U.S. patent application number 09/842192 was filed with the patent office on 2001-08-16 for engine control apparatus.
This patent application is currently assigned to Hitachi, Ltd.. Invention is credited to Asano, Seiji, Hosokawa, Kouji, Shimada, Kousaku.
Application Number | 20010013335 09/842192 |
Document ID | / |
Family ID | 18226103 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010013335 |
Kind Code |
A1 |
Hosokawa, Kouji ; et
al. |
August 16, 2001 |
Engine control apparatus
Abstract
The variation of the A/F ratio and the deterioration of driving
feeling or exhaust owing to the response delay of air intake
against the fuel injection is suppressed, in an engine control
apparatus for controlling an intake air flow based on the torque or
the fuel injection amount. The apparatus causes the phase of fuel
injection to fit to that of air intake. In order to fit the phase
of fuel injection to that of air intake, an apparatus for delaying
the fuel injection or an apparatus for speeding up the air intake
is used.
Inventors: |
Hosokawa, Kouji; (Tokyo,
JP) ; Shimada, Kousaku; (Hitachinaka-shi, JP)
; Asano, Seiji; (Hitachinaka-shi, JP) |
Correspondence
Address: |
EVENSON, McKEOWN, EDWARDS
& LENAHAN, P.L.L.C.
Suite 700
1200 G Street, N.W.
Washington
DC
20005
US
|
Assignee: |
Hitachi, Ltd.
|
Family ID: |
18226103 |
Appl. No.: |
09/842192 |
Filed: |
April 26, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09842192 |
Apr 26, 2001 |
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09201830 |
Dec 1, 1998 |
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6223728 |
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Current U.S.
Class: |
123/478 ;
123/350; 123/399 |
Current CPC
Class: |
F02D 41/18 20130101;
F02D 2041/1433 20130101; F02D 2200/0406 20130101; F02D 2200/0414
20130101; F02D 41/1401 20130101; F02D 2041/389 20130101; Y02T 10/40
20130101; F02D 43/00 20130101; F02D 2200/0408 20130101; F02D
41/0002 20130101; F02D 2200/503 20130101 |
Class at
Publication: |
123/478 ;
123/350; 123/399 |
International
Class: |
F02D 041/14; F02D
041/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 1, 1997 |
JP |
9-329864 |
Claims
What is claimed is:
1. An engine control apparatus comprises; a reference pulse width
calculating means for calculating the width of a reference pulse
used as the reference when a fuel injection pulse width is
calculated based on operating conditions, a target A/F ratio
calculating means for calculating the target A/F ratio based on the
operating conditions, a target throttle opening calculating means
for calculating the target throttle opening based on the operating
condition including the target A/F ratio, a fuel injection phase
correcting means for calculating the width of a filtering reference
pulse by time-filtering the reference pulse width, whereby the fuel
injection amount is calculated based on the filtering reference
pulse width and the fuel injection control is performed.
2. The engine control apparatus according to claim 1, further
comprising an intake air flow calculating means for calculating air
flow aspirated into an engine cylinder and obtaining actual air
flow aspirated into the cylinder.
3. The engine control apparatus according to claim 2, wherein said
intake air flow calculating means for calculating or detecting
throttle-passed air flow, and calculating the air flow aspirated
into the cylinder.
4. The engine control apparatus according to claim 2, wherein said
intake air flow calculating means comprises; a throttle-passed air
flow calculating means for calculating or detecting the
throttle-passed air flow, an intake pipe inner pressure estimating
means for estimating the inner pressure of the intake pipe based on
the throttle-passed air flow and the cylinder intake air flow, and
a cylinder intake air flow calculating means for calculating the
cylinder intake air flow based on engine speed and the inner
pressure of the intake pipe.
5. The engine control apparatus according to claim 2, wherein said
intake air flow calculating means comprises; an intake pipe inner
pressure detecting means for detecting the inner pressure of the
intake pipe, and a cylinder intake air flow calculating means for
calculating the air flow aspirated into the cylinder based on
engine speed and the inner pressure of the intake pipe.
6. The engine control apparatus according to any one of claims 1 to
5, further comprising a target air flow calculating means for
calculating the target air flow to be aspirated into the engine
cylinder.
7. The engine control apparatus according to claim 6, wherein said
target air flow calculating means calculates the target air flow
based on the width of the reference pulse, the target A/F ratio and
the engine speed.
8. The engine control apparatus according to any one of claims 1 to
7, wherein the reference pulse width calculating means obtains the
width of the reference pulse by referring to a map with axes of an
engine speed and an accelerator opening.
9. The engine control apparatus according to any one of claims 1 to
8, wherein the target A/F ratio calculating means obtains the
target A/F ratio by referring to a map with axes of an engine speed
and the reference pulse width.
10. The engine control apparatus according to any one of claims 1
to 9, wherein the fuel injection phase correcting means calculates
air-response time constant of a cylinder intake air flow based on
the target air flow calculated by the target air flow calculating
means, the cylinder intake air flow calculated or detected the
intake air flow calculating means and the cylinder intake air flow
previously calculated or detected, and obtains the filtering
reference pulse width by using the air-response time constant as a
time-filter.
11. The engine control apparatus according to any one of claims 1
to 9, wherein said fuel injection phase correcting means comprises;
an actual reference pulse width calculating means for calculating
the width of the actual reference pulse per one cylinder by
dividing the cylinder intake air flow by the engine speed and
multiplying the quotient by a coefficient that can obtains the
stoichiometric A/F ratio (=14.7), and a target throttle opening
calculating means for obtaining the width of the target reference
pulse by multiplying the reference pulse width by the target A/F
ratio and dividing the product by the stoichiometric A/F ratio
(=14.7), wherein a response time constant of the actual reference
pulse width is calculated based on the actual reference pulse
width, the previously calculated actual reference pulse width and
the target reference pulse width, and the filtering reference pulse
width is obtained by using the response time constant as the
time-filter.
12. The engine control apparatus according to any one of claims 1
to 9, wherein the fuel injection phase correcting means obtains the
filtering reference pulse width by multiplying the reference pulse
width by the ratio of the cylinder intake air flow and the target
air flow.
13. The engine control apparatus according to claim 12, wherein if
it is within a predetermined delay time from the switching of the
target A/F ratio and if the ratio of the cylinder intake air flow
and the target air flow is within a range defined by a certain
threshold value, the reference pulse width itself is used as the
filtering reference pulse width.
14. The engine control apparatus according to any one of claims 1
to 9, wherein the fuel injection phase correcting means obtains
filtering reference pulse width by delaying the reference pulse
width by the delay time.
15. The engine control apparatus according to any one of claims 1
to 9, wherein the fuel injection phase correcting means obtains the
filtering reference pulse width from the reference pulse width
based on a time constant of first-order lag.
16. The engine control apparatus according to either claims 14 or
15, wherein each of the delay time and the time constant of
first-order lag is switched to either of two setting values, in
accordance with either an idle state or an off-idle state, an
accelerator opening, actual opening of the throttle, and the
cylinder intake air flow.
17. The engine control apparatus according to either claims 14 or
15, wherein each of the delay time and the time constant of
first-order lag are obtained by referring to a table with an axis
of a gear position, an engine speed, actual opening of the
throttle, or a cylinder intake air flow.
18. The engine control apparatus according to either claims 14 or
15, wherein the delay time and the time constant of first-order lag
are obtained by referring to a map with axes of an engine speed and
actual opening of the throttle, or a map with axes of an engine
speed and a cylinder intake air flow.
19. The engine control apparatus according to claim 15, wherein the
delay time is obtained by learning the time from the change in the
target throttle opening to the change in a cylinder intake air
flow.
20. The engine control apparatus according to claim 15, wherein the
constant time of first-order lag is obtained by learning the change
in a cylinder intake air flow when the target throttle opening is
changed.
21. The engine control apparatus according to either claims 19 or
20, wherein each of the delay time and the time constant of
first-order lag is obtained by learning as two setting values, in
accordance with either an idle state or an off-idle state, an
accelerator opening, actual opening of the throttle, and the
cylinder intake air flow.
22. The engine control apparatus according to either claims 19 or
20, wherein each of the delay time and the time constant of
first-order lag is obtained by learning as a reference value of a
table with an axis of a gear position, an engine speed, actual
opening of the throttle, or a cylinder intake air flow.
23. The engine control apparatus according to either claims 14 or
15, wherein each of the delay time and the time constant of
first-order lag is obtained by learning as a reference value of a
map with axes of an engine speed and actual opening of the
throttle, or a map with axes of an engine speed and a cylinder
intake air flow.
24. The engine control apparatus according to any one of claims 1
to 23, wherein said target filtering reference pulse width
comprises; a means for calculating the throttle opening
corresponding to engine speed feedback correction for allowing the
engine speed at idle to follow the target engine speed, a means for
calculating load-corresponding throttle opening based on the
correction to loads of an air conditioner, a power steering, an
electrical load (consumption current), an electrical radiator fan,
etc., and a means for calculating the throttle opening
corresponding to the accelerator opening, wherein the target
throttle opening is obtained based on the target A/F ratio and the
sum of the throttle opening corresponding to the feedback
correction of the engine speed, the throttle opening corresponding
to the loads and the throttle opening corresponding to the
accelerator.
25. The engine control apparatus according to any one of claims 1
to 23, wherein said target throttle opening calculating means
further comprises target air flow calculating means for calculating
the target air flow, and the target throttle opening is obtained by
converting the target air flow using the throttle opening.
26. The engine control apparatus according to any one of claims 1
to 23, wherein said target throttle opening calculating means
comprises; an intake air flow calculating means for calculating or
detecting a cylinder intake air flow, target air flow calculating
means for calculating the target air flow, and a target throttle
opening feedback calculating means for calculating the target
throttle opening by using the feedback control in which the
cylinder intake air flow is allowed to follow the target air
flow.
27. The engine control apparatus according to any one of claims 1
to 23, wherein said target throttle opening calculating means
comprises; an intake air flow calculating means for calculating or
detecting a cylinder intake air flow, an actual reference pulse
width calculating means for calculating the width of the actual
reference pulse per one cylinder by dividing the cylinder intake
air flow by the engine speed and multiplying the quotient by a
coefficient that can obtains the stoichiometric A/F ratio (=14.7),
and a target throttle opening calculating means for obtaining the
width of the target reference pulse by multiplying the reference
pulse width by the target A/F ratio and dividing the product by the
stoichiometric A/F ratio (=14.7), a target throttle opening
feedback calculating means for calculating the target throttle
opening by using the feedback control in which the actual reference
pulse width is allowed to follow the target reference pulse
width.
28. The engine control apparatus according to either claims 26 or
27, further comprising a means for setting the feedback constant of
the target throttle opening feedback calculating means in
accordance with the operating condition.
29. The engine control apparatus according to claim 28, wherein
said feedback constant setting means switches the feedback constant
to either of two setting values, in accordance with either an idle
state or an off-idle state, an accelerator opening, actual opening
of the throttle, and the cylinder intake air flow.
30. The engine control apparatus according to claim 28, wherein
said feedback constant setting means obtains the feedback constant
by referring to a table with an axis of a gear position, an engine
speed, actual opening of the throttle, or a cylinder intake air
flow.
31. The engine control apparatus according to claim 28, wherein
said feedback constant setting means obtains the feedback constant
by referring to a map with axes of an engine speed and actual
opening of the throttle, or a map with axes of an engine speed and
a cylinder intake air flow.
32. The engine control apparatus according to any one of claims 1
to 32, wherein an actuator for providing the target throttle
opening calculated by said target throttle opening calculating
means is an electronically controlled throttle.
33. The engine control apparatus according to any one of claims 1
to 32, wherein an object to be controlled is a lean-burn
engine.
34. The engine control apparatus according to any one of claims 1
to 32, wherein an object to be controlled is an in-cylinder
injection engine.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an engine control apparatus
for controlling an intake air flow based on torque or a fuel
injection amount, particularly to an engine control apparatus which
can obtain suitable air/fuel ratio in any operating conditions.
[0002] The typical engine control apparatus is disclosed, for
example, in Japanese Patent Application Laid-Open No.7-301139
(1995).
[0003] In the prior art, the fuel injection is performed after at
least two parameters is selected among the timing of the fuel
injection, the ratio of air to fuel (A/F ratio), the timing of
ignition and the air flow, based on the target torque calculated
according to the operating condition, and thereby controlling the
engine so as to improve the fuel consumption and the feeling of
run.
[0004] However, the above prior art does not disclose the timing of
the fuel injection and air intake. Therefore, in particular, there
is a fear that the variation of the A/F ratio and the deterioration
of driving feeling or exhaust occurs, owing to the response delay
of air intake against the fuel injection in the transient state of
the intake air flow control performed based on the torque or the
fuel injection amount.
SUMMARY OF THE INVENTION
[0005] An object of the present invention is to suppress the
variation of the A/F ratio and the deterioration of driving feeling
or exhaust owing to the response delay of air intake against the
fuel injection, in an engine control apparatus for controlling an
intake air flow based on the torque or the fuel injection
amount.
[0006] The above object is attained by fitting the phase of fuel
injection to that of air intake. In order to fit the phase of fuel
injection to that of air intake, the present invention adopts a
method of delaying the fuel injection or a method of speeding up
the air intake.
[0007] In the former method, time-filtering for the fuel injection
amount is performed.
[0008] Concretely, an engine control apparatus according to an
embodiment of the present invention has a means for calculating the
width of a reference pulse used as the reference when a fuel
injection pulse width is calculated based on operating conditions,
a means for calculating the target A/F ratio based on the operating
conditions, a means for calculating the target throttle opening
based on the operating condition including the target A/F ratio,
and a fuel injection phase correcting means for calculating the
width of a filtering reference pulse by time-filtering the
reference pulse width.
[0009] The fuel injection amount is calculated based on the
filtering reference pulse width and the fuel injection control is
performed.
[0010] In the latter method, an electronically controlled throttle
is used to control the intake air flow. Further, the feedback
constant is controlled when feedback-controlling the opening of the
electronically controlled throttle.
[0011] Concretely, an engine control apparatus according to another
embodiment of the present invention has a means for calculating the
width of a reference pulse used as the reference when a fuel
injection pulse width is calculated based on operating conditions,
a means for calculating the target A/F ratio based on the operating
conditions, a means for calculating the target throttle opening
based on the operating condition including the target A/F ratio.
Further, the target throttle opening calculating means includes a
means for calculating or detecting a cylinder intake air flow, a
means for calculating the target air flow, a means for
feedback-calculating the target throttle opening by using the
feedback control in which the cylinder intake air flow is allowed
to follow the target air flow, and a means for setting the feedback
constant of the target throttle opening feedback calculating means
in accordance with the operating condition.
[0012] While the variation of the fuel injection amount is
reflected instantaneously on the fuel injection apparatus in the
transient state of the engine control apparatus which controls the
intake air flow based on the torque or the fuel injection amount,
the variation of the cylinder intake air flow is behind the
variation of the fuel injection amount owing to the time lag
required to pass through the intake pipe or the time lag necessary
for the variation of the inner pressure of the intake pipe.
[0013] With regard to the above problem, in the case that the
time-filtering is applied to the fuel injection amount, or the
electronically controlled throttle is used for the control of the
intake air flow and further the opening of the electronically
controlled throttle is feedback-controlled, it becomes possible to
fit the phases of the fuel injection and the air intake to each
other, and thus suppress the variation of the A/F ratio and the
deterioration of the drive feeling or exhaust.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a control block diagram according to an embodiment
of the present invention.
[0015] FIG. 2 is a schematic diagram of an in-cylinder injection
engine system to which the present invention is applied.
[0016] FIG. 3 is a schematic diagram of a control unit to which the
present invention is applied
[0017] FIG. 4 is a control block diagram of the present
invention.
[0018] FIG. 5 is a control block diagram of the intake air flow
calculating means.
[0019] FIG. 6 is a flow chart of the intake air flow calculating
means shown in FIG. 5.
[0020] FIG. 7 is a model diagram of an intake pipe.
[0021] FIG. 8 is a control block diagram of the target throttle
opening calculating means.
[0022] FIG. 9 is a flow chart of the target throttle opening
calculating means shown in FIG. 8.
[0023] FIG. 10 is a control block diagram of the fuel injection
phase correcting means.
[0024] FIG. 11 is a flow chart of the fuel injection phase
correcting means shown in FIG. 10.
[0025] FIG. 12 is an illustration showing a method of calculating
the time constant of air response.
[0026] FIG. 13 is an illustration of effects of the fuel injection
phase correcting means shown in FIG. 1.
[0027] FIG. 14 is a control block diagram of the throttle-passed
air flow calculating means.
[0028] FIG. 15 is a control block diagram of the intake pipe inner
pressure estimating means.
[0029] FIG. 16 is a control block diagram of the cylinder intake
air flow calculating means.
[0030] FIG. 17 is a control block diagram of the target air flow
amount calculating means.
[0031] FIG. 18 is a control block diagram of the target throttle
opening calculating means.
[0032] FIG. 19 is a control block diagram of the target throttle
opening calculating means.
[0033] FIG. 20 is a flow chart of the target shown in FIG. 19.
[0034] FIG. 21 is a control block diagram of the target throttle
opening calculating means.
[0035] FIG. 22 is a flow chart of the target throttle opening
calculating means shown in FIG. 21.
[0036] FIG. 23 is a control block diagram of the fuel injection
phase correcting means.
[0037] FIG. 24 is a flow chart of the fuel injection phase
correcting means shown in FIG. 22.
[0038] FIG. 25 is a control block diagram of the fuel injection
phase correcting means.
[0039] FIG. 26 is an illustration of effects of the fuel injection
phase correcting means shown in FIG. 25.
[0040] FIG. 27 is an illustration of effects of a means for setting
the feedback constant of the target throttle opening.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0041] Embodiments of the present invention will be explained in
detail hereinafter with reference to the drawings.
[0042] Now, FIG. 2 is a schematic diagram of an in-cylinder
injection engine system to which the present invention is applied.
In FIG. 2, the air aspirated into an engine passes from an inlet
portion 202a of an air cleaner 202 to a collector 206 via an intake
air temperature sensor 225, an air flow sensor 203 and a throttle
body housing a throttle valve 205 for controlling the intake air
flow. An intake pipe pressure sensor 224 is provided on the side of
a cylinder. The intake air is distributed into the intake pipes
each connected to each of the cylinders of an engine 207, and
introduced to the inside of the cylinders.
[0043] While, fuel such as gasoline is pumped up from a fuel tank
214, a primary pressure is applied by a fuel pump 210 and a
secondary pressure by a fuel pump 211. The pressurized fuel is
supplied to a fuel system having an injector 209. The
primarily-pressurized fuel is adjusted to become a constant
pressure (ex. 3 kg/cm.sup.2) by a fuel-pressure regulator 212, and
the higher secondarily-pressurized fuel is also adjusted to become
a constant pressure (ex. 50 kg/cm.sup.2). Then, the pressurized
fuel is injected into the cylinder from the injector 209 provided
in each cylinder. The injected fuel is ignited by an ignition plug
208 receiving an high voltage ignition signal supplied from an
ignition coil 222.
[0044] A control unit 215 inputs a signal indicative of the
temperature of the intake air from the intake air temperature
sensor 225, a signal indicative of the intake air flow from the air
flow sensor 203, and a signal indicative of the inner pressure of
the intake pipe from the intake pipe pressure sensor 224. The
throttle body has a throttle sensor 204 for detecting the opening
of the throttle valve 205a. An output of the throttle sensor 204 is
also input to the control unit 215.
[0045] Further, reference numeral 216 designates a crank shaft
mounted on an axis of a cam shaft, for outputting an angle signal
POS for the detection of a rotation signal (indicative of engine
speed) and a reference angle signal REF indicative of the
rotational position of the crank shaft. These signals are also
input to the control unit 215.
[0046] Reference numeral 218 designates an A/F sensor provided
before a catalyst 220 in an exhaust pipe 219. An output signal of
the A/F sensor is also input to the control unit 215. Further, a
fuel pressure sensor 223 is provided inside of the secondarily
pressurized piping. An output signal of the fuel pressure sensor is
also input to the control unit 215.
[0047] As shown in FIG. 3, a major part of the control unit 215
comprises an MPU 301, a ROM 302, a RAM 303 and an I/O LSI 304
including an A/D converter. The control unit 215 inputs signals
from various sensors for detecting the operating conditions of the
engine, carries out the predetermined arithmetic processing, and
supplies the predetermined control signals to the injector 209 and
the ignition coil 222. As described above, the controls of the
amount of fuel supply and the ignition timing are performed.
[0048] FIG. 4 is a control block diagram showing the fuel injection
control and the air intake control performed in the control unit
215 of the in-cylinder injection engine as described above. While
the configuration of FIG. 4 comprises a reference pulse width
calculating means 401, a target A/F ratio calculating means 402, an
intake air flow calculating means 403, a target air flow amount
calculating means 404, a target throttle opening calculating means
405 and a fuel injection phase correcting means 406, it may
eliminate either or both of the intake air flow calculating means
403 and the target air flow amount calculating means 404 from the
above configuration.
[0049] The configuration of FIG. 1 is an example of an apparatus
having the whole components of FIG. 4. The configuration of FIG. 1
will be explained in detail hereinafter.
[0050] In the reference pulse width calculating means 101, the
reference pulse width KTP is obtained by referring a map based on
the accelerator opening Acc and the engine speed Ne. the reference
pulse width KTP is a reference value used when the width TI of fuel
injection pulse is calculated. The pulse width TI is calculated,
for example, by equation 1.
TI=KTP.times.COEF.times.GAMMA (1)
[0051] Where, COEF is a fuel correction coefficient of open loop
which acts according to the operation conditions such as a
transient state and an after-starting state, and GAMMA is a A/F
feedback coefficient.
[0052] In the target A/F ratio calculating means 102, the target
A/F ratio tAF is obtained by referring a map based on the engine
speed Ne and the reference pulse width KTP.
[0053] In the intake air flow calculating means 103, the cylinder
intake air flow rQa is calculated from the throttle-passed air flow
rQt which is an output of the air flow sensor. The details of the
control is shown in FIG. 5.
[0054] First, the output of the air flow sensor is converted into
the throttle-passed air flow rQt by using a voltage-mass flow
conversion table 501. Then, the inner pressure rPa of the intake
pipe is calculated from the convertethrottle-passed air flowd rQt,
the cylinder intake air flow rQa, and the previously calculated
value rPa[-dt] of the inner pressure of the intake pipe by an
intake inner pressure estimating means 502. The equation carried
out in the intake pipe inner pressure estimating means 502 is
obtained as follows.
[0055] The gradient of the inner pressure of the intake pipe is
proportional to the difference between the throttle-passed air flow
rQt and the cylinder intake air flow rQa. The equation (2)
represents the relationship mentioned above. A proportion
coefficient K1 is introduced from the state equation of ideal gas,
and is expressed as equation (3).
d(rPa)/dt=K1.times.(rQt-rQa) (2)
K1=R.times.Ta/M.times.V (3)
[0056] Where, R is a gas constant, Ta temperature of the intake
air, M average molecular weight of the air and V volume from the
throttle to the cylinder.
[0057] The following equation (4) is obtained by developing the
equation (2) for use of the digital processing. The inner pressure
rPa of the intake pipe is obtained by the equation (4).
rPa=rPa[-dt]+dt.times.K1.times.(rQt-rQa) (4)
[0058] The cylinder intake air flow rQa is calculated by the
cylinder intake air flow calculating means 503 based on the engine
speed Ne and the inner pressure rPa of the intake pipe calculated
by the intake pipe inner pressure estimating means 502. A map used
in the cylinder intake air flow calculating means 503 is set by the
following equation (5). The equation (5) is introduced from the
state equation of ideal gas.
[0059] rQa={rPa.times.(Ne/120).times.M.times.D/R.times.Ta}.eta.
(5)
[0060]
[0061] where, D is the displacement of an engine and .eta. is the
charging efficiency. FIG. 6 is a flow chart of the intake air flow
calculating means shown in FIG. 5.
[0062] Effects of the control of FIG. 5 will be explained. FIG. 7
shows an example of a model of the intake pipe. Particularly, in a
transient state, the throttle-passed air flow rQt does not match
the cylinder intake air flow rQa due to the volume of the intake
pipe. Concretely, the throttle-passed air flow rQt during the
acceleration increases more than the cylinder intake air flow rQa,
because extra air flow is required to fill up the intake pipe.
Further, the throttle-passed air flow rQt during the deceleration
decreases more than the cylinder intake air flow rQa, because a
part of the air flow filled in the intake pipe flows into the
cylinder.
[0063] While, it becomes possible to prevent the mismatching of the
throttle-passed air flow rQt and the cylinder intake air flow rQa
caused by the volume of the intake pipe by using the control of
FIG. 5, because the time-variation of the inner pressure rPa of the
intake pipe is modeled. As a result, it is possible to calculate
the cylinder intake air flow rQa with a high accuracy.
[0064] Next, in the target air flow amount calculating means 104,
the target air flow tQa is calculated by the equation (6) based on
the reference pulse width KTP calculated in the reference pulse
width calculating means 101, the target A/F ratio tAF calculated in
the target A/F ratio calculating means 102 and the engine speed
Ne.
tQa=(1/K2).times.KTP.times.(tAF/14.7).times.Ne (6)
K2=K3.times.f(FP) (7)
[0065] Where, K2 is obtained by equation (7). K3 is a conversion
coefficient used when the actual reference pulse rTP is obtained
from the cylinder intake air flow rQa and the engine speed Ne of
the equation (8) known in the control of the conventional intake
port injection (MPI). Further, FP is a fuel pressure, and K2
includes the correction of the fuel pressure according to
f(FP).
RTP=K3.times.(rQa/Ne) (8)
[0066] In the target throttle opening calculating means 105, the
target throttle opening tTH is feedback-controlled according to the
difference between the target air flow tQa calculated in the target
air flow amount calculating means 104 and the cylinder intake air
flow rQa calculated in the intake air flow calculating means 103.
Where, an actuator for controlling the target throttle opening tTH
is an electronically controlled throttle.
[0067] The configuration of the target throttle opening calculating
means 105 is shown in FIG. 8. First, the deviation eQa of the air
flow is obtained by subtracting the cylinder intake air flow rQa
from the target air flow tQa. The proportional component of the
feedback control is obtained by multiplying the deviation of the
air flow by a gain obtained by a block 801, the differential
component is obtained by multiplying the differential value of the
air flow deviation eQa obtained by a differential circuit 802 by a
differential gain in a block 803, and the integration component is
obtained by multiplying the integral value of the air flow
deviation eQa obtained by an integral circuit 804 by an integral
gain in a block 805. Finally, the target throttle opening rTH is
obtained by summing the proportional value, the differential value
and the integral value. FIG. 9 shows a flow chart used for the
calculation of the target throttle opening in FIG. 8
[0068] By performing the feedback control of the target throttle
opening rTH, the matching steps are extremely decreased, and it
becomes possible to fit correctly the cylinder intake air flow rQa
to the target air flow tQa. Further, because the time-variation of
the inner pressure is modeled and the mismatching of the
throttle-passed air flow rQt, and thus the cylinder intake air flow
rQa due to the volume of the intake pipe is compensated in this
example, it is possible to obtain more accurate cylinder intake air
flow rQa and thus improve the precision of the throttle
control.
[0069] Next, the configuration of the fuel injection phase
correcting means 106 is shown in FIG. 10. the time constant a of
air response of the cylinder intake air flow rQa is calculated by
an air response time constant calculating means 1001 using equation
(9), based on the cylinder intake air flow rQa calculated by the
intake air flow calculating means 103 and the previously calculated
value rQa[-dt] of the cylinder intake air flow and the target air
flow tQa. Further, in a phase correcting means 1002, the filtering
reference pulse width FKTP is calculated by equation (10) using the
air-response time constant a as a time-filter. FIG. 11 shows a flow
chart of the control of phase correction of the fuel injection in
FIG. 10.
.alpha.=dt.times.{(tQa-rQa)/(rQa-rQa[-dt])} (9)
FKTP={dt/(.alpha.+dt)}.times.KTP +{.alpha./(.alpha.+dt)}.times.FKTP
[-dt] (10)
[0070] where, dt is the calculation cycle and [-dt] is the previous
value by time dt.
[0071] The equations (9) and (10) will be explained by using FIG.
12. At a certain calculation timing, the ratio of the proportional
distribution for determining a point B with respect to points A and
C is calculated by using the target air flow tQa of the point A,
the cylinder intake air flow rQa of the point B and the previously
calculated value rQa [-dt] of the cylinder intake air flow of the
point C. The reference pulse width KTP of a point D and the
previously calculated value FKTP[-dt] of the filtering reference
pulse width of a point E are proportionally distributed by using
the ratio, and the filtering reference pulse width FKTP of a point
X is obtained.
[0072] The width TI of the fuel injection pulse to be finally
injected is different from the reference pulse width KTP by the
equation (1). It is calculated based on the filtering reference
pulse width FKTP calculated by the following equation (11). As a
result, the fuel injection can be performed so as to match the
phase of the cylinder intake air flow rQa.
TI=FKTP.times.COEF.times.GAMMA (11)
[0073] FIG. 13 shows effects of the control in FIG. 1. Now assumed
that an accelerator is opened in the in-cylinder injection engine
which controls the intake air flow based on the torque or the fuel
injection amount. FIG. 13(a) shows effects of the case where the
control of FIG. 1 is not performed. In this case, th efuel
injection amount is calculated based on the reference pulse width
KTP in which the phase correction has not been performed, using the
equation (1). While the variation of the fuel injection amount
according to the variation of the reference pulse width KTP
instantaneously occurs, the variation of the cylinder intake air
flow rQa according to the variation of the target air flow tQa is
behind the variation of the fuel injection amount due to the
time-lag required to pass through the intake pipe or the time-lag
required to vary the inner pressure of the intake pipe.
[0074] As a result, the region is produced where the phases of the
fuel injection and the intake air flow do not match to each other.
Therefor, the A/F ratio becomes rich, and thus the drive feeling
deteriorates. At worst, the engine goes to stop. Next, FIG. 13(b)
shows effects of the case where the control of FIG. 1 is performed.
In the control of FIG. 1, the cylinder intake air flow rQa is
calculated with high accuracy, and the air response time constant
.alpha. is calculated from the time-variation of the cylinder
intake air flow rQa. Then, the filtering reference pulse width FKTP
is calculated by correcting the phase of fuel injection based on
the air response time constant .alpha.. In this case, the fuel
injection amount is calculated based on the filtering reference
pulse width FKTP of which the phase is corrected by equation (11).
Thereby it becomes possible to fit accurately the phases of the
fuel injection and the air intake to each other, and to control the
A/F ratio to be constant even in the transient state of operation.
It is possible to suppress the deterioration of the driving feel or
exhaust by controlling the A/F ratio to be constant.
[0075] FIG. 13(b) shows also the variation of the filtering
reference pulse width FKTP when the target A/F ratio is switched.
In the correction of the fuel injection phase based on the equation
(10), the filtering reference pulse width FKTP is not varied if the
reference pulse width KTP is not varied. Therefore, the filtering
reference pulse width FKTP is not varied even if the target A/F
ratio tAF is switched and the cylinder intake air flow rQa is
increased. In other words, it becomes possible to eliminate the
variation of the fuel injection amount due to the switching of the
target A/F ratio tAF, that is, the occurrence of the torque
shock.
[0076] Hereinafter, alternative of the configuration of FIG. 1 will
be explained every block shown in FIG. 4.
[0077] With regard to the intake air flow calculating means 403, it
should be appreciated that the throttle-passed air flow rQt can be
obtained not only by the air flow sensor as shown in FIG. 5, but by
referring a map with the axes of the engine speed Ne and the
throttle opening rTH as shown in FIG. 14. Instead of the intake
pipe inner pressure estimating means 502 of FIG. 5, an intake pipe
pressure sensor may provided as shown in FIG. 15, in which the
value detected by the intake pipe pressure sensor is input to the
cylinder intake air flow calculating means 503 as the intake pipe
inner pressure rPa. Further, instead of the cylinder intake air
flow calculating means 503, the cylinder intake air flow rQa may be
obtained in the way shown in FIG. 16. the value rQa is calculated
by the equation eliminated the charging efficiency .eta. from the
equation of FIG. 5 in a block 1601. The charging efficiency .eta.
is obtained by referring a map with the axes of the engine speed Ne
and the actual opening rTH of the throttle in a charging efficiency
calculating means 1602 arranged in parallel with the block 1601.
Furthermore, the charging efficiency .eta. may be modeled and the
cylinder intake air flow calculating means 503 may be substituted
for a linear equation.
[0078] In the intake air flow calculating means 403, the
throttle-passed air flow rQt itself may be used as the cylinder
intake air flow rQa without using the control of FIG. 5. It may be
possible to use as the cylinder intake air flow rQa by filtering
the throttle-passed air flow rQt with the time constant .beta. as
shown in equation (12).
rQa={dt/(.beta.+dt)}.times.rQt +{.beta./(.beta.+dt)}.times.rQa[-dt]
(12)
[0079] where, dt is the calculation cycle and [-dt] is the previous
value by time dt.
[0080] Next, as to the target air flow amount calculating means
404, in addition to calculate the target air flow tQa according to
the linear equation (6), it may be possible to calculate the target
air flow tQa according to the linear equation in which the
reference pulse width KTP is substituted for the fuel injection
pulse TI. Further, the target air flow tQa may be obtained in such
a method that as shown in FIG. 17 the stoichiometric target air
flow tSQa is calculated by referring a map with the axes of the
engine speed Ne and the reference pulse width KTP in a
stoichiometric target air flow calculating means 1701, the
stoichiometric target air flow tSQa is multiplied by the target A/F
ratio tAF, and its product is divided by the stoichiometric A/F
ratio or 14.7.
[0081] Next, with respect to the target ttt 405, in addition to
feedback-calculate the target throttle opening tTH based on the
deviation eQa of the air flow, i.e. the difference between the
target air flow tQa and the cylinder intake air flow rQa as shown
in FIG. 8, it may be possible to use such a method that the target
air flow tQa calculated in the target air flow amount calculating
means 404 is converted into the target throttle opening tTH
according to the air flow to opening conversion table 1801.
[0082] Two other examples of the target ttt 405 will be explained
hereinafter.
[0083] One example is shown in FIG. 19. The throttle opening
corresponding to engine speed feedback correction for allowing the
engine speed at idle to follow the target engine speed is firstly
calculated in the control of FIG. 19. The deviation eNe between the
target engine speed tNe and the engine speed Ne is obtained. The
proportional component of a PID control is obtained by multiplying
the deviation eNe by a gain obtained by a block 1901, the
differential component is obtained by multiplying the differential
value of the deviation eNe obtained by a differential circuit 1902
by a differential gain in a block 1903, and the integration
component is obtained by multiplying the integral value of the
deviation eNe obtained by an integral circuit 1904 by an integral
gain in a block 805. Finally, the throttle opening corresponding to
the feedback correction of the engine speed is obtained by summing
the proportional value, the differential value and the integral
value. Further, in a block 1906, the load-corresponding throttle
opening is obtained based on the load SW corresponding to an on/off
state of an air conditioner, a power steering, an electrical load
(consumption current), an electrical radiator fan, etc. Further, in
a block 1907, the throttle opening corresponding to the accelerator
is calculated based on the opening Acc of the accelerator. The
target throttle opening tTH is obtained by adding the throttle
opening corresponding to the engine speed feedback, the throttle
opening corresponding to the loads and the throttle opening
corresponding to the accelerator, multiplying the sum by the target
A/F ratio tAF and dividing the product by the stoichiometric A/F
ratio (=14.7). FIG. 20 shows a flow chart for calculating the
target throttle opening tTH of FIG. 19.
[0084] The other control is shown in FIG. 21. in a block 2101, the
actual reference pulse width rTP is calculated by the equation (8)
based on the engine speed Ne and the cylinder intake air flow rQa
obtained in the intake air flow calculating means 403. While, the
target reference pulse width tTP is calculated by the following
equation (13) based on the reference pulse width KTP, the target
A/F ratio tAF and the stoichiometric A/F ratio.
tTP=KTP.times.(tAF/14.7) (13)
[0085] Then, the deviation eTP between the target reference pulse
width tTP and the actual reference pulse width rTP is obtained. The
proportional component of a PID control is obtained by multiplying
the deviation eTP by a gain obtained by a block 2102, the
differential component is obtained by multiplying the differential
value of the deviation eTP obtained by a differential circuit 2103
by a differential gain in a block 2104, and the integration
component is obtained by multiplying the integral value of the
deviation eTP obtained by an integral circuit 2105 by an integral
gain in a block 2106. Finally, the target throttle opening tTH is
obtained by summing the proportional value, the differential value
and the integral value. FIG. 22 shows a flow chart for calculating
the target throttle opening of FIG. 21.
[0086] The actuator for obtaining the target throttle opening tTH
calaculated by the target throttle opening calculating means 405
may be an electronically controlled throttle.
[0087] Three examples of the fuel injection phase correcting means
406 will be explained hereinafter.
[0088] A first example of the control is shown in FIG. 23. in a
block 2301, the actual reference pulse width rTP is calculated by
the equation (8) based on the engine speed Ne and the cylinder
intake air flow rQa. While, the target reference pulse width tTP is
obtained by multiplying the reference pulse width KTP by the target
A/F ratio tAF and dividing the product by the stoichiometric A/F
ratio (=14.7). the response time constant .alpha. of the actual
reference pulse width rTP is calculated by the following equation
(14) based on the actual reference pulse width rTP, the previously
calculated value rTP[-dt] of the actual reference pulse width and
the target reference pulse width tTP in a response time constant
calculating means 2302.
.alpha.=dt.times.{(tTP-rTP)/(rTP-rTP[-dt])} (14)
[0089] where, dt is the calculation cycle and [-dt] is the previous
value by time dt.
[0090] Then, in a phase correcting means 2303, the filtering
reference pulse width FKTP is calculated by equation (10) using the
air-response time constant .alpha. as a time-filter. FIG. 24 shows
a flow chart of the control of phase correction of the fuel
injection in FIG. 23.
[0091] A second example of the control is a method of using the
ratio of the target air flow tQa to the cylinder intake air flow
rQa as a time-filter. Concretely, the ratio of of the target air
flow tQa calculated by the target air flow amount calculating means
104 to the cylinder intake air flow rQa calculated by the intake
air flow calculating means is calculated by the following equation
(15), and the filtering reference pulse width FKTP is obtained by
multiplying the ratio by the reference pulse width KTP calculated
by the reference pulse width calculating means 101.
FKTP=KTP.times.(rQa/tQa) (15)
[0092] The ratio of the target air flow tQa to the cylinder intake
air flow rQa is a correction term corresponding to time-variation
of the cylinder intake air flow rQa to the target air flow tQa and
becomes a time-filter with respect to the reference pulse width
KTP. Because the correction term is provided, it is possible to fit
the filtering reference pulse width FKTP to the phase of the
cylinder intake air flow rQa.
[0093] Further, in a method in which the ratio of the cylinder
intake air flow rQa and the target air flow tQa is used as a
time-filter according to the equation (15), it may be possible to
use the reference pulse width KTP itself as the filtering reference
pulse width FKTP under the predetermined condition. FIG. 25 shows a
block diagram including the predetermined condition.
[0094] If a first condition 2501 is satisfied that it is within a
predetermined delay time from the switching of the target A/F
ratio, and if a second condition 2502 is also satisfied that the
ratio of the cylinder intake air flow and the target air flow is
within a range defined by a certain threshold value, the reference
pulse width itself can be used as the filtering reference pulse
width in a block 2503. While, if either the conditions 2501 or 2502
is not satisfied, the filtering reference pulse width FKTP is
obtained by multiplying the reference pulse width KTP by the ratio
of the cylinder intake air flow rQa and the target air flow tQa.
Where, AFTH1 and AFTH2 are set to, for example, 95% and 105%,
respectively.
[0095] FIG. 26 shows effects of the control shown in FIG. 25. Now
with regard to the variation of each variable before and after the
switching of the target A/F ratio tAF, the reference pulse width
KTP is not varied, but the target air flow tQa is varied according
to the switching of the target A/F ratio. The cylinder intake air
flow rQa is also varied so as to follow the target air flow tQa. At
this time, the variation of the filtering reference pulse width
FKTP before and after the switching of the target A/F ratio tAF is
decreased due to the effect of the ratio of the cylinder intake air
flow rQa and the target air flow tQa if the control of the equation
(15) is performed as illustrated in FIG. 26(a). Therefore, the
amount of fuel injection is decreased before and after the
switching of the target A/F ratio tAF, and thus the torque shock is
occurred. While, because both the first and second conditions 2501,
2502 are satisfied before and after the switching of the target A/F
ratio tAF if the control of FIG. 25 is performed as illustrated in
FIG. 26(a), the filtering reference pulse width FKTP becomes equal
to the reference pulse width KTP, and thus it is not varied before
and after the switching of the target A/F ratio tAF. Therefore, the
amount of fuel injection becomes constant before and after the
switching of the target A/F ratio tAF, and thus the torque shock is
not occurred.
[0096] In the final example, the constant is set to as a
time-filter. Concretely, the filtering reference pulse width FKTP
is obtained by delaying the reference pulse width KTP by the delay
time Dly. Alternatively, the filtering reference pulse width FKTP
is obtained from the reference pulse width KTP based on a time
constant .gamma. of first-order lag.
FKTP=KTP[-Dly] (16)
FKTP=(dt/(.gamma.+dt)).times.KTP
+(.gamma./(.gamma.+dt)).times.FKTP[-dt] (17)
[0097] where, dt is the calculation cycle and [-dt] is the previous
value by time dt.
[0098] Further, the following methods can be adopted as a method of
setting the delay time Dly and the time constant .gamma. of
first-order lag.
[0099] In one method, the delay time and the time constant of
first-order lag are switched to either of two setting values, in
accordance with either an idle state or an off-idle state, the
accelerator opening Acc, the actual opening rTH of the throttle,
and the cylinder intake air flow rQa.
[0100] In another method, the delay time and the time constant of
first-order lag are obtained by referring to a table with an axis
of a gear position, an engine speed Ne, actual opening rTH of the
throttle, or a cylinder intake air flow rQa.
[0101] In a further method, the delay time and the time constant of
first-order lag are obtained by referring to a map having axes of
an engine speed Ne and actual opening rTH of the throttle, or a map
with axes of an engine speed Ne and a cylinder intake air flow
rQa.
[0102] Further, the value of the time-filter in the fuel injection
phase correcting means 406 may be obtained by learning based on the
operating condition. As a learning method of the time-filter, the
following methods are used.
[0103] In one method, the delay time Dly is obtained by learning
the time from the change in the target throttle opening rTH to the
change in a cylinder intake air flow rQa.
[0104] In another method, the constant time .gamma. of first-order
lag is obtained by learning the change in a cylinder intake air
flow rQa when the target throttle opening rTH is changed.
[0105] Further, the following methods can be adopted as a method of
setting the delay time Dly and the time constant .gamma. of
first-order lag.
[0106] In one method, the delay time and the time constant of
first-order lag is obtained by learning as two setting values, in
accordance with either an idle state or an off-idle state, the
accelerator opening Acc, the actual opening rTH of the throttle,
and the cylinder intake air flow rQa.
[0107] In another method, the delay time and the time constant of
first-order lag is obtained by learning as a reference value of a
table with an axes of the gear position, the engine speed Ne, the
actual opening rTH of the throttle, or a cylinder intake air flow
rQa.
[0108] In a further method, the delay time and the time constant of
first-order lag are obtained by learning as a reference value of a
map with axes of an engine speed Ne and actual opening rTH of the
throttle, or they are obtained by using a map with axes of an
engine speed Ne and a cylinder intake air flow rQa.
[0109] To sum up the above description, there is a key point in
that the phases of the fuel injection and the air intake are fitted
to each other by delaying the response of the fuel injection in the
fuel injection phase correcting means 406. While, in the case that
the target throttle opening tTH is obtained by using the feedback
control shown in FIG. 8 or 21 in the target throttle opening
calculating means 403, the response of the air intake is speeded
up, and thus the phases of the fuel injection and the air intake
are fitted to each other.
[0110] Concretely, a means for setting the feedback constant of the
target throttle opening feedback calculating means in accordance
with the operating condition is provided in the target throttle
opening feedback calculating means shown in FIG. 8 or 21.
[0111] The following apparatus are used as the means for setting
the feedback constant.
[0112] In one apparatus, the feedback constant setting means
switches the feedback constant to either of two setting values, in
accordance with either an idle state or an off-idle state, the
accelerator opening Acc, the actual opening rTH of the throttle,
and the cylinder intake air flow rQa.
[0113] In another apparatus, the feedback constant setting means
obtains the feedback constant by referring to a table with an axis
of the gear position, the engine speed Ne, the actual opening rTH
of the throttle, or the cylinder intake air flow rQa.
[0114] In a further apparatus, the feedback constant setting means
obtains the feedback constant by referring to a map with axes of
the engine speed Ne and the actual opening rTH of the throttle, or
a map with axes of the engine speed Ne and the cylinder intake air
flow rQa.
[0115] FIG. 27 shows effects of the feedback constant setting means
for setting the feedback constant according to the operating
conditions. In the case that there is no feedback constant setting
means as shown in FIG. 27 (a), the variation of the cylinder intake
air flow rQa is delayed and thus the variation of the A/F ratio is
occurred because the feedback constant for the steady state is used
even in the transient state. In addition, the convergence from the
actual A/F ratio to the target A/F ratio is delayed when the target
A/F is switched. While, in the case that there ifeedback constant
setting meanss as shown in FIG. 27(b), the variation of the
cylinder intake air flow rQa is speeded up and thus the A/F ratio
is controlled so as to be constant because the feedback constant
for the transient state is larger than that in the steady state. In
addition, the convergence from the actual A/F ratio to the target
A/F ratio is delayed when the target A/F is switched. By
controlling the A/F ratio so as to be constant, it becomes possible
to suppress the deterioration of the dive feeling and exhaust. In
addition, the convergence from the actual A/F ratio to the target
A/F ratio is speeded up when the target A/F is switched.
[0116] While the described embodiment represents the preferred form
of the present invention, it is to be understood that changes and
variations may be made without departing from the spirit of the
invention.
* * * * *