Title: Fuel injection control device for internal combustion engine
Abstract: An internal combustion engine (10) is provided with a port injector (28) and an in-cylinder injector (22). Before a port injection is started, the total amount of fuel to be injected is calculated (at an injection amount calculation timing). The port injection fuel amount and the in-cylinder injection fuel amount are calculated by appropriately dividing the total amount between them. If a change of the operating load on the internal combustion engine (10) is detected after the injection amount calculation timing, the load change is reflected in the amount of fuel to be injected in the current engine cycle by increasing or decreasing the in-cylinder injection fuel amount.
Patent Number: 6,988,485 Issued on 01/24/2006 to Ichise, et al.
| Inventors:
|
Ichise; Masaharu (Susono, JP);
Kashiwagura; Toshimi (Susono, JP);
Nogawa; Shinichiro (Mishima, JP);
Hashima; Takashi (Gotenba, JP)
|
| Assignee:
|
Toyota Jidosha Kabushiki Kaisha (Toyota, JP)
|
| Appl. No.:
|
026038 |
| Filed:
|
January 3, 2005 |
Foreign Application Priority Data
| Jan 16, 2004[JP] | 2004-009781 |
| Current U.S. Class: |
123/430; 123/431 |
| Current Intern'l Class: |
F02B 17/00 (20060101) |
| Field of Search: |
123/430,431
|
References Cited [Referenced By]
U.S. Patent Documents
| 5875743 | Mar., 1999 | Dickey.
| |
| 6341487 | Jan., 2002 | Takahashi et al.
| |
| 2002/0040692 | Apr., 2002 | LaPointe et al.
| |
| 2003/0159434 | Aug., 2003 | Ikemoto et al.
| |
| 2003/0221661 | Dec., 2003 | Willi et al.
| |
| 2005/0109320 | May., 2005 | Mashiki.
| |
| 2005/0178360 | Aug., 2005 | Satou.
| |
| Foreign Patent Documents |
| 1 258 622 | Nov., 2002 | EP.
| |
| A 5-231221 | Sep., 1993 | JP.
| |
| A 11-1822/83 | Jul., 1999 | JP.
| |
| A 11-3036/69 | Nov., 1999 | JP.
| |
| A 2003-13784 | Jan., 2003 | JP.
| |
Primary Examiner: Kwon; John T.
Attorney, Agent or Firm: Oliff & Berridge, PLC
Claims
What is claimed is:
1. A fuel injection control device for an internal combustion engine, comprising:
operating load detecting means for detecting an operating load on the internal
combustion engine;
a port injector for port injection;
an in-cylinder injector for in-cylinder injection;
fuel amount calculating means for calculating a port injection amount of fuel
to be injected from the port injector and a reference in-cylinder injection amount
of fuel to be injected from the in-cylinder injector at a predetermined injection
amount calculation timing based on the operating load;
port injection control means which starts a port injection before an in-cylinder
injection so as to inject said port injection amount of fuel from the port injector;
correction fuel amount calculation means which calculates a fuel correction amount
for a change of the operating load on the internal combustion engine if the change
is detected after the injection amount calculation timing and before a reflection
limit timing until which the amount of fuel to be injected from the in-cylinder
injector; and
in-cylinder injection control means which executes the in-cylinder injection
after the port injection so as to inject an amount of fuel from the in-cylinder
injector wherein the amount of fuel is determined based on the reference in-cylinder
injection amount and the correction amount.
2. A fuel injection control device for an internal combustion engine according
to claim 1, wherein
the in-cylinder injection control means includes normal in-cylinder injection
means which starts a normal in-cylinder injection at a predetermined timing so
as to inject the reference in-cylinder injection amount of fuel if a non-zero value
is calculated as the reference in-cylinder injection amount; and
the correction fuel amount calculation means includes normal in-cylinder injection
amount correcting means which increases or decreases the amount of fuel to be injected
by the normal in-cylinder injection by the correction amount of fuel corresponding
to a change of the operating load on the internal combustion engine if the change
is detected before a limit timing until which the amount of fuel to be injected
by the normal in-cylinder injection is changed.
3. A fuel injection control device for an internal combustion engine according
to claim 1, wherein
the in-cylinder injection control means includes normal in-cylinder injection
means which starts a normal in-cylinder injection at a predetermined timing so
as to inject the reference in-cylinder injection amount of fuel if a non-zero value
is calculated as the reference in-cylinder injection amount; and
the correction fuel amount calculation means includes in-cylinder injection amount
increasing means which executes an additional in-cylinder injection so as to inject
the correcting amount of fuel corresponding to an increase of the operating load
on the internal combustion engine if the increase is detected after a limit timing
until which the amount of fuel to be injected by the normal in-cylinder injection
is changed.
4. A fuel injection control device for an internal combustion engine according
to claim 1, wherein the in-cylinder injection control means includes additional
in-cylinder injection means which executes an in-cylinder injection after the port
injection so as to inject the correcting amount of fuel corresponding to an increase
of the operating load on the internal combustion engine if the increase is detected
after zero is calculated as the reference in-cylinder injection amount.
5. A fuel injection control device for an internal combustion engine according
to claim 1, wherein the fuel amount calculating means includes:
port fuel deviation estimating means which estimates a deviation of the amount
of fuel which actually enters a cylinder from an intake port from an ideal amount
of fuel which should enters the cylinder from the intake port, based on the change
of the load on the internal combustion engine; and
reference amount correcting means which increases or decreases the reference
in-cylinder injection amount so as to compensate for the deviation.
6. A fuel injection control device for an internal combustion engine, comprising:
an operating load detecting unit for detecting an operating load on the internal
combustion engine;
a port injector for port injection;
an in-cylinder injector for in-cylinder injection;
a fuel amount calculating unit for calculating a port injection amount of fuel
to be injected from the port injector and a reference in-cylinder injection amount
of fuel to be injected from the in-cylinder injector at a predetermined injection
amount calculation timing based on the operating load;
a port injection control unit which starts a port injection before an in-cylinder
injection so as to inject said port injection amount of fuel from the port injector;
a correction fuel amount calculation unit which calculates a fuel correction
amount for a change of the operating load on the internal combustion engine if
the change is detected after the injection amount calculation timing and before
a reflection limit timing until which the amount of fuel to be injected from the
in-cylinder injector; and
an in-cylinder injection control unit which executes the in-cylinder injection
after the port injection so as to inject an amount of fuel from the in-cylinder
injector wherein the amount of fuel is determined based on the reference in-cylinder
injection amount and the correction amount.
7. A fuel injection control device for an internal combustion engine according
to claim 6, wherein
the in-cylinder injection control unit includes a normal in-cylinder injection
unit which starts a normal in-cylinder injection at a predetermined timing so as
to inject the reference in-cylinder injection amount of fuel if a non-zero value
is calculated as the reference in-cylinder injection amount; and
the correction fuel amount calculation unit includes a normal in-cylinder injection
amount correcting unit which increases or decreases the amount of fuel to be injected
by the normal in-cylinder injection by the correction amount of fuel corresponding
to a change of the operating load on the internal combustion engine if the change
is detected before a limit timing until which the amount of fuel to be injected
by the normal in-cylinder injection is changed.
8. A fuel injection control device for an internal combustion engine according
to claim 6, wherein
the in-cylinder injection control unit includes a normal in-cylinder injection
unit which starts a normal in-cylinder injection at a predetermined timing so as
to inject the reference in-cylinder injection amount of fuel if a non-zero value
is calculated as the reference in-cylinder injection amount; and
the correction fuel amount calculation unit includes an in-cylinder injection
amount increasing unit which executes an additional in-cylinder injection so as
to inject the correcting amount of fuel corresponding to an increase of the operating
load on the internal combustion engine if the increase is detected after a limit
timing until which the amount of fuel to be injected by the normal in-cylinder
injection is changed.
9. A fuel injection control device for an internal combustion engine according
to claim 6, wherein the in-cylinder injection control unit includes an additional
in-cylinder injection unit which executes an in-cylinder injection after the port
injection so as to inject the correcting amount of fuel corresponding to an increase
of the operating load on the internal combustion engine if the increase is detected
after zero is calculated as the reference in-cylinder injection amount.
10. A fuel injection control device for an internal combustion engine according
to claim 6, wherein the fuel amount calculating unit includes:
a port fuel deviation estimating unit which estimates a deviation of the amount
of fuel which actually enters a cylinder from an intake port from an ideal amount
of fuel which should enters the cylinder from the intake port, based on the change
of the load on the internal combustion engine; and
a reference amount correcting unit which increases or decreases the reference
in-cylinder injection amount so as to compensate for the deviation.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel injection control device for an internal
combustion engine and, more particularly, to a fuel injection control device for
an internal combustion engine which is provided with a port injector to inject
fuel into the intake port and an in-cylinder injector to inject fuel into the cylinder.
2. Background Art
As conventional internal combustion engines, those comprising a port injector
to inject fuel into the intake port and an in-cylinder injector to inject fuel
into the cylinder are known as disclosed in, for example, Japanese Patent Laid-open
No. 2003-13784. In such a prior art internal combustion engine operating under
certain conditions, port injection by a port injector is combined with in-cylinder
injection by an in-cylinder injector so as to form a fuel-rich layer near the spark
plug while introducing uniform mixture into the cylinder. According to this fuel
injection technique, it is possible to keep lean the air-fuel ratio of the mixture
while producing stable combustion in the cylinder. Hereinafter, such an internal
combustion engine is denoted as a "dual-injector type internal combustion engine".
In a dual-injector type internal combustion engine which concurrently performs
both port injection and in-cylinder injection, the injection ratio between them
must be controlled to an appropriate value. Conventionally, such an internal combustion
engine therefore determines both the port injection fuel amount and the in-cylinder
injection fuel amount at a predetermined injection amount calculation timing just
before port injection is started. Then, the internal combustion engine successively
drives the port injector and the in-cylinder injector so as to implement port and
in-cylinder fuel injections of the determined respective amounts. According to
this control technique, fuel can be injected into the intake port and the cylinder
at an appropriate ratio, allowing stable combustion with a lean air-fuel mixture.
Including the above-mentioned document, the applicant is aware of the following
documents as a related art of the present invention.
[Patent Document 1] Japanese Patent Laid-open No. 2003-13784
[Patent Document 2] Japanese Patent Laid-open No. 11-182283
[Patent Document 3] Japanese Patent Laid-open No. 5-231221
[Patent Document 4] Japanese Patent Laid-open No. 11-303669
In the above-mentioned prior art internal combustion engine, however, the port
injection fuel amount and the cylinder injection fuel amount are calculated only
once per engine cycle just before port injection is started. Therefore, if the
load on the internal combustion engine changes or the change is detected after
the calculation, the load change is not reflected in the fuel injection amount
until the next engine cycle. More specifically, in the above-mentioned prior art
internal combustion engine, any change in the load (intake air flow) during actual
air intake, which may occur after the fuel injection amount is calculated and just
before the port injection (intake stroke) is started, is not reflected in the fuel
injection amount.
If the load change is not reflected in the fuel injection amount, no large change
occurs in the torque of the internal combustion engine. This means that the conventional
dual-injector type internal combustion engines leave room for improvement in terms
of response to load changes.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above-mentioned problem. It
is an object of the present invention to provide a fuel injection control device
which enables an internal combustion engine to make excellent responses to load changes.
The above object is achieved by a fuel injection control device for an internal
combustion engine. The control device includes an operating load detecting unit
for detecting an operating load on the internal combustion engine. A port injector
is provided for port injection. An in-cylinder injector is provided for in-cylinder
injection. The control device also includes a fuel amount calculating unit for
calculating a port injection amount of fuel to be injected from the port injector
and a reference in-cylinder injection amount of fuel to be injected from the in-cylinder
injector at a predetermined injection amount calculation timing based on the operating
load. The control device further includes a port injection control unit which starts
a port injection before an in-cylinder injection so as to inject said port injection
amount of fuel from the port injector. There is also provided a correction fuel
amount calculation unit which calculates a fuel correction amount for a change
of the operating load on the internal combustion engine if the change is detected
after the injection amount calculation timing and before a reflection limit timing
until which the amount of fuel to be injected from the in-cylinder injector. There
is further provided an in-cylinder injection control unit which executes the in-cylinder
injection after the port injection so as to inject an amount of fuel from the in-cylinder
injector wherein the amount of fuel is determined based on the reference in-cylinder
injection amount and the correction amount.
Other objects and further features of the present invention will be apparent
from the following detailed description when read in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a diagram for explaining the configuration of a first embodiment of
the present invention;
FIGS. 2A to 2D are diagrams for explaining the fuel injection patterns used
in the first embodiment of the present invention;
FIG. 3 is a flowchart of an injection amount calculation routine which is executed
in the first embodiment of the present invention;
FIG. 4 is a flowchart of a fuel injection routine which is executed in the first
embodiment of the present invention;
FIGS. 5A to 5C are timing charts for explaining how the cylinder injection
fuel amount is calculated in a second embodiment of the present invention; and
FIG. 6 is a flowchart for explaining a processing sequence which is executed
in the second embodiment of the present invention in place of step 106 in
FIG. 3.
BEST MODE FOR CARRYING OUT THE INVENTION
First Embodiment
[System Configuration of First Embodiment]
FIG. 1 is provided to explain the configuration of a first embodiment of the
present invention. As shown in FIG. 1, this system embodiment has an internal combustion
engine
10. The internal combustion engine
10 is communicated with
an intake port
12 and an exhaust port
14. An intake valve
16
is provided between the intake port
12 and the in-cylinder space of the
internal combustion engine
10. An exhaust valve
18 is provided between
the exhaust port
14 and the in-cylinder space of the internal combustion
engine
10.
In addition, a spark plug
20 and an in-cylinder injector (DInj)
22
for direct injection into the cylinder are set to the internal combustion engine
10. The tip of the spark plug
20 is exposed in the middle of the
in-cylinder space. The tip of the in-cylinder injector
22 is directed toward
the center of the in-cylinder space. The piston
24 of the internal combustion
engine
10 has a cavity
26 formed on its top surface. Fuel, injected
from the in-cylinder injector
22 at a predetermined timing, is reflected
by the wall of the cavity
26 to form a gas layer near the tip of the spark.
Thus, the in-cylinder injector
22 generates a rich mixture only near the
spark plug
20, making it possible to secure stable operation with a smaller
amount of fuel, that is, realize what is called stratified operation.
A port injector
28 is set to the intake port
12. The port injector
28 can inject fuel into the intake port
12. Injecting fuel into the
intake port
12 makes it possible to introduce a uniformly concentrated mixture
into the cylinder. By combining port fuel injection through the port injector
28
with in-cylinder fuel injection through the in-cylinder injector
22 in a
specific operating region, the system of this embodiment can realize stable operation
with less fuel.
A throttle valve
30 is provided upstream of the intake port
12.
The
amount Ga of air which is taken into the internal combustion engine
10 increases
or decreases depending on the opening degree of the throttle valve
30. Since
the throttle valve
30 acts in conjunction with an accelerator pedal
32,
the air intake amount Ga can be adjusted by operating the accelerator.
As shown in FIG. 1, the system of this embodiment is provided with an ECU (Electronic
Control Unit)
40. The ECU
40 is connected with a crank angle sensor
42, a revolution sensor
44, an air flow meter
46 and other
sensors. Based on the outputs of these sensors, the ECU
40 can detect the
crank angle CA, revolution speed NE, intake air amount Ga of the internal combustion
engine
10 and the like. The ECU
40 is also connected with the above-mentioned
in-cylinder injector
22 and port injector
28. Based on the operating
condition of the internal combustion engine
10, detected through the various
sensors, the ECU
40 can drive these injectors
22 and
28 so
as to make appropriate the port injection fuel amount and the in-cylinder injection
fuel amount.
[Fuel Injection Patterns in First Embodiment]
In the system of this embodiment, fuel injection is selected from dual fuel injection
performing both port injection and in-cylinder injection (denoted as "port-in-cylinder
injection"), port-only fuel injection, etc. according to the operating condition
of the internal combustion engine
10. Referring to FIG. 2, the following
describes the fuel injection patterns used in this system embodiment.
FIG. 2A is provided to explain an injection pattern which occurs when port-in-cylinder
injection is requested at the injection amount calculation timing, then a change
of the operating load (namely, the intake air amount Ga) on the internal combustion
engine
10 is detected during the port injection period. In FIG. 2A, the
point "Injection Amount Calculation Timing" is a point of time at which the port
injection fuel amount and the in-cylinder injection fuel amount are calculated
for the internal combustion engine
10.
In this embodiment, the injection amount calculation timing differs depending
on each cylinder. The injection amount calculation timing for a cylinder is a predetermined
point of time which immediately precede the start of the combustion/expansion stroke.
At the point of time, the ECU
40 calculates a fuel injection amount depending
on the operating condition of the internal combustion engine
10 and, further,
calculates a port injection fuel amount and a in-cylinder injection fuel amount
so as to divide the calculated fuel injection amount between port injection and
in-cylinder injection according to a predetermined rule. Hereinafter, the in-cylinder
injection fuel amount calculated at this timing is specially referred to as the
"reference in-cylinder injection fuel amount".
In a port-only injection region, zero is obtained as the reference in-cylinder
injection fuel amount. In FIG. 2A, since the example is a pattern for the region
in which port-in-cylinder injection should be done, a non-zero value is obtained
at the injection amount calculation timing as the reference in-cylinder injection
fuel amount.
In the system of this embodiment, the port injection period is defined such that
it roughly agrees with the period during which the combustion/expansion stroke
and exhaust stroke are done (the 360 CA° period from the top dead center of
compression to the top dead center of exhaust) as shown in FIG. 2A. Depending on
the operating condition of the internal combustion engine
10, an appropriate
point of time is set in the port injection period by the ECU
40 as the port
injection time. At this port injection time, the amount of fuel calculated as mentioned
above is injected from the port injector
28.
In the system of this embodiment, the normal cylinder injection period is defined
such that it roughly agrees with the period during which the intake stroke is done
(the 180 CA° period from the top dead center of exhaust to the bottom dead
center of intake). Depending on the operating condition of the internal combustion
engine
10, an appropriate point of time is set in the normal in-cylinder
injection period by the ECU
40 as the normal in-cylinder injection time.
At this normal in-cylinder injection time, the in-cylinder injector
22 begins
to inject the reference in-cylinder injection amount of fuel calculated as mentioned above.
Even after the injection amount calculation timing, the ECU
40 can correct
the amount of fuel to be injected by the normal in-cylinder injection until the
normal in-cylinder injection is started. Hereinafter, the deadline for this correction
is referred to as the "limit timing". In the example of FIG. 2A, since a load change
is detected earlier than the limit timing, the amount of fuel to be injected by
the normal in-cylinder injection can be corrected according to the load change.
Performing such a correction improves the response of the internal combustion engine
10 and makes its air-fuel ratio control more accurate since a load change
which occurs after the injection fuel amount calculation timing can be reflected
in the total amount of fuel to be injected in the current engine cycle.
As shown in FIG. 2A, therefore, if the operating load on the internal combustion
engine
10 changes between the injection fuel calculation timing and the
limit timing in this system embodiment, a positive or negative correction is given
to the reference in-cylinder injection fuel amount in accordance with the load
change. The "Injection Amount Increase/Decrease Correction" in FIG. 2A indicates
an instance of this correction timing. Since correction is made in this manner,
the system of this embodiment can show excellent response to load changes which
may occur between the injection fuel calculation timing and the limit timing while
keeping high the air-fuel ratio control accuracy.
The total fuel injection amount determined at the injection amount calculation
timing can therefore be either increased or decreased by correcting the amount
of fuel to be injected by the normal in-cylinder injection. According to the injection
pattern shown in FIG. 2A, even if the operating load changes after the injection
amount calculation timing, it is possible to inject an appropriate amount of fuel
according to the load change in the current engine cycle regardless of whether
the load change is increases or decrease. The injection pattern shown in FIG. 2A
is effective for both increase and decrease in the load.
FIG. 2B is provided to explain an injection pattern which occurs when port-in-cylinder
injection is requested at the injection amount calculation timing and then an increase
of the operating load on the internal combustion engine
10 is detected after
the normal in-cylinder injection is started (after the limit timing). In this case,
since the change of the load on the internal combustion engine
10 is detected
later than the limit timing, this change cannot be reflected in the amount of fuel
to be injected by the normal in-cylinder injection.
However, since the normal in-cylinder injection terminates during the intake
stroke, there remains some time which may allow re-execution of an in-cylinder
injection. If in-cylinder injection is re-executed by using this time, the total
amount of fuel to be injected in the current engine cycle, determined at the injection
amount calculation timing, can be given a positive correction.
That is, even if the load on the internal combustion engine
10 changes
later than the limit timing, as long as the change is detected at a time from which
another in-cylinder injection can be completed before the ignition, although it
is not possible to correct the total fuel injection amount to a lower amount in
the current engine cycle, it is possible to correct the total fuel injection amount
to a higher amount. Hereinafter, the deadline for executing another in-cylinder
injection is referred to as the "reflection limit timing".
Therefore, if a change or, more specifically, an increase in the load
on the internal combustion engine is detected between the limit timing and the
reflection limit timing, the system of this embodiment executes another fuel injection
so as to correct the injection fuel amount according to the increase of the load.
Hereinafter, "additional in-cylinder injection" is used to refer to such an in-cylinder
injection, namely, an in-cylinder injection that is done in order to correct the
fuel injection amount in accordance with a load increase that occurs after the
injection amount calculation timing.
In the example shown in FIG. 2B, port-in-cylinder injection is requested at the
injection amount calculation timing and then a load increase is detected during
the intake stroke. In this case, since the load increase is detected earlier than
the reference limit timing, the ECU
40 can perform an additional in-cylinder
injection. The "Injection Amount Increase Correction" in FIG. 2B indicates a timing
at which the amount of fuel to be injected for correction by the additional in-cylinder
injection is set, that is, the amount of fuel corresponding to the load increase
is set for correction.
Further, in an engine cycle which requires port-in-cylinder injection, a
certain period during the compression stroke is defined as the "additional in-cylinder
injection period" as shown in FIG. 2B. Depending on the operating condition of
the internal combustion engine
10, an appropriate point of time is set in
the additional in-cylinder injection period by the ECU
40 as the additional
in-cylinder injection time. At this additional in-cylinder injection time, the
additional in-cylinder injection is performed to inject the previously set amount
of fuel. According to the procedure described so far, if the load on the internal
combustion engine
10 increases between the limit timing and the reflection
limit timing, the load increase can be reflected in the total amount of fuel to
be injected in the current engine cycle. Thus, the injection pattern shown in FIG.
2B makes it possible to realize excellent response to such load increases while
keeping highly accurate air-fuel ratio control.
FIG. 2C is provided to explain an injection pattern which occurs if port-only
injection is requested at the injection amount calculation timing and then an increase
of the operating load on the internal combustion engine
10 is detected during
the port injection period. If the load on the internal combustion engine
10
is detected as changed at such a timing, its change cannot be reflected in the
port injection fuel amount. However, if the load change is an increase, it is possible
to correct the fuel amount in accordance with the load increase by performing an
additional in-cylinder injection after the port injection.
"Injection Amount Increase Correction" in FIG. 2C indicates a timing at
which the amount of fuel to be injected for correction in accordance with the detected
load increase is set. "Additional Cylinder Injection Period" also in FIG. 2C is
substantially identical to the normal in-cylinder injection period shown in FIG.
2A. That is, if port-only injection is requested at the injection amount calculation
timing and then a load increase is detected earlier than the above-mentioned limit
timing, the system of this embodiment sets an additional in-cylinder injection
period which is identical to the normal in-cylinder injection period shown in FIG.
2A. Then, according to the operating condition of the internal combustion engine
10, the ECU
40 sets an appropriate point of time in the additional
in-cylinder injection period as the additional in-cylinder injection time and performs
the additional in-cylinder injection at the additional in-cylinder injection time.
According to the above-mentioned procedure, if only port injection is requested
at the injection amount calculation timing and then a load increase is detected
earlier than the limit timing, execution of a port injection can be followed by
an in-cylinder injection as if port-in-cylinder injection was requested. Thus,
the injection pattern shown in FIG. 2C makes it possible to realize excellent response
and excellent air-fuel ratio control accuracy in a case where load increase occurs
under such conditions that port-only injection is requested.
FIG. 2D is provided to explain an injection pattern which occurs if port-only
injection is requested at the injection amount calculation timing and then an increase
of the operating load on the internal combustion engine
10 is detected during
the intake stroke, that is, the load increase is detected later than a timing at
which a normal in-cylinder injection should be started. In this case, immediately
after the load change (increase) is detected, "Injection Amount Increase Correction"
is performed as shown in FIG. 2D, that is, the amount of fuel for correction in
accordance with the load increase is set.
Further in this case, a period which continues until just before the reflection
limit timing is set as "Additional Cylinder Injection Period" after "Injection
Amount Increase Correction" is done. Then, according to the operating condition
of the internal combustion engine
10, the ECU
40 sets an appropriate
point of time in the additional in-cylinder injection period as the additional
in-cylinder injection time and performs the additional in-cylinder injection at
the additional in-cylinder injection time.
According to the above-mentioned procedure, if port-only injection is requested
at the injection amount calculation timing and then a load increase is detected
earlier than the reflection limit timing, an in-cylinder injection can make up
the fuel shortfall left by the port injection. Thus, similar to the injection pattern
shown in FIG. 2C, this injection pattern in FIG. 2D makes it possible to realize
excellent response and excellent air-fuel ratio control accuracy in a case where
load increase occurs under such conditions that port-only injection is requested.
[Practical Processing in First Embodiment]
The ECU
40 implements the aforementioned fuel injection patterns by executing
the routines shown in FIGS. 3 and 4. The following will describe the details of
these routines step by step. FIG. 3 is a flowchart of an injection amount calculation
routine which is executed by the ECU
40 in order to calculate the amount
of fuel to be injected by the port injection, the amount of fuel to be injected
by the normal in-cylinder injection and the amount of fuel to be injected by the
additional in-cylinder injection.
The routine shown in FIG. 3 is activated periodically, for example, every 1 msec.
If this routine is activated, the operating condition of the internal combustion
engine
10, namely the engine revolution speed NE and the engine load are
detected at first based on the individual sensor outputs (step
100). Then,
the location of the current timing in the current cycle of the internal combustion
engine
10 is detected. Specifically, the current crank angle CA of the internal
combustion engine
10 is detected (step
102).
Then, based on the detected crank angle CA, it is judged whether the current
timing is earlier than the injection amount calculation timing (step
104).
The crank angle which corresponds to the deadline for performing an additional
in-cylinder injection, namely the reflection limit timing, is stored in the ECU
40. The crank angle which corresponds to the injection amount calculation
timing is also stored in the ECU
40. By comparing these crank angles with
the current crank angle, this step
104 judges whether the current timing
is later than the reflection limit timing but earlier than the injection amount
calculation timing. If the condition is true, the judgment result is "Before Injection
Amount Calculation Timing".
If the judgment result in the above-mentioned step
104 is "Before Injection
Amount Calculation Timing", a port injection fuel amount and an in-cylinder injection
fuel amount (reference in-cylinder injection fuel amount) which are appropriate
to the current operating condition are calculated (step
106). Upon completion
of this step
106 processing, this activated routine is immediately terminated.
If the above processing is repeated, the reference port injection fuel amount and
the reference in-cylinder injection fuel amount can be calculated as respective
values that are appropriate for the current operating condition at a timing of
injection amount calculation.
If the judgment result of the above-mentioned step
104 in the routine
of
FIG. 3 is not "Before Injection Amount Calculation Timing", it is judged whether
port-only injection was requested at the injection amount calculation timing (step
108). If the result is that the requested injection is not port-only injection,
it is recognized that the requested injection is port-in-cylinder injection. In
this case, it is judged whether the current timing is earlier than the limit timing
(step
110).
If the judgment result of the above-mentioned step
110 is "Before Limit
Timing", the change of the load on the internal combustion engine
10 can
be reflected in the amount of fuel to be injected by the normal in-cylinder injection.
In this case, it is judged at first whether the current load has increased from
the load which was detected at the injection amount calculation timing (step
112).
Practically, if the opening of the throttle shows a meaningful increase, this step
112 judges that the load has increased. If a load increase is recognized,
the amount of fuel to be injected by the normal in-cylinder injection is increased
for correction (step
114).
If any load increase is not recognized in the above-mentioned step
112,
it is judged whether the current load has decreased from the load detected at the
injection amount calculation timing (step
116). Practically, if the opening
of the throttle shows a meaningful decrease, this step
116 judges that the
load has increased. If a load decrease is recognized, the amount of fuel to be
injected by the normal in-cylinder injection is decreased for correction (step
118). If any load decrease is not recognized, this activated routine is
immediately terminated.
If it is judged in the above-mentioned step
108 that the injection requested
at the injection amount calculation timing is port-only injection and in the above-mentioned
step
110 that the current timing is already later than the limit timing,
it is judged whether an additional in-cylinder injection is necessary. Specifically,
it is judged whether the current load (opening degree of the throttle) shows a
meaningful increase from the load (opening degree of the throttle) detected at
the injection amount calculation timing (step
120).
If a load increase is recognized as the result of the above-mentioned judgment,
the amount of fuel to be injected by the additional in-cylinder injection for correction
is calculated (step
122). If no load increase is recognized in step
120,
performing an additional in-cylinder injection is judged to be not necessary. In
this case, this activated routine is terminated without doing any processing to
increase the amount of fuel to be injected.
According to the injection amount calculation routine described so far,
a port injection fuel amount and a reference in-cylinder injection fuel amount,
which are appropriate for the current operating condition, can be calculated at
the injection amount calculation timing. In addition, if a load change is detected
before the limit timing under such conditions that port-in-cylinder injection is
requested, the amount of fuel to be injected by the normal in-cylinder injection
can be increased or decreased for correction (refer to FIG. 2A). Likewise, if a
load increase is detected after the limit timing, the amount of fuel to be injected
by an additional in-cylinder injection can be calculated (refer to FIG. 2B). Further,
under such conditions that port-only injection is requested, corrected fuel injection
amount which matches to a load increase detected after the injection amount calculation
timing can be calculated as fuel amount to be injected by an additional in-cylinder
injection (refer to FIG. 2C and FIG. 2D).
FIG. 4 is a flowchart of a routine executed by the ECU
40 in order to
actually inject the amount of fuel, calculated by the routine of FIG. 3, through
port injection or in-cylinder injection. The routine shown in FIG. 4 is repeatedly
activated each time its processing completes. If this routine is activated, the
engine rotation speed NE and the engine load are detected at first based on the
individual sensor outputs (step
130).
Then, based on the engine rotation speed NE and the engine load, a port injection
time and a normal in-cylinder injection time are set (steps
132 and
134).
Then, based on the current crank angle CA, it is judged whether the port injection
time has come (step
136). If it is judged that the port injection time has
come, processing for port injection is executed (step
138). Practically,
the port injector
28 is driven so as to inject the amount of fuel calculated
by the routine of FIG. 3.
Then, it is judged whether normal in-cylinder injection is requested (step
140). In this step
140, it is judged that normal in-cylinder injection
is not requested if a non-zero value is set by the routine of FIG. 3 as the amount
of fuel to be injected by the normal in-cylinder injection, that is, a non-zero
value is calculated at the injection amount calculation timing as the reference
in-cylinder injection fuel amount (refer to the aforementioned step
106).
If it is judged in the above-mentioned step
140 that normal in-cylinder
injection is not requested, the routine jumps steps
142 and
144 described
below. Otherwise, it is judged based on the current crank angle whether the normal
in-cylinder injection time has come (step
142).
If the judgment result is that the normal in-cylinder injection time has come,
processing is executed in order to inject a proper amount of fuel from the in-cylinder
injector
22 (step
144). Practically, the in-cylinder injector
22
is driven so as to inject the amount of fuel calculated last by the aforementioned
step
106,
114 or
118 of the routine shown in FIG. 3.
Then, in the routine shown in FIG. 4, it is judged whether additional in-cylinder
injection is requested (step
146). In this step
146, it is recognized
that additional in-cylinder injection is requested if an amount of fuel to be injected
by an additional in-cylinder injection was calculated by the step
122 processing
in the routine of FIG. 3.
If a request for additional in-cylinder injection is recognized, the in-cylinder
injector
22 is driven so as to inject the amount of fuel calculated by the
above-mentioned step
122 for correction (step
148). Meanwhile, if
it is judged that no request is recognized for additional in-cylinder injection,
it is judged based on the current crank angle whether the current timing is earlier
than the reflection limit timing (step
150).
If the current timing is judged to be earlier than the reflection limit timing,
the above-mentioned step
146 processing is executed again since there remains
the possibility that a request for additional in-cylinder injection may occur in
the current engine cycle. Then, if the reflection limit timing comes without a
request for additional in-cylinder injection, the step
150 produces a negative
judgment, terminating the this activated routine.
As described so far, according to the routine shown in FIG. 4, if execution of
a normal in-cylinder injection is requested, a port injection can be followed by
execution of a normal in-cylinder injection. According to the routine of FIG. 3,
when a normal in-cylinder injection is started, load change is reflected in the
amount of fuel to be injected by the normal in-cylinder injection. Thus, the system
of this embodiment can implement the injection pattern shown in FIG. 2A.
Moreover, according to the system of this embodiment, corrected fuel amount
that matches engine load increase is calculated at step
120 shown in FIG.
3, if the engine load increase is detected after the port injection and the normal
in-cylinder injection have done and before the reflection limit timing has come.
Then, if corrected fuel amount is calculated as described above, the additional
in-cylinder injection is executed for injecting the corrected fuel amount by the
routine shown in FIG. 4. Thus, the system of this embodiment can implement the
injection pattern shown in FIG. 2B.
Further, in the system of this embodiment, if port-only injection is requested
at the injection fuel amount calculation timing, the necessity of normal in-cylinder
injection is negated according to the routine shown in FIG. 4. Even in this case,
after the port injection, it is possible to immediately begin to judge whether
additional in-cylinder injection is necessary. If an engine load increase is detected
before the reflection limit timing, the amount of fuel corresponding to the increase
is calculated for correction by step
120 in FIG. 3. In this case, an additional
in-cylinder injection can be executed to inject the corrected fuel amount according
to the routine shown in FIG. 4. Thus, the system of this embodiment can implement
the injection patterns shown in FIGS. 2C and 2D.
As described so far, the system of this embodiment can selectively implement
an
appropriate injection pattern, any of those shown in FIG. 2A through FIG. 2D, according
to the request made at the injection amount calculation timing, and the timing
at which the load change is detected. Consequently, the system of this embodiment
can realize an internal combustion engine
10 capable of showing excellent
response to load changes and maintaining high accuracy air-fuel ratio control.
Note that in the aforementioned first embodiment, when the load on the internal
combustion engine
10 is recognized as changed, the amount of fuel to be
injected is corrected in such a manner as to improve not only the response to the
load change but also the air-fuel control accuracy. However, how to correct the
injection fuel amount is not limited to this manner. For example, correction may
be done so as to intentionally make richer the air-fuel ratio if improvement of
the response is given higher priority.
Second Embodiment
Referring to FIGS. 5 and 6, the following describes a second embodiment
of the present invention. In terms of hardware configuration, the system of this
embodiment is the same as that of the first embodiment. That is, the system of
this embodiment is provided with both an in-cylinder injector
22 and a port
injector
28 which are identical to those in the first embodiment.
[Characteristics of Second Embodiment]
In the internal combustion engine
10, some transport delay occurs until
fuel is introduced into the cylinder after the fuel is injected from the port injector
28. Therefore, increasing or decreasing the port injection fuel amount according
to the change of the engine load is not immediately reflected in the amount of
fuel to be injected into the cylinder from the intake port
12. Consequently,
in a transient period responding to a load increase, the amount of fuel entering
the cylinder from the intake port
12 is smaller than the ideal value. Also
in a transient period responding to a load decrease, the mount of fuel entering
the cylinder from the intake port
12 is larger than the ideal value.
On the contrary, the fuel injected from the in-cylinder injector
22 is
supplied into the cylinder without transport delay. Therefore, when the amount
of fuel injected into the cylinder from the intake port
12 is deficient,
the in-cylinder injection fuel amount can be increased so as to compensate for
the deficiency. Likewise, when the amount of fuel injected into the cylinder from
the intake port
12 is excessive, the in-cylinder injection fuel amount can
be decreased so as to compensate for the surplus. Using this capability of the
in-cylinder injector
22, the total injection fuel amount can be controlled
to an ideal value in each engine cycle even during transient periods.
FIG. 5 is a timing chart for explaining an in-cylinder injection fuel amount
calculation method which is used to implement the above-mentioned capability in
this embodiment. More specifically, FIG. 5A shows the waveform of the total requested
injection amount corresponding to load change. FIG. 5B shows the waveform of the
calculated port injection amount corresponding to the transition of the total requested
injection amount. FIG. 5C shows the transition of the in-cylinder injection amount
which would occur following the transition of the total requested injection amount
(broken line) and the transition of the in-cylinder injection amount which includes
the amount of fuel which compensates for the effect of the fuel transport delay
(solid line).
The amount of fuel which enters the cylinder from the intake port
12 shows
the largest transport delay effect immediately after the total requested injection
amount is changed. Then, the transport delay effect decreases with time after the
change occurs. Therefore, the largest compensating fuel amount is given to the
in-cylinder injection amount when the total requested injection amount is changed,
and then the compensating fuel amount is gradually reduced with time, as shown
in FIG. 5C in the system of this embodiment.
[Practical Processing in Second Embodiment]
FIG. 6 is a flowchart showing the flows of processing executed by the ECU
40
in this embodiment in order to implement the above-mentioned capability. These
flows of processing are to replace the processing of the step
106 in the
routine of FIG. 3. That is, this processing sequence is to be executed if step
104 in the routine of FIG. 3 judges the current timing to be "Before Injection
Amount Calculation Timing".
In the processing sequence shown in FIG. 6, a total requested injection amount
is calculated at first based on the operating condition and then a port injection
fuel amount Q
p and a reference in-cylinder injection fuel amount Q
DB
are calculated by dividing the requested amount between them at a predefined
ratio (step
160). Then, it is judged whether this total requested injection
amount is greatly larger than the total requested injection amount which was previously
calculated by the routine (whether an increase beyond a predefined value is recognized)
(step
162).
If it is judged that the total requested injection amount shows such a great
increase,
a request up flag is turned ON to indicate a sharp increase in the engine load
while a request down flag is turned OFF (step
164). In addition, a compensation
counter C is cleared so as to be associated with the start of a transient period
(step
166).
On the contrary, if the aforementioned step
162 results in a negative
judgment,
it is judged whether this total requested injection amount is greatly smaller than
the total requested injection amount which was previously calculated by the routine
(whether a decrease beyond a predefined value is recognized) (step
168).
If it is judged that the total requested injection amount shows such a great decrease,
the request down flag is turned ON to indicate a sharp decrease in the engine load
while the request up flag is turned OFF (step
170). Since this time point
is also a start time of a transient period, the aforementioned processing of step
166 is executed in order to clear the compensation counter C.
If it is judged by the aforementioned step
168 that the total requested
injection amount does not show a sharp decrease, processing goes to step
172
while maintaining the status of the request up flag, that of the request down flag
and the count value of the compensation counter C. In step
172, the compensation
counter C is incremented. By the procedure described so far, the elapsed time since
the occurrence of a sharp change in the total requested injection amount is measured
by the compensation counter C.
Then, in FIG. 6, a transport delay compensating value ΔQ
(c)
is calculated to compensate the port injection fuel for the transport delay effect
(step
174). The transport delay compensating value ΔQ(c) is a function
of the magnitude of the change in the total requested injection amount and the
count value of the compensation counter C. Practically, when the count value of
the compensation counter C is "1", that is, immediately after a sharp change is
detected in the total requested injection amount by step
162 or
168,
the ECU
40 calculates the initial value of the transport delay compensating
value ΔQ
(c) based on the magnitude of the change detected in the
total requested injection amount. The initial value of ΔQ
(c) is
set to be larger as the requested amount changes bigger.
In addition, if the count value of the compensation counter C is larger than
"1",
the ECU
40 calculates the transport delay compensating value ΔQ
(c)
by multiplying the aforementioned initial value by an attenuation factor k. The
attenuation factor k is initially "1.0" and decreases at almost a constant ratio
each time the compensation counter C is increased until it reaches to "0". Therefore,
the transport delay compensating value ΔQ
(c) gradually decreases
to "0" after the total requested injection amount shows a sharp change.
After the transport delay compensating value ΔQ
(c) is calculated,
it is judged whether the request up flag is ON (step
176). If the request
up flag is ON, it is judged that the transport delay effect is making insufficient
the amount of fuel which enters the cylinder. In this case, therefore, the amount
Q
D of fuel to be injected by the normal in-cylinder injection is obtained
by adding the transport delay compensating value ΔQ
(c) to the
reference in-cylinder injection amount Q
DB (step
178).
If the result of the above-mentioned processing of step
176 indicates
that
the request up flag is not ON, it is judged that the transport delay effect is
making excessive the amount of fuel which enters the cylinder. In this case, therefore,
the amount Q
D of fuel to be injected by the normal in-cylinder injection
is obtained by subtracting the transport delay compensating value ΔQ
(c)
from the reference in-cylinder injection amount Q
DB (step
179).
In the system of this embodiment, the values obtained according to the procedure
of FIG. 6 are treated as the amount of fuel to be injected by the port injection
(port injection fuel amount) and the amount of fuel to be injected by the normal
in-cylinder injection (reference in-cylinder injection fuel amount) (see FIG. 3).
Then, as described so far, the reference in-cylinder injection fuel amount is changed
by the processing sequence of FIG. 6 so as to compensate for the transport delay
of the port-injected fuel. That is, the corrected reference in-cylinder injection
fuel amount agrees with the solid line shown in FIG. 5C. In addition to the capabilities
of the first embodiment, therefore, this system embodiment can effectively prevent
the injection amount control accuracy from deteriorating due to the fuel transport delay.
The major benefits of the present invention described above are summarized as follows:
According to the first aspect of the present invention, in an internal
combustion engine provided with aport injector and an in-cylinder injector, if
the operating load on the internal combustion engine changes after the injection
amount calculation timing, it is possible to calculate a correction amount of fuel
corresponding to the change. By reflecting the correction amount in the cylinder
injection amount, the load change can quickly be reflected in the injection fuel
amount. Thus, the present invention can raise the response of the internal combustion engine.
According to the second aspect of the present invention, if a change of
the operating load on the internal combustion engine is detected after the injection
amount calculation timing and before a limit timing until which the amount of fuel
to be injected by the normal in-cylinder injection can be changed, the amount of
fuel to be injected by the normal cylinder injection can be increased or decreased.
In this case, both the increase and decrease in the operating load can be reflected
in the fuel injection amount.
According to the third aspect of the present invention, if an increase
of the operating load on the internal combustion engine is detected after the limit
timing until which the amount of fuel to be injected by the normal in-cylinder
injection can be changed, a cylinder injection can be executed after the normal
cylinder injection so as to inject the correcting amount of fuel corresponding
to the increase. Thus, the present invention can raise the response at acceleration.
According to the fourth aspect of the present invention, even if zero is
calculated as the reference cylinder injection amount at the injection amount calculation
timing and an increase of the operating load on the internal combustion engine
is detected later, a cylinder injection can be executed to inject a correction
amount of fuel corresponding to the increase. Thus, the present invention can raise
the response at acceleration.
According to the fifth aspect of the present invention, the deviation of
the amount of fuel which actually enters the cylinder from the intake port from
the ideal amount can be estimated based on the change of the load on the internal
combustion engine. The reference cylinder injection amount can be increased or
decreased so as to cancel the deviation. In this case, the error of the amount
of fuel that enters the cylinder from the port due to the transport delay can be
compensated for by the amount of fuel to be injected from the in-cylinder injector.
Thus, the present invention can accurately control the injection amount during
transient periods.
Further, the present invention is not limited to these embodiments, but
variations and modifications may be made without departing from the scope of the
present invention.
*
