U.S. patent application number 11/631196 was filed with the patent office on 2008-03-13 for exhaust gas control apparatus for internal combustion engine.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Hideki Aoki, Takeshi Hashizume, Kingo Suyama, Hiroyuki Tominaga.
Application Number | 20080060347 11/631196 |
Document ID | / |
Family ID | 35169964 |
Filed Date | 2008-03-13 |
United States Patent
Application |
20080060347 |
Kind Code |
A1 |
Tominaga; Hiroyuki ; et
al. |
March 13, 2008 |
Exhaust Gas Control Apparatus for Internal Combustion Engine
Abstract
When the temperature of exhaust gas control means (3), which is
provided in an exhaust passage (2) of an internal combustion engine
(1) and which has oxidation function, is increased to a target
temperature in order to recover an exhaust gas control ability of
the exhaust gas control means (3), the method of increasing the
temperature of the exhaust gas control means (3) is switched
between a method in which the temperature of the exhaust gas
control means (3) is increased by controlling an amount of fuel
supplied to the exhaust gas control means (3) and a method in which
the fuel supply to the exhaust gas control means (3) is prohibited
and the temperature of the exhaust gas control means (3) is
increased by controlling an amount of air taken in the internal
combustion engine (1), based on an operation state of the internal
combustion engine (1).
Inventors: |
Tominaga; Hiroyuki;
(Shizuoka-ken, JP) ; Suyama; Kingo; (Shizuoka-ken,
JP) ; Hashizume; Takeshi; (Shizuoka-ken, JP) ;
Aoki; Hideki; (Aichi-ken, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
1, Toyota-Cho
Toyota-Shi
JP
471-8571
|
Family ID: |
35169964 |
Appl. No.: |
11/631196 |
Filed: |
July 19, 2006 |
PCT Filed: |
July 19, 2006 |
PCT NO: |
PCT/IB05/02068 |
371 Date: |
December 29, 2006 |
Current U.S.
Class: |
60/284 ;
60/301 |
Current CPC
Class: |
F01N 3/0821 20130101;
F01N 9/00 20130101; F02D 41/2451 20130101; Y02T 10/26 20130101;
F02D 2009/0237 20130101; F01N 2610/03 20130101; F01N 3/0842
20130101; F02D 41/029 20130101; F02D 41/0002 20130101; F02D 41/18
20130101; Y02T 10/47 20130101; Y02T 10/42 20130101; Y02T 10/12
20130101; F02D 41/0245 20130101; Y02T 10/40 20130101; F02D 41/2441
20130101; F01N 11/002 20130101; F01N 3/0807 20130101; F02D
2009/0222 20130101 |
Class at
Publication: |
060/284 ;
060/301 |
International
Class: |
F01N 3/10 20060101
F01N003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 20, 2004 |
JP |
2004-212155 |
Claims
1. An exhaust gas control apparatus for an internal combustion
engine, comprising: an exhaust gas control device which is provided
in an exhaust passage of an internal combustion engine, and which
has oxidation function; fuel supply device for supplying fuel to
the exhaust gas control device from a position upstream of the
exhaust gas control device; and intake air amount control device
for controlling an amount of air taken in the internal combustion
engine, wherein, when a temperature increasing condition for
increasing a temperature of the exhaust gas control device to a
target temperature in order to recover an exhaust gas control
ability of the exhaust gas control device has been satisfied, if an
engine load of the internal combustion engine is lower than a
predetermined engine load, the temperature of the exhaust gas
control device is increased to or maintained at the target
temperature by controlling an amount of fuel supplied from the fuel
supply device to the exhaust gas control device, and the intake air
amount control device controls the amount of air taken in the
internal combustion engine to an intake air amount that is set
based on an engine rotational speed of the internal combustion
engine and the engine load of the internal combustion engine; and
when the temperature increasing condition has been satisfied, if
the engine load of the internal combustion engine is equal to or
higher than the predetermined engine load, fuel supply from the
fuel supply device is prohibited, and the intake air amount control
device controls the amount of air taken in the internal combustion
engine, whereby the temperature of the exhaust gas control device
is increased to or maintained at the target temperature.
2. The exhaust gas control apparatus for an internal combustion
engine according to claim 1, wherein the exhaust gas control device
includes at least one of a filter which supports an oxidation
catalyst, a filter which supports a NOx storage reduction catalyst,
and a NOx storage reduction catalyst.
3. The exhaust gas control apparatus for an internal combustion
engine according to claim 1, wherein the fuel supply device
performs sub-fuel injection in a cylinder of the internal
combustion engine during a power stroke or an exhaust stroke after
main fuel injection is performed, thereby supplying fuel to the
exhaust gas control device from a position upstream of the exhaust
gas control device.
4. The exhaust gas control apparatus for an internal combustion
engine according to claim 3, wherein even in a case where the
engine load of the internal combustion engine is lower than the
predetermined engine load when the temperature increasing condition
has been satisfied, if the engine rotational speed of the internal
combustion engine is equal to or higher than a predetermined engine
rotational speed, the fuel supply from the fuel supply device is
prohibited, and the intake air amount control device controls the
amount of air taken in the internal combustion engine, whereby the
temperature of the exhaust gas control device is increased to or
maintained at the target temperature.
5. The exhaust gas control apparatus for an internal combustion
engine according to claim 1, wherein the fuel supply device
supplies fuel by using a fuel supply valve that is provided in the
exhaust passage at a position upstream of the exhaust gas control
device, thereby supplying the fuel to the exhaust gas control
device.
6. The exhaust gas control apparatus for an internal combustion
engine according to claim 1, wherein, as the engine rotational
speed of the internal combustion engine that is obtained when the
temperature increasing condition has been satisfied becomes higher,
the predetermined engine load is set to a lower value.
7. The exhaust gas control apparatus for an internal combustion
engine according to claim 1, wherein there is further provided
learning device for learning a relationship between the amount of
air taken in the internal combustion engine and the temperature of
the exhaust gas control device in a state where the fuel supply
from the fuel supply device is not performed, wherein in a case
where the temperature increasing condition has been satisfied, when
an operation state of the internal combustion engine is shifted
from an operation region where the amount of fuel supplied from the
fuel supply device to the exhaust gas control device is controlled,
whereby the temperature of the exhaust gas control device is
increased to the target temperature, to an operation region where
the intake air amount control device controls the amount of air
taken in the internal combustion engine, whereby the temperature of
the exhaust gas control device is increased to the target
temperature, the relationship between the amount of air taken in
the internal combustion engine and the temperature of the exhaust
gas control device is learned by the learning device after the fuel
supply from the fuel supply device is stopped and the temperature
of the exhaust gas control device is brought to a steady state; and
the amount of air taken in the internal combustion engine is
controlled by the intake air amount control device based on the
relationship between the amount of air taken in the internal
combustion engine and the temperature of the exhaust gas control
service that is obtained by learning performed by the learning
device such that the temperature of the exhaust gas control device
is controlled to the target temperature.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to an exhaust gas control apparatus
for an internal combustion engine, which includes exhaust gas
control means that is provided in an exhaust passage of an internal
combustion engine and that has oxidation function.
[0003] 2. Description of the Related Art
[0004] In an exhaust gas control apparatus for an internal
combustion engine, a particulate filter (hereinafter, referred to
as a "filter") which traps particulate matter (hereinafter,
referred to as "PM") in exhaust gas, a NOx storage reduction
catalyst, or the like may be provided in an exhaust passage of an
internal combustion engine. In the case where the filter is
provided in the exhaust passage, the temperature of the filter
needs to be increased when PM accumulated in the filter is removed.
In the case where the NOx storage reduction catalyst is provided in
the exhaust passage, the temperature of the NOx storage reduction
catalyst needs to be increased when SOx stored in the NOx storage
reduction catalyst is reduced.
[0005] There is a known technology related to an exhaust gas
control apparatus for an internal combustion engine, in which a
filter serving as exhaust gas control means is provided in an
exhaust passage. According to the technology, when PM accumulated
in the filter is removed by increasing the temperature of the
filter in order to recover the exhaust gas control ability of the
filter, one of the following methods is selected based on an
operation state of the internal combustion engine, and the
temperature of the filter is increased by the selected method. The
methods are (1) a method in which the temperature of the exhaust
gas is increased by performing a normal operation in a high load
operation region, (2) a method in which fuel injection timing is
retarded, (3) a method in which sub-fuel injection is performed
during power stroke, and EGR gas is introduced, and (4) a method in
which sub-fuel injection is performed during power stroke, and a
flow rate of intake air/exhaust gas is decreased. Such a technology
is disclosed in, for example, Japanese Patent Application
Publication No. JP (A) 2000-161044.
[0006] Also, there is a technology related to an exhaust gas
control apparatus for an internal combustion engine, in which
exhaust gas control means provided in an exhaust passage has
oxidation function. According to the technology, fuel is supplied
to the exhaust gas control means from a position upstream of the
exhaust gas control means, in order to increase the temperature of
the exhaust gas control means. Such a technology is disclosed in,
for example, Japanese Patent Application Publication No. JP (A)
2002-285896, Japanese Patent Application Publication No. JP (A)
2002-235589, and Japanese Patent Application Publication No. JP (A)
05-106518.
[0007] In the exhaust gas control apparatus for an internal
combustion engine including the exhaust gas control means that is
provided in the exhaust passage of the internal combustion engine
and that has oxidation function, when the temperature of the
exhaust gas control means is increased in order to recover the
exhaust gas control ability of the exhaust gas control means, for
example, fuel is supplied to the exhaust gas control means from a
position upstream of the exhaust gas control means by performing
the sub-fuel injection that is performed after the main fuel
injection in the internal combustion engine, and supplying fuel to
the exhaust passage located upstream of the exhaust gas control
means. In this case, the temperature of the exhaust gas control
means is increased by oxidation heat generated due to oxidation of
the fuel that occurs in the exhaust gas control means.
[0008] However, it is sometimes difficult, due to the operation
state of the internal combustion engine, to supply the exhaust gas
control means with a sufficient amount of fuel that is required for
increasing the temperature of the exhaust gas control means to a
target temperature at which the exhaust gas control ability of the
exhaust gas control means can be recovered. For example, as a load
placed on the internal combustion engine (hereinafter, referred to
as an "engine load of the internal combustion engine") becomes
higher, the temperature in a cylinder and the exhaust gas
temperature increase. Accordingly, there is a possibility that the
fuel injected by the sub-fuel injection or the fuel supplied to the
exhaust passage is burned in the cylinder or the exhaust passage,
and therefore, a sufficient amount of fuel is not supplied to the
exhaust gas control means.
SUMMARY OF THE INVENTION
[0009] The invention is made in light of the above-mentioned
circumstances. It is, therefore, an object of the invention to
provide a technology that makes it possible to increase a
temperature of exhaust gas control means provided in an exhaust
passage of an internal combustion engine to a target temperature in
a broader range of an operation state, thereby recovering an
exhaust gas control ability of the exhaust gas control means more
appropriately, in an exhaust gas control apparatus for an internal
combustion engine.
[0010] According to the invention, when the temperature of exhaust
gas control means, which is provided in an exhaust passage of an
internal combustion engine and which has oxidation function, is
increased to a target temperature in order to recover an exhaust
gas control ability of the exhaust gas control means, the method of
increasing the temperature of the exhaust gas control means is
switched between a method in which the temperature of the exhaust
gas control means is increased by controlling an amount of fuel
supplied to the exhaust gas control means and a method in which the
fuel supply to the exhaust gas control means is prohibited and the
temperature of the exhaust gas control means is increased by
controlling an amount of air taken in the internal combustion
engine, based on an operation state of the internal combustion
engine.
[0011] More particularly, according to the invention, there is
provided an exhaust gas control apparatus for an internal
combustion engine including exhaust gas control means which is
provided in an exhaust passage of an internal combustion engine,
and which has oxidation function; fuel supply means for supplying
fuel to the exhaust gas control means from a position upstream of
the exhaust gas control means; and intake air amount control means
for controlling an amount of air taken in the internal combustion
engine, characterized in that when a temperature increasing
condition for increasing a temperature of the exhaust gas control
means to a target temperature in order to recover an exhaust gas
control ability of the exhaust gas control means has been
satisfied, if an engine load of the internal combustion engine is
lower than a predetermined engine load, the temperature of the
exhaust gas control means is increased to or maintained at the
target temperature by controlling an amount of fuel supplied from
the fuel supply means to the exhaust gas control means, and the
intake air amount control means controls the amount of air taken in
the internal combustion engine to an intake air amount that is set
based on an engine rotational speed of the internal combustion
engine and the engine load of the internal combustion engine; and
when the temperature increasing condition has been satisfied, if
the engine load of the internal combustion engine is equal to or
higher than the predetermined engine load, fuel supply from the
fuel supply means is prohibited, and the intake air amount control
means controls the amount of air taken in the internal combustion
engine, whereby the temperature of the exhaust gas control means is
increased to or maintained at the target temperature.
[0012] Examples of the exhaust gas control means according to the
invention include a filter which supports an oxidation catalyst or
a NOx storage reduction catalyst, and a NOx storage reduction
catalyst.
[0013] The fuel supply means according to the invention may perform
sub-fuel injection in a cylinder of the internal combustion engine
during a power stroke or an exhaust stroke after main fuel
injection is performed, thereby supplying fuel to the exhaust gas
control means. Also, the fuel supply means may supply fuel to the
exhaust passage located upstream of the exhaust gas control means
by using a fuel supply valve, thereby supplying the fuel to the
exhaust gas control means.
[0014] The temperature increasing condition is changed depending on
the types of the exhaust gas control means. For example, when the
exhaust gas control means is a filter, the temperature increasing
condition may be a condition in which removal of the PM accumulated
in the filter is performed. When the exhaust gas control means is a
NOx storage reduction catalyst, the temperature increasing
condition may be a condition in which reduction of the SOx stored
in the NOx storage reduction catalyst is performed. Also, the
target temperature is changed depending on the purposes of
increasing the temperature.
[0015] In the invention, when the temperature increasing condition
for increasing the temperature of the exhaust gas control means to
the target temperature has been satisfied, if the engine load of
the internal combustion engine is lower than the predetermined
engine load, the temperature of the exhaust gas control means is
increased to or maintained at the target temperature by controlling
the amount of fuel supplied from the fuel supply means to the
exhaust gas control means. At this time, the intake air amount
control means controls the amount of air taken in the internal
combustion engine to an intake air amount that is set based on the
engine rotational speed of the internal combustion engine and the
engine load of the internal combustion engine.
[0016] However, as described above, as the engine load of the
internal combustion engine increases, the temperature in the
cylinder and the exhaust gas temperature increase. Accordingly,
there is a possibility that the fuel supplied by the fuel supply
means from a position upstream of the exhaust gas control means is
burned in the cylinder or the exhaust passage, in a region where
the engine load is high.
[0017] Therefore, in the invention, when the temperature increasing
condition for increasing the temperature of the exhaust gas control
means to the target temperature has been satisfied, if the engine
load of the internal combustion engine is equal to or higher than
the predetermined engine load, the fuel supply from the fuel supply
means is prohibited. Then, the intake air amount control means
controls the amount of air taken in the internal combustion engine,
whereby the temperature of the exhaust gas control means is
increased to or maintained at the target temperature.
[0018] The predetermined engine load may be a threshold value of
the engine load, at which the temperature in the cylinder or the
exhaust gas temperature becomes high and the fuel supplied from the
fuel supply means is burned in the cylinder or the exhaust
passage.
[0019] Even when fuel is not supplied to the exhaust gas control
means, if the flow rate of the exhaust gas is decreased by
decreasing the intake air amount, the temperature of the exhaust
gas can be increased, and therefore, the temperature of the exhaust
gas control means can be increased. When the engine load of the
internal combustion engine is relatively high, the temperature of
the exhaust gas control means can be increased to the target
temperature only by controlling the intake air amount. When the
engine load of the internal combustion engine is equal to or higher
than the predetermined engine load, prohibition of the fuel supply
makes it possible to suppress an excessive increase in the
temperature of the exhaust gas, which is caused due to burning of
the fuel in the cylinder or the exhaust passage.
[0020] Therefore, according to the invention, the temperature of
the exhaust gas control means can be increased to or maintained at
the target temperature regardless of the engine load of the
internal combustion engine. Namely, the temperature of the exhaust
gas control means can be increased to the target temperature in a
broader range of operation state. Accordingly, the exhaust gas
control ability of the exhaust gas control means can be recovered
more appropriately.
[0021] When fuel is supplied to the exhaust gas control means from
a position upstream of the exhaust gas control means by performing
the sub-fuel injection in the cylinder of the internal combustion
engine during a power stroke or an exhaust stroke after the main
fuel injection is performed, as the engine rotational speed of the
internal combustion engine becomes higher, the time required for
one combustion cycle becomes shorter. Therefore, the number of
times of the sub-fuel injection that can be performed during one
combustion cycle decreases. Accordingly, in the region where the
internal combustion engine is operated at a high engine rotational
speed, it may be difficult to supply a sufficient amount of fuel
required for increasing the temperature of the exhaust gas control
means to the target temperature by performing the sub-fuel
injection.
[0022] Therefore, in the invention, in the case where the fuel
supply means performs sub-fuel injection in a cylinder of the
internal combustion engine during the power stroke or the exhaust
stroke after main fuel injection is performed, thereby supplying
fuel to the exhaust gas control means from a position upstream of
the exhaust gas control means, even if the engine load of the
internal combustion engine is lower than the predetermined engine
load when the temperature increasing condition has been satisfied,
if the engine rotational speed of the internal combustion engine is
equal to or higher than the predetermined engine rotational speed,
fuel supply from the fuel supply means is prohibited. The intake
air amount control means may control the amount of air taken in the
internal combustion engine, whereby the temperature of the exhaust
gas control means is increased to or maintained at the target
temperature.
[0023] The predetermined engine rotational speed may be a threshold
value of the engine rotational speed at which it becomes difficult
to perform the sub-fuel injection number of times that makes it
possible to supply the sufficient amount of fuel required for
increasing the temperature of the exhaust gas control means to the
target temperature.
[0024] According to the invention, when fuel supply to the exhaust
gas control means is performed by the sub-fuel injection, even if
the engine rotational speed of the internal combustion engine is
high, the temperature of the exhaust control means can be increased
to the target temperature in the broader range of the operation
state. Accordingly, the exhaust gas control ability of the exhaust
gas control means can be recovered more appropriately.
[0025] In the internal combustion engine, as the engine rotational
speed increases, the friction that occurs between an inner surface
of the cylinder and a piston increases. Accordingly, even when the
engine rotational speed is high, the torque substantially equal to
that when the engine rotational speed is low is generated.
Accordingly, if the engine load is at substantially the same value,
as the engine rotational speed increases, the amount of fuel
injected by the main fuel injection is increased. However, when
such control of the fuel injection amount is performed, there is a
possibility that, as the engine rotational speed increases, the
temperature of the cylinder and the exhaust gas temperature
increase by an amount corresponding to an amount of increase in the
fuel injected by the main fuel injection. As a result, the fuel
supplied from the fuel supply means may be burned more easily in
the cylinder or the exhaust passage, as the engine rotational speed
increases.
[0026] Accordingly, in the invention, as the engine rotational
speed of the internal combustion engine that is obtained when the
temperature increasing condition has been satisfied increases, the
predetermined engine load may be set to a lower value.
[0027] Setting the predetermined engine load in this manner makes
it possible to suppress an increase in the temperature of the
exhaust gas control means due to the fuel supply performed by the
fuel supply means when the fuel is burned easily in the cylinder or
the exhaust passage. Namely, the temperature of the exhaust gas
control means can be increased to the target temperature in the
broader range of the operation state.
[0028] In the invention, there may be further provided learning
means for learning a relationship between the amount of air taken
in the internal combustion engine and the temperature of the
exhaust gas control means in a state where the fuel supply from the
fuel Supply means is not performed. In a case where the temperature
increasing condition has been satisfied, when the operation state
of the internal combustion engine is shifted from an operation
region (hereinafter, referred to as a "fuel amount control region")
where the amount of fuel supplied from the fuel supply means to the
exhaust gas control means is controlled, whereby the temperature of
the exhaust gas control means is increased to the target
temperature, to an operation region (hereinafter, referred to as a
"intake air amount control region") where the intake air amount
control means controls the amount of air taken in the internal
combustion engine, whereby the temperature of the exhaust gas
control means is increased to the target temperature, the
relationship between the amount of air taken in the internal
combustion engine and the temperature of the exhaust gas control
means may be learned by the learning means after the fuel supply
from the fuel supply means is stopped and the temperature of the
exhaust gas control means is brought to a steady state. The amount
of air taken in the internal combustion engine may be controlled by
the intake air amount control means based on the relationship
between the amount of air taken in the internal combustion engine
and the temperature of the exhaust gas control means that is
obtained by learning performed by the learning means such that the
temperature of the exhaust gas control means is controlled to the
target temperature.
[0029] When the temperature increasing condition has been
satisfied, if the operation state of the internal combustion engine
is shifted from the fuel amount control region to the intake air
amount control region, the fuel supply from the fuel supply means
to the exhaust gas control means is stopped. Accordingly, the
temperature of the exhaust gas control means starts to be
decreased. If the learning means learns the relationship between
the amount of air taken in the internal combustion engine and the
temperature of the exhaust gas control means while the temperature
of the exhaust gas control means is decreasing, the relationship
obtained by the learning may deviate from the actual
relationship.
[0030] Accordingly, in the invention, when the learning means
learns the relationship between the intake air amount and the
temperature of the exhaust gas control means, the learning is
performed after the temperature of the exhaust gas control means is
decreased to a temperature corresponding to the intake air amount
that is obtained when the learning is performed, namely, after the
temperature of the exhaust gas control means is brought to the
steady state. It may be determined that the temperature of the
exhaust gas control means has been brought to the steady state,
when the amount of change in the temperature of the exhaust gas
control means per unit time becomes equal to or smaller than a
predetermined amount.
[0031] The relationship between the intake air amount and the
temperature of the exhaust gas control means is learned when the
temperature of the exhaust gas control means is in the steady
state, and the intake air amount is controlled based on the
relationship obtained by the learning such that the temperature of
the exhaust gas control means is controlled to the target
temperature. Accordingly, when the temperature increasing condition
has been satisfied, even if the operation state of the internal
combustion engine is changed due to a change in the engine load
from a low engine load to a high engine load, the temperature of
the exhaust gas control means can be controlled to the target
temperature more reliably.
[0032] With the exhaust gas control apparatus for an internal
combustion engine according to the invention, the temperature of
the exhaust gas control means provided in the exhaust passage of
the internal combustion engine can be increased to the target
temperature in the broader range of the operation state.
Accordingly, the exhaust gas control ability of the exhaust gas
control means can be recovered more appropriately.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The features, advantages thereof, and technical and
industrial significance of this invention will be better understood
by reading the following detailed description of preferred
embodiments of the invention, when considered in connection with
the accompanying drawings, in which:
[0034] FIG. 1 illustrates a view schematically showing an internal
combustion engine and an intake/exhaust system thereof according to
a first embodiment of the invention;
[0035] FIG. 2 illustrates a flowchart showing a filter temperature
increasing control routine according to the first embodiment;
[0036] FIG. 3 illustrates a time chart showing a relationship among
an engine load, fuel supply from a fuel injection valve, a
temperature of a filter, and an opening amount of a throttle valve
during the filter temperature increasing control;
[0037] FIG. 4 illustrates a flowchart showing a control routine
that is used when the engine load of the internal combustion engine
is changed from an engine load lower than a predetermined engine
load to a load equal to or higher than the predetermined engine
load during the filter temperature increasing control;
[0038] FIG. 5 illustrates a view showing an internal combustion
engine and an intake/exhaust system thereof according to a second
embodiment of the invention;
[0039] FIG. 6 illustrates a graph showing a relationship between an
operation state of the internal combustion engine and a method of
increasing the temperature of the filter; and
[0040] FIG. 7 illustrates a flowchart showing a filter temperature
increasing control routine according to the second embodiment.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0041] In the following description and the accompanying drawings,
the present invention will be described in more detail in terms of
exemplary embodiments.
[0042] First, a first embodiment of the invention will be
described. Hereafter, a description will be made concerning the
case where the invention is applied to a diesel engine for driving
a vehicle. FIG. 1 illustrates a view schematically showing a
structure of an internal combustion engine and an intake/exhaust
system thereof according to the first embodiment.
[0043] An internal combustion engine 1 is a diesel engine for
driving a vehicle. An intake passage 4 and an exhaust passage 2 are
connected to the internal combustion engine 1. An airflow meter 11
and a throttle valve 8 are provided in the intake passage 4. A
particulate filter 3 (hereinafter, simply referred to as a "filter
3") which traps PM, for example, soot in the exhaust gas is
provided in the exhaust passage 2. The filter 3 supports an
oxidation catalyst. The filter 3 may support a NOx storage
reduction catalyst instead of supporting the oxidation catalyst.
Instead of the structure in which the filter 3 supports a catalyst,
a structure, in which an oxidation catalyst, or the like is
provided in the exhaust passage 2 at a position upstream of the
filter 3, may be employed.
[0044] A fuel supply valve 5 which supplies fuel in the exhaust gas
is provided in the exhaust passage 2 at a position upstream of the
filter 3. An exhaust gas temperature sensor 7 which outputs an
electric signal corresponding to the temperature of the exhaust gas
flowing through the exhaust passage 2 is provided in the exhaust
passage 2 at a position downstream of the filter 3.
[0045] For the internal combustion engine 1 having the
above-mentioned structure, an electronic control unit (ECU) 10 for
controlling the internal combustion engine 1 is provided. The ECU
10 controls an operation state of the internal combustion engine 1
based on operation conditions of the internal combustion engine 1
or a request made by a driver. The ECU 10 is electrically connected
to various types of sensors such as the airflow meter 11, the
exhaust gas temperature sensor 7, a crank position sensor 6 that
outputs an electric signal corresponding to a crank angle of the
internal combustion engine 1, and an accelerator pedal operation
amount sensor 9 that outputs an electric signal corresponding to an
accelerator pedal operation amount. The ECU 10 receives signals
output from these sensors. The ECU 10 calculates an engine
rotational speed of the internal combustion engine 1 based on a
value output from the crank position sensor 6, and calculates an
engine load of the internal combustion engine 1 based on a value
output from the accelerator pedal operation amount sensor 9. The
ECU 10 estimates the temperature of the filter 3 based on a value
output from the exhaust gas temperature sensor 7. The ECU 10 is
electrically connected to the throttle valve 8, the fuel supply
valve 5, a fuel injection valve of the internal combustion engine
1, and the like, and therefore the ECU 10 can control these
valves.
[0046] First, a filter temperature increasing control will be
described. If PM is accumulated in the filter 3, the exhaust gas
control ability of the filter 3 is decreased. Therefore, in the
first embodiment, if the amount of PM accumulated in the filter 3
becomes equal to or larger than a predetermined accumulated amount,
the filter temperature increasing control for increasing the
temperature of the filter 3 to the target temperature is performed
in order to oxidize and remove the PM accumulated in the filter 3,
thereby recovering the exhaust gas control ability of the filter 3.
The predetermined accumulated amount is an amount that is smaller
than the PM accumulated amount at which the temperature of the
filter 3 is excessively increased due to the heat generated by
oxidation of the PM, and that is set in advance by an experiment or
the like. The target temperature is a temperature at which the
accumulated PM can be oxidized and removed. The filter temperature
increasing control may be performed at predetermined time intervals
or at predetermined distance intervals.
[0047] Hereafter, the filter temperature increasing control routine
according to the first embodiment will be described with reference
to a flowchart shown in FIG. 2. The routine is stored in the ECU 10
in advance, and repeatedly performed at predetermined time
intervals while the internal combustion engine 1 is operated.
[0048] In this routine, the ECU 10 determines in step S101 whether
an execution condition of the filter temperature increasing control
has been satisfied. When an affirmative determination is made in
step S101, the ECU 10 performs step S102. On the other hand, when a
negative determination is made in step S101, the ECU 10 ends the
routine.
[0049] In step S102, the ECU 10 determines whether the present
engine load of the internal combustion engine 1 is equal to or
higher than a predetermined engine load.
[0050] The predetermined engine load is a threshold value of the
engine load at which it can be determined that the temperature of
the exhaust gas flowing through the exhaust passage 2 located
upstream of the filter 3 has become so high that the fuel supplied
from the fuel supply valve 5 is burned in the exhaust passage 2.
When the engine load of the internal combustion engine 1 is at
substantially the same value, as the engine rotational speed of the
internal combustion engine 1 increases, the amount of fuel injected
by the main fuel injection is increased. Therefore, the temperature
in the cylinder 2 and the exhaust gas temperature may be increased.
Accordingly, in the first embodiment, as the present engine
rotational speed of the internal combustion engine 1 becomes
higher, the predetermined engine load is set to a lower value. In
the first embodiment, a map defining the relationship between the
engine rotational speed of the internal combustion engine 1 and the
predetermined engine load may be stored in the ECU 10 in advance.
When an affirmative determination is made in step S102, the ECU 10
performs step S103. On the other hand, when a negative
determination is made in step S102, the ECU 10 performs step
S104.
[0051] In step S104, the ECU 10 causes the fuel supply valve 5 to
supply fuel, thereby supplying fuel to the filter 3, and controls
the amount of fuel supplied from the fuel supply valve 5. Thus,
when the present temperature of the filter 3 is lower than the
target temperature, the ECU 10 increases the temperature of the
filter 3 to the target temperature. On the other hand, when the
present temperature of the filter 3 is equal to the target
temperature, the ECU 10 maintains the temperature of the filter 3
at the target temperature. Namely, fuel is supplied from the fuel
supply valve 5, whereby the fuel is supplied to the oxidation
catalyst supported by the filter 3. Then, the temperature of the
filter 3 is increased by the heat generated due to oxidation of the
fuel that occurs in the oxidation catalyst. When fuel is supplied
from the fuel supply valve 5 in step S104, the opening amount of
the throttle valve 8 is controlled to an opening amount that is set
based on the engine rotational speed and the engine load of the
internal combustion engine 1. At this time, the opening amount of
the throttle valve 8 may be different from an opening amount that
is used when the engine rotational speed of the internal combustion
engine 1 is at substantially the same value and the engine load of
the internal combustion engine 1 is at substantially the same value
in the normal operation state. After the temperature of the filter
3 is increased to the target temperature in step S104, the ECU 10
ends the routine.
[0052] On the other hand, in step S103, the ECU 10 prohibits fuel
supply from the fuel supply valve 5 and decreases the opening
amount of the throttle valve 8, thereby decreasing the intake air
amount and increasing the temperature of the filter 3.
[0053] As described above, if fuel is supplied from the fuel supply
valve 5 when the engine load is equal to or higher than the
predetermined engine load, the fuel is burned in the exhaust
passage 2. Therefore, in the case where fuel is supplied from the
fuel supply valve 5, it may be difficult to supply the oxidation
catalyst supported by the filter 3 with the sufficient amount of
fuel required for increasing the temperature of the filter 3 to the
target temperature. Accordingly, in step S103, the opening amount
of the throttle valve 8 is controlled, namely, the intake air
amount is controlled. Thus, when the present temperature of the
filter 3 is lower than the target temperature, the temperature of
the filter 3 is increased to the target temperature. On the other
hand, when the present temperature of the filter 3 is equal to the
target temperature, the temperature of the filter 3 is maintained
at the target temperature.
[0054] In this case, the exhaust gas temperature is increased by
decreasing the intake air amount, and the temperature of the filter
3 is increased with an increase in exhaust gas temperature. In this
case, the relationship between the opening amount of the throttle
valve 8 and the temperature of the filter 3 in the state where fuel
supply from the fuel supply valve 5 is not performed is learned
before the opening amount of the throttle valve 8 is changed, and
the opening amount of the throttle valve 8 is controlled based on
the relationship obtained by the learning. After the temperature of
the filter 3 is increased to the target temperature in step S103,
the ECU 10 ends the routine.
[0055] According to the control routine described so far, the
temperature of the filter 3 can be increased to the target
temperature regardless of the engine load of the internal
combustion engine 1. Namely, the temperature of the filter 3 can be
increased to the target temperature in a broader range of operation
state. It is, therefore, possible to oxidize and remove the PM
accumulated in the filter 3 in the broader range of operation
state. When the engine load of the internal combustion engine 1 is
equal to or higher than the predetermined engine load, prohibition
of fuel supply from the fuel supply valve 5 makes it possible to
suppress an excessive increase in the exhaust gas temperature
caused due to burning of the fuel in the exhaust passage 2.
According to the first embodiment, the exhaust gas control ability
of the filter 3 can be recovered appropriately.
[0056] In the above-mentioned control routine, when fuel is
supplied to the filter 3 in order to increase the temperature of
the filter 3, the fuel is supplied from the fuel supply valve 5 to
the exhaust gas. However, fuel may be supplied to the filter 3 from
a position upstream of the filter 3 by performing sub-fuel
injection in the cylinder of the internal combustion engine 1
during the power stroke or the exhaust stroke after the main fuel
injection is performed, instead of by performing fuel supply from
the fuel supply valve 5.
[0057] The control routine may be applied to the case where the
filter 3 supports a NOx storage reduction catalyst (hereinafter,
referred to as a "NOx catalyst"), and SOx stored in the NOx
catalyst is reduced. In this case, the temperature of the filter
may start to be increased when the amount of SOx stored in the NOx
catalyst becomes equal to or larger than a predetermined storage
amount. Also, the target temperature is a temperature at which the
SOx stored in the NOx catalyst can be reduced.
[0058] The above-mentioned control routine may be applied to the
case where the NOx catalyst is provided instead of the filter 3,
and the temperature of the NOx catalyst is increased.
[0059] Next, the learning of the relationship between the opening
amount of the throttle valve and the temperature of the filter will
be described. Namely, a description will be made concerning the
control that is performed when the engine load of the internal
combustion engine 1 is changed from an engine load lower than the
predetermined engine load to an engine load equal to or higher than
the predetermined engine load during the filter temperature
increasing control, with reference to FIG. 3. FIG. 3 illustrates a
time chart showing a relationship among the engine load, the fuel
supply from the fuel supply valve 5, the temperature of the filter
3, and the opening amount of the throttle valve 8 during the filter
temperature increasing control. The chained line in the region
showing the engine load indicates the predetermined engine load,
and the chained line in the region showing the temperature of the
filter indicates the target temperature.
[0060] As described above, when the engine load of the internal
combustion engine 1 is lower than the predetermined engine load
during the filter temperature increasing control, fuel supply from
the fuel supply valve 5 is performed. If the engine load of the
internal combustion engine 1 is changed to an engine load equal to
or higher than the predetermined engine load, fuel supply from the
fuel supply valve 5 is stopped upon completion of the change in the
engine load, as shown in FIG. 3. As a result, the temperature of
the filter 3, which has been maintained at the target temperature,
starts to decrease.
[0061] In the first embodiment, when the engine load of the
internal combustion engine 1 is equal to or higher than the
predetermined engine load during the filter temperature increasing
control, the temperature of the filter 3 is increased to the target
temperature by controlling the opening amount of the throttle valve
8. In this case, the ECU 10 learns the relationship between the
temperature of the filter 3 and the opening amount of the throttle
valve 8 in the state where fuel supply from the fuel supply valve 5
is not performed. The opening amount of the throttle valve 8 is
controlled based on the relationship obtained by the learning.
However, if the ECU 10 learns the relationship between the
temperature of the filter 3 and the opening amount of the throttle
valve 8 while the temperature of the filter 3 is decreasing, the
ECU 10 erroneously learns that the relationship using a temperature
that is higher than the temperature of the filter 3 actually
corresponding to the opening amount of the throttle valve 8. Then,
if ECU 10 controls the opening amount of the throttle valve 8 in
order to increase the temperature of the filter 3 to the target
temperature based on the relationship between the temperature of
the filter 3 and the opening amount of the throttle valve 8 that is
obtained by learning performed in the above-mentioned manner, the
actual temperature of the filter 3 deviates from the target
temperature.
[0062] Accordingly, in the first embodiment, after the fuel supply
from the fuel supply valve 5 is stopped and the temperature of the
filter 3 is brought into the steady state (namely, at time "a" in
FIG. 3), the ECU 10 learns the relationship between the temperature
of the filter 3 and the opening amount of the throttle valve 8.
Then, the opening amount of the throttle valve 8 is controlled such
that the temperature of the filter 3 is increased to the target
temperature based on the relationship between the temperature of
the filter 3 and the opening amount of the throttle valve 8 that is
obtained by learning performed at time "a" shown in FIG. 3.
[0063] Next, the control routine that is used when the engine load
is changed during the filter temperature increasing control will be
described. Hereafter, a description will be made concerning the
control routine that is used when the engine load of the internal
combustion engine 1 is changed from an engine load lower than the
predetermined engine load to an engine load equal to or higher than
the predetermined engine load during the filter temperature
increasing control, with reference to a flowchart in FIG. 4. The
routine is stored in the ECU 10 in advance, and repeatedly
performed at predetermined intervals during the filter temperature
increasing control.
[0064] In the routine, the ECU 10 determines in step S201 whether
the engine load of the internal combustion engine 1 has been
changed from an engine load lower than the predetermined engine
load to an engine load equal to or higher than the predetermined
engine load. When an affirmative determination is made in step
S201, the ECU 10 performs step S202. On the other hand, when a
negative determination is made in step S201, the ECU 10 ends the
routine.
[0065] In step S202, the ECU 10 stops the fuel supply from the fuel
supply valve 5.
[0066] Next, the ECU 10 determines in step S203 whether the
temperature of the filter 3 is in the steady state. An affirmative
determination is made in step S203 if the amount of change in the
temperature of the filter 3 per unit time becomes equal to or
smaller than a predetermined amount. When an affirmative
determination is made in step S203, the ECU 10 performs step S204.
On the other hand, when a negative determination is made in step
S203, the ECU 10 ends the routine. When a negative determination is
made in step S203, the ECU 10 may repeatedly perform step S203.
[0067] In step S204, the ECU 10 learns the relationship between the
opening amount of the throttle valve 8 and the temperature of the
filter 3.
[0068] Next, in step S205, the ECU 10 controls the opening amount
of the throttle valve 8 based on the relationship between the
opening amount of the throttle valve 8 and the temperature of the
filter 3 that is obtained by learning performed in step S204, so as
to increase the temperature of the filter 3 to the target
temperature, after which the ECU 10 ends the routine.
[0069] According to the control routine described so far, the
relationship between the opening amount of the throttle valve 8 and
the temperature of the filter 3 is learned when the temperature of
the filter 3 is in the steady state, and the opening amount of the
throttle valve 8 is controlled based on the relationship obtained
by the learning such that the temperature of the filter 3 becomes
the target temperature. Thus, even when the operation state of the
internal combustion engine 1 is changed due to a change in the
engine load from a low engine load to a high engine load while the
temperature increase condition is satisfied, the temperature of the
filter 3 can be controlled to the target temperature more
reliably.
[0070] In the first embodiment, when an exhaust throttle valve is
provided in the exhaust passage 2, control of the opening amount of
the exhaust throttle valve may be performed along with the control
of the opening amount of the throttle valve 8.
[0071] Next, a second embodiment of the invention will be
described. FIG. 5 illustrates a view schematically showing an
internal combustion engine and an intake/exhaust system thereof
according to the second embodiment. As shown in FIG. 5, the
schematic structure of the internal combustion engine and the
intake/exhaust system thereof according to the second embodiment is
the same as that according to the first embodiment except that the
fuel Supply valve 5 is not provided in the second embodiment.
[0072] First, the filter temperature increasing control will be
described. In the second embodiment, when the temperature of the
filter 3 is increased by supplying fuel to the filter 3 (the
oxidation catalyst supported by the filter 3), sub-fuel injection
is performed in the cylinder of the internal combustion engine 1
during the power stroke or the exhaust stroke after the main fuel
injection is performed, whereby fuel is supplied to the filter 3
from a position upstream of the filter 3.
[0073] When fuel is supplied to the filter 3 by the sub-fuel
injection, as the engine rotational speed of the internal
combustion engine 1 becomes higher, the time required for one
combustion cycle becomes shorter. Therefore, the number of times of
the sub-fuel injection that can be performed during one combustion
cycle decreases. Accordingly, in the region where the internal
combustion engine 1 is operated at a high engine rotational speed,
it may be difficult to supply a sufficient amount of fuel required
for increasing the temperature of the filter 3 to the target
temperature by performing the sub-fuel injection.
[0074] Accordingly, in the second embodiment, as shown in FIG. 6,
when the filter temperature increasing control is performed while
the operation state of the internal combustion engine 1 is in a
region (A), namely, when the engine load of the internal combustion
engine 1 is lower than the predetermined engine load and the engine
rotational speed of the internal combustion engine 1 is lower than
the predetermined engine rotational speed, the temperature of the
filter 3 is increased to the target temperature by performing the
sub-fuel injection and controlling the amount of fuel injected by
the sub-fuel injection. When the filter temperature increasing
control is performed while the operation state of the internal
combustion engine 1 is in a region (B), namely, when the engine
load of the internal combustion engine 1 is equal to or higher than
the predetermined engine load or the engine rotational speed of the
internal combustion engine 1 is equal to or higher than the
predetermined engine rotational speed, the sub-fuel injection is
prohibited, and the temperature of the filter 3 is increased to the
target temperature by controlling the opening amount of the
throttle valve 8.
[0075] FIG. 6 illustrates a graph showing the relationship between
the operation state of the internal combustion engine 1 and a
method of increasing the temperature of the filter 3. In FIG. 6,
the vertical axis indicates the engine load, and the horizontal
axis indicates the engine rotational speed. The dashed line
indicates the boundary between the region (A) and the region (B).
The solid line indicates the maximum engine load corresponding to
the engine rotational speed.
[0076] The boundary between the region (A) and the region (B) is
set based on the predetermined engine load and the predetermined
engine rotational speed. The predetermined engine load is the same
as the predetermined engine load according to the first embodiment.
As the engine rotational speed becomes higher, the predetermined
engine load is set to a lower value. The predetermined engine
rotational speed is the engine rotational speed that is set in
advance. The predetermined engine rotational speed is the threshold
value of the engine rotational speed at which it becomes difficult
to perform the sub-fuel injection number of times that makes it
possible to supply the sufficient amount of fuel required for
increasing the temperature of the filter 3 to the target
temperature.
[0077] Next, the filter temperature increasing control routine
according to the second embodiment will be described with reference
to a flowchart shown in FIG. 7. The routine is the same as the
filter temperature increasing control routine shown in FIG. 2
except that step S304 is performed instead of step S104, and step
S303 is added. Therefore, only step S303 and step S304 will be
described, and the other steps will not be described here. As in
the case of the routine shown in FIG. 2, the routine according to
the second embodiment is stored in the ECU 10 in advance, and
repeatedly performed at predetermined time intervals during the
operation of the internal combustion engine.
[0078] In the routine, when a negative determination is made in
step S102, the ECU 10 performs step S303.
[0079] The ECU 10 determines in step S303 whether the engine
rotational speed of the internal combustion engine 1 is equal to or
higher than the predetermined engine rotational speed. When an
affirmative determination is made in step S303, the ECU 10 performs
step S103. On the other hand, when a negative determination is made
in step S303, the ECU 10 performs step S304.
[0080] In step S304, the ECU 10 performs the sub-fuel injection in
the cylinder of the internal combustion engine 1, and controls the
amount of fuel injected by the sub-fuel injection. Thus, when the
present temperature of the filter 3 is lower than the target
temperature, the temperature of the filter 3 is increased to the
target temperature. When the present temperature of the filter 3 is
equal to the target temperature, the temperature of the filter 3 is
maintained at the target temperature. When the sub-fuel injection
is performed in step S304, the opening amount of the throttle valve
8 is controlled to the opening amount that is set based on the
engine load of the internal combustion engine 1.
[0081] According to the control routine described so far, even if
the engine rotational speed of the internal combustion engine 1 is
high when fuel is supplied to the filter 3 by the sub-fuel
injection, the temperature of the filter 3 can be increased to the
target temperature more reliably. Namely, the temperature of the
filter 3 can be increased to the target temperature in a broader
range of the operation state. Accordingly, the PM accumulated in
the filter 3 can be oxidized and removed in the broader range of
operation state.
[0082] In the second embodiment, when the operation state of the
internal combustion engine 1 is shifted from the region (A) to the
region (B) shown in FIG. 6 during the filter temperature increasing
control, the sub-fuel injection is stopped upon completion of the
shifting. Then, the ECU 10 learns the relationship between the
temperature of the filter 3 and the opening amount of the throttle
valve 8 after the sub-fuel injection is stopped and the temperature
of the filter 3 is brought to the steady state. Then, the ECU 10
controls the opening amount of the throttle valve 8 based on the
relationship obtained by the learning so as to increase the
temperature of the filter 3 to the target temperature.
[0083] Thus, even when the operation state of the internal
combustion engine 1 is changed during the filter temperature
increasing control, the temperature of the filter 3 can be
controlled to the target temperature more reliably.
[0084] As in the case of the filter temperature control routine
according to the first embodiment, the control routine according to
the second embodiment can be applied to the case where SOx stored
in the NOx catalyst is reduced when the NOx catalyst is supported
by the filter 3 or the NOx catalyst is provided instead of the
filter 3.
* * * * *