhaust manifold, and heat transfer
materials with high thermal conductivity are layered as the
temperature regulating material between the cover member and the
high-temperature area of the exhaust manifold.
7. The engine exhaust structure according to claim 1, wherein a
cover member is provided to cover the exhaust manifold, and heat
shield materials are layered as the temperature regulating material
on an area of the cover member corresponding to a low-temperature
area of the exhaust manifold.
8. The engine exhaust structure according to claim 1, wherein a
cover member is provided to cover the exhaust manifold, and
temperature regulating materials are layered as the temperature
regulating material between the cover member and the exhaust
manifold, an area of each of the temperature regulating materials
corresponding to the high-temperature area of the exhaust manifold
being made higher in thermal conductivity than an area of each of
the temperature regulating materials corresponding to the
low-temperature area of the exhaust manifold.
9. The engine exhaust structure according to claim 1, wherein the
exhaust manifold has a two-tiered structure with an inner member
and an outer member in part or in all, and heat transfer materials
with high thermal conductivity are layered as the temperature
regulating material on the high-temperature area of the exhaust
manifold between the inner member and the outer member.
10. The engine exhaust structure according to claim 1, wherein the
exhaust manifold has a two-tiered structure with an inner member
and an outer member in part or in all, and heat shield materials
are layered as the temperature regulating material on the
low-temperature area of the exhaust manifold between the inner
member and the outer member.
11. The engine exhaust structure according to claim 1, wherein the
exhaust manifold has a two-tiered structure with an inner member
and an outer member in part or in all, and temperature regulating
materials are layered as the temperature regulating material
between the inner member and the outer member, an area of each of
the temperature regulating materials corresponding to the
high-temperature area of the exhaust manifold being made higher in
thermal conductivity than an area of each of the temperature
regulating materials corresponding to the low-temperature area of
the exhaust manifold.
12. The engine exhaust structure according to claim 1, wherein the
high-temperature area of the exhaust manifold is an area that
contains at least the collecting part.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an engine exhaust
structure.
[0003] 2. Description of the Related Art
[0004] At a middle portion of exhaust passage in an automobile
engine, an exhaust manifold, a catalytic converter and a muffler
are intervened in this order from the upstream side. Exhaust gases
from the engine are collected in the exhaust manifold, purified
through the catalytic converter, muffed by the muffler, and then
emitted to the outside.
[0005] Many mainstream catalytic converters purify exhaust gases by
means of a three-way catalyst. However, those catalytic converters
using a three-way catalyst have a problem that unpurified exhaust
gases are emitted to the outside unless a catalyst temperature
reaches an active temperature or higher.
[0006] For this reason, there have been proposed engine exhaust
structures to shorten the time between when an engine is started
and when a catalyst reaches an active temperature or higher, in
which a catalyst converter is provided as closely to the collecting
part of an exhaust manifold as possible to facilitate a catalyst
temperature rise, or in which a flow path of exhaust gases in an
exhaust manifold has a two-tiered structure with an inner member
and an outer member to form a heat shield space between the two
members for prevention of a temperature decrease of exhaust gases
in the exhaust manifold (refer to Patent Document 1, for
example).
[0007] Additionally, there is proposed a sound insulation cover
attached to an exhaust manifold (for example, refer to Patent
Document 2). The invention described in Patent Document 2 is
intended to cut noise from an engine and protect electronic devices
and their harnesses disposed in an engine room from an exhaust
manifold at a high temperature. Noise-absorbing materials are
layered on the sound insulation cover and act as a heat shield.
This accelerates an increase in an ambient temperature in the
surroundings of the exhaust manifold, thereby promoting the
activation of the catalyst.
Patent Document 1 Japanese Patent Application No. 2005-76605
Patent Document 2 Japanese Patent Application No. 7-119458
[0008] An exhaust manifold is not at a uniform temperature in the
whole. For example, the collecting part and its nearby areas become
at higher temperature than the other areas because exhaust gases
are collected in those areas from individual cylinders. For this
reason, an exhaust manifold is designed to offer thermal resistance
with reference to temperatures of the collecting part and its
nearby areas. However, this design requires the use of highly
heat-resistant and expensive metal materials even for areas at low
temperatures as well as the collecting part and its nearby areas,
although the areas at low temperature are not needed to be as
heat-resistant as the areas at high temperatures. This causes
higher costs of manufacturing exhaust manifolds. In particular, if
the collecting part and the branched pipe are two-tiered or are
covered with a cover member for facilitation of the catalyst
temperature during a warm-up and higher performance of exhaust gas
purification as with the inventions described in Patent Documents 1
and 2, the performance of exhaust gas purification will be enhanced
during the warm-up. Instead, the whole exhaust manifold needs to be
formed from highly nickel-containing stainless, for example, which
is excellent in heat resistance but is very expensive, because the
collecting part and its nearby areas are excessively become high in
temperature after the warm-up. This leads to a significant increase
in costs of manufacturing exhaust manifolds.
SUMMARY OF THE INVENTION
[0009] An object of the present invention is to provide an engine
exhaust structure which contributes to a decrease in manufacturing
costs of exhaust manifolds while offering sufficient heat-resistant
properties of an exhaust manifold, by regulating uniformly the
temperatures of individual parts of the exhaust manifold.
[0010] An engine exhaust structure in the present invention is
provided with a temperature regulating material for regulating a
temperature of an exhaust manifold such that individual parts of
the exhaust manifold are uniformed in temperature.
[0011] In the exhaust structure, the temperature regulating
material regulates a temperature of an exhaust manifold in such a
manner that individual parts of the exhaust manifold are uniformed
in temperature, thereby preventing a local temperature rise in the
exhaust manifold. Accordingly, with lower requirements for the
heat-resistant properties of an exhaust manifold, it is possible to
form an exhaust manifold from a metal material which is somewhat
less heat-resistant but is available at an inexpensive price,
resulting in a decrease in costs of manufacturing exhaust
manifolds.
[0012] In a preferred embodiment, a cover member may be provided to
cover the exhaust manifold, and heat transfer materials with high
thermal conductivity may be layered as the temperature regulating
material on the cover member at an area corresponding to a
high-temperature area of the exhaust manifold. In this case, heat
from the area of the cover member corresponding to the
high-temperature area of the exhaust manifold is efficiently
transferred by the heat transfer materials to an outer panel side
of the cover member, thereby facilitating heat dissipation from the
area to the outside. This retards the increase of an ambient
temperature in the surroundings of the high-temperature area of the
exhaust manifold, which prevents a local temperature rise in the
whole exhaust manifold. By the prevention of local temperature
elevation, it is possible to form an exhaust manifold from an
inexpensive metal material, which leads to a reduction in
manufacturing costs of exhaust manifolds, as stated above. Further,
since the exhaust manifold is covered with the cover member, a
temperature rise in the whole exhaust manifold is facilitated, a
temperature rise in a catalyst in a catalytic converter is
accelerated, and the time required for the catalyst to reach an
active temperature or more can be shortened to improve the
performance of exhaust gas purification.
[0013] In another preferred embodiment, a cover member may be
provided to cover the exhaust manifold, and heat shield materials
may be layered as the temperature regulating material on the cover
member at an area corresponding to a low-temperature area of the
exhaust manifold. In this case, the heat shield materials prevent
the dissipation of heat to the outside from the area of the cover
member corresponding to the low-temperature area of the exhaust
manifold. This facilitates a raise in an ambient temperature in the
surroundings of the low-temperature area of the exhaust manifold,
and regulates uniformly the temperatures of the individual parts of
the exhaust manifold, thereby preventing a local temperature rise
in the whole exhaust manifold. Accordingly, it is possible to form
an exhaust manifold from an inexpensive metal material and to
reduce the costs of manufacturing exhaust manifolds, as stated
above. Further, since the exhaust manifold is covered with the
cover member, a temperature rise in the whole exhaust manifold is
facilitated, a temperature rise in the catalyst of the catalytic
converter is accelerated, and the time required for the catalyst to
reach an active temperature or more can be shortened to improve the
performance of exhaust gas purification. Moreover, the prevention
of heat dissipation from the cover member by the heat shield
materials allows the exhaust manifold to be regulated in
temperature. This causes the heat of exhaust gases to efficiently
act on the catalytic converter, thereby accelerating a temperature
rise in the catalyst.
[0014] In another preferred embodiment, a cover member may be
provided to cover the exhaust manifold, and temperature regulating
materials may be layered as the temperature regulating material on
the cover member, an area of each of the temperature regulating
materials corresponding to the high-temperature area of the exhaust
manifold being made higher in thermal conductivity than an area of
each of the temperature regulating materials corresponding to the
low-temperature area of the exhaust manifold. In this case, the
temperature regulating materials facilitate heat dissipation to the
outside from the outer panel of the cover member at a
high-temperature area, and suppress heat dissipation to the outside
from the outer panel of the cover member at a low-temperature area.
This regulates uniformly an ambient temperature in the surroundings
of the exhaust manifold with further efficiency, regulates
uniformly the temperatures of the individual parts of the exhaust
manifold, and prevents a local temperature rise in the exhaust
manifold. Accordingly, it is possible to form the exhaust manifold
from an inexpensive metal material and reduce the costs of
manufacturing exhaust manifolds, as stated above. Further, since
the exhaust manifold is covered with the cover member, a
temperature rise in the whole exhaust manifold is facilitated, a
temperature rise in the catalyst in the catalytic converter is
accelerated, and the time required for the catalyst to reach an
active temperature or more can be shortened to improve the
performance of exhaust gas purification.
[0015] In another preferred embodiment, a cover member may be
provided to the exhaust manifold and a heat dissipation material as
the temperature regulating material may coat an outer surface of
the area of the cover member corresponding to the high-temperature
area of the exhaust manifold. In this case, heat from the area of
the cover member corresponding to the high-temperature area of the
exhaust manifold is efficiently dissipated to the outside by the
heat dissipation material. This suppresses an increase in an
ambient temperature in the surroundings of the high-temperature
area of the exhaust manifold, regulates uniformly the temperatures
of the individual parts of the exhaust manifold, and prevents a
local temperature rise in the exhaust manifold. Accordingly, with
lower requirements for the heat-resistant properties of an exhaust
manifold, it is possible to form an exhaust manifold from an
inexpensive metal material, resulting in a decrease in costs of
manufacturing exhaust manifolds, as described above.
[0016] In another preferred embodiment, a cover member may be
provided to cover the exhaust manifold, and heat transfer materials
with high thermal conductivity may be layered as the temperature
regulating material between the cover member and the
high-temperature area of the exhaust manifold. In this case, heat
from the high-temperature area of the exhaust manifold is
efficiently transferred to the cover member side by the heat
transfer materials, regulates uniformly temperatures of the
individual parts of the exhaust manifold, and prevents a local
temperature rise in the exhaust manifold. Accordingly, with lower
requirements for the heat-resistant properties of an exhaust
manifold, it is possible to form an exhaust manifold from an
inexpensive metal material, resulting in a decrease in costs of
manufacturing exhaust manifolds, as stated above.
[0017] In another preferred embodiment, a cover member may be
provided to cover the exhaust manifold, and heat shield materials
may be layered as the temperature regulating material on the area
of the cover member corresponding to the low-temperature area of
the exhaust manifold. In this case, the heat shield materials
prevent the dissipation of heat to the outside from the area of the
cover member corresponding to the low-temperature area of the
exhaust manifold. This facilitates a rise in an ambient temperature
in the surroundings of the low-temperature area of the exhaust
manifold, and regulates uniformly the temperatures of the
individual parts of the exhaust manifold, thereby preventing a
local temperature rise in the exhaust manifold. Accordingly, with
lower requirements for the heat-resistant properties of an exhaust
manifold, it is possible to form an exhaust manifold from an
inexpensive metal material and reduce the costs of manufacturing
exhaust manifolds, as stated above.
[0018] In another preferred embodiment, a cover member may be
provided to cover the exhaust manifold, and temperature regulating
materials may be layered as the temperature regulating material
between the cover member and the exhaust manifold, an area of each
of the temperature regulating materials corresponding to the
high-temperature area of the exhaust manifold being made higher in
thermal conductivity than an area of each of the temperature
regulating materials corresponding to the low-temperature area of
the exhaust manifold. In this case, the temperature regulating
materials facilitate heat transfer from the exhaust manifold to the
cover member at the high-temperature area, and suppress heat
transfer from the exhaust manifold to the cover member at the
low-temperature area. This regulates uniformly temperatures of the
individual parts of the exhaust manifold, and prevents a local
temperature rise in the exhaust manifold. Accordingly, with low
requirements for the heat-resistant properties of an exhaust
manifold, it is possible to form an exhaust manifold from an
inexpensive metal material, resulting in a decrease in costs of
manufacturing exhaust manifolds, as stated above.
[0019] In another preferred embodiment, the exhaust manifold may
have a two-tiered structure with an inner member and an outer
member in part or in all, and heat transfer materials with high
thermal conductivity may be layered as the temperature regulating
material on the high-temperature area of the exhaust manifold
between the inner member and the outer member. In this case, at the
high-temperature area of the exhaust manifold, the heat transfer
materials transfer heat from the inner member to the outer member,
facilitate the heat dissipation from the outer member, regulate
uniformly the temperatures of the individual parts of the exhaust
manifold, and prevent a local temperature rise in the exhaust
manifold. Accordingly, with lower requirements for the
heat-resistant properties of an exhaust manifold, it is possible to
form an exhaust manifold from an inexpensive metal material,
resulting in a decrease in costs of manufacturing exhaust
manifolds, as stated above. Further, since the exhaust manifold has
a two-tiered structure with the inner member and the outer member,
a temperature rise in the whole inner member is facilitated, a
temperature rise in the catalyst in the catalytic converter is
accelerated, and the time required for the catalyst to reach an
active temperature or more can be shortened to improve the
performance of exhaust gas purification.
[0020] In another preferred embodiment, the exhaust manifold may
have a two-tiered structure with an inner member and an outer
member in part or in all, and heat shield materials may be layered
as the temperature regulating material on the low-temperature area
of the exhaust manifold between the inner member and the outer
member. In this case, at the low-temperature area of the exhaust
manifold, the heat shield materials block heat from the inner
member to suppress heat transfer to the outer member, regulate
uniformly the temperatures of the individual parts of the exhaust
manifold, and prevent a local temperature rise in the exhaust
manifold. Accordingly, with lower requirements for the
heat-resistant properties of an exhaust manifold, it is possible to
form an exhaust manifold from an inexpensive metal material,
resulting in a decrease in costs of manufacturing exhaust
manifolds, as stated above. Further, since the exhaust manifold has
a two-tiered structure with the inner member and the outer member,
a temperature rise in the whole inner member is facilitated, a
temperature rise in the catalyst in the catalytic converter is
accelerated, and the time required for the catalyst to reach an
active temperature or more can be shortened to improve the
performance of exhaust gas purification. Moreover, since the
prevention of heat dissipation from the inner member by the heat
shield materials allows the exhaust manifold to be regulated in
temperature, it is possible to cause the heat of exhaust gases to
efficiently act on the catalytic converter, thereby accelerating a
temperature rise in the catalyst.
[0021] In another preferred embodiment, the exhaust manifold may be
a two-tiered structure with an inner member and an outer member in
part or in all, and temperature regulating materials may be layered
as the temperature regulating material between the inner member and
the outer member, an area of each of the temperature regulating
materials corresponding to the high-temperature area of the exhaust
manifold being made higher in thermal conductivity than an area of
each of the temperature regulating materials corresponding to the
low-temperature area of the exhaust manifold. In this case, the
temperature regulating materials facilitate heat dissipation from
the inner member to the outer member at the high-temperature area,
and suppress heat dissipation from the inner member to the outer
member at a low-temperature area. This regulates uniformly the
temperatures of the individual parts of the exhaust manifold more
effectively, thereby preventing a local temperature rise in the
exhaust manifold. Accordingly, with low requirements for the
heat-resistant properties of an exhaust manifold, it is possible to
form an exhaust manifold from an inexpensive metal material and
reduce the costs of manufacturing exhaust manifolds, as stated
above. Further, since the exhaust manifold is covered with the
cover member, a temperature rise in the whole exhaust manifold is
facilitated, a temperature raise in the catalyst in the catalytic
converter is accelerated, and the time required for the catalyst to
reach an active temperature or more can be shortened to improve the
performance of exhaust gas purification.
[0022] In another preferred embodiment, the high-temperature area
of the exhaust manifold is an area that contains at least the
collecting part. The collecting part of the exhaust manifold
becomes high in temperature due to exhaust gases collected from the
individual cylinders of an engine. Therefore, when the area
containing the collecting part is set as the high-temperature area
and the remaining branched area is set as the low-temperature area,
the temperatures of the two areas can be regulated uniformly.
[0023] According to an engine exhaust structure in the present
invention, the temperature regulating materials regulate a
temperature of the exhaust manifold in such a manner that
temperatures of the individual parts of the exhaust manifold are
uniformed, thereby preventing a local temperature rise in the
exhaust manifold. Accordingly, with lower requirements for the
heat-resistant properties of an exhaust manifold, it is possible to
form an exhaust manifold from a metal material which is somewhat
less heat-resistant but is available at an inexpensive price,
resulting in a decrease in costs of manufacturing exhaust
manifolds.
DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a perspective view of main components of an engine
exhaust structure;
[0025] FIG. 2 is a front view of an exhaust manifold;
[0026] FIG. 3 is a cross-sectional view of the exhaust manifold in
FIG. 2 with a cover member and without temperature regulating
materials, taken along line III-III;
[0027] FIG. 4 is a view of the exhaust manifold with temperature
regulating materials, which is equivalent to FIG. 3; and
[0028] FIG. 5 is a front view of an exhaust manifold of another
configuration.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] Hereinafter, embodiments of the present invention will be
described with reference to the drawings.
[0030] First, a basic configuration of an automobile engine exhaust
structure will be discussed.
[0031] An engine 10 shown in FIG. 1 is an automobile inline
four-cylinder engine. At a middle portion of an exhaust passage in
the engine 10, an exhaust manifold 11, a catalytic converter 12 and
a muffler (not shown) are intervened in this order from the
upstream side. Exhaust gases from the engine 10 are collected in
the exhaust manifold 11, purified through the catalytic converter
12, muffed by the muffler, and then emitted to the outside.
[0032] As shown in FIGS. 1 to 3, the exhaust manifold 11 includes
four branched pipes 15 connected respectively to four exhaust ports
14 formed in a cylinder head 13, a collecting pipe 16 aggregating
downstream ends of the four branched pipes 15, and outer members 17
each covering a pair of the adjacent branched pipes 15.
[0033] A first tubular clearance 18 of 1.0 to 4.0 mm in thickness,
for example, is provided between the outer members 17 and the
branched pipes 15 along the almost full lengths thereof. Each of
the outer members 17 is formed from an upper surface plate 17U and
a lower surface plate 17L. The outer member 17 is assembled in such
a manner as to surround the branched pipe 15 by combining the upper
surface plate 17U and the lower surface plate 17L with the branched
pipes 15 inside thereof and welding the two plates together in a
butt joint. Provided at an upstream end of each of the outer
members 17 is a bifurcated part 17a that is branched into two.
Upstream ends of the branched pipes 15 are individually fitted into
the bifurcated part 17a of the outer member 17. Provided at an
upstream end of the exhaust manifold 11 is an overlaid part 17b in
which the upstream end of the bifurcated part 17a is reduced in
diameter and overlaid on the upstream end of the branched pipe 15.
An attachment sheet 19 is provided at the upstream end of the
exhaust manifold 11 for attachment to the cylinder head 13. The
attachment sheet 19 is provided with four through-holes 20
corresponding to the exhaust ports 14. By inserting and welding the
overlaid parts 17b individually into the four through-holes 20, the
four branched pipes 15 and the two outer members 17 are combined
via the attachment sheet 19. A downstream end of the outer member
17 is welded into the collecting pipe 16. A spacer member 21 for
preventing vibrations of the branched pipe 15 is intervened between
the downstream end of the branched pipe 15 and the downstream end
of the outer member 17. In addition, a flange member 22 is welded
into a downstream end of the collecting pipe 16 for connection to
an exhaust pipe on the downstream side.
[0034] Provided at both upper and lower sides of the exhaust
manifold 11 are cover members 25 for blocking noise and heat from
the exhaust manifold 11. The upper and lower cover members 25 are
each fixed to the exhaust manifold 11 by means of a bracket member
26 provided on the exhaust manifold 11. A second clearance 27 is
provided between the exhaust manifold 11 and the cover member 25.
However, the lower cover member 25 may be eliminated.
[0035] The upper and lower cover members 25 each include an outer
panel 28 disposed on the outer surface side and an inner panel 29
disposed on the exhaust manifold 11 side. A third clearance 30 is
provided between the outer panel 28 and the inner panel 29. In the
third clearance 30, sound-absorbing materials or temperature
regulating materials 31 to be discussed below are layered in close
contact with the outer panel 28 and the inner panel 29. The outer
panel 28 and the inner panel 29 are made by press-molding metal
plates of stainless steel or the like. However, the inner panel 29
may be formed from general-purpose punching metal or mesh for
higher sound-absorbing quality.
[0036] The present invention is characterized in that, in an
exhaust structure of the engine 10 formed basically as described
above, temperature regulating materials are disposed as shown in
FIG. 4, for example, for regulating uniformly temperatures of the
individual parts of the exhaust manifold 11.
[0037] The exhaust manifold 11 becomes higher in temperature from
the cylinder head 13 side to the collecting pipe 16 side. It is
impossible to specify a boundary B between the low-temperature area
LT and the high-temperature area HT as shown in FIG. 4. However,
assuming that a pipe length between the upstream end of the
branched pipe 15 and the boundary B is L1, and that a pipe length
between the boundary B and the downstream end of the collecting
pipe 16 is L2, the boundary B can be set within a range that
L1/(L1+L2) becomes 20 to 35%.
[0038] As the temperature regulating material 31, a heat transfer
material 31A is tightly arranged in the high-temperature area(s) HT
of one or more selected from the first clearance 18, the second
clearance 27 and the third clearance 30. In addition, a heat shield
material 31B is tightly arranged in the low-temperature area(s) LT
of one or more selected from the first clearance 18, the second
clearance 27 and the third clearance 30. Further, a heat
dissipation material 31C may coat the outer surface of at least one
of the high-temperature area HT of the exhaust manifold 11 and the
high-temperature area HT of the cover member 25. However, the first
clearance 18 between the branched pipe 15 and the outer member 17
acts as a heat insulating space, and therefore the heat shield
material 31B for the low-temperature area LT may be eliminated.
Additionally, if the heat transfer material 31A is provided in the
high-temperature area HT of the second clearance 27, a coating of
the heat dissipation material 31C to the outer surface of the
high-temperature area HT of the exhaust manifold 11 may be
eliminated. Further, if the heat transfer material 31A or the heat
shield material 31B is not provided in the third clearance 30, a
sound-absorbing material is to be provided in the location instead.
The temperature regulating material 31 is only needed to be
provided such that temperatures of the individual parts of the
exhaust manifold 11, in particular, temperatures of the branched
pipes 15 and the collecting pipe 16 are uniformly regulated. The
temperature regulating material 31 may be provided to at least one
of the above-described areas.
[0039] In particular, as shown in FIG. 4, the heat transfer
materials 31A are provided to the high-temperature area HT of the
first clearance 18 and the high-temperature area HT of the second
clearance 27, the heat dissipation material 31C coats the outer
surface of the cover member 25, and the heat shield materials 31B
are provided to the low-temperature area LT of the second clearance
27. Accordingly, the heat transfer materials 31A transfer
efficiently heat from the high-temperature area HT of the exhaust
manifold 11 to the cover member 25, and then the heat dissipation
material 31C dissipates heat from the outer surface of the cover
member 25 to the outside. Accordingly, it is possible to prevent
excessively high temperatures of the downstream portions of the
branched pipes 15 and the collecting pipe 16 with most strict
requirements for heat resistance, and to improve the heat-retaining
properties of the upstream sides of the branched pipes 15 for
accelerating a temperature rise. This allows the branched pipes 15
and the collecting pipe 16 to be regulated in temperature uniformly
as a whole.
[0040] The heat shield material 31B may use preferably a mat formed
from inorganic fibers such as glass fibers, rock wool fibers,
ceramic fibers or potassium titanate fibers, or organic fibers such
as poly-phenylene-benzobisoxazole (PBO) fibers.
[0041] The heat transfer material 31A may use a mat formed from
metal fibers such as stainless fibers, steel fibers, copper fibers,
brass fibers, bronze fibers or aluminum fibers, or carbon fibers
such as pitch-based carbon fibers or PAN-based carbon fibers, or
metal plating fibers. In addition, to seal the first clearance 18
between the outer member 17 and the branched pipe 15 and the third
clearance 30 between the outer panel 28 and inner panel 29 of the
cover member 25, these clearances 18 and 30 may be filled with one
or a mixture of any combination of carbon powder, graphitic powder,
aluminum powder, copper powder, brass powder, and bronze powder.
Further, any of the above-mentioned fiber materials may support any
of the above-mentioned powders when it is formed into a mat.
[0042] The heat dissipation material 31C may appropriately use a
ceramic-based heat dissipation coating material, for example,
Cooltech (made by Okitsumo Incorporated). Alternatively, a silicon-
or acryl-based heat dissipation sheet may be stuck as the heat
dissipation material 31C.
[0043] The temperature regulating materials 31 to be attached to
different areas may be formed from a material of the same kind or
from materials of different kinds. In this embodiment, the exhaust
manifold 11 is divided into two segments of low-temperature area LT
and high-temperature area HT. Alternatively, the exhaust manifold
11 may be divided into three segments of high-temperature area,
medium-temperature area and low-temperature area, or more segments,
such that the individual parts of the exhaust manifold 11 are
uniform in temperature. Further, the temperature regulating
material 31 may change gradually or continuously in heat shield
properties and/or heat transfer properties to regulate a
temperature of the exhaust manifold 11 in a more detailed
manner.
[0044] The present invention is also applicable to an exhaust
structure for the engine 10 without the outer member 17 and an
exhaust structure for the engine 10 without the cover member 25.
For an exhaust structure without the outer member 17, the heat
shield material 31B or heat transfer material 31A is disposed in at
least one of the second clearance 27 between the cover member 25
and the branched pipe 15 and the third clearance 30 between the
outer panel 28 and inner panel 29 of the cover member 25.
Alternatively, the heat dissipation material 31C coats the outer
surfaces of the branched pipe 15 and collecting pipe 16, or the
outer surface of the cover member 25 at the high-temperature area
HT. For an exhaust structure without the cover member 25, the heat
shield material 31B or the heat transfer material 31A is disposed
in the first clearance 18 between the outer member 17 and the
branched pipe 15, the heat dissipation material 31C is disposed on
the outer surfaces of the outer member 17 and collecting pipe 16.
Further, if the cover member 25 is a cover member without the third
clearance 30 formed between the outer panel 28 and the inner panel
29, or if the cover member 25 is a cover member formed from a
single panel, the heat shield material 31B or the heat transfer
material 31A is disposed in the first clearance 18 between the
outer member 17 and the branched pipe 15 and is disposed in the
second clearance 27 between the cover member and the branched pipe
15, and the heat dissipation material 31C coats the outer surface
of the exhaust manifold 11 or the outer surface of the cover member
at the high-temperature area HT.
[0045] The present invention is applicable to any configuration of
the exhaust manifold 11. For example, as shown in FIG. 5, the
present invention may be applied to an exhaust manifold 41
including four branched pipes 40 of different lengths.
Additionally, the present invention can be applied to an exhaust
manifold with the outer member 17 surrounding the individual
branched pipes 15. For provision of such an outer member
surrounding the individual branched pipes 15, the outer member may
be formed by welding the upper surface plate and the lower surface
plate together, or the outer member 17 formed from a pipe member
larger in diameter than the branched pipe 15 may be attached to the
outside of the branched pipe 15. Moreover, the present invention
can be applied to exhaust structures for inline multi-cylinder
engines and V-type multi-cylinder engines as well as those for the
inline four-cylinder engine 10.
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