U.S. patent application number 12/003724 was filed with the patent office on 2008-07-10 for vehicle exhaust system structure.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Tomoki Mabuchi, Hisashi Nishino.
Application Number | 20080163613 12/003724 |
Document ID | / |
Family ID | 39247214 |
Filed Date | 2008-07-10 |
United States Patent
Application |
20080163613 |
Kind Code |
A1 |
Mabuchi; Tomoki ; et
al. |
July 10, 2008 |
Vehicle exhaust system structure
Abstract
A vehicle exhaust system structure is obtained which can protect
well a bend portion of an exhaust pipe. A vehicle exhaust system
structure 10 is intended to discharge exhaust gases of a
front-engine front-drive vehicle with a transverse engine from a
rear part of a vehicle body and is applied to an exhaust system 11
which is configured such that a first catalytic converter 12, a
second catalytic converter 14, an exhaust system heat exchanger 15
and a muffler 16 are disposed sequentially in that order from an
upstream side in an exhaust gas flow direction. In the exhaust
system 11, a heat exchanger to muffler exhaust pipe 26 which
connects the exhaust system heat exchanger 15 to the muffler 16 has
an inclined portion 26A, and a portion of the exhaust system 11
which lies further rearwards than the exhaust system heat exchanger
15 is suspended from the vehicle body by a suspension unit 80.
Provided on a catalytic converter to heat exchanger exhaust pipe 24
which connects the second catalytic converter 14 to the exhaust
system heat exchanger 15 is a ball joint 96 which permits a
relative displacement between the second catalytic converter 14 and
the exhaust system heat exchanger 15.
Inventors: |
Mabuchi; Tomoki;
(Toyota-shi, JP) ; Nishino; Hisashi; (Aichi-gun,
JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
TOYOTA-SHI
JP
|
Family ID: |
39247214 |
Appl. No.: |
12/003724 |
Filed: |
December 31, 2007 |
Current U.S.
Class: |
60/299 ;
181/227 |
Current CPC
Class: |
B60K 13/04 20130101;
Y02A 50/20 20180101; Y02A 50/2322 20180101; F01N 13/1811 20130101;
F01N 3/2885 20130101; F01N 13/1816 20130101; F01N 13/009 20140601;
F01N 13/08 20130101; F01N 13/0093 20140601; F01N 13/1822
20130101 |
Class at
Publication: |
60/299 ;
181/227 |
International
Class: |
F01N 3/10 20060101
F01N003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 9, 2007 |
JP |
2007-001581 |
Claims
1. A vehicle exhaust system structure for discharging exhaust gases
of an internal combustion engine, which is transversely installed
in a front part of a vehicle body, from a rear part of the vehicle
body, the vehicle exhaust system structure comprising: a first
catalytic device, a second catalytic device, an exhaust heat
recovery unit and a silencer which are disposed sequentially in
that order from an upstream side in an exhaust gas flow direction;
a first exhaust pipe which connects the second catalytic device to
the exhaust heat recovery unit; a second exhaust pipe which
includes a portion extending in a direction intersecting a vehicle
front-rear direction and, which connects the exhaust heat recovery
unit, which is disposed to be offset in a vehicle width direction,
to the silencer; a suspension unit which suspends at least part of
the exhaust system elements including the exhaust heat recovery
unit, the second exhaust pipe, and the silencer, relative to the
vehicle body, on a downstream side in an exhaust gas flow direction
relative to the first exhaust pipe; and a vibration cut-off
mechanism which is provided at the first exhaust pipe and permits a
relative displacement between the second catalytic device and the
exhaust heat recovery unit.
2. The vehicle exhaust system structure according to claim 1,
wherein the first catalytic device, the second catalytic device,
the first exhaust pipe and the exhaust heat recovery unit are
disposed linearly along a vehicle front-rear direction when seen in
plan view, the vibration cut-off mechanism is configured such that
a front portion and a rear portion of the first exhaust pipe in the
vehicle front-rear direction may be displaced relative to each
other in a vehicle vertical direction.
3. The vehicle exhaust system structure according to claim 1,
wherein the suspension unit has a heat recovery unit suspending
portion which suspends the exhaust heat recovery unit relative to
the vehicle body, and which is at a position furthest upstream in
an exhaust gas flow direction, and wherein the heat recovery unit
suspending portion includes a supported member which is fixed to a
low-rigidity portion of the exhaust heat recovery unit.
4. The vehicle exhaust system structure according to claim 2,
wherein the suspension unit has a heat recovery unit suspending
portion which suspends the exhaust heat recovery unit relative to
the vehicle body, and which is at a position furthest upstream in
an exhaust gas flow direction, and wherein the heat recovery unit
suspending portion includes a supported member which is fixed to a
low-rigidity portion of the exhaust heat recovery unit.
5. The vehicle exhaust system structure according to claim 1,
further comprising: a vibration cut-off mechanism which permits a
relative displacement between the first catalytic device and the
second catalytic device.
6. The vehicle exhaust system structure according to claim 2,
further comprising: a vibration cut-off mechanism which permits a
relative displacement between the first catalytic device and the
second catalytic device.
7. The vehicle exhaust system structure according to claim 3,
further comprising: a vibration cut-off mechanism which permits a
relative displacement between the first catalytic device and the
second catalytic device.
8. The vehicle exhaust system structure according to claim 4,
further comprising: a vibration cut-off mechanism which permits a
relative displacement between the first catalytic device and the
second catalytic device.
9. The vehicle exhaust system structure according to claim 1,
wherein a bend portion of the second exhaust pipe is made up of a
shell which is formed at one end of the exhaust heat recovery unit,
and an inclined portion of the second exhaust pipe which extends in
a direction intersecting the vehicle front-rear direction.
10. The vehicle exhaust system structure according to claim 9,
wherein the shell includes a projecting portion which projects in a
direction in which the inclined portion extends, further than an
end surface of the shell in a vehicle width direction.
11. A vehicle exhaust system structure for discharging exhaust
gases of an internal combustion engine, which is transversely
installed in a front part of a vehicle body, from a rear part of
the vehicle body, the vehicle exhaust system structure comprising:
a first catalytic device, a second catalytic device, an exhaust
heat recovery unit and a silencer which are disposed sequentially
in that order from an upstream side in an exhaust gas flow
direction; an exhaust pipe which includes a portion extending in a
direction intersecting a vehicle front-rear direction, and which
connects the exhaust heat recovery unit, which is disposed to be
offset in a vehicle width direction, to the silencer; a vibration
cut-off mechanism which permits a relative displacement between the
first catalytic device and the second catalytic device, or a
relative displacement between the second catalytic device and the
exhaust heat recovery unit; and a suspension unit which includes a
supported member which is fixed to a low-rigidity portion of the
exhaust heat recovery unit and a support member which supports the
supported member on the vehicle body.
12. The vehicle exhaust system structure according to claim 11,
wherein a bend portion of the exhaust pipe is made up of a shell
which is formed at one end of the exhaust heat recovery unit, and
an inclined portion of the exhaust pipe which extends in a
direction intersecting the vehicle front-rear direction.
13. The vehicle exhaust system structure according to claim 12,
wherein the shell includes a projecting portion which projects in a
direction in which the inclined portion extends, further than an
end surface of the shell in a vehicle width direction.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority under 35 USC 119 from
Japanese Patent Application, No. 2007-1581, the disclosure of which
is incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a vehicle exhaust system
structure for an internal combustion engine which is installed
transversely in a front part of a vehicle body of, for example, a
front-engine front-drive vehicle, and more particularly to a
vehicle exhaust system structure which includes an exhaust heat
recovery unit for recovering exhaust heat.
[0004] 2. Description of the Related Art
[0005] As is disclosed in, for example, Japanese Patent Application
Laid-Open (JP-A) Nos. 10-196358 and 2004-190610, in an exhaust
system which is connected to a transverse internal combustion
engine and in which a catalytic converter, a sub-muffler and a main
muffler are disposed directly in that order from an upstream side
of an exhaust gas flow direction, there is known a structure in
which a bend portion is provided in an exhaust pipe which connects
the sub-muffler to the main muffler and ball joints are provided,
respectively, upstream of the catalytic converter in the exhaust
gas flow direction and directly upstream of the main muffler in the
exhaust gas flow direction.
[0006] In the above-mentioned related art, however, it is feared
that a large magnitude of force is applied to the bend portion of
the exhaust pipe when an exhaust heat recovery unit of large mass
is provided along the exhaust system, and there has still been room
for improvement in this area.
SUMMARY OF THE INVENTION
[0007] The present invention has been made in view of the above
circumstances and provides a vehicle exhaust system structure.
[0008] A first aspect of the present invention provides a vehicle
exhaust system structure for discharging exhaust gases of an
internal combustion engine, which is transversely installed in a
front part of a vehicle body, from a rear part of the vehicle body,
the vehicle exhaust system structure comprising: a first catalytic
device, a second catalytic device, an exhaust heat recovery unit
and a silencer which are disposed sequentially in that order from
an upstream side in an exhaust gas flow direction; a first exhaust
pipe which connects the second catalytic device to the exhaust heat
recovery unit; a second exhaust pipe which includes a portion
extending in a direction intersecting a vehicle front-rear
direction, and which connects the exhaust heat recovery unit, which
is disposed to be offset in a vehicle width direction, to the
silencer; a suspension unit which suspends at least part of the
exhaust system elements including the exhaust heat recovery unit,
the second exhaust pipe, and the silencer, relative to the vehicle
body, on a downstream side in an exhaust gas flow direction
relative to the first exhaust pipe; and a vibration cut-off
mechanism which is provided at the first exhaust pipe and permits a
relative displacement between the second catalytic device and the
exhaust heat recovery unit.
[0009] A second aspect of the present invention provides a vehicle
exhaust system structure for discharging exhaust gases of an
internal combustion engine, which is transversely installed in a
front part of a vehicle body, from a rear part of the vehicle body,
the vehicle exhaust system structure comprising: a first catalytic
device, a second catalytic device, an exhaust heat recovery unit
and a silencer which are disposed sequentially in that order from
an upstream side in an exhaust gas flow direction; an exhaust pipe
which includes a portion extending in a direction intersecting a
vehicle front-rear direction, and which connects the exhaust heat
recovery unit, which is disposed to be offset in a vehicle width
direction, to the silencer; a vibration cut-off mechanism which
permits a relative displacement between the first catalytic device
and the second catalytic device, or a relative displacement between
the second catalytic device and the exhaust heat recovery unit; and
a suspension unit which includes a supported member which is fixed
to a low-rigidity portion of the exhaust heat recovery unit and a
support member which supports the supported member on the vehicle
body.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Embodiments of the present invention will be described in
detail based on the following figures, wherein:
[0011] FIG. 1 is a plan view of an exhaust system to which a
vehicle exhaust system structure according to an embodiment of the
present invention is applied;
[0012] FIG. 2 is a side view of the exhaust system to which the
vehicle exhaust system structure according to the embodiment of the
present invention is applied;
[0013] FIG. 3 is a plan view of an exhaust system heat exchanger
which makes up the vehicle exhaust system structure according to
the embodiment of the present invention;
[0014] FIG. 4 is a cross-sectional side view which shows a valve
device which makes up the vehicle exhaust system structure
according to the embodiment of the present invention;
[0015] FIG. 5A is a cross-sectional plan view which shows a ball
joint which makes up the vehicle exhaust system structure according
to the embodiment of the present invention;
[0016] FIG. 5B is a side view which shows the ball joint which
makes up the vehicle exhaust system structure according to the
embodiment of the present invention;
[0017] FIG. 6A is a plan view which shows a state in which the
exhaust system to which the vehicle exhaust system structure
according to the embodiment of the present invention is applied
vibrates with a specific frequency;
[0018] FIG. 6B is a side view which shows the state in which the
exhaust system to which the vehicle exhaust system structure
according to the embodiment of the present invention is applied
vibrates with the specific frequency;
[0019] FIG. 7A is a plan view which shows a state in which the
exhaust system to which the vehicle exhaust system structure
according to the embodiment of the present invention is applied
vibrates with one other specific frequency; and
[0020] FIG. 7B is a side view which shows the state in which the
exhaust system to which the vehicle exhaust system structure
according to the embodiment of the present invention is applied
vibrates with the one other specific frequency.
DETAILED DESCRIPTION OF THE INVENTION
[0021] Hereinbelow, an example of an exemplary embodiment of the
present invention will be described in detail with reference to the
drawings.
[0022] Firstly, an overall configuration of an exhaust system 11 to
which a vehicle exhaust system structure 10 is applied will be
schematically described, next, an exhaust system heat exchanger 15
which makes up the vehicle exhaust system structure 10 will be
described, and thereafter, a support structure of the exhaust
system 11 relative to a vehicle body will be described which
constitutes a main part of the present invention in the vehicle
exhaust system structure 10. Note that in the following
description, when such words as upstream and downstream are simply
used, they are to denote upstream and downstream of an exhaust gas
flow direction. In addition, an arrow FR, arrow UP and arrow W
which are shown in the respective drawings are to denote,
respectively, front side (running direction) in a vehicle
front-rear direction, upper side in a vehicle vertical direction,
and a vehicle width direction, of a motor vehicle to which the
vehicle exhaust system structure 10 is applied.
[0023] (Overall Configuration)
[0024] FIG. 1 schematically shows an overall configuration of the
vehicle exhaust system structure 10 in plan view, and FIG. 2 shows
the vehicle exhaust system structure 10 in side view. As is shown
in these figures, the exhaust system 11 to which the vehicle
exhaust system structure 10 is applied such that it forms an
exhaust gas flow path, and a first catalytic converter 12 as a
first catalytic device, a second catalytic converter 14 as a second
catalytic device, for purifying exhaust gases, an exhaust system
heat exchanger 15 as an exhaust heat recovery unit for recovering
heat entrained by exhaust gases, in order to promote engine warm-up
and maintain heating, and a muffler 16 for reducing (silencing)
exhaust noise, are provided sequentially in that order from an
upstream side, and these devices are made to communicate in series
with each other by an exhaust pipe 18.
[0025] More specifically, the first catalytic converter 12 is, as
is shown in FIG. 2, directly coupled to an exhaust manifold 20A of
an engine 20, which is an internal combustion engine. The engine 20
is of a transverse type in which an axial direction of a crankshaft
20B coincides substantially with the vehicle width direction and is
installed in a front part of a vehicle body. In this embodiment,
the engine 20 is applied to a front-wheel drive vehicle
(front-engine front-drive vehicle) or a four-wheel drive vehicle
based on a front-wheel drive vehicle, and is configured to impart
driving force to at least front wheels, not shown. In addition, as
is shown in FIGS. 1 and 2, the first catalytic converter 12 and the
second catalytic converter 14 are connected to (made to communicate
with) each other via an inter-catalytic converter exhaust pipe 22
which makes up a furthest upstream portion of the exhaust pipe 18.
The second catalytic converter 14 and the exhaust system heat
exchanger 15 are connected to (made to communicate with) each other
via a catalytic converter to heat exchanger exhaust pipe 24 as a
first exhaust pipe which makes up an upstream portion of the
exhaust pipe 18.
[0026] Furthermore, the exhaust system heat exchanger 15 and the
muffler 16 are connected to each other via a heat exchanger to
muffler exhaust pipe 26 as a second exhaust pipe (exhaust pipe)
which makes up an intermediate portion of the exhaust pipe 18. The
heat exchanger to muffler exhaust pipe 26 is connected to a muffler
inlet pipe 16A of the muffler 16. In addition, a muffler outlet
pipe 16B of the muffler 16 is connected to an upstream end of a
downstream side exhaust pipe 28, which makes up a downstream
portion of the exhaust pipe 18. The downstream side exhaust pipe
28, that is, a downstream end of the exhaust pipe 18 is made to
constitute an atmosphere release portion 18A from which exhaust
gases that have been purified by the catalytic converters 12, 14
are discharged to the atmosphere.
[0027] As a result of the configuration of the exhaust system 11
described above, exhaust gases discharged from the exhaust manifold
20A of the engine 20 which is situated in the front part of the
vehicle body flows sequentially through the first catalytic
converter 12, the inter-catalytic converter exhaust pipe 22, the
second catalytic converter 14, the catalytic converter to heat
exchanger exhaust pipe 24, the exhaust system heat exchanger 15,
the heat exchanger to muffler exhaust pipe 26, the muffler 16 and
the downstream side exhaust pipe 28 in that order and is discharged
to the atmosphere from the atmosphere release portion 18A which is
situated in the rear end portion of the vehicle body.
[0028] (Configuration of Exhaust System Heat Exchanger)
[0029] The exhaust system heat exchanger 15 is configured to
recover heat entrained by exhaust gases to an engine cooling water
as a cooling medium and includes, as is shown in FIG. 4, a
partition wall pipe 30 which isolates a flow path of the exhaust
gases from a flow path of the engine cooling water. In this
embodiment, the partition wall pipe 30 has spiral grooves 30A, 30B
which are spirally formed on internal and external surfaces of a
pipe wall thereof. The spiral grooves 30A, 30B are formed along
almost the full length of a heat exchange portion 15A where heat
exchange is implemented between the exhaust gases and the engine
cooling water, and the front and rear of the partition wall pipe 30
are made to constitute, respectively, an exhaust gas introduction
portion 30C and an exhaust gas exhaust portion 30D which extend
forwards and rearwards relative to the heat exchange portion
15A.
[0030] An inner pipe 32, which functions as a bypass pipe portion
formed substantially into a cylindrical shape, is disposed
coaxially inside the partition wall pipe 30. A space defined
between the partition wall pipe 30 and the inner pipe 32 is made to
constitute an exhaust gas flow path 34 of the exhaust system heat
exchanger 15. In addition, the partition wall pipe 30 is covered
from an outer peripheral side with an outer pipe 36 which is formed
substantially into a cylindrical shape and is disposed coaxially. A
space defined between the partition wall pipe 30 and the outer pipe
36 is made to constitute an engine cooling water flow path 38 of
the exhaust system heat exchanger 15.
[0031] In the exhaust system heat exchanger 15, a range where the
engine cooling water flow path 38 is formed in the exhaust gas flow
direction is made to constitute the heat exchange portion 15A where
heat exchange is implemented between exhaust gases and engine
cooling water, and the inner pipe 32 protrudes further upstream and
downstream than the heat exchange portion 15A. A space within the
inner pipe 32 in this exhaust system heat exchanger 15 is made to
constitute a bypass flow path 40 as an upstream gas flow path for
bypassing the heat exchange portion 15A in the exhaust system heat
exchanger 15.
[0032] More specifically, as is shown in FIG. 4, a downstream end
of the catalytic converter to heat exchanger exhaust pipe 24 is
connected to an upstream end 32A of the inner pipe 32, and a
downstream end 32B of the inner pipe 32 is connected almost
coaxially to an upstream end 42A of an exhaust gas guide pipe 42.
Note that in place of the exhaust gas guide pipe 42, the inner pipe
32 may be extended towards the downstream side. In addition, a
front end of the exhaust gas introduction portion 30C (the portion
further upstream than the heat exchange portion 15A) which projects
further upstream than the outer pipe 36 (the engine cooling water
flow path 38) in the partition wall pipe 30 is connected to an
outer peripheral surface of the upstream end 32A of the inner pipe
32 in an airtight fashion. Furthermore, the exhaust gas exhaust
portion 30D (the portion further downstream than the heat exchange
portion 15A) of the partition wall pipe 30 which projects further
downstream than the outer pipe 36 (the engine cooling water flow
path 38) in the partition wall pipe 30 is connected to the exhaust
gas guide pipe 42 via an end pipe 44 in an airtight fashion.
[0033] In addition, through-holes 46, which establish a
communication between the bypass flow path 40 which is the space
inside the inner pipe 32 and the exhaust gas flow path 34 of the
exhaust system heat exchanger 15, are provided in a portion of the
inner pipe 32 which lies inside the exhaust gas introduction
portion 30C of the partition wall pipe 30. Namely, the
through-holes 46 makes up a diverging portion between the exhaust
gas flow path 34 and the bypass flow path 40. On the other hand,
through-holes 48, which establish a communication between the
inside and outside of the exhaust gas flow path 34, are provided in
the end pipe 44. The through-holes 48 and a downstream side opening
end 42B of the exhaust gas guide pipe 42 are both made to open to
an exhaust gas exit header 52 which is a space within a heat
exchanger rear portion shell 50, as a shell, of which an upstream
side opening end 50A is airtightly connected to the end pipe
44.
[0034] Consequently, in the exhaust system heat exchanger 15,
exhaust gases which have bypassed the heat exchange portion 15A and
passed through the bypass flow path 40 reaches the exhaust gas exit
header 52 within the heat exchanger rear portion shell 50 by way of
the inside of the exhaust gas guide pipe 42, while exhaust gases
which have passed through the exhaust gas flow path 34 by way of
the through-holes 46 reaches the exhaust gas exit header 52 within
the heat exchanger rear portion shell 50 by way of the outside of
the exhaust gas guide pipe 42 and the through-holes 48.
[0035] Furthermore, the exhaust system heat exchanger 15 includes a
valve device 54 for opening and closing the downstream side opening
end 42B of the exhaust gas guide pipe 42. The valve device 54
includes a valve 58 which can take a closed position (refer to
solid lines in FIG. 4) in which the valve 58 rotates around a
rotational shaft 56 which is supported by the heat exchanger rear
portion shell 50 so as to close the downstream side opening end 42B
of the exhaust gas guide pipe 42 and an open position (refer to
imaginary lines in FIG. 4) in which the valve 58 rotates in a
direction indicated by an arrow A from the closed position to open
the downstream side opening end 42B of the exhaust gas guide pipe
42. The valve 58 is configured to be brought into abutment with a
valve seat (a seal) 60 provided around the downstream side opening
end 42B of the exhaust gas guide pipe 42 when the valve 58 is
positioned in the closed position.
[0036] The rotational shaft 56, which is made long in the vehicle
width direction, is supported on a frame 62 fixed to the exhaust
gas guide pipe 42 in such a manner as to rotate relative to the
heat exchanger rear portion shell 50. The valve 58 is connected to
the rotational shaft 56 via an arm 64 in such a manner as to rotate
together with the rotational shaft 56, whereby the valve 58 is
allowed to rotate around the rotational shaft 56 to thereby take
the aforesaid closed position and open position. In addition, a
return spring 66, which functions as a biasing member for
generating biasing force to displace the valve 58 to the closed
position, is provided on an end portion of the rotational shaft 56
which projects outwards of the heat exchanger rear portion shell
50. As is shown in FIG. 3, the end portion of the rotational shaft
56 and the return spring 66 are covered with a heat insulation
cover 68.
[0037] In the exhaust system heat exchanger 15 having the valve
device 54 that has been described heretofore, in the event that the
pressure of exhaust gases is low, the valve 58 closes the exhaust
gas guide pipe 42, that is, the bypass flow path 40 by virtue of
the biasing force of the return spring 66, so that exhaust gases
are allowed to flow through the exhaust gas flow path 34 of the
heat exchange portion 15A. On the other hand, when the pressure of
exhaust gases reaches or exceeds a predetermined value, the valve
58 is designed to take an open position according to the pressure
of exhaust gases against the biasing force of the return spring 66.
In this embodiment, the valve 58 is set to take an open position
(refer to the imaginary lines in FIG. 4), in which the opening of
the valve by virtue of the pressure of exhaust gases becomes
maximum, by virtue of the pressure of exhaust gases at which a
maximum output of the engine 20 is generated.
[0038] In addition, in this embodiment, the valve device 54 is made
to force the valve 58 to be held in the open position irrespective
of the pressure of exhaust gases in the event that the temperature
of engine cooling water which exchanges heat with exhaust gases
reaches or exceeds a predetermined temperature. Specifically, as is
shown in FIG. 3, a first cooling water inlet pipe 70, which
communicates with the engine cooling water flow path 38 in an
interior thereof, is connected to a downstream side of the outer
pipe 36 in the exhaust gas flow direction. A thermoactuator 72,
whose operation end is provided inside the heat insulation cover
68, is provided at an end portion of the first cooling water inlet
pipe 70. The thermoactuator 72 is configured to rotate the
rotational shaft 56 against the biasing force of the return spring
66 by virtue of thermal expansion of wax filled in the interior
thereof. In this embodiment, the thermoactuator 72 is made to
cause, via the rotational shaft 56, the valve 58 to take a full
open position whose opening is larger than that of the open
position realized by virtue of the pressure of exhaust gases (to
cause the valve 58 to maintain the full open position) in the event
that the engine cooling water temperature is equal to or higher
than 80.degree. C. As is indicated by long-dashed short-dashed
lines in FIG. 4, the full open position is a position resulting
when the valve 58 rotates about 90.degree. in the direction
indicated by the arrow A from the closed position.
[0039] As is shown in FIG. 3, a second cooling water inlet pipe 74
is connected to an intermediate portion of the first cooling water
inlet pipe 70 for introducing engine cooling water into the engine
cooling water flow path 38 of the exhaust system heat exchanger 15
by way of the first cooling water inlet pipe 70. On the other hand,
a cooling water outlet pipe 76 is connected to an upstream side of
the outer pipe 36 in the exhaust gas flow direction for discharging
engine cooling water from the engine cooling water flow path 38.
The cooling water outlet pipe 76 communicates with a substantially
vertical apex portion (a highest portion) of the outer pipe 36,
while the second cooling water inlet pipe 74 communicates with a
portion which constitutes a highest portion of the first cooling
water inlet pipe 70 which communicates with the outer pipe 36 in a
position which is slightly lower than a vertical apex portion
thereof and a portion which is higher than the highest portion of
the outer pipe 36. The second cooling water inlet pipe 74 and the
cooling water outlet pipe 76 are connected to a cooling water
circulation path which includes the engine 20, a radiator and a
heater core in such a manner as to become in series with the engine
20 at least along the flow of engine cooling water.
[0040] Thus, the exhaust system heat exchanger 15 is made to be a
counter flow heat exchanger in which the flow of exhaust gases is
opposite to the flow of engine cooling water, and in this
embodiment, due to a spiral flow of exhaust gases along the spiral
groove 30A being produced and a spiral flow of engine cooling water
along the spiral groove 30B which is opposite to the flow of
exhaust gases being produced, the exhaust system heat exchanger 15
is configured into an exhaust system heat exchanger which is
compact in size and which provides a high heat exchange efficiency.
In addition, in the exhaust system heat exchanger 15, the pressure
loss (back pressure) in exhaust gases due to the passage through
the bypass flow path 40 is sufficiently small relative to the
pressure loss in exhaust gases due to the passage through the
exhaust gas flow path 34, and exhaust gases are made to flow mainly
through the bypass flow path 40 when the valve 58 takes the open
position.
[0041] (Vehicle Exhaust System Structure)
[0042] As is shown in FIG. 1, in the vehicle exhaust system
structure 10, the first catalytic converter 12, the inter-catalytic
converter exhaust pipe 22, the second catalytic converter 14, the
catalytic converter to heat exchanger exhaust pipe 24 and the
exhaust system heat exchanger 15 are disposed substantially in a
straight line along the vehicle front-rear direction when seen in
plan view. In addition, as is shown in FIG. 2, in the side view,
the first catalytic converter 12 is disposed along the vehicle
vertical direction, and the second catalytic converter 14 and the
exhaust system heat exchanger 15 are both disposed slightly
inclined relative to a horizontal direction.
[0043] In addition, as is shown in FIG. 1, the first catalytic
converter 12, the inter-catalytic converter exhaust pipe 22, the
second catalytic converter 14, the catalytic converter to heat
exchanger exhaust pipe 24 and the exhaust system heat exchanger 15,
which are disposed substantially in the straight line when seen in
plan view as has been described above, are disposed substantially
in a central portion in the vehicle width direction. In addition,
the exhaust system heat exchanger 15 is disposed within a tunnel
portion T (in FIG. 1, a portion held between a pair of left and
right tunnel side reinforcements 82) which is formed in a floor of
the vehicle body B, so as to be protected from the interference
with road surface and flying gravels.
[0044] On the other hand, as is shown in FIG. 1, the muffler 16 is
disposed to be offset relative to the exhaust system heat exchanger
15 in the vehicle width direction. In this embodiment, the muffler
16 is disposed in parallel with a fuel tank 84 in the vehicle width
direction. Because of this, the heat exchanger to muffler exhaust
pipe 26 is made to constitute at its central portion (its main
part) an inclined portion 26A which extends in a direction
intersecting the vehicle front-rear direction (which is inclined
relative to the vehicle front-rear direction) when seen in plan
view. A rear end side of the heat exchanger to muffler exhaust pipe
26 is made to constitute a straight portion 26B which extends
substantially along the vehicle front-rear direction, and the
straight portion 26B is, as has been described above, fixed to the
muffler inlet pipe 16A of the muffler 16. Consequently, the vehicle
exhaust system structure 10 can be understood as a configuration in
which the inclined portion 26A is provided in the heat exchanger to
muffler exhaust pipe 26 in order to dispose the exhaust system 11
or the muffler 16 in such a manner as to go round the fuel tank
84.
[0045] In addition, in the vehicle exhaust system structure 10, the
first catalytic converter 12 is coupled directly to the exhaust
manifold 20A of the engine 20 as has been described above, and a
rear part of the exhaust system 11 which includes the exhaust
system heat exchanger 15 is supported on the vehicle body B by a
suspension unit 80. In this embodiment, in the exhaust system 11,
the exhaust system heat exchanger 15 is supported on the vehicle
body B by two support portions 86, 88 which both function as heat
recovery unit suspending portions, the muffler 16 is supported on
the vehicle body B by a support portion 90, and the downstream side
exhaust pipe 28 is supported on the vehicle body B by a support
portion 92. Specific description will be given below.
[0046] As is shown in FIG. 3, supported rods 86A, 88A, which
function as supported members which project in opposite directions
to each other in such a manner as to be substantially at right
angles to the longitudinal direction of the exhaust system heat
exchanger 15 when seen in plan view, are fixed to the exhaust gas
exhaust portion 30D which is an exposed portion to the outside of
the partition wall pipe 30 which makes up the exhaust system heat
exchanger 15. As is shown in FIG. 4, the exhaust gas exhaust
portion 30D of the partition wall pipe 30 is made to constitute a
single-sheeted portion which is exposed between the outer pipe 36
in an outer shell of the exhaust system heat exchanger 15 and the
end pipe 44. Namely, the supported rods 86A, 88A, which make up the
two support portions 86, 88, are both fixed to a low-rigidity
portion (a least rigid location) of the exhaust system heat
exchanger 15.
[0047] As is shown in FIG. 1, the support portion 86 suspends
(supports in a suspending fashion) the exhaust system heat
exchanger 15, which constitutes the component of largest mass in
the exhaust system 11, from the vehicle body B by causing a distal
end portion of the supported rod 86A to be inserted into a support
rubber 86C into which a support rod 86B fixed to the vehicle body B
is inserted in such a manner as to enable a longitudinal relative
displacement (absorption of thermal elongation). Similarly, the
support portion 88 suspends the exhaust system heat exchanger 15,
which constitutes the component of largest mass in the exhaust
system 11, from the vehicle body B by causing a distal end portion
of the supported rod 88A to be inserted into a support rubber 88C
into which a support rod 88B fixed to the vehicle body B is
inserted in such a manner as to enable a longitudinal relative
displacement. In this embodiment, the support rods 86B, 88B are
fixed to a body cross member 94 which straddles between the left
and right tunnel side reinforcements 82.
[0048] The support portion 90 has a supported rod 90A which is
fixed to a rear end 16D of a muffler shell 16C which makes up the
muffler 16 and which projects outwards in the vehicle width
direction. The supported rod 90A suspends (supports in a suspending
fashion) the muffler 16, which constitutes the component of
relatively large mass in the exhaust system 11, from the vehicle
body B by being inserted into a support rubber 90C into which a
support rod 90B fixed to the vehicle body B is inserted in such a
manner as to enable a longitudinal relative displacement
(absorption of thermal elongation). In addition, the support
portion 92 has a supported rod 92A which is fixed to a position on
the downstream side exhaust pipe 28 which lies in the vicinity of
the atmosphere release portion 18A and which projects outwards in
the vehicle width direction. The supported rod 92A suspends
(supports in a suspending fashion) the downstream side exhaust pipe
28, which makes up the exhaust pipe 18, from the vehicle body B by
being inserted into a support rubber 92C into which a support rod
92B fixed to the vehicle body B is inserted in such a manner as to
enable a longitudinal relative displacement (absorption of thermal
elongation).
[0049] Although the illustration is omitted, a configuration is
adopted in which the center of gravity of the exhaust system 11 is
situated inside an imaginary quadrangle which is formed by the four
support portions 86, 88, 90, 92 (the support rubbers 86C, 88C, 90C,
92C). In addition, in this embodiment, a configuration is adopted
in which the center of gravity of a portion of the exhaust system
11 which lies further downstream side than a ball joint 96 (which
will be described later) of the inter-catalytic converter exhaust
pipe 22 is situated inside the aforesaid imaginary quadrangle.
[0050] In addition, the vehicle exhaust system structure 10
includes ball joints 96, which function as vibration cut-off
mechanisms, which prevent the transmission of vibration of the
engine 20 (roll around an axis which is parallel to the crankshaft
20B) to the rear part of the exhaust system 11 which includes the
exhaust system heat exchanger 15. In this embodiment, ball joints
96 are provided, respectively, on the inter-catalytic converter
exhaust pipe 22 and the catalytic converter to heat exchanger
exhaust pipe 24, and are configured to permit a relative
displacement between a front portion 22A and a rear portion 22B of
the inter-catalytic converter exhaust pipe 22 and a relative
displacement between a front portion 24A and a rear portion 24B of
the catalytic converter to heat exchanger exhaust pipe 24.
[0051] More specifically, as is shown in FIG. 5A, in the ball
joints 96, gaskets 96D have spherical portions adapted to be
brought into slidable contact with the surfaces of spherical
portions 96C of second flanges 96B, which are provided on the rear
portions 22B and 24B of the inter-catalytic converter exhaust pipe
22 and the catalytic converter to heat exchanger exhaust pipe 24.
Gaskets 96D are disposed to be held between first flanges 96A,
which are provided on the front portions 22A and 24A of the
inter-catalytic converter exhaust pipe 22 and the catalytic
converter to heat exchanger exhaust pipe 24, and the second flanges
96B. As a result, the front portions 22A and 24A of the
inter-catalytic converter exhaust pipe 22 and the catalytic
converter to heat exchanger exhaust pipe 24, and the rear portions
22B and 24B of the inter-catalytic converter exhaust pipe 22 and
the catalytic converter to heat exchanger exhaust pipe 24, are
coupled in such a manner as to enable a relative angle displacement
around the center of the spherical portions 96C.
[0052] In addition, in the ball joint 96, the first flange 96A and
the second flange 96B are fastened together via springs 96E by
bolts 96F. As is shown in FIG. 5A, pairs of springs 96E and bolts
96F are provided in such a manner as to hold therebetween the
inter-catalytic converter exhaust pipe 22 and the catalytic
converter to heat exchanger exhaust pipe 24 in the vehicle width
direction, whereby the ball joints 96 are constructed to couple
together the front portions 22A, 24A of the inter-catalytic
converter exhaust pipe 22 and the catalytic converter to heat
exchanger exhaust pipe 24 and the rear portions 22B, 24B of the
inter-catalytic converter exhaust pipe 22 and the catalytic
converter to heat exchanger exhaust pipe 24 in such a manner to
allow a relative angle displacement in vehicle vertical directions
(refer to an arrow X in FIG. 5B).
[0053] Furthermore, as is shown in FIG. 3, in the vehicle exhaust
system structure 10, the heat exchanger rear portion shell 50,
which makes up the exhaust system heat exchanger 15, has a
projecting portion 50C which projects further in a direction in
which the inclined portion 26A of the heat exchanger to muffler
exhaust pipe 26 extends than an end surface 50B thereof in the
vehicle width direction and is joined to an upstream end 26C of the
heat exchanger to muffler exhaust pipe 26 (the inclined portion
26A) at a projecting end 50D of the projecting portion 50C through
welding. Namely, a welded joint Wp between the projecting end 50D
and the upstream end 26C lies offset in the vehicle width direction
relative to the straight line formed by the first catalytic
converter 12, the inter-catalytic converter exhaust pipe 22, the
second catalytic converter 14, the catalytic converter to heat
exchanger exhaust pipe 24 and the exhaust system heat exchanger 15
when seen in plan view. In addition, in the vehicle exhaust system
structure 10, the heat exchanger rear portion shell 50 which makes
up the exhaust system heat exchanger 15 makes up the bend portion
18B of the exhaust pipe 18 together with the inclined portion 26A
of the heat exchanger to muffler exhaust pipe 26.
[0054] In order to form this projecting portion 50C, the heat
exchanger rear portion shell 50 is made up by joining together a
half body 98 which constitutes one side in the vehicle width
direction and a half body 99 which constitutes the other side, and
the projecting portion 50C is formed integrally on the half body 98
through, for example, drawing. Consequently, the projecting portion
50C is formed substantially into a cone shape in which the
cross-sectional area of its flow path is gradually reduced towards
the projecting end 50D which has substantially the same diameter as
that of the heat exchanger to muffler exhaust pipe 26.
[0055] Next, the operation of the embodiment will be described.
[0056] In the exhaust system 11 to which the vehicle exhaust system
structure 10 of the aforementioned configuration is applied,
exhaust gases produced in association with the running of the
engine 20 are purified, made silent, and released into the
atmosphere via the first catalytic converter 12, the second
catalytic converter 14, the exhaust system heat exchanger 15 and
the muffler 16 which are made to communicate with each other
through the exhaust pipe 18. In addition, in the exhaust system
heat exchanger 15, if the temperature of engine cooling water is
low, the valve 58 is made free relative to the thermoactuator 72,
whereby the valve device 54 functions as a self-pressurizing valve.
Because of this, under running conditions of low exhaust gas
pressure, the exhaust gas guide pipe 42, that is, the bypass flow
path 40, is closed by virtue of the biasing force of the return
spring 66, and exhaust gases are made to flow through the exhaust
gas flow path 34 in the heat exchange portion 15A, so as to
implement a heat exchange with the engine cooling water which is
flowing through the engine cooling water flow path 38. Thereby,
warming up of the engine 20 can be promoted, and heating can be
maintained, when starting a vehicle in low-temperature
conditions.
[0057] For example, in a running condition in which the output of
the engine 20 is increased for acceleration or climbing, when the
pressure of exhaust gases is increased, the valve 58 which receives
the pressure of the exhaust gases rotates in the direction
indicated by the arrow A against the biasing force of the return
spring 66 to reach the open position, whereby exhaust gases flow
mainly through the bypass flow path 40, and the back pressure is
reduced compared with the case in which exhaust gases flow through
the exhaust gas flow path 34. Namely, in the vehicle exhaust system
structure 10 which includes the valve device 54 which functions as
the self-pressurizing valve, when the reduction in back pressure to
secure the output of the engine 20 takes priority over the recovery
of exhaust heat to warm up or the like the engine 20, exhaust gases
bypass the heat exchange portion 15A to flow through the bypass
flow path 40, whereby the back pressure is reduced automatically.
In addition, when the engine 20 produces its maximum output, the
valve 58 is caused to take the open position which is indicated by
the imaginary lines in FIG. 4 by the pressure of exhaust gases (is
opened to its maximum opening by the pressure of exhaust
gases).
[0058] In addition, in the vehicle exhaust system structure 10,
when the temperature of engine cooling water reaches or exceeds
80.degree. C., the thermoactuator 72 imparts a torque which can
resist the biasing force of the return spring 66 to the rotational
shaft 56, so as to hold the valve 58 in the full open position,
whereby exhaust gases are caused to flow mainly through the bypass
flow path 40 and are then discharged from the exhaust pipe 18 by
way of the exhaust gas guide pipe 42 and the exhaust gas exit
header 52 of the heat exchanger rear portion shell 50. Namely, in
the running condition in which the recovery of exhaust heat is not
necessary, the exhaust gas flow path is automatically switched to
the bypass flow path 40.
[0059] Incidentally, in the engine 20 which is transversely
installed in the front part of the vehicle body B, rolling
vibration (refer to an arrow R in FIG. 2) around an axis parallel
to the crankshaft 20B is generated, and vibration like this tends
to generate twist or bend in the inclined portion 26A of the heat
exchanger to muffler exhaust pipe 26 which makes up the bend
portion 18B of the exhaust pipe 18, the welded joint Wp which is
the joint portion between the inclined portion 26A and the heat
exchanger rear portion shell 50, or the like.
[0060] Here, in the vehicle exhaust system structure 10, since the
ball joint 96 is provided in the catalytic converter to heat
exchanger exhaust pipe 24, the transmission of rolling vibration of
the engine 20 to the inclined portion 26A of the heat exchanger to
muffler exhaust pipe 26 is prevented. In particular, since the ball
joint 96 is made to permit the relative displacement in the vehicle
vertical direction between the front portion 24A and the rear
portion 24B of the catalytic converter to heat exchanger exhaust
pipe 24 and the first catalytic converter 12, the inter-catalytic
converter exhaust pipe 22, the second catalytic converter 14, the
catalytic converter to heat exchanger exhaust pipe 24 and the
exhaust system heat exchanger 15, which constitute a vibration
transmission path from the engine 20, are disposed substantially in
the straight line when seen in plan view, the transmission of
rolling vibration of the engine 20 to the heat exchanger to muffler
exhaust pipe 26 side is suppressed effectively.
[0061] Namely, in the vehicle exhaust system structure 10, the
first catalytic converter 12, the inter-catalytic converter exhaust
pipe 22, the second catalytic converter 14, the catalytic converter
to heat exchanger exhaust pipe 24 and the exhaust system heat
exchanger 15 are disposed in a straight line along the vehicle
front-rear direction when seen in plan view, and since load or
forced displacement associated with the rolling vibration of the
engine 20 acts mainly along a plane orthogonal to the vehicle width
direction (a vehicle width direction component is small), the load
or forced displacement can effectively be cut off (absorbed) by the
ball joint 96.
[0062] In addition, in the vehicle exhaust system structure 10, by
providing the ball joint 96 on the catalytic converter to heat
exchanger exhaust pipe 24, a distance between the ball joint 96 and
the frontmost support portions 86, 88 in the suspension unit 80
which support the exhaust system 11 is set to be short. Because of
this, the ball joint 96 can be installed with good accuracy in a
neutral position, thereby making it possible to exhibit well the
vibration cut-off effect by the ball joint 96.
[0063] Furthermore, in the vehicle exhaust system structure 10, by
providing the ball joint on the catalytic converter to heat
exchanger exhaust pipe 24, the length of the exhaust system 11 that
is supported on the vehicle body B by the suspension system 80 (the
vibration system made up by the exhaust system 11) can be made
short in appearance. Specifically, since the portion (downstream
side) of the exhaust system 11 which lies further rearwards in the
vehicle front-rear direction than the ball joint 96 (the second
flange 96B) provided on the catalytic converter to heat exchanger
exhaust pipe 24 can be understood as the vibration system which is
independent from the front-side portion of the exhaust system 11,
the resonance frequency of the vibration system that is supported
by the suspension system 80 of the exhaust system 11 becomes high,
whereby the strengths against rolling resonance of the engine 20 of
the inclined portion 26A of the catalytic converter to muffler
exhaust pipe 26 which makes up the bend portion 18B of the exhaust
system 11 and the welded joint Wp which is the joint portion
between the inclined portion 26A and the heat exchanger rear
portion shell 50 are increased.
[0064] On the other hand, in the vehicle exhaust system structure
10, since the ball joint 96 is also provided on the inter-catalytic
converter exhaust pipe 22, the transmission of rolling vibration of
the engine 20 to the heat exchanger to muffler exhaust pipe 26 side
is suppressed more effectively. Namely, in case the second ball
joint 96 is provided on the heat exchanger to muffler exhaust pipe
26 or the downstream side exhaust pipe 28, the ball joint 96 is
disposed between the support portions 86, 88 and the support
portion 90 or between the support portion 90 and the support
portion 92, that is, between the portions restrained by the
suspension unit 80, and this causes a fear that the action of the
ball joint 96 is interrupted. In contrast to this, in the vehicle
exhaust system structure 10, since the ball joint 96 is disposed on
the inter-catalytic converter exhaust pipe 22, in other words,
since the two ball joints 96 are disposed between the first
catalytic converter 12 which is restrained by the engine 20 and the
frontmost support portions 86, 88 of the suspension unit 80, both
the two ball joints 96 are allowed to exhibit the required
vibration cut-off effect.
[0065] In addition, since the ball joints 96 are provided both
upstream and downstream of the second catalytic converter 14, the
joint portion between the second catalytic converter 14 and the
inter-catalytic converter exhaust pipe 22 is protected against the
rolling vibration of the engine 20. In case a configuration is
adopted in which no ball joint 96 is provided on the
inter-catalytic converter exhaust pipe 22, since the first
catalytic converter 12 to which an upstream end of the
inter-catalytic converter exhaust pipe 22 is connected is fixed to
the engine 20, there is caused a fear that vibration associated
with the action of the ball joint 96 provided on the catalytic
converter to heat exchanger exhaust pipe 24 applies high stress to
the joint portion between the inter-catalytic converter exhaust
pipe 22 and the second catalytic converter 14. In contrast to this,
in the vehicle exhaust system structure 10, since the second
catalytic converter 14 is supported (or made free) in such a manner
as to be displaced relative to the front and rear restraining
portions (the engine 20, the suspension unit 80) by providing the
ball joint 96 on the inter-catalytic converter exhaust pipe 22, the
joint portion between the inter-catalytic converter exhaust pipe 22
and the second catalytic converter 14 is protected.
[0066] Furthermore, in the vehicle exhaust system structure 10,
since the frontmost support portions 86, 88, which make up the
suspension unit 80, are fixed to the exhaust gas exhaust portion
30D of the partition wall pipe 30 which constitutes the
low-rigidity portion of the exhaust system heat exchanger 15, the
exhaust system heat exchanger 15 performs an oscillating action
(around the exhaust gas exhaust portion 30D serving as a fulcrum)
due to the elastic deformation of the exhaust gas exhaust portion
30D of the partition wall pipe 30 where the supported rods 86A, 88A
are fixed in association with the vibration cut-off action of the
ball joint 96. Because of this, the displacement of the downstream
portion (the rear portion) of the exhaust system heat exchanger 15
in association with the vibration cut-off action of the ball joint
96 is suppressed, and the transmission of the displacement
(vibration) to the heat exchanger to muffler exhaust pipe 26 is
suppressed, whereby in particular, an input of twist of the
inclined portion 26A of the heat exchanger to muffler exhaust pipe
26 is suppressed effectively.
[0067] Furthermore, in the vehicle exhaust system structure 10,
since the heat exchanger rear portion shell 50, which makes up the
exhaust system heat exchanger 15, makes up the bend portion 18B of
the exhaust pipe 18 together with the inclined portion 26A of the
heat exchanger to muffler exhaust pipe 26, the cross-sectional area
of the bend portion 18B of the exhaust pipe 18 is larger at the
heat exchanger rear portion shell 50 than the other portion (a
straight-line portion of the exhaust pipe 18), and hence, is strong
against bend and twist. Moreover, since the projecting portion 50C
provided on the heat exchanger rear portion shell 50 gradually
decreases its cross-sectional area towards the inclined portion
26A, a portion where the cross-section is changed drastically and
hence stress is easily concentrated is not formed, whereby an
excessively large stress is prevented from being applied to the
bend portion 18B. Furthermore, since the projecting portion 50C
projects further than the end surface 50B of the heat exchanger
rear portion shell 50 in the vehicle width direction, in other
words, since the welded joint Wp between the projecting end 50D of
the projecting portion 50C and the upstream end 26C of the heat
exchanger to muffler exhaust pipe 26 is spaced apart in the vehicle
width direction from the rear end portion of the exhaust system
heat exchanger 15 which constitutes a twist and/or bend input
portion, stress that is applied to the welded joint Wp can be
decreased.
[0068] To describe this point more specifically, it has been
confirmed through a numerical analysis that in the event that a
vibration mode is generated, as is shown in FIG. 6A, for example,
in which the ball joint 96 of the catalytic converter to heat
exchanger exhaust pipe 24 is deviated in the vehicle width
direction with a specific frequency, a deformation mode of the
exhaust pipe 18 occurs as is also shown in FIG. 6B in which the
heat exchanger to muffler exhaust pipe 26 is displaced in such a
manner as to push the muffler 16 rearwards without imparting an
excessively large bend to the bend portion 18B. In addition, it has
been confirmed through a numerical analysis that in the event that
a vibration mode is generated, as is shown in FIG. 7A, in which the
ball joint 96 of the catalytic converter to heat exchanger exhaust
pipe 24 is deviated obliquely rearwards with another specific
frequency, a deformation mode of the exhaust pipe 18 occurs as is
also shown in FIG. 7B in which the heat exchanger to muffler
exhaust pipe 26 is displaced in such a manner as to push the
muffler 16 rearwards without imparting an excessively large bend to
the bend portion 18B. Namely, it has been confirmed analytically
that by causing the heat exchanger rear portion shell 50 to make up
at least part of the bend portion 18B in the exhaust system 11 to
which the vehicle exhaust system structure 10 is applied, stress
that would otherwise be applied to the bend portion 18B of the
exhaust pipe 18 and the welded joint Wp can be suppressed.
[0069] As a result of the configuration that has been described
heretofore, in a motor vehicle which includes the exhaust system 11
to which the vehicle exhaust system structure 10 is applied, the
exhaust system 11 can be laid out while avoiding the interference
of the fuel tank 84 with the configuration in which the exhaust
heat exchanger 15 is disposed in a limited space underneath the
vehicle body. In addition, the exhaust system 11 which includes the
exhaust heat exchanger 15 of large mass can be supported on the
vehicle body B by the suspension unit 80 with the small number of
constituent components or at the small number of support points,
and the bend portion 18B can be protected well by decreasing the
stress applied to the bend portion 18B by the rolling of the engine
20, whereby by applying the vehicle exhaust system structure 10 to
the exhaust system 11, the exhaust system 11 disposing the exhaust
system heat exchanger 15 and avoiding the interference of the fuel
tank 84 can be provided on, for example, a small front-engine front
drive vehicle with a transverse engine.
[0070] Note that while in the aforesaid embodiment, the example is
described in which the exhaust system 11 which includes the exhaust
system heat exchanger 15 is supported on the vehicle body by the
vehicle exhaust system structure 10, the invention is not limited
thereto, and hence, the invention can also be applied to exhaust
systems having various types of exhaust system heat exchangers.
[0071] In addition, while in the aforementioned embodiment, the
example is described in which the ball joint 96 is provided on the
inter-catalytic converter exhaust pipe 22, the invention is not
limited thereto, and hence, for example, in a configuration in
which the second catalytic converter 14 is supported on the engine
20 via a bracket or the like, the necessity of the ball joint 96 on
the inter-catalytic converter exhaust pipe 22 can be obviated.
[0072] Furthermore, while in the embodiment above, the example is
described in which the suspension unit 80 includes the four support
portions 86, 88, 90, 92, the invention is not limited thereto, and
hence, for example, the exhaust system 11 may be made to be
supported by three support portions.
[0073] In addition, while in the embodiment above, the example is
described in which the ball joint 96 is provided on the catalytic
converter to heat exchanger exhaust pipe 24 and the supported rods
86A, 88A of the suspension unit 80 are fixed to the exhaust gas
exhaust portion 30D of the partition wall pipe 30, the invention is
not limited thereto, and hence, the invention may be configured to
include only either of the aforesaid two characteristic
configurations.
[0074] The invention provides a vehicle exhaust system structure
which can protect well a bend portion of an exhaust pipe.
[0075] A first aspect of the present invention provides a vehicle
exhaust system structure for discharging exhaust gases of an
internal combustion engine, which is transversely installed in a
front part of a vehicle body, from a rear part of the vehicle body,
the vehicle exhaust system structure comprising: a first catalytic
device, a second catalytic device, an exhaust heat recovery unit
and a silencer which are disposed sequentially in that order from
an upstream side in an exhaust gas flow direction; a first exhaust
pipe which connects the second catalytic device to the exhaust heat
recovery unit; a second exhaust pipe which includes a portion
extending in a direction intersecting a vehicle front-rear
direction, and which connects the exhaust heat recovery unit, which
is disposed to be offset in a vehicle width direction, to the
silencer; a suspension unit which suspends at least part of the
exhaust system elements including the exhaust heat recovery unit,
the second exhaust pipe, and the silencer, relative to the vehicle
body, on a downstream side in an exhaust gas flow direction
relative to the first exhaust pipe; and a vibration cut-off
mechanism which is provided at the first exhaust pipe and permits a
relative displacement between the second catalytic device and the
exhaust heat recovery unit.
[0076] According to the above-described aspect, exhaust gases
discharged from the internal combustion engine flow from the front
part towards the rear part of the vehicle body through the first
catalytic device, the second catalytic device, the exhaust heat
recovery unit and the silencer in that order so as to be discharged
to the atmosphere. Since the transversely installed internal
combustion engine rolls around an axis along the vehicle width
direction, a portion (a bend portion) of the second exhaust pipe of
the exhaust system supported on the vehicle body by the suspension
unit which extends in a direction intersecting a vehicle front-rear
direction is subject to twist or bend (load or forced
displacement), but the twist or bend is suppressed (absorbed) by
the vibration cut-off mechanism. Here, the portion which is
situated further upstream in the exhaust gas flow direction than
the vibration cut-off mechanism can be understood as a portion (a
vibration system) which is isolated from a supported portion on the
vehicle body by the suspension unit. In addition, in the vehicle
exhaust system structure, since the vibration cut-off mechanism is
provided at the first exhaust pipe disposed between the second
catalytic device and the exhaust heat recovery unit, the vibration
system of the exhaust system which is supported on the vehicle body
by the suspension unit is configured to be short (light), whereby
the resonance frequency can be increased, thereby making it
possible to increase the strength of the second exhaust pipe having
the bend portion or the joint portion (the welded joint or the
like) between the exhaust pipe and an exhaust system component
against resonance attributed to the vibration of the internal
combustion engine.
[0077] According to the above-described aspect, the bend portion of
the exhaust pipe can be protected well.
[0078] In the above-described aspect, the first catalytic device,
the second catalytic device, the first exhaust pipe and the exhaust
heat recovery unit may be disposed linearly along a vehicle
front-rear direction when seen in plan view, the vibration cut-off
mechanism may be configured such that a front portion and a rear
portion of the first exhaust pipe in the vehicle front-rear
direction may be displaced relative to each other in a vehicle
vertical direction.
[0079] According to the above-described aspect, in order to permit
the relative displacement in the vehicle vertical direction between
the front portion and rear portion of the first exhaust pipe, the
vibration cut-off mechanism can suppress effectively the
transmission of roll of the transverse internal combustion engine
to the bend portion of the second exhaust pipe.
[0080] In the above-described aspect, the suspension unit may have
a heat recovery unit suspending portion which suspends the exhaust
heat recovery unit relative to the vehicle body, and which is at a
position furthest upstream in an exhaust gas flow direction, and
the heat recovery unit suspending portion may include a supported
member which is fixed to a low-rigidity portion of the exhaust heat
recovery unit.
[0081] According to the above-described aspect, the heat recovery
unit suspending portion which includes the supported member which
is fixed to the low-rigidity portion which is lower in rigidity
(easier to be deformed) than the other portions of the exhaust heat
recovery unit constitutes the suspending portion of the suspension
unit which is at a position furthest upstream in the exhaust gas
flow direction and is disposed closest to the vibration cut-off
mechanism. Because of this, displacement generated in the vibration
cut-off mechanism is absorbed by deformation in the low-rigidity
portion of the exhaust heat recovery unit, whereby the transmission
of load or forced displacement associated with the rolling of the
internal combustion engine to the second exhaust pipe (the bend
portion) which is situated further downstream in the exhaust gas
flow direction than the exhaust heat recovery unit is suppressed,
thereby the strength of the bend portion against resonance being
increased further.
[0082] In the above-described aspect, a vibration cut-off mechanism
which permits a relative displacement between the first catalytic
device and the second catalytic device may further be provided.
[0083] According to the above-described aspect, at least two
vibration cut-off mechanisms are disposed in such a manner as to
hold therebetween the second catalytic device in the exhaust gas
flow direction. Namely, at least two vibration cut-off mechanisms
are disposed between the internal combustion engine and the bend
portion of the second exhaust pipe, so that the transmission of
load or forced displacement associated with the rolling of the
internal combustion engine to the bend portion of the second
exhaust pipe is suppressed, and the strength of the bend portion
against the resonance is increased further. In addition, since the
two vibration cut-off mechanisms are disposed further upstream in
the exhaust gas flow direction than the position where the exhaust
system is supported by the suspension unit, the interruption of
vibration cut-off operations of the vibration cut-off mechanisms by
the suspension unit is suppressed.
[0084] In the above-described aspect, a bend portion of the second
exhaust pipe may be made up of a shell which is formed at one end
of the exhaust heat recovery unit, and an inclined portion of the
second exhaust pipe which extends in a direction intersecting the
vehicle front-rear direction.
[0085] According to the above-described aspect, since the
cross-sectional area of the bend portion of the second exhaust pipe
is larger in the shell than that of the other portion (a
straight-line portion of the exhaust pipe), the strength against
bend or twist can be increased.
[0086] In the above-described aspect, the shell may include a
projecting portion which projects in a direction in which the
inclined portion extends, further than an end surface of the shell
in a vehicle width direction.
[0087] According to the above-described aspect, since a welded
joint between a projecting end of the projecting portion and an
upstream end of the second exhaust pipe is spaced apart in the
vehicle width direction from a rear end portion of the exhaust heat
recovery unit which constitutes a portion where twist or bend is
inputted, stress applied to the welded joint can be reduced.
[0088] A second aspect of the present invention provides a vehicle
exhaust system structure for discharging exhaust gases of an
internal combustion engine, which is transversely installed in a
front part of a vehicle body, from a rear part of the vehicle body,
the vehicle exhaust system structure comprising: a first catalytic
device, a second catalytic device, an exhaust heat recovery unit
and a silencer which are disposed sequentially in that order from
an upstream side in an exhaust gas flow direction; an exhaust pipe
which includes a portion extending in a direction intersecting a
vehicle front-rear direction, and which connects the exhaust heat
recovery unit, which is disposed to be offset in a vehicle width
direction, to the silencer; a vibration cut-off mechanism which
permits a relative displacement between the first catalytic device
and the second catalytic device, or a relative displacement between
the second catalytic device and the exhaust heat recovery unit; and
a suspension unit which includes a supported member which is fixed
to a low-rigidity portion of the exhaust heat recovery unit and a
support member which supports the supported member on the vehicle
body.
[0089] According to the above-described aspect, exhaust gases
discharged from the internal combustion engine flow from the front
part towards the rear part of the vehicle body through the first
catalytic device, the second catalytic device, the exhaust heat
recovery unit and the silencer in that order so as to be discharged
to the atmosphere. Since the transversely installed internal
combustion engine rolls around an axis along the vehicle width
direction, a portion (a bend portion) of the exhaust pipe of the
exhaust system supported on the vehicle body by the suspension unit
which extends in a direction intersecting a vehicle front-rear
direction is subject to twist or bend (load or forced
displacement), but the twist or bend is suppressed (absorbed) by
the vibration cut-off mechanism. Here, in the vehicle exhaust
system structure, in the exhaust system including the exhaust heat
recovery unit, since the supported member fixed to the low-rigidity
portion of the exhaust heat recovery unit is supported on the
vehicle body via the support member, displacement generated in the
vibration cut-off mechanism is absorbed by the deformation of the
low-rigidity portion of the exhaust heat recovery unit. Because of
this, the transmission of load or forced displacement associated
with the rolling of the internal combustion engine to the bend
portion of the exhaust pipe which is situated further downstream in
the exhaust gas flow direction than the exhaust heat recovery unit
is suppressed, thereby making it possible to increase the strength
of the exhaust pipe having the bend portion or the joint portion
(the welded joint or the like) between the exhaust pipe and an
exhaust system component against resonance attributed to the
vibration of the internal combustion engine.
[0090] According to the above-described aspect, the bend portion of
the exhaust pipe can be protected well.
[0091] In the above-described aspect, a bend portion of the exhaust
pipe may be made up of a shell which is formed at one end of the
exhaust heat recovery unit, and an inclined portion of the exhaust
pipe which extends in a direction intersecting the vehicle
front-rear direction.
[0092] According to the above-described aspect, since the
cross-sectional area of the bend portion of the exhaust pipe is
larger in the shell than that of the other portion (a straight-line
portion of the exhaust pipe), the strength against bend or twist
can be increased.
[0093] In the above-described aspect, the shell may include a
projecting portion which projects in a direction in which the
inclined portion extends, further than an end surface of the shell
in a vehicle width direction.
[0094] According to the above-described aspect, since a welded
joint between a projecting end of the projecting portion and an
upstream end of the exhaust pipe is spaced apart in the vehicle
width direction from a rear end portion of the exhaust heat
recovery unit which constitutes a portion where twist or bend is
inputted, stress applied to the welded joint can be reduced.
[0095] As has been described heretofore, the vehicle exhaust system
structure according to the invention has an effect that the bend
portion of the exhaust pipe can be protected well.
[0096] The foregoing description of the exemplary embodiment of the
present invention has been provided for the purposes of
illustration and description. It is not intended to be exhaustive
or to limit the invention to the precise forms disclosed.
Obviously, many modifications and variations will be apparent to
practitioners skilled in the art. The exemplary embodiments were
chosen and described in order to best explain the principles of the
invention and its practical application, thereby enabling others
skilled in the art to understand the invention for various
embodiments and with the various modifications as are suited to the
particular use contemplated. It is intended that the scope of the
invention be defined by the following claims and their
equivalents.
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