U.S. patent application number 11/392683 was filed with the patent office on 2006-11-09 for exhaust gas purification apparatus for engine.
Invention is credited to Hisashi Akagawa, Kiminobu Hirata, Shuichi Nakamura, Ikuo Sakai, Hiroki Ueno.
Application Number | 20060248880 11/392683 |
Document ID | / |
Family ID | 34425315 |
Filed Date | 2006-11-09 |
United States Patent
Application |
20060248880 |
Kind Code |
A1 |
Hirata; Kiminobu ; et
al. |
November 9, 2006 |
Exhaust gas purification apparatus for engine
Abstract
An exhaust gas purification apparatus of an engine having a
reduction catalytic converter arranged in an engine exhaust gas
system, for reducing and purifying nitrogen oxide by a liquid
reducing agent, a reducing agent supply device controlling a flow
rate of a liquid reducing agent that is supplied to the reduction
catalytic converter, depending on engine operating conditions, an
injection nozzle secured to the exhaust system via a flange, for
injection-supplying the liquid reducing agent into exhaust gas at a
position upstream of the reduction catalytic converter, and piping
providing a fluid communication between the reducing agent supply
device and the injection nozzle. The piping is constructed of a
material made of ceramics, or water repellency treatment is applied
to the inner wall of at least one of the injection nozzle and the
piping.
Inventors: |
Hirata; Kiminobu; (Ageo,
JP) ; Akagawa; Hisashi; (Ageo, JP) ; Nakamura;
Shuichi; (Ageo, JP) ; Ueno; Hiroki; (Ageo,
JP) ; Sakai; Ikuo; (Ageo, JP) |
Correspondence
Address: |
BAKER & HOSTETLER LLP
WASHINGTON SQUARE, SUITE 1100
1050 CONNECTICUT AVE. N.W.
WASHINGTON
DC
20036-5304
US
|
Family ID: |
34425315 |
Appl. No.: |
11/392683 |
Filed: |
March 30, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP04/12744 |
Sep 2, 2004 |
|
|
|
11392683 |
Mar 30, 2006 |
|
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Current U.S.
Class: |
60/286 ; 60/295;
60/301 |
Current CPC
Class: |
F01N 2510/14 20130101;
F01N 2610/02 20130101; F01N 2610/1453 20130101; F01N 3/2066
20130101; F01N 2610/11 20130101; Y02T 10/24 20130101; F01N 2510/00
20130101; Y02T 10/12 20130101 |
Class at
Publication: |
060/286 ;
060/295; 060/301 |
International
Class: |
F01N 3/00 20060101
F01N003/00; F01N 3/10 20060101 F01N003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 30, 2003 |
JP |
2003-339245 |
Sep 30, 2003 |
JP |
2003-341586 |
Claims
1. An exhaust gas purification apparatus of an engine comprising: a
reduction catalytic converter arranged in an engine exhaust system,
for reducing and purifying nitrogen oxide by a liquid reducing
agent; a reducing agent supply device that controls a flow rate of
a liquid reducing agent that is supplied to said reduction
catalytic converter, depending on engine operating conditions; an
injection nozzle that is secured to said exhaust system via a
flange, for injection-supplying the liquid reducing agent into
exhaust gas at a position upstream of said reduction catalytic
converter; and piping that provides a fluid communication between
said reducing agent supply device and said injection nozzle,
wherein said piping is constructed from a material made of
ceramics.
2. The exhaust gas purification apparatus of an engine according to
claim 1, wherein cooling fins are provided and disposed in rows on
said flange.
3. The exhaust gas purification apparatus of an engine according to
claim 1, wherein a coolant is permitted to flow through said
flange.
4. The exhaust gas purification apparatus of an engine according to
claim 1, wherein an insulating material gasket is interposed
between said exhaust system and said flange.
5. An exhaust gas purification apparatus of an engine comprising: a
reduction catalytic converter arranged in an engine exhaust system,
for reducing and purifying nitrogen oxide by a liquid reducing
agent; a reducing agent supply device that controls a flow rate of
a liquid reducing agent that is supplied to said reduction
catalytic converter, depending on engine operating conditions; an
injection nozzle that injection-supplies the liquid reducing agent
into exhaust gas at a position upstream of said reduction catalytic
converter; and piping that provides a fluid communication between
said reducing agent supply device and said injection nozzle,
wherein a water repellency treatment is applied to an inner wall of
at least one of said injection nozzle and said piping.
6. The exhaust gas purification apparatus of an engine according to
claim 5, wherein said water repellency treatment is a fluorocarbon
resin treatment.
7. The exhaust gas purification apparatus of an engine according to
claim 5, wherein said water repellency treatment is an organic
plating treatment.
8. The exhaust gas purification apparatus of an engine according to
claim 5, wherein said piping is arranged to have an axis thereof
extending in a substantially vertical direction, and said injection
nozzle is connected to a lower end of said piping.
Description
[0001] This application is a continuation of PCT/JP2004/012744,
filed on May 6, 2005.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an exhaust gas purification
apparatus for an engine (referred to hereunder as "exhaust gas
purification apparatus"), which reduces the nitrogen oxide (NOx) in
the exhaust gas using a liquid reducing agent. In particular, it
relates to technology for suppressing clogging in the injection
nozzle and its associated piping.
[0004] 2. Description of the Related Art
[0005] As an exhaust gas purification system for purifying NOx
contained in engine exhaust gas, the exhaust gas purification
apparatus disclosed in Japanese Unexamined Patent Publication No.
2000-27627 has been proposed.
[0006] In such an exhaust gas purification apparatus, NOx is
purified into harmless constituents by arranging a reduction
catalytic converter in the engine exhaust system, and a reducing
agent is injection-supplied into the exhaust gas at an upstream
side of the reduction catalytic converter, to thereby cause a
catalytic reduction reaction between the reducing agent and NOx in
the exhaust gas. The reducing agent is of liquid state at the room
temperature and is stored in a storage tank, and a necessary amount
depending on engine operating conditions, is injection-supplied
from an injection nozzle. Here, as the reducing agent, a liquid
reducing agent such as a urea aqueous solution, an ammonia aqueous
solution, or diesel oil whose main constituent is hydrocarbons, is
used.
[0007] However, depending on the engine operating conditions, the
amount of NOx in the exhaust gas is sometimes small, and NOx
purification by a reduction catalytic converter is not necessary.
Therefore, in view of avoiding unnecessary consumption of the
liquid reducing agent, a construction in which the liquid reducing
agent is injection-supplied into the exhaust gas at an upstream
side of the reduction catalytic converter intermittently depending
on the engine operating conditions is adopted. In the case where
such a construction is adopted, after the injection-supply of the
liquid reducing agent stops, there is concern that the liquid
reducing agent solidifies inside the injection nozzle and its
associated piping causing them to be clogged, and the liquid
reducing agent can no longer be injection-supplied. That is,
immediately after the injection-supply of the liquid reducing agent
is stopped, liquid drops of the liquid reducing agent are attached
to the inside of the injection nozzle and its associated piping.
Then, the temperatures of the injection nozzle and its associated
piping increase due to the exhaust heat, since they are directly
exposed to the high temperature exhaust gas, and the water content
from the liquid reducing agent evaporates and the reducing agent
constituents are deposited. When the injection nozzle and its
associated piping become clogged and are unable to injection-supply
the liquid reducing agent, NOx purification by the reduction
catalytic converter can no longer be expected, and hence exhaust
gas having a large amount of NOx must be emitted into the
atmosphere.
SUMMARY OF THE INVENTION
[0008] Therefore, the present invention takes the above-described
existing problems into consideration, with an object of providing
an exhaust gas purification apparatus in which clogging is
suppressed by reducing the volume unrelated to injection-supply of
a liquid reducing agent, or by applying a water repellency
treatment to at least one of the injection nozzle and its
associated piping.
[0009] In accordance with a first embodiment of the present
invention, an exhaust gas purification apparatus of an engine is
provided, which comprises: a reduction catalytic converter arranged
in an engine exhaust system, for reducing and purifying nitrogen
oxide by a liquid reducing agent; a reducing agent supply device
that controls a flow rate of a liquid reducing agent supplied to
the reduction catalytic converter, depending on engine operating
conditions; an injection nozzle that is secured to the exhaust
system via a flange, for injection-supplying the liquid reducing
agent into exhaust gas at a position upstream of the reduction
catalytic converter; and piping that provides a fluid communication
between the reducing agent supply device and the injection nozzle,
the exhaust gas purification apparatus being provided with such a
configuration that the piping is constructed from a material made
of ceramics.
[0010] In this case, cooling fins may be disposed in rows on the
flange, or a coolant may be flowed through the flange. Moreover, an
insulating material gasket may be interposed between the exhaust
system and the flange.
[0011] In accordance with a second embodiment of the present
invention, an exhaust gas purification apparatus of an engine is
provided, which comprises: a reduction catalytic converter arranged
in an engine exhaust system, for reducing and purifying nitrogen
oxide by a liquid reducing agent; a reducing agent supply device
that controls a flow rate of a liquid reducing agent that is
supplied to the reduction catalytic converter, depending on engine
operating conditions; an injection nozzle that injection-supplies
the liquid reducing agent into exhaust gas at a position upstream
of the reduction catalytic converter; and piping that provides a
fluid communication between the reducing agent supply device and
the injection nozzle, the exhaust gas purification apparatus is
provided with such a configuration that a water repellency
treatment is applied to an inner wall of at least one of the
injection nozzle and the piping.
[0012] In this case, a fluorocarbon resin treatment or an organic
plating treatment can be applied as the water repellency treatment.
Moreover, the piping may be arranged to have an axis thereof
extending in a substantially vertical direction, and the injection
nozzle can be connected to a lower end of the piping.
[0013] According to the exhaust gas purification apparatus of the
first embodiment of the present invention, NOx contained in the
engine exhaust gas is reduced and purified in the reduction
catalytic converter, by using the liquid reducing agent supplied
and controlled by the reducing agent supply device. In this case,
because the piping that provides a fluid communication between the
reducing agent supply device and the injection nozzle is
constructed from a material made of ceramics, its coefficient of
thermal conductivity, which is a thermal characteristic, is small.
Therefore the transmission of heat of the exhaust system to the
reducing agent supply device is suppressed. Thus, even if the
reducing agent supply device is positioned close to the exhaust
system, an increase in its temperature in use is prevented, and a
predetermined environment of its usage can be fulfilled. Moreover,
as a result of enabling the reducing agent supply device to be
positioned close to the exhaust system, the length of the piping
can be shorter, and the volume unrelated to the injection-supply of
the liquid reducing agent can be decreased, so that the liquid
reducing agent attached to the inner walls of the piping and the
injection nozzle immediately after the stopping injection-supply of
the liquid reducing agent is reduced. Therefore, even if the water
content evaporates from the liquid reducing agent due to the
exhaust heat, and the reducing agent constituents are deposited,
the absolute amount thereof becomes too small to cause clogging of
the piping and the injection nozzle.
[0014] On the other hand, after restarting injection-supply of the
liquid reducing agent, the liquid reducing agent flows vigorously
through the piping and the injection nozzle, and hence the reducing
agent constituents that have solidified on the inner walls are
dissolved and discharged into the exhaust system. Therefore, even
if the injection-supply of the liquid reducing agent is performed
intermittently, there is no longer a gradual deposition of the
constituents of the liquid reducing agent on the inner walls of the
piping and the injection nozzle, so that occurrence of clogging is
fully suppressed. Therefore the necessary NOx purification
efficiency can be maintained for a long time.
[0015] According to the exhaust gas purification apparatus of the
second embodiment of the present invention, NOx contained in the
engine exhaust gas is reduced and purified in the reduction
catalytic converter by using the liquid reducing agent supplied by
the reducing agent supply device. In this case, because the water
repellency treatment is applied to the inner wall of at least one
of the injection nozzle and the piping, when the injection-supply
of the liquid reducing agent stops, the remaining liquid reducing
agent therein drops downward, and the amount of urea aqueous
solution held on the inner wall thereof decreases. Therefore, even
if the water content evaporates from the liquid reducing agent due
to the exhaust heat, and the reducing agent constituents are
deposited, the absolute amount thereof becomes too small to cause
clogging of the piping and the injection nozzle.
[0016] On the other hand, after restarting injection-supply of the
liquid reducing agent, the liquid reducing agent flows vigorously
through the piping and the injection nozzle, and hence the reducing
agent constituents that have solidified on the inner walls are
dissolved and discharged into the exhaust system. Therefore, even
if the injection-supply of the liquid reducing agent is performed
intermittently, there is no longer a gradual deposition of the
constituents of the liquid reducing agent on the inner walls of the
piping and the injection nozzle, so that the clogging is fully
suppressed. Therefore the necessary NOx purification efficiency can
be maintained for a long time.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a basic block diagram of an exhaust gas
purification apparatus to which the present invention is
applied;
[0018] FIG. 2 is an enlarged view of a region around the injection
nozzle in FIG. 1;
[0019] FIG. 3 is an explanatory diagram of an air cooling structure
that can be adopted by the first embodiment of the present
invention;
[0020] FIG. 4 is an explanatory diagram of a water cooling
structure that can be adopted by the first embodiment of the
present invention; and
[0021] FIG. 5 is an explanatory diagram of a water repellent layer
according to a second embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] Hereunder is a detailed description of the present
invention, with reference to the appended drawings.
[0023] FIG. 1 shows the basic construction of an exhaust gas
purification apparatus to which the present invention is
applied.
[0024] The exhaust gas of an engine 10 is discharged into the
atmosphere from an exhaust gas manifold 12 via an exhaust pipe 16,
in which a NOx reduction catalytic converter 14 is arranged. In
particular, in the exhaust pipe 16, in order from the exhaust gas
upstream side are respectively arranged; an oxidation catalytic
converter for nitrogen monoxide (NO), a NOx reduction catalytic
converter, and an ammonia oxidation catalytic converter, and before
and after these are arranged a thermal sensor and an oxygen sensor
and the like, to thereby construct the exhaust system, whose detail
is not shown in the figures.
[0025] To the exhaust gas upstream of the NOx reduction catalytic
converter 14, a liquid reducing agent together with air is
injection-supplied from a reducing agent supply device 18 via
piping 20 and an injection nozzle 22. That is, as shown in FIG. 2,
a flange 24 to which the injection nozzle 22 is attached, is
fastened by bolts 26 to the exhaust pipe 16, which is located on an
upstream side of the exhaust gas flow from the NOx reduction
catalytic converter 14, so as to cover an opening portion 16A
opened in the peripheral wall of the exhaust pipe 16. In the
description hereunder, a urea aqueous solution is used as the
liquid reducing agent, however an ammonia aqueous solution, or
diesel oil whose main constituent is hydrocarbons may alternatively
be used. Here the urea aqueous solution is a solution in which
solid or powder urea is dissolved, and it is supplied to the
reducing agent supply device 18 from a storage tank (not
shown).
[0026] The urea aqueous solution that is injection-supplied to the
exhaust gas flow at an upstream position of the NOx reduction
catalytic converter 14 is hydrolyzed due to the exhaust heat and
the steam in the exhaust gas, and ammonia is easily produced. It is
well known that the produced ammonia reacts with NOx in the exhaust
gas, in the NOx reduction catalytic converter 14, and is purified
into water and harmless gas.
[0027] Moreover, a control unit 28 incorporating therein a built-in
computer is provided so as to control the amount of
injection-supply of the urea aqueous solution, depending on engine
operating conditions. The control unit 28 controls the reducing
agent supply device 18 depending on the engine rotating speed and
the fuel injection amount input via a CAN (Controller Area
Network).
[0028] According to the exhaust gas purification apparatus of the
first embodiment of the present invention, the reducing agent
supply device 18 and the injection nozzle 22 are in fluid
communication with one another by means of the piping 20 made of
ceramics.
[0029] According to such a construction, since the reducing agent
supply device 18 and the injection nozzle 22 are connected to have
a fluid communication therebetween via the piping 20 made of
ceramics, its coefficient of thermal conductivity, which is a
thermal characteristic, is small. Therefore, the transmission of
heat of the exhaust pipe 16 to the reducing agent supply device 18
is appreciably suppressed and restricted. Therefore, even if the
reducing agent supply device 18 is positioned close to the exhaust
pipe 16, a temperature rise during the usage of the reducing agent
supply device 18 is fully suppressed, and a predetermined
environmental condition in use can be fulfilled. Moreover, as a
result of enabling the reducing agent supply device 18 to be
positioned close to the exhaust pipe 16, the length of the piping
20 can be shorter, and the pipe volume unrelated to the
injection-supply of the urea aqueous solution can be reduced with
certainty. Therefore, the urea aqueous solution attached to the
inner walls of the piping 20 and the injection nozzle 22
immediately after stopping injection-supply of the urea aqueous
solution is reduced. Therefore, even if the water content
evaporates from the urea aqueous solution due to the exhaust heat,
and the urea is deposited on the inner walls, the absolute amount
thereof becomes too small to cause clogging of the piping 20 and
the injection nozzle 22.
[0030] On the other hand, when the engine operating conditions
change and the injection-supply of the urea aqueous solution is
restarted, the urea aqueous solution and air flows vigorously
through the piping 20 and the injection nozzle 22, and hence the
urea that has solidified on the inner walls is dissolved and
discharged into the exhaust pipe 16. Therefore, even if the
injection-supply of the urea aqueous solution is intermittently
performed, there is no longer a gradual deposition of the urea on
the inner walls of the piping 20 and the injection nozzle 22, and
the injection-supply of the urea aqueous solution depending on the
engine operating conditions is realized. Therefore, the necessary
NOx purification efficiency can be maintained for a long time.
[0031] Moreover, in order to further reduce the heat quantity
transmitted from the exhaust pipe 16 to the reducing agent supply
device 18, as shown FIG. 3, an air cooling structure in which
cooling fins 30 that are made of a material having good thermal
conductivity such as copper are disposed in rows on the flange 24
that covers the opening portion 16A opened in the peripheral wall
of the exhaust pipe 16, may be adopted. Moreover, as shown in FIG.
4, a water cooling structure in which a cooling water passage is
formed inside the flange 24, and engine cooling water or the like
is passed therethrough as a coolant, may be adopted. Both of the
air cooling structure and the water cooling structure in the flange
24 may be adopted.
[0032] By adopting such a cooling structure, the exhaust heat
transmitted from the exhaust pipe 16 to the flange 24 is dissipated
by radiation by means of the cooling fins 30, or is heat exchanged
with the cooling water, thus reducing the heat quantity that is
transmitted to the piping 20. Therefore, the temperature in use of
the reducing agent supply device 18 is reduced, and hence it
becomes possible to position the reducing agent supply device 18
closer to the exhaust pipe 16, and the piping volume that is
unrelated to the injection-supply of the urea aqueous solution is
further reduced. Moreover, since the absolute amount of the urea
aqueous solution that is attached to the inner walls of the piping
20 and the injection nozzle 22 is further reduced, the clogging
thereof can be effectively prevented.
[0033] Furthermore, instead of the air cooling structure or the
water cooling structure, an insulating material gasket can be
interposed between the opening portion 16A of the exhaust pipe 16
and the flange 24. By such a structure, transmission of the heat of
the exhaust pipe 16 to the flange 24 is suppressed, and a similar
effect to the above effects can be achieved. Moreover, in
particular, in addition to the air cooling structure and/or the
water cooling structure, by interposing the insulating material
gasket between the opening portion 16A and the flange 24, the heat
quantity transmitted from the exhaust pipe 16 to the reducing agent
supply device 18 is effectively reduced, and the reducing agent
supply device 18 can be positioned even closer to the exhaust pipe
16.
[0034] FIG. 5 shows the structure of an exhaust gas purification
apparatus according to a second embodiment of the present
invention.
[0035] According to the present embodiment, as a prerequisite for
the basic structure of the exhaust gas purification apparatus shown
in FIGS. 1 and 2, as shown FIG. 5, a water repellent layer 32 is
formed by a fluorocarbon resin treatment or an organic plating
treatment, as a water repellent treatment on the inner walls of the
piping 20 and the injection nozzle 22.
[0036] According to such a structure, since the water repellent
treatment is applied to the inner walls of the piping 20 and the
injection nozzle 22, when the injection-supply of the urea aqueous
solution stops, the urea aqueous solution remaining inside thereof
drops downward, reducing the urea aqueous solution attached to the
inner walls of the piping 20 and the injection nozzle 22.
Therefore, even if the water content evaporates from the urea
aqueous solution due to the exhaust heat, and the urea is deposited
on the inner walls, its absolute amount becomes too small to cause
clogging of the piping 20 and the injection nozzle 22.
[0037] On the other hand, when the engine operating conditions
change and the injection-supply of the urea aqueous solution is
restarted, the urea aqueous solution and air flows vigorously
through the piping 20 and the injection nozzle 22, and hence the
urea that has solidified on the inner walls is dissolved and
discharged into the exhaust pipe 16. Therefore, even if the
injection-supply of the urea aqueous solution is intermittently
performed, there is no longer a gradual build up of the urea on the
inner walls of the piping 20 and the injection nozzle 22, and the
injection-supply of the urea aqueous solution depending on the
engine operating conditions is possible. Therefore the necessary
NOx purification efficiency can be maintained over a long term.
[0038] Moreover, if the fluorocarbon resin treatment is applied as
the water repellent treatment, a decrease in the water repellent
efficiency can be suppressed, even when the piping 20 and the
injection nozzle 22 are heated by the exhaust heat. On the other
hand, by applying the organic plating treatment as the water
repellent treatment, the water repellent efficiency of the piping
20 and the injection nozzle 22 is improved, and also the water
repellent layer 32 is kept from coming off from the inner
walls.
[0039] Moreover, it is preferable that the axis of the piping 20 is
extended in a substantially vertical direction, and the injection
nozzle 22 is connected to the lower end thereof. By such a
structure, when the injection-supply of the urea aqueous solution
stops, the urea aqueous solution inside the piping 20 drops
vertically downward under gravity, and is discharged to the exhaust
pipe 16 from the injection hole of the injection nozzle 22.
Therefore, the amount of the urea aqueous solution attached to the
inner wall of the piping 20 is further reduced, and even if the
water content evaporates from the urea aqueous solution due to the
exhaust heat, and the urea is deposited by precipitation, since its
absolute amount is small, clogging of the piping 20 is further
suppressed.
[0040] In the present embodiment, the water repellent treatment is
applied to both the piping 20 and the injection nozzle 22. However
the water repellent treatment may be applied to only the one of
them that is vulnerable to clogging. Also, if the water repellent
treatment is applied to the inner wall of the piping 20, on only a
particular area that can be heated to a temperature at which the
urea aqueous solution can solidify, the clogging thereof can be
suppressed.
[0041] As described above, in the exhaust gas purification
apparatus according to the present invention, even if when the
injection-supply of the liquid reducing agent stops, the water
content evaporates from the liquid reducing agent remaining in the
injection nozzle and its piping, and the reducing agent
constituents are deposited, its absolute amount is too small to
cause clogging of the piping and the injection nozzle, and hence
this is extremely advantageous.
* * * * *