U.S. patent application number 12/226611 was filed with the patent office on 2009-09-17 for exhaust gas purification apparatus for an internal combustion engine.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Takashi Ogawa.
Application Number | 20090229257 12/226611 |
Document ID | / |
Family ID | 38219023 |
Filed Date | 2009-09-17 |
United States Patent
Application |
20090229257 |
Kind Code |
A1 |
Ogawa; Takashi |
September 17, 2009 |
Exhaust Gas Purification Apparatus for an Internal Combustion
Engine
Abstract
In an exhaust gas purification apparatus for an internal
combustion engine, there is provided a technique that can perform
the addition of a reducing agent to an exhaust gas in a more
appropriate manner; in an exhaust gas purification apparatus for an
internal combustion engine having a fuel addition valve that adds
fuel to an exhaust gas upstream of a filter arranged in an exhaust
passage of the internal combustion engine, an internal pressure in
a cylinder of the internal combustion engine upon opening of an
exhaust valve for the cylinder is detected, and a flow speed or
temperature of the exhaust gas passing a fuel addition position of
the fuel addition valve in the exhaust passage is estimated based
on the detected cylinder internal pressure; an amount of addition
of fuel is adjusted based on the estimated flow speed or
temperature of the exhaust gas.
Inventors: |
Ogawa; Takashi; (Susono-shi,
JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
|
Family ID: |
38219023 |
Appl. No.: |
12/226611 |
Filed: |
April 26, 2007 |
PCT Filed: |
April 26, 2007 |
PCT NO: |
PCT/JP2007/059421 |
371 Date: |
October 23, 2008 |
Current U.S.
Class: |
60/287 ;
60/310 |
Current CPC
Class: |
F01N 3/0821 20130101;
Y02T 10/40 20130101; F01N 3/0842 20130101; F02D 41/1445 20130101;
F01N 3/0253 20130101; F01N 3/0871 20130101; F01N 9/00 20130101;
F01N 9/002 20130101; F02D 35/023 20130101; F01N 3/36 20130101; Y02T
10/47 20130101; F02D 41/1447 20130101 |
Class at
Publication: |
60/287 ;
60/310 |
International
Class: |
F01N 9/00 20060101
F01N009/00; F01N 3/04 20060101 F01N003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 26, 2006 |
JP |
2006-121613 |
Claims
1. An exhaust gas purification apparatus for an internal combustion
engine having a reducing agent addition unit that adds a reducing
agent to an exhaust gas upstream of an exhaust gas purification
unit arranged in an exhaust passage of said internal combustion
engine, said apparatus comprising: a cylinder internal pressure
detection unit that detects an internal pressure in a cylinder of
said internal combustion engine when an exhaust valve for said
cylinder is opened; an estimation unit that estimates a flow speed
or temperature of said exhaust gas passing a reducing agent
addition position of said reducing agent addition unit in said
exhaust passage based on said cylinder internal pressure detected
by said cylinder internal pressure detection unit; and an addition
control unit that adjusts an amount of addition of said reducing
agent based on the flow speed or temperature of said exhaust gas
estimated by said estimation unit.
2. The exhaust gas purification apparatus for an internal
combustion engine as set forth in claim 1, wherein said estimation
unit estimates that the higher said cylinder internal pressure
detected by said cylinder internal pressure detection unit, the
higher the flow speed or temperature of said exhaust gas becomes;
and said addition control unit increases the amount of addition of
said reducing agent in accordance with the higher flow speed or
temperature of said exhaust gas estimated by said estimation
unit.
3. The exhaust gas purification apparatus for an internal
combustion engine as set forth in claim 1, wherein said estimation
unit estimates timing at which the flow speed of said exhaust gas
discharged per one exhaust stroke period becomes maximum; and said
addition control unit adjusts the timing of addition of said
reducing agent based on said timing estimated by said estimation
unit.
4. The exhaust gas purification apparatus for an internal
combustion engine as set forth in claim 2, wherein said estimation
unit estimates timing at which the flow speed of said exhaust gas
discharged per one exhaust stroke period becomes maximum; and said
addition control unit adjusts the timing of addition of said
reducing agent based on said timing estimated by said estimation
unit.
Description
TECHNICAL FIELD
[0001] The present invention relates to an exhaust gas purification
apparatus for an internal combustion engine that serves to add a
reducing agent to an exhaust gas.
BACKGROUND ARTS
[0002] Japanese patent application laid-open No. 2004-143988
discloses, as a technique to add a reducing agent to an exhaust
gas, one in which an exhaust gas temperature sensor is arranged
between an oxidation catalyst disposed in an exhaust passage and a
particulate filter disposed immediately downstream of the oxidation
catalyst, so that the reducing agent is added to the exhaust gas
based on the temperature of the exhaust gas detected by the exhaust
gas temperature sensor. Also, Japanese patent application laid-open
No. 2004-44515 discloses a technique in which when temperature
raising control is performed by controlling the addition of a
reducing agent by a reducing agent addition unit based on the
temperature of an exhaust gas detected by a temperature detecting
unit arranged downstream of two purification units, a flow rate Q
of the exhaust gas passing through two purification units is
estimated or detected, and the temperature raising control on the
purification units is not started when the above-mentioned flow
rate Q is equal to or less than a predetermined amount CQ at the
time of starting the temperature raising control. In addition,
Japanese patent application laid-open No. 2005-120938 discloses a
technique in which when the processing of purifying a NOx catalyst
is carried out by releasing and reducing NOx held in the NOx
catalyst, light oil is injected into an exhaust gas by an addition
valve so that the light oil is supplied to the NOx catalyst
together with the exhaust gas, and after the droplet-like light oil
adheres to the entire area of the NOx catalyst, the flow rate of
the exhaust gas is decreased.
DISCLOSURE OF THE INVENTION
[0003] Here, note that the flow rate or speed and the temperature
of the exhaust gas passing the position of addition of the reducing
agent in the exhaust passage might fluctuate to a great extent in
each cylinder or cycle in accordance with a change in the operating
state of the internal combustion engine.
[0004] However, there occurs a response delay by the time the
change in the exhaust gas temperature is reflected on measurements
of the exhaust gas temperature sensor. so there will be a
possibility that the exhaust gas temperature sensor can not catch a
steep temperature variation in each cylinder or cycle as stated
above. Accordingly, in the above-mentioned conventional technique,
the reducing agent can not occasionally be added in an appropriate
manner.
[0005] The object of the present invention is to provide a
technique which is capable of performing the addition of a reducing
agent in a more appropriate manner in an exhaust gas purification
apparatus for an internal combustion engine including a reducing
agent addition unit for adding the reducing agent to an exhaust gas
flowing in an exhaust passage of the internal combustion
engine.
[0006] In the present invention, the following construction is
adopted. That is, the present invention resides in an exhaust gas
purification apparatus for an internal combustion engine having a
reducing agent addition unit that adds a reducing agent to an
exhaust gas upstream of an exhaust gas purification unit arranged
in an exhaust passage of said internal combustion engine,
[0007] said exhaust gas purification apparatus being characterized
by comprising:
[0008] a cylinder internal pressure detection unit that detects an
internal pressure in a cylinder of said internal combustion engine
when an exhaust valve for the cylinder is opened;
[0009] an estimation unit that estimates a flow speed or
temperature of the exhaust gas passing a reducing agent addition
position of said reducing agent addition unit in said exhaust
passage based on the cylinder internal pressure detected by said
cylinder internal pressure detection unit; and
[0010] an addition control unit that adjusts an amount of addition
of the reducing agent based on the flow speed or temperature of the
exhaust gas estimated by said estimation unit.
[0011] The flow speed and the temperature of the exhaust gas
passing the reducing agent addition position might change or
fluctuate to a great extent in each cylinder or cycle of the
internal combustion engine. Thus, it has been difficult to detect a
steep change as stated above immediately with the use of a sensor
having a low response as an exhaust gas temperature sensor.
[0012] In contrast to this, the flow speed and the temperature of
the exhaust gas discharged on an exhaust stroke of the cylinder
correlate to the cylinder internal pressure (the pressure in the
cylinder) when the exhaust valve is opened, so the flow speed and
the temperature of the exhaust gas can be specified (estimated)
immediately by measuring the cylinder internal pressure upon
opening of the exhaust valve for the cylinder.
[0013] Accordingly, the exhaust gas purification apparatus for an
internal combustion engine of the present invention estimates the
flow speed or the temperature of the exhaust gas passing the
reducing agent addition position based on the cylinder internal
pressure upon opening of the exhaust valve, and adjusts the amount
of addition of the reducing agent based on the estimated flow speed
or temperature of the exhaust gas.
[0014] According to this, even when the flow speed and the
temperature of the exhaust gas passing the reducing agent addition
position differ to a great extent among individual cylinders or
individual cycles, it is possible to immediately estimate the flow
speed or the temperature of the exhaust gas at the time when the
exhaust gas discharged from each cylinder passes the reducing agent
addition position, or the flow speed or the temperature of the
exhaust gas at the time when the exhaust gas discharged from each
cylinder on an exhaust stroke of each cycle passes the reducing
agent addition position. When the amount of addition of the
reducing agent is adjusted in accordance with the flow speed or the
temperature of the exhaust gas estimated in this manner, the amount
of addition of the reducing agent becomes appropriate for the flow
speed or the temperature of the exhaust gas, so the addition of the
reducing agent can be performed in a more appropriate manner.
[0015] Here, note that the flow speed and the temperature of the
exhaust gas tend to become higher in accordance with the increasing
cylinder internal pressure upon opening of the exhaust valve, so
the estimation unit of the present invention can estimate that the
higher the cylinder internal pressure detected by the cylinder
internal pressure detection unit, the higher the flow speed or
temperature of the exhaust gas passing the reducing agent addition
position becomes. As a consequence of this, the addition control
unit may increase the amount of addition of the reducing agent in
accordance with the higher flow speed or temperature of the exhaust
gas estimated by the estimation unit.
[0016] For example, when the amount of addition of the reducing
agent is increased in accordance with the increasing flow speed of
the exhaust gas estimated by the estimation unit, the amount of the
reducing agent with respect to the flow rate or amount of the
exhaust gas can be maintained to a desired ratio. Accordingly, it
becomes easy to make the air-fuel ratio of the exhaust gas converge
into a target air-fuel ratio by adding the reducing agent to the
exhaust gas.
[0017] In addition, when the amount of addition of the reducing
agent is increased in accordance with the higher temperature of the
exhaust gas estimated by the estimation unit, it is possible to add
a maximum amount of reducing agent that can be vaporized with
respect to the temperature of the exhaust gas. Thus, it becomes
easy to raise the temperature of the exhaust gas purification unit
at an early time by using the oxidation heat of the reducing
agent.
[0018] Here, note that the estimation unit may estimate timing at
which the flow speed of the exhaust gas discharged per one exhaust
stroke period becomes maximum, and the addition control unit may
adjust the timing of addition of the reducing agent based on the
timing estimated by the estimation unit. As a result, the timing of
the reducing agent addition becomes appropriate for the flow speed
or temperature of the exhaust gas, thus making it possible to
perform the addition of the reducing agent in a more appropriate
manner.
[0019] The above and other objects, features and advantages of the
present invention will become more readily apparent to those
skilled in the art from the following detailed description of
preferred embodiments of the present invention taken in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 illustrates the schematic construction of an internal
combustion engine with an intake system and an exhaust system to
which an exhaust gas purification apparatus for an internal
combustion engine according to an embodiment of the present
invention is applied.
[0021] FIG. 2 is a flow chart illustrating a control routine in
fuel addition control.
[0022] FIG. 3 is a view showing cylinder internal pressure, the
flow speed and the temperature of an exhaust gas, and the state of
fuel addition associated with the fuel addition control.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0023] Hereinafter, reference will be made to a specific embodiment
of the present invention.
First Embodiment
[0024] FIG. 1 illustrates the schematic construction of an internal
combustion engine with its intake system and exhaust system to
which an exhaust gas purification apparatus according to a first
embodiment of the present invention is applied.
[0025] The internal combustion engine 1 as shown in FIG. 1 is a
water-cooled four-stroke cycle diesel engine having four cylinders
2. A piston 3 is slidably fitted in each cylinder 2 of the internal
combustion engine 1.
[0026] An intake port 4 and an exhaust port 5 are connected with a
combustion chamber defined in each cylinder 2 at an upper portion
thereof. The intake port 4 and the exhaust port 5 have their
opening portions into the combustion chamber adapted to be opened
and closed by an intake valve 6 and an exhaust valve 7,
respectively. The intake port 4 and the exhaust port 5 are
connected with an intake passage 8 and an exhaust passage 9,
respectively.
[0027] In addition, on each cylinder 2, there is mounted a fuel
injection valve 10 at a location right above the cylinder 2 for
directly injecting fuel into the corresponding cylinder 2. Also, on
each cylinder 2 at an ascending location thereof, there is mounted
a cylinder internal pressure sensor 11 for detecting the internal
pressure of the corresponding cylinder 2.
[0028] An exhaust passage 9 is connected at its downstream end with
an unillustrated muffler. A filter 12 for purifying an exhaust gas
discharged from each cylinder 2 of the internal combustion engine 1
is arranged in the exhaust passage 9. The filter 12 is a
particulate filter that serves to collect PM (particulate matter)
such as soot, etc., discharged from the internal combustion engine
1. An occlusion reduction type NOx catalyst (hereinafter referred
to as a NOx catalyst) is supported by the filter 12. In addition,
the filter 12 may be one having a NOx catalyst and a particulate
filter arranged in series with each other, or another one having a
plurality of NOx catalysts and particulate filters alternately
arranged one over another. The filter 12 corresponds to an exhaust
gas cleaning or purification unit of the present invention.
[0029] Also, a fuel addition valve 13 for supplying a reducing
agent in the form of fuel to the exhaust gas passing through the
exhaust passage 9 is mounted on the exhaust passage 9 at an
upstream side of the filter 12. The fuel addition valve 13
corresponds to a reducing agent addition unit of the present
invention.
[0030] An electronic control unit (ECU) 14 for controlling the
internal combustion engine 1 is provided in conjunction with the
internal combustion engine 1 as constructed in the above manner.
The ECU 14 comprises a control computer comprising a CPU, a ROM, a
RAM, a backup RAM, etc.
[0031] The ECU 14 is connected to the cylinder internal pressure
sensors 11 through electrical wiring, so that output signals of the
individual cylinder internal pressure sensors 11 are input to the
ECU 14. Also, the ECU 14 is connected to the fuel injection valves
10 and the fuel addition valve 13 through electrical wiring, so
that the opening and closing timing of the fuel injection valves 10
and the fuel addition valve 13 can be controlled by the ECU 14.
[0032] In a basic routine to be executed at regular intervals, the
ECU 14 executes, for example, inputting of output signals from a
variety of kinds of sensors as well as arithmetic calculations of
the engine rotational speed, the amount of fuel to be supplied, and
the fuel supply timing of fuel to be supplied, etc. The various
kinds of signals input to the ECU 14 and various control values
obtained by the calculations of the ECU 14 in the basic routine are
temporarily stored in the RAM of the ECU 14.
[0033] Further, in such interrupt processing that is triggered by
input of signals from the variety of sensors and switches, the
elapse of a prescribed time, or input of a pulse signal from a
crank position sensor, etc., the ECU 14 reads out various control
values from the RAM, and controls the fuel injection valves 10 and
the fuel addition valve 13 in accordance with the control values
thus read out.
[0034] The ECU 14 executes fuel addition control such as NOx
reduction processing, SOx poisoning recovery processing, PM
oxidation removal processing, etc., so as to add fuel to the
exhaust gas flowing form the fuel addition valve 13 into the filter
12 in accordance with an application program stored in the ROM.
[0035] Here, note that the NOx reduction processing is the
processing that adds fuel from the fuel addition valve 13 to the
exhaust gas to enrich the air-fuel ratio of the exhaust gas flowing
into the filter 12, thereby releasing and reducing the NOx occluded
in the NOx catalyst of the filter 12.
[0036] The SOx poisoning recovery processing is the processing that
adds fuel from the fuel addition valve 13 to the exhaust gas to
oxidize the added fuel in the NOx catalyst of the filter 12,
whereby the temperature of the filter 12 is raised to 600 degrees
C.-800 degrees C. due to the heat accompanying the oxidation
reaction, and at the same time, the air-fuel ratio of the exhaust
gas flowing into the filter 12 is enriched, thereby releasing and
reducing the SOx occluded in the NOx catalyst of the filter 12.
[0037] The PM oxidation removal processing is the processing that
adds fuel from the fuel addition valve 13 to the exhaust gas to
oxidize the added fuel in the NOx catalyst of the filter 12,
whereby the temperature of the filter 12 is raised by the heat
accompanying the oxidation reaction to oxidize and remove the PM
collected in the filter 12.
[0038] Here, note that the flow speed and the temperature of the
exhaust gas passing the position of addition of fuel from the fuel
addition valve 13 in the exhaust passage 9 change to a great extent
in each cylinder 2 of the internal combustion engine 1 in
accordance with a change in the operating state of the internal
combustion engine 1. In the fuel addition control, it is desired to
add fuel in an amount and at timing of addition suitable for the
flow speed and the temperature of the exhaust gas passing the
position of addition of fuel from the fuel addition valve 13 in the
exhaust passage 9.
[0039] Accordingly, in this embodiment, the flow speed and the
temperature of the exhaust gas passing the position of addition of
fuel is estimated based on the cylinder internal pressure, and the
number or frequency of fuel addition and the timing of fuel
addition from the fuel addition valve 13 are adjusted based on the
flow speed and the temperature of the exhaust gas thus
estimated.
[0040] According to this, it is possible to set the frequency and
timing of addition of fuel suitable or appropriate for the
estimated flow speed and temperature of the exhaust gas passing the
position of addition of fuel, so the addition of fuel can be
carried out in a more appropriate manner.
[0041] In the NOx reduction processing and the SOx poisoning
recovery processing, the amount of fuel with respect to the flow
rate of the exhaust gas can be maintained at a desired ratio. As a
result, the air-fuel ratio of the exhaust gas can be lowered with a
high degree of precision, whereby the air-fuel ratio of the exhaust
gas is converged into a target air-fuel ratio in an easy manner.
Thus, it is possible to suppress the air-fuel ratio of the exhaust
gas from shifting to a lean side or a rich side with respect to the
target air-fuel ratio, for example, even at the time of transient
operation
[0042] In addition, in the SOx poisoning recovery processing and
the PM oxidation removal processing, the temperature of the filter
12 can be raised to a target temperature by adding a maximum amount
of fuel that can be vaporized. Accordingly, it is possible to
facilitate to raise the temperature of the filter 12 at an early
time by using the oxidation heat of fuel, and it is also possible
to suppress insufficient vaporization of fuel and hence prevention
of a temperature rise due to the addition of an excessively large
amount of fuel, as well as the occurrence of filter clogging
resulting from that fuel in a droplet state reaches the filter 12.
In addition, it is further possible to suppress an insufficient
temperature rise of the filter 12 resulting from the addition of an
excessively small amount of fuel.
[0043] Here, reference will be made to a control routine for
performing the fuel addition control according to this embodiment
based on a flow chart shown in FIG. 2. Note that this routine is
stored in the ECU 14 beforehand, and in this embodiment, the
routine is executed in a periodic manner when the addition of fuel
is executed at the time either of the cylinders 2 of the internal
combustion engine 1 undergoes an exhaust stroke.
[0044] When a request for executing fuel addition control is made
to start the processing of this routine, first in step S101, the
ECU 14 detects the internal pressure of one predetermined cylinder
2, for which a relevant exhaust valve 7 is opened, by means of a
cylinder internal pressure sensor 11 at the time of opening of the
relevant exhaust valve 7 for the one predetermined cylinder 2,
which undergoes an exhaust stroke in the current fuel addition
control of the internal combustion engine 1. That is, as shown in
FIG. 3(a), the cylinder internal pressure is detected at an instant
immediately after the start of the exhaust stroke of the cylinder 2
for which the relevant exhaust valve 7 is opened. Here, note that
the ECU 14 executing this step corresponds to a cylinder internal
pressure detection unit of the present invention. Then, the control
flow shifts to step S102.
[0045] In step S102, based on the internal pressure of a cylinder 2
for which the relevant exhaust valve 7 is opened and which is
detected by the relevant cylinder internal pressure sensor 11, the
ECU 14 estimates the flow speed and the temperature of the exhaust
gas passing the position of addition of fuel from the fuel addition
valve 13 in the exhaust passage 9 for the period of the exhaust
stroke of the cylinder 2 for which the relevant exhaust valve 7 is
opened. That is, as shown in FIG. 3(b), the flow speed of the
exhaust gas, which changes in a convex curve, and the temperature
of the exhaust gas, which changes in a straight line, are estimated
in the period of the exhaust stroke of the cylinder 2 for which the
relevant exhaust valve 7 is opened. Here, note that the ECU 14
executing this step corresponds to an estimation unit of the
present invention.
[0046] The estimated flow speed and temperature of the exhaust gas
is derived from a cylinder internal pressure map and the result of
the last fuel addition control, and the higher the cylinder
internal pressure, the greater the flow speed of the exhaust gas
becomes, and the higher the temperature of the exhaust gas becomes.
Specifically, the flow speed of the exhaust gas is estimated in
such a manner that a basic convex curve-shaped variation or
fluctuation of the flow speed in the period of the exhaust stroke
of one of the cylinders 2 is derived from the cylinder internal
pressure map, and a starting point of the current flow speed is
connected with a termination point of the flow speed estimated in
the last fuel addition control. Also, the temperature of the
exhaust gas is estimated in such a manner that a first temperature
of the exhaust gas at a time point when the flow speed of the
exhaust gas in the current fuel addition control becomes maximum is
derived from the cylinder internal pressure map, and the
temperature of the exhaust gas changes linearly on a straight line
connecting between the first temperature and a second temperature
of the exhaust gas at a time point when the flow speed of the
exhaust gas in the last fuel addition control became maximum.
Thereafter, the control flow shifts to step S103.
[0047] In step S103, the ECU 14 calculates, based on the estimated
flow speed and temperature of the exhaust gas, the frequency of
addition of fuel from the fuel addition valve 13 for the period of
the exhaust stroke of the cylinder 2 for which the relevant exhaust
valve 7 is opened. The frequency of fuel addition thus calculated
is derived from a map, which has the flow speed and the temperature
of the exhaust gas as parameters, so as to provide an optimal
amount of fuel addition, and the higher the flow speed and the
temperature of the exhaust gas, the greater the frequency of fuel
addition becomes, as shown in FIG. 3(c). Here, note that the ECU 14
executing this step corresponds to an addition control unit of the
present invention. Then, the control flow shifts to step S104.
[0048] In step S104, the ECU 14 adds fuel from the fuel addition
valve 13 to the exhaust gas at the frequency of fuel addition
calculated in step S103. Here, note that the timing of fuel
addition is set to the time of starting the addition of fuel
immediately after the flow speed of the exhaust gas changing in a
convex curved manner, which was estimated in step S102, becomes
maximum, as shown in FIG. 3(b) and (c), in such a manner that the
fuel to be added reaches the filter 12 at an optimal time while
being entrained in the exhaust gas. Thereafter, the processing of
this routine is once terminated.
[0049] In fuel addition control thereafter, the processing of this
routine is performed upon each execution of such control.
[0050] By executing the above-mentioned routine in this manner, it
is possible to set the frequency and timing of addition of fuel in
an optimal manner in accordance with the estimated flow speed and
temperature of the exhaust gas passing the position of addition of
fuel in fuel addition control, so the addition of fuel into the
exhaust gas can be carried out in a more appropriate manner.
[0051] Here, note that in the above-mentioned embodiment, an
optimal amount of fuel is added by increasing and decreasing the
frequency of addition of fuel, but the present invention is not
limited to this, and an optimal amount of fuel may be added by
changing the duration of opening of the fuel addition valve 13
thereby to change the time or duration of fuel addition, or by
changing the fuel addition pressure of the fuel addition valve 13
thereby to change the amount of fuel to be added per unit time.
[0052] In addition, in the above-mentioned embodiment, the time of
fuel addition is uniquely decided as a time when the addition of
fuel is started immediately after the estimated flow speed of the
exhaust gas becomes maximum. However, the present invention is not
limited to this, and the time of fuel addition may be appropriately
changed in consideration of the flow speed and the temperature of
the exhaust gas.
[0053] The exhaust gas purification apparatus according to the
present invention is not limited to the above-mentioned embodiment,
but various changes may be made therein in the range not departing
from the spirit of the present invention.
[0054] While the invention has been described in terms of preferred
embodiments, those skilled in the art will recognize that the
invention can be practiced with modifications within the spirit and
scope of the appended claims.
INDUSTRIAL APPLICABILITY
[0055] According to the present invention, in an exhaust gas
purification apparatus for an internal combustion engine, it is
possible to perform the addition of a reducing agent in a more
appropriate manner.
* * * * *