U.S. patent application number 10/409599 was filed with the patent office on 2003-11-20 for apparatus and method for purifying exhaust gas in engine.
This patent application is currently assigned to NISSAN MOTOR CO., LTD.. Invention is credited to Tabata, Munehiro.
Application Number | 20030213231 10/409599 |
Document ID | / |
Family ID | 28449926 |
Filed Date | 2003-11-20 |
United States Patent
Application |
20030213231 |
Kind Code |
A1 |
Tabata, Munehiro |
November 20, 2003 |
Apparatus and method for purifying exhaust gas in engine
Abstract
The apparatus improves regeneration efficiency of a diesel
particulate filter (DPF) that traps particulate matter, reduces
pressure loss caused by the filter, and benefits space of a
vehicle. Therefor, the DPF that traps particulate matter having a
large diameter is connected to or close to an exhaust manifold in
an engine, and the DPF that traps particulate matter having a small
diameter is disposed in an exhaust pipe downstream of the exhaust
manifold and at a location away (under a vehicle floor) from the
exhaust manifold.
Inventors: |
Tabata, Munehiro;
(Isehara-shi, JP) |
Correspondence
Address: |
FOLEY AND LARDNER
SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
NISSAN MOTOR CO., LTD.
|
Family ID: |
28449926 |
Appl. No.: |
10/409599 |
Filed: |
April 9, 2003 |
Current U.S.
Class: |
60/280 ; 60/297;
60/311 |
Current CPC
Class: |
Y02T 10/20 20130101;
F01N 2250/02 20130101; Y02T 10/12 20130101; F02B 29/04 20130101;
F01N 2330/06 20130101; F01N 3/0222 20130101; F01N 3/035 20130101;
F02B 37/00 20130101; F01N 3/023 20130101; F01N 2340/04 20130101;
F01N 13/0093 20140601; F01N 3/021 20130101; F01N 13/009
20140601 |
Class at
Publication: |
60/280 ; 60/311;
60/297 |
International
Class: |
F01N 003/00; F01N
003/02; F01N 005/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 9, 2002 |
JP |
2002-106683 |
Claims
What is claimed:
1. An apparatus for purifying an exhaust gas in an engine
comprising: an exhaust passage in the engine; a first filter
disposed in an upstream side of the exhaust passage, the first
filter trapping particulate matter that has at least a first
diameter; and a second filter disposed in a downstream side of the
exhaust passage and placed separately from the first filter, the
second filter trapping particulate matter that has at least a
second diameter, the second diameter smaller than the first
diameter.
2. An apparatus according to claim 1, further comprising: a first
casing containing the first filter; and a second casing containing
the second filter, the second casing separate from the first
casing.
3. An apparatus according to claim 1, wherein the first diameter is
in the range of 80-100 nm.
4. An apparatus according to claim 1, wherein the second diameter
is in the range of 20-50 nm.
5. An apparatus according to claim 1, wherein the exhaust passage
comprises an exhaust manifold connected to a cylinder head of the
engine and an exhaust pipe downstream of the exhaust manifold,
further comprising: an exhaust turbine in a turbocharger disposed
between the exhaust manifold and the exhaust pipe wherein, the
first filter is disposed upstream of the exhaust turbine.
6. An apparatus according to claim 1, further comprising: the
exhaust passage comprises an exhaust manifold connected to a
cylinder head of the engine and an exhaust pipe downstream of the
exhaust manifold, further comprising: an exhaust turbine in a
turbocharger disposed between the exhaust manifold and the exhaust
pipe wherein, the first filter is disposed downstream of the
exhaust turbine.
7. An apparatus according to claim 1, wherein the first filter is
disposed under an engine hood; and the second filter is disposed
under a vehicle body floor.
8. An apparatus according to claim 1, wherein a capacity of the
first filter is less than a capacity of the second filter.
9. An apparatus according to claim 1, wherein each of the first and
second filters carries a catalyst.
10. A method for purifying an exhaust gas in an engine comprising:
disposing a first filter in an upstream side of an exhaust passage;
and disposing a second filter in a downstream side of the exhaust
passage and placed separately from the first filter wherein the
first filter traps particulate matter having a larger diameter than
the diameter of the particulate matter which the second filter
traps.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an apparatus for purifying
an exhaust gas in an engine and in particular, for trapping and
burning particulate matter in the exhaust gas.
[0003] 2. Background Art
[0004] In an earlier apparatus for purifying an exhaust gas of an
engine, as shown in Japanese Unexamined Patent Publication No.
2001-295627, a front filter and a rear filter are disposed in a
single filter casing. The front filter has bores adapted to trap
particulate matter having a large diameter and the rear filter has
bores adapted to trap particulate matter having a small
diameter.
SUMMARY OF THE INVENTION
[0005] In the above earlier technology the two types of the filters
used respectively in the front and in the rear. However, the front
filter is positioned adjacent to the rear filter in the filter
casing, thereby causing the following problems.
[0006] When this filter casing is disposed under a vehicle floor,
the particulate matter having a large diameter to be trapped in the
front filter do not burn due to low exhaust gas temperature, and
regeneration efficiency of the filter deteriorates.
[0007] On the other hand, this filter housing has a capacity enough
for receiving two filters and therefore, it is difficult to find
space enough for positioning the filter casing close to an exhaust
manifold having a high exhaust gas temperature in an engine hood.
In case where a pressure loss is controlled to be low, particularly
for engine output increase, the capacity of the rear filter is
required to be large and accordingly, it is more difficult to find
space around the engine for attaching the filter casing receiving
two filters.
[0008] The present invention provides an apparatus for purifying an
exhaust gas of an engine to solve the foregoing problems.
[0009] Therefore, one aspect of the invention provides an apparatus
of disposing a first filter in an upstream side of the exhaust
passage to trap particulate matter having at least a first diameter
and disposing a second filter in a downstream side of the exhaust
passage to trap particulate matter having at least a second
diameter, the second diameter smaller than the first diameter.
[0010] These and other aspects, and features of this invention will
be understood from the following description with accompanying
drawings.
BRIEF EXPLANATION OF THE DRAWINGS
[0011] FIG. 1 is a system view of an engine showing a first
embodiment according to the invention.
[0012] FIG. 2 is a view showing a layout of the first
embodiment-mounting vehicle.
[0013] FIG. 3 is a schematic perspective view of a diesel
particulate filter.
[0014] FIG. 4 is an enlarged cross section view showing an inner
structure of the diesel particulate filter.
[0015] FIG. 5 is a view showing a difference between a diesel
particulate filter with large mesh size and a diesel particulate
filter with small mesh size.
[0016] FIG. 6 is a view showing a relation between a distance from
the engine and an exhaust gas temperature.
[0017] FIG. 7 is a view showing a relation between a diameter of a
particulate matter and oxidizing temperature.
[0018] FIG. 8 is a view showing a relation between a capacity of
the diesel particulate filter and a pressure loss of the diesel
particulate filter.
[0019] FIG. 9, is a view showing between a diameter of the
particulate matter that can be trapped and the loss of the diesel
particulate filter.
[0020] FIG. 10 is a view showing a relation between the capacity of
the diesel particulate filter, and the diameter of the particulate
matter that can be trapped and a tolerance pressure loss.
[0021] FIG. 11a is a system view of an engine showing a second
embodiment according to the invention.
DETAILED EXPLANATION OF THE PREFERRED EMBODIMENTS
[0022] The preferred embodiments according to the invention will be
explained with reference to the drawings as follows.
[0023] FIG. 1 is a system view of a diesel engine showing a first
embodiment of the invention. Air is aspired into a combustion
chamber 2 of each cylinder in a diesel engine 1 through an intake
system such as an air cleaner 3, an intake compressor 4 of a
turbocharger, an intercooler 5, an intake throttle valve 6, and an
intake manifold 7. An injector 8 directly injects fuel into
combustion chamber 2 where the mixture thereof burns by compression
ignition.
[0024] An exhaust gas after the combustion is discharged from an
exhaust manifold 9a connected to a cylinder head of engine 1 and an
exhaust pipe 9b connected thereto, which drives an exhaust turbine
10 of the turbocharger disposed in exhaust pipe 9b.
[0025] A particulate filter 11a with a first mesh size (large mesh
size) is contained in a casing 11a that traps particulate matter
having a large diameter and a particulate 12a filter with a second
mesh size (small mesh size) is contained in a casing 12a that traps
particulate matter having a small diameter are separately disposed
as a diesel particulate filter (DPF hereinafter) in an exhaust
passage where the particulate matter trapped burns in order to
purify the particulate matter in the exhaust gas discharged from
diesel engine 1. As described later, the bores of the large mesh
size are not necessarily larger than the bores of the small mesh
size, but the bores of the large mesh size are adapted to trap
particulate matter having a larger diameter and the bores of the
small mesh size are adapted to trap particulate matter having a
small diameter.
[0026] DPF 11a is directly connected to exhaust manifold 9a
upstream of exhaust turbine 10. DPF 11a may be disposed close to
exhaust manifold 9a. On the other hand, DPF 12a is positioned in
exhaust pipe 9b and at a location away from exhaust manifold 9a
(namely, downstream of exhaust turbine 10). An exhaust passage 9
includes exhaust manifold 9a, DPF 11a, exhaust turbine 10 of the
turbocharger, DPF 12a, and exhaust pipe 9b.
[0027] FIG. 2 is a layout view of the first embodiment-mount
vehicle where DPF 11a is disposed in an engine hood. D in the
figure shows a dash panel that is a partition wall between a front
side and a rear side of the engine hood and R in the figure shows a
radiator disposed in the front side of the engine hood.
[0028] DPF 12a is disposed in the middle of an exhaust pipe 9b
extending along and under a vehicle floor from engine 1 toward a
vehicle rear side, and a flexible tube F and a ball coupling (not
shown) included in exhaust passage 9 are used for its
connection.
[0029] DPF 11a with the large mesh size and DPF 12a with the small
mesh size will be explained in detail. First, the points common in
both DPF 11a and DPF 12a will be explained. DPF 11a and DPF 12a
both are formed of porous ceramic and honeycomb structure having a
circular shape, and received in a cylindrical housing (not shown)
through a holding mat.
[0030] In an inner structure of DPF 11a, 12a, as shown in FIG. 4
showing an enlarged cross section of the honeycomb structure, a
plurality of parallel cell spaces 22 are formed being partitioned
by porous latticed cell walls 21 made of honeycomb-structure
ceramic and each cell space extends toward an exhaust gas flow
direction. In relation to neighboring cell spaces, an outlet of one
cell space is closed by a sealing member 23 and an inlet of the
other neighboring cell space is closed by a sealing member 24
alternately.
[0031] Cell space 22 where the inlet is open and the outlet is
closed by the sealing member 23 is an exhaust gas--inflow cell
space 22A and cell space 22 where the inlet is closed by sealing
member 24 and the outlet is open is an exhaust gas--outflow cell
space 22B. An exhaust gas from engine 1 flows into cell space 22A
and outflows into cell space 22B only through porous cell wall 21
(its air hole). Therefore, cell wall 21 can certainly trap the
particulate matter in the exhaust gas.
[0032] An inner surface of cell wall 21 facing cell space 22A is
coated with a catalyst including precious medals such as Pt, Pd, Rh
and the like to form a catalyst layer 25 and thereby, along with
trapping the particulate matter in the exhaust gas, due to catalyst
effect, oxidization of HC and CO in the exhaust gas is prompted and
these HC and CO can be purified. And also the deposited particulate
matter can be burned and removed under oxygen in the exhaust gas by
the particulate matter being heated due to its reaction heat.
[0033] Different points between DPF 11a and DPF 12a will be
explained next. DPF 11a with large mesh size can trap the
particulate matter in a relatively large diameter and has a
relatively small flow resistance and DPF with small mesh size can
trap the particulate matter in a relatively small diameter and has
a relatively large flow resistance.
[0034] FIG. 5(a) shows an enlarged cross section view of a lattice
cell wall 21 of DPF 11a with the first mesh size and Fig. (b) or
(c) shows an enlarged cross section view of lattice cell wall 21 of
DPF 12a. Lattice cell wall 21 of DPF 11a, as shown in FIG. 5(a),
can trap the particulate matter in 80-100 nm of a particle diameter
by enlarging an averaging bore diameter of the air bores.
[0035] On the other hand, lattice cell wall 21 of DPF 12a with the
second mesh size, as shown in FIG. 5(b), can trap the particulate
matter in 20-50 nm of a particle diameter by reducing an averaging
bore diameter of the air bores or, as shown in FIG. 5(c), can trap
the particulate matter by increasing a wall thickness thereof to
enlarge a passing length or a contact surface area thereof without
changing an averaging bore diameter of the air bores to DPF 11a in
FIG. 5(a). Large mesh size and small mesh size may be formed by
selection of a material (fabric ceramic, foam metal) in addition of
change of the air bore diameter or the wall thickness.
[0036] If a capacity of DPF 11a is V1 and a capacity of DPF 12a is
V2, V1 is set as a value less than V2. When DPF 11a and DPF 12a
have the same capacity, and a total capacity of the flow paths in
the small mesh size is smaller than in the large mesh size and
thereby, the small mesh size have more flow resistance than the
large mesh size. Accordingly in order to make the flow resistance
or total capacity of the flow paths in DPF 11a to be equal to that
of the DPF 12a it is desirable to increase the capacity of DPF 12a
with small mesh size compared with DPF 11a with large mesh size.
Pressure loss is an important factor and a pressure loss of an
engine is determined by the largest pressure loss among pressure
resistance factors in the exhaust system and therefore, no
difference in the pressure loss between DPF 11a and DPF 12a is
preferable.
[0037] The effect of the embodiment will be explained. DPF 11a with
large mesh size that traps particulate matter in a relatively large
diameter is disposed around exhaust manifold 9 and therefore, it is
sufficient only if DPF 12a with small mesh size downstream of DPF
11a traps particulate matter in a relatively small diameter.
[0038] As seen in FIG. 6 showing a relation between a distance from
an engine and an exhaust gas temperature, DPF 11a traps particulate
matter in a relatively large diameter in the vicinity of exhaust
manifold 9 in a high temperature atmosphere and therefore, even if
a diameter of the particulate matter trapped is large, the
particulate matter can be burned properly, thereby promoting
regeneration efficiency.
[0039] As seen in FIG. 7 showing a relation between particulate
matter diameter and oxidization temperature, as the particulate
matter diameter becomes larger, the oxidization temperature is
lower and therefore, even when the DPF is positioned under a
vehicle body floor away from an engine, the particulate matter can
burn.
[0040] As seen in FIG. 8 showing a relation between DPF capacity
and DPF pressure loss, as the DPF capacity becomes larger, the
pressure loss becomes smaller. As seen in FIG. 9 showing a relation
between a diameter of a particulate matter to be able to be trapped
and DPF pressure loss, as a particle diameter to be able to be
trapped becomes larger, a flow resistance thereof becomes smaller
and thereby the pressure loss becomes small.
[0041] Accordingly in DPF 11a that can traps particulate matter in
a large diameter, as seen in FIG. 9, when the pressure loss is
small, and even if the pressure loss increases due to reducing a
capacity of DPF 11a as seen in FIG. 8, a total pressure can be
maintained at a certain level. As an equal pressure line of a
tolerance pressure loss is shown by DPF 11a capacity and a diameter
of the particulate matter to be able to be trapped as a parameter
in FIG. 10, since in a case of DPF 11a the diameter of the
particulate matter to be able to be trapped is large, DPF capacity
can be reduced. Thereby a small capacity of DPF 11a can be used and
a small space for receiving DPF 11a can be used, enabling
positioning DPF 11a in the vicinity of engine 1 which has a small
space.
[0042] On the other hand, DPF 12a with small mesh size that traps
particulate matter in a relatively small diameter is positioned in
a downstream side away from the vicinity of exhaust manifold 9 and
DPF 11a in the upstream side traps the particulate matter in a
large diameter. Therefore, since DPF 12a traps only the particulate
matter in a small diameter that does not require a high temperature
for its burning, it is not difficult to burn.
[0043] In DPF 12a with small mesh size having a small diameter, the
flow resistance is large and the pressure loss increases. However,
since due to increasing the capacity of DPF 12a, increase of the
pressure loss can be controlled (FIG. 9) and there is enough space
for DPF 12a, there is no problem for increasing the capacity
thereof.
[0044] With reference to FIG. 10, in DPF 12a a tolerance pressure
loss can be maintained to a certain level by increasing the DPF
capacity corresponding to a particle diameter of the particle
matter for trap being small. Although this increase of the DPF
capacity requires more space, there is no problem with it because
there is space for accommodating DPF 12a under a vehicle floor.
[0045] According to the embodiment, a particulate filter with large
mesh size that traps particulate matter having a relatively large
diameter is disposed in the vicinity of an exhaust manifold and on
the other hand, a particulate filter with small mesh size that
traps particulate matter having a relatively small diameter is
dispose in a downstream side away from the vicinity of the exhaust
manifold. Thereby the embodiment can provides an exhaust
purification apparatus that has an excellent quality in terms of
regeneration efficiency, pressure loss, and space of a particulate
filter.
[0046] According to the embodiment, a particulate filter with large
mesh size is disposed upstream of an exhaust gas turbine. Thereby
regeneration efficiency thereof can be improved by making use of a
high-temperature exhaust gas prior to a temperature decrease
thereof caused by the exhaust gas turbine.
[0047] According to the embodiment, it is practical to position a
particulate filter with large mesh size within an engine hood and
position a particulate filter with small mesh size under a vehicle
floor.
[0048] According to the embodiment, a capacity (V1) of a
particulate filter with large mesh size having a small flow
resistance is made small and a capacity of a particulate filter
with small mesh size having a large flow resistance is made large
(V2; V2>V1). Thereby an increase of the pressure loss can be
restrained.
[0049] According to the embodiment, each of a particulate filter
with large mesh size and a particulate filter with small mesh size
has a catalyst by which oxidization of HC and CO in the exhaust gas
is promoted. Therefore, the particulate matter can be properly
burned by using reaction heat thereof.
[0050] A second embodiment according to the invention will be
explained with reference to FIG. 11a. In the first embodiment, DPF
11a is disposed upstream of exhaust gas turbine 10 whereby the
regeneration efficiency of DPF 11a can be improved by making use of
the high-temperature exhaust gas prior to the temperature decrease
caused by exhaust gas turbine 10. However, there may be a little
space upstream of exhaust gas turbine 10 and also a turbocharger
performance may deteriorate if a distance between an engine and the
turbocharger is lengthened.
[0051] Coping with the above problems, the second embodiment, as
shown in FIG. 11a, DPF 11a is disposed immediately downstream of
exhaust gas turbine 10. thereby regeneration efficiency of DPF 11a
can be properly maintained by using a high-temperature exhaust gas
as much as possible in a relatively spacious location without
deteriorating a turbocharger performance.
[0052] In regard to an application of the second embodiment to a
vehicle, in the same as the first embodiment as shown in FIG. 2,
DPF 11a can be disposed in the engine hood and DPF 12a can be
disposed under a vehicle floor.
[0053] This application claims priority to Japanese Patent
Application No. 2002-106683 filed Apr. 9, 2002. The entire
disclosure of Japanese Patent Application No. 2002-106683 is hereby
incorporated herein by reference.
[0054] While only selected embodiments have been chosen to
illustrate the present invention, it will be apparent to those
skilled in the art from this disclosure that various changes and
modifications can be made herein without departing from the scope
of the invention as defined in the appended claims.
[0055] Furthermore, the foregoing description of the embodiments
according to the present invention is provided for illustration
only, and not for the purpose of limiting the invention as defined
by the appended claims and their equivalents. Moreover, features of
the different embodiments may be combined.
* * * * *