U.S. patent application number 12/667656 was filed with the patent office on 2010-12-23 for engine powered machine.
This patent application is currently assigned to Hitachi Corporation Machinery Co., Ltd.. Invention is credited to Yasushi Arai, Shohei Kamiya, Kazunori Nakamura.
Application Number | 20100319321 12/667656 |
Document ID | / |
Family ID | 40226135 |
Filed Date | 2010-12-23 |
United States Patent
Application |
20100319321 |
Kind Code |
A1 |
Kamiya; Shohei ; et
al. |
December 23, 2010 |
Engine Powered Machine
Abstract
An engine powered machine is provided with an economical exhaust
gas purification system capable of avoiding overheating. The engine
powered machine is provided with an exhaust gas purification system
that injects a reducing agent into an exhaust pipe of an engine by
a reducing agent feeder to detoxify nitrogen oxides in exhaust
gases. A cooling fan, the driving or stopping of which is
controlled by a controller, is arranged as a cooling device for a
reducing agent tank in which the reducing agent to be injected by
the reducing agent feeder is stored. When a detected temperature
signal output from a reducing agent temperature detector has become
higher than a cooling initiation temperature stored in a storage
unit, the controller drives the cooling fan to initiate cooling of
the reducing agent tank.
Inventors: |
Kamiya; Shohei;
(Tsuchiura-shi, JP) ; Nakamura; Kazunori;
(Tsuchiura-shi, JP) ; Arai; Yasushi;
(Tsuchiura-shi, JP) |
Correspondence
Address: |
CROWELL & MORING LLP;INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
Hitachi Corporation Machinery Co.,
Ltd.
Bunkyo-ku, Tokyo
JP
|
Family ID: |
40226135 |
Appl. No.: |
12/667656 |
Filed: |
July 2, 2008 |
PCT Filed: |
July 2, 2008 |
PCT NO: |
PCT/JP2008/061997 |
371 Date: |
January 4, 2010 |
Current U.S.
Class: |
60/285 |
Current CPC
Class: |
F01N 2610/11 20130101;
F01N 2610/03 20130101; B01D 2258/012 20130101; F01N 3/208 20130101;
F01N 2610/14 20130101; Y02T 10/12 20130101; B01D 2257/404 20130101;
B01D 53/90 20130101; F01N 2260/022 20130101; Y02T 10/24 20130101;
F01N 2900/1811 20130101; F01P 1/06 20130101; F01N 2610/1406
20130101; F01N 2610/02 20130101; B01D 2251/2067 20130101; B01D
53/9431 20130101 |
Class at
Publication: |
60/285 |
International
Class: |
F01N 9/00 20060101
F01N009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 3, 2007 |
JP |
2007-175466 |
Claims
1. An engine powered machine provided with an NOx removal catalyst
arranged in an exhaust passage of an engine to selectively subject
to reduction treatment nitrogen oxides that flow through the
exhaust passage, a reducing agent tank for storing a reducing
agent, a reducing agent feeder for injecting into the exhaust
passage the reducing agent stored in the reducing agent tank, a
reducing agent temperature detector for detecting a temperature of
the reducing agent stored in the reducing agent tank, a cooling fan
for cooling the reducing agent tank, and a controller for receiving
a detected temperature signal outputted from the reducing agent
temperature detector and controlling drive of the cooling fan,
wherein: the controller has an input port for receiving the
detected temperature signal, a storage unit in which a cooling
initiation temperature for the reducing agent tank is stored, a
computing unit for comparing the detected temperature signal with
the cooling initiation temperature and, when the detected
temperature signal has become equal to or higher than the cooling
initiation temperature, outputting a drive signal for the cooling
fan, and an output port for outputting the drive signal.
2. The engine powered machine according to claim 1, wherein the
reducing agent is a urea water, and the cooling initiation
temperature is +35.degree. C.
3. The engine powered machine according to claim 1, wherein the
reducing agent tank is provided on an outer wall thereof with
cooling fins.
4. The engine powered machine according to claim 1, wherein an
electric motor or hydraulic motor is used as a power source for the
cooling fan.
Description
TECHNICAL FIELD
[0001] This invention relates to a machine equipped with an engine
as a power source (engine powered machine) such as a construction
machine or automotive vehicle, and especially to a temperature
control means for an exhaust gas purification system, which
detoxifies nitrogen oxides in exhaust gases by using an NOx removal
catalyst and a reducing agent added thereto, in an engine powered
machine provided with the exhaust gas purification system.
BACKGROUND ART
[0002] Known exhaust gas purification systems to be mounted on
engine powered machines include one provided with an NOx removal
catalyst arranged in an exhaust pipe and a reducing agent feeder
for injecting a reducing agent, which is stored in a reducing agent
tank, from a side upstream of the arranged location of the NOx
removal catalyst to selectively subject nitrogen oxides in exhaust
gases to reduction treatment with the reducing agent in the
presence of the NOx removal catalyst such that the nitrogen oxides
are decomposed into harmless nitrogen gas and water. Usable as the
reducing agent is a urea water that undergoes hydrolysis in the
exhaust pipe and is changed into ammonia having good reactivity
with nitrogen oxides, an aqueous ammonia solution, gas oil
containing hydrocarbons as principal components, or the like.
[0003] When brought into a supercooled state, such a reducing agent
freezes so that it can no longer be injected into an exhaust pipe.
When brought into an overheated state, on the other hand, its
component(s) vaporize(s) to produce an offensive odor. Further, a
variation in the concentration of the reducing agent due to
freezing or overheating develops an inconvenience such that a
restriction would be placed on start-up of an engine by a signal
from a concentration sensor arranged in the reducing agent tank.
Certain keep-warm measures are, therefore, needed such that the
reducing agent can be maintained within an appropriate temperature
while being stored in the reducing agent tank.
Conventionally-proposed keep-warm measures for a reducing agent
stored in a reducing agent tank include those in which a heat
exchanger is arranged in the reducing agent tank, a cooling
circulation passage equipped with a radiation device is connected
to a circulation passage for an engine cooling medium via three-way
cocks, the three-way cocks are switched toward the cooling medium
circulation passage to guide a cooling medium of a high
temperature, which is flowing through the cooling medium
circulation passage, to the heat exchanger in the reducing agent
tank when the reducing agent has come into a supercooled state, and
the three-way cocks are switched toward the cooling circulation
passage to guide the cooling medium of a low temperature, which is
flowing through the cooling circulation passage, to the heat
exchanger in the reducing agent tank when the reducing agent has
come into an overheated state (see, for example,
JP-A-200583223).
[0004] Further, proposed anti-freezing means for a reducing agent
tank mounted on a construction machine include a technology in
which the reducing agent tank is arranged in an engine compartment,
near a hydraulic pump, in an operator's cab, near a hydraulic oil
tank, or near a hydraulic motor (see, for example,
JP-A-2003-20936).
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
[0005] However, the technology disclosed in JP-A-2005-83223
requires, as cooling means for the reducing agent stored in the
reducing agent tank, the heat exchanger, cooling medium circulation
passage, three-way cocks, radiation device and cooling circulation
passage, and therefore, is accompanied by problems that the exhaust
gas purification system becomes large and the system, and
consequently, the engine powered machine provided with the system
become highly costly.
[0006] On the other hand, the technology disclosed in
JP-A-2003-20936 is advantageous in cost, but involves a problem
that the reducing agent in the reducing agent tank is prone to
overheating depending on the operational status of the engine
powered machine because the reducing agent tank is arranged in a
compartment or cab of a relatively high temperature and is provided
with no cooling means.
[0007] With a view to solving such problems of the conventional
technologies, an object of the present invention is to provide an
engine powered machine provided with an economical exhaust gas
purification system capable of avoiding overheating of a reducing
agent.
Means for Solving the Problem
[0008] To solve the above-described problems, the present invention
has been firstly constituted to be provided with an NOx removal
catalyst arranged in an exhaust passage of an engine to selectively
subject to reduction treatment nitrogen oxides that flow through
the exhaust passage, a reducing agent tank for storing a reducing
agent, a reducing agent feeder for injecting into the exhaust
passage the reducing agent stored in the reducing agent tank, a
reducing agent temperature detector for detecting a temperature of
the reducing agent stored in the reducing agent tank, a cooling fan
for cooling the reducing agent tank, and a controller for receiving
a detected temperature signal outputted from the reducing agent
temperature detector and controlling drive of the cooling fan,
wherein the controller has an input port for receiving the detected
temperature signal, a storage unit in which a cooling initiation
temperature for the reducing agent tank is stored, a computing unit
for comparing the detected temperature signal with the cooling
initiation temperature and, when the detected temperature signal
has become equal to or higher than the cooling initiation
temperature, outputting a drive signal for the cooling fan, and an
output port for outputting the drive signal.
[0009] According to such a constitution, when the detected
temperature signal outputted from the reducing agent temperature
detector has become equal to or higher than the cooling initiation
temperature stored in the storage unit, the computing unit of the
controller outputs the drive signal for the cooling fan to drive
the cooling fan. It is, therefore, possible to avoid overheating of
the reducing agent stored in the reducing agent tank, and
consequently, production of an offensive odor. Further, this
constitution can be economically put into practice because it is
only necessary to arrange the cooling fan at a predetermined
location as an anti-overheating means for the reducing agent.
[0010] The present invention is secondly constituted such that in
the engine powered machine of the above-described first
constitution, the reducing agent is a urea water, and the cooling
initiation temperature is +35.degree. C.
[0011] Exhaust gas purification systems that make use of a urea
water are most widely employed as exhaust gas purification systems
for diesel engines and gasoline engines, and moreover, have been
established technically. The use of such an exhaust gas
purification system can, therefore, realize stable purification of
exhaust gases. As a urea water vaporizes at about +40.degree. C.
and produces an ammonia odor, the production of an ammonia odor can
be avoided by initiating the drive of the cooling fan at
+35.degree. C. which is lower than the vaporization temperature of
the urea water.
[0012] The present invention is thirdly constituted such that in
the engine powered machine of the above-described first
constitution, the reducing agent tank is provided on an outer wall
thereof with cooling fins.
[0013] The arrangement of the cooling fins on the outer wall of the
reducing agent tank can improve the efficiency of release of heat
from the reducing agent tank, and therefore, the cooling effect for
the reducing agent tank by the cooling fan can be enhanced
further.
[0014] The present invention is fourthly constituted such that in
the engine powered machine of the above-described first
constitution, an electric motor or hydraulic motor is used as a
power source for the cooling fan.
[0015] The use of an electric motor as a power source for the
cooling fan makes it possible to cool the reducing agent tank by
simply arranging the cooling fan and installing necessary wiring,
thereby making it possible to put an exhaust gas purification
system, which is provided with a cooling apparatus for the reducing
agent tank, into practice at low cost. On the other hand, the use
of a hydraulic motor as a power source for the cooling fan makes it
possible to achieve effective utilization of power in an engine
powered machine of the hydraulic drive type, such as a hydraulic
excavator, that uses pressure oil as a power source for various
components in the machine.
Advantageous Effects of the Invention
[0016] The engine powered machine according to the present
invention is provided with the cooling fan for the reducing agent
tank and, when the detected temperature signal outputted from the
reducing agent temperature detector has become equal to or higher
than the cooling initiation temperature stored in the storage unit,
the cooling fan is driven based on the drive signal for the cooling
fan as outputted from the computing unit of the controller. It is,
therefore, possible to avoid overheating of the reducing agent
stored in the reducing agent tank, and consequently, production of
an offensive odor. Further, the engine powered machine according to
the present invention can be economically put into practice,
because it is only necessary to arrange the cooling fan as an
anti-overheating means for the reducing agent.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a constitution diagram of an engine powered
machine according to an embodiment.
[0018] FIG. 2 is a block diagram showing the constitution of a
controller in the embodiment.
[0019] FIG. 3 is a cross-sectional view of a reducing agent tank in
the embodiment.
[0020] FIG. 4 is a table showing operation temperatures of a
reducing agent feeder, cooling fan and on/off device in the
embodiment.
BEST MODES FOR CARRYING OUT THE INVENTION
[0021] One embodiment of the engine powered machine according to
the present invention will hereinafter be described based on FIG. 1
to FIG. 4, in which FIG. 1 is a constitution diagram of the engine
powered machine according to this embodiment, FIG. 2 is a block
diagram showing the constitution of a controller in this
embodiment, FIG. 3 is a cross-sectional view of a reducing agent
tank in this embodiment, and FIG. 4 is a table showing operation
temperatures of a reducing agent feeder, cooling fan and on/off
device in this embodiment.
[0022] As depicted in FIG. 1, the engine powered machine of this
embodiment is provided with an engine 1 as a power source for
individual components of the machine, an NOx removal catalyst 3
arranged in an exhaust pipe (exhaust passage) 2 of the engine 1, a
reducing agent feeder 4 for injecting an NOx reducing agent into
the exhaust pipe 2 on a side upstream of the arranged location of
the NOx removal catalyst 3, a reducing agent tank 5 for storing the
reducing agent to be injected by the reducing agent feeder 4, a
reducing agent temperature detector 6 for detecting a temperature
of the reducing agent stored in the reducing agent tank 5, a
cooling fan 7 for the reducing agent tank 5, a cooling medium flow
passage 8 for guiding a portion of an engine cooling medium to the
reducing agent tank 5, a reducing agent heater 10 for heating the
reducing agent, which is stored in the reducing agent tank 5, with
heat of the engine cooling medium flowing through the cooling
medium flow passage 8, an on/off device 11 for opening/closing the
cooling medium flow passage 8, and a controller 12 for receiving a
detected temperature signal a outputted from the reducing agent
temperature detector 6 and outputting drive signals b, c, d for the
reducing agent feeder 4, cooling fan 7 and on/off device 11.
[0023] As shown in FIG. 2, the controller 12 is comprised of an
input port 12a, a storage unit 12b, a computing unit 12c, and an
output port 12d. The input port 12a receives the detected
temperature signal a. In the storage unit 12b, a cooling initiation
temperature for the reducing agent tank 5 and an injection
initiation temperature for the reducing agent feeder 4 are stored.
The computing unit 12c compares the detected temperature signal a
with the cooling initiation temperature and, when the detected
temperature signal a has become equal to or higher than the cooling
initiation temperature, outputs the drive signal c for the cooling
fan 7 and the drive signal d for the on/off device 11. The
computing unit 12c also compares the detected temperature signal a
with the injection initiation temperature and, when the detected
temperature signal a has become equal to or higher than the
injection initiation temperature, outputs the drive signal b for
the reducing agent feeder 4. The output port 12d outputs the drive
signals b, c, d. The cooling initiation temperature for the
reducing agent tank 5 is set at a temperature slightly lower than
the vaporization temperature of the reducing agent, for example, at
a temperature slightly lower than +40.degree. C. at which ammonia
is produced, for example, +35.degree. C. when a urea water is used
as the reducing agent. On the other hand, the injection initiation
temperature for the reducing agent feeder 4 is set at a temperature
slightly higher than the freezing temperature of the reducing
agent, for example, at a temperature higher than -11.degree. C. at
which the urea water freezes, for example, 0.degree. C. when the
urea water is used as the reducing agent.
[0024] The NOx removal catalyst 3, reducing agent feeder 4 and
reducing agent tank 5 make up the exhaust gas purification system
described in the above-cited Patent Document 1. The reducing agent
stored in the reducing agent tank 5, such as a urea water, an
aqueous ammonia solution or gas oil containing hydrocarbons as
principal components, is injected in the form of a mist into the
exhaust pipe 2 by the reducing agent feeder 4, and nitrogen oxides
in exhaust gases are selectively subjected to reduction treatment
with the reducing agent in the presence of the NOx catalyst 3 to
decompose the nitrogen oxides into harmless nitrogen gas and water.
When a urea water is used as the reducing agent, the urea water
injected into the exhaust pipe 2 is subjected to hydrolysis with
the heat of exhaust gases to produce ammonia having good reactivity
with nitrogen oxides, and by the thus-produced ammonia, nitrogen
oxides are selectively subjected to reduction treatment. Depending
on the exhaust rate and exhaust temperature, the injection rate of
the reducing agent into the exhaust pipe 2 is controlled to such a
range that the nitrogen oxides in exhaust gases can be
substantially removed while avoiding leaving the reducing agent as
a surplus. The reducing agent feeder 4 is comprised of a nozzle 4a
and an injection device 4b for injecting the reducing agent, which
is stored in the reducing agent tank 5, in the form of a mist
through the nozzle 4a, and the driving or stopping of the injection
device is controlled by the drive signal b outputted from the
controller 12.
[0025] The reducing agent tank 5 is formed of plastics, stainless
steel plates or the like, and at necessary locations on outer
walls, cooling fins 5a are arranged as illustrated in FIG. 3. Their
arrangement has made it possible to reduce the size of the cooling
fan 7 and also to achieve efficient cooling by blowing air. The
reducing agent tank 5 can be arranged at a desired location on the
engine powered machine. It is, however, desired to arrange the
reducing agent tank 5 at a location from which an offensive odor is
not allowed to penetrate into the operator's cab even if the
offensive odor is produced, for example, within a utility
compartment in the case of a construction machine or under a body
in the case of a truck. When the reducing agent tank 5 is arranged
within a compartment such as a utility compartment, formation of a
vent hole on a downstream side of air-blowing is particularly
desired to enhance the efficiency of cooling by the cooling fan
7.
[0026] The cooling fan 7 is comprised of rotating blades 7a and a
motor 7b for rotationally driving the rotating blades 7a, and the
driving or stopping of the motor 7b is controlled by the drive
signal c outputted from the controller 12. As the motor 7b, an
electric motor can be used, or a hydraulic motor can also be used.
The use of an electric motor as the motor 7b for the cooling fan 7
makes it possible to cool the reducing agent tank 5 by simply
arranging the cooling fan 7 and installing necessary wiring,
thereby making it possible to put an exhaust gas purification
system, which is provided with a cooling apparatus for the reducing
agent tank, into practice at low cost. On the other hand, the use
of a hydraulic motor as the motor 7b for the cooling fan 7 makes it
possible to achieve effective utilization of power in an engine
powered machine, such as a hydraulic excavator, that uses pressure
oil as a power source for various components in the machine.
[0027] The on/off device 11 is comprised of a valve element 11a for
opening or closing the cooling medium flow passage 8 and an
actuator 11b, such as a solenoid, for driving the valve element,
and the switched position of the valve element 11a is controlled by
the drive signal d outputted from the controller 12.
[0028] Using FIG. 4, a description will hereinafter be made of
operation of the reducing agent feeder 4, cooling fan 7 and on/off
device 11. It is to be noted that FIG. 4 illustrates by way of
example a case in which a urea water was used as a reducing agent,
-11.degree. C. is the freezing temperature of the urea water,
0.degree. C. is an injection initiation temperature for the
reducing agent feeder 4, and +35.degree. C. is a cooling initiation
temperature for the reducing agent tank 5. In FIG. 4, the sign
"OFF" shown in the column for the reducing agent feeder 4 indicates
that the injection of the reducing agent by the reducing agent
feeder 4 is in a stopped state, while the sign "ON" indicates that
the injection of the reducing agent by the reducing agent feeder 4
is under execution. The sign "OFF" shown in the column for the
cooling fan 7 indicates that the cooling fan 7 is in a stopped
state, while the sign "ON" indicates that the cooling fan 7 is in a
driven state. Further, the sign "OFF" shown in the column for the
on/off device 11 indicates that the feeding of the engine cooling
medium to the reducing agent heater 10 is in a stopped state, while
the sign "ON" indicates that the engine cooling medium is in a
state of being fed to the reducing agent heater 10.
[0029] As is evident from this table, when the temperature of the
reducing agent in the reducing agent tank 5 is equal to or higher
than the injection initiation temperature (0.degree. C.), the
reducing agent feeder 4 receives a drive signal b outputted from
the controller 12 and is driven to perform the injection of the
reducing agent into the exhaust pipe 2. As a consequence, it is
possible to conduct the purification of engine exhaust gases
flowing through the exhaust pipe 2. When the temperature of the
reducing agent in the reducing agent tank 5 is lower than the
injection initiation temperature (0.degree. C.), on the other hand,
the reducing agent feeder 4 receives a drive signal b outputted
from the controller 12 and its driving is stopped. As a
consequence, it is possible to avoid clogging of an unillustrated
injection nozzle with pieces of ice or the like.
[0030] When the temperature of the reducing agent in the reducing
agent tank 5 has arisen to the cooling initiation temperature
(+35.degree. C.), the cooling fan 7 receives a drive signal c
outputted from the controller 12 and its driving is initiated to
cool the reducing agent stored in the reducing agent tank 5. On the
other hand, the operation of the on/off device 11 is opposite to
that of the cooling fan 7 and, when the temperature of the reducing
agent in the reducing agent tank 5 has arisen to the cooling
initiation temperature (+35.degree. C.), the on/off device 11
receives a drive signal d outputted from the controller 12, and the
feeding of the engine cooling medium to the reducing agent heater
10 is stopped to permit efficient cooling of the reducing agent by
the cooling fan 7. By controlling the driving of the cooling fan 7
and on/off device 11 as described above, the temperature of the
reducing agent in the reducing agent tank 5 can be maintained
within an appropriate temperature range.
[0031] When the detected temperature signal a outputted from the
reducing agent temperature detector 6 has become equal to or higher
than the cooling initiation temperature stored in the storage unit
12b in the engine powered machine according to this embodiment, the
computing unit 12c of the controller 12 outputs the drive signal c
for the cooling fan 7 to rotationally drive the cooling fan 7. It
is, therefore, possible to avoid overheating of the reducing agent
stored in the reducing agent tank 5, and consequently, production
of an offensive odor. Further, the engine powered machine can be
economically put into practice because it is only necessary to
arrange the cooling fan 7 as an anti-overheating means for the
reducing agent.
[0032] The engine powered machine according to this embodiment is
provided with the system for heating the reducing agent stored in
the reducing agent tank 5, specifically, the cooling medium flow
passage 8 for guiding a portion of an engine cooling medium to the
reducing agent tank 5, a cooling medium temperature detector 9 for
detecting the temperature of the engine cooling medium flowing
through the cooling medium flow passage 8, the reducing agent
heater 10 for heating the reducing agent, which is stored in the
reducing agent tank 5, with the heat of the engine cooling medium
flowing through the cooling medium flow passage 8, and the on/off
device 11 for opening/closing the cooling medium flow passage 8. It
is, however, to be noted that these devices may be omitted in an
engine powered machine to be used under an environment that the
reducing agent does not freeze.
[0033] In this embodiment, the reducing agent tank 5 having the
cooling fins 5a is used. However, a reducing agent tank 5 which
does not have the cooling fins 5a can also be used when the cooling
capacity of the cooling fan 7 is sufficiently large.
LEGEND
[0034] 1 Engine [0035] 2 Exhaust pipe [0036] 3 NOx removal catalyst
[0037] 4 Reducing agent feeder [0038] 5 Reducing agent tank [0039]
6 Reducing agent temperature detector [0040] 7 Cooling fan [0041]
7a Rotating blades [0042] 7b Motor [0043] 8 Engine cooling medium
flow passage [0044] 9 Cooling medium temperature detector [0045] 10
Reducing agent heater [0046] 11 On/off device [0047] 12
Controller
* * * * *