U.S. patent application number 12/963071 was filed with the patent office on 2011-06-16 for apparatus for and method of controlling fuel injection of internal combustion engine.
This patent application is currently assigned to Hitachi Automotive Systems, Ltd.. Invention is credited to Atsushi Murai, Tomoyuki Murakami, Yoshitatsu NAKAMURA.
Application Number | 20110144891 12/963071 |
Document ID | / |
Family ID | 43993124 |
Filed Date | 2011-06-16 |
United States Patent
Application |
20110144891 |
Kind Code |
A1 |
NAKAMURA; Yoshitatsu ; et
al. |
June 16, 2011 |
APPARATUS FOR AND METHOD OF CONTROLLING FUEL INJECTION OF INTERNAL
COMBUSTION ENGINE
Abstract
There is provided a configuration in which a cylinder which is
in an inlet stroke when an internal combustion engine is in a stop
(automatic stop) state is determined and stored, and when starting
the engine upon detection of a start request, the fuel injection of
an initial cycle to the cylinder, which has been determined as
having been stopped in the inlet stroke when the engine was in the
stop state before starting, is split into a plurality if injections
at least including an injection before engine rotation, to thereby
perform injections. As a result, startability is improved while
suppressing pre-ignition at the time of starting.
Inventors: |
NAKAMURA; Yoshitatsu;
(Isesaki-shi, JP) ; Murakami; Tomoyuki;
(Isesaki-shi, JP) ; Murai; Atsushi; (Isesaki-shi,
JP) |
Assignee: |
Hitachi Automotive Systems,
Ltd.
|
Family ID: |
43993124 |
Appl. No.: |
12/963071 |
Filed: |
December 8, 2010 |
Current U.S.
Class: |
701/104 |
Current CPC
Class: |
F02D 41/061 20130101;
F02D 41/068 20130101; F02D 41/345 20130101; F02N 11/0814 20130101;
F02D 41/402 20130101; F02D 41/3005 20130101; Y02T 10/40 20130101;
F02D 2200/021 20130101; F02D 41/065 20130101; Y02T 10/48 20130101;
F02D 13/0234 20130101; F02D 41/062 20130101; F02D 2041/001
20130101; Y02T 10/44 20130101 |
Class at
Publication: |
701/104 |
International
Class: |
F02D 41/02 20060101
F02D041/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 14, 2009 |
JP |
2009-282946 |
Claims
1. An apparatus for controlling fuel injection of an internal
combustion engine for a vehicle comprising: a fuel injection valve
arranged so as to inject fuel to an inlet port of each cylinder of
the internal combustion engine; and a control unit which controls
driving of the fuel injection valve comprising: an inlet stroke
stopped cylinder determination section which determines a cylinder
stopped in an inlet stroke when the internal combustion engine is
stopped; a start request detection section which detects a start
request of the internal combustion engine; and a start-commencement
cylinder injection control section which, when starting the engine
upon detection of the start request, splits fuel injection of the
initial cycle to the cylinder, which has been determined as being
stopped in the inlet stroke when the internal combustion engine was
stopped before starting, into a plurality of injections at least
including an injection before engine rotation, to thereby perform
injections.
2. An apparatus according to claim 1, wherein the control unit
further comprises: an automatic engine stop section which stops
fuel injection when the vehicle stops to thereby automatically stop
the operation of the internal combustion engine; and the inlet
stroke stopped cylinder determination section determines a cylinder
which has been stopped in an inlet stroke when the internal
combustion engine is automatically stopped; the start request
detection section detects a start request of the internal
combustion engine, which has been automatically stopped; and the
start-commencement cylinder injection control section, when
starting the engine upon detection of the start request after the
internal combustion engine has been automatically stopped, splits
fuel injection of the initial cycle to the cylinder, which has been
automatically stopped in the inlet stroke, into a plurality of
injections at least including an injection before engine rotation,
to thereby perform injections.
3. An apparatus according to claim 1, further comprising: an engine
temperature detector which detects an engine temperature; and the
control unit further comprises: a warm-up completion state
determination section which determines a warm-up completion state
in which the detected engine temperature is greater than or equal
to a predetermined temperature; and the start-commencement cylinder
injection control section, when starting the engine upon the start
request detection in the determined warm-up completion state,
splits fuel injection of the initial cycle to the cylinder, which
has been determined as being stopped in the inlet stroke when the
internal combustion engine was stopped before starting, into a
plurality of injections at least including an injection before
engine rotation, to thereby perform injections.
4. An apparatus according to claim 3, wherein the control unit is
separately formed as: a fuel control unit which controls driving of
the fuel injection valve; and an automatic stop control unit which
outputs; an automatic stop request which stops driving the fuel
injection valve when the vehicle is stopped to thereby
automatically stop the operation of the internal combustion engine,
and a start request of the internal combustion engine which has
been automatically stopped, to the fuel control unit, and the fuel
control unit comprises: a fuel injection valve drive stop section
which stops fuel injection based on a start request signal from the
automatic stop control unit to thereby stop the operation of the
internal combustion engine; an inlet stroke cylinder determination
section which determines a cylinder stopped in an inlet stroke when
the internal combustion engine is automatically stopped; and a
start-commencement cylinder injection control section which, when
starting the engine based on the start request, splits fuel
injection in an initial cycle to a cylinder stopped in the inlet
stroke, into a plurality of injections at least including an
injection before engine rotation, to thereby perform
injections.
5. An apparatus according to claim 1, wherein the
start-commencement cylinder injection control section splits the
entire injection amount of the fuel injection of the initial cycle
into a plurality of injections before engine rotation, to thereby
perform injections.
6. An apparatus according to claim 1, wherein the
start-commencement cylinder injection control section splits the
fuel injection of the initial cycle into a plurality of injections
to thereby perform injections, so that the fuel is at least
injected respectively before and after engine rotation.
7. An apparatus according to claim 6, wherein the
start-commencement cylinder injection control section completes the
fuel injections after engine rotation before a timing by which an
operation of air-fuel mixture suction into the cylinder is
completed in the inlet stroke.
8. An apparatus according to claim 7, wherein the
start-commencement cylinder injection control section sets
injection intervals of the plurality of fuel injections, based on a
remaining period of time in an inlet stroke in a cylinder which has
been stopped in the inlet stroke.
9. An apparatus according to claim 6, wherein if a remaining period
of time of the inlet stroke of a cylinder which has been stopped in
the inlet stroke is determined as being within a predetermined
period of time, the start-commencement cylinder injection control
section injects before engine rotation, instead of the fuel
injection of the initial cycle of the cylinder, a fuel injection
amount of the initial cycle, to a cylinder which will undergo an
inlet stroke after this cylinder.
10. An apparatus according to claim 6, wherein the internal
combustion engine further comprises: a variable valve actuation
mechanism which can at least change a closing timing of an inlet
valve, and when a closing timing of an inlet valve of a cylinder
which is stopped in the inlet stroke is set to a retarded side of
an inlet bottom dead center by the variable valve actuation
mechanism, the start-commencement cylinder injection control
section sets an injection completion timing of a final injection
after engine rotation, to a timing before the inlet bottom dead
center.
11. An apparatus according to claim 6, wherein the
start-commencement cylinder injection control section controls an
injection commencing timing of fuel injection after engine
rotation, based on an engine rotation speed.
12. An apparatus according to claim 1, wherein the
start-commencement cylinder injection control section performs
control so that an injection period of an earlier fuel injection is
made longer than an injection period of a later fuel injection.
13. An apparatus for controlling fuel injection of an internal
combustion engine for a vehicle comprising: a fuel injection valve
arranged so as to inject fuel to an inlet port of each cylinder of
the internal combustion engine; a start request detection means
which detects a start request of the internal combustion engine; an
inlet stroke stopped cylinder determination means which determines
a cylinder stopped in an inlet stroke when the internal combustion
engine is stopped; a start request detection means which detects a
start request of the internal combustion engine; and a
start-commencement cylinder injection control means which, when
starting the engine upon detection of the start request, splits
fuel injection of the initial cycle to the cylinder, which has been
determined as being stopped in the inlet stroke when the internal
combustion engine was stopped before starting, into a plurality of
injections at least including an injection before engine rotation,
to thereby perform injections.
14. A method of controlling fuel injection of an internal
combustion engine for a vehicle, the method comprising the steps
of: injecting fuel from a fuel injection valve arranged in an inlet
port of each cylinder of the internal combustion engine;
determining a cylinder which has been stopped in an inlet stroke
when the internal combustion engine is stopped; detecting a start
request of the engine; and controlling the fuel injection valve so
that, when starting the engine upon detection of the start request,
fuel injection of the initial cycle to the cylinder, which has been
determined as being stopped in the inlet stroke when the internal
combustion engine was stopped before starting, is split into a
plurality of injections at least including an injection before
engine rotation, to thereby perform injections.
15. A method according to claim 14, the method further comprising
the steps of: stopping fuel injection when the vehicle stops, to
thereby automatically stop the operation of the internal combustion
engine; and in the step of determining a cylinder, determining the
cylinder which has been stopped in the inlet stroke when the
internal combustion engine is automatically stopped; in the step of
detecting the start request, detecting a start request of the
internal combustion engine, which has been automatically stopped;
and in the step of controlling the fuel injection valve, when
starting the engine upon detection of the start request after the
internal combustion engine has been automatically stopped,
splitting fuel injection of the initial cycle to the cylinder,
which has been automatically stopped in the inlet stroke, into a
plurality of injections at least including an injection before
engine rotation, to thereby perform injections.
16. A method according to claim 14, the method further comprising
the steps of: detecting an engine temperature; and determining a
warm-up completion state in which the detected engine temperature
is greater than or equal to a predetermined temperature, and in the
step of controlling the fuel injection valve, when starting the
engine upon the start request detection in the determined warm-up
completion state, splitting fuel injection of the initial cycle to
the cylinder, which has been determined as being stopped in the
inlet stroke when the internal combustion engine was stopped before
starting, into a plurality of injections at least including an
injection before engine rotation, to thereby perform
injections.
17. A method according to claim 14, wherein in the step of
controlling the fuel injection valve, the entire injection amount
of the fuel injection of the initial cycle is split into a
plurality of injections before engine rotation, to thereby perform
injections.
18. A method according to claim 14, wherein in the step of
controlling the fuel injection valve, the fuel injection of the
initial cycle is split into a plurality of injections to thereby
perform injections, so that the fuel is at least injected
respectively before and after engine rotation.
19. A method according to claim 18, wherein in the step of
controlling the fuel injection valve, the fuel injections after
engine rotation, are completed before a timing by which an
operation of air-fuel mixture suction into the cylinder is
completed in the inlet stroke.
20. A method according to claim 18, wherein in the step of
controlling the fuel injection valve, if a remaining period of time
of the inlet stroke of a cylinder which has been stopped in the
inlet stroke is determined as being within a predetermined period
of time, the start-commencement cylinder injection control section
injects before engine rotation, instead of the fuel injection of
the initial cycle of the cylinder, a fuel injection amount of the
initial cycle to a cylinder which will undergo an inlet stroke
after this cylinder.
Description
1. FIELD OF THE INVENTION
[0001] The present invention relates to an apparatus for and a
method of controlling fuel injection of an internal combustion
engine, in particular, to fuel injection control performed when
restarting an internal combustion engine which has been
automatically stopped or when starting it in a warm-up completion
state.
2. DESCRIPTION OF RELATED ART
[0002] Japanese Laid-open (Kokai) Patent Application Publication
No. 2008-215192 discloses a fuel injection control apparatus of an
internal combustion engine in which, at the time of restarting
after completion of a warm-up operation (when restarting from an
idle stop state for example) fuel injection is executed before
starting (cranking), and the fuel injection amount during starting
after engine rotation is reduction-corrected.
[0003] The above disclosed apparatus is of a configuration in which
an injection amount required for starting is injected all at once
in a state in which the engine is stopped before starting (before
engine rotation).
[0004] However, in such a configuration in which the entire amount
is injected at once, the penetration force (penetration) of fuel
spray is high and injection is performed in a state in which there
is no intake air flow towards the interior of a cylinder.
Consequently, the amount of adhesion on the inlet air passage wall
surface becomes high and the evaporation rate within the inlet air
passage becomes reduced.
[0005] Therefore there is a possibility that the effect of cooling
the interior of the inlet air passage by the latent heat of
vaporization of the fuel spray may be reduced, and intake air of a
comparatively high temperature may be introduced into a cylinder at
the time of restarting the engine, consequently causing an
auto-igniting phenomenon (pre-ignition) to occur.
SUMMARY OF THE INVENTION
[0006] Consequently, an object of the present invention is to
suppress pre-ignition when restarting an internal combustion engine
which has been automatically stopped, or when starting it in a
warm-up completion state, and thereby improve startability.
[0007] In order to achieve the above object, the present invention
is
[0008] an apparatus for and a method of controlling fuel injection
of an internal combustion engine for a vehicle in which fuel is
injected from a fuel injection valve to an inlet port of each
cylinder, wherein:
[0009] A. a cylinder which has been stopped in an inlet stroke is
determined when the internal combustion engine is stopped;
[0010] B. a start request of the internal combustion engine is
detected; and
[0011] C. when starting the engine based on the start request, fuel
injection in the initial cycle to the cylinder, which was stopped
in the inlet stroke, is split into a plurality of injections at
least including an injection before engine rotation, to thereby
perform injections.
[0012] The other objects and features of this invention will become
understood from the following description with reference to the
accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a configuration diagram of an internal combustion
engine for a vehicle to which the present invention is applied.
[0014] FIG. 2A is a time chart of a first embodiment, and FIG. 2B
is a time chart of a second embodiment.
[0015] FIG. 3A is a time chart of a third embodiment, and FIG. 3B
is a time chart of a fourth embodiment.
[0016] FIG. 4A is a time chart of a fifth embodiment, and FIG. 4B
is a time chart of a sixth embodiment.
[0017] FIG. 5A is a flow chart of the first embodiment.
[0018] FIG. 5B is a flow chart of the second and fourth
embodiments.
[0019] FIG. 5C is a flow chart of the third and fifth
embodiments.
[0020] FIG. 5D is a flow chart of the sixth embodiment.
[0021] FIG. 5E is a flow chart of a seventh embodiment.
[0022] FIG. 6 is a time chart of an example of the second
embodiment.
[0023] FIG. 7 is a time chart of another example of the second
embodiment.
[0024] FIG. 8 is a flow chart of valve closing timing control of an
inlet valve when the internal combustion engine is automatically
stopped.
[0025] FIG. 9 is a time chart of valve closing timing control of
the same inlet valve.
[0026] FIG. 10A is an enlarged view of a peripheral part of an
injection nozzle hole of a spray impingement type fuel injection
valve, FIG. 10B is a cross-sectional view showing a nozzle plate in
FIG. 10A alone, FIG. 10C is a plan view showing the nozzle plate
alone, FIG. 10D is an enlargement view of a relevant part showing
the respective nozzle hole pairs in FIG. 10C being operated in a
fuel injection operation, and FIG. 10E is an enlarged
cross-sectional view of each nozzle hole, which constitutes the
nozzle hole pair, seen from the direction illustrated with arrows
VI-VI in FIG. 10D.
[0027] FIG. 11 is a flow chart showing a relevant part of fuel
pressure raising control at the time of restarting.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0028] Hereunder, embodiments of the present invention are
described, with reference to the accompanying drawings.
[0029] FIG. 1 is a configuration diagram of an internal combustion
engine for a vehicle to which the present invention is applied. On
an inlet pipe 102 of an internal combustion engine 101 there is
disposed an electronically controlled throttle 104 which drives a
throttle valve 103b open and close, with a throttle motor 103a. Air
is sucked into a combustion chamber 106 via electronically
controlled throttle 104 and an inlet valve 105.
[0030] Exhaust gas is discharged from combustion chamber 106
through an exhaust valve 107, is purified in a front catalyst 108
and a rear catalyst 109, and is then discharged into the
atmosphere.
[0031] Exhaust valve 107 is driven to open or close by a cam 111
supported on an exhaust side cam shaft 110, while maintaining a
constant lift amount and a working angle (crank angle from open to
close). On the other hand, regarding inlet valve 105, lift amount
and working angle, that is, valve opening, can be continuously
changed by a variable valve lift mechanism 112. The lift amount and
working angle can be simultaneously changed so that when the
characteristic of one is determined, the characteristic of the
other is also determined.
[0032] On both end sections of an inlet side cam shaft, there are
provided a variable valve timing mechanism 201 and an inlet side
cam angle sensor 202. Variable valve timing mechanism 201 includes
a mechanism which continuously performs variable control of
rotational phase difference between the crank shaft and the inlet
side cam shaft to thereby advance or retard the valve timing (valve
opening/closing timing) of inlet valve 105. Inlet side cam angle
sensor 202 detects a rotational position of the inlet side cam
shaft.
[0033] An engine control electronic control unit (EECU) 114
controls electrically controlled throttle 104 and variable valve
lift mechanism 112 depending on the opening of an acceleration
pedal detected by an accelerator opening sensor APS 116. With this
control, by using the opening of throttle valve 103b and the
opening characteristic of inlet valve 105 it is possible to obtain
a target intake air amount which corresponds to an accelerator
opening ACC. Accelerator opening sensor APS 116 has a built-in idle
switch 116a which detects an accelerator opening equal to or less
than a predetermined opening, as an idle state (turned ON).
[0034] EECU 114 receives signal inputs from each of the following
sensors as well as from accelerator opening sensor APS 116 and
inlet side cam angle sensor 202. A rotation angle sensor 127
detects a rotational angle of a control shaft which is driven by an
electric motor serving as an actuator of variable valve lift
mechanism 112. Detection of the rotational angle of the control
shaft corresponds to detection of the lift amount and working angle
of the inlet valve. An airflow meter 115 detects an intake air
amount Q of engine 101. A crank angle sensor 117 extracts engine
rotation signals (a signal output at every unit angle and a
cylinder determination signal output at every stroke phase
difference) from the crank shaft. A throttle sensor 118 detects an
opening TVO of throttle valve 103b. A water temperature sensor 119
detects a cooling water temperature Tw of engine 101. A vehicle
traveling speed sensor 125 detects a vehicle traveling speed, and a
brake sensor 126 detects an operating state (ON and OFF) of a
brake.
[0035] Moreover, on an inlet port 130 on the upstream side of inlet
valve 105 of each of the cylinders, there is provided an
electromagnetic type fuel injection valve 131. Fuel injection valve
131 injects fuel, which has been adjusted to a predetermined
pressure, toward inlet valve 105, when it is driven open by an
injection pulse signal from EECU 114.
[0036] On the other hand, an idle-stop control electronic control
unit (ISECU) 120 performs idle stop control which stops fuel
injection of the internal combustion engine to thereby
automatically stop its operation when the vehicle is stopped in an
idle state (in a state in which the accelerator pedal is released),
and performs control to restart the internal combustion engine when
the operation has been automatically stopped and an occurrence of a
restart request has been detected.
[0037] Moreover, as vehicle power supplies, there are provided a
lead battery 121 and a lithium-ion battery 122. At restart after
the internal combustion engine is automatically stopped, a starter
123 is activated using high-voltage lithium-ion battery 122. When
starting the engine by manually operating a starter switch,
low-voltage lead battery 121 is used to activate starter 123. ISECU
120 performs switching control of a switching relay 124 to thereby
switch the battery to be used. ISECU 120 also performs control for
maintaining the state of charge (SOC), the voltage, and the like of
lithium-ion battery 122.
[0038] From EECU 114, ISECU 120 receives signals from sensors
required for performing these controls such as idle switch 116a,
vehicle traveling speed sensor 125, brake sensor 126, and the like,
and it sends command signals for automatically stopping and
restarting the engine to EECU 114, so as perform these
controls.
[0039] EECU 114 determines and stores the cylinder which is in an
inlet stroke when the internal combustion engine is automatically
stopped (the cylinder in which a piston therein is stopped at an
inlet stroke position. Hereunder, referred to as inlet stroke
stopped cylinder), and the crank angle position of the inlet stroke
stopped cylinder. When starting the engine based on the start
request, fuel injection in the initial cycle with respect to the
inlet stroke stopped cylinder is split into a plurality of
injections at least including an injection performed before engine
rotation, to thereby perform injections.
[0040] In this embodiment, there are provided two ECU units namely
EECU 114 and ISECU 120, and control functions are assigned thereto,
and consequently the size of individual ECU units can be made
compact, thereby improving the degree of freedom in the layout
thereof. However, of course the configuration may also be provided
so as to perform both controls on a single ECU unit.
[0041] Next, there are described respective embodiments of fuel
injection control, according to the present invention, for when
restarting based on a start request after automatic stop. In the
respective embodiments, in addition to a start request after
automatic stop, a restart request after completion of a warm-up
operation (an operation of a starting switch such as an ignition
switch and a start switch performed by a driver) may be judged, and
fuel injection control in restarting may be executed according to
the respective embodiments.
[0042] When a predetermined idle stop condition (automatic stop
condition) is satisfied, fuel injection of the internal combustion
engine is stopped and the engine operation is automatically
stopped. The predetermined idle stop condition includes a moment
when depression of a brake pedal is detected in a vehicle stop
state for example.
[0043] The vehicle stop state may be determined when a detection
value VSP detected by the vehicle traveling speed sensor 125 is 0,
or it is less than or equal to a predetermined value for
determining a vehicle stop.
[0044] Moreover, detection of depression of the brake pedal may be
determined as a state in which the brake pedal is depressed when a
detection value of brake sensor 126 is greater than or equal to a
predetermined value.
[0045] The brake sensor is of a configuration capable of detecting
a depression amount of the brake pedal. However, a brake switch
which detects a depression of the brake pedal as ON/OFF may also be
adapted thereto, so that a depression of the brake pedal is
determined when the brake switch is turned ON.
[0046] Moreover, in addition to the above idle stop condition,
there may be set an idle stop condition by adding or combining
conditions such as: it is in a warm-up completion state in which
the engine cooling water temperature is greater than or equal to a
predetermined value; the idle switch 116a is ON and the engine is
determined to be in an idle operating state, or the engine rotation
speed Ne is within a set rotation speed range in an idle state; and
the state of charge of the battery is greater than or equal to a
predetermined value which enables restarting.
[0047] After having performed the above automatic stop of the
internal combustion engine, when there has been detected a restart
request caused by a brake release or a depression of the
accelerator pedal performed by the driver, that is to say, when the
detection value of the brake sensor is less than or equal to the
predetermined value, or when the brake switch OFF is detected or
accelerator opening sensor APS 116 detects an accelerator opening
greater than or equal to a predetermined value, which is outside
the idle operation range, the fuel injection amount of each
cylinder is set as follows.
[0048] First, at the time of automatic stop, the inlet stroke
stopped cylinder is determined and stored, and the fuel injection
amount at the time of restarting (hereunder, referred to as restart
time injection amount) is split to perform injection a plurality of
number of times. Here, the split injections in which the restart
time injection amount is split into a plurality of number of times
may be performed during a period from the opening timing of the
inlet valve to the closing timing of the inlet valve.
[0049] Moreover, when the inlet valve closing timing is controlled
by an operation of variable valve timing mechanism 201 and variable
valve lift mechanism 112, to be after bottom dead center of the
piston, and the engine is stopped, after the piston bottom dead
center, even if the inlet valve is open when starting, the piston
still rises after engine rotation. Therefore injected fuel is not
easily sucked, and it becomes difficult to introduce the restart
time injection amount into the cylinder.
[0050] Consequently, it is preferable that split injections are
completed before bottom dead center of the piston which is on the
advanced side of the inlet valve closing timing.
[0051] By completing split injections at the piston bottom dead
center or before bottom dead center, the split injections are
completed in a state in which the piston is descending, that is to
say, in a state in which the speed of suction into the cylinder by
the piston is comparatively high. Therefore, introduction of
injected fuel into the cylinder becomes easier, and superior
combustion can be performed, thereby improving startability.
[0052] It is more preferable that the split injections are
completed before approaching the vicinity of 30.degree. before
bottom dead center. That is to say, a delay occurs after injecting
fuel from the fuel injection valve until it is introduced into the
cylinder. Therefore taking this delay into consideration, it is
preferable that the timing at which the fuel injected from the fuel
injection valve is introduced into the cylinder, is set as a limit
timing of the split injection completion timing, and the split
injections are completed before the limit timing is reached.
[0053] If in the vicinity of 30.degree. before bottom dead center,
the restart time injection amount can be introduced into the
cylinder by performing split injections.
[0054] Moreover, when the inlet valve closing timing is controlled
by an operation of variable valve timing mechanism 201 and variable
valve lift mechanism 112 to be at or before bottom dead center of
the piston, it is preferable that the split injections are
completed before the closing timing.
[0055] Furthermore, in this case also, so that the injected fuel is
introduced into the cylinder before the closing timing, it is
preferable that the split injections are completed before the limit
timing, which is set before the closing timing, taking into
consideration the delay from injection from the fuel injection
valve until introduction into the cylinder. As a result,
introduction of the injected fuel into the cylinder becomes easier,
and superior combustion can be performed, thereby improving
startability.
[0056] FIG. 2A shows a time chart of a first embodiment (the
horizontal axis t represents time).
[0057] In this embodiment, there is illustrated a case of
performing split injection twice before engine rotation. Regarding
the injection timing, injection timing of the initial injection is
set immediately after a restart request has been detected, and
injection timing of the second injection is set after a
predetermined delay time Dspl has elapsed after completion of the
initial injection.
[0058] The second injection timing is set so as to satisfy the
following relationship so that the second injection is completed
before engine rotation is commenced.
Dspl<tw-tp1-tp2=tw-tp (1)
[0059] where, tw represents a set time from a moment when a restart
request is made to a moment when the starter is activated and
restarting (cranking) is commenced, tp1 represents the initial
injection amount (injection time), and tp2 represents the second
injection amount (injection time). Consequently, the starting time
injection amount tp=tp1+tp2.
When tp1 equals tp2, then tp1=tp2=tp/2
[0060] As a result, in a cylinder which is in an inlet stroke
immediately after a restart request has been made, superior
combustion can be commenced as described below.
[0061] In the initial cycle after restarting, by splitting the
starting time injection amount into a plurality of number of times
including the injection before engine rotation, split injections
are performed in single short injection times, and the resistance
of air having no flow in the stop state becomes greater.
Consequently, the penetration force of the fuel spray injected from
the fuel injection valve becomes weak and the amount of fuel
becoming attached to the inlet air passage wall surface is reduced,
while the amount of fuel spay drifting inside the inlet air passage
increases.
[0062] Here, regarding the inlet stroke stopped cylinder, since the
inlet valve is open, the heat of high-temperature gas such as
residual gas within the cylinder is transmitted to the inlet air
passage side, and the air inside the inlet air passage is
consequently excessively heated to a higher temperature compared to
that of the inlet air passage wall. Therefore, the increased amount
of fuel spray drifting inside the inlet air passage is exposed to
the high-temperature air within the inlet air passage and becomes
evaporated, thereby increasing the air cooling effect due to latent
heat of vaporization. As a result, cooled inlet air is introduced
into the cylinder when engine rotation is commenced. Therefore it
is possible to suppress an increase in in-cylinder temperature in
the compression stroke, and suppress the occurrence of
pre-ignition.
[0063] Incidentally, comparing with the conventional technique
disclosed in Patent Document 1 above, in the conventional
technique, the whole amount of a start request fuel injection
amount is injected all at once before the engine rotates. Therefore
the penetration force of the spray is significant, and since there
is no flow of the sucked air toward the interior of the cylinder,
the amount of fuel spray drifting within the inlet air passage
decreases, and on the other hand, the amount of the fuel which
becomes attached to the inlet air passage wall surface increases.
Therefore it is clear that the air cooling effect is low and the
occurrence of pre-ignition cannot be easily suppressed.
[0064] The initial injection timing before engine rotation is
preferably immediately after a start request has been made. In this
way, it is possible to make the time to ignition timing or engine
rotation longer, and thereby create a sufficient amount of
evaporation time, thus enabling promotion of in-cylinder
cooling.
[0065] On the other hand, the second injection timing is shown in
the diagram as being when injection is completed immediately before
engine rotation is commenced. However it is not limited to this
timing. For example, preferably the second injection timing is set
through experiment, simulation, or the like, to a timing where the
cooling effect becomes greatest. The same applies to the ratio
between the first injection amount and the second injection amount
(split ratio).
[0066] Moreover, the configuration may be such that injections
split into three times or more are performed before engine
rotation. In this case, the single injection amount is reduced and
the penetration force is further weakened. Therefore evaporation is
facilitated and the effect of suppressing adhesion to the inlet
port wall is also increased, so that the cooling effect of the air
within the inlet port can be increased.
[0067] Next, there is described an embodiment in which, when
restarting, an injection is performed before engine rotation, for
the initial cycle of the inlet stroke stopped cylinder, as well as
after commencing engine rotation.
[0068] In a second embodiment shown in FIG. 2B, an injection amount
which is set by splitting injection into two (1/2 of the restart
time injection amount) is injected respectively before engine
rotation and after engine rotation. Regarding the injection timing,
the injection commencing timing when the engine is stopped is set
to an injection commencing timing of the initial injection
immediately after the restart request has been detected. After
completion of the injection when the engine is stopped, an
injection commencing timing for injection after engine rotation is
set after a predetermined delay time Dspl has elapsed, to commence
the second injection.
[0069] Using the respective values in the expression (1), this is
set so as to satisfy the following condition:
Dspl>tw-tp1 (2)
[0070] Next, there is described an operation and effect of the
second embodiment.
[0071] 1) Regarding the inlet stroke stopped cylinder, since the
inlet valve is open, the heat of high-temperature gas such as
residual gas within the cylinder is transmitted to the interior of
the inlet air passage, and the air inside the inlet air passage is
consequently excessively heated to a higher temperature compared to
that of the inlet air passage wall.
[0072] Consequently, the restart time injection amount is split and
set for the cylinder which is in an inlet stroke immediately after
the restart request has been made. The first split injection is
executed in a state before the engine rotates, where there is no
air flow and the air resistance is high. Consequently, the
penetration force of the fuel spray injected from the fuel
injection valve becomes weak and the amount of fuel becoming
attached to the inlet air passage wall surface is reduced, while
the amount of fuel spay drifting inside the inlet air passage
increases. The increased fuel spray formed by the injection before
engine rotation and having a weak penetration force is exposed to
high-temperature air within the inlet air passage and evaporates,
and consequently, the air cooling effect due to the latent heat of
vaporization is increased. Then this cooled inlet air is introduced
into the cylinder when engine rotation is commenced. Therefore it
is possible to suppress an increase in the in-cylinder temperature
in the compression stroke and suppress the occurrence of
pre-ignition.
[0073] 2) The fuel spray injected after engine rotation travels on
the inlet air flow and is introduced into the cylinder, and the
air-fuel mixture is dispersed and introduced into the cylinder
while being diffused. The air-fuel mixture within the cylinder
(concentration) becomes uniform, and the effect of suppressing
pre-ignition occurrence is further increased.
[0074] FIG. 3A shows a third embodiment in which the number of
splittings is set to three or more.
[0075] First, at the time of automatic stop, based on the piston
position of the inlet stroke stopped cylinder, there is predicted a
time tc from the moment when restart (cranking) of this cylinder is
commenced to the moment when the inlet valve is closed. This
prediction may be performed by experiment, simulation, or the like,
and it may be set to a map or the like as a predicted time tc
corresponding to each piston position (or a total time is with tw
described later). Moreover, since the cranking speed varies
according to parameters such as battery voltage, state of charge,
and cooling water temperature, the predicted time tc may be
corrected based on detection values of these parameters.
[0076] In an internal combustion engine in which the inlet valve
closing timing is changed by an operation of variable valve timing
mechanism 201 and variable valve lift mechanism 112 according to
the engine operating state when it is in an idle stop state, the
inlet valve closing timing at the time of restarting is found based
on the operating status of variable valve timing mechanism 201 and
variable valve lift mechanism 112, to thereby calculate the
predicted time tc.
[0077] Moreover, as described above, when the inlet valve closing
timing is controlled to be after bottom dead center of the piston
by an operation of variable valve timing mechanism 201 and variable
valve lift mechanism 112, the split injections are to be completed
before inlet bottom dead center, or more preferably before
approaching the vicinity of 30.degree. before bottom dead center.
Therefore, with consideration of a delay, which occurs after
injecting fuel from the fuel injection valve until it is introduced
into the cylinder, it is preferable that the timing at which the
fuel injected from the fuel injection valve is introduced into the
cylinder is set as a limit timing of the split injection completion
timing, and the split injections are completed at or before the
limit timing is reached. Therefore, in this case, the predicted
time tc may be predicted as a time tc from the moment after
commencing restarting (cranking) to the moment when the limit
timing is reached.
[0078] Moreover, the split injections are completed within the time
from the moment when the restart request is detected to the moment
when the inlet valve is closed, or within the time in which the
limit timing is reached. That is to say, the split injections are
completed during the total time is in which the predicted time tc
until the inlet valve is closed after commencing the restarting
(cranking) or until the limit timing is reached, is added to the
set time tw from the moment when the restart request was made to
the moment when the starter is activated and restarting (cranking)
is commenced.
[0079] That is to say, the restart time injection amount tp is
divided by the number of splits n to thereby set a single split
injection amount, and a delay time Dspl which serves as a split
injection interval time may be set so that the split injections are
completed within the total time ts.
[0080] First, the number of splits n may be set to a preliminarily
decided value (3 to 5 for example), however, it may also be
variably set based on the above total time ts. For example, if the
split number n is made high (low), then a single split injection
amount becomes low (high), and the amount of evaporation time
required for this single injection amount decreases (increases),
however, the delay time Dspl also decreases (increases). Therefore,
it is preferable that the delay time Dspl is made greater than the
required evaporation time, and the split number n is set to a
number where the evaporation efficiency of the entire restart time
injection amount becomes highest.
[0081] Moreover, the injection commencing timing of the initial
injection is set immediately after the restart request has been
detected and a fuel injection is executed. Having completed the
injection, split injections are executed for the decided split
number of times when each delay time Dspl has elapsed.
[0082] Next, there is described an operation and effect of the
third embodiment.
[0083] The third embodiment exhibits at least one of the following
effects.
[0084] 1) When performing split injections three times or more, if
the number of injections before the engine rotates increases, the
single injection amount is further reduced and the penetration
force thereof is further weakened. Therefore evaporation is further
facilitated. As a result, the effect of suppressing adhesion to the
inlet port is also increased and the amount of fuel spray drifting
within the inlet air passage increases. Therefore the cooling
effect of the air within the inlet port due to the latent heat of
vaporization, can be increased.
[0085] 2) If the number of injections after engine rotation is
increased, injection can be continued intermittently in the inlet
stroke. Therefore, disproportion in the injection amount in the
inlet stroke can be further reduced, and the uniformity of the
air-fuel mixture within the cylinder can be further improved.
[0086] 3) By reducing the injection amount in the vicinity of inlet
stroke completion, an injection amount according to the reduced gas
flow is achieved. Furthermore, the uniformity of the air-fuel
mixture within the cylinder can be improved.
[0087] Also in the third embodiment, there can be achieved the
operation and effects of increasing the effect of suppressing
pre-ignition occurrence by: 1) the cooling effect of the air within
the inlet port due to the injection before engine rotation having a
weak penetration force; and 2) the uniformity of the air-fuel
mixture in the cylinder achieved by the injection after engine
rotation, which are the operation and effects disclosed in the
second embodiment above.
[0088] FIG. 3B shows a fourth embodiment. In this embodiment, in a
configuration in which a single injection before and after engine
rotation, that is, a total of two injections are performed, the
first injection amount before engine rotation is higher than the
second injection amount after engine rotation.
[0089] Regarding the injection timing, the injection commencing
timing when the engine is stopped is set to an injection commencing
timing of the initial injection immediately after a restart request
has been detected, to thereby perform an injection when the engine
is stopped. After having completed the injection, an injection
commencing timing for an injection after engine rotation is set
after a predetermined delay time Dspl has elapsed, to commence the
second injection.
[0090] Using the respective values in the expression (1), this is
set so as to satisfy the following condition:
Dspl>tw-tp1 (2)
[0091] It is preferable that the amount of the initial fuel
injection is set in a range in which evaporation is possible within
the delay time Dspl. As a result, the fuel injection after having
commenced engine rotation can be executed in a state in which the
fuel of the initial injection has evaporated. That is to say, if
the fuel spray of the initial fuel injection in a non-evaporated
state impinges on the fuel spray injected after commencing engine
rotation, the particle diameter thereof increases and consequently
vaporization becomes more unlikely, so that promotion of
vaporization by the latent heat of vaporization is reduced. On the
other hand, by setting the delay time Dspl so that the fuel of the
initial injection evaporates, such a reduction in promotion of
vaporization can be suppressed.
[0092] Moreover, there may be provided a detection means which
detects the temperature within the inlet air passage (inlet air
temperature), and the initial fuel injection amount may be variably
set according to the detected temperature in the inlet air
passage.
[0093] In this case, the amount of fuel which can evaporate within
the delay time Dspl can be made higher as the temperature within
the inlet air passage becomes higher. Therefore the initial fuel
injection amount is set to an even higher amount.
[0094] As a result, since a higher amount of fuel can be set to the
initial fuel injection amount when the inlet air temperature is
comparatively high, the effect of cooling due to the latent heat of
vaporization can be increased, and the inlet air temperature within
the inlet air passage can be reduced.
[0095] Detection of the temperature within the inlet air passage
may be performed with a configuration provided with a temperature
sensor within the inlet air passage, or the temperature of the
cylinder interior may be detected directly or indirectly (estimated
based on the cooling water temperature or the like), and the
temperature within the inlet air passage then estimated based on
the temperature of the cylinder interior.
[0096] Next, there is described an operation and effect of the
fourth embodiment.
[0097] In this embodiment, the first injection amount before engine
rotation where the vaporization time until introduction into the
cylinder can be made long, is made greater than the second
injection amount after engine rotation where the vaporization time
is short, and thereby vaporization efficiency can be improved.
[0098] Also in this embodiment, there can be achieved the operation
and effects of increasing the effect of suppressing pre-ignition
occurrence by: 1) the cooling effect of the air within the inlet
port due to the injection before engine rotation having a weak
penetration force; and 2) the uniformity of the air-fuel mixture in
the cylinder achieved by the injection after engine rotation, which
are the operation and effects disclosed in the second embodiment
above.
[0099] FIG. 4A shows a fifth embodiment. In this embodiment, in a
configuration in which injections are split into three injections
to be performed, the injection amount is made greater when the
injection is performed earlier, and the injection amount is made
less when the injection is made later.
[0100] When automatic stop is performed, as with the third
embodiment, the split injection completion timing is controlled
based on the piston position of the inlet stroke stopped cylinder.
That is to say, a time tc from the moment after restarting
(cranking) of the cylinder is commenced, to the moment when the
inlet valve is closed, or a time tc until the limit timing, which
was used in the third embodiment, is reached, is predicted. The
split injections are completed during the total time ts in which
the predicted time tc is added to a time until the inlet valve is
closed after detecting a restart request or until the limit timing
is reached, that is, a set time tw from the moment when the restart
request was made to the moment when the starter is activated and
restarting (cranking) is commenced.
[0101] On the other hand, in this embodiment, an assigned ratio (%)
of the individual split injection amounts is preliminarily set
where the starting time injection amount is taken as 100%, and the
starting time injection amount is multiplied by the assigned ratio
to thereby set individual injection amounts. A greater assigned
ratio is set higher when the order of injection is earlier, and the
assigned ratio is set so that a higher injection amount is
injected.
[0102] The number of splits n may be set to a preliminarily decided
value (3 to 5 for example), however, it may also be variably set
based on the above total time ts.
[0103] The delay time Dspl, which serves as a split injection
interval time, may be set based on the restart time injection
amount tp, the total time ts, and the split number n, so that the
split injections are completed within the total time ts.
[0104] Moreover, the injection commencing timing of the initial
injection is set immediately after the restart request has been
detected, and a fuel injection is executed. Having completed the
injection, split injections are executed the decided split number
of times when each delay time Dspl has elapsed.
[0105] Furthermore the delay time Dspl may be simply set as a
single value, with which the intervals of the respective split
injections are equal. However, as another setting method, by having
the delay time Dspl made longer for an earlier injection order, a
longer vaporization time can be ensured and it is possible to
suppress impingement on the fuel spray caused by the next split
injection.
[0106] As a result, impingement of the fuel sprays between
individual split injections can be suppressed, so that the
reduction in the vaporization efficiency caused by the increase in
particle diameter of the fuel spray due to impingement can be
suppressed.
[0107] Next, there is described an operation and effect of the
fifth embodiment.
[0108] In this embodiment, the injection amount is made greater for
an earlier injection which allows prolonged vaporization time until
introduction into the cylinder, and the injection amount is made
less for a later injection in which vaporization time is short.
Thereby vaporization efficiency can be improved.
[0109] Also in the fifth embodiment, there can be achieved the
operation and effects of increasing the effect of suppressing
pre-ignition occurrence by: 1) the cooling effect of the air within
the inlet port due to the injection before engine rotation having a
weak penetration force; and 2) the uniformity of the air-fuel
mixture in the cylinder achieved by the injection after engine
rotation, which are the operation and effects disclosed in the
second embodiment above.
[0110] FIG. 4B shows a sixth embodiment. In this embodiment, an
engine rotation speed (cranking speed) is detected after engine
rotation has commenced, and when the rotation speed has reached a
predetermined value, injection after engine rotation is
commenced.
[0111] In this embodiment, an injection amount which is set by
splitting the injection into two (1/2 of the restart time injection
amount) is injected respectively before engine rotation and after
engine rotation. Regarding the injection timing, the injection
commencing timing when the engine is stopped is set to an injection
commencing timing of the initial injection immediately after the
restart request has been detected, and after completion of the
injection when the engine is stopped, a split injection after
engine rotation is executed when the engine rotation speed Ne is
determined to be greater than or equal to a predetermined
value.
[0112] This predetermined value is set for detecting engine
rotation being actually commenced by commencement of cranking for
example, and it is set to a value less than or equal to the
rotation speed of the idle operation. The engine rotation speed may
be calculated, for example, based on the angle at pulse occurrence
of crank angle sensor 117 (for example, 10.degree.) and pulse
interval time when the pulse occurs.
[0113] The number of split injections before engine rotation may be
a plurality of number of times. The number of split injections
after engine rotation may also be a plurality of number of times.
The delay time Dspl of injection intervals may be set so that the
injection completion timing of the final injection becomes less
than or equal to the limit crank angle .theta.erst where effective
injection can be performed after engine rotation.
[0114] Moreover, the injection amount of an earlier split injection
may be made greater than that of a later split injection.
[0115] Next, there is described an operation and effect of the
sixth embodiment.
[0116] In this embodiment, an actual engine rotation speed is
detected, and injection is commenced when the engine rotation speed
has increased and the flow velocity of inlet air into the cylinder
has become high. Thereby, there is achieved an effect of promoting
vaporization of the fuel spray and uniformity thereof inside the
cylinder.
[0117] Incidentally, the injection completion timing of the
injection after engine rotation (the final injection when
performing split injections three times or more) needs to be
completed before the inlet stroke is completed. Also in this case,
as with the case of detecting a cylinder which is in an inlet
stroke when automatic stop is performed, for example, even if, as
described later, the inlet valve closing timing is set after the
piston bottom dead center, by a variable valve actuation mechanism,
it is preferable that the injection completion timing of the final
injection after engine rotation, is set at or before the inlet
bottom dead center. However, if there is a state in which the
air-fuel mixture can be sucked into the cylinder after the inlet
bottom dead center, by means of supercharging or the like performed
by a supercharger during cranking, a completion timing of this
suction (timing at which the effect of air-fuel mixture suction
becomes insufficient) may be set as an injection completion timing
in the final injection after engine rotation.
[0118] Hereunder, embodiments which include control of completing
the above injection completion timing in the final injection after
engine rotation, by the time of completion of the inlet stroke are
described, with reference to the flow charts of FIG. 5A to 5D.
[0119] FIG. 5A corresponds to the first embodiment shown in FIG. 2A
in which split injections are performed only before engine
rotation.
[0120] In step S1, it is determined whether the predetermined idle
stop condition described above is satisfied. If satisfied, control
proceeds to step S2 in which fuel injection is stopped in order to
automatically stop the internal combustion engine.
[0121] In step S3, there is executed a process of stabilizing the
engine stop position. Specifically, the engine load (rotational
resistance) is increased, for example, by fully opening the
throttle opening, and thereby the piston position of each cylinder
when the engine is stopped is stopped within a predetermined crank
angle range, thereby suppressing variation in the stop position. As
a result, more stable startability can be ensured. In addition to
the procedure described above, an increase in the engine load can
also be made by controlling; the lift amount and operating angle of
the inlet valve, the valve timing, and the power generation of the
alternator, and on a hybrid vehicle, by controlling the drive
electric motor.
[0122] After engine rotation is stopped in the process of step S3,
in step S4 a cylinder which is in an inlet stroke in a stop state
is determined based on a signal from crank angle sensor 117, and
also the piston position (crank angle position) of the inlet stroke
stopped cylinder is detected, and stored in a backup memory.
[0123] In step S5, it is determined whether the stored crank angle
.theta. of the inlet stroke stopped cylinder (the angle from the
inlet top dead center) is less than or equal to a limit crank angle
.theta.erst' (advanced side). This limit crank angle .theta.erst'
is set as a limit crank angle .theta. at which the fuel spray
within the inlet air passage split-injected before engine rotation
after the engine is automatically stopped by an idle-stop control
can be sufficiently sucked into the cylinder by the time of the
inlet stroke completion after engine rotation. That is to say, even
with the inlet stroke stopped cylinder, if the inlet stroke which
remains after engine rotation is too short, the spray injected into
the inlet air passage before engine rotation cannot be sufficiently
sucked into the cylinder, and consequently it is difficult to
commence a superior restart in this cylinder. Therefore, in this
case, in order to prohibit split injections before engine rotation,
the above determination is performed.
[0124] In step S5, if the crank angle .theta. of the inlet stroke
stopped cylinder is determined to be less than or equal to the
limit crank angle .theta.erst', it is judged that the spray within
the inlet air passage made by the split injection before engine
rotation is sufficiently sucked after engine rotation.
[0125] Therefore, control proceeds to step S6 in which a restart
time injection amount tp is set based on a water temperature, and
this restart time injection amount tp is divided by the split
number n to thereby calculate the injection amount tpn of each
injection. At the same time, a delay time Dspl which serves as the
interval time between the respective split injections is
calculated.
[0126] Next, in step S7, an occurrence of a restart request such as
a depressing operation of the accelerator is determined.
[0127] If it is determined in step S7 that a restart request has
occurred, control proceeds to step S8, and a fuel injection before
engine rotation (first injection) is commenced.
[0128] Subsequently, in step S9, after the injection is completed
in step S8, a second split injection is performed after the delay
time Dspl has elapsed. In a case in which split injection is
performed three times or more, a subsequently split injection is
performed after the delay time Dspl has elapsed after each split
injection is completed, to thereby complete the split injection
before engine rotation.
[0129] In step S10, after the restart request has occurred, the
starter is activated after a predetermined delay time tw has
elapsed, and engine start (cranking) is commenced.
[0130] On the other hand, if the crank angle .theta. of the inlet
stroke stopped cylinder is determined to be greater than the limit
crank angle .theta.erst' (retarded side) in step S5, it is judged
that split injection cannot be performed in this cylinder.
[0131] In this case, control proceeds to step S11 in which a
restart time injection amount is set, and after having determined
the restart request being satisfied in step S12, in step S13, the
set restart time injection amount of fuel is injected at once into
the cylinder which has been stopped in an exhaust stroke.
[0132] FIG. 5B shows a flow of the embodiment in which a single
split injection is respectively performed before and after engine
rotation.
[0133] Step S1 to step S4 are similar to those in FIG. 5A in that
when a predetermined idle stop condition is satisfied, fuel
injection is stopped in order to automatically stop the internal
combustion engine, and after having executed a process of
stabilizing the engine stop position, the inlet stroke stopped
cylinder is determined, and the piston position thereof (crank
angle position) is detected and stored.
[0134] In step S21, it is determined whether the stored crank angle
.theta. of the inlet stroke stopped cylinder is less than or equal
to the limit crank angle .theta.erst at which a split injection, in
particular, an effective injection after engine rotation can be
performed when restarting.
[0135] If it is determined in step S21 that the crank angle .theta.
of the inlet stroke stopped cylinder is less than or equal to the
limit crank angle .theta.erst, control proceeds to step S22.
[0136] In step S22, a fuel injection amount at the time of
restarting (hereunder, referred to as restart time injection
amount) is set based on water temperature, and also use of the
split injection method is determined, and the restart time
injection amount tp is divided by the split number (twice) to
thereby calculate the split injection amount tpn of each
injection.
[0137] As described above, in the second embodiment shown in FIG.
2B, the amount of two split injections tpn is set equal
(tp1=tp2=tp/2), and in the fourth embodiment shown in FIG. 3B, the
first injection amount tp1 (before engine rotation) is set to an
amount greater than the second split injection amount tp2 (after
engine rotation).
[0138] For example, in a case in which the injection commencing
timing of the second split injection is set immediately after
commencement of restarting (cranking), then in accordance with this
setting, a delay time Dspl, which serves as an injection interval
time from the completion of the first injection to the commencement
of the second injection, is initially set as shown in the following
expression.
Dspl=tw-tp1 (3)
[0139] Next, in step S23, in the above split injections, an
injection completion timing .theta.end of the second injection
after engine rotation, which has been found based on the split
injection amounts tp1 and tp2 of the respective injections and the
initial injection interval value (delay time Dspl), is compared
with a limit crank angle (air-fuel mixture suction limit crank
angle) .theta.itend at which the effect of air-fuel mixture suction
can be maintained at an excellent level.
[0140] The air-fuel mixture suction limit crank angle may normally
be the inlet bottom dead center as described above. However, this
may be at the inlet valve closing timing when the inlet valve
closing timing is after the inlet bottom dead center in a case of
performing supercharging with use of a supercharger.
[0141] Moreover, the limit crank angle (limit timing) .theta.itend
may be set based on the operating state of variable valve timing
mechanism 201 and variable valve lift mechanism 112 when the engine
is in a stop state, that is to say, it may be set based on the
closing timing of the inlet valve.
[0142] Furthermore, the air-fuel mixture suction limit crank angle
.theta.itend set based on these may be set as a crank angle on the
advanced side to the inlet bottom dead center or the inlet valve
closing timing described above, with consideration of the delay
from the moment of fuel injection to the moment of introduction
into the cylinder.
[0143] If .theta.end>.theta.itend is determined in step S23, the
delay time Dspl of split injection is reduction-corrected in step
S24 so that .theta.end.ltoreq..theta.itend is satisfied.
Subsequently, control proceeds to step S25 in which it is
determined whether an engine restart request has occurred in a
state in which the engine is automatically stopped.
[0144] By setting the fuel injection amount at the time of
restarting in the automatic stop state in this manner, calculation
delay can be suppressed, fuel injection delay in response to the
restart request can be reduced, and the starting time can be
reduced, thereby improving startability, compared to the case of
calculating a fuel injection amount after a restart request has
been detected.
[0145] If it is determined in step S25 that a restart request has
occurred, control proceeds to step S26, and a fuel injection before
engine rotation stop (first injection) is commenced.
[0146] In step S26, after the restart request has occurred, the
starter is activated after a predetermined delay time tw has
elapsed, and engine start (cranking) is commenced.
[0147] In step S27, after completion of the first injection before
engine rotation, the second fuel injection after engine rotation is
performed after the delay time Dspl has elapsed, and then this
routine ends.
[0148] Here, if step S23 determines at the beginning that
.theta.end.ltoreq..theta.itend is satisfied and the delay time Dspl
is an initially set value, a fuel injection after engine rotation
is commenced, after engine rotation (cranking) has been commenced
by starter activation.
[0149] On the other hand, in a case in which it is determined in
the beginning that .theta.end>.theta.itend is satisfied as shown
in FIG. 6A and the delay time Dspl has been reduction-corrected,
the second injection commencing timing is brought to a earlier
timing as shown in FIG. 6B. Therefore, if the amount of reduction
correction is high, fuel injection is commenced before engine
rotation, and the injection may end after engine rotation in some
cases.
[0150] By making the injection intervals smaller in this way, split
injections are executed in the inlet stroke stopped cylinder to the
greatest possible extent and prompt combustion is commenced, and
thereby the start completion time can be reduced and startability
can be improved.
[0151] Moreover, if the crank angle .theta. of the inlet stroke
stopped cylinder is determined to be greater than the limit crank
angle .theta.erst in step S21 as shown in FIG. 7A, it is judged
that split injection cannot be performed in this cylinder. Then,
control proceeds to step S11 in which a restart time injection
amount is set, and after having determined the restart request
being satisfied in step S12, in step S13, the set restart time
injection amount of fuel is injected into the cylinder which has
been stopped in an exhaust stroke as shown in FIG. 7B.
[0152] If a fuel injection is also performed in a case in which,
even if fuel has been injected into the inlet stroke stopped
cylinder, suction of the injected fuel can be hardly done in the
inlet stroke, and consequently combustion is not performed, then in
the subsequent inlet stroke, a highly concentrated air-fuel mixture
is sucked along with the fuel re-injected in the immediately prior
exhaust stroke, and consequently a misfire may occur, or the
rotation speed may drop due to insufficient output power in some
cases.
[0153] In a case in which injected fuel can be hardly sucked in the
inlet stroke as with the present embodiment, by stopping
(prohibiting) fuel injection into the cylinder, the above misfire
and drop in rotation speed can be suppressed, and startability can
be stabilized.
[0154] FIG. 5C shows a flow of the embodiment in which a split
injection is respectively performed before and after engine
rotation, and the split number n is three times or more.
[0155] Step S1 to step S4, and step S21 are similar to those in
FIG. 5B in that when a predetermined idle stop condition is
satisfied, fuel injection is stopped in order to automatically stop
the internal combustion engine. Then, after having executed a
process of stabilizing the engine stop position, the inlet stroke
stopped cylinder is determined, and the piston position (crank
angle position) thereof is detected and stored. Then, it is
determined whether the crank angle .theta. of the inlet stroke
stopped cylinder is less than or equal to the limit crank angle
.theta.erst at which an effective split injection can be performed
after engine rotation at the time of restarting.
[0156] If it is determined in step S21 that the crank angle .theta.
of the inlet stroke stopped cylinder is less than or equal to the
limit crank angle .theta.erst, use of the split injection method is
determined and control proceeds to step S31. In step S31, a restart
time injection amount tp is set based on water temperature, and a
split number n, a split injection amount tpn of each injection, and
a delay time Dspl which serves as an injection interval time are
calculated based on the crank angle .theta. of the inlet stroke
stopped cylinder.
[0157] Specifically, based on the piston position (crank angle
position) of the inlet stroke stopped cylinder as described above,
an amount of time required from the moment when the restart request
is detected to the moment when the air-fuel mixture suction limit
crank angle .theta.itend is reached is predicted, and the above
respective values are set so that split injections can be completed
within this predicted amount of time.
[0158] In the third embodiment shown in FIG. 3A, the split
injection amount tpn of each injection is set equal (tpn=tp/n), and
the delay time Dspl between the respective split injections is also
set equal. On the other hand, in the fifth embodiment shown in FIG.
4A, it is preferable that the split injection amount tpn is set
higher for an earlier injection, and regarding the delay time Dspl,
this is set higher for an injection interval at earlier timing.
[0159] Subsequently, control proceeds to step S32 in which it is
determined whether an engine restart request has occurred in a
state in which the engine automatically stopped.
[0160] If it is determined in step S32 that a restart request has
occurred, control proceeds to step S33, and a fuel injection before
engine rotation stop (first injection) is commenced.
[0161] In step S34, after completion of the first injection before
engine rotation, the second fuel injection after engine rotation is
performed after the delay time Dspl has elapsed, and subsequently,
there is repeated control in which after completion of each
injection, the next split injection is commenced after the delay
time Dspl has elapsed.
[0162] In step S35, after the restart request has occurred, the
starter is activated after a predetermined delay time tw has
elapsed, and engine start (cranking) is commenced.
[0163] In step S36, also after restarting, there is continued the
control of split injections at the above delay time Dspl intervals,
until injection ends within the air-fuel mixture suction limit
crank angle .theta.itend.
[0164] Moreover, if it is determined in step S21 that the crank
angle .theta. of the inlet stroke stopped cylinder is greater than
the limit crank angle .theta.erst, as with the case of FIG. 5B, it
is judged that split injection cannot be performed in this
cylinder. Then, a restart time injection amount is set in step S11,
and after having determined the restart request being satisfied in
step S12, in step S13, the set restart time injection amount of
fuel is injected into the cylinder which has been stopped in the
exhaust stroke.
[0165] Furthermore, FIG. 5C may be applicable to a configuration in
which a total of two split injections are performed, that is to
say, a single split injection is performed respectively before and
after engine rotation.
[0166] FIG. 5D shows a flow of the embodiment (the fifth embodiment
shown in FIG. 4A) in which the timing of commencing the second
split injection after engine rotation is set at the moment when the
engine rotation speed reaches a predetermined value.
[0167] Step S1 to step S4 are similar to those in FIG. 5A to FIG.
5C in that when a predetermined idle stop condition is satisfied,
fuel injection is stopped in order to automatically stop the
internal combustion engine, and after having executed a process of
stabilizing the engine stop position, the inlet stroke stopped
cylinder is determined and the piston position thereof (crank angle
position) is detected and stored.
[0168] In step S41, in a case in which the crank angle .theta. of
the inlet stroke stopped cylinder is such that the second split
injection is commenced when the engine rotation speed Ne has
reached a predetermined value Ne0 after restarting, it is
determined whether this split injection can be completed within the
air-fuel mixture suction limit crank angle .theta.itend.
[0169] If it is determined that the injection can be completed
within the air-fuel mixture suction limit crank angle .theta.itend,
control proceeds to step S42 to perform split injections.
[0170] In step S42, a restart time injection amount and a split
injection amount are set.
[0171] If it is determined in step S43 that a restart request has
occurred, control proceeds to step S44, and a fuel injection before
engine rotation stop (first injection) is commenced.
[0172] In step S45, after the restart request has occurred, the
starter is activated after a predetermined delay time tw has
elapsed, and engine start (cranking) is commenced.
[0173] In step S46, it is determined whether the engine rotation
speed Ne has reached the predetermined value Ne0 or a greater value
after the engine has been restarted. The predetermined value Ne0 is
set to a value at which the inlet air flow velocity in the cylinder
has increased due to the increase in the engine rotation speed Ne,
and the effect of in-cylinder diffusion of the injected spray is
high.
[0174] In step S46, if it is determined that the engine rotation
speed Ne has reached the predetermined value Ne0 or a greater
value, control proceeds to step S47 and the second split injection
is commenced.
[0175] On the other hand, in step S41, in a case in which the
second split injection is commenced at an engine rotation speed Ne
greater than or equal to the predetermined value Ne0, if it is
determined that this injection may not be completed within the
air-fuel mixture suction limit crank angle .theta.itend, a restart
time injection amount is set in step S11, and after having
determined the restart request being satisfied in step S12, in step
S13, the set restart time injection amount of fuel is injected into
the cylinder which has been stopped in the exhaust stroke.
[0176] Moreover, control may proceed to step S21 and the subsequent
steps of FIG. 5B if the second split injection has been commenced
at an engine rotation speed Ne greater than or equal to the
predetermined value Ne0 in step S41. In this case, if the crank
angle .theta. of the inlet stroke stopped cylinder is less than or
equal to the limit crank angle .theta.erst, split injections can be
executed.
[0177] FIG. 5E shows a flow of a seventh embodiment in which a
restart request after a warm-up completion is judged, and fuel
injection control at the time of restarting is executed as
described in the respective embodiments of FIG. 5A to FIG. 5D.
[0178] In step S51, it is determined whether a start commencing
operation has been performed by an engine start switch (such as an
ignition switch or a push-type start button).
[0179] If no start commencing operation has been performed, control
proceeds to step S57 in which it is determined whether the engine
is stopped by an OFF operation of the engine start switch. If YES,
control proceeds to step S58 in which the cylinder in the inlet
stroke is determined based on a signal from the crank angle sensor
117 in an engine stop state, and the piston position of the inlet
stroke stopped cylinder (crank angle position) is detected and
stored into the backup memory. If the determination result of step
S57 is NO, this flow ends.
[0180] On the other hand, if it is determined in step S51 that a
start commencing operation has been performed by the engine start
switch, control proceeds to step S52 and detection values of engine
temperature (engine cooling water temperature, lubricating oil
temperature, and the like) are read.
[0181] In step S53, it is determined whether the engine temperature
is below the warm-up completion temperature.
[0182] If it is determined as being a low-temperature start at an
engine temperature below the warm-up completion temperature,
control proceeds to step S54 in which the starter is activated to
commence cranking, and a cylinder determination is performed based
on a signal from the crank angle sensor 117. This cylinder
determination is performed in a manner such that the result stored
in step S58 is cleared and a determination is made again.
[0183] Since the vaporizability of fuel becomes lower and the
amount of fuel which becomes attached to the inlet air passage wall
increases when the engine temperature is lower, in step S55, the
fuel injection amount is increase-corrected and fuel injection is
executed in the exhaust stroke (normal low-temperature injection
amount control).
[0184] On the other hand, if it is determined in step S54 that the
engine temperature is greater than or equal to the warm-up
completion temperature, a warm-up start is performed under a
condition similar to that at the time of restarting after an idle
stop, and therefore there is performed control similar to any one
of the respective embodiments shown in FIG. 5A to FIG. 5D (step S5
and subsequent steps in FIG. 5A, step S21 and subsequent steps in
FIGS. 5B and 5C, and step S41 and subsequent steps in FIG. 5D).
[0185] According to the seventh embodiment, also at the time of
performing warm-up start with an engine start switch operation
performed by the driver, there is obtained the operation and effect
of the corresponding embodiment among the first to sixth
embodiments described above.
[0186] Moreover, although the seventh embodiment may be practiced
in combination with the first to sixth embodiments at the time of a
start request after automatic stop is performed, the seventh
embodiment can of course be independently practiced on a vehicle in
which automatic stop such as idle stop is not performed.
[0187] In the embodiment described above, split injections can be
easily performed a plurality of number of times before engine
rotation, by setting a split number n1 before engine rotation, each
split injection amount tpn1, and a delay time Dspl1 with respect to
the injection amount before engine rotation. Split injections after
engine rotation may also be performed a plurality of number of
times, and a split number n2 after engine rotation, each split
injection amount tpn2, and a delay time Dspl2 are similarly set
with respect to the injection amount after engine rotation.
Furthermore, when the engine rotation speed Ne has reached the
predetermined value Ne0 and injection has been commenced in step
S41, it may be determined whether the final injection can be
completed within the air-fuel mixture suction limit crank angle
.theta.itend, and it may be executed if this injection completion
is possible.
[0188] Furthermore, in the above embodiment, when a split injection
is performed in the initial cycle for the inlet stroke stopped
cylinder, at the same time, the restart time injection amount of
fuel is injected into the cylinder stopped in the exhaust stroke
immediately after a restart request has been made. Subsequently,
injection is commenced for the cylinder in the exhaust stroke at a
predetermined injection commencing timing. However the control is
switched after the second cycle, or once engine rotation has been
stabilized after a complete explosion, so that the injection
completion timing becomes constant.
[0189] Moreover, as has been described, an injection before engine
rotation contributes to cooling of air inside the inlet port while
an injection after engine rotation contributes to uniformity of
air-fuel mixture inside the cylinder, and these injections
respectively have an effect of suppressing pre-ignition.
Consequently, with a long stroke engine or an engine having a
tumble control valve added thereto and having a comparatively high
gas flow and a high level of air-fuel mixture uniformity in the
cylinders, the entire injection amount may be split-injected only
before engine rotation as with the first embodiment. Moreover, with
an engine in which the injection amount before engine rotation is
made relatively high to enhance the cooling capability, and
air-fuel mixture uniformity in the cylinders is low, the injection
amount after engine rotation may be made relatively high so as to
enhance the uniformity.
[0190] Furthermore, in order to improve startability, there may
also be used in combination a control in which the inlet valve
closing timing is controlled to a most retarded position to reduce
the compression pressure, using variable valve timing mechanism 201
at the time of idle stop.
[0191] FIG. 8 shows a flow chart of valve closing timing control of
the above inlet valve.
[0192] In step S101, it is determined whether an idle stop
condition is satisfied. If satisfied, control proceeds to step S102
in which the valve timing of the inlet valve is made most retarded
by variable valve timing mechanism (VTC) 201, thereby executing
control to make inlet valve closing timing (IVC) retarded to the
greatest possible extent.
[0193] Moreover, in a case of mechanically driving to be most
retarded, by stopping power distribution to a control actuator of
variable valve timing mechanism 201, power distribution to the
control actuator may be stopped to thereby shift the valve timing
of the inlet valve to the most retarded side.
[0194] Furthermore, it is preferable that variable valve lift
mechanism 112 executes control so that the lift amount and
operating angle of the inlet valve are on the greater side (where
the lift amount is maximum for example).
[0195] Here, by using the most retard control of the valve timing
performed by variable valve timing mechanism 201 in combination
with the inlet valve operating angle control of variable valve lift
mechanism 112, IVC can be made further retarded, and it becomes
possible to expand the range of IVC control required for
pre-ignition suppression.
[0196] In this case, the control actuator of variable valve lift
mechanism 112 is driven until at least the engine is stopped, and
thereby the high lift amount side of the inlet valve is
retained.
[0197] Moreover, power distribution may be performed even when the
engine is in the stop state, in order to continue to drive the
control actuator of variable valve lift mechanism 112. Furthermore,
power distribution may be stopped when the engine has been stopped
and it may be restored when an automatic start request is made.
[0198] In step S103, it is determined whether the valve timing of
the inlet valve has been shifted to the most retarded position by
variable timing mechanism 201, and this control continues to be
performed until it is determined as having been shifted.
[0199] Whether or not the valve timing of the inlet valve has been
shifted to the most retarded position can be determined when the
actual advance displacement amount of variable valve timing
mechanism 201 takes a value showing the most retarded position.
This actual advance displacement amount can be calculated based on
the rotational phase difference between the inlet cam shaft and the
crank shaft.
[0200] After the engine has been stopped in step S104, a restart
request occurs due to the determination in step S105, and the
restart control described above is performed.
[0201] Then, in step S106, if the start completion is determined
(for example, when the start switch is OFF and the engine rotation
speed has reached a value corresponding to a complete explosion),
in step S107, the control of bringing the valve timing of the inlet
valve to the most retarded position is released, and the control is
switched to employ a target valve timing of the inlet valve, which
is set based on the engine operating state.
[0202] FIG. 9 shows a time chart of the above IVC control.
[0203] When the accelerator opening is reduced and the engine
operation is brought to a deceleration idle state in which idle
switch 116a is turned ON, the target value of the valve timing
control of the inlet valve performed by variable valve timing
mechanism (VTC) 201 is set to a retarded value according to the
deceleration idle state, and the valve timing is retard-controlled
so as to approach this target value.
[0204] Moreover, the target values of the lift amount and of the
operating angle control of the inlet valve performed by variable
valve lift mechanism (VEL) 112 are also set to values at which the
operating angle is reduced according to the deceleration idle
state, and a reduction-control is performed so that the lift amount
and the operating angle approach these target values.
[0205] With these retardation control and reduction control of the
lift amount and the operating angle of the inlet valve, the inlet
valve opening timing is retarded, and the amount of valve
overlapping with the exhaust valve is reduced. Consequently,
combustion characteristics in the deceleration idle state can be
maintained at a superior level.
[0206] When the vehicle traveling speed is reduced by the
deceleration idle state, to a speed below an idle stop
determination vehicle traveling speed, and the idle stop condition
is satisfied, the pre-ignition avoidance control is commenced as
described above. As a result, the target value of the valve timing
control of the inlet valve performed by variable valve timing
mechanism (VTC) 201 is set to the most retarded position, and
control is performed so that valve timing approaches the most
retarded position.
[0207] On the other hand, in a case in which as described above,
the pre-ignition avoidance control with variable valve lift
mechanism 112 is used in combination, the target value is set so
that the lift amount and operating angle of the inlet valve are on
the greater side (where the lift amount is maximum for example),
and increase-control is performed so that the lift amount and the
operating angle approach the target values.
[0208] The most retard control of the valve timing of the inlet
valve performed by variable valve timing mechanism 201 continues to
be performed until the most retarded position, which is the target
value, is determined as being reached. Moreover, in a case in which
the pre-ignition avoidance control performed by variable valve lift
mechanism 112 is used in combination, the control continues to be
performed until it is determined that the lift amount and operating
angle of the inlet valve have reached the target values. However,
power distribution may be performed even when the engine is in a
stop state in order to continue to drive the control actuator
(state shown in the diagram), or power distribution may be stopped
when the engine has been stopped and it may be restored when an
automatic start request is made.
[0209] After the engine is stopped as described above, when an
increase in the accelerator opening caused by a depressing
operation of the accelerator pedal is detected and a restart
request occurrence is detected, the start switch is turned ON and
restarting (cranking) is commenced. As a result, when the engine
rotation speed reaches a predetermined value or higher and causes
the starter switch to turn OFF, and the engine rotation speed has
reached a value corresponding to a complete explosion and start
completion is determined, the most retard control of the valve
timing of the inlet valve performed by variable valve mechanism 201
is released. Moreover, in a case in which the increase-control of
the valve timing of the inlet valve performed by the variable valve
lift mechanism 112 is used in combination, this control is also
released and the control is switched to employ new target values,
which are respectively set based on the engine operating state.
[0210] If there is performed the most retard control of the valve
timing of the inlet valve performed by variable valve timing
mechanism 201, or control which combines the most retard control of
the valve timing of the inlet valve performed by variable valve
timing mechanism 201 with the increase-control of the lift amount
and operating angle of the inlet valve performed by variable valve
lift mechanism 112, the inlet valve closing timing (IVC) is in a
most retarded position at the time of restarting after the idle
stop has been released. As a result compression pressure is reduced
and startability of the engine can be further improved.
[0211] Furthermore, there is a fuel injection valve in which sprays
injected from a plurality of injection nozzles are made to impinge
on each other to thereby promote atomization of the fuel (refer to
Japanese Patent No. 4099075).
[0212] The relevant parts structure and operation of the above fuel
spray impingement type fuel injection valve is described, with
reference to the drawings.
[0213] As shown in FIG. 10A to FIG. 100, a nozzle plate 18 provided
so as to cover an injection nozzle 8C on a valve seat member 8
includes; a flat plate section 18A which is formed in a disk shape
by applying press-working to a metallic plate for example, and a
cylinder section 18B which is formed bent in a substantially L
shape toward the outer periphery side of the flat plate section
18A.
[0214] Flat plate section 18A is joined with the tip end surface of
valve seat member 8 by a welding section 19, and cylinder section
18B is joined with the inner circumferential surface of a small
diameter cylinder section 2B of a valve casing 2 by a welding
section 20.
[0215] A plurality of nozzle holes 21 provided in flat plate
section 18A of nozzle plate 18 are provided in a total of 12
locations in the center of flat plate section 18A as shown in FIG.
100 and FIG. 10D for example, and fuel inside casing 1 is injected
therefrom when a valve body 9 is open.
[0216] Here, the respective nozzle holes 21 form six nozzle hole
pairs 22, 23, 24, 25, 26, and 27 respectively having a pair of two
adjacent nozzle holes 21A and 21B, and nozzle hole pairs 22, 23,
and 24 and nozzle hole pairs 25, 26, and 27 are arranged
line-symmetric about the X-X axis which passes through the center
of nozzle plate 18. First nozzle hole pairs 22 and 25 among these
nozzle hole pairs 22, 23, 24, 25, 26, and 27 are arranged along the
X-X axis in the vicinity of the X-X axis as shown in FIG. 10D, and
second nozzle hole pairs 23, 24, 26, and 27 are arranged in
positions different in the circumferential direction of nozzle
plate 18 from those of first nozzle hole pairs 22 and 25 and
distanced from the X-X axis further than first nozzle hole pairs 22
and 25 to the outer periphery side of nozzle plate 18.
[0217] Nozzle holes 21A and 21B which form the respective nozzle
hole pairs 22 to 27 are of a configuration such that as shown in
FIG. 10E, the hole centers A-A and B-B thereof are respectively
inclined only by an angle .theta. with respect to the Y-Y axis
orthogonal to flat plate section 18A of nozzle plate 18, and they
intersect with each other in a V shape about the Y-Y axis.
[0218] As a result, each of nozzle hole pairs 22 to 27 is
configured as an impingement type nozzle hole pair in which
injection flows of fuel injected from the respective nozzle holes
21A and 21B in the direction shown with arrows F impinge on each
other on the forward side in the injection directions. The spray of
fuel after the impingement caused by first nozzle hole pairs 22 and
25 forms spray patterns 28 and 31 shown in FIG. 10D. Moreover, the
spray of fuel after the impingement caused by second nozzle hole
pairs 23, 24, 26, and 27 form other spray patterns 29, 30, 32, and
33, the spraying directions of which are different from those of
spray patterns 28 and 31 formed by first nozzle hole pairs 22 and
25.
[0219] Nozzle hole pairs 22 to 27 atomize the fuel by causing the
injection flows of fuel injected from nozzle holes 21A and 21B to
impinge on each other, and inject this fuel to the outside in spray
patterns 28, 29, 30, 31, 32, and 33 shown in FIG. 10D. At this
time, spray patterns 28, 29, 30, 31, 32, and 33 respectively have
different spraying directions so as to be line-symmetric about the
X-X axis as shown in FIG. 10D.
[0220] Here, in this embodiment, as shown in FIG. 10E, the
dimensional ratio t/d between the plate thickness t of nozzle plate
18 (flat plate section 18A) and the hole diameter d of nozzle holes
21A and 21B is set so as to satisfy a relationship
t/d.gtoreq.1.0.
[0221] As a result, the length L of nozzle holes 21A and 21B
provided in nozzle plate 18 can be made long, so that straight
progression of the injection flow can be ensured when injecting
fuel in the arrow F direction from each of nozzle holes 21A and
21B.
[0222] Therefore, in the provided configuration, atomization of the
fuel can be promoted by making the injection flows injected from
nozzle holes 21A and 21B of the respective nozzle hole pairs 22 to
27 appropriately impinge on each other, and spray patterns 28 to 33
from nozzle hole pairs 22 to 27 can be expanded extensively.
[0223] With use of this spray impingement type fuel injection
valve, impingement between sprays promotes fuel atomization and the
spray patterns expand extensively, and consequently the penetration
force becomes reduced. Therefore, the atomized fuel spray, in
particular, the fuel spray injected before engine rotation in the
inlet stroke stopped cylinder, efficiently cools the inlet port
wall and the air-fuel mixture within the inlet port while spray
adhesion to the inlet valve is being suppressed, and the cooling
effect thereof within a cylinder when sucked into the cylinder can
be increased and the effect of suppressing pre-ignition can be
increased.
[0224] Moreover, atomization of the fuel can be further promoted by
increasing the fuel pressure supplied to the fuel injection valve
at the time of restarting.
[0225] FIG. 11 shows a flow of a relevant part of a fuel pressure
raising control at the time of restarting. In step S9 in the flow
chart of FIG. 5A, when a restart request occurrence has been
determined, control proceeds to step S21 and fuel pressure raising
control is executed. For example, it is possible to raise the fuel
pressure to be supplied to the fuel injection valve by increasing
pump rotation speed from that at the time of idle operating by
changing the battery, which supplies electric power to an electric
fuel pump (not shown in the drawing), from normal lead battery 121
to lithium-ion battery 122.
[0226] Next, in step S22, it is determined whether the actual fuel
pressure detected by a fuel pressure sensor (not shown in the
drawing) has reached a target fuel pressure. After it has been
reached, control proceeds to step S10 and the first fuel injection
before engine rotation is executed in the inlet stroke stopped
cylinder. Other steps are similar to those in FIG. 5A.
[0227] Furthermore, when automatically stopping the internal
combustion engine, if fuel pressure raising control is performed
before the engine is stopped, to increase the fuel pressure within
the fuel tubing, the amount of time required for the fuel pressure
to reach the target fuel pressure is reduced when performing the
fuel pressure raising control at the time of restarting, and the
commencement of the first injection before engine rotation can be
performed earlier, accordingly allowing prolonged vaporization
time.
[0228] Although not shown in the drawing, fuel consumption may be
improved by changing the fuel pump power supply source to a lead
battery to reduce the fuel pressure to the normal fuel pressure,
after starting has been completed (complete explosion).
[0229] If this fuel pressure raising control at the time of
restarting is used in combination with the spray impingement type
fuel injection valve, improved atomization increases the cooling
effect within the cylinder and the effect of suppressing
pre-ignition can be further increased. However, even if this is
applied to a system which uses a normal fuel injection valve
(non-spray-impingement type), it is of course possible to increase
the effect of suppressing pre-ignition.
[0230] The entire contents of Japanese Patent Application No.
2009-282946 filed on Dec. 14, 2009 a priority of which is claimed,
are incorporated herein by reference.
[0231] While only selected embodiments have been chosen to
illustrate and describe the present invention, it will be apparent
to those skilled in the art from this disclosure that various
changes and modifications can be made herein without departing from
the scope of the invention as defined in the appended claims.
[0232] Furthermore, the foregoing description of the embodiments
according to the present invention is provided for illustration
only, and not for the purpose of limiting the invention as defined
by the appended claims and their equivalents.
* * * * *