U.S. patent application number 15/660292 was filed with the patent office on 2018-02-01 for egr device for internal combustion engine.
The applicant listed for this patent is HONDA MOTOR CO., LTD.. Invention is credited to Keita Hashimoto, Kazuya Miyoshi.
Application Number | 20180030876 15/660292 |
Document ID | / |
Family ID | 60951430 |
Filed Date | 2018-02-01 |
United States Patent
Application |
20180030876 |
Kind Code |
A1 |
Miyoshi; Kazuya ; et
al. |
February 1, 2018 |
EGR DEVICE FOR INTERNAL COMBUSTION ENGINE
Abstract
Provided is an EGR device that allows an EGR valve to be removed
with ease even when the EGR valve is provided adjacent to a
turbocharger. The EGR device includes a first connecting pipe
portion (41b) extending from a compressor of the turbocharger and
having a first annular shoulder surface (41c) at a base end
thereof, an EGR valve (65) fixedly attached to a part of the
engine, a joint member (71) including a flange (71a) attached to
the EGR valve (65) and a second connecting pipe portion (71b), and
opposing the first connecting pipe portion in a coaxial
relationship, the second connecting pipe portion being provided
with a second annular shoulder surface (71c) at a base end thereof,
and a flexible pipe member (72) having a first end fitted onto the
first connecting pipe portion and a second end fitted onto the
second connecting pipe portion. A distance (L2) between the two
annular shoulder surfaces is greater than a length (L1) of the
flexible pipe member by a prescribed distance.
Inventors: |
Miyoshi; Kazuya; (Wako-shi,
JP) ; Hashimoto; Keita; (Minato-ku, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HONDA MOTOR CO., LTD. |
Tokyo |
|
JP |
|
|
Family ID: |
60951430 |
Appl. No.: |
15/660292 |
Filed: |
July 26, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01N 13/1811 20130101;
Y02T 10/12 20130101; Y02T 10/20 20130101; F01N 3/021 20130101; F02M
26/51 20160201; F01N 3/08 20130101; F02M 26/06 20160201; F02M 26/15
20160201; F02M 26/12 20160201; F01N 13/1855 20130101; F02M 26/21
20160201 |
International
Class: |
F01N 13/18 20060101
F01N013/18; F01N 3/08 20060101 F01N003/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 2016 |
JP |
2016149698 |
Claims
1. An EGR device for a multiple-cylinder engine equipped with a
supercharger for returning a part of exhaust gas expelled from an
exhaust system of the engine to an intake system of the engine,
comprising: a first connecting pipe portion extending from a
compressor of the supercharger and having a first annular shoulder
surface at a base end thereof; an EGR valve fixedly attached to a
part of the engine; a joint member including a flange attached to
the EGR valve and a second connecting pipe portion defining a
passage communicating with an inlet end of the EGR valve, and
opposing the first connecting pipe portion in a coaxial
relationship, the second connecting pipe portion being provided
with a second annular shoulder surface at a base end thereof; and a
flexible pipe member having a first end fitted onto the first
connecting pipe portion and a second end fitted onto the second
connecting pipe portion; wherein a distance between the two annular
shoulder surfaces is greater than a length of the flexible pipe
member by a prescribed distance.
2. The EGR device according to claim 1, wherein the supercharger
consists of a turbocharger including a turbine for powering the
compressor and attached to a part of the engine such that the
compressor projects from an exhaust side part of the engine beyond
a cylinder row end part of the engine, and the first connecting
pipe portion, the EGR valve, the flexible pipe member and the
second connecting pipe portion extend from the compressor along the
cylinder row end part of the engine.
3. The EGR device according to claim 2, further comprising an
upstream EGR pipe assembly communicating a part of the exhaust
system to the inlet end of the EGR valve, the upstream EGR pipe
assembly including a part extending generally vertically along the
cylinder row end part of the engine toward a downstream part of the
exhaust system of the engine.
4. The EGR device according to claim 3, wherein an exhaust gas
purification device is positioned on an exhaust side of the engine
under the turbine, and an upstream end of the upstream EGR pipe
assembly is connected to a downstream part of the exhaust gas
purification device.
5. The EGR device according to claim 4, wherein the upstream EGR
pipe assembly extends generally upward from the upstream end
thereof between the engine and the exhaust gas purification device,
and along the cylinder row end part of the engine toward the intake
side of the engine before doubling back toward the exhaust side of
the engine and being connected to the inlet end of the EGR
valve.
6. The EGR device according to claim 5, wherein the upstream EGR
pipe assembly comprises an EGR cooler.
7. The EGR device according to claim 6, wherein the upstream EGR
pipe assembly includes a rigid pipe member connected between the
EGR cooler and the EGR valve.
8. The EGR device according to claim 7, wherein a plurality of
threaded bolts are passed through a flange provided on a downstream
end of the rigid pipe member of the upstream EGR pipe assembly, the
EGR valve and the joint member to fasten these components to one
another.
9. The EGR device according to claim 8, wherein the threaded bolts
include at least a pair of stud bolts each having a base end
threaded into one of the flange of the rigid pipe member and the
flange of the joint member, and a free end having a threaded
portion having a nut fastened thereon.
10. The EGR device according to claim 9, wherein the free end of
each stud bolt is provided with a tool engagement feature.
11. The EGR device according to claim 9, wherein the threaded
portion on the free end of each stud bolt is provided with a length
at least twice as long as a thickness of the nut.
12. The EGR device according to claim 9, wherein a first gasket is
interposed between the flange of the rigid pipe member of the
upstream EGR pipe assembly and the EGR valve, and a second gasket
is interposed between the EGR valve and the joint member, and
wherein the distance between the two annular shoulder surfaces is
greater than the length of the flexible pipe member at least by a
combined thickness of the two gaskets in an unused state.
13. The EGR device according to claim 9, wherein each end of the
flexible pipe member is secured onto the corresponding connecting
pipe portion with a hose band.
Description
TECHNICAL FIELD
[0001] The present invention relates to an EGR (exhaust gas
recirculation) device for an internal combustion engine equipped
with a supercharger such as a turbocharger.
BACKGROUND ART
[0002] In a known EGR device for an internal combustion engine, an
EGR valve is attached to a cylinder row end of a cylinder head, and
internally defines a part of an exhaust gas passage that extends
from an exhaust system. The upstream end of the exhaust gas passage
is connected to a converging part of an exhaust manifold via an
exhaust gas introduction pipe, and the downstream end of the
exhaust gas passage is connected to an intake passage of an intake
manifold via an exhaust gas injection pipe. See JP2000-87807A, for
instance.
[0003] An engine is often equipped with a supercharger such as a
turbocharger for the purpose of improving fuel economy. A
turbocharger supplies compressed air into the combustion chambers
of the engine so that the volumetric efficiency is improved and a
high engine input can be obtained for the given engine displacement
of the engine. In an engine equipped with a turbocharger, both a
high-pressure EGR device that recirculates the high-pressure
exhaust gas in an upstream part of the exhaust system to the intake
air under high pressure, and a low-pressure EGR device that
recirculates the low-pressure exhaust gas in a downstream part of
the exhaust system to the intake air under negative pressure are
employed at the same time. As a result, the structure of the intake
system and the exhaust system tends to be highly complex owing to
the presence of these EGR devices. To allow a compact design of the
intake system and the exhaust system, it is a common practice to
place at least one of the EGR valves adjacent to the
turbocharger.
[0004] When an EGR valve is positioned adjacent to a turbocharger,
because the associated piping and other components bunch up around
the turbocharger, it becomes difficult to remove the EGR valve for
maintenance purpose. Oftentimes, it is necessary to remove the
turbocharger itself to remove or replace the EGR valve.
[0005] The present invention was made in view of such problems of
the prior art, and has a primary object to provide an EGR device
that allows an EGR valve to be removed with ease even when the EGR
valve is provided adjacent to a supercharger.
[0006] To achieve such an object, the present invention provides a
An EGR device for a multiple-cylinder engine equipped with a
supercharger (41) for returning a part of exhaust gas expelled from
an exhaust system of the engine to an intake system of the engine,
comprising: a first connecting pipe portion (41b) extending from a
compressor of the supercharger and having a first annular shoulder
surface (41c) at a base end thereof; an EGR valve (65) fixedly
attached to a part of the engine; a joint member (71) including a
flange (71a) attached to the EGR valve (65) and a second connecting
pipe portion (71b) defining a passage communicating with an inlet
end of the EGR valve, and opposing the first connecting pipe
portion in a coaxial relationship, the second connecting pipe
portion being provided with a second annular shoulder surface (71c)
at a base end thereof; and a flexible pipe member (72) having a
first end fitted onto the first connecting pipe portion and a
second end fitted onto the second connecting pipe portion; wherein
a distance (L2) between the two annular shoulder surfaces is
greater than a length (L1) of the flexible pipe member by a
prescribed distance.
[0007] According to this arrangement, by moving the joint member
(optionally along with the flexible pipe member) in the axial
direction away from the EGR valve, the EGR valve can be removed
without requiring any major components such as the supercharger to
be removed. The axial movement of the joint member is permitted
until the two ends of the flexible pipe member abut the respective
annular shoulder surfaces.
[0008] In a preferred embodiment of the present invention, the
supercharger consists of a turbocharger including a turbine for
powering the compressor and attached to a part of the engine such
that the compressor projects from an exhaust side part of the
engine beyond a cylinder row end part of the engine, and the first
connecting pipe portion (41b), the EGR valve (65), the flexible
pipe member (72) and the second connecting pipe portion (71b)
extend from the compressor along the cylinder row end part of the
engine.
[0009] Thereby, the EGR device can be installed in an area
adjoining the main body of the engine in a highly compact
manner.
[0010] The EGR device may further comprises an upstream EGR pipe
assembly (62-64) communicating a part of the exhaust system to the
inlet end of the EGR valve, the upstream EGR pipe assembly (62-64)
including a part generally extending vertically along the cylinder
row end part of the engine toward a downstream part of the exhaust
system of the engine.
[0011] This also contributes to the compact arrangement of the EGR
device.
[0012] Preferably, an exhaust gas purification device is positioned
on an exhaust side of the engine under the turbine, and an upstream
end of the upstream EGR pipe assembly is connected to a downstream
part of the exhaust gas purification device.
[0013] Thereby, the low-pressure exhaust gas having a relatively
low temperature is returned to the intake system of the engine, and
is mixed with the intake air under negative pressure. The exhaust
gas contains moisture of a certain acidity, but the acidity of the
exhaust gas is reduced by the catalytic converter before being
returned to the intake system. Therefore, the thermal degradation
of the flexible pipe member can be minimized.
[0014] According to a preferred embodiment of the present
invention, the upstream EGR pipe assembly extends generally upward
from the upstream end thereof between the engine and the exhaust
gas purification device, and along the cylinder row end part of the
engine toward the intake side of the engine before doubling back
toward the exhaust side of the engine and being connected to the
inlet end of the EGR valve.
[0015] This also contributes to the compact arrangement of the EGR
device.
[0016] The upstream EGR pipe assembly may comprise an EGR cooler
(63).
[0017] Thereby, the temperature of the exhaust gas conducted to the
flexible pipe member can be lowered by the EGR cooler so that the
thermal degradation of the flexible pipe member can be
minimized.
[0018] The upstream EGR pipe assembly may include a rigid pipe
member (64) connected between the EGR cooler and the EGR valve.
[0019] The rigid pipe member may be fixedly attached to a suitable
part of the engine so that the EGR valve (on the downstream end of
the rigid pipe member) and the EGR cooler (on the upstream end of
the rigid pipe member) can be fixedly secured to the engine in a
highly stable manner without requiring additional brackets.
[0020] In a particularly preferred embodiment of the present
invention, a plurality of threaded bolts (81, 82) are passed
through a flange (64b) provided on a downstream end of the rigid
pipe member of the upstream EGR pipe assembly, the EGR valve (65)
and the joint member (71) to fasten these components to one
another.
[0021] Thereby, the EGR valve and the joint member can be fixedly
secured to the rigid pipe member of the upstream EGR pipe assembly
in a both simple and stable manner.
[0022] Preferably, the threaded bolts include at least a pair of
stud bolts each having a base end threaded into one of the flange
(64b) of the rigid pipe member and the flange (71a) of the joint
member, and a free end having a threaded portion having a nut (83)
fastened thereon.
[0023] Thereby, the rigid pipe member, the EGR valve and the joint
member can be assembled together in a proper alignment with one
another with the aid of the stud bolts so that the assembly work
can be facilitated. Typically, a gasket is required to be placed
between each interface, but this arrangement allows the assembly
process to be carried out in a highly efficient manner.
[0024] Typically, the free end of each stud bolt is provided with a
tool engagement feature (81a). Thereby, each stud bolt can be
installed and removed with ease by engaging a suitable tool with
the tool engagement feature.
[0025] Alternatively or additionally, the threaded portion on the
free end of each stud bolt may be provided with a length at least
twice as long as a thickness of the nut. Thereby, by threading an
additional nut (84) until the additional nut abuts the original nut
(a double nut arrangement), the stud bolt can be unscrewed from the
flange of the rigid pipe member or the flange of the joint member
(as the case may be) by engaging the original nut with a suitable
tool.
[0026] In a preferred embodiment of the present invention, a first
gasket (68) is interposed between the flange of the rigid pipe
member of the upstream EGR pipe assembly and the EGR valve, and a
second gasket (69) is interposed between the EGR valve and the
joint member, and wherein the distance (L2) between the two annular
shoulder surfaces is greater than the length of the flexible pipe
member (L1) at least by a combined thickness of the two gaskets in
an unused state.
[0027] According to this arrangement, adequate spaces can be
created between the flange of the rigid pipe member of the upstream
EGR pipe assembly and the EGR valve, and between the EGR valve and
the joint member so that the replacement of the EGR valve can be
accomplished without causing any difficulty.
[0028] Each end of the flexible pipe member may be secured onto the
corresponding connecting pipe portion with a hose band.
[0029] Thereby, the flexible pipe member can be installed in a both
simple and economical manner.
BRIEF DESCRIPTION OF THE DRAWING(S)
[0030] FIG. 1 is a plan view of an engine of a motor vehicle
equipped with an EGR device embodying the present invention;
[0031] FIG. 2 is a block diagram of an intake system and an exhaust
system of the engine;
[0032] FIG. 3 is a fragmentary perspective view of a low-pressure
EGR device shown in FIG. 2;
[0033] FIG. 4 is a fragmentary sectional view of a part of the
low-pressure EGR device;
[0034] FIG. 5 is an exploded perspective view of a part of the
low-pressure EGR device; and
[0035] FIG. 6 is a view similar to FIG. 4 when the low-pressure EGR
device is being disassembled.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0036] An embodiment of the present invention is described in the
following with reference to the appended drawings. An engine 4
consisting of an in-line four-cylinder diesel engine is positioned
in an engine room 3 formed in a front part of a vehicle body 2 of a
motor vehicle 1.
[0037] The engine 4 is laterally mounted in the engine room 3, and
slightly offset in the rightward direction. The engine 4 is
supported by the vehicle body 2 via an engine mount (not shown in
the drawings) with a slight rearward slant. A transmission system
is connected to a lower side of a left end part of the engine 4. A
pair of front side frames 6 (only one of them is shown in FIG. 1)
extend along either side of the engine room 3, and a pair of damper
bases 7 are positioned on either side of a rear end part of the
engine room 3.
[0038] A rectangular battery 8 is positioned on an inboard side of
the left damper base 7 with the long side of the battery 8
extending in the fore and aft direction. An ECU unit 9 for
controlling various parts of the vehicle 1 is provided immediately
ahead of the battery 8, and an air cleaner 10 is positioned
immediately ahead of the ECU unit 9. A relay box 11 which is
elongate in the fore and aft direction is positioned on the
outboard side of the battery 8.
[0039] A front bulkhead (not shown in the drawings) supporting a
radiator (not shown in the drawings) is provided in a front end
part of the engine room 3. A cover member 12 is positioned on top
of the front bulkhead. The engine 4 is provided with an
intake/exhaust system 18 consisting of an intake system 20 for
supplying air to the engine 4 and an exhaust system 30 for
expelling exhaust gas from the engine 4. The exhaust system 30 is
provided with a turbocharger 40 which is powered by the flow of the
exhaust gas and compresses the intake air supplied to the engine 4.
A high-pressure EGR device 50 is provided in a downstream part of
the turbocharger 40, and a low-pressure EGR device 60 is provided
in an upstream part of the turbocharger 40, each for returning a
controlled amount of the exhaust gas to the intake system 20.
[0040] FIG. 2 is a block diagram illustrating the overall structure
of the intake/exhaust system 18. In the intake system 20, air drawn
from the atmosphere is introduced into a first intake duct 21 via
an intake inlet 21a, and is then conducted to a throttle valve 23
via an air cleaner 10 and a second intake duct 22. Then, after
being compressed by a compressor 41 of the turbocharger 40, the
intake air is forwarded to an intercooler 25 via a third intake
duct 24, and to an intake manifold 29 via a fourth intake duct 26,
an intake shutter valve 27 and a fifth intake duct 28.
[0041] In the exhaust system 30, the exhaust gas collected from the
engine 4 by an exhaust manifold 31 is forwarded to a turbine 42 of
the turbocharger 40, and is expelled to the atmosphere via a first
exhaust pipe 32, a catalytic converter 33, a DPF 34, and a second
exhaust pipe 35. The high-pressure EGR device 50 includes a first
high-pressure EGR pipe 51 directly connected to the exhaust
manifold 31, a high-pressure EGR valve 52, and a second
high-pressure EGR pipe 53 connected to the downstream side of the
intake shutter valve 27, in this order from the side of the exhaust
system 30. The low-pressure EGR device 60 includes an EGR filter
device 61 connected to the DPF 34, a first low-pressure EGR pipe
62, a low-pressure EGR cooler 63, a second low-pressure EGR pipe
64, a low-pressure EGR valve 65, and a third low-pressure EGR pipe
66 connected to the downstream side of the throttle valve 23, in
this order from the side of the exhaust system 30.
[0042] The throttle valve 23 controls the intake air amount and the
intake pressure of the intake air supplied into the cylinders of
the engine 4. The intake shutter valve 27 is configured to
selectively reduce the intake air amount by narrowing the intake
passage at the valve body to raise the temperature of the exhaust
gas when the DPF is required to be regenerated by burning off the
particulate matter (PM) collected by the DPF 34, but is otherwise
kept fully open.
[0043] The first low-pressure EGR pipe 62, the low-pressure EGR
cooler 63, and the second low-pressure EGR pipe 64 on the upstream
side of the low-pressure EGR valve 65 may be collectively referred
to as an upstream EGR pipe assembly. In the illustrated embodiment,
the second low-pressure EGR pipe 64 forms a part of the upstream
EGR pipe assembly.
[0044] Referring to FIG. 1 once again, exhaust ports of the engine
4 are provided on the front side of the engine 4. An exhaust
converging pipe 36 is attached to a planar mounting surface defined
on the front side of the engine 4, and communicates with the
exhaust manifold 31 which, in the illustrated embodiment, is
internally defined in the cylinder head of the engine 4. The
exhaust manifold may also be provided separately from the engine
and attached to the front side of the engine 4. The outlet end of
the exhaust converging pipe 36 is positioned on the left end side
of the engine 4, and is fitted with the turbine 42 of the
turbocharger 40.
[0045] The turbine 42 is positioned on the front side of the
exhaust converging pipe 36, and is provided with a turbine housing
and a turbine wheel rotatably supported by the turbine housing
around a rotational center line extending in the lateral direction
of the vehicle body. The turbine housing defines a turbine inlet
extending circumferentially along a tangential direction of the
turbine housing, and a turbine inlet extending in the axial
direction from a central part of the turbine housing in the
rightward direction. The turbine inlet is connected to the outlet
end of the exhaust converging pipe 36, and the turbine outlet is
connected to the first exhaust pipe 32 connected to the right side
wall of the turbine housing.
[0046] The first exhaust pipe 32 curves downward as it extends
rightward, and is connected to an upper part of the catalytic
converter 33 provided under the turbine 42 in a forwardly spaced
apart relationship to the exhaust side (the front side) of the
engine 4. The catalytic converter 33 removes HC, CO and NOx from
the exhaust gas. The DPF 34 (FIG. 2) for trapping particulates from
the exhaust gas is provided under the catalytic converter 33. The
second exhaust pipe 35 (FIG. 2) is connected to the lower side of
the DPF 34, and extends under the engine 4 in the rearward
direction. The second exhaust pipe 35 further extends under the
floor to a rear end part of the vehicle.
[0047] The air cleaner 10 is connected to the downstream end of the
first intake duct 21 (FIG. 2) so that the air drawn into the engine
room 3 via a front grill is forwarded to the air cleaner 10 via the
intake inlet 21a. An intake outlet is formed on the right side of
the air cleaner 10, and is connected to the upstream end of the
second intake duct 22. The downstream end of the second intake duct
22 is connected to the left end of the throttle valve 23 which
internally defines a laterally extending intake passage.
[0048] The compressor 41 of the turbocharger 40 is positioned
between the throttle valve 23 and the turbine 42 so as to be
coaxial with the turbine 42 and projects beyond the left end of the
engine 4. The compressor 41 includes a compressor housing 41a (FIG.
4) and a compressor wheel rotatably supported by the compressor
housing 41a around a laterally extending rotational center line.
The compressor housing 41a is provided with a compressor inlet
provided centrally on the left side wall of the compressor housing
41a, and a low-pressure EGR introduction port opens out and
projects from a rear side of the peripheral wall of the compressor
housing 41a. The compressor housing 41a is further provided with a
compressor outlet extending tangentially from a lower part of the
outer peripheral wall of the compressor housing 41a. The compressor
inlet is connected to the intake passage of the throttle valve 23,
and the low-pressure EGR introduction port is connected to the EGR
gas passage of the low-pressure EGR device 60. The compressor
outlet is connected to the intake passage of the third intake duct
24 connected to the lower wall of the compressor housing 41a.
[0049] The turbocharger 40 is provided with a drive shaft 40a (FIG.
2) connecting the turbine wheel on the side of the exhaust system
30 to the compressor wheel on the side of the intake system 20. The
rotational power of the turbine wheel is transmitted to the
compressor wheel via the drive shaft 40a. Thereby, the turbocharger
40 compresses the intake air supplied from the throttle valve 23
and the exhaust gas supplied from the low-pressure EGR device 60,
and forwards the mixture at a pressure higher than the atmospheric
pressure to the engine 4.
[0050] The third intake duct 24 connected to the lower part of the
outer periphery of the compressor 41 is connected to the
intercooler 25 (FIG. 2) positioned under the cover member 12. The
fourth intake duct 26 (FIG. 2) is passed behind the engine 4 via
the intercooler 25, and is connected to the intake manifold 29
(FIG. 2) attached to the rear side of the engine 4.
[0051] The first high-pressure EGR pipe 51 of the high-pressure EGR
device 50 is connected to the right end of the exhaust converging
pipe 36 and receives the exhaust gas from the exhaust converging
pipe 36. The high-pressure EGR valve 52 is attached to the front
side of the cylinder head, and the rear end of the first
high-pressure EGR pipe 51 is attached to the front end of the
high-pressure EGR valve 52. In the cylinder head of the engine 4,
an upstream side passage portion of the second high-pressure EGR
pipe 53 (FIG. 2) communicating with the EGR passage of the
high-pressure EGR valve 52 is formed so as to extend in the fore
and aft direction. The downstream side passage portion of the
second high-pressure EGR pipe 53 connected to the rear surface of
the engine 4 is connected to the intake introduction portion of the
intake manifold 29 and causes the exhaust gas having passed through
the high-pressure EGR valve 52 to return to the intake system 20.
The downstream side passage portion of the second high-pressure EGR
pipe 53 may be connected to a portion other than the intake
manifold 29 as long as it is on the downstream side of the
compressor 41 in the intake system 20 and on the upstream side of
the intake introduction portion.
[0052] As shown in FIG. 3, the first low-pressure EGR pipe 62 that
extends vertically includes a first upstream flange 62a disposed at
the lower end thereof and fastened to the lower end of the DPF 34
with threaded bolts, and a first downstream flange 62b disposed at
the upper end thereof. The first low-pressure EGR pipe 62 extends
rightward from the first upstream flange 62a, and then curves
upward to extend along the right side of the DPF 34 before
extending obliquely upward and rearward. The first upstream flange
62a generally faces to the left, and the first downstream flange
62b faces obliquely upward and rearward. The lower portion of the
vertical section of the first low-pressure EGR pipe 62 is formed as
a flexible pipe or a bellows 62c. As a result, the first upstream
flange 62a and the first downstream flange 62b can be displaced
relative to each other, and stress concentration in the first
low-pressure EGR pipe 62 due to thermal expansion of the exhaust
system 30 can be avoided.
[0053] The EGR filter device 61 consists of a metallic mesh
interposed between the first upstream flange 62a of the first
low-pressure EGR pipe 62 and a connecting flange (not shown in the
drawings) of the DPF 34. The EGR filter device 61 captures
fragments of the DPF 34 and other metallic pieces that might be
introduced into the first low-pressure EGR pipe 62.
[0054] The low-pressure EGR cooler 63 is provided with a
rectangular cooler main body portion 63a having a laterally
elongated cross section and a smaller fore and aft dimension than a
vertical dimension. A right end part of the cooler main body
portion 63a is integrally provided with an upstream side connecting
pipe portion 63b extending obliquely downward and forward, and a
left end part of the cooler main body portion 63a is integrally
provided with a downstream side connecting pipe portion 63c
extending to the front. Connecting flanges are integrally formed at
the free ends of the upstream side connecting pipe portion 63b and
the downstream side connecting pipe portion 63c, respectively. The
cooler main body portion 63a is provided with a plurality of
mounting pieces 63d for attachment to the engine 4. The cooler main
body portion 63a is positioned between the engine 4 and the
catalytic converter 33 which is spaced from the front side of the
engine 4, and is attached to the front side of the engine 4 via the
mounting pieces 63d and associated threaded bolts. The cooler main
body portion 63a is configured to circulate the cooling water
therein, and cool the exhaust gas by heat exchange between the
cooling water flowing through the cooler main body portion 63a and
the exhaust gas.
[0055] The second low-pressure EGR pipe 64 is made of a rigid pipe
member, and includes a second upstream flange 64a positioned at the
lower end thereof and fastened to the downstream side connecting
pipe portion 63c of the low-pressure EGR cooler 63 by threaded
bolts, and a second downstream flange 64b positioned at the upper
end thereof. The second low-pressure EGR pipe 64 extends from the
second upstream flange 64a forward and then toward the left end
side of the engine 4 in an upward and leftward direction along a
curved path. The second low-pressure EGR pipe 64 is bent again
along the left end side of the engine 4 in the rearward direction
(toward the intake side). The second low-pressure EGR pipe 64 is
then bent upward and forward (toward the exhaust side) making a U
turn. In other words, the downstream part of the second
low-pressure EGR pipe 64 extends rearward along the cylinder row
end part of the engine toward the intake side of the engine, and
then doubles back toward the exhaust side of the engine. The second
low-pressure EGR pipe 64 is made of metal, and is therefore highly
rigid (as opposed to a flexible tube). A connecting piece 64d for
attachment to the engine 4 is provided at an appropriate position
of the second low-pressure EGR pipe 64. The second low-pressure EGR
pipe 64 is fixed to the engine 4 via a pipe stay 64e (which is
attached to a left end surface of the engine 4) by fastening the
connecting piece 64d to the pipe stay 64e with a threaded bolt.
[0056] FIG. 4 is a longitudinal sectional view of the third
low-pressure EGR pipe 66 and the EGR valve 65 which form an
essential part of the low-pressure EGR device 60, and FIG. 5 is an
exploded perspective view of the third low-pressure EGR pipe 66 and
associated parts. As shown in FIGS. 3 and 4, a compressor
connecting pipe portion 41b extends rearward from the rear surface
of the rear wall portion of the compressor housing 41a of the
compressor 41. The base end of the compressor connecting pipe
portion 41b is formed with an annular shoulder surface 41c facing
rearward. The annular shoulder surface 41c protrudes rearward from
the surrounding surface of the rear wall portion of the compressor
housing 41a by a prescribed distance in the illustrated embodiment,
but may also be defined by a part of the surface of the rear wall
portion itself surrounding the compressor connecting pipe portion
41b.
[0057] The third low-pressure EGR pipe 66 includes a joint member
71 positioned on the downstream side of the low-pressure EGR valve
65, a flexible pipe member 72, and a pair of hose bands 73 provided
on either axial end of the flexible pipe member 72. As shown in
FIGS. 4 and 5, the joint member 71 includes a joint flange portion
71a and a joint connecting pipe portion 71b extending forward
toward the free end of the compressor connecting pipe portion 41b.
The joint connecting pipe portion 71b is provided with an annular
shoulder surface 71c facing forward so as to face the annular
shoulder surface 41c in a coaxial relationship. The annular
shoulder surface 71c protrudes forward from the forwardly facing
surface of the joint flange portion 71a by a certain distance in
the illustrated embodiment, but may also be defined by a part of
the forwardly facing surface of the joint flange portion 71a
surrounding the joint connecting pipe portion 71b. The joint flange
portion 71a is provided with three bolt holes 70, one centrally in
an upper part and two on either lower side part of the joint flange
portion 71a.
[0058] The low-pressure EGR valve 65 includes a valve housing 65a
defining a low-pressure EGR passage extending in the front and aft
direction, and a disk-shaped butterfly valve 65d rotatably
supported in the valve housing 65a for opening and closing the
low-pressure EGR passage defined in the valve housing 65a. The two
axial ends of the valve housing 65a define mutually parallel mating
surfaces facing in the fore and aft direction. Three bolt holes 65b
extending in the axial direction are passed through respective
thick-walled portions 65c formed on the outer peripheral parts of
the valve housing 65a at a regular angular interval in such a
manner that the three bolt holes 65b align with the respective bolt
holes 70 of the joint flange portion 71a.
[0059] The second downstream flange 64b of the second low-pressure
EGR pipe 64 opposes the compressor connecting pipe portion 41b in a
coaxial relationship from the rear and at a certain distance. The
second downstream flange 64b is provided with three bolt holes 64c,
one centrally in an upper part and two on either lower side part of
the second downstream flange 64b. One of the axial end surfaces
(the rear axial end surface) of the valve housing 65a is joined to
the second downstream flange 64b of the second low-pressure EGR
pipe 64 via a first gasket 68, and the other axial end surface (the
front axial end surface) of the valve housing 65a is joined to the
joint flange portion 71a of the joint member 71.
[0060] The bolt holes 70 of the joint flange portion 71a consist of
female threaded holes passed through the joint flange portion 71a.
A threaded bolt 82 having a threaded part at one end and a
hexagonal head at the other end is passed through one of the bolt
holes 64c (the lower right bolt hole 64c) of the second downstream
flange 64b and the corresponding bolt hole 65b formed in the
thick-walled portions 65c of the valve housing 65a, and threaded
into the corresponding bolt hole 70 of the joint flange portion
71a. A stud bolt 81 (threaded bolt) having a threaded part at each
end is passed through each of the remaining two bolt holes 64c (the
upper bolt hole 64c and the lower left bolt hole 64c) of the second
downstream flange 64b and the corresponding bolt hole 65b formed in
the thick-walled portion 65c of the valve housing 65a, and threaded
into the corresponding bolt hole 70 of the joint flange portion
71a. A nut 83 is threaded onto the threaded portion of each stud
bolt 82 projecting rearward from second downstream flange 64b.
[0061] As a result, the second downstream flange 64b of the second
low-pressure EGR pipe 64, the low-pressure EGR valve 65 and the
joint flange portion 71a of the joint member 71 are fastened
together with the first gasket 68 and the second gasket 69 placed
in the interfaces between these three parts. Thus, the fasteners
consisting of the threaded bolt 82, the stud bolts 81 and the nuts
83 detachably join the second low-pressure EGR pipe 64, the
low-pressure EGR valve 65 and the joint member 71 to one
another.
[0062] When the second downstream flange 64b and the low-pressure
EGR valve 65 are jointly fastened to the joint flange portion 71a,
the length of the threaded part of each stud bolt 81 protruding
from the outer (rear) surface of the second downstream flange 64b
is at least twice the thickness of the nut 83 so that an additional
nut 84 (indicated by imaginary lines), in addition to the nut 83,
can be threaded onto the protruding part of the stud bolt 81. A
tool engaging feature 81a for engaging a tool is formed at the free
end of the stud bolt 81. In the illustrated embodiment, the tool
engaging feature 81a is formed as a projection having a hexagonal
cross section. Alternatively, the tool engaging feature 81a may
consist of a projection having any other non-circular cross
section, or a non-circular recess as long as it can be used for
turning the stud bolt 81 around the central axial line thereof.
[0063] The flexible pipe member 72 is made of an elastic material
such as synthetic rubber, natural rubber and elastomer (such as
urethane rubber and silicone rubber), and is elastically deformable
in the lateral direction and the axial direction. The flexible pipe
member 72 is disposed between the joint member 71 and the
compressor 41, and has an upstream side end portion 72a fitted over
the joint connecting pipe portion 71b and a downstream side end
portion 72b fitted over the compressor connecting pipe portion 41b.
A pair of annular protrusions 72c are formed on the outer
peripheral surfaces of the upstream side end portion 72a and the
downstream side end portion 72b of the flexible pipe member 72,
respectively, for preventing the axial misalignment of the hose
bands 73. Each pair of annular protrusions 72c are spaced apart
from each other by a distance slightly greater than the width of
the hose band 73.
[0064] Each hose band 73 may consist of a per se known hose band,
and the circumferential length thereof can be adjusted, for
example, by using a fastening arrangement (not shown) such as a
screw. The hose bands 73 clamp the upstream side end portion 72a
and the downstream side end portion 72b of the flexible pipe member
72 onto the compressor connecting pipe portion 41b and the joint
connecting pipe portion 71b, respectively, to achieve an air tight
connection at these two parts.
[0065] When exhaust gas flows through the low-pressure EGR device
60, the second low-pressure EGR pipe 64 and the low-pressure EGR
valve 65 are heated, and thermally expand. The flexible pipe member
72 absorbs expansion and contraction of these members, and prevents
stress concentration owing to the thermal expansion.
[0066] In particular, the length L1 of the flexible pipe member 72
is shorter than the distance L2 between the annular shoulder
surface 41c on the side of the compressor 41 and the annular
shoulder surface 71c on the side of the joint member 71 opposing
each other in a state where the low-pressure EGR device 60 is not
at a high temperature (a state where maintenance work can be
performed). As a result, the axial end surfaces of the flexible
pipe member 72 are spaced from the corresponding annular shoulder
surfaces 41c and 71c by a combined spacing G. In the illustrated
example, the corresponding end of the flexible pipe member 72 abuts
the annular shoulder surface 71c so that a space L3 (=L2-L1) is
created between the annular shoulder surface 41c and the front end
surface of the flexible pipe member 72.
[0067] The dimension L3 of the gap G is selected such that the
first gasket 68 and the second gasket 69 both in an unused state
(yet to be compressed) can be inserted between the low-pressure EGR
valve 65 and the second low-pressure EGR pipe 64, and between the
low-pressure EGR valve 65 and the joint member 71, respectively.
More specifically, if the thickness of the first gasket 68 is t1
and the thickness of the second gasket 68 is t2, the dimension L3
is greater than the sum of these thicknesses by a certain margin a
corresponding to the combined amount of compression of the two
gaskets 68 and 69 (L3>t1+t2+.alpha.). The thickness of the
gasket in an unused state accounts for the thickness of the beads
and the warping of the gasket. Therefore, when the stud bolts 81
and the threaded bolt 82 are unfastened, and the hose bands 73 for
the flexible pipe member 72 are loosened, it is possible to insert
the two gaskets 68 and 69 between the low-pressure EGR valve 65 and
the second low-pressure EGR pipe 64, and between the low-pressure
EGR valve 65 and the joint member 71, respectively.
[0068] The assembling process for the low-pressure EGR device 60 is
described in the following.
[0069] As shown in FIG. 3, when installing the low-pressure EGR
device 60, the low-pressure EGR cooler 63 to which the first
low-pressure EGR pipe 62 is connected is attached to the engine 4
via the mounting pieces 63d. Next, the second upstream flange 64a
of the second low-pressure EGR pipe 64 is connected to the
downstream side connecting pipe portion 63c of the low-pressure EGR
cooler 63, and the second low-pressure EGR pipe 64 is attached to
the engine 4 via the connecting piece 64d. Since the second
low-pressure EGR pipe 64 is fixed to the engine 4, the supporting
rigidity thereof is high and the two stud bolts 81 are also held in
a stable condition. As shown in FIG. 5, the two stud bolts 81 are
fastened to the joint member 71 in advance so that the two stud
bolts 81 extend rearward from the joint flange portion 71a of the
joint member 71.
[0070] Thereafter, the two stud bolts 81 are passed into the
through holes of the second gasket 69 to temporarily assemble the
first gaskets 68 to the joint member 71. Subsequently, the two stud
bolts 81 are passed into the bolt holes 65b of the low-pressure EGR
valve 65 to temporarily assemble the low-pressure EGR valve 65 to
the joint member 71. Since the two stud bolts 81 are provided in
the upper portion and the lower left portion of the second upstream
flange 64a, the position of the low-pressure EGR valve 65 in the
directions perpendicular to the axial line of the joint member 71
is correctly determined.
[0071] Thereafter, the two stud bolts 81 are passed into the
through holes of the first gasket 68 to temporarily assemble the
second gasket 69 to the joint member 71. As a result, the first
gasket 68, the low-pressure EGR valve 65, the second gasket 69, and
the joint member 71 are in a temporarily assembled state so that
the relative position in the direction perpendicular to the axial
line is correctly determined in a stable manner. Subsequently,
while holding this assembly together, the two stud bolts 81 are
passed into the bolt holes 64c of the second low-pressure EGR pipe
64, and the two nuts 83 are threaded onto the stud bolts 81 so that
the assembly is pressed onto the second downstream flange 64b. The
nuts 83 are only loosely tightened at this time. In this state, the
low-pressure EGR valve 65 and the joint member 71 are suspended by
the second low-pressure EGR pipe 64 via the stud bolts 81 in a
stable condition. Thereafter, the threaded bolt 82 having the
hexagonal head is passed through the bolt holes of these members
from behind, and threaded into the bolt hole 70 of the joint member
71. The two nuts 83 and the bolt 82 with a hexagonal head are
tightened one after the other so that the second low-pressure EGR
pipe 64, the low-pressure EGR valve 65 and the joint member 71 are
finally assembled together.
[0072] Thereafter, as shown in FIGS. 3 and 4, the upstream side end
portion 72a of the flexible pipe member 72 having the hose band 73
loosely thereof is fitted onto the joint connecting pipe portion
71b, and the corresponding axial end of the flexible pipe member 72
is brought into contact with the annular shoulder surface 71c. The
hose band 73 is tightened at this position so that the flexible
pipe member 72 is connected to the joint connecting pipe portion
71b in an air tight manner.
[0073] Thereafter, to assemble the turbocharger 40 to the engine 4,
the compressor connecting pipe portion 41b is inserted into the
downstream side end portion 72b of the flexible pipe member 72, and
the turbocharger 40 is fixedly attached to the engine 4 at
appropriate positions. As a result, a gap G having a dimension L3
is created between the annular shoulder surface 41c and the front
end surface of the joint member 71. Finally, the hose band 73 on
the downstream side is tightened to connect the downstream side end
portion 72b of the flexible pipe member 72 to the compressor
connecting pipe portion 41b in an air tight manner. This concludes
the assembly of the low-pressure EGR device 60 to the engine 4.
[0074] Thereafter, the catalytic converter 33 and the DPF 34 are
connected to the downstream side of the turbine 42. This can be
accomplished without being obstructed by the low-pressure EGR
device 60. Further, the first upstream flange 62a of the first
low-pressure EGR pipe 62 is connected to the lower end of the DPF
34. Since the lower portion of the first low-pressure EGR pipe 62
is configured as a bellows 62c, stress concentration in the first
low-pressure EGR pipe 62 due to thermal expansion of the exhaust
system 30 can be avoided.
[0075] The disassembling process for the low-pressure EGR device 60
for maintenance and other purposes is described in the
following.
[0076] First of all, as shown in FIGS. 4 and 5, the hose band 73 on
the downstream side is loosened, and the two nuts 83 and the bolt
82 are loosened. As a result, the joint member 71 and the flexible
pipe member 72 can be moved toward the side of the compressor 41 so
that the gap G is created. Subsequently, the bolt 82 is pulled out
rearward. The stud bolts 81 are loosened each by engaging the tool
engaging feature 81a with a suitable tool, and are pulled out
rearward. If any of the stud bolts 81 is firmly lodged in the
threaded hole of the joint flange portion 71a and cannot be turned,
the additional nut 84 may be threaded onto the stud bolt 81 in
addition to the original nut 83 so that the two nuts 83 and 84
become locked onto the stud bolt 81. Then, the original nut 83 may
be engaged by a spanner or any suitable tool, and is turned in the
counter-clockwise direction. Since the effective diameter of the
nut 83 is larger than that of the tool engaging feature 81a, a
larger torque can be applied to the stud bolt 81.
[0077] Once the stud bolts 81 and the bolt 82 are removed, the
low-pressure EGR valve 65 can be removed by sliding the
low-pressure EGR valve 65 upward or leftward. If a high frictional
resistance is encountered when sliding the low-pressure EGR valve
65 upward or leftward, the joint member 71 and the flexible pipe
member 72 may be moved until the flexible pipe member 72 abuts
against the annular shoulder surface 41c. As a result, the distance
between the second downstream flange 64b and the joint member 71 is
increased so that the low-pressure EGR valve 65 can be relatively
easily slid off. Therefore, the subsequent work of reinstalling the
low-pressure EGR valve 65 or installing a new low-pressure EGR
valve 65 can be facilitated.
[0078] As described above, the dimension L3 of the gap G is
selected such that the first gasket 68 and the second gasket 69 in
an unused state can be inserted between the low-pressure EGR valve
65 and the second low-pressure EGR pipe 64 and between the
low-pressure EGR valve 65 and the joint member 71. More
specifically, as shown in FIG. 6, with the low-pressure EGR valve
65 installed in the designated position, a gap t3 greater than the
thickness of the first gasket 68 in the unused state is created
between the low-pressure EGR valve 65 and the second low-pressure
EGR pipe 64, and a gap t4 greater than the second gasket 69 in the
unused state is created between the low-pressure EGR valve 65 and
the joint member 71. Therefore, the first gasket 68 and the second
gasket 69 can be installed in the designated positions after the
low-pressure EGR valve 65 is installed without any difficulty.
Thereafter, the remaining parts of the low-pressure EGR valve 65
and the associated parts can be assembled by reversing the order of
disassembly discussed earlier.
[0079] According to the low-pressure EGR device 60 constructed as
described above, the following advantages can be obtained. As shown
in FIG. 4, the inlet end of the low-pressure EGR valve 65 is
detachably connected to the second downstream flange 64b of the
second low-pressure EGR pipe 64, and the free end of the compressor
connecting pipe portion 41b is detachably connected to the outlet
end of the low-pressure EGR valve 65. The flexible pipe member 72
connected to the compressor connecting pipe portion 41b and the
joint connecting pipe portion 71b by the hose bands 73 has a length
L1 smaller than the distance L2 between the annular shoulder
surface 41c and the annular shoulder surface 71c. Therefore, a gap
G is created between the flexible pipe member 72 and the annular
shoulder surface 41c. As a result, the flexible pipe member 72 and
the joint member 71 can be axially moved toward the side of the
compressor 41 until the flexible pipe member 72 abuts against the
annular shoulder surface 41c so that the low-pressure EGR valve 65
can be easily removed without removing the compressor 41.
[0080] As shown in FIGS. 1, 3 and 4, the compressor 41 is provided
so as to protrude beyond the left end of the engine 4, and the
second downstream flange 64b of the second low-pressure EGR pipe
64, the low-pressure EGR valve 65, the joint connecting pipe
portion 71b, the flexible pipe member 72 and the compressor
connecting pipe portion 41b are arranged in the fore and aft
direction along the left side of the engine 4. Therefore, the
low-pressure EGR device 60 can be arranged in a compact manner
adjacent to the engine 4.
[0081] As shown in FIGS. 2 and 3, the first upstream flange 62a of
the first low-pressure EGR pipe 62 is connected to a portion of the
exhaust system 30 on the downstream side of the catalytic converter
33, and the compressor connecting pipe portion 41b is connected to
the upstream side of the compressor 41. Therefore, the exhaust gas
contains moisture with a certain acidity, but the acidity of the
exhaust gas is weakened as the exhaust gas passes through the
catalytic converter 33 before the exhaust gas is recirculated to
the intake air of the intake system 20 under negative pressure via
the low-pressure EGR device 60. Therefore, deterioration of the
flexible pipe member 72 that could be caused by the acidity can be
minimized.
[0082] As shown in FIG. 3, the low-pressure EGR device 60 includes
the low-pressure EGR cooler 63 fixedly attached to the engine 4 and
disposed between the engine 4 and the catalytic converter 33. In
terms of the flow of the exhaust gas, the low-pressure EGR cooler
63 is provided with an intermediate part of the path of the exhaust
gas or between the first low-pressure EGR pipe 62 and the second
low-pressure EGR pipe 64. The low-pressure EGR device 60 extends
from the first upstream flange 62a to the left side of the engine 4
through a space defined between the engine 4 and the catalytic
converter 33. The low-pressure EGR device 60 then extends toward
the intake side of the engine 4 along the left side of the engine,
and curves upward to be bent back toward the exhaust side of the
engine 4. Therefore, the temperature of the exhaust gas flowing
through the flexible pipe member 72 is lowered as the exhaust gas
flows along this path so that the thermal degradation of the
flexible pipe member 72 is minimized. Furthermore, the low-pressure
EGR device 60 can be arranged in a highly compact manner by making
use of the space defined between the engine 4 and the catalytic
converter 33.
[0083] The second low-pressure EGR pipe 64 connecting the
low-pressure EGR cooler 63 to the low-pressure EGR valve 65 is made
of a rigid member and fixed to the engine 4. Therefore, the support
rigidity of the second low-pressure EGR pipe 64 is very high. This
facilitates the work of installing and removing the low-pressure
EGR valve 65, and also eliminates the need to remove or install the
low-pressure EGR cooler 63 when removing the low-pressure EGR valve
65 so that the need for the work involved in removing and filling
cooling water for the low-pressure EGR cooler 63 can be
eliminated.
[0084] As shown in FIGS. 4 and 5, as a fastening means for
detachably fastening the second low-pressure EGR pipe 64, the
low-pressure EGR valve 65, and the joint member 71 having the joint
connecting pipe portion 71b, at least one stud bolt 81 (more
preferably at least two stud bolts) each penetrating the EGR valve
65 having a base end threaded into the joint member 71 is used. The
free end of the stud bolt 81 is provided with a threaded position
and the nut 83 is threaded thereon. Therefore, the low-pressure EGR
valve 65 and the joint member 71 can be temporarily assembled to
the second low-pressure EGR pipe 64 making use of the stud bolt 81
so that the assembling of the the low-pressure EGR device 60 is
facilitated. In the illustrated embodiment, two stud bolts 81 are
used as fastening means. Therefore, the relative position of the
low-pressure EGR valve 65 in the direction perpendicular to the
joint member 71 with respect to the joint member 71 is correctly
determined while the EGR valve 65 and the joint member 71 are being
temporarily assembled so that the assembling the low-pressure EGR
device 60 is facilitated even further.
[0085] In the illustrated embodiment, the base end of each stud
bolt 81 is screwed into the joint flange portion 71a of the joint
member 71, but may also be threaded into or otherwise detachably
fastened to the second downstream flange 64b of the second
low-pressure EGR pipe 64.
[0086] As shown in FIG. 4, each stud bolt 81 has a tool engaging
feature 81a at the free end. Further, the stud bolt 81 protrudes
from the second downstream flange 64b by more than twice the
thickness of the nut 83 in the assembled state so that an
additional nut 84 may be threaded onto the free end of the stud
bolt 81. Therefore, even when the stud bolt 81 is firmly lodged in
the threaded hole 70 of the joint flange portion 71a, the stud bolt
81 can be unscrewed from the threaded hole 70 by applying an
unfastening torque to the additional nut 84 with a suitable tool.
Since the additional nut 84 has a relatively large diameter, a
large unfastening torque can be applied to the stud bolt 81.
[0087] As shown in FIGS. 4 and 6, the dimension L3 of the gap Gin
the axial direction of the flexible pipe member 72 is selected such
that the first gasket 68 and the second gasket 69 in an unused
state can be fitted into the gap between the low-pressure EGR valve
65 and the second low-pressure EGR pipe 64 and the gap between the
low-pressure EGR valve 65 and the joint member 71, respectively.
More specifically, when the flexible pipe member 72 is moved
leftward until the corresponding end of the flexible pipe member 72
abuts the annular shoulder surface 41c, the gap (t3) created
between the low-pressure EGR valve 65 and the second low-pressure
EGR pipe 64 and the gap (t4) created between the low-pressure EGR
valve 65 and the joint member 71 are larger than the thicknesses of
the first gasket 68 and the second gasket 69 in an unused state.
Therefore, the removal and reinstalling of the low-pressure EGR
valve 65 can be accomplished with ease.
[0088] Although the present invention has been described in terms
of a preferred embodiment thereof, it is obvious to a person
skilled in the art that various alterations and modifications are
possible without departing from the spirit of the present
invention. For instance, the present invention was applied to an
automotive diesel engine, but may also be applied to gasoline
engines as well, and may also be applied to engines for other
applications, such as railways and other ground transportation
vehicles, watercraft and aircraft.
[0089] Further, in the above-described embodiment, the engine 4 was
laterally mounted on the motor vehicle 1, but may be mounted
longitudinally. The exhaust side of the engine may also be provided
on the opposite side of the engine without departing from the
spirit of the present invention. In the foregoing embodiment, the
EGR device was applied to the low-pressure EGR device 60, but may
be applied to the high-pressure EGR device 50. In the above
embodiment, the turbocharger 40 may be replaced with a supercharger
which may be powered either by an electric motor or the output of
the engine. In the above embodiment, the compressor connecting pipe
portion 41b was formed integrally with the compressor housing 41a,
but may also be formed separately from the compressor housing 41a
and coupled to the compressor housing 41a. In the above embodiment,
two stud bolts 81 were implanted in the joint member 71, but one or
three or more stud bolts 81 may be used, and the stud bolts 81 may
also be implanted to the second low-pressure EGR piping 64.
Alternatively, it is also possible to do away with the stud bolts
81 altogether, and use only normal threaded bolts.
[0090] In the above embodiment, the stud bolts 81 and the normal
bolt 82 were passed through the valve housing 65a of the
low-pressure EGR valve 65, and the second low-pressure EGR pipe 64,
the low-pressure EGR valve 65 and the joint member 71 were fastened
together by the nut 83. However, a fastening means for fastening
the second low-pressure EGR pipe 64 and the low-pressure EGR valve
65 to each other and a fastening means for fastening the
low-pressure EGR valve 65 and the joint member 71 to each other may
be separately provided.
[0091] Alternatively, fasteners other than bolts and nuts may be
used for the fastening member. In the above embodiment, the gap G
was formed between the annular shoulder surface 41c and the
flexible pipe member 72, but it may also be formed between the
annular shoulder surface 71c and the corresponding end of the
flexible pipe member 72. Furthermore, the compressor connecting
pipe portion 41b and the joint connecting pipe portion 71b may not
be exactly aligned in a coaxial relationship, and/or the flexible
pipe member 72 may be bent or otherwise curved.
* * * * *