U.S. patent application number 09/734611 was filed with the patent office on 2001-08-16 for control apparatus and method for internal combustion engine with variably operated engine valve.
Invention is credited to Arai, Masahiro, Kawasaki, Takao.
Application Number | 20010013322 09/734611 |
Document ID | / |
Family ID | 18448844 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010013322 |
Kind Code |
A1 |
Arai, Masahiro ; et
al. |
August 16, 2001 |
Control apparatus and method for internal combustion engine with
variably operated engine valve
Abstract
In control apparatus and method for an internal combustion
engine having variably operated engine valves, a target vacuum
pressure is calculated on the basis of an engine driving condition
and an opening angle of an electronically controlled throttle valve
is disposed in an intake air passage to achieve the target vacuum
pressure. A target air quantity to be sucked within an engine
cylinder on the basis of the engine driving condition is calculated
and a valve closure timing of an intake valve of, e.g., an
electromagnetic operation type is controlled to achieve the target
air quantity. At this time, in accordance with the target vacuum
pressure TBOOST(or in accordance with an actual vacuum pressure
BOOST detected by means of a vacuum pressure sensor), the target
air quantity to calculate the valve closure timing of the intake
valve calculated on the basis of target air quantity is corrected
or the intake valve closure timing IVC per se is corrected by a
correction value of AIVC.
Inventors: |
Arai, Masahiro; (Yokohama,
JP) ; Kawasaki, Takao; (Kanagawa, JP) |
Correspondence
Address: |
FOLEY & LARDNER
Washington Harbour
Suite 500
3000 K Street, N.W.
Washington
DC
20007-5109
US
|
Family ID: |
18448844 |
Appl. No.: |
09/734611 |
Filed: |
December 13, 2000 |
Current U.S.
Class: |
123/90.11 |
Current CPC
Class: |
F02D 2041/001 20130101;
F02D 13/0234 20130101; Y02T 10/12 20130101; F02D 2041/002 20130101;
F02D 13/0207 20130101; F02D 2250/18 20130101; Y02T 10/18 20130101;
F02D 41/083 20130101; F02D 13/0253 20130101 |
Class at
Publication: |
123/90.11 |
International
Class: |
F01L 009/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 15, 1999 |
JP |
11-356401 |
Claims
What is claimed is:
1. A control apparatus for an internal combustion engine,
comprising: a variably operated intake valve enabled for its
open-and-closure operation to be arbitrarily controlled; a target
air quantity calculating section that calculates a target air
quantity to be sucked into an engine cylinder on the basis of an
engine driving condition; a target vacuum pressure calculating
section that calculates a target vacuum pressure on the basis of
the engine driving condition; a throttle valve controlling section
that controls a throttle valve disposed in an intake air passage of
the engine to achieve the target vacuum pressure; and an intake
valve open-and-closure timing controlling section that calculates
and controls valve open and closure timings of the variably
operated intake valve to achieve the target air quantity, the valve
closure timing of the intake valve being varied in accordance with
a vacuum pressure developed within a portion of the intake air
passage which is located downstream to the throttle valve.
2. A control apparatus for an internal combustion engine as claimed
in claim 1, wherein the intake valve open-and-closuring timing
controlling section corrects the valve closure timing of the intake
valve in accordance with the target vacuum pressure so that the
valve closure timing of the intake valve is varied.
3. A control apparatus for an internal combustion engine as claimed
in claim 1, further comprising a vacuum pressure sensor to detect
an actual vacuum pressure of the portion of the intake air passage
which is located downstream to the throttle valve and wherein the
intake valve open-and-closure timing controlling section that
corrects the intake valve closure timing in accordance with the
actual vacuum pressure so that the valve closure timing of the
intake valve is varied.
4. A control apparatus for an internal combustion engine as claimed
in claim 1, wherein the intake valve open-and-closure timing
controlling section corrects the target air quantity so that the
valve closure timing of the intake valve is varied.
5. A control apparatus for an internal combustion engine as claimed
in claim 1, wherein the intake valve open-and-closure timing
controlling section corrects the valve closure timing of the intake
valve per se calculated on the basis of the target air quantity in
accordance with either an actual vacuum pressure within the portion
of the intake passage which is located downstream to the throttle
valve or the target pressure to be developed therewithin.
6. A control apparatus for an internal combustion engine as claimed
in claim 1, wherein the throttle valve is an electronically
controlled throttle valve.
7. A control apparatus for an internal combustion engine as claimed
in claim 2, further comprising a vacuum pressure request section
that determines whether a request to strengthen the vacuum pressure
is established and wherein the target vacuum pressure is calculated
in accordance with the engine coolant temperature.
8. A control apparatus for an internal combustion engine as claimed
in claim 7, further comprising an engine coolant temperature sensor
to detect an engine coolant temperature and wherein the target
vacuum pressure calculating section calculates the target vacuum
pressure in accordance with the engine coolant temperature.
9. A control apparatus for an internal combustion engine as claimed
in claim 8, wherein as the engine coolant temperature becomes
lower, the target vacuum pressure becomes larger.
10. A control apparatus for an internal combustion engine as
claimed in claim 8, wherein when the request is not established,
the target vacuum pressure calculating section calculates the
target vacuum pressure according to the engine coolant temperature
by referring a fist table and when the request is established, the
target vacuum pressure is calculated according to the engine
coolant temperature by referring to a second table.
11. A control apparatus for an internal combustion engine as
claimed in claim 7, wherein the target vacuum pressure when the
request is established is larger than the target vacuum pressure
when the request is not established.
12. A control apparatus for an internal combustion engine as
claimed in claim 7, wherein the request is established when a
blow-by gas ventilation demands to develop the vacuum pressure.
13. A control apparatus for an internal combustion engine as
claimed in claim 7, wherein the request is established when a
vaporized fuel purge system demands to develop the vacuum
pressure.
14. A control apparatus for an internal combustion engine as
claimed in claim 7, wherein the request is established when a
master brake booster of a vehicular brake system demands to develop
the vacuum pressure.
15. A control apparatus for an internal combustion engine as
claimed in claim 2, wherein the valve closure timing of the intake
valve is corrected to be set toward a direction of a bottom dead
center during a suction stroke as the vacuum pressure is
increased.
16. A control apparatus for an internal combustion engine as
claimed in claim 5, wherein as the actual vacuum pressure becomes
larger, a correction value for the valve closure timing of the
intake valve becomes larger.
17. A control apparatus for an internal combustion engine as
claimed in claim 4, wherein as a post-correction target air
quantity after the correction of the target air quantity becomes
larger, the valve closure timing of the intake valve is set toward
a direction of a bottom dead center during a suction stroke.
18. A control apparatus for an internal combustion engine as
claimed in claim 1, the valve open-and-closure timing controlling
section controls the valve openand-closure timing of the intake
valve according to the corrected valve closure timing of the intake
valve.
19. A control apparatus for an internal combustion engine as
claimed in claim 1, wherein the variably operated intake valve
comprises a pair of springs to bias the intake valve toward a
neutral position; a first electromagnet to attract a movable
element associated with a valve stem of the intake valve thereonto
to displace the intake valve toward a closure position of the
intake valve when energized; and a second electromagnet to attract
the movable element thereonto to displace the intake valve toward
an open position of the intake valve when energized.
20. A control method for an internal combustion engine, comprising:
providing a variably operated intake valve enabled for its
open-and-closure operation to be arbitrarily controlled;
calculating a target air quantity to be sucked into an engine
cylinder on the basis of an engine driving condition; calculating a
target vacuum pressure on the basis of the engine driving
condition; calculating an opening of a throttle valve disposed in
an intake air passage of the engine to achieve the target vacuum
pressure; controlling the opening of the throttle valve in
accordance with a result of calculation of the opening of the
throttle valve; calculating valve open and closure timings of the
variably operated intake valve to achieve the target air quantity;
and controlling the valve closure timing of the variably operated
intake valve in accordance with a result of calculation of the
valve closure timing of the intake valve, the controlled valve
closure timing of the intake valve being varied in accordance with
a vacuum pressure developed within a portion of the intake air
passage which is located downstream to the throttle valve.
21. A control apparatus for an internal combustion engine as
claimed in claim 1, wherein the throttle control section comprises
to calculate a target vacuum pressure coefficient on a basis of the
target vacuum pressure, calculate an A/NV value corresponding to
the target vacuum pressure correction coefficient, wherein the A/NV
value representing an opening area of the throttle valve divided by
a product between an engine speed and an engine displacement,
calculate a throttle valve opening calculation coefficient on a
basis of the A/NV value corresponding to the target vacuum pressure
correction coefficient and the target vacuum pressure, calculate a
vacuum pressure controlling A?NV value on a basis of the throttle
valve opening calculation coefficient and the target air quantity,
and calculate a target opening of the throttle valve based on the
vacuum pressure controlling A/NV value, the engine speed and the
engine displacement, wherein the throttle valve being controlled to
the target opening of the throttle valve.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the invention
[0002] The present invention relates generally to control apparatus
and method for an internal combustion engine with variably operated
engine valves in which a variable valve drive unit through which an
open-and-closure operation of one of the engine valves, viz., an
intake valve is arbitrarily controllable is installed and which
controls a closure timing of an intake valve to regulate an air
quantity sucked into an engine cylinder.
[0003] 2. Description of the related art:
[0004] A Japanese Patent Application First Publication No. Heisei
11-117777 published on Apr. 27, 1999 (which corresponds to a U.S.
Pat. No. 6,039,026 issued on Mar. 21, 2000) exemplifies a
previously proposed electromagnetically operated engine valve
open-and-closure timing controlling apparatus for an internal
combustion engine.
[0005] In the previously proposed electromagnetically operated
engine valve open-and-closure timing controlling apparatus,
open-and-closure operation of engine valves, for example, an intake
valve can arbitrarily be controlled using variably operated engine
valve drive mechanisms and an intake air quantity sucked into a
corresponding engine cylinder is controlled by varying a valve
closure timing of the intake valve, with the intake valve closure
at a time point when a piston reaches to an intake stroke bottom
dead center as a latest valve closure timing (so called, an earlier
valve closure timing control).
[0006] Since such an electromagnetically operated valve
open-and-closure timing controlling apparatus as described above
has an object of an improvement in a fuel consumption through a
non-throttle drive (viz., a state wherein an engine throttle valve
of an electronic control type is at a full open state)
(also-called, a reduction in a pumping loss), the engine is
basically driven, an air pressure within an intake air passage
being equivalent to the atmospheric pressure. An air quantity to be
sucked within the cylinder is controlled by a cylinder volume at
the time point of the closure of the intake valve.
SUMMARY OF THE INVENTION
[0007] In order to cope with an occurrence in a request to develop
a vacuum pressure in the engine during a low engine coolant
temperature, from a purge system of vaporized fuel, from a blow-by
gas ventilation system, and/or from a brake master vac.(a brake
booster of a master cylinder of a vehicular brake system), it is
often necessary for the electromagnetically operated engine valve
open-and-closure timing controlling apparatus to further control a
position of the electronically controlled throttle valve to develop
a desired vacuum pressure within a portion of the intake air
passage located downstream to the throttle valve.
[0008] While the air quantity to be sucked into the engine cylinder
is controlled according to the valve closure timing of the intake
valve, the air quantity is controlled according to a cylinder
volume at the time of closure of the intake valve. Hence, in a case
where a pressure variation occurs within the intake air passage, an
air density is accordingly varied so that an intake air mass within
the corresponding engine cylinder is also varied. Especially, in a
case where a target vacuum pressure is variably controlled in
response to the occurrence in the request to develop the vacuum
pressure, the previously proposed electromagnetically operated
engine valve open-and-closure timing controlling apparatus
described in the Background of the Invention cannot cope with such
a pressure variation as described above in the intake air
passage.
[0009] It is therefore an object of the present invention to
provide control apparatus and method for an internal combustion
engine which can achieve a cylinder intake air mass which meets
with a demanding torque irrespective of a variation in air pressure
within a portion of an intake air passage located downstream to an
electronically controlled throttle valve even if a desired vacuum
pressure is provided in an intake air passage while performing an
air quantity control through a variably operated engine valve and
which can improve a control accuracy of intake air quantity.
[0010] According to one aspect of the present invention, there is
provided a control apparatus for an internal combustion engine,
comprising: a variably operated intake valve enabled for its
open-and-closure operation to be arbitrarily controlled; a target
air quantity calculating section that calculates a target air
quantity to be sucked into an engine cylinder on the basis of an
engine driving condition; a target vacuum pressure calculating
section that calculates a target vacuum pressure on the basis of
the engine driving condition; a throttle valve controlling section
that controls a throttle valve disposed in an intake air passage of
the engine to achieve the target vacuum pressure; and an intake
valve open-and-closure timing controlling section that calculates
and controls valve open and closure timings of the variably
operated intake valve to achieve the target air quantity, the valve
closure timing of the intake valve being varied in accordance with
a vacuum pressure developed within a portion of the intake air
passage which is located downstream to the throttle valve.
[0011] According to another aspect of the present invention, there
is provided a control method for an internal combustion engine,
comprising: providing a variably operated intake valve enabled for
its open-and-closure operation to be arbitrarily controlled;
calculating a target air quantity to be sucked into an engine
cylinder on the basis of an engine driving condition; calculating a
target vacuum pressure on the basis of the engine driving
condition; calculating an opening of a throttle valve disposed in
an intake air passage of the engine to achieve the target vacuum
pressure; controlling the opening of the throttle valve in
accordance with a result of calculation of the opening of the
throttle valve; calculating valve open and closure timings of the
variably operated intake valve to achieve the target air quantity;
and controlling the valve closure timing of the variably operated
intake valve in accordance with a result of calculation of the
valve closure timing of the intake valve, the controlled valve
closure timing of the intake valve being varied in accordance with
a vacuum pressure developed within a portion of the intake air
passage which is located downstream to the throttle valve.
[0012] This summary of the invention does not necessarily describe
all necessary features so that the invention may also be a
sub-combination of these described features.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1A is a rough system configuration view of an internal
combustion engine to which a control apparatus of a first preferred
embodiment according to the present invention is applicable.
[0014] FIG. 1B is a schematic circuit block diagram of a controller
shown in FIG. 1A.
[0015] FIG. 2 is a basic conceptual diagram of an electromagnetic
type variably operated engine valve applicable to intake and
exhaust valves of the engine shown in FIG. 1A.
[0016] FIG. 3 is an operational flowchart representing a
calculation of a target air quantity.
[0017] FIG. 4 is an operational flowchart representing a
calculation-and-control procedure of a valve open-and-closure
timing executed in the controller shown in FIG. 1A.
[0018] FIG. 5 is an operational flowchart representing a
calculation-and-control procedure of a valve open-and-closure
timing executed in the controller shown in FIG. 1A.
[0019] FIG. 6 is a rough configuration view of the internal
combustion engine to which the control apparatus in a second
preferred embodiment according to the present invention is
applicable.
[0020] FIG. 7 is an operational flowchart representing a
calculation-and-control procedure of the valve open-and-closure
timing of the intake valve in a case of the second preferred
embodiment of the control apparatus shown in FIG. 6.
[0021] FIG. 8 is an operational flowchart representing the
calculation-and-control procedure of the valve open-and-closure
timing in a case of a third preferred embodiment of the control
apparatus.
[0022] FIG. 9 is a characteristic graph representing a QHO versus
A/NV characteristic when a cylinder volume is 100%.
[0023] FIG. 10 is a characteristic graph representing the QHQ
versus A/NV characteristic when a valve closure timing of the
intake valve is varied.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] Reference will hereinafter be made to the drawings in order
to facilitate a better understanding of the present invention.
[0025] FIG. 1A shows a rough configuration view of an internal
combustion engine to which a control apparatus in a first preferred
embodiment according to the present invention is applicable.
[0026] FIG. 1B shows a schematic circuit block diagram of a
controller shown in FIG. 1A.
[0027] In FIG. 1A, electromagnetically operated intake valve 5 and
exhaust valve 6 are disposed on a cylinder head so as to enclose a
spark plug 4 in a combustion chamber 3 defined by means of a piston
2 of each cylinder of the engine 1.
[0028] In FIG. 1A, an intake air passage 7 and an exhaust passage 8
are disposed in the engine 1.
[0029] FIG. 2 shows a basic conceptual structure of an
electromagnetic valve drive unit and integrated engine valve for a
corresponding one of the intake and exhaust valves 5 and 6 shown in
FIG. 1A.
[0030] A plate-like armature 22 is integrally attached onto a valve
axle 21 of a valve body 20 to form a movable element. The armature
22 is biased at a neutral position between a full open position of
valve body 20 with respect to a valve seat and a full closure
position thereof by means of pair of springs 23 and 24.
[0031] A valve opening electromagnet 25 is disposed at a lower
position so as to face vertically toward a rear end of the movable
element 22 and a valve closing electromagnet 26 is displaced
vertically at an upper position so as to face vertically toward a
front end of the movable element 22. When the engine valve is to be
opened, a power supply from a controller 11 to an upper valve
closing magnet coil portion 26 is turned off to de-energize it and,
thereafter, the power supply therefrom to a lower valve opening
electromagnet coil portion 25 is turned on to energize it and the
movable element 22 is magnetically attracted onto the lower valve
opening electromagnetic coil 25 so that valve body 20 is lifted in
a downward direction to open the valve. On the contrary, when the
valve is to be closed, the power supply to lower valve opening
electromagnetic coil portion 25 is turned off and, thereafter, the
power supply to upper valve closing electromagnetic coil portion 26
is turned on. Hence, movable element 22 can be attracted onto the
rear surface of upper valve closing electromagnet coil portion 26.
Then, valve body 20 is seated on a valve seat so that the intake
valve (exhaust valve) can be at the full closure portion. The valve
body 20 and the valve axle 21 shown in FIG. 2 correspond to the
intake valve 5 or the exhaust valve 6 shown in FIG. 1A. In
addition, the valve opening and closing electromagnetic coil
portions 25 and 26 are connected to controller 11 shown in FIG.
1A.
[0032] Referring back to FIG. 1A, an electronically controlled
throttle valve 9 (the throttle valve is driven by means of, e.g., a
DC motor) is disposed on a collecting portion of the intake air
passage 7 which is common to all cylinders. An electromagnetic type
fuel injection valve 10 is disposed on a part of intake port for
each cylinder.
[0033] It is noted that a blow-by gas ventilator ((i.e., a
crankcase) 50 and PCV (Positive Crankcase Ventilation) valve 51 are
interposed between a portion of the intake air passage 7 which is
located downstream to the throttle valve 9 and a portion of the
intake air passage 7 which is located upstream to the throttle
valve 9 as a crankcase ventilation system, a master vac.(also
called, a brake booster in a master cylinder) of a vehicular brake
system with a check valve 53 is linked to the portion of the intake
air passage 7 which is located at the downstream side to the
throttle valve 9, and a vaporized fuel purge system having a purge
control valve 54 connected to controller 11, a flow passage
pressure detector 55, a second passage 56, a canister 59, a first
passage 57, a fuel tank 58, and a drain cutting valve 61 is linked
to the same upstream portion of intake air passage 7 to the
throttle valve 9.
[0034] It is noted that the vaporized fuel purge system is also
exemplified by a U.S. Pat. No. 6,079,397 issued on Jun. 27, 2000
(disclosure of which is herein incorporated by reference).
[0035] Controller 11 controls operations of intake valve 5, exhaust
valve 6, electronically controlled throttle valve 9, fuel injection
valve 10, spark plug 4, purge control valve 54, and drain cutting
valve 61.
[0036] Controller 11 receives output signals from a crank angle
sensor 12, an accelerator pedal depression sensor 13, an airflow
meter 14, and a coolant temperature sensor 15.
[0037] The crank angle sensor 12 outputs a crank angular signal in
synchronization with an engine revolution so that controller 11 can
detect a crank angular position and an engine revolution number per
time in rpm (engine speed Ne). The accelerator pedal depression
sensor 13 detects an accelerator depression angle APO (or
accelerator pedal depression depth) and includes an idle switch
which is turned on when the accelerator pedal is fully closed. The
airflow meter 14 measures an intake air quantity Qa at a position
of intake air passage 7 upstream to the throttle valve 9. The
coolant temperature sensor 15 detects an engine coolant temperature
Tw.
[0038] Referring to FIG. 1B, controller 11 includes a microcomputer
basically having a CPU (Central Processing Unit) 11a, a ROM (Read
Only Memory) 11b, RAM (Random Access Memory) 11c, an Input Port
11d, an Output Port 11f, and a common bus and a peripheral
circuitry such as drive circuitry 11f.
[0039] In this engine 1, the open-and-closure operations of the
electromagnetically operated intake and exhaust valves 5 and 6 in
the electromagnetically driven type are controlled at a normal
driving state in order to improve the fuel consumption due to the
reduction in pumping loss. Especially, a valve opening timing of
the intake valve 5 (called, IVO) is set at a proximity to an upper
top dead center (TDC) and a valve closure timing of the intake
valve 5 (called, IVC) is variably controlled so that the air
quantity to be sucked into the cylinder 3 is controlled for the
sucked air quantity to reach to a target air quantity.
Consequently, a substantial non-throttling drive is enabled to be
carried out.
[0040] It is desired that the electronically controlled throttle
valve 9 is positioned in a full open state in order to give the
engine in the non-throttling drive. However, an opening angle of
throttle valve 9 is controlled by controller 11 in order to obtain
a required vacuum pressure within the intake air passage 7.
[0041] Fuel injection (start) timing and fuel injection quantity
through the fuel injection valve 10 are controlled by controller 11
on the basis of an engine driving condition. Basically, however,
the fuel injection quantity is controlled on the basis of the
intake air quantity Qa measured by means of the airflow meter 14 to
provide a desired air-fuel ratio.
[0042] An ignition timing through an ignition plug 4 is controlled
by controller 11 on the basis of the engine driving condition so as
to vary the ignition timing at an MBT (Minimum angle for Best
Torque) point or knocking limit point.
[0043] Next, controls for the valve closure timing of the intake
valve 5 (IVC) and the valve open timing (IVO) thereof 5 and the
electromagnetically controlled throttle valve 9 will be described
in more details with reference to flowcharts shown in FIGS. 3
through 5.
[0044] FIG. 3 shows the flowchart representing a calculation of a
target air quantity (viz., a target volumetric (volume) flow rate)
to be sucked into a corresponding engine cylinder.
[0045] At a step S1, controller 11 searches a target air quantity
corresponding to a driver's demanding torque as a target volumetric
flow rate (TQHO) by searching it from a map shown in FIG. 3 on the
basis of accelerator depression angle APO and engine speed Ne.
[0046] It is noted that, during an engine idle state (idle switch
ON), target volumetric flow rate TQHO is corrected in accordance
with a deviation ANe between engine speed Ne and a target engine
idling speed Nidle (.DELTA.Ne=Ne-Nidle). If this deviation
.DELTA.Ne is minus, TQHO is corrected in an increment direction. If
.DELTA.Ne>0, TQHO is corrected in a decrement direction. This
step S1 corresponds to a target air quantity calculating
section.
[0047] Suppose that volumetric flow rate QHO (target volumetric
flow rate TQHO) is deemed to be equivalent to .eta.v (a volumetric
efficiency).
[0048] A value of 1 of QHO means in a static sense of term that the
valve closure timing IVC of intake valve 5 is at a time point when
piston 2 has reached to a bottom dead center (BDC), viz., at a time
point of a maximum cylinder intake stroke volume.
[0049] In addition, QHO=0.7 represents that the cylinder intake
stroke volume indicates 70% with respect to a maximum stroke
volume.
[0050] FIG. 4 shows the flowchart representing a position control
for electronically controlled throttle valve 9.
[0051] At a step S11, controller 11 determines whether a vacuum
pressure request flag (NPRF) is set to "1" or reset to "0" to
determine whether there is a request to develop a vacuum pressure
in the portion of the intake air passage downstream to the throttle
valve 9.
[0052] If NPRF="0" (at a normal driving), the routine goes to a
step S12.
[0053] At the step S12, controller 11 refers to a normal drive
table to calculate a target vacuum pressure TBOOST from engine
coolant temperature Tw.
[0054] If NPRF flag="1", controller 11 determines that there is the
request to generate the vacuum pressure and the routine goes to a
step S13.
[0055] This vacuum pressure request flag NPRF is set to "1" when
the vacuum pressure request occurs from the blow-by gas ventilation
system, vaporized fuel purge system, and/or the brake master vac.
of the vehicular brake system.
[0056] Both tables during the normal driving and during the vacuum
pressure request indicate that as the coolant temperature Tw
becomes lower, the target vacuum pressure TBOOST is set to be
higher.
[0057] In addition, the target vacuum pressure TBOOST in the case
of the active vacuum pressure request table shown at the step S13
is usually higher than that in the case of the normal engine drive
state table shown at step S12.
[0058] At the next step S14, controller 11 converts target vacuum
pressure TBOOST calculated at step S12 or S13 into a target vacuum
pressure correction coefficient CBOOST(%) corresponding to
volumetric flow rate QHO by referring to a table shown at step
S14.
[0059] At the next step S15, controller 11 calculates an A/NV value
(A/NV value during the development of the target vacuum pressure)
viz., ASLBST when QHO=CBOOST from a QHO versus A/NV characteristic
curve shown in FIG. 9.
[0060] It is noted that A/NV value represents an opening area A of
throttle valve 9 divided by a product between engine speed Ne and
engine displacement V. The QHO versus A/NV characteristic curve
shown in FIG. 9 is a characteristic when no change occurs in the
valve closure timing IVC of intake valve 5 and the air quantity
(QHO) is controlled only through the opening area of the throttle
valve 9 (cylinder volume Vcyl=100%). It is noted that QHO=1
represents that the cylinder is in the atmospheric pressure state
and QHO=0 represents that the cylinder is in a vacuum state and the
table shown at step S15 corresponds to the characteristic curve
shown in FIG. 9.
[0061] At the next step S16, controller 11 calculates a throttle
valve opening angle calculation coefficient RKOTEN from target
vacuum pressure correction coefficient CBOOST calculated at step
S14 and ASLBST of the A/NV value during the occurrence of the
target vacuum pressure as follows:
RKOTEN=ASLBST/CBOOST (1).
[0062] The throttle valve opening angle correction coefficient
RKOTEN corresponds to a gradient of a straight line passing through
a point giving the target vacuum pressure on the QHO versus A/NV
characteristic curve, shown in FIG. 9, viz., corresponds to A/NV
value on the straight line when the volumetric flow rate of
QHO=1.
[0063] When the vacuum pressure is controlled to be constant
(fixed), the QHO versus A/NV characteristic indicates a straight
line and a gradient of this line causes the line to pass through
the point at which the desired vacuum pressure (CBOOST) on the QHO
versus A/NV characteristic curve is derived, during the cylinder
volume of 100%, as shown in FIG. 9.
[0064] In order to vary the target vacuum pressure during the
vacuum pressure constant control, the gradient (RKOTEN) is varied
so that an arbitrary vacuum pressure control becomes possible.
[0065] Referring back to a step S17 shown in FIG. 4, controller 11
provides a suitable delay processing for the target volumetric flow
rate TQHO calculated in the target air quantity calculating flow
shown in FIG. 3 and reads it.
[0066] At a step S18, controller 11 calculates a vacuum pressure
controlling A/NV value, i.e., TANV from the target volumetric flow
rate TQHO read at step S17 and the throttle opening angle
calculation correction coefficient (gradient) RKOTEN calculated at
step S16 as follows:
TANV=TQHO.times.RKOTEN (2).
[0067] Since the vacuum pressure controlling A/NV value TANV has
been calculated, a vacuum pressure controlling throttle valve
opening area A can be calculated from engine speed Ne and the
engine displacement V. Hence, at the step S19, this value TANV is
converted into a target opening angle TVO of the electronically
controlled throttle valve 9. Consequently, the opening angle of the
electronically controlled throttle valve 9 is controlled. Steps S11
through S13 shown in FIG. 4 correspond to target vacuum pressure
calculating section. Steps S14 through S19 correspond to throttle
valve opening angle controlling section.
[0068] FIG. 5 shows the flowchart representing a valve timing
control procedure executed in the first embodiment of the control
apparatus shown in FIG. 1A.
[0069] At a step S21, controller 11 reads target volumetric flow
rate TQHO as target air quantity calculating flow shown in FIG.
3.
[0070] At a step S22, controller 11 reads target vacuum pressure
correction coefficient CBOOST calculated in the throttle valve
control flowchart shown in FIG. 4.
[0071] At a step S23, controller 11 calculates a post-correction
target volumetric flow rate TQHO' as a post-correction target air
quantity from target volumetric flow rate TQHO and target vacuum
pressure correction coefficient CBOOST as follows:
TQHO'=TQHO/CBOOST (3).
[0072] At a step S24, controller 11 calculates a valve timing to
obtain the post-correction target air quantity.
[0073] That is to say, while the intake valve open timing TVO is
fixed at a proximity to the upper top dead center (TDC), controller
11 refers to the table shown at step S24 of FIG. 5 to calculate the
closure timing IVC of intake valve 5 from the post-correction
(namely, corrected) target volumetric flow rate TQHO' derived in
the equation (3). Specifically, as the post-correction target
volumetric flow rate TQHO' becomes smaller, the closure timing IVC
of the intake valve 5 is set toward the upper top dead center (TDC)
direction. As the post-correction target volumetric flow rate TQHO'
becomes larger, the closure timing IVC of intake valve 5 is set
toward bottom dead center (BDC) direction.
[0074] The flowchart shown in FIG. 5 corresponds to intake valve
open-and-closure timing controlling section.
[0075] Especially, steps S22 and S23 correspond to vacuum pressure
dependent correcting section for correcting the target air quantity
(target volumetric flow rate TQHO) to calculate the valve closure
timing (IVC) of the intake valve in accordance with the target
vacuum pressure (target vacuum pressure correction coefficient
CBOOST).
[0076] FIG. 10 shows a characteristic graph representing the QHO
versus A/NV characteristic when the valve closure timing IVC of
intake valve 5 (namely, cylinder volume Vcyl is varied) is
varied.
[0077] This characteristic graph of FIG. 10 represents an analogous
constriction form of QHO versus A/NV characteristic shown in FIG. 9
as a base (Vcyl: 100%).
[0078] For example, suppose that when the valve closure timing IVC
of intake valve 5 is at a maximum (Vcyl: 100%), target volumetric
flow rate TQHO is 1.
[0079] Since, at this time, QHO is varied at a rate of Vcyl target
volumetric flow rate TQHO indicates 0.6 when Vcyl=60%.
[0080] For example, QHO which provides a certain target vacuum
pressure when Vcyl=60% is 0.92 and 0.6.times.0.92=0.55 when QHO
which provides QHO when Vcyl: 100% (this value corresponds to
TQHO).
[0081] This means that to obtain a certain target vacuum pressure
when TQHO=0.55, it is necessary to provide the valve closure timing
IVC of intake valve 5 which gives a maximum air quantity at a time
point of 0.6=0.55/0.92 of the characteristic line passing through
QHO=0.55.
[0082] Hence, the vacuum pressure dependent correction for the
valve closure timing IVC of intake valve 5 is carried out.
[0083] Next, a second preferred embodiment of the control apparatus
for the internal combustion engine will be described below.
[0084] FIG. 6 shows a rough system configuration of the internal
combustion engine to which the control apparatus for the internal
combustion engine in the second preferred embodiment according to
the present invention is applicable.
[0085] In the second embodiment, a vacuum pressure sensor 16 is
disposed to detect an actual vacuum pressure BOOST on the portion
of the intake air passage 7 downstream to the throttle valve 9 and
an output signal of the vacuum pressure sensor 16 is supplied to
controller 11.
[0086] FIG. 7 shows the flowchart on the valve timing control, the
flowchart being executed in place of FIG. 5 described in the first
embodiment.
[0087] At a step S31, controller 11 reads the target volumetric
flow rate TQHO calculated in the target air quantity calculation
flow shown in FIG. 3.
[0088] At a step S32, controller 11 reads an actual vacuum pressure
BOOST detected by means of vacuum pressure sensor 16.
[0089] At a step S33, controller 11 converts actual vacuum pressure
BOOST detected at step S32 into actual vacuum pressure correction
coefficient CBOOST (%) corresponding to volumetric flow rate QHO by
referring to a table map shown at step S23.
[0090] At the next step S34, controller 11 calculates the
post-correction target volumetric flow rate TQHO' as the
post-correction target air quantity from target volumetric flow
rate TQHO and actual vacuum pressure correction coefficient CBOOST
as follows:
TQHO'=TQHO/CBOOST (4).
[0091] At the next step S35, controller 11 calculates a valve
open-and-closure timing to obtain post-correction target air
quantity TQHO. That is to say, while the valve open timing IVO of
intake valve 5 is fixed at the proximity to upper top dead center
(TDC), controller 11 calculates the closure timing IVC of intake
valve 5 by referring to a table as shown at step S35 of FIG. 7 with
respect to the post-correction target volumetric flow rate TQHO'
and variably controls the closure timing of intake valve 5.
Specifically, as the post-correction target volumetric flow rate
TQHO' becomes smaller, the closure timing IVC of intake valve 5 is
set toward the upper top dead center direction and the closure
timing IVC of intake valve is set toward the bottom dead center
(BDC) direction as the post-correction target volumetric flow rate
TQHO' becomes larger.
[0092] This flow of FIG. 7 corresponds to the intake valve
open-and-closure timing controlling section and steps S32 through
S34 correspond to vacuum pressure dependent correcting section for
correcting the target air quantity (target volumetric flow rate
TQHO) in accordance with actual boost correction coefficient CBOOST
to calculate intake valve closure timing IVC.
[0093] A third preferred embodiment of the control apparatus for an
internal combustion engine will be described below.
[0094] FIG. 8 shows the flowchart representing the valve timing
control executed in the third preferred embodiment of the control
apparatus. The other structure of the control apparatus in the
third embodiment is the same as shown in FIG. 1A or FIG. 6.
[0095] The program based on the flowchart of FIG. 8 is executed in
place of FIG. 5 or FIG. 7 described in the first or second
embodiment.
[0096] At a step S41, controller 11 reads the target volumetric
flow quantity TQHO as target air quantity calculated in the target
air quantity calculation flow shown in FIG. 3.
[0097] At a step S42, controller 11 calculates the valve
open-and-closure timing to obtain the target air quantity.
[0098] That is to say, while the valve open timing IVO of intake
valve open timing IVO of intake valve 5 is fixed at the proximity
to the upper top dead center (TDC), controller 11 calculates valve
closure timing IVC of intake valve 5 by referring to a table shown
in FIG. 8 with respect to the target volumetric flow rate TQHO. As
the target volumetric flow rate TQHO becomes smaller, the valve
closure timing IVC of intake valve 5 is set toward the upper top
dead center direction. As TQHO becomes larger, the valve closure
timing IVC of intake valve 5 is set toward bottom dead center (BDC)
direction.
[0099] At the next step S43, controller 11 reads either target
vacuum pressure (TBOOST) calculated in the flow shown in FIG. 4 or
actual vacuum pressure BOOST detected by means of vacuum pressure
sensor 16.
[0100] At the next step S44, controller 11 refers to a table shown
at step S44 in FIG. 8 according to the target vacuum pressure
TBOOST or actual vacuum pressure BOOST to calculate a correction
value .DELTA.IVC for the valve closure timing IVC of intake valve
5.
[0101] It is noted that as target vacuum pressure TBOOST or actual
vacuum pressure BOOST becomes higher, the correction value
.DELTA.IVC is set to be larger.
[0102] At a step S45, controller 11 corrects the valve closure
timing IVC of intake valve 5 on the basis of the correction value
.DELTA.IVC. That is to say, controller 11 adds the correction value
.DELTA.IVC calculated at step S44 to the closure timing IVC of
intake valve 5 calculated at step S42 to determine a
post-correction intake valve closure timing IVC' as described in
the following equation.
IVC'=IVC+.DELTA.IVC (5).
[0103] As described above, as target vacuum pressure TBOOST (or
actual vacuum pressure BOOST) becomes higher, air density becomes
reduced. Hence, to compensate for the reduction in air density, the
closure timing IVC of intake valve 5 is corrected toward a
retardation direction (namely, the intake stroke bottom dead center
(BTC) direction).
[0104] The flow shown in FIG. 8 corresponds to the intake valve
open-and-closure timing controlling section. Especially, the steps
S43 through S45 correspond to vacuum pressure dependent correcting
section for correcting the valve closure timing IVC of intake valve
5 calculated on the basis of the target air quantity. In each of
the first through third embodiments, the electromagnetic operation
type variable valve drive unit has been used for each of the engine
valves. However, the present invention is applicable to hydraulic
operation type variably operated engine valves.
[0105] The entire contents of Japanese Patent Application No.
11-356401 filed in Japan on Dec. 15, 1999 are herein incorporated
by reference. Although the invention has been described above by
reference to certain embodiment of the invention, the invention is
not limited to the embodiments described above. Modifications and
variations of the embodiments described above will occur to those
skilled in the art in the light of the above teachings. The scope
of the invention is defined with reference to the following
claims.
* * * * *