U.S. patent application number 14/361475 was filed with the patent office on 2014-11-13 for control apparatus for internal combustion engine.
The applicant listed for this patent is Takashi Nishikiori. Invention is credited to Takashi Nishikiori.
Application Number | 20140331651 14/361475 |
Document ID | / |
Family ID | 48534877 |
Filed Date | 2014-11-13 |
United States Patent
Application |
20140331651 |
Kind Code |
A1 |
Nishikiori; Takashi |
November 13, 2014 |
CONTROL APPARATUS FOR INTERNAL COMBUSTION ENGINE
Abstract
This control apparatus for an internal combustion engine
includes: a turbo-supercharger; a port injection valve and an
in-cylinder injection valve; and catalysts. The control apparatus
determines whether or not blow-by of gas to an exhaust passage from
an intake passage through a combustion chamber occurs, or whether
or not a condition in which the blow-by of gas is likely to occur
is satisfied. If the determination is affirmative, the control
apparatus sets the fuel injection timing for the port injection
valve or the in-cylinder injection valve so as to execute fuel
injection after an exhaust valve is closed. Further, if the
aforementioned determination is affirmative, the control apparatus
sets the fuel injection amount so that the air-to-fuel ratio
defined using the amount of air passing through the intake valve
coincides with a value leaner than the stoichiometric air-to-fuel
ratio.
Inventors: |
Nishikiori; Takashi;
(Susono-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nishikiori; Takashi |
Susono-shi |
|
JP |
|
|
Family ID: |
48534877 |
Appl. No.: |
14/361475 |
Filed: |
December 1, 2011 |
PCT Filed: |
December 1, 2011 |
PCT NO: |
PCT/JP2011/077833 |
371 Date: |
May 29, 2014 |
Current U.S.
Class: |
60/285 |
Current CPC
Class: |
Y02T 10/12 20130101;
F02B 29/0406 20130101; F02D 13/0261 20130101; F01N 3/20 20130101;
Y02T 10/144 20130101; F02D 13/0238 20130101; F02D 41/40 20130101;
Y02T 10/44 20130101; F02D 41/0007 20130101; F02M 26/04 20160201;
F02M 69/046 20130101; F02D 41/3094 20130101; F02B 25/145 20130101;
F02D 41/1475 20130101; Y02T 10/40 20130101; F02D 2250/08 20130101;
Y02T 10/18 20130101 |
Class at
Publication: |
60/285 |
International
Class: |
F01N 3/20 20060101
F01N003/20 |
Claims
1. A control apparatus for an internal combustion engine,
comprising: a supercharger that supercharges intake air; a fuel
injection valve that injects fuel into the internal combustion
engine; a catalyst that is installed in an exhaust passage and is
capable of purifying exhaust gas; an air-to-fuel ratio sensor that
is installed in the exhaust passage on an upstream side of the
catalyst to detect an air-to-fuel ratio of exhaust gas at an
upstream of the catalyst; a variable valve operating mechanism that
is capable of adjusting a valve overlap period during which an
opening period of an intake valve and an opening period of an
exhaust valve overlap with each other; intake valve passing-through
air amount obtaining means for obtaining an amount of air passing
through the intake valve; overlap period adjusting means for
adjusting the valve overlap period so that when blow-by of gas to
the exhaust passage from an intake passage through a combustion
chamber occurs or when a condition in which the blow-by of gas is
likely to occur is satisfied, an amount of the blow-by in which the
air-to-fuel ratio of exhaust gas detected by the air-to-fuel ratio
sensor is equal to or lower than a value obtained by adding a
predetermined value to a stoichiometric air-to-fuel ratio is
obtained; injection timing setting means for, if the amount of the
blow-by is not obtained by an adjustment of the valve overlap
period by the overlap period adjusting means in a case where the
blow-by of gas occurs or the condition in which the blow-by of gas
is likely to occur is satisfied, setting a fuel injection timing
for the fuel injection valve so that fuel injection is executed
after the exhaust valve is closed; and fuel injection amount
controlling means for, if the amount of the blow-by is not obtained
by an adjustment of the valve overlap period by the overlap period
adjusting means in a case where the blow-by of gas occurs or the
condition in which the blow-by of gas is likely to occur is
satisfied, setting a fuel injection amount so that an air-to-fuel
ratio defined using the amount of air passing through the intake
valve becomes a value leaner than the stoichiometric air-to-fuel
ratio.
2. The control apparatus for the internal combustion engine
according to claim 1, wherein the control apparatus for the
internal combustion engine further comprises catalyst temperature
determination means for determining whether or not a temperature of
the catalyst is higher than a predetermined value, and wherein the
fuel injection amount controlling means sets a fuel injection
amount so that when the blow-by of gas occurs or the condition in
which the blow-by of gas is likely to occur is satisfied and the
temperature of the catalyst is higher than the predetermined value,
the air-to-fuel ratio defined using the amount of air passing
through the intake valve becomes a value leaner than the
stoichiometric air-to-fuel ratio.
3. The control apparatus for the internal combustion engine
according to claim 1, wherein the fuel injection amount controlling
means includes air-to-fuel ratio lean-correction means for
correcting the fuel injection amount so that the air-to-fuel ratio
of exhaust gas detected by the air-to-fuel ratio sensor becomes a
value leaner than the stoichiometric air-to-fuel ratio.
4. The control apparatus for the internal combustion engine
according to claim 3, wherein the air-to-fuel ratio lean-correction
means further includes lean-degree determination means for, when an
amount of the blow-by of gas is large, changing a target
air-to-fuel ratio of exhaust gas to a value leaner than that when
the amount of the blow-by of gas is small.
5. The control apparatus for the internal combustion engine
according to claim 4, wherein the lean-degree determination means
changes the target air-to-fuel ratio of exhaust gas to a leaner
value so that an air-to-fuel ratio defined using an in-cylinder
charged air amount obtained by subtracting the amount of the
blow-by of gas from the amount of air passing through the intake
valve coincides with the stoichiometric air-to-fuel ratio.
6. The control apparatus for the internal combustion engine
according to claim 1, wherein the control apparatus for the
internal combustion engine further comprises: air-to-fuel ratio
feedback controlling means for adjusting the fuel injection amount
so that the air-to-fuel ratio of exhaust gas detected by the
air-to-fuel ratio sensor becomes a predetermined target air-to-fuel
ratio; air-to-fuel ratio feedback suspend means for, when the
blow-by of gas occurs or when the condition in which the blow-by of
gas is likely to occur is satisfied, suspending an adjustment of
the fuel injection amount by the air-to-fuel ratio feedback
controlling means; and in-cylinder air amount obtaining means for
obtaining an in-cylinder charged air amount out of the amount of
air passing through the intake valve, wherein the fuel injection
amount controlling means sets the fuel injection amount so that
when the blow-by of gas occurs or when the condition in which the
blow-by of gas is likely to occur is satisfied, an air-to-fuel
ratio defined using the in-cylinder charged air amount becomes the
stoichiometric air-to-fuel ratio.
7. The control apparatus for the internal combustion engine
according to claim 1, wherein the variable valve operating
mechanism is capable of changing opening and closing timings of the
intake valve and a closing timing of the exhaust valve, and wherein
the overlap period adjusting means executes an adjustment of the
closing timing of the exhaust valve in priority to an adjustment of
the opening and closing timings of the intake valve when
controlling the amount of the blow-by of gas by adjusting the valve
overlap period.
8. The control apparatus for the internal combustion engine
according to claim 1, wherein the fuel injection valve includes a
first fuel injection valve that injects fuel into the intake
passage and a second fuel injection valve that injects fuel into a
cylinder, and wherein the control apparatus for the internal
combustion engine further comprises fuel injection valve selection
means for selecting the second fuel injection valve as a fuel
injection valve that is used when fuel injection control is
performed by the fuel injection timing setting means and the fuel
injection amount controlling means.
9. The control apparatus for the internal combustion engine
according to claim 1, wherein the control apparatus for the
internal combustion engine further comprises gas blow-by
determination means for determining whether or not the blow-by of
gas occurs, or whether or not the condition in which the blow-by of
gas is likely to occur is satisfied, and wherein the gas blow-by
determination means determines that the blow-by of gas is occurring
when the air-to-fuel ratio of the exhaust gas detected by the
air-to-fuel ratio sensor is leaner than or equal to a sum of the
stoichiometric air-to-fuel ratio and a predetermined value.
10. A control apparatus for an internal combustion engine,
comprising: a supercharger that supercharges intake air; a fuel
injection valve that injects fuel into the internal combustion
engine; a catalyst that is installed in an exhaust passage and is
capable of purifying exhaust gas; an air-to-fuel ratio sensor that
is installed in the exhaust passage on an upstream side of the
catalyst to detect an air-to-fuel ratio of exhaust gas at an
upstream of the catalyst; a variable valve operating mechanism that
is capable of adjusting a valve overlap period during which an
opening period of an intake valve and an opening period of an
exhaust valve overlap with each other; and a controller that is
programmed to: obtain an amount of air passing through the intake
valve; adjust the valve overlap period so that when blow-by of gas
to the exhaust passage from an intake passage through a combustion
chamber occurs or when a condition in which the blow-by of gas is
likely to occur is satisfied, an amount of the blow-by in which the
air-to-fuel ratio of exhaust gas detected by the air-to-fuel ratio
sensor is equal to or lower than a value obtained by adding a
predetermined value to a stoichiometric air-to-fuel ratio is
obtained; set a fuel injection timing for the fuel injection valve
so that fuel injection is executed after the exhaust valve is
closed if the amount of the blow-by is not obtained by an
adjustment of the valve overlap period in a case where the blow-by
of gas occurs or the condition in which the blow-by of gas is
likely to occur is satisfied; and set a fuel injection amount so
that an air-to-fuel ratio defined using the amount of air passing
through the intake valve becomes a value leaner than the
stoichiometric air-to-fuel ratio if the amount of the blow-by is
not obtained by an adjustment of the valve overlap period in a case
where the blow-by of gas occurs or the condition in which the
blow-by of gas is likely to occur is satisfied.
Description
TECHNICAL FIELD
[0001] The present invention relates to a control apparatus for an
internal combustion engine, and more particular to a control
apparatus for an internal combustion engine that is suitable for
controlling an supercharger-equipped internal combustion
engine.
BACKGROUND ART
[0002] So far, for example, Patent Document 1 discloses an internal
combustion engine having a turbo-supercharger. In this conventional
internal combustion engine, the amount of blow-by of fresh air that
blows through a combustion chamber to an exhaust passage from an
intake passage is estimated on the basis of, for example, the
oxygen concentration (air-to-fuel ratio) of exhaust gas detected by
an air-to-fuel ratio sensor. Further, a target air-to-fuel ratio
and a target ignition timing are corrected on the basis of the
estimated amount of blow-by of fresh air.
[0003] More specifically, Patent Document 1 discloses that since,
as the amount of blow-by of fresh air decreases, an in-cylinder
scavenging action (scavenging effect) during a valve overlap period
weakens to increase an in-cylinder residual gas, knock becomes
likely to occur. Further, in Patent Document 1, making rich the
air-to-fuel ratio (an increase in fuel injection amount) is
performed in accordance with a decrease in the amount of blow-by of
fresh air, that is to say, a weakness in the in-cylinder scavenging
action.
[0004] If the fuel injection amount is increased as disclosed in
Patent Document 1 in a situation in which blow-by of fresh air is
occurring, a part of the injected fuel may be blown to the exhaust
passage as well as the fresh air, or a gas including unburned fuel
in a cylinder (a gas air-to-fuel ratio of which is richer than the
stoichiometric air-to-fuel ratio) may be discharged to the exhaust
passage. If the unburned fuel that is introduced into the exhaust
passage as described above flows into a catalyst to bring about
chemical reactions with oxygen trapped (stored) in the catalyst,
the temperature of the catalyst rapidly rises. As a result of this,
there is a concern that the deterioration of the catalyst may be
facilitated.
[0005] Including the above described document, the applicant is
aware of the following documents as related art of the present
invention.
CITATION LIST
Patent Documents
[0006] Patent Document 1: Japanese Laid-open Patent Application
Publication No. 2007-23082 [0007] Patent Document 2: Japanese
Laid-open Patent Application Publication No. 2007-263083 [0008]
Patent Document 3: Japanese Laid-open Patent Application
Publication No. 2008-75549 [0009] Patent Document 4: Japanese
Laid-open Patent Application Publication No. 2010-216464
SUMMARY OF INVENTION
[0010] The present invention has been made to solve the problem as
described above, and has its object to provide a control apparatus
for an internal combustion engine which can prevent combustion of
unburned fuel from occurring inside a catalyst while increasing the
torque of the internal combustion engine using scavenging
effect.
[0011] The present invention is a control apparatus for an internal
combustion engine that includes: a supercharger; a fuel injection
valve; a catalyst; injection timing setting means; intake valve
passing-through air amount obtaining means; and fuel injection
amount controlling means.
[0012] The supercharger supercharges intake air. The fuel injection
valve injects fuel into the internal combustion engine. The
catalyst is installed in an exhaust passage and is capable of
purifying exhaust gas. When blow-by of gas to the exhaust passage
from an intake passage through a combustion chamber occurs or when
a condition in which the blow-by of gas is likely to occur is
satisfied, the injection timing setting means sets a fuel injection
timing for the fuel injection valve so that fuel injection is
executed after an exhaust valve is closed. The intake valve
passing-through air amount obtaining means obtains the amount of
air passing through an intake valve. The fuel injection amount
controlling means sets a fuel injection amount so that when the
blow-by of gas occurs or the condition in which the blow-by of gas
is likely to occur is satisfied, an air-to-fuel ratio defined using
the amount of air passing through the intake valve becomes a value
leaner than a stoichiometric air-to-fuel ratio.
[0013] According to the present invention, the setting of the fuel
injection timing by the fuel injection amount controlling means can
prevent fuel from blowing to the exhaust passage as well as fresh
air during the valve overlap period. Further, according to the
setting of the fuel injection timing by the fuel injection amount
controlling means, although the air-to-fuel ratio defined using the
amount of air passing through the intake valve becomes leaner than
the stoichiometric air-to-fuel ratio, the fuel injection amount can
be set so that the air-to-fuel ratio that is defined using the
in-cylinder charged air amount that is obtained by subtracting the
amount of blow-by of fresh air from the amount of air passing
through the intake valve becomes a value near the stoichiometric
air-to-fuel ratio. Consequently, the exhaust gas (burned gas)
discharged from the cylinder can be prevented from including
unburned fuel. The control of the present embodiment can therefore
achieve the prevention of the blow-by of unburned fuel to the
exhaust passage and the prevention of the discharge of unburned
fuel from the cylinder. This makes it possible to prevent oxygen
trapped (stored) in the catalyst from bringing about an oxygen
reaction with unburned fuel inside the catalyst, and to thereby
prevent the temperature of the catalyst from rapidly rising at the
time of occurrence of the blow-by of gas. In addition, according to
the present invention, the air-to-fuel ratio defined using the
in-cylinder charged air amount can be put close to the
stoichiometric air-to-fuel ratio even when such control of the fuel
injection amount is being performed. Therefore, the present
invention can prevent the deterioration of the catalyst from being
facilitated while ensuring an increase in the torque of the
internal combustion engine by use of the scavenging effect.
[0014] Moreover, the control apparatus for the internal combustion
engine in the present invention may further comprises catalyst
temperature determination means that determines whether or not the
temperature of the catalyst is higher than a predetermined value.
Further, the fuel injection amount controlling means may set a fuel
injection amount so that when the blow-by of gas occurs or the
condition in which the blow-by of gas is likely to occur is
satisfied and the temperature of the catalyst is higher than the
predetermined value, the air-to-fuel ratio defined using the amount
of air passing through the intake valve becomes a value leaner than
the stoichiometric air-to-fuel ratio.
[0015] This makes it possible to prevent the deterioration of the
catalyst from being facilitated while ensuring an increase in the
torque of the internal combustion engine by use of the scavenging
effect in a situation such that the deterioration of the catalyst
is concerned due to the fact that the temperature of the catalyst
is high.
[0016] Moreover, the control apparatus for the internal combustion
engine in the present invention may further comprises an
air-to-fuel ratio sensor that is installed in the exhaust passage
on the upstream side of the catalyst to detect an air-to-fuel ratio
of exhaust gas at the upstream of the catalyst. Further, the fuel
injection amount controlling means may include air-to-fuel ratio
lean-correction means that corrects the fuel injection amount so
that the air-to-fuel ratio of exhaust gas detected by the
air-to-fuel ratio sensor becomes a value leaner than the
stoichiometric air-to-fuel ratio.
[0017] This makes it possible to set the fuel injection amount so
that the air-to-fuel ratio defined using the amount of air passing
through the intake valve coincides with a value leaner than the
stoichiometric air-to-fuel ratio, by use of the air-to-fuel
lean-correction means that corrects the fuel injection amount so
that the air-to-fuel ratio of exhaust gas detected by the
air-to-fuel ratio sensor coincides with a value leaner than the
stoichiometric air-to-fuel ratio.
[0018] Moreover, the air-to-fuel ratio lean-correction means in the
present invention may further includes lean-degree determination
means that, when the amount of the blow-by of gas is large, changes
a target air-to-fuel ratio of exhaust gas to a value leaner than
that when the amount of the blow-by of gas is small.
[0019] This makes it possible to suppress the execution of the
increase in the target air-to-fuel ratio to the minimum necessary
regardless of the amount of the blow-by of fresh air. The
deterioration of the exhaust emission due to the fact that the
ambient air-to-fuel ratio of the catalyst is deviated from the
vicinity of the stoichiometric air-to-fuel ratio can therefore be
minimally suppressed.
[0020] Moreover, the lean-degree determination means in the present
invention may change the target air-to-fuel ratio of exhaust gas to
a leaner value so that an air-to-fuel ratio defined using an
in-cylinder charged air amount obtained by subtracting the amount
of the blow-by of gas from the amount of air passing through the
intake valve coincides with the stoichiometric air-to-fuel
ratio.
[0021] This makes it possible to control the air-to-fuel ratio
defined using the in-cylinder charged air amount, that is to say,
the air-to-fuel ratio at the time of combustion in the cylinder so
as to be a value near the stoichiometric air-to-fuel ratio
regardless of the amount of the blow-by of fresh air.
[0022] Moreover, the control apparatus for the internal combustion
engine in the present invention may further comprises: an
air-to-fuel ratio sensor that is installed in the exhaust passage
on the upstream side of the catalyst to detect an air-to-fuel ratio
of exhaust gas at the upstream of the catalyst; air-to-fuel ratio
feedback controlling means that adjusts the fuel injection amount
so that the air-to-fuel ratio of exhaust gas detected by the
air-to-fuel ratio sensor becomes a predetermined target air-to-fuel
ratio; air-to-fuel ratio feedback suspend means that, when the
blow-by of gas occurs or when the condition in which the blow-by of
gas is likely to occur is satisfied, suspends the adjustment of the
fuel injection amount by the air-to-fuel ratio feedback controlling
means; and in-cylinder air amount obtaining means that obtains an
in-cylinder charged air amount out of the amount of air passing
through the intake valve. Further, the fuel injection amount
controlling means may set the fuel injection amount so that, when
the blow-by of gas occurs or when the condition in which the
blow-by of gas is likely to occur is satisfied, an air-to-fuel
ratio defined using the in-cylinder charged air amount becomes the
stoichiometric air-to-fuel ratio.
[0023] This makes it possible to set the fuel injection amount so
that the air-to-fuel ratio defined using the amount of air passing
through the intake valve coincides with a value leaner than the
stoichiometric air-to-fuel ratio, by use of a manner that sets the
fuel injection amount so that the air-to-fuel ratio defined using
the in-cylinder charged air amount coincides with the
stoichiometric air-to-fuel ratio using the air-to-fuel ratio
feedback suspend means and the in-cylinder air amount obtaining
means.
[0024] Moreover, the control apparatus for the internal combustion
engine in the present invention may further comprises: a variable
valve operating mechanism that is capable of changing opening and
closing timings of the intake valve and a closing timing of the
exhaust valve; and overlap period adjusting means that, when
controlling the amount of the blow-by of gas by adjusting a valve
overlap period during which an opening period of the intake valve
and an opening period of the exhaust valve overlap with each other
in a case where the blow-by of gas occurs or the condition in which
the blow-by of gas is likely to occur is satisfied, executes the
adjustment of the closing timing of the exhaust valve in priority
to the adjustment of the opening and closing timings of the intake
valve.
[0025] If the closing timing of the intake valve is changed by
adjusting the opening and closing timings of the intake valve for
the adjustment of the valve overlap period, the actual compression
ratio of the internal combustion engine changes and ease of
occurrence of knock changes. In this regard, the aforementioned
manner, which executes the adjustment of at least the closing
timing of the exhaust valve in priority to the adjustment of the
opening and closing timings of the intake valve, makes it possible
to prevent the fluctuation of the air-to-fuel ratio (the large
dilution) of the exhaust gas due to the blow-by of gas (fresh air)
while preventing knock resistance from being impaired as much as
possible.
[0026] Moreover, the fuel injection valve in the present invention
may further includes a first fuel injection valve that injects fuel
into the intake passage and a second fuel injection valve that
injects fuel into a cylinder. Further, the control apparatus for
the internal combustion engine further comprises fuel injection
valve selection means that selects the second fuel injection valve
as a fuel injection valve that is used when fuel injection control
is performed by the fuel injection timing setting means and the
fuel injection amount controlling means.
[0027] This makes it possible to prevent wet fuel attaching to the
periphery of an intake port from blowing to the exhaust passage as
well as fresh air during the valve overlap period, and to therefore
more surely prevent the blow-by of unburned fuel to the exhaust
passage.
[0028] Moreover, the control apparatus for the internal combustion
engine in the present invention may further comprises: gas blow-by
determination means that determines whether or not the blow-by of
gas occurs, or whether or not the condition in which the blow-by of
gas is likely to occur is satisfied; and an air-to-fuel ratio
sensor that is installed in the exhaust passage on the upstream
side of the catalyst to detect an air-to-fuel ratio of exhaust gas
at the upstream of the catalyst. Further, the gas blow-by
determination means may determine that the blow-by of gas is
occurring when the air-to-fuel ratio of the exhaust gas detected by
the air-to-fuel ratio sensor is leaner than or equal to a sum of
the stoichiometric air-to-fuel ratio and a predetermined value.
[0029] This makes it possible to accurately discriminate the
monotonous fluctuation of the air-to-fuel ratio due to, for
example, a variation of the air-to-fuel ratio between cylinders,
from the blow-by of gas (fresh air).
BRIEF DESCRIPTION OF DRAWINGS
[0030] FIG. 1 is a diagram for explaining a system configuration of
an internal combustion engine according to a first embodiment of
the present invention;
[0031] FIG. 2 is a diagram that represents one example of a control
state concerning a valve timing of each of the intake valve and the
exhaust valve shown in Fi
[0032] FIG. 3 is a diagram for explaining the scavenging effect of
the blow-by of fresh air into an exhaust passage from an intake
passage via a combustion chamber;
[0033] FIG. 4 is a flowchart of a routine that is executed in the
first embodiment of the present invention;
[0034] FIG. 5 is a flowchart of a routine that is executed in a
second embodiment of the present invention; and
[0035] FIG. 6 is a flowchart of a routine that is executed in a
third embodiment of the present invention.
DESCRIPTION OF EMBODIMENTS
First Embodiment
Explanation of System Configuration
[0036] FIG. 1 is a diagram for explaining a system configuration of
an internal combustion engine 10 according to a first embodiment of
the present invention. the system shown in FIG. 1 includes an
internal combustion engine 10. A piston 12 is provided in a
cylinder of the internal combustion engine 10. A combustion chamber
14 (see FIG. 2) is firmed on the top side of the piston 12 in the
cylinder. There are an intake passage 16 and an exhaust passage 18
in communication with the combustion chamber 14.
[0037] An air filter 20 is installed in the vicinity of an inlet of
the intake passage 16. In the intake passage 16 on the downstream
side of the air filter 20, an air flow meter 22 that outputs a
signal corresponding to the flow rate of air sucked into the intake
passage 16 is installed. A compressor 24a of a turbo-supercharger
24 is disposed in the intake passage 16 on the downstream side of
the air flow meter 22. Further, to bypass the compressor 24a, an
air bypass passage 26 is connected to the intake passage 16. At
some point in the air bypass passage 26, an air bypass valve (ABV)
28 for controlling the flow rate of the air that flows through the
air bypass passage 26 is disposed.
[0038] An intercooler 30 for cooling air that is compressed by the
compressor 24a is disposed in the intake passage 16 on the
downstream side of the compressor 24a. An electronically-controlled
throttle valve 32 is installed in the intake passage 16 on the
downstream side of the intercooler 30. In addition, in the intake
passage 16 on the upstream side of the throttle valve 32 and on the
downstream side of the intercooler 30, a throttle upstream side
pressure sensor 34 for detecting intake pressure at that position
is installed; and in the intake passage 16 on the downstream side
of the throttle valve 32 (the collector section of an intake
manifold), a throttle downstream side pressure sensor 36 for
detecting intake pressure at that position is installed.
[0039] A port injection valve 38 for injecting fuel into an intake
port is installed in the intake passage 16 (each intake port) after
branching off toward each cylinder. Further, there are installed in
each cylinder of the internal combustion engine 10, an in-cylinder
injection valve 40 for directly injecting fuel into the combustion
chamber 14 (into the cylinder) and a spark plug 42 for igniting
air-fuel mixture gas. In the internal combustion engine 10, in
order to stabilize combustion and improve fuel efficiency, at least
one of the port injection valve 38 and the in-cylinder injection
valve 40 is selected in accordance with operating conditions.
[0040] Moreover, the internal combustion engine 10 includes an
intake variable valve operating mechanism 46 which makes valve
opening characteristics of an intake valve 44 variable, and an
exhaust variable valve operating mechanism 50 which makes valve
opening characteristics of an exhaust valve 48 variable. More
specifically, it is assumed herein that each of these variable
valve operating mechanisms 46 and 50 includes a variable phase
mechanism (VVT (Variable Valve Timing) mechanism) which can
continuously changing the opening and closing timings of the intake
valve 44 or exhaust valve 48 while fixing the operating angle
thereof; by changing the rotation phase of a camshaft (not
illustrated in the drawings) with respect to the rotation phase of
a crankshaft 52. Moreover, an intake cam angle sensor 54 and an
exhaust cam angle sensor 56, which detect the rotation angle of
each camshaft, that is, an intake cam angle and an exhaust cam
angle, are disposed respectively in the vicinity of the intake
camshaft and the exhaust camshaft.
[0041] A turbine 24b of the turbo-supercharger 24 is disposed in
the exhaust passage 18. As exhaust purifying catalysts for
purifying exhaust gas (herein, three-way catalysts), an upstream
catalyst (SC: start catalyst) 58 and a downstream catalyst (UFC:
under floor catalyst) 60 are installed in the exhaust passage 18 on
the downstream side of the turbine 24 in series in the order from
the upstream side. A muffler 62 is installed in the exhaust passage
18 on the downstream side of the downstream catalyst 60.
[0042] Moreover, at the exhaust passage 18 on the upstream side of
the upstream catalyst 58, an A/F sensor 64 is installed to produce
an output substantially linear relative to the air-to-fuel ratio of
exhaust gas flowing into the upstream catalyst 58 (exhaust gas
discharged from each cylinder). At a section between the upstream
catalyst 58 and the downstream catalyst 60 in the exhaust passage
18, an O.sub.2 sensor 66 is installed to produce a rich output when
the exhaust gas flowing out through the upstream catalyst 58 is
richer than the stoichiometric air-to-fuel ratio and to produce a
lean output when the exhaust gas is leaner than the stoichiometric
air-to-fuel ratio.
[0043] Moreover, an exhaust bypass passage 68 that bypasses the
turbine 24b and connects the inlet side of the turbine 24b with the
outlet side thereof is connected to the exhaust passage 18. A waste
gate valve (WGV) 70 that opens and closes the exhaust bypass
passage 68 is installed at some point of the exhaust bypass passage
68. Further, the internal combustion engine 10 includes an exhaust
gas recirculation passage (EGR passage) 72 that connects the intake
passage 16 with the exhaust passage 18. At some point of the EGR
passage 72, an EGR valve 74 is installed to adjust the amount of
exhaust gas that flows back into the intake passage 16 from the
exhaust passage 18 (EGR gas). Furthermore, a crank angle sensor 76
for detecting a crank angle and an engine speed is installed in the
vicinity of the crankshaft 52.
[0044] Furthermore, the system shown in FIG. 1 includes an ECU
(Electronic Control Unit) 80. There are connected to an input
section of the ECU 80, various types of sensors for detecting the
operational state of the internal combustion engine 10, such as the
air flow meter 22, the throttle upstream pressure sensor 36, the
cam angle sensors 54 and 56, the A/F sensor 64, the O.sub.2 sensor
66 and the crank angle sensor 76 that are described above. In
addition, there are connected to an output section of the ECU 80,
various types of actuators for controlling the operation of the
internal combustion engine 10, such as the ABV 28, the throttle
valve 32, the port injection valve 38, the in-cylinder injection
valve 40, the spark plug 42, the variable valve operating
mechanisms 46 and 50, the WGV 70 and the EGR valve 74 that are
described above. The ECU 80 controls the operational state of the
internal combustion engine 10 by actuating the various types of
actuators on the basis of the output of each sensor and
predetermined programs.
[0045] In the system of the internal combustion engine 10 that
includes the above described configuration, a base fuel injection
amount is basically set so that an air-to-fuel ratio defined using
the amount of air passing through the intake valve 44 coincides
with the theoretical air-to-fuel ratio (stoichiometric air-to-fuel
ratio) during operation of the internal combustion engine 10,
expect for predetermined exceptional operating conditions (such as
the time of cold start). Specifically, in order to enable such base
fuel injection amount to be obtained, the ECU 80 stores a map (not
illustrated in the drawings) that defines the base fuel injection
amount in accordance with the operating state (the intake air
amount (the load factor) based on the output of the air flow meter
22, and the engine speed), and calculates the base fuel injection
amount in accordance with the present operating state with
reference to such map.
[0046] Further, in the aforementioned system of the internal
combustion engine 10, after the A/F sensor 64 and the O.sub.2
sensor 66 are activated following the start-up of the internal
combustion engine 10, a main feedback control is executed on the
basis of the output of the A/F sensor 64 on the upstream side. In
the main feedback control, correction of fuel injection amount with
respect to the base fuel injection amount is performed so that the
air-to-fuel ratio of the exhaust gas that flows into the upstream
catalyst 58 coincides with a target air-to-fuel ratio (basically,
the stoichiometric air-to-fuel ratio). In a sub feedback control
that is executed on the basis of the output of the O.sub.2 sensor
66 on the downstream side, the contents of the main feedback
control are corrected so that the air-to-fuel ratio of the exhaust
gas that flows out to the downstream of the downstream catalyst 60
coincides with the stoichiometric air-to-fuel ratio.
[Scavenging Effect of Blow-by of Fresh Air into Exhaust Passage
from Intake Passage Via Combustion Chamber]
[0047] FIG. 2 is a diagram that represents one example of a control
state concerning a valve timing of each of the intake valve 44 and
the exhaust valve 46 shown in FIG. 1.
[0048] In the control state shown in FIG. 2, a valve overlap period
during which the valve opening period of the intake valve 44 and
the valve opening period of the exhaust valve 48 overlap with each
other (hereinafter, simply abbreviated as "O/L period") is provided
in the vicinity of the intake/exhaust top dead center. As described
above, the opening and closing timings (the phase) of the intake
valve 44 can be changed using the intake variable valve operating
mechanism 46 within a predetermined variable range, and the opening
and closing timings (the phase) of the exhaust valve 48 can be
changed using the exhaust variable valve operating mechanism 50
within a predetermined variable range. The aforementioned O/L
period can be increased and decreased by changing, using these
variable valve operating mechanisms 46 and 50, at least one of the
advance angle value of the opening and closing timings of the
intake valve 44 and the retard angle value of the opening and
closing timings of the exhaust valve 48.
[0049] FIG. 3 is a diagram for explaining the scavenging effect of
the blow-by of fresh air into the exhaust passage 18 from the
intake passage 16 via the combustion chamber 14. In FIG. 3, the
illustration of the in-cylinder injection valve 40 is omitted.
[0050] When intake pressure (on the upstream of the intake valve
44) is higher than exhaust pressure (on the downstream of the
exhaust valve) with the supercharging by the turbo-supercharger 24
in a state in which the O/L period is provided as shown in FIG. 2,
a phenomenon occurs in which the fresh air (intake gas) blows
through the combustion chamber 14 to the exhaust passage 18 from
the intake passage 16 as shown in FIG. 3. Although in-cylinder
residual gas, the amount of which corresponds to at least the
clearance volume of the combustion chamber 14, normally exists, an
occurrence of such blow-by of fresh air allows the residual gas to
be extruded and scavenged using the fresh air from the intake
passage 16 and to be thereby replaced with the fresh air
(scavenging effect). This can produces effects such as an increase
in the torque of the internal combustion engine 10.
[0051] It is noted that the aforementioned scavenging effect is
produced when an O/L amount is intentionally set in order to
achieve this effect in a predetermined low-speed and high-load
region in which the effect can be expected to be produced, or is
produced when a condition in which the effect can be produced is
satisfied in a situation where an O/L amount is set for another
purpose.
[Control of First Embodiment]
[0052] It is ideal that in order to increase the torque of the
internal combustion engine 10 using the above described scavenging
effect, the amount of the fresh air introduced for the scavenging
is just the amount for sweeping the in-cylinder residual gas the
amount of which corresponds to the clearance volume of the
combustion chamber 14. However, it is difficult to continue to
control the O/L amount so that such an ideal scavenging can be
always achieved during operation of the internal combustion engine
10.
[0053] When an O/L amount is provided to utilize the scavenging
effect, oxygen that is included in the fresh air that has blown
through the combustion chamber 14 by the action of excess
scavenging is trapped (stored) by the catalysts 58 and 60 (mainly,
the upstream catalyst 58). In addition, the amount of in-cylinder
charged air that is actually charged in the cylinder when the
blow-by of fresh air is occurring corresponds to the amount
obtained by subtracting the blow-by fresh air amount from the
amount of air that passes through the intake valve 44 to flow into
the cylinder (intake valve passing-through air amount).
Nevertheless, if the fuel injection amount is controlled so that
the air-to-fuel ratio that is defined using the intake valve
passing-through air amount coincides with the stoichiometric
air-to-fuel ratio, the air-to-fuel ratio in the cylinder at the
time of combustion becomes a value richer than the stoichiometric
air-to-fuel ratio. As a result of this, if a rich gas that is
subsequently discharged from the cylinder (a gas that includes
unburned fuel that has not been used for combustion and is richer
than the stoichiometric air-to-fuel ratio) flows into the upstream
catalyst 58, the unburned fuel in this rich gas and the oxygen that
has been trapped by the upstream catalyst 58 brings about an
oxidation reaction. Further, when fuel injection is performed
during the O/L period or prior to the O/L period, unburned fuel
flows into the upstream catalyst 58 as well as the blow-by fresh
air. Also in this case, the unburned fuel that has flown into the
upstream catalyst 58 brings about an oxygen reaction with oxygen.
As a result, the temperature of the upstream catalyst 58 rapidly
rises. Therefore, there is a concern that the deterioration of the
upstream catalyst 58 may be facilitated due to such a temperature
rise if the upstream catalyst 58 is in a high-temperature state.
Moreover, the problem as described above arises more prominently in
a case such that when utilizing the scavenging effect, the
air-to-fuel ratio is controlled to a predetermined air-to-fuel
ratio for best torque that is richer than the stoichiometric
air-to-fuel ratio in order to increase the toque.
[0054] Accordingly, in the present embodiment, the following fuel
injection control is executed if an occurrence of the
aforementioned blow-by of gas has been detected in a condition in
which the temperature of the upstream catalyst 58 is higher than a
predetermined value (a situation in which the deterioration of the
upstream catalyst 58 is concerned). Specifically, when these
conditions (in which the blow-by of fresh air occurs and the
temperature of the upstream catalyst 58 is high) are satisfied, the
fuel injection timing is set (changed) so that the fuel injection
is executed after the exhaust valve 48 is closed (that is, after
the O/L period is terminated). Further, if these conditions are
satisfied, the base fuel injection amount is corrected using the
aforementioned (main) air-to-fuel ratio feedback control so that
the air-to-fuel ratio of the exhaust gas detected by the A/F sensor
64 (that is, the air-to-fuel ratio of the exhaust gas flowing into
the upstream catalyst 58) becomes a value leaner than the
stoichiometric air-to-fuel ratio.
[0055] FIG. 4 is a flowchart that represents a control routine
executed by the ECU 80 to implement the control according to the
first embodiment of the present invention. It is assumed that the
present routine is repeatedly executed at a predetermined control
cycle.
[0056] In the routine shown in FIG. 4, first, adaptation values of
target valve timings (VVT) of the intake valve 44 and the exhaust
valve 48 are obtained (step 100). The ECU 80 stores a map (not
illustrated in the Drawings) that previously defines the adaptation
values of the target VVT with a relation to the engine speed and
the load factor (air charge rate). In this map, as for a
predetermined low-speed and high-load region in which the
scavenging effect can be expected, the O/L period for utilizing the
scavenging effect is set with values according to the operating
state. In present step 100, the adaptation values of the target VVT
in accordance with the present operating state (engine speed and
load factor) are obtained with reference to such map.
[0057] Next, it is determined whether or not a precondition
concerning execution of the control according to the present
embodiment is satisfied (step 102). Specifically, the precondition
in present step 102 is a condition for judging whether or not an
operating condition in which the blow-by of gas (scavenging effect)
actually occurs is satisfied in a temperature situation in which
the deterioration of the upstream catalyst 58 is concerned. The
present precondition is related to: whether or not the temperature
of the upstream catalyst 58 is higher than a predetermined value;
whether or not the intake pressure (throttle downstream pressure)
is higher than the exhaust pressure (nearly, atmospheric air
pressure); and whether or not the advance angle value of the
opening and closing timings of the intake valve 44 is larger than a
predetermined adaptation value A (or the retard angle value of the
opening and closing timings of the exhaust valve 48 is larger than
a predetermined adaptation value B). In addition, when the engine
speed varies, the opening time periods of the intake and exhaust
valves 44 and 48 during the O/L period change even if the opening
areas thereof are equal. Therefore, the engine speed is also
considered in the determination of the precondition in present step
102. Incidentally, for example, the temperature of the upstream
catalyst 58 can be estimated on the basis of the operation record
of the internal combustion engine 10, or may be obtained using a
temperature sensor additionally included.
[0058] If it is determined that the aforementioned precondition in
step 102 is satisfied, it is determined whether or not the
air-to-fuel ratio (A/F) of the exhaust gas detected by the A/F
sensor 64 is higher than (that is, leaner than) a value obtained by
adding a predetermined value a (for example, 0.5) to the
theoretical air-to-fuel ratio (stoichiometric air-to-fuel ratio)
(step 104). If the blow-by of fresh air occurs in a situation in
which the air-to-fuel ratio of the exhaust gas is being controlled
to the stoichiometric air-to-fuel ratio by the above described
air-to-fuel ratio feedback control, the output of the A/F sensor 64
changes to a value that is leaner than the stoichiometric
air-to-fuel ratio. Accordingly, it is determined in present step
104 whether or not the blow-by of fresh air is actually occurring
by determining whether or not the air-to-fuel ratio of the exhaust
gas is larger than the value by adding the predetermined value a to
the stoichiometric air-to-fuel ratio. The predetermined value a is
a value that is used for preventing erroneous decision due to, for
example, a variation in the air-to-fuel ratio between
cylinders.
[0059] If the determination of step 104 becomes affirmative
following the affirmative determination of step 102, that is to
say, if an occurrence of the blow-by of fresh air is detected, it
is determined whether or not there is a situation in which only the
port injection valve 38 is being used (step 106). As a result of
this, if the port injection valve 38 and the in-cylinder injection
valve 40 are concurrently being used, a fuel injection valve that
is used for the fuel injection control is switched so as to only
use the in-cylinder injection valve 40 (step 108). On that basis,
the fuel injection timing is retarded so that the fuel injection is
executed after the exhaust valve 48 is closed (that is to say,
after the O/L? period elapses) (step 110). According to the
in-cylinder injection valve 40, the fuel injection can be executed
at an arbitrary timing in the intake stroke and the compression
stoke. According to the processing of present step 110, the retard
of the fuel injection timing is executed so that fuel is not blown
to the exhaust passage 18 as well as fresh air during the O/L,
period. Specifically, the fuel injection is executed during the
intake stroke after closing of the exhaust valve 48, the subsequent
compression stroke, or a period that extends over the both.
[0060] If, on the other hand, it is determined in step 106 that
there is in a situation in which only the port injection valve 38
is being used, the manner of fuel injection using the port
injection valve 38 is changed to intake synchronous injection that
is executed after the exhaust valve 48 is closed (that is to say,
after the O/L period elapses) (step 112). As for the fuel injection
using the port injection 38, intake asynchronous injection, in
other words, fuel injection that is executed during the course of
the exhaust stroke is normally executed. In present step 112, the
switching to the intake synchronous injection from such intake
asynchronous injection is performed so that fuel is supplied into
the combustion chamber 14 as well as intake air during the course
of the intake stroke after the exhaust valve 48 is closed.
[0061] After the processing of step 110 or 112 is executed, the
target air-to-fuel ratio of the above described (main) air-to-fuel
ratio feedback control is made lean so that the air-to-fuel ratio
of the exhaust gas that is detected by the A/F sensor 64 becomes a
value leaner than the stoichiometric air-to-fuel ratio (step 114).
As described above, the base fuel injection amount itself is set so
that the air-to-fuel ratio defiled using the intake valve
passing-through air amount coincides with the stoichiometric
air-to-fuel ratio. In present step 114, a correction (lean
correction) to subtract a predetermined fuel amount from the base
fuel injection amount is executed so that the air-to-fuel ratio
detected by the A/F sensor 64 becomes a value leaner than the
stoichiometric air-to-fuel ratio.
[0062] In present step 114, the degree of lean of the target
air-to-fuel ratio (that is to say, the decrease amount of fuel with
respect to the base fuel injection amount) is fixed in accordance
with the amount of blow-by of fresh air. More specifically, the
fuel injection amount is adjusted (decreased) so that the
air-to-fuel ratio that is defined using the in-cylinder charged air
amount that is obtained by subtracting the amount of blow-by of
fresh air from the intake valve passing-through air amount
coincides with the stoichiometric air-to-fuel ratio. As the amount
of blow-by of fresh air increases, the in-cylinder charged air
amount, which is the amount of air charged in the cylinder, out of
the intake valve passing-through air amount decreases. Accordingly,
in present step 114, as the amount of blow-by fresh air increases,
the degree of lean of the target air-to-fuel ratio (the decrease
amount of the fuel injection amount) is adjusted so as to be
increased. It is noted that the amount of blow-by of fresh air to
the exhaust passage 18 itself can be calculated on the basis of the
intake pressure (throttle downstream pressure), the exhaust
pressure, the O/L amount and the engine speed (the opening time
period in the O/L period). In this case, the aforementioned intake
pressure can be obtained using the throttle downstream pressure
sensor 36, and the exhaust pressure can be obtained on the basis of
a turbine rotational speed that is separately estimated, the
opening degree of the WGV 70, the intake air amount detected by the
air flow meter 22, and the like.
[0063] Incidentally, when the blow-by of fresh air has stopped
being detected due to the fact that the determination of step 102
or 104 becomes negative after the determination of step 104 becomes
affirmative, the fuel injection control is returned to the control
at the normal time.
[0064] According to the routine shown in FIG. 4 described so far,
if an occurrence of the blow-by of fresh air (scavenging effect) is
detected in a situation in which the deterioration of the upstream
catalyst 58 is concerned, the fuel injection timing is changed by
the processing of step 110 or 112. This can prevent fuel from
blowing to the exhaust passage 18 as well as fresh air during the
O/L period even when either of the port injection valve 38 and the
in-cylinder injection valve 40 is used. In other words, all amount
of the injected fuel is surely left in the cylinder. Further,
according to the increase in the target air-to-fuel ratio with the
processing of step 114, although the air-to-fuel ratio defined
using the intake valve passing-through air amount becomes leaner
than the stoichiometric air-to-fuel ratio, the fuel injection
amount is corrected so that the air-to-fuel ratio that is defined
using the in-cylinder charged air amount that is obtained by
subtracting the amount of blow-by of fresh air from the intake
valve passing-through air amount coincides with the stoichiometric
air-to-fuel ratio. Consequently, the exhaust gas (burned gas)
discharged from the cylinder can be prevented from including
unburned fuel.
[0065] Accordingly, the control of the present embodiment can
achieve the prevention of the blow-by of unburned fuel to the
exhaust passage 8 and the prevention of the discharge of unburned
fuel from the cylinder. This makes it possible to prevent oxygen
trapped (stored) in the upstream catalyst 58 from bringing about an
oxygen reaction with unburned fuel inside the upstream catalyst 58,
and to thereby prevent the temperature of the upstream catalyst 58
from rapidly rising at the time of occurrence of the blow-by of
fresh air. In addition, according to the control of the present
embodiment, the air-to-fuel ratio defined using the in-cylinder
charged air amount can be maintained at the stoichiometric
air-to-fuel ratio even when such increase in the target air-to-fuel
ratio is being performed. Therefore, the control can prevent the
deterioration of the upstream catalyst 58 from being facilitated
while ensuring an increase in the torque of the internal combustion
engine 10 by use of the scavenging effect.
[0066] Moreover, according to the aforementioned routine, the
degree of lean of the target air-to-fuel ratio is fixed in
accordance with the amount of blow-by of fresh air. This can
suppress the execution of the increase in the target air-to-fuel
ratio to the minimum necessary regardless of the amount of the
blow-by of fresh air, and the deterioration of the exhaust emission
due to the fact that the ambient air-to-fuel ratio of the upstream
catalyst 58 is deviated from the vicinity of the stoichiometric
air-to-fuel ratio can therefore be minimally suppressed. Further,
according to the increase in the target air-to-fuel ratio in step
114, the air-to-fuel ratio defined using the in-cylinder charged
air amount, that is to say, the air-to-fuel ratio at the time of
combustion in the cylinder can be controlled so as to be a value
near the stoichiometric air-to-fuel ratio regardless of the amount
of the blow-by of fresh air.
[0067] Moreover, according to the aforementioned routine, the fuel
injection valve that is used for the fuel injection control is
switched so as to use only the in-cylinder injection valve 40 if
the port injection valve 38 and the in-cylinder injection valve 40
are concurrently being used when an occurrence of the blow-by of
fresh air (scavenging effect) is detected. At the time of use of
the port injection valve 38, a part of the injected fuel attaches
to the periphery of the intake port as a wet fuel. In contrast, the
switching is performed so that all amount of the fuel is injected
using the in-cylinder injection valve 40, and can thereby prevent
the wet fuel from blowing to the exhaust passage 18 as well as
fresh air during the O/L period. Consequently, the blow-by of
unburned fuel to the exhaust passage 18 can be more surely
prevented.
[0068] Furthermore, the processing of steps 102 and 104 in the
aforementioned routine multiply determines whether or not the
blow-by of fresh air (scavenging effect) occurs. The above
described increase in the target air-to-fuel ratio can suppress the
deterioration of the upstream catalyst 58 while ensuring an
increase in the torque of the internal combustion engine 10.
However, the ambient air-to-fuel ratio of the upstream catalyst 58
is changed from a value near the stoichiometric air-to-fuel ratio
to a value leaner than that. Thus, the execution of the increase in
the target air-to-fuel ratio can be suppressed to the minimum
necessary by more accurately detecting an occurrence of the blow-by
of fresh air (scavenging effect) with the processing of steps 102
and 104. In addition, such determination makes it possible to
accurately discriminate the monotonous fluctuation of the
air-to-fuel ratio due to, for example, a variation of the
air-to-fuel ratio between cylinders, from the blow-by of fresh
air.
[0069] In the first embodiment, which has been described above, the
ECU 80 executes the aforementioned processing of step 110 or 112,
whereby the "injection timing setting means" according to the
present invention is realized; the ECU 80 calculates the intake
valve passing-through air amount using a known relational
expression and the air flow meter 22, whereby the "intake valve
passing-through air amount obtaining means" according to the
present invention is realized; and the ECU 80 executes the
aforementioned processing of step 114, whereby the "fuel injection
amount controlling means" according to the present invention is
realized. In addition, the aforementioned processing of step 104
corresponds to the "determination of whether or not blow-by of gas
to the exhaust passage from an intake passage through a combustion
chamber occurs" according to the present invention; and the
aforementioned processing of step 102 corresponds to the
"determination of whether or not a condition in which the blow-by
of gas is likely to occur is satisfied" according to the present
invention.
[0070] Moreover, in the first embodiment, the ECU 80 executes the
aforementioned processing of step 112, whereby the "catalyst
temperature determination means" according to the present invention
is realized.
[0071] Moreover, in the first embodiment, the A/F sensor 64
corresponds to the "air-to-fuel ratio sensor" according to the
present invention; and the ECU 80 executes the aforementioned
processing of step 114, whereby the "air-to-fuel ratio
lean-correction means" according to the present invention is
realized.
[0072] Moreover, in the first embodiment, the ECU 80 executes the
aforementioned processing of step 114, whereby the "lean-degree
determination means" according to the present invention is
realized.
[0073] Moreover, in the first embodiment, the port injection valve
38 corresponds to the "first fuel injection valve" according to the
present invention; and the in-cylinder injection valve 40
corresponds to the "second fuel injection valve" according to the
present invention. In addition, the ECU 80 executes the
aforementioned processing of step 108 when the aforementioned
determination of step 106 is negative, whereby the "fuel injection
valve selection means" according to the present invention is
realized.
[0074] Moreover, in the first embodiment, the ECU 80 executes the
aforementioned processing of steps 102 and 104, whereby the "gas
blow-by determination means" according to the present invention is
realized.
Second Embodiment
[0075] Next, a second embodiment of the present invention will be
described with reference to FIG. 5.
[0076] The system of the present embodiment can be implemented by
using the hardware configuration shown in FIG. 1 and causing the
ECU 80 to execute the routine shown in FIG. 5 described below,
instead of the routine shown in FIG. 4.
[0077] In the above described first embodiment, when an occurrence
of the blow-by of fresh air (scavenging effect) is detected in a
situation in which the deterioration of the upstream catalyst 58 is
concerned, an increase in the target air-to-fuel ratio is executed
using the air-to-fuel ratio feedback control, as well as the retard
of the fuel injection timing. In contrast, when an occurrence of
the blow-by of fresh air (scavenging effect) is detected in a
situation in which the deterioration of the upstream catalyst 58 is
concerned, the system of the present embodiment is the same as the
system of the above described first embodiment in executing the
retard of the fuel injection timing and is different from the first
embodiment in the following points. More specifically, in the
present embodiment, the air-to-fuel ratio feedback control is
suspended (that is to say, the control is changed to air-to-fuel
ratio open-loop control that is not associated with feedback), and
the fuel injection amount is set so that the air-to-fuel ratio
defined using the in-cylinder charged air amount coincides with the
stoichiometric air-to-fuel ratio.
[0078] FIG. 5 is a flowchart that represents a control routine
executed by the ECU 80 to implement the control according to the
second embodiment of the present invention. In FIG. 5, the same
steps as the steps shown in FIG. 4 in the first embodiment will be
assigned with the same reference numerals, and the description
thereof will be omitted or simplified.
[0079] In the routine shown in FIG. 5, after the processing of step
110 or 112 is executed, next, the air-to-fuel ratio feedback
control (the above described main and sub feedback controls
correspond to this) is suspended, and is changed to the air-to-fuel
ratio open-loop control that is not associated with feedback (step
200).
[0080] Next, the in-cylinder charged air amount is calculated (step
202). As already described in the first embodiment, the in-cylinder
charged air amount in a situation in which the blow-by of fresh air
is detected can be calculated (estimated) by subtracting the amount
of the blow-by of fresh air to the exhaust passage 18, from the
intake valve passing-through air amount based on the output of the
air flow meter 22.
[0081] Next, the fuel injection amount is set so that the
air-to-fuel ratio defined using the in-cylinder charged air amount
calculated in step 202 coincides with the stoichiometric
air-to-fuel ratio (step 204). In present step 204, the use of the
aforementioned map that defines the base fuel injection amount for
obtaining the stoichiometric air-to-fuel ratio is suspended, and
the fuel injection amount is fixed so that the stoichiometric
air-to-fuel ratio is obtained on the basis of the in-cylinder
charged air amount. If the determination of step 102 or 104 is
negative, the aforementioned air-to-fuel ratio feedback control
(closed-loop) is executed as normal (step 206).
[0082] According to the routine shown in FIG. 5 described so far,
if an occurrence of the blow-by of fresh air (scavenging effect) is
detected in a situation in which the deterioration of the upstream
catalyst 58 is concerned, the retard of the fuel injection timing
using the processing of step 110 or 112 and the control of the fuel
injection amount in steps 200 to 204 are executed. Such control can
also control the air-to-fuel ratio of the exhaust gas flowing into
the upstream catalyst 58 to a value leaner than the stoichiometric
air-to-fuel ratio while controlling the air-to-fuel ratio at the
time of combustion in the cylinder to the stoichiometric
air-to-fuel ratio, as in the above described control according to
the first embodiment. In other words, it can be said that when
taking the intake valve passing-through air amount as a reference,
the manner of the present embodiment performs the increase in the
target air-to-fuel ratio at the time of detection of the blow-by of
fresh air.
[0083] The control of the present embodiment as described so far
can also achieve the prevention of the blow-by of unburned fuel to
the exhaust passage 18 and the prevention of discharge of the
unburned fuel from the cylinder. This makes it possible to prevent
oxygen trapped (stored) in the upstream catalyst 58 from bringing
about an oxygen reaction with unburned fuel inside the upstream
catalyst 58, and to thereby prevent the temperature of the upstream
catalyst 58 from rapidly rising. In addition, according to the
control of the present embodiment, the air-to-fuel ratio defined
using the in-cylinder charged air amount can be maintained at the
stoichiometric air-to-fuel ratio even when such increase in the
target air-to-fuel ratio is being performed, as in the control
according to the first embodiment. Therefore, the control can
prevent the deterioration of the upstream catalyst 58 from being
facilitated while ensuring an increase in the torque of the
internal combustion engine 10 by use of the scavenging effect.
[0084] Meanwhile, in the second embodiment, which has been
described above, the air-to-fuel ratio feedback control is
suspended and the fuel injection amount is set so that the
air-to-fuel ratio defined using the in-cylinder charged air amount
coincides with the stoichiometric air-to-fuel ratio, in order to
increase the target air-to-fuel ratio at the time of detection of
the blow-by of fresh air. However, the fuel injection amount
control in the present invention is not limited to the above
described manner. More specifically, at the time of detection of
the blow-by of fresh air, for example, the air-to-fuel ratio
feedback control may be suspended and the fuel injection amount may
be set so that the air-to-fuel ratio defined using the intake valve
passing-through air amount becomes a value leaner than the
stoichiometric air-to-fuel ratio.
[0085] In the second embodiment, which has been described above,
the ECU 80 executes the main feedback control described in the
first embodiment, whereby the "air-to-fuel ratio feedback
controlling means" according to the present invention is realized;
the ECU 80 executes the aforementioned processing of step 200,
whereby the "air-to-fuel ratio feedback suspend means" according to
the present invention is realized; and the ECU 80 executes the
aforementioned processing of step 202, whereby the "in-cylinder air
amount obtaining means" according to the present invention is
realized.
Third Embodiment
[0086] Next, a third embodiment of the present invention will be
described with reference to FIG. 6,
[0087] The system of the present embodiment can be implemented by
using the hardware configuration shown in FIG. 1 and causing the
ECU 80 to execute the routine shown in FIG. 6 described below,
instead of the routine shown in FIG. 4.
[0088] Meanwhile, in the first and second embodiments, which have
been described above, the retard of the fuel injection timing and
the increase in the target air-to-fuel ratio are executed when the
blow-by of fresh air (scavenging effect) is detected. In contrast,
in the present embodiment, the following control is executed prior
to the retard of the fuel injection timing and the increase in the
target air-to-fuel ratio when the blow-by of fresh air is
detected.
[0089] More specifically, in the present embodiment, when the
blow-by of fresh air is detected, by adjusting the O/L amount on
the basis of the output of the A/F sensor 64, the amount of the
blow-by of fresh air (the scavenging amount) is adjusted so as not
to be excessively scavenged. On this occasion, the present
embodiment is characterized by executing the adjustment of the
opening and closing timings of the exhaust valve 48 in priority to
(ahead of) the adjustment of the opening and closing timings of the
intake valve 44. Further, if the adjustment margin of the opening
and closing timings of the exhaust valve 48 has been run out, the
adjustment of the opening and closing timings of the intake valve
44 is executed. On that basis, if the adjustment of the amount of
the blow-by of fresh air is not sufficient even though the
adjustment margin of the opening and closing timings of the intake
valve 44 has been subsequently run out, the retard of the fuel
injection timing and the increase in the target air-to-fuel ratio
that are explained in the first and second embodiments are
executed.
[0090] FIG. 6 is a flowchart that represents a control routine
executed by the ECU 80 to implement the control according to the
third embodiment of the present invention. In FIG. 6, the same
steps as the steps shown in FIG. 4 in the first embodiment will be
assigned with the same reference numerals, and the description
thereof will be omitted or simplified. In addition, although
description is herein made taking as an example a control routine
that is combined with the control of the first embodiment (step
114), instead of that, a control routine that is combined with the
control of the second embodiment (steps 200 to 204) may be
used.
[0091] In the routine shown in FIG. 6, when the determination of
step 104 is affirmative, that is to say, when an occurrence of the
blow-by of fresh air is detected, it is determined whether or not
the present advance angle value of the opening and closing timings
of the exhaust valve 48 (EX-VVT) is the most advanced angle value
by use of the exhaust earn angle sensor 56 (step 300).
[0092] If, as a result, it is determined in step 300 that the
advance angle value of the opening and closing timings of the
exhaust valve 48 has not yet reached the most advanced angle value,
the advance of the opening and closing timings of the exhaust valve
48 is executed (step 302). As the amount of the blow-by of fresh
air increases, the air-to-fuel ratio of the exhaust gas that flows
into the upstream catalyst 58 is largely increased. If the
atmosphere of the upstream catalyst 58 is disturbed, due to such
increase in the air-to-fuel ratio, so as to be deviated from the
atmosphere of the stoichiometric air-to-fuel ratio, the purifying
performance of the upstream catalyst 58 is impaired. Accordingly,
in present step 302, the advance of the opening and closing timings
of the exhaust valve 48 is executed on the basis of the output of
the ALF sensor 64 so that the amount of the blow-by of fresh air is
obtained in which the air-to-fuel ratio of the exhaust gas flowing
into the upstream catalyst 58 is equal to or lower than a value
obtained by adding the aforementioned predetermined value a to the
stoichiometric air-to-fuel ratio.
[0093] If, on the other hand, it is determined in step 300 that the
advance angle value of the opening and closing timings of the
exhaust valve 48 has reached the most advanced angle value, next,
it is determined whether or not the present retard angle value of
the opening and closing timings of the intake valve 44 (IN-VVT) is
the most retarded angle value by use of the intake cam angle sensor
54 (step 304). If, as a result, it is determined that the retard
angle value of the opening and closing timings of the intake valve
44 has not yet reached the most retarded angle value, the retard of
the opening and closing timings of the intake valve 44 is executed
(step 306). Specifically, in present step 306, the retard of the
opening and closing timings of the intake valve 44 is executed on
the basis of the output of the A/F sensor 64 so that the amount of
the blow-by of fresh air is obtained in which the air-to-fuel ratio
of the exhaust gas flowing into the upstream catalyst 58 is equal
to or lower than a value obtained by adding the aforementioned
predetermined value a to the stoichiometric air-to-fuel ratio.
[0094] If, on the other hand, it is determined in step 306 that the
retard angle value of the opening and closing timings of the intake
valve 44 has reached the most retarded angle value, that is to say,
if the large dilution of the exhaust gas flowing into the upstream
catalyst 58 is not fully eliminated even though the advance of the
opening and closing timings of the exhaust valve 48 and the retard
of the opening and closing timings of the intake valve 44 have been
executed, next, the processing of step 106 and the subsequent steps
in the routine shown in FIG. 4 are executed.
[0095] According to the routine shown in FIG. 6 described so far,
the following effects can be produced as well as the effects
described in the first embodiment. More specifically, the intake
variable valve operating mechanism 46 is a mechanism that is
capable of changing the opening timing and the closing timing of
the intake valve 44 without changing the relation therebetween
(that is, operating angle). Because of this, A change in the
opening timing of the intake valve 44 for the adjustment of the O/L
amount is accompanied by a change in the closing timing of the
intake valve 44. If the closing timing of the intake valve 44 is
changed, the actual compression ratio of the internal combustion
engine 10 changes and ease of occurrence of knock changes. In
contrast, such change does not occur to the adjustment of the Oil,
amount using the adjustment of the opening and closing timings of
the exhaust valve 48. Thus, the present embodiment, which executes
the adjustment of the opening and closing timings of the exhaust
valve 48 in priority to (ahead of) the adjustment of the opening
and closing timings of the intake valve 44 when adjusting the O/L
amount to adjust the amount of the blow-by of fresh air, can
prevent the fluctuation of the air-to-fuel ratio (the large
dilution) of the exhaust gas due to the blow-by fresh air while
preventing knock resistance from being impaired as much as
possible.
[0096] In the third embodiment, which has been described above, the
ECU 80 executes the aforementioned processing of steps 300 to 306,
whereby the "overlap period adjusting means" according to the
present invention is realized.
[0097] Meanwhile, in the first to third embodiments, which have
been described above, in order to adjust the O/L period, the
variable valve operating mechanisms 46 and 50 that are capable of
continuously changing the opening and closing timings of the intake
valve 44 and the exhaust valve, respectively, while fixing those
operating angles. However, in relation to the controls explained in
the first and second embodiments, the O/L, period is not
necessarily limited to one that is variable, and may be fixed at a
value at which the blow-by of fresh air can occur depending on the
operating condition. In addition, in relation to the controls
explained in the first and second embodiments, a mechanism that is
capable of changing only the opening timing of the intake valve 44
for the adjustment of the O/L period may be used. On the other
hand, as for the exhaust valve 48, in relation to the control
explained in any of the first to third embodiments, a mechanism
that is capable of changing only the closing timing of the exhaust
valve 48 for the adjustment of the O/L period may be used.
[0098] Moreover, in the first to third embodiments, description has
been made taking as an example the internal combustion engine 10
that includes both of the port injection valve 38 and the
in-cylinder injection valve 40. However, an internal combustion
engine in the present invention is not limited to one having the
aforementioned configuration, and may be one that only includes any
one of a fuel injection valve capable of injecting fuel into an
intake passage (for example, port injection valve) and an
in-cylinder injection valve capable of directly injecting fuel into
a cylinder.
[0099] Moreover, in the first to third embodiments, description has
been made taking as an example the internal combustion engine 10
that includes the turbo-supercharger 24. However, a supercharger
included in an internal combustion engine in the present invention
is not limited to one having the aforementioned configuration, and
may, for example, be one that uses the power from a crankshaft of
an internal combustion engine or one that uses an
electrically-driven motor.
DESCRIPTION OF SYMBOLS
[0100] 10 internal combustion engine [0101] 12 piston [0102] 14
combustion chamber [0103] 16 intake passage [0104] 18 exhaust
passage [0105] 22 air flow meter [0106] 24 turbo-supercharger
[0107] 24a compressor of turbo-supercharger [0108] 24b turbine of
turbo-supercharger [0109] 32 throttle valve [0110] 34 throttle
upstream pressure sensor [0111] 36 throttle downstream pressure
sensor [0112] 38 port injection valve [0113] 40 in-cylinder
injection valve [0114] 42 spark plug [0115] 44 intake valve [0116]
46 intake variable valve operating mechanism [0117] 48 exhaust
valve [0118] 50 exhaust variable valve operating mechanism [0119]
52 crankshaft [0120] 54 intake cam angle sensor [0121] 56 exhaust
can angle sensor [0122] 58 upstream catalyst [0123] 60 downstream
catalyst [0124] 64 A/F sensor [0125] 66 O.sub.2 sensor [0126] 76
crank angle sensor [0127] 80 ECU (Electronic Control Unit)
* * * * *