U.S. patent application number 11/795338 was filed with the patent office on 2008-05-29 for exhaust gas purification system for internal combustion engine.
Invention is credited to Tomihisa Oda, Kouseki Sugiyama.
Application Number | 20080120966 11/795338 |
Document ID | / |
Family ID | 36569953 |
Filed Date | 2008-05-29 |
United States Patent
Application |
20080120966 |
Kind Code |
A1 |
Sugiyama; Kouseki ; et
al. |
May 29, 2008 |
Exhaust Gas Purification System for Internal Combustion Engine
Abstract
An exhaust passageway of the internal combustion engine is
formed of a single exhaust pipe 5. A portion 11b configuring a
passageway through which the exhaust gas passes and a portion 11c
provided with a catalyst 11e heating up the exhaust gas by emitting
heat upon being supplied with a reducing agent, are provided in
parallel so as to share a section of the single exhaust pipe with
each other on an upstream side 11 of an exhaust gas purifying
device 10 in the exhaust pipe 5. In the exhaust gas flowing through
the exhaust pipe 5, allocation of a quantity of the exhaust gas
passing through the catalyst 11e and a quantity of the exhaust gas
passing through the passageway 11b, is set changeable.
Inventors: |
Sugiyama; Kouseki;
(Shizuoka-ken, JP) ; Oda; Tomihisa; (Shizuoka-ken,
JP) |
Correspondence
Address: |
KENYON & KENYON LLP
1500 K STREET N.W., SUITE 700
WASHINGTON
DC
20005
US
|
Family ID: |
36569953 |
Appl. No.: |
11/795338 |
Filed: |
March 28, 2006 |
PCT Filed: |
March 28, 2006 |
PCT NO: |
PCT/JP2006/307008 |
371 Date: |
July 16, 2007 |
Current U.S.
Class: |
60/287 ; 60/300;
60/301 |
Current CPC
Class: |
F01N 2410/02 20130101;
F01N 3/2053 20130101; F01N 13/011 20140603; F01N 3/204 20130101;
F02D 2200/0802 20130101; Y02T 10/12 20130101; Y02T 10/26 20130101;
F02D 41/1454 20130101; F01N 3/0821 20130101; F01N 2410/12 20130101;
F01N 3/0253 20130101; F01N 2410/04 20130101; F01N 13/0097 20140603;
F01N 13/009 20140601; F01N 3/2033 20130101; F01N 2410/06
20130101 |
Class at
Publication: |
60/287 ; 60/301;
60/300 |
International
Class: |
F01N 3/20 20060101
F01N003/20; F01N 3/025 20060101 F01N003/025 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 28, 2005 |
JP |
2005-091485 |
Claims
1. An exhaust gas purifying system of an internal combustion
engine, comprising: an exhaust gas purifying device provided in an
exhaust passageway of said internal combustion engine, purifying an
exhaust gas passing through said exhaust passageway and with its
temperature increased to a predetermined temperature or higher with
the result that purifying capability thereof is improved; exhaust
gas temperature increasing unit provided on an upstream side of
said exhaust gas purifying device in said exhaust passageway; and
reducing agent adding unit provided on the upstream side of said
exhaust gas temperature increasing unit in said exhaust passageway
and adding a reducing agent to the exhaust gas passing through said
exhaust passageway, wherein said exhaust gas temperature increasing
unit includes: an exhaust gas temperature increasing catalyst
provided in a single exhaust pipe configuring said exhaust
passageway so that an exhaust gas flow-through area trough which
the exhaust gas should pass is left, supplied with the reducing
agent added from said reducing agent adding unit and thereby
emitting heat; and an exhaust gas flow rate control device
controlling, in the exhaust gas passing through said exhaust pipe,
allocation of a quantity of the exhaust gas passing said exhaust
gas flow-through area and a quantity of the exhaust gas passing
through said exhaust gas temperature increasing catalyst.
2. An exhaust gas purifying system of an internal combustion engine
according to claim 1, wherein said exhaust gas flow-through area is
disposed in a central portion in section perpendicular to an
exhaust gas pass-through direction in said exhaust pipe, and said
exhaust gas temperature increasing catalyst is disposed outside of
said exhaust gas flow-through area within the section.
3. An exhaust gas purifying system of an internal combustion engine
according to claim 1, wherein said exhaust gas flow rate control
device is capable of selecting, by controlling the allocation, a
state where substantially an entire quantity of the exhaust gas
flowing through said exhaust pipe passes through said exhaust gas
flow-through area, a state where substantially the entire quantity
of the exhaust gas flowing through said exhaust pipe passes through
said exhaust gas temperature increasing catalyst, and a state where
the exhaust gas flowing through the exhaust pipe passes through
both of said exhaust gas flow-through area and said exhaust gas
temperature increasing catalyst.
4. An exhaust gas purifying system of an internal combustion engine
according to claim 1, wherein when increasing the temperature of
said exhaust gas purifying device, said reducing agent adding unit
adds the reducing agent to the exhaust gas passing through said
exhaust passageway, and said exhaust gas flow rate control device
controls the allocation in order to make substantially the entire
quantity of the exhaust gas flowing through said exhaust pipe pass
through said exhaust gas temperature increasing catalyst, and said
exhaust gas flow rate control device, after the reducing agent
added from said reducing agent adding unit has reached said exhaust
gas temperature increasing catalyst, controls the allocation in
order to decrease, in the exhaust gas flowing through said exhaust
pipe, the quantity of the exhaust gas passing through said exhaust
gas temperature increasing catalyst.
5. An exhaust gas purifying system of an internal combustion engine
according to claim 1, wherein said exhaust gas flow rate control
device, during a decelerating operation of a vehicle mounted with
said internal combustion engine, controls the allocation in order
to decrease, in the exhaust gas flowing through said exhaust pipe,
the quantity of the exhaust gas passing through said exhaust gas
temperature increasing catalyst.
6. An exhaust gas purifying system of an internal combustion engine
according to claim 2, wherein said exhaust gas flow rate control
device is capable of selecting, by controlling the allocation, a
state where substantially an entire quantity of the exhaust gas
flowing through said exhaust pipe passes through said exhaust gas
flow-through area, a state where substantially the entire quantity
of the exhaust gas flowing through said exhaust pipe passes through
said exhaust gas temperature increasing catalyst, and a state where
the exhaust gas flowing through the exhaust pipe passes through
both of said exhaust gas flow-through area and said exhaust gas
temperature increasing catalyst.
7. An exhaust gas purifying system of an internal combustion engine
according to claim 2, wherein when increasing the temperature of
said exhaust gas purifying device, said reducing agent adding unit
adds the reducing agent to the exhaust gas passing through said
exhaust passageway, and said exhaust gas flow rate control device
controls the allocation in order to make substantially the entire
quantity of the exhaust gas flowing through said exhaust pipe pass
through said exhaust gas temperature increasing catalyst, and said
exhaust gas flow rate control device, after the reducing agent
added from said reducing agent adding unit has reached said exhaust
gas temperature increasing catalyst, controls the allocation in
order to decrease, in the exhaust gas flowing through said exhaust
pipe, the quantity of the exhaust gas passing through said exhaust
gas temperature increasing catalyst.
8. An exhaust gas purifying system of an internal combustion engine
according to claim 2, wherein said exhaust gas flow rate control
device, during a decelerating operation of a vehicle mounted with
said internal combustion engine, controls the allocation in order
to decrease, in the exhaust gas flowing through said exhaust pipe,
the quantity of the exhaust gas passing through said exhaust gas
temperature increasing catalyst.
9. An exhaust gas purifying system of an internal combustion engine
according to claim 3, wherein when increasing the temperature of
said exhaust gas purifying device, said reducing agent adding unit
adds the reducing agent to the exhaust gas passing through said
exhaust passageway, and said exhaust gas flow rate control device
controls the allocation in order to make substantially the entire
quantity of the exhaust gas flowing through said exhaust pipe pass
through said exhaust gas temperature increasing catalyst, and said
exhaust gas flow rate control device, after the reducing agent
added from said reducing agent adding unit has reached said exhaust
gas temperature increasing catalyst, controls the allocation in
order to decrease, in the exhaust gas flowing through said exhaust
pipe, the quantity of the exhaust gas passing through said exhaust
gas temperature increasing catalyst.
10. An exhaust gas purifying system of an internal combustion
engine according to claim 3, wherein said exhaust gas flow rate
control device, during a decelerating operation of a vehicle
mounted with said internal combustion engine, controls the
allocation in order to decrease, in the exhaust gas flowing through
said exhaust pipe, the quantity of the exhaust gas passing through
said exhaust gas temperature increasing catalyst.
11. An exhaust gas purifying system of an internal combustion
engine according to claim 4, wherein said exhaust gas flow rate
control device, during a decelerating operation of a vehicle
mounted with said internal combustion engine, controls the
allocation in order to decrease, in the exhaust gas flowing through
said exhaust pipe, the quantity of the exhaust gas passing through
said exhaust gas temperature increasing catalyst.
12. An exhaust gas purifying system of an internal combustion
engine according to claim 6, wherein when increasing the
temperature of said exhaust gas purifying device, said reducing
agent adding unit adds the reducing agent to the exhaust gas
passing through said exhaust passageway, and said exhaust gas flow
rate control device controls the allocation in order to make
substantially the entire quantity of the exhaust gas flowing
through said exhaust pipe pass through said exhaust gas temperature
increasing catalyst, and said exhaust gas flow rate control device,
after the reducing agent added from said reducing agent adding unit
has reached said exhaust gas temperature increasing catalyst,
controls the allocation in order to decrease, in the exhaust gas
flowing through said exhaust pipe, the quantity of the exhaust gas
passing through said exhaust gas temperature increasing
catalyst.
13. An exhaust gas purifying system of an internal combustion
engine according to claim 6, wherein said exhaust gas flow rate
control device, during a decelerating operation of a vehicle
mounted with said internal combustion engine, controls the
allocation in order to decrease, in the exhaust gas flowing through
said exhaust pipe, the quantity of the exhaust gas passing through
said exhaust gas temperature increasing catalyst.
14. An exhaust gas purifying system of an internal combustion
engine according to claim 7, wherein said exhaust gas flow rate
control device, during a decelerating operation of a vehicle
mounted with said internal combustion engine, controls the
allocation in order to decrease, in the exhaust gas flowing through
said exhaust pipe, the quantity of the exhaust gas passing through
said exhaust gas temperature increasing catalyst.
15. An exhaust gas purifying system of an internal combustion
engine according to claim 9, wherein said exhaust gas flow rate
control device, during a decelerating operation of a vehicle
mounted with said internal combustion engine, controls the
allocation in order to decrease, in the exhaust gas flowing through
said exhaust pipe, the quantity of the exhaust gas passing through
said exhaust gas temperature increasing catalyst.
16. An exhaust gas purifying system of an internal combustion
engine according to claim 12, wherein said exhaust gas flow rate
control device, during a decelerating operation of a vehicle
mounted with said internal combustion engine, controls the
allocation in order to decrease, in the exhaust gas flowing through
said exhaust pipe, the quantity of the exhaust gas passing through
said exhaust gas temperature increasing catalyst.
Description
[0001] This is a 371 national phase application of
PCT/JP2006/307008 filed 28 Mar. 2006, claiming priority to Japanese
Patent Application No. JP 2005-091485 filed 28 Mar. 2005, the
contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to an exhaust gas purifying
system of an internal combustion engine.
BACKGROUND OF THE INVENTION
[0003] An exhaust gas from an internal combustion engine contains
harmful substances such as NOx (nitrogen oxide). It is known that a
NOx catalyst for purifying the exhaust gas of NOx is provided in an
exhaust system of the internal combustion engine in order to
decrease emissions of these harmful substances. In this technology,
when a temperature of the NOx catalyst is low, there might be a
case that a NOx purifying efficiency decreases. Accordingly, the
temperature of the NOx catalyst needs increasing up to a
temperature at which the exhaust gas can be sufficiently purified
of NOx.
[0004] On the other hand, the exhaust gas from the internal
combustion engine contains particulate matters (PM) of which a main
component is carbon. A known technology for preventing the
emissions of these particulate matters into the atmospheric air
involves providing an exhaust system of the internal combustion
engine with a particulate filter (which will hereinafter simply be
termed a [filter]) for trapping (scavenging) the particulate
matters.
[0005] In this type of filter, when a deposition quantity of the
trapped particulate matters rises, a backpressure in the exhaust
gas increases due to clogging of the filter, and engine performance
declines. To cope with this, a temperature of the filter is raised
by increasing the temperature of the exhaust gas introduced into
the filter, and the trapped particulate matters are removed by
oxidation, thus scheming to regenerate the exhaust gas purifying
performance of the filter (which will hereinafter be referred to as
a [PM regenerating process]).
[0006] In the above PM regenerating process, when the temperature
of the filter is low, there might be a case of being unable to
sufficiently oxidation-remove the particulate matters trapped by
the filter. Accordingly, in this case also, the filter temperature
needs increasing up to the temperature at which the particulate
matters trapped by the filter can be sufficiently removed by
oxidation.
[0007] In this respect, as disclosed in Japanese Patent Application
Laid-Open Publication No. 2003-166417, such a technology is
proposed that there are provided a filter, an oxidation catalyst
disposed on an upstream side of the filter and a bypath via which
the exhaust gas bypasses the oxidation catalyst, and the filter is
warmed up as soon as possible when executing the PM regenerating
process by switchover as to which way, the bypath or the oxidation
catalyst, the exhaust gas should pass through. Alternatively, as
disclosed in published Japanese translations of PCT international
publication for patent applications No. 2003-533626, a technology
is proposed, wherein a catalyst-type burner and a fuel adding
device are provided upstream of the filter, and the PM regenerating
process can be executed surely at a low cost.
[0008] Herein, in the former technology, there was a case in which
when the exhaust gas passed through the bypath, the temperature of
the exhaust gas decreased, and the filter temperature was hard to
rise efficiently. Further, in the latter technology, during a
normal operation of the internal combustion engine, the
catalyst-type burner dissipated a great amount of exhaust heat, and
there was a possibility that the filter temperature might be
decreased.
SUMMARY OF INVENTION
[0009] It is an object of the present invention to provide a
technology capable of increasing the temperature of an exhaust gas
purifying device in an exhaust system of an internal combustion
engine more efficiently or more surely with a much simpler
configuration.
[0010] The following is a greatest feature of the present invention
for accomplishing the above object. An exhaust passageway of the
internal combustion engine is formed of a single exhaust pipe on an
upstream side of the exhaust gas purifying device, and a portion
configuring a passageway through which the exhaust gas passes and a
portion provided with a catalyst heating up the exhaust gas by
emitting heat upon being supplied with a reducing agent, are
provided in parallel with each other in the exhaust pipe. Then, in
the exhaust gas flowing through the exhaust pipe, allocation of a
quantity of the exhaust gas passing through the catalyst heating up
the exhaust gas and a quantity of the exhaust gas passing through
the passageway, is set changeable.
[0011] More specifically, in an exhaust gas purifying system of an
internal combustion engine, comprising:
[0012] an exhaust gas purifying device provided in an exhaust
passageway of the internal combustion engine, purifying an exhaust
gas passing through the exhaust passageway and heated up to a
predetermined temperature or higher with the result that purifying
capability thereof is improved;
[0013] exhaust gas temperature increasing unit provided on an
upstream side of the exhaust gas purifying device in the exhaust
passageway; and
[0014] reducing agent adding unit provided on the upstream side of
the exhaust gas temperature increasing unit in the exhaust
passageway and adding a reducing agent to the exhaust gas passing
through the exhaust passageway,
[0015] an improvement is characterized in that the exhaust gas
temperature increasing unit includes:
[0016] an exhaust gas temperature increasing catalyst provided in a
single exhaust pipe configuring the exhaust passageway so that an
exhaust gas flow-through area trough which the exhaust gas should
pass is left, supplied with the reducing agent added from the
reducing agent adding unit and thereby emitting heat; and
[0017] an exhaust gas flowrate control device controlling, in the
exhaust gas passing though the exhaust pipe, allocation of a
quantity of the exhaust gas passing the exhaust gas flow-through
area and a quantity of the exhaust gas passing through the exhaust
gas temperature increasing catalyst.
[0018] Herein, in the case of purifying the exhaust gas of the NOx
by the NOx catalyst provided in the exhaust system of the internal
combustion engine, the NOx catalyst needs to have a temperature
equal to or higher than an activation temperature at which the NOx
can be occluded. Further, in the case of executing the PM
regenerating process on the filter provided in the exhaust system,
it is required that a temperature of the filter be kept equal to or
higher than a temperature at which the particulate matters trapped
by the filter can be removed by oxidation.
[0019] Then, for attaining this, there might be a case of taking a
method by which the exhaust gas temperature increasing catalyst for
increasing the temperature of the exhaust gas flowing into the NOx
catalyst or the filter is provided on the upstream side of the NOx
catalyst or the filter, and the temperature of the exhaust gas
flowing into the NOx catalyst or the filter is increased by
reaction heat generated by supplying the reducing agent to this
exhaust gas temperature increasing catalyst.
[0020] In such a case, if a heat retaining property of the exhaust
gas temperature increasing catalyst itself is insufficient, even
when supplying the reducing agent to the exhaust gas temperature
increasing catalyst, there was a possibility that the temperature
of the exhaust gas flowing into the NOx catalyst or the filter
could not be amply increased.
[0021] Further, for example, if the temperature of the NOx catalyst
or the filter is high, there might occur such a case that the
exhaust gas not passing through the exhaust gas temperature
increasing catalyst is to flow directly into the NOx catalyst or
the filter. For attaining this, it is considered that a bypath via
which the exhaust gas bypasses the exhaust gas temperature
increasing catalyst is provided separately from the exhaust pipe.
In this case, however, the exhaust passageway comes to have a
complicated structure, and there was a possibility that
mountability on a vehicle declines or it becomes difficult to
reduce costs.
[0022] Such being the case, according to the present invention, the
exhaust gas temperature increasing unit is provided on the upstream
side of the exhaust gas purifying device in the exhaust passageway.
Then, in the exhaust gas temperature increasing unit, the exhaust
gas temperature increasing catalyst is provided in the single
exhaust pipe configuring the exhaust passageway so as to occupy
part of the section of the exhaust pipe, and a remaining area of
the section of the exhaust pipe is set as the exhaust gas
flow-through area through which the exhaust gas passes. Then, the
exhaust gas flow rate control device can control, in the exhaust
gas flowing through the exhaust pipe, the allocation of the
quantity of the exhaust gas passing through the exhaust gas
flow-through area and the quantity of the exhaust gas passing
through the exhaust gas temperature increasing catalyst.
[0023] With this contrivance, the exhaust gas temperature
increasing catalyst and the exhaust gas flow-through area can be
formed in parallel with each other in an interior of the single
exhaust pipe configuring the exhaust passageway, and hence a
contact area between the exhaust gas temperature increasing
catalyst and the external portion of the exhaust passageway can be
decreased to the greatest possible degree. Further, when the
exhaust gas passes through the exhaust gas flow-through area, the
heat of the exhaust gas can be efficiently transferred to the
exhaust gas temperature increasing catalyst. As a result thereof,
the heat retaining property of the exhaust gas temperature
increasing catalyst can be improved.
[0024] Moreover, both of the exhaust gas temperature increasing
catalyst and the exhaust gas flow-through area through which the
exhaust gas passes can be provided in the single exhaust pipe, and
the structure can be thus simplified, whereby the mountability of
the exhaust gas purifying system on the vehicle can be improved,
and the cost reduction can be also attained.
[0025] Furthermore, according to the present invention, the exhaust
gas flow-through area may be disposed in a central portion in
section perpendicular to an exhaust gas pass-through direction in
the exhaust pipe, and the exhaust gas temperature increasing
catalyst may be disposed outwardly of the exhaust gas flow-through
area within the section.
[0026] Herein, if the exhaust gas warmed up by the exhaust gas
temperature increasing catalyst uniformly flows to an
upstream-sided edge surface of the exhaust gas purifying device,
the temperature of the exhaust gas purifying device tends to be
high at its central portion and becomes lower as it gets closer to
a peripheral portion thereof. This is attributed to an escape of
the heat into the outside air from the outer peripheral portion of
the exhaust gas purifying device.
[0027] By contrast, according to the present invention, the exhaust
gas flow-through area through which the exhaust gas passes is
disposed at the central portion in the section perpendicular to an
exhaust gas pass-through direction in the exhaust pipe, and the
exhaust gas temperature increasing catalyst is disposed outside of
the exhaust gas flow-through area within the section. With this
arrangement, the exhaust gas temperature increasing catalyst can be
distributed over the outer peripheral portion in the section
perpendicular to the exhaust gas pass-through direction in the
exhaust pipe. This contrivance being thus made, the exhaust gas
heated up by the exhaust gas temperature increasing catalyst can be
supplied concentratedly to the outer peripheral portion of the
exhaust gas purifying device, and, even when the heat escapes into
the outside air from the outer peripheral portion of the exhaust
gas purifying device, the temperature of the exhaust gas purifying
device can be increased uniformly.
[0028] Further, according to the present invention, the exhaust gas
flow rate control device may be set capable of selecting, by
controlling the allocation, a state where substantially an entire
quantity of the exhaust gas flowing through the exhaust pipe passes
through the exhaust gas flow-through area, a state where
substantially the entire quantity of the exhaust gas flowing
through the exhaust pipe passes through the exhaust gas temperature
increasing catalyst, and a state where substantially the entire
quantity of the exhaust gas flowing through the exhaust pipe passes
through both of the exhaust gas flow-through area and the exhaust
gas temperature increasing catalyst.
[0029] This contrivance being thus made, the exhaust gas flow rate
control device selects the state where substantially the entire
quantity of the exhaust gas flowing through the exhaust pipe passes
through the exhaust gas temperature increasing catalyst, and the
reducing agent adding unit adds the reducing agent to the exhaust
gas, whereby the exhaust gas temperature increasing catalyst is
supplied with the entire quantity of the exhaust gas and can get
the reducing reaction caused by the reducing agent. This enables an
inflow of only the high-temperature exhaust gas into the exhaust
gas purifying device.
[0030] Further, the exhaust gas flow rate control device selects
the state where substantially the entire quantity of the exhaust
gas flowing through the exhaust pipe passes through the exhaust gas
flow-through area, whereby the exhaust gas can be flowed directly
into the exhaust gas purifying device without passing through the
exhaust gas temperature increasing catalyst. With this contrivance,
if the exhaust temperature of the exhaust gas discharged from the
internal combustion engine is high such as when in a high-load
operation, the exhaust gas purifying device can be heated up by a
thermal energy of the exhaust gas. Further, when the temperature of
the exhaust gas purifying device is high and in a low-load
operation, the exhaust gas temperature increasing catalyst can be
restrained from becoming an excessively high temperature by flowing
a comparatively low-temperature exhaust gas directly into the
exhaust gas purifying device.
[0031] Moreover, if the temperature of the exhaust gas discharged
from the internal combustion engine is high such as when in the
high-load operation and if the temperature of the exhaust gas
temperature increasing catalyst has already been high, the
high-temperature exhaust gas can be restrained from further flowing
into the exhaust gas temperature increasing catalyst. This makes it
possible to restrain the exhaust gas temperature increasing
catalyst from becoming the excessively high temperature. In
addition, if the temperature of the exhaust gas discharged from the
internal combustion engine is low such as when in the low-load
operation, the low-temperature exhaust gas can be restrained from
flowing into the exhaust gas temperature increasing catalyst. This
makes it feasible to restrain the decrease in temperature of the
exhaust gas temperature increasing catalyst.
[0032] Moreover, the exhaust gas flow rate control device selects
the state where the exhaust gas flowing through the exhaust pipe
passes through both of the exhaust gas flow-through area and the
exhaust gas temperature increasing catalyst, whereby the exhaust
gas heated up as it passes through the exhaust gas temperature
increasing catalyst and the exhaust gas not passing through the
exhaust gas temperature increasing catalyst can be flowed in a
properly mixed state thereof into the exhaust gas purifying device.
This enables improvement of controllability of the temperature of
the exhaust gas purifying device.
[0033] Furthermore, according to the present invention, when
heating up the exhaust gas purifying device,
[0034] the reducing agent adding unit may add the reducing agent to
the exhaust gas passing through the exhaust passageway, and the
exhaust gas flow rate control device may control the allocation in
order to make substantially the entire quantity of the exhaust gas
flowing through the exhaust pipe pass through the exhaust gas
temperature increasing catalyst, and
[0035] the exhaust gas flow rate control device may, after the
reducing agent added from the reducing agent adding unit has
reached the exhaust gas temperature increasing catalyst, control
the allocation in order to decrease, in the exhaust gas flowing
through the exhaust pipe, the quantity of the exhaust gas passing
through the exhaust gas temperature increasing catalyst.
[0036] Namely, in the case of heating up the exhaust gas purifying
device as described above, it is desirable that the
high-temperature exhaust gas be flowed into the exhaust gas
purifying device. For attaining this, the reducing agent adding
unit adds the reducing agent to the exhaust gas flowing through the
exhaust passageway, and the exhaust gas flow rate control device
controls the allocation in order for the exhaust gas temperature
increasing catalyst to admit the passage of substantially the
entire quantity of the exhaust gas flowing trough the exhaust pipe.
Under this control, the reducing agent added from the reducing
agent adding unit can be efficiently led to the exhaust gas
temperature increasing catalyst.
[0037] Then, after the reducing agent added from the reducing agent
adding unit has reached the exhaust gas temperature increasing
catalyst, the exhaust gas flow rate control device controls, in the
exhaust gas flowing through the exhaust pipe, the allocation in
order to decrease the quantity of the exhaust gas passing through
the exhaust gas temperature increasing catalyst. The allocation
being thus controlled, after the reducing agent has reached the
exhaust gas temperature increasing catalyst, the flow rate of the
exhaust gas passing though the exhaust gas temperature increasing
catalyst decreases, and therefore the reducing agent can be
restrained from passing intact through the exhaust gas temperature
increasing catalyst. Then, the reducing agent can be stayed for a
sufficiently long period of time in the exhaust gas temperature
increasing catalyst. As a result, the sufficient reducing reaction
can be caused in the exhaust gas temperature increasing catalyst,
and the temperature of the exhaust gas discharged from the exhaust
gas temperature increasing catalyst can be increased more
surely.
[0038] Further, according to the present invention, the exhaust gas
flow rate control device may, during a decelerating operation of a
vehicle mounted with the internal combustion engine, control the
allocation in order to decrease, in the exhaust gas flowing through
the exhaust pipe, the quantity of the exhaust gas passing through
the exhaust gas temperature increasing catalyst.
[0039] Herein, during a decelerating operation of the internal
combustion engine, there is a case where the temperature of the
exhaust gas discharged from the internal combustion engine
decreases. Then, in such a case, when the low-temperature exhaust
gas passes through the exhaust gas temperature increasing catalyst,
the temperature of the exhaust gas temperature increasing catalyst
decreases, and there is a possibility that the temperature of the
exhaust gas becomes hard to increase efficiently. Herein, the
exhaust gas temperature increasing catalyst often has a smaller
thermal capacity than the exhaust gas purifying device has, and
hence there are many cases in which the temperature thereof
especially tends to decrease due to the passage of the
low-temperature exhaust gas.
[0040] By contrast, during the decelerating operation of the
vehicle mounted with the internal combustion engine, the exhaust
gas flow rate control device may, in the exhaust gas flowing
through the exhaust pipe, decrease the quantity of the exhaust gas
passing through the exhaust gas temperature increasing catalyst.
With this operation, if the temperature of the exhaust gas
discharged from the internal combustion engine is low, it is
possible to decrease the quantity of the exhaust gas passing
through the exhaust gas temperature increasing catalyst and to
restrain the drop in temperature of the exhaust gas temperature
increasing catalyst.
[0041] It should be noted that the means for solving the problems
in the invention can be used by combining these means as much as
possible.
BRIEF DESCRIPTION OF DRAWINGS
[0042] FIG. 1 is a view showing an internal combustion engine
according to a first embodiment of the present invention and
showing outlines of configurations of an exhaust system and a
control system thereof;
[0043] FIG. 2 is a flowchart showing an exhaust gas purifying
device temperature increasing routine in the first embodiment of
the present invention;
[0044] FIG. 3 is a flowchart showing another example of the exhaust
gas purifying device temperature increasing routine in the first
embodiment of the present invention;
[0045] FIG. 4 is a view showing an exhaust gas temperature
increasing device according to a second embodiment of the present
invention and showing an outline of configuration of an exhaust gas
purifying device;
[0046] FIG. 5 is a view showing the exhaust gas temperature
increasing device according to the second embodiment of the present
invention and showing another mode of the outline of configuration
of the exhaust gas purifying device; and
[0047] FIG. 6 is a view showing the exhaust gas temperature
increasing device according to the second embodiment of the present
invention and showing still another mode of the outline of
configuration of the exhaust gas purifying device.
DETAILED DESCRIPTION
[0048] An in-depth description of a best mode for carrying out the
present invention will hereinafter be given in an exemplifying
manner with reference to the drawings.
First Embodiment
[0049] FIG. 1 is a view showing an internal combustion engine
according to a first embodiment and showing outlines of
configurations of an exhaust system and a control system thereof.
An internal combustion engine 1 shown in FIG. 1 is classified as a
diesel engine. Note that an interior of the internal combustion
engine 1 and an intake system thereof are omitted in FIG. 1.
[0050] In FIG. 1, an exhaust pipe 5, through which an exhaust gas
discharged from the internal combustion engine 1 flows, is
connected to the internal combustion engine 1 and is further
connected downstream to an unillustrated silencer. Moreover, an
exhaust gas purifying device 10, which purifies the exhaust gas
from NOx and particulate matters (e.g., soot), is disposed
downstream in the exhaust pipe 5. Then, an exhaust gas temperature
increasing device 11, which increases the temperature of the
exhaust gas purifying device 10 by increasing a temperature of the
exhaust gas flowing into the exhaust gas purifying device 10, is
disposed upstream of the exhaust gas purifying device 10 in the
exhaust pipe 5.
[0051] This exhaust gas temperature increasing device 11 is
partitioned by a partition pipe 11a having approximately the same
diameter as a diameter of the exhaust pipe 5 off into an internal
pipe portion 11b and an external pipe portion 11c. Then, the
internal pipe portion 11b is provided with a flow rate control
valve 11d that determines how a flow rate of the exhaust gas
flowing through the internal pipe portion 11b and a flow rate of
the exhaust gas flowing through the external pipe portion 11c are
allocated by changing a flow rate of the exhaust gas passable
through the internal pipe portion 11b. Further, the external pipe
portion 11c is provided with an oxidation catalyst 11e having
oxidation capability so that the external pipe portion 11c is
filled with the oxidation catalyst 11e. Moreover, a fuel adding
valve 12 for adding a fuel as a reducing agent to the exhaust gas
flowing through the exhaust pipe 5 is disposed on the upstream side
of the exhaust gas temperature increasing device 11 in the exhaust
pipe 5.
[0052] Herein, the exhaust gas temperature increasing device 11
corresponds to exhaust gas temperature increasing unit. Further,
the oxidation catalyst 11e corresponds to an exhaust gas
temperature increasing catalyst. Moreover, the internal pipe
portion 11b corresponds to an exhaust gas flow-through area. The
fuel adding valve 12 corresponds to reducing agent adding unit.
Still further, the flow rate control valve 11d configures an
exhaust gas flow rate control device.
[0053] The exhaust gas purifying device 10 in the first embodiment
is a device constructed so that a wall-flow type filter composed of
a porous base material supports an oxidation catalyst typified by
platinum (Pt) and NOx occlusion agent typified by potassium (K) and
cesium (Cs). The exhaust gas purifying device 10 does not
necessarily have to, however, be a device that support the NOx
occlusion agent, wherein, for example, the NOx catalyst may be
separately independently provided in the exhaust pipe 5.
[0054] In the thus-constructed internal combustion engine 1 and the
exhaust system thereof, an electronic control unit (ECU) 35 for
controlling the internal combustion engine 1 and the exhaust
system, is provided. This ECU 35 is a unit for performing, in
addition to controlling an operating state etc of the internal
combustion engine 1 in accordance with operating conditions of the
internal combustion engine 1 and in response to a request of a
driver, the control of an exhaust gas purifying system including
the exhaust gas purifying device 10, the exhaust gas temperature
increasing device 11 and the fuel adding valve 12.
[0055] Unillustrated sensors related to the control of the
operating state of the internal combustion engine 1, such as an
airflow meter, a crank position sensor and an accelerator position
sensor, are connected via electric wirings to the ECU 35, wherein
output signals of these sensors are inputted to the ECU 35. On the
other hand, an unillustrated fuel injection valve etc for
combustion in the internal combustion engine 1 is connected via the
electric wiring to the ECU 35, and, in addition, the flow rate
control valve 11d, the fuel adding valve 12 etc in the first
embodiment are connected via the electric wirings to the ECU 35,
whereby these connected components are controlled.
[0056] Further, the ECU 35 is equipped with a CPU (Central
Processing Unit), a ROM (Read-Only Memory), a RAM (Random Access
Memory) etc, wherein the ROM is preinstalled with programs for
executing various categories of control of the internal combustion
engine 1 and is stored with a map registered with data. The
programs preinstalled in the ROM of the ECU 35 include, as one
category of the program, a PM regenerating process routine (of
which an explanation is omitted) for regenerating PM trapping
(scavenging) capability of the exhaust gas purifying device 10, a
NOx reduction process routine for reducing and thus purifying the
NOx occluded in the NOx catalyst in the exhaust gas purifying
device 10, similarly a SOx regenerating process routine (of which
an explanation is omitted) for reducing and thus purifying SOx
occluded in the NOx catalyst in the exhaust gas purifying device
10, and, in addition, an exhaust gas purifying device temperature
increasing routine in the first embodiment, which will be described
later on.
[0057] By the way, when starting up the internal combustion engine
1 according to the first embodiment, if a temperature of the
exhaust gas purifying device 10 is low, there might be a case in
which the NOx catalyst in the exhaust gas purifying device 10 does
not yet reach an activation temperature and is therefore incapable
of sufficiently purifying the NOx in the exhaust gas that is
discharged from the internal combustion engine 1. Then, the exhaust
gas discharged from the internal combustion engine 1 is released
without purifying the exhaust gas of the NOx, and such a
possibility might arise that the emission is deteriorated.
[0058] Such being the case, the first embodiment shall take such a
contrivance that when starting up the internal combustion engine 1,
if the temperature of the exhaust gas purifying device 10 is low, a
quantity of the exhaust gas passing though the internal pipe
portion 11b is decreased or zeroed by driving the flow rate control
valve 11d on a valve-closing side, and the fuel is added as a
reducing agent from the fuel adding valve 12.
[0059] With this contrivance, the fuel added from the fuel adding
valve 12 is efficiently supplied to the oxidation catalyst 11e, and
reducing reaction is efficiently caused in the oxidation catalyst
11e, thereby increasing the temperature of the exhaust gas
discharged from the oxidation catalyst 11e. This operation enables
the high-temperature exhaust gas to flow into the exhaust gas
purifying device 10, whereby the exhaust gas purifying device 10
can be immediately warmed up.
[0060] On this occasion, in the first embodiment, the exhaust gas
temperature increasing device 11 is disposed within the exhaust
pipe 5 without branching the exhaust pipe 5 configuring an exhaust
passageway. To be specific, the internal pipe portion 11b and the
external pipe portion 11c are provided within the exhaust pipe 5,
and the oxidation catalyst 11e is disposed so that the external
pipe portion 11c is filled with the oxidation catalyst 11e. With
this contrivance, as compared with a configuration of branching off
into the exhaust passageway containing the oxidation catalyst and a
bypath, the exhaust gas temperature increasing device 11 can be
downsized on the whole, and mountability onto a vehicle can be
improved. Further, cost reduction can be attained. Still further,
the exhaust gas temperature increasing device 11 takes a
configuration that makes it harder for the heat of reaction that is
generated in the oxidation catalyst 11e to effuse outside than in
the configuration of branching off into the exhaust passageway
containing the oxidation catalyst and the bypath, and hence a heat
retaining property of the oxidation catalyst 11e can be
improved.
[0061] Yet further, in the first embodiment, the oxidation catalyst
11e is disposed in the external pipe portion 11c within the exhaust
pipe 5, and therefore the high-temperature exhaust gas can be
supplied concentratedly to an outer peripheral portion of a front
edge surface of the exhaust gas purifying device 10. As a result, a
central portion of the front edge surface of the exhaust gas
purifying device 10 can be restrained from having a excessively
higher temperature than at the outer peripheral portion, whereby
the exhaust gas purifying device 10 can be uniformly warmed up on
the whole.
[0062] Next, the detailed control on the occasion of warming up the
exhaust gas purifying device 10 in the first embodiment will be
explained. FIG. 2 shows the exhaust gas purifying device
temperature increasing routine in the first embodiment, and this is
a routine for increasing a temperature of the NOx catalyst up to
the activation temperature if the NOx catalyst of the exhaust gas
purifying device 10 does not yet reach the activation temperature.
This routine is executed by the ECU 35 at an interval of
predetermined time during the operation of the internal combustion
engine 1.
[0063] Upon executing this routine, to start with, in S101, a
catalyst temperature T defined as the temperature of the NOx
catalyst of the exhaust gas purifying device 10 is acquired. This
catalyst temperature T may be deduced in a way that detects a
temperature of cooling water of the internal combustion engine 1 by
use of an unillustrated cooling water temperature sensor, and the
temperature of the exhaust gas discharged from the exhaust gas
purifying device 10 may also be detected directly by an
unillustrated exhaust gas temperature sensor. Alternatively, a
relationship between elapsed time since the startup of the internal
combustion engine 1 has begun and the catalyst temperature T, is
previously obtained, and the catalyst temperature T may also be
deduced from the elapsed time since the startup of the internal
combustion engine 1 has begun. When finishing the process in S101,
the operation proceeds to S102.
[0064] In S102, it is judged whether the catalyst temperature T is
equal to or higher than the activation temperature of the NOx
catalyst in the exhaust gas purifying device 10. Then, when judging
that the catalyst temperature T is equal to or higher than the
activation temperature of the NOx catalyst in the exhaust gas
purifying device 10, the exhaust gas purifying device 10 is judged
to be in a state capable of purifying the exhaust gas of the NOx
that is discharged from the internal combustion engine 1, and hence
the operation proceeds to S107.
[0065] In S107, the flow rate control valve 11d is fully opened.
Through this valve opening, the exhaust gas discharged from the
internal combustion engine 1 flows directly into the exhaust gas
purifying device 10 and is purified of the NOx therein.
[0066] While on the other hand, when judging in S102 that the
catalyst temperature T is lower than the activation temperature,
the catalyst temperature T must be raised up to the activation
temperature or higher as soon as possible, and therefore the
operation proceeds to S103. In S103, the flow rate control valve
11d is fully closed. Through this operation, it follows that
substantially an entire quantity of the exhaust gas from the
internal combustion engine 1 flows into the oxidation catalyst 11e.
When terminating the process in S103, the operation proceeds to
S104.
[0067] In S104, the fuel serving as the reducing agent is added
from the fuel adding valve 12 to the exhaust gas flowing through
the exhaust pipe 5. The fuel being thus added, it follows that the
fuel added from the fuel adding valve 12 is carried together with
substantially the entire quantity of exhaust gas getting to flow to
the oxidation catalyst 11e and is thus supplied to the oxidation
catalyst 11e. When finishing the process in S104, the operation
proceeds to S105.
[0068] In S105, it is judged whether or not the fuel added from the
fuel adding valve 12 reaches the oxidation catalyst 11e. Herein,
the judgment that the fuel added from the fuel adding valve 12
reaches the oxidation catalyst 11e may be made by reading, into the
ECU 35, an output of an unillustrated air-fuel ratio sensor
provided upstream immediately of the oxidation catalyst 11e, and
may also be made by knowing that the temperature of the oxidation
catalyst 11e starts abruptly increasing. Moreover, a relationship
between the operating state of the internal combustion engine 1 and
a period of time till the fuel added from the fuel adding valve 12
reaches the oxidation catalyst 11e, is mapped beforehand, and the
above judgment may be made based on whether or not there is an
elapse of the time read from the map in accordance with the
operating state of the internal combustion engine 1 when executing
the exhaust gas purifying device temperature increasing routine
since the fuel has been added from the fuel adding valve 12.
[0069] If it is judged in S105 that the fuel does not yet reach the
oxidation catalyst 11e, the operation returns to a status before
the process in S105, wherein it is again judged in S105 whether the
fuel added from the fuel adding valve 12 reaches the oxidation
catalyst 11e or not. Then, the process in S105 is repeatedly
executed till judging that the fuel reaches the oxidation catalyst
11e. Subsequently, when judging in S105 that the fuel reaches the
oxidation catalyst 11e, the operation proceeds to S106.
[0070] In S106, the full-close of the flow rate control valve 11d
is cancelled, and the flow rate control valve 11d is opened to a
predetermined opening degree. With this valve opening, the flow
rate of the exhaust gas flowing to the oxidation catalyst 11e
decreases. The operation being thus done, the fuel reaching the
oxidation catalyst 11e can be restrained from passing intact
through the oxidation catalyst 11e within a short period of time
and can be made to stay within the oxidation catalyst 11e over a
sufficient period of time. As a result, the temperature of the
exhaust gas after passing through the oxidation catalyst 11e can be
sufficiently increased, and the exhaust gas purifying device 10 can
be heated up quickly. Further, a fuel consumption for heating up
the exhaust gas purifying device 10 can be decreased.
[0071] Herein, the predetermined opening degree is an opening
degree capable of sufficiently restraining the fuel reaching the
oxidation catalyst 11e from passing intact through the oxidation
catalyst 11e and amply supplying the exhaust gas having its
temperature increased in the oxidation catalyst 11e to the exhaust
gas purifying device 10 in order to increase the temperature of the
exhaust gas purifying device 10. This predetermined opening degree
may be previously mapped in relation with the operating state of
the internal combustion engine land may be, when executing S106,
derived by reading from the map the opening degree corresponding to
the operating state of the internal combustion engine 1 on this
occasion. When terminating the process in S106, the present routine
is finished for the meantime.
[0072] As discussed so far, the catalyst temperature increasing
routine in the first embodiment is that if the temperature of the
NOx catalyst in the exhaust gas purifying device 10 is lower than
the activation temperature, the flow rate control valve 11d is
fully closed, and the fuel is added into the exhaust gas from the
fuel adding valve 12, thereby making it possible to ensure
transportability enough for having the added fuel reached the
oxidation catalyst 11e.
[0073] Further, after the fuel has reached the oxidation catalyst
11e, the flowrate control valve 11d is opened, and the exhaust gas
from the internal combustion engine 1 flows to both of the external
pipe portion 11c and the internal pipe portion 11b, whereby the
fuel reaching the oxidation catalyst 11e can be refrained from
passing intact through the oxidation catalyst 11e within the short
period of time, and the exhaust gas the temperature of which has
been increased by the reducing reaction in the oxidation catalyst
11e can be supplied more surely to the exhaust gas purifying device
10.
[0074] Note that in the exhaust gas purifying system described
above, if the operating state of the internal combustion engine 1
is a decelerating state, after the fuel added from the fuel adding
valve 12 has reached the oxidation catalyst 11e, the flowrate
control valve 11d may be opened to a much larger opening degree,
and an inflow quantity of the exhaust gas discharged from the
internal combustion engine 1 into the oxidation catalyst 11e may
thus be decreased to a greater degree. The operation being done so,
the low-temperature exhaust gas in the decelerating state of the
internal combustion engine 1 can be refrained from flowing into the
oxidation catalyst 11e, and the oxidation catalyst 11e can be also
restrained from being cooled down.
[0075] FIG. 3 shows an example of the exhaust gas purifying device
temperature increasing routine in that case. A different point
between the control in the present routine and the control in FIG.
2 is that in the present routine, after judging in S105 that the
fuel reaches the oxidation catalyst 11e, the operation proceeds to
not S106 but S201. It is judged in S201 whether the internal
combustion engine 1 is in the decelerating state or not. To be
specific, an output of an unillustrated accelerator position sensor
is read into the ECU 35, and it may be judged whether an
accelerator tread-on quantity obtained from this value is zero or
not. A state where the accelerator is not trodden on may be defined
as the decelerating state.
[0076] When judging in S201 that the internal combustion engine 1
is in the decelerating state, it is judged that if the flow rate
control valve 11d is opened to the predetermined opening degree,
and the exhaust gas from the internal combustion engine 1 is
supplied to both of the internal pipe portion 11b and the external
pipe portion 11c containing the oxidation catalyst 11e as explained
in FIG. 2, the oxidation catalyst 11e is cooled down conversely.
Hence, the operation proceeds to S107, wherein the flow rate
control valve 11d is fully opened. Whereas if it is judged in S201
that the internal combustion engine 1 is not in the deceleration
state, as described in FIG. 2, the operation proceeds to S106.
[0077] If done so, even in the case the internal combustion engine
1 is in the decelerating state and the reducing reaction occurs in
the oxidation catalyst 11e due to the fuel added from the fuel
adding valve 12, it is feasible to restrain an occurrence of the
situation that the oxidation catalyst 11e is cooled down by the
low-temperature exhaust gas. As a result, the exhaust gas purifying
device 10 can be warmed up more surely.
[0078] It should be noted that in the first embodiment, when the
internal combustion engine 1 is judged to be in the decelerating
state in S201, if the flowrate control valve 11d is fully opened in
S107, it follows that the low-temperature exhaust gas flows
directly into the exhaust gas purifying device 10. In this case
also, however, the exhaust gas purifying device 10 has a larger
thermal capacity than the oxidation catalyst 11e has, and hence
such a problem, it is considered, is hard to occur that the exhaust
gas purifying device 10 itself is cooled quickly down to the low
temperature.
[0079] Moreover, other than what has been discussed above, after
finishing the warm-up of the internal combustion engine 1 in the
first embodiment and when the exhaust gas purifying device
temperature increasing routine is not executed, if the internal
combustion engine 1 gets into the decelerating state, such control
may also be conducted that the flow rate control valve 11d be fully
opened. This control being thus conducted, after finishing the
warm-up of the internal combustion engine 1, it is possible to
restrain the low-temperature exhaust gas from flowing into the
oxidation catalyst 11e reaching the activation temperature or
higher and also to restrain the oxidation catalyst 11e reaching at
last the activation temperature or higher from being cooled
down.
Second Embodiment
[0080] Next, a second embodiment of the present invention will be
described. The second embodiment will exemplify another
configuration of the exhaust gas temperature increasing device 11
explained in FIG. 1.
[0081] FIG. 4 is a view showing an outline of the configuration of
the exhaust gas temperature increasing device 11 in the second
embodiment. A first mode of the second embodiment is that as
illustrated in FIG. 4 (A), an exhaust gas purifying device 20 and
an exhaust gas temperature increasing device 21 are substantially
equalized in their diameters and are provided within a pipe having
the same diameter. According to the first mode, the exhaust gas can
be more smoothly flowed into the exhaust gas purifying device 20
without disturbing the flow of the exhaust gas discharged from the
exhaust gas temperature increasing device 21. Further, especially
when an oxidation catalyst 21e is provided in an external pipe
portion 21c, the high-temperature exhaust gas discharged from the
oxidation catalyst 21e can be more surely flowed into the outer
peripheral portion of the exhaust gas purifying device 20, with the
result that the temperature of the exhaust gas purifying device 20
can be more certainly uniformly increased. Moreover, according to
the first mode, a stepped portion 21f in FIG. 4(A) is not
positioned between the exhaust gas temperature increasing device 21
and the exhaust gas purifying device 20. It is therefore possible
to restrain a large amount of heat from escaping outwardly of the
exhaust pipe 5 because the exhaust gas discharged from the
oxidation catalyst 21e flows against the stepped portion 21f.
[0082] Furthermore, FIG. 4 (B) illustrates another mode of the
second embodiment. In FIG. 4 (B), the oxidation catalyst 21e is
provided not in the external pipe portion 21c but in an internal
pipe portion 21b. With this arrangement, the oxidation catalyst 21e
does not abut on the external portion of the exhaust pipe 5,
whereby the heat retaining property of the oxidation catalyst 21e
can be more enhanced.
[0083] Moreover, as shown in FIG. 5, such a mode may be taken that
the exhaust gas purifying device 20 is partially inserted into the
internal pipe portion 21b. FIG. 5(A) shows a state where the flow
rate control valve 21d is opened, while FIG. 5(B) shows a state
where the flow rate control valve 21d is fully closed. According to
the present mode, even when the exhaust gas purifying device 20 has
a large capacity, the whole configuration including the exhaust gas
temperature increasing device 21 and the exhaust gas purifying
device 20 can be downsized, and the mountability on the vehicle can
be improved.
[0084] Further, FIG. 6 illustrates still another mode of the second
embodiment. In FIG. 6(A), an electro-thermic heater 21g is provided
in the oxidation catalyst 21e. Then, when heating up the exhaust
gas purifying device 20, to begin with, the electro-thermic heater
21g is electrified to emit the heat, thereby increasing the
temperature of the oxidation catalyst 21e itself. When done so, it
is feasible to increase the temperature of the oxidation catalyst
21e itself over the activation temperature more surely and to raise
the temperature of the exhaust gas flowing into the exhaust gas
purifying device 20 more certainly.
[0085] Further, in FIG. 6(B), a glow plug 21h is provided upstream
immediately of the oxidation catalyst 21e. Then, when heating up
the exhaust gas purifying device 20, at first, the glow plug 21h is
electrified to emit the heat, the temperature of the oxidation
catalyst 21e itself is increased, and the temperature of the
exhaust gas passing through the external pipe portion 21c is
raised. Then, the fuel is added from the fuel adding valve 12. With
this operation, the temperature of the oxidation catalyst 21e
itself can be increased over the activation temperature with more
of the certainty, and the temperature of the exhaust gas discharged
from the oxidation catalyst 21e can be further increased.
Accordingly, the temperature of the exhaust gas flowing into the
exhaust gas purifying device 20 can be raised more certainly.
[0086] It is to be noted that the embodiments discussed above have
exemplified the case of warming up the exhaust gas purifying device
10 or 20 when starting up the internal combustion engine 1. In
addition, the configurations and the control in the embodiments
discussed above may be applied to a case of increasing the
temperature of the NOx catalyst or of the filter in a SOx poisoning
recovery process and in the PM regenerating process of the filter
in the exhaust gas purifying device 10 or 20.
[0087] Further, the embodiments discussed above have exemplified
the example of adding the fuel as the reducing agent from the fuel
adding valve 12, however, these embodiments may be applied to the
exhaust gas purifying system that involves using urea water as the
reducing agent. Moreover, these embodiments may also be applied to
the exhaust gas purifying system of the internal combustion engine
other than the diesel engine. In addition, these embodiments may
also be applied to the exhaust gas purifying system adding the fuel
as the reducing agent by executing the sub-injection such as VIGOM
injection, POST injection, etc., from a fuel injection valve of the
internal combustion engine.
[0088] Moreover, the configuration of the exhaust gas purifying
system according to the present invention is not limited to the
configurations in the embodiments discussed above and can be
modified as far as these modifications are within the range of the
technical idea of the present invention. For example, full-close
state of the flow rate control valve 11d in the embodiments
discussed above does not necessarily mean completely closed state
of valve. It can include the state that the flow rate control valve
11d is closed to a sufficiently small opening degree with which
substantially an entire quantity of the exhaust gas from the
internal combustion engine 1 can flow into the oxidation catalyst
11e.
INDUSTRIAL APPLICABILITY
[0089] According to the present invention, the temperature of the
exhaust gas purifying device in the exhaust system of the internal
combustion engine can be increased more efficiently or more surely
with the much simpler configuration.
* * * * *