U.S. patent application number 10/042741 was filed with the patent office on 2003-04-24 for method and apparatus for controlling intake airflow rate of an engine and method for controlling output.
Invention is credited to Aono, Toshihiro, Kadomukai, Yuzo, Kowatari, Takehiko, Usui, Toshifumi.
Application Number | 20030075147 10/042741 |
Document ID | / |
Family ID | 17410135 |
Filed Date | 2003-04-24 |
United States Patent
Application |
20030075147 |
Kind Code |
A1 |
Kowatari, Takehiko ; et
al. |
April 24, 2003 |
Method and apparatus for controlling intake airflow rate of an
engine and method for controlling output
Abstract
There is provided an air flow meter for detecting the flow rate
of air, an electronically controlled throttle for opening and
closing a throttle valve and a calculating device to which a target
engine intake air flow rate, a value detected by the air flow
meter, the position of a throttle valve detected by a throttle
position sensor, and a value detected by an engine speed sensor are
input. The calculating device calculates a time constant of a delay
of response of the air flow rate into the engine, and a air flow
rate passing through the throttle valve to compensate for the delay
of response, and drives the throttle valve such that the flow rate
of air passing through the throttle valve agrees with the
calculated value.
Inventors: |
Kowatari, Takehiko;
(kashiwa-shi, JP) ; Kadomukai, Yuzo; (Ishioka-shi,
JP) ; Aono, Toshihiro; (Niihari-gun, JP) ;
Usui, Toshifumi; (Hitachinaka-shi, JP) |
Correspondence
Address: |
Mattingly Stanger & Malur PC
104 Hume Avenue
Alexandria
VA
22301
US
|
Family ID: |
17410135 |
Appl. No.: |
10/042741 |
Filed: |
February 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10042741 |
Feb 22, 2001 |
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09397855 |
Sep 17, 1999 |
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6199537 |
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Current U.S.
Class: |
123/399 |
Current CPC
Class: |
F02D 11/105 20130101;
F02D 2041/0017 20130101; Y02T 10/40 20130101; F02D 2041/1431
20130101; F02D 41/187 20130101; Y02T 10/47 20130101; F02D 2041/1424
20130101; F02D 41/0065 20130101 |
Class at
Publication: |
123/399 |
International
Class: |
F02D 011/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 18, 1998 |
JP |
10-264927 |
Claims
What is claimed is:
1. A method for controlling the flow rate of intake air to an
engine by controlling the opening of an electronically controlled
throttle comprising the steps of: calculating a command value for
the flow rate of intake air to the engine from a throttle position
signal of the electronically controlled throttle provided in a
suction pipe, an air flow rate signal detected by an air flow meter
provided upstream of the electronically controlled throttle valve
and an engine speed signal; and calculating a target engine intake
air flow rate by finding an over-shooting amount for said
electronically controlled throttle valve.
2. A method according to claim 1, wherein an over-shooting
operation includes; determining a time constant of a delay of
response based on the throttle position signal from the
electronically controlled throttle, the signal of the air flow
meter, the engine speed signal and the target engine intake air
flow rate to be taken into the cylinders of the engine by a
calculating device; calculating a target signal for an air flow
meter for compensating for the delay of response based on the
determined time constant of the delay of response; and driving the
electronically controlled throttle such that the signal of the air
flow rate meter agrees with the target signal.
3. A method for controlling the flow rate of intake air to an
engine by controlling the opening of an electronically controlled
throttle comprising the steps of: calculating an engine intake air
flow rate from a throttle valve position signal, an air flow rate
signal of air flowing through a suction pipe and an engine speed
signal; calculating an intake air flow rate command value in
accordance with an amount of fuel injection determined based on
said intake air flow rate; calculating a throttle valve position
signal by adding an over-shooting amount to said intake air flow
rate command value; and repeating above calculations by calculating
an engine intake air flow rate from the throttle valve position
signal, air flow rate signal and the engine speed signal.
4. A method for controlling the flow rate of intake air to an
engine by controlling the opening of an electronically controlled
throttle comprising the steps of: calculating an exhaust gas
recirculation flow rate of exhaust gas recirculation for
introducing the exhaust gas of the engine into the intake pipe
based on a throttle valve position signal, an air flow rate signal
of air flowing through the intake pipe and an engine speed signal;
calculating a position signal of an exhaust gas recirculation flow
rate adjusting valve (referred to as "EGR valve") by adding an
over-shooting amount to a value corresponding to said exhaust gas
recirculation flow rate; and repeating said calculation by
calculating an exhaust gas recirculation flow rate from said
throttle valve position signal, air flow rate signal and engine
speed signal.
5. A method according to claim 3 or 4, wherein said over-shooting
amount is a compensating value determined in advance for the delay
of change of the intake air flow rate relative to the operation of
the electronically controlled throttle.
6. A method for controlling the flow rate of intake air to an
engine having an electronically controlled throttle provided in a
suction pipe for introducing air in the internal combustion engine
for controlling air flow rate, an air flow meter provided upstream
of the electronically controlled throttle for detecting the air
flow rate, an engine speed meter for detecting engine speed, a
calculating device and a flow rate adjusting valve for an exhaust
gas recirculation device for introducing exhaust gas from the
internal combustion engine into the intake pipe comprising the
steps of: determining a time constant for a first delay of response
based on a throttle position signal from the electronically
controlled throttle, an air flow meter signal, an engine speed
signal, the flow rate of intake air to be taken into the cylinders
of the engine and the flow rate of the exhaust gas to be taken into
the cylinder of the engine by a calculating device; calculating a
target signal for the air flow rate meter to compensate for the
delay of response based on the determined time constant for the
first delay of response; driving the electronically controlled
throttle such that the signal from the air flow rate meter agrees
with the target signal; determining a time constant for a second
delay of response; and driving the flow rate adjusting valve based
on the determined time constant for the second delay of response to
compensate for the delay of response of the exhaust gas that flows
into the engine.
7. A device for controlling the flow rate of intake air to an
engine comprising: an electronically controlled throttle provided
in a suction pipe for introducing air in the engine to control air
flow rate; an air flow rate meter provided upstream of the
electronically controlled throttle valve to detect the air flow
rate an engine speed meter to detect engine speed; and a
calculating device which calculates the flow rate of intake air to
the engine based on a throttle valve position signal, an air flow
rate signal and an engine speed signal, calculates an intake air
flow rate command value based on said intake air flow rate,
calculates a throttle valve position signal by adding an
over-shooting amount to said intake air flow rate command value and
repeats said calculation by calculating an engine intake flow rate
based on the throttle valve position signal, the air flow rate
signal and engine speed signal.
8. A device according to claim 7, wherein said calculating device
calculates an amount of fuel injection based on said engine intake
air flow rate and calculates said intake air flow rate command
value in accordance with said amount of fuel injection.
9. A device for controlling the flow rate of intake air to an
engine comprising: an electronically controlled throttle provided
in a suction pipe for introducing air in the internal combustion
engine to control air flow rate; an air flow rate meter provided
upstream of the electronically controlled throttle to detect the
air flow rate; an engine speed meter to detect engine speed; a flow
rate adjusting valve for an exhaust gas recirculation device to
introduce exhaust gas from the engine into the suction pipe; a
calculating device which determines a time constant for a first
delay of response based on a throttle position signal from the
electronically controlled throttle, an air flow meter signal, an
engine speed signal, the flow rate of intake air to be taken into
the cylinders of the engine and the flow rate of the exhaust gas to
be taken into the cylinder of the engine, calculates a target
signal for the air flow meter to compensate for the delay of
response based on the determined time constant for the first delay
of response, drives the electronically controlled throttle such
that the signal from the air flow meter agrees with the target
signal, determines a time constant for a second delay of response
and drives the flow rate adjusting valve based on the determined
time constant for the second delay of response to compensate for
the delay of response of the exhaust gas that flows into the
engine.
10. A method for controlling the output of an engine in which
output required for an engine is controlled by a command from an
acceleration pedal comprising the steps of: determining an amount
of fuel injection in advance based on an intake air flow rate;
determining an intake air flow rate command value based on said
amount of fuel injection; and determining a target intake air flow
rate by adding an over-shooting amount transiently to said intake
air flow rate command value to control the opening of an
electronically controlled throttle.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an accurate method and
apparatus for controlling the flow rate of intake air of an
engine.
[0002] There are two general types of methods for controlling fuel
injection type engines. One is the air-first control system in
which air taken into the cylinders of an engine (hereinafter
referred to as "engine intake air flow rate. The result of
measurement by an air flow meter provided in a intake pipe is
simply referred to as "air flow rate") is measured and then the
fuel is injected in an amount in accordance with the engine intake
air flow rate. The other is the fuel-first control system in which
an amount of fuel is defined in advance and an engine intake air
flow rate in accordance with the same is supplied to the
engine.
[0003] In either of the systems, it is important to achieve an air
fuel ratio that realizes a state of combustion desirable for
reduction of harmful components in exhaust gas and reduction of the
amount of fuel consumption.
[0004] Referring to the air-first control system, methods for
controlling an internal combustion engine aimed at maintaining an
air fuel ratio accurately during a transient time are disclosed in,
for example, Japanese patent Application Laid-Open 104930/1990
(hereinafter "first prior art") and Japanese patent Application
Laid-Open 134136/1992 (hereinafter "second prior art").
[0005] In the first prior art, a technique is disclosed in which an
amount of fuel injection is determined by calculating a flow rate
of intake air to an engine in accordance with a model of a intake
pipe. In this case, a delay in an engine intake air flow rate at
the time of a movement of a throttle valve caused by an accelerator
pedal is calculated using pressure and engine speed information,
and the amount of fuel injection is corrected in association with
the delay of air. Since this method has had a problem in that
amount for fuel correction is slow because the correction is
calculated after a change in the opening of the throttle valve
occurs, the second prior art provides a fuel injection controller
by introducing a delay to the opening of the throttle valve
relative to an acceleration pedal stepping-on amount to reduce the
effect of the correction delay.
SUMMARY OF THE INVENTION
[0006] However, both of the conventional techniques are intended
for the air-first control system and have the following problems
when used for engines utilizing the fuel-first type control, e.g.,
direct injection in cylinder engines (hereinafter referred to "DI
engines" which imply both of spark ignition type and compression
ignition type DI engines). In a DI engine, as its name implies,
fuel is directly injected into the combustion chamber of the
engine. It is therefore an engine convenient for fuel-first type
control because an amount of fuel to be used for one cycle of
combustion can be supplied each time. However, since the
conventional technique is intended for the air-first type control
system, there is a need for an apparatus and a method which can
freely control the intake air flow rate of an engine for engines
utilizing the fuel-first type control.
[0007] In the case of air-first control, the output of an engine is
changed through a long process that starts with the changing of the
opening of the throttle valve followed by a change in the pressure
in the intake pipe, a change in the amount of engine intake air,
the changing of the fuel flow rate in accordance with the air flow
rate and an increase or decrease in the engine output. Since the
output of an engine is mainly proportionate to the amount of fuel
injection, such control can result in poor engine response because
the amount of fuel injection must be changed after the engine
intake air flow rate is changed even when the output is to be
increased or decreased in a short period. This problem has not been
regarded as a significant problem in conventional single point
injection (SPI) systems in which fuel is injected upstream of the
intake pipe (upstream of the throttle valve) and multi-point
injection (MPI) systems in which fuel is injected into a manifold
because the time for fuel to reach the combustion chamber of the
engine is similar to the time for engine intake air from rate to
change, which problem has been difficult to solve.
[0008] In the case of a DI engine, however, since it can supply an
amount of fuel with better response to a delay of air compared to
an SPI or MPI engine, the air-first type control system hinders the
improvement of response because of the delay of air in one aspect
thereof. While this can be solved by employing the fuel-first type
control system, no controller and method have been provided which
cause an air flow rate to follow up an amount of fuel injection
with high accuracy.
[0009] Meanwhile, from the viewpoint of improved safety of
automobiles, vehicle movement controlling techniques have been
developed such as traction control to prevent slipping of wheels by
adjusting engine output, and intelligent cruise control for
preventing a collision with a car in front by adjusting engine
output. Further, engine output is sometimes controlled in
accordance with a gear change for automatic transmission, and
engine output control at high speed and with high accuracy is
required for such vehicle movement control.
[0010] Further, recent environmental regulations permit no increase
in harmful components in exhaust gas attributable to fluctuation of
an air fuel ratio, which has resulted in a need for reducing
fluctuation of an air fuel ratio during acceleration and
deceleration. This has resulted in a need for a method and an
apparatus for controlling not only fuel but also an engine intake
air flow rate.
[0011] The output of an engine is directly affected by the amount
of fuel which is a source of thermal energy. That is, the output of
an engine is determined by the amount of fuel. In the conventional
techniques intended for the air-first control, the output of an
engine has been indirectly adjusted with air flow rate. Therefore,
accurate adjustment of engine output has involved repeated
operations of varying the air flow rate first, injecting fuel in
accordance therewith, observing the output and appropriately
varying the air flow rate again in the case of an excess or
shortage, and this has made it difficult to control the output
accurately. In the case of a fuel-first control type engine, since
the amount of fuel which determines the output is first determined,
the engine output can be controlled with high accuracy only by
controlling the intake air flow rate of the engine. However, no
apparatus and method have been provided which transiently control
the intake air flow rate of an engine with high accuracy.
[0012] It is an object of the present invention to provide an
apparatus and a method for controlling engine intake air and a
method for controlling output in which in order to control the
output of an engine with high accuracy, when the intake air flow
rate of the engine is determined (i.e., the output is determined)
in accordance with the amount of fuel, an actual engine intake air
flow rate is supplied accurately in accordance therewith.
[0013] In order to solve the above problems, there is provided an
air flow rate controller which has an air flow rate detecting
device for detecting an air flow rate, a throttle valve
opening/closing device for opening and closing a throttle valve,
and a calculating device to which the detection value of the air
flow rate detecting device, the position of the throttle valve, the
engine speed and a target engine intake air flow rate are input and
in that the calculating device drives the throttle valve
opening/closing device in advance such that the engine intake air
flow rate agrees with the target engine intake air flow rate.
[0014] There is also provided a method for controlling engine
intake air flow rate in which a time constant of a delay of
response of the air flow rate is calculated and the throttle valve
is controlled such that a delay of the engine intake air flow rate
is corrected based on the calculated time constant to cause the
engine intake air flow rate to follow up the target engine intake
air flow rate.
[0015] The present invention specifically provides the methods and
apparatuses described below.
[0016] The present invention provides a method for controlling the
flow rate of intake air to an engine by controlling the opening of
an electronically controlled throttle, in which a command value for
the flow rate of intake air to the engine is calculated from a
throttle position signal of the electronically controlled throttle
provided in a intake pipe, an air flow rate signal detected by an
air flow rate meter provided upstream of the electronically
controlled throttle and an engine speed signal and in which a
target engine intake air flow rate is calculated by finding an
over-shooting amount for said electronically controlled throttle
valve.
[0017] The present invention further provides a method for
controlling the flow rate of intake air to an engine including an
over-shooting operation in which a throttle position signal from
the electronically controlled throttle, the signal of the air flow
rate meter, the engine speed signal and the target engine intake
air flow rate to be taken into the cylinders of the engine are
input to a calculating device and in which the calculating device
determines a time constant of a delay of response, calculates a
target signal for an air flow rate meter for compensating for the
delay of response based on the determined time constant of the
delay of response and drives the electronically controlled throttle
such that the signal of the air flow rate meter agrees with the
target signal.
[0018] The present invention provides a method for controlling the
flow rate of intake air to an engine by controlling the opening of
an electronically controlled throttle, in which an engine intake
air flow rate is obtained from a throttle valve position signal, an
air flow rate signal of air flowing through a suction pipe and an
engine speed signal; an intake air flow rate command value is
calculated in accordance with an amount of fuel injection
determined based on said intake air flow rate; a throttle valve
position signal is obtained by adding an over-shooting amount to
said intake air flow rate command value; and said calculation is
repeated by obtaining an engine intake air flow rate from the
throttle valve position signal, air flow rate signal and the engine
speed signal.
[0019] The present invention further provides a method for
controlling the flow rate of intake air to an engine in which said
over-shooting amount is a compensating (correcting) value
determined in advance for the delay of change of the intake air
flow rate relative to the operation of the electronically
controlled throttle.
[0020] The present invention provides a method for controlling the
flow rate of intake air to an engine by controlling the opening of
an electronically controlled throttle, in which an exhaust gas
recirculation flow rate of exhaust gas recirculation for
introducing the exhaust gas of the engine into a suction pipe is
obtained based on a throttle valve position signal, an air flow
rate signal of air flowing through the suction pipe and an engine
speed signal; a position signal of an EGR valve is obtained by
adding an over-shooting amount to a value corresponding to said
exhaust gas recirculation flow rate; and said calculation is
repeated by obtaining an exhaust gas recirculation flow rate from
said throttle valve position signal, air flow rate signal and
engine speed signal.
[0021] The present invention provides a method for controlling the
flow rate of intake air to an engine having an electronically
controlled throttle provided in a suction pipe for introducing air
in the internal combustion engine for controlling air flow rate, an
air flow rate meter provided upstream of the electronically
controlled throttle for detecting the air flow rate, an engine
speed meter for detecting engine speed, a calculating device and an
EGR valve for an exhaust gas recirculation device for introducing
exhaust gas from the internal combustion engine into the suction
pipe, in which a throttle position signal from the electronically
controlled throttle, an airflow rate meter signal, an engine speed
signal, the flow rate of intake air to be taken into the cylinders
of the engine and the flow rate of the exhaust gas to be taken into
the cylinder of the engine are input to the calculating device; the
calculating device determines a time constant for a first delay of
response, calculates a target signal for the air flow rate meter to
compensate for the delay of response based on the determined time
constant for the first delay of response and drives the
electronically controlled throttle such that the signal from the
air flow rate meter agrees with the target signal; and the
calculating device determines a time constant for a second delay of
response and drives the EGR valve based on the determined time
constant for the second delay of response to compensate for the
delay of response of the exhaust gas that flows into the
engine.
[0022] The present invention provides a device for controlling the
flow rate of intake air to an engine having an electronically
controlled throttle provided in a suction pipe for introducing air
in the engine for controlling air flow rate, an air flow rate meter
provided upstream of the electronically controlled throttle valve
for detecting the air flow rate and an engine speed meter for
detecting engine speed, having a configuration including a
calculating device which obtains the flow rate of intake air to the
engine from a throttle valve position signal, an air flow rate
signal and an engine speed signal, calculates an intake air flow
rate command value based on said intake air flow rate, obtains a
throttle valve position signal by adding an over-shooting amount to
said intake air flow rate command value and repeats said
calculation by obtaining an engine intake flow rate from the
throttle valve position signal, the air flow rate signal and engine
speed signal.
[0023] The present invention provides a device for controlling the
flow rate of intake air to an engine having an electronically
controlled throttle provided in a suction pipe for introducing air
in the engine for controlling air flow rate, an air flow rate meter
provided upstream of the electronically controlled throttle valve
for detecting the air flow rate and an engine speed meter for
detecting engine speed, having a configuration including a
calculating device which obtains a flow rate of intake air to the
engine from a throttle valve position signal, an air flow rate
signal and an engine speed signal, obtains an amount of fuel
injection from said engine intake air flow rate, calculates an
intake air flow rate command value in accordance with said amount
of fuel injection, obtains a throttle valve position signal by
adding an over-shooting amount to said intake air flow rate command
value and repeats said calculation by obtaining an engine intake
flow rate from the throttle valve position signal, the air flow
rate signal and engine speed signal.
[0024] The present invention provides a device for controlling the
flow rate of intake air to an engine having an electronically
controlled throttle provided in a suction pipe for introducing air
in the engine for controlling air flow rate, an air flow rate meter
provided upstream of the electronically controlled throttle for
detecting the air flow rate, an engine speed meter for detecting
engine speed, a calculating device and an EGR valve for an exhaust
gas recirculation device for introducing exhaust gas from the
engine into the suction pipe, having a configuration including a
calculating device to which a throttle position signal from the
electronically controlled throttle, an air flow rate meter signal,
an engine speed signal, the flow rate of intake air to be taken
into the cylinders of the engine and the flow rate of the exhaust
gas to be taken into the cylinder of the engine are input, in which
the calculating device determines a time constant for a first delay
of response, calculates a target signal for the air flow rate meter
to compensate for the delay of response based on the determined
time constant for the first delay of response and drives the
electronically controlled throttle such that the signal from the
air flow rate meter agrees with the target signal and in which the
calculating device determines a time constant for a second delay of
response and drives the EGR valve based on the determined time
constant for the second delay of response to compensate for the
delay of response of the exhaust gas that flows into the
engine.
[0025] The present invention provides a method for controlling the
output of an engine in which output required for an engine is
controlled by a command from an acceleration pedal, in which the
torque of an engine is controlled by determining an amount of fuel
injection in advance based on an intake air flow rate obtained in a
calculating portion, then determining an intake air flow rate
command value based on said amount of fuel injection, and
determining a target intake air flow rate by adding an
over-shooting amount transiently to said intake air flow rate
command value to control the opening of an electronically
controlled throttle.
[0026] According to the invention, once a target engine intake air
flow rate is given, a controller predicts the engine intake air
flow rate and controls the opening of a throttle valve such to
achieve the best approximation of the target engine intake air flow
rate. Further, when a target engine intake EGR flow rate is given,
an EGR valve is driven such that the EGR valve also achieves the
target intake EGR flow rate. As a result, an actual engine intake
air flow rate can quickly and accurately reach the target. It is
therefore possible to obtain an intake air flow rate which is
preferably used in a fuel-first control engine.
[0027] This also makes it possible to control the output of an
engine taking advantage of the fuel-first type control system.
BRIEF DESCRIPTION OF THE DRAWING
[0028] FIG. 1 is a diagram showing a method of control as a
whole.
[0029] FIG. 2 is a diagram showing a method for compensating for a
delay in suction.
[0030] FIG. 3 is a diagram showing a method for obtaining a target
position of a throttle valve.
[0031] FIG. 4 is a diagram showing a method for obtaining the
pressure inside a suction pipe with improved accuracy.
[0032] FIG. 5 is a diagram showing a method for obtaining a flow
rate of air passing through a throttle valve with improved
accuracy.
[0033] FIG. 6 is a diagram showing a method for predicting a change
in an engine speed.
[0034] FIG. 7 is a view of an integrated apparatus.
[0035] FIG. 8 is a view of an integrated apparatus mounted on an
engine.
[0036] FIG. 9 is a diagram showing an embodiment in which the
present invention is applied to an engine with an EGR device.
[0037] FIG. 10 is an illustration of a delay in the flow rate of
the air taken into an engine.
[0038] FIG. 11 is a diagram showing the characteristics of an
engine intake air flow rate in an application of the present
invention.
[0039] FIG. 12 is a diagram showing the characteristics of an
engine intake air flow rate in an application of the present
invention to an engine with an EGR.
[0040] FIG. 13 is a view of an integrated apparatus mounted on an
engine with an EGR.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0041] An embodiment of a controller and a control method according
to the present invention will now be described using FIG. 1. The
configuration will be described first. Air taken into an engine 11
passes an air cleaner 9 and passes a throttle valve 13 to be taken
into the engine 11. Exhaust gas from the engine 11 is released to
the atmosphere through an exhaust pipe 15. The throttle valve 13 is
a part of an electronically controlled throttle 8 and is driven by
an electric motor. The opening of the throttle valve 13 is detected
by an throttle position sensor which is not shown. An air flow
meter 7 is positioned between the throttle valve 13 and the air
cleaner 9 to measure the air flow rate in the position of the air
flow rate meter 7. In the embodiment, a hot wire type air flow
meter was used as the air flow rate meter. The engine speed of the
engine 11 is determined based on a signal detected by a crank angle
sensor 12.
[0042] Algorithm for the controller will now be described. When a
driver operates on the accelerator pedal, a signal from an
accelerator pedal position sensor which is not shown is taken into
a block 1 to calculate the torque (output) required for the engine.
Required information on the torque from other sensors which are not
shown, e.g., engine required torque for traction control, is also
input to the block 1 to be included in the calculation of the
required engine torque. A block 2 calculates an amount of fuel
injection based on the engine required torque calculated in the
block 1 and outputs a fuel injection amount signal to an injector
control portion for injecting fuel which is not shown. A block 3
calculates the flow rate of intake air to be taken into cylinders
of the engine based on the amount of fuel injection calculated in
the block 2 and outputs it as an engine intake air flow rate
command. A block 4 calculates the engine speed of the engine 11
obtained by the crank angle sensor 12 and determines a time
constant for a delay of the engine intake air flow rate relative to
the flow rate of the air passing through the throttle valve based
on the engine speed. Once the time constant of delay is determined,
a flow rate of air passing through the throttle valve required to
reach the engine intake air flow rate command is calculated using
an inverse function of a transfer function representing a change in
the intake air flow rate of the engine from a change in the
throttle valve opening. A block 5 calculates a throttle valve
opening that results in the flow rate of the air passing through
the throttle valve as calculated in the block 4 based on a signal
output by the air flow rate meter 7 and a throttle valve opening
signal 10 outputted from the throttle position sensor. The block 5
further controls the opening of the electronically controlled
throttle 8 such that the calculated throttle valve opening is
achieved.
[0043] The operation of the block 4 will be described further using
FIG. 2. Engine speed information obtained by the crank angle sensor
12 is input in the a block 4a which calculates a time constant
(.tau.) of delay. This time constant depends on the capacity of the
intake pipe downstream of the throttle valve and the engine speed
(N). Specifically, it can be calculated using Equation 1.
.tau.=C1(N)/N (Equation 1)
[0044] N represents the engine speed and C1 represents a
coefficient.
[0045] The coefficient C1 is a function of N and can be
approximated using a quadratic of N expressed by Equation 2.
C1(N)=a2.multidot.N.sup.2+a1.multidot.N+a0 (Equation 2)
[0046] a0-a2 are constants which are empirically defined.
[0047] When it is desired to reduce the burden on the calculating
device, C1 may be stored as a map of N to allow reference to
C1.
[0048] Next, a block 4b uses the time constant of delay (.tau.) to
filter the engine intake air flow rate command with the following
transfer function, and this provides a command for the flow rate of
air passing through the throttle valve. Equation 3 shows the
function for filtering.
G(s)=(.tau.s+1)/(C2s+1) (Equation 3)
[0049] C2 is a coefficient, and s is a Laplace operator. While C2
may be empirically defined, it should be preferably equal to or
smaller than {fraction (1/10)} of .tau.. The result of the
calculation in the block 4b is sent to the block 5.
[0050] The block 5 will be described in detail using FIG. 3. The
air flow rate signal from the air flow meter 7 is input to the
block 5a which linearizes the signal from the air flow meter. The
signal output from the air flow meter exhibits a high sensitivity
to a low flow rates and a low sensitivity to a high flow rate.
Therefore, in order to convert it into a flow rate, it is necessary
to use the conversion formula represented by Equation 4 or to store
the relationship between the output and the flow rate as a table
map in advance and to convert the output signal of the air flow
meter into an actual flow rate.
Q=b4.multidot.V.sup.4+b3.multidot.V.sup.3+b2.multidot.V.sup.2+b1.multidot.-
V+b0 (Equation 4)
[0051] b0-b4 are constants which are empirically defined, and V
represents the output of the air flow rate meter.
[0052] The actual flow rate Q is used as the current flow rate of
air passing through the throttle valve 13. Theoretically, there is
a delay, due to the transport of air and due to the detection lag
of the air flow meter, but this delay is small and is ignored in
this embodiment.
[0053] A block 5b obtains any difference between the current flow
rate of air passing through the throttle valve 13 and the command
for the flow rate of air passing through the throttle valve 13
obtained in the block 4 and supplies a gain to this difference to
obtain a correction amount for the throttle valve opening. A block
5c adds a signal 10 from the current throttle valve opening sensor
to the throttle valve opening correction amount obtained in the
block 5b to determine a throttle valve position command. Further,
throttle valve position control is carried out aiming at the
determined throttle valve position.
[0054] A block 6 obtains throttle valve movement and air flow rate
information from block 5 and .tau. from block 4 to calculate the
air flow rate actually taken into the engine. The result is send to
the block 2 and sends it to the block 2. The block 2 corrects the
amount of fuel injection if necessary.
[0055] The operation of the throttle valve of this apparatus will
be described using FIG. 11. In FIG. 11, the driver stepwise changes
the position of the accelerator pedal and, as a result, a
controller 801 issues a command for an increase in the fuel flow
rate and stepwise increases in the engine intake air flow rate at a
point in time t0 to cause stepwise increase of engine torque. The
broken line in FIG. 11(c) represents the engine intake air flow
rate command. The engine intake air flow rate command is sent to an
integrated calculating device 601 through a bus 701 to adjust the
opening (position) of the throttle valve. FIG. 11(a) shows the
throttle valve opening. The throttle valve opening operates with an
over-shoot from the ultimate opening. The over-shooting amount and
over-shooting time are determined by the time constant of delay.
Such an operation of the throttle valve can cause near stepwise
changes in the engine intake air flow rate that follow up the
target as indicated by the solid line in FIG. 11(c) The actual
engine intake air flow rate can be controlled at a high speed
without the step operation by operating the throttle valve 13 in
advance based on the time constant of delay if the target engine
intake air flow rate is supplied.
[0056] In the above-described control method, the block 5b has
obtained a correction amount for the throttle valve opening from
the difference between the current flow rate of air passing through
the throttle valve 13 and the command for the flow rate of air
passing through the throttle valve obtained in block 4 such that
the flow rate of air passing through the throttle valve 13 agrees
with the signal of the air flow meter. However, since the throttle
valve opening and the flow rate are in a non-linear relationship
and the non-linearity is significant especially at low flow rates,
this method can take time to converge. The following method is
adopted in place of the block 5 to control the throttle valve
opening at a higher speed and with higher accuracy.
[0057] For this purpose, a technique is used in which the current
pressure in the intake pipe (the pressure in the intake pipe
between the throttle valve and the engine) is first estimated and a
throttle valve opening that achieves a target flow rate of air
passing through the throttle valve is predicted.
[0058] FIG. 4 shows a method for finding the pressure in the intake
pipe. The output of the air flow meter (with a symbol "Mat_sensor)
is used as the input. A block 112h converts the output of the air
flow meter into a flow rate using Equation 4 or a table map. A
block 112a makes a selection on which of a value calculated in a
block 111h and the output of the block 112h is to be used. The
output of the block 112h is selected to estimate the current
pressure in the intake pipe. The output of the block 112a is sent
to a block 112b to calculate the rate of change of pressure of the
pressure inside the intake pipe (.sigma.Pman/.sigma.t). The rate of
change of the pressure is calculated using Equation 5.
.sigma.Pman/.sigma.t=Mat(RT/V)-Map_cal (Equation 5)
[0059] Pman represents the pressure inside the intake pipe; t
represents time; Mat represents the flow rate of air passing
through the throttle valve; R represents a gas constant; V
represents the volume between the throttle and engine; and Map_cal
represents the engine intake air flow rate. The result is subjected
to time integration in a block 112c to calculate the change of
pressure .DELTA.Pman. A block 112d obtains the sum of the change of
pressure .DELTA.Pman and a previous calculated value Pman1 and
newly stores it as Pman2. Pman2 is stored in a block 112e to be
used for the next calculation in the block 112e. The output of the
block 112d is sent to a block 112g for calculating the engine
intake air flow rate and a block 112f for calculating a
coefficient. The block 112f also receives the engine speed
information N at the same time to calculate a coefficient Ev.
[0060] The coefficient Ev varies depending on the engine speed (N)
and can be approximated using a quadratic of N expressed by
Equation 6.
Ev(N)=e2.multidot.N.sup.2+e1.multidot.N+e0 (Equation 6)
[0061] e0-e2 are constants which are empirically defined.
[0062] When it is desired to reduce the burden on the calculating
device, Ev may be stored as a table map of N to allow reference to
Ev(N).
[0063] The coefficient Ev is sent to the block 112g for calculating
the engine intake air flow rate (Map_cal). In the block 112g,
Equation 7 is calculated.
Map_cal=N/120*V*Ev/R/Tman*Pman (Equation 7)
[0064] Tman represents the temperature of the air inside the intake
pipe. The temperature of the air inside the intake pipe may be
similar to the ambient air temperature and is sent by the bus 701.
The result of the block 112g is sent to the block 112b for
calculating the change of pressure to be used for the next
calculation.
[0065] The pressure inside the intake pipe Pman obtained in the
block 112d is used for the calculation of the flow rate of air
passing through the throttle valve.
[0066] FIG. 5 shows a method for calculating the flow rate of air
passing through the throttle valve.
[0067] The flow rate of air passing through the throttle valve not
only depends on the throttle valve opening (.alpha.) but also
varies depending on the pressure inside the intake pipe Pman and
the atmospheric pressure Pamb. A method is adopted here in which
the flow rate of air passing through the throttle valve is obtained
by multiplying a flow rate obtained from .alpha. by a coefficient
determined by Pman and Pamb. When the throttle valve opening
.alpha. is input, a block 111i calculates a flow rate a1 as a cubic
algebraic expression of .alpha. and sends it to a calculation
portion 111h. The coefficients c0, c1, c2, c3 of the cubic
algebraic expression are empirically defined and are input in
advance. Referring to the manifold pressure Pman_cal and the
atmospheric pressure Pamb, the magnitudes of them are compared in
comparison portions 111a-111c; a coefficient 1 is obtained when the
manifold pressure Pman is smaller than 1/2 of the atmospheric
pressure Pamb; the coefficient is calculated according to a
coefficient calculating portion 111e when it is equal to greater
than the same and smaller than Pamb; the coefficient is determined
by a coefficient calculating portion 111f when the manifold
pressure Pman is smaller than twice the atmospheric pressure and is
determined by a coefficient calculating portion 111g when greater
than twice the atmospheric pressure; and the result is sent to the
calculating portion 111h. As the atmospheric pressure Pamb,
Pman_cal is stored when the throttle is fully opened, and the value
is used. The calculating portion 111h obtains the product of the
coefficient a1 according to the position of the throttle valve and
the coefficient a2 of the 111d-111g to calculate the flow rate of
air passing through the throttle valve Mat_cal. To reduce the
burden on the calculating device, a table map may be used to which
the pressure inside the intake pipe, the atmospheric pressure and
the throttle valve opening are input and which refers to the flow
rate of air passing through the throttle valve.
[0068] While the resultant flow rate of air passing through the
throttle valve Mat_cal is acceptable if it agrees with the command
for the flow rate of air passing through the throttle valve
obtained in the block 4, if they do not agree, the throttle valve
opening .alpha. input to the block 111a is virtually varied to
carry out calculations in the blocks 111a-h to identify the
throttle valve opening .alpha. with which Mat_cal becomes
closest.
[0069] To obtain a flow rate of air passing through the throttle
valve Mat_cal with improved accuracy, Mat_cal may be selected in
the block 112a (FIG. 4) after the calculations in the blocks 111a-i
to calculate the blocks 112b-g and the pressure inside the suction
pipe Pman_cal may be calculated in the blocks 111a-h in FIG. 2
again to obtain the flow rate of air passing through the throttle
valve Mat_cal. In this case, while the current engine speed 113 may
be used as the engine speed information N used in the block 112f,
it is better to pay attention to fluctuation of the engine speed in
order to calculate a coefficient Ev more accurately.
[0070] For this purpose, the calculation for predicting the engine
speed shown in FIG. 6 is used. First, a block 402 predicts the
engine torque. The result of the engine intake air flow rate
Map_cal obtained in the block 112g, a target air fuel ratio
.lambda. and the current engine speed (the symbol N[0] in FIG. 6)
are used for this purpose. The target air fuel ratio .lambda. is a
constant value or is set by obtaining information from the control
portion for determining the amount of fuel injection. Engine torque
Teng is calculated using a table map whose parameters are three
variables, i.e., .lambda., N[0] and Map_cal.
[0071] Next, the result of the engine torque Teng obtained in the
block 402 is multiplied by the inverse number of the inertia J. The
inertia J is supplied by a control portion that monitors the state
of the gear ratio of the vehicle because it varies depending on the
gear ratio of the driving and transmission mechanism of the vehicle
which is not shown. More conveniently, the inertia J may be set as
an empirically obtained constant value, although the accuracy is
reduced. The result will correspond to the change in angular
velocity of the engine. It can be subjected to time integration to
obtain the engine speed, thereby making it possible to predict the
engine speed at the time of a change in the throttle valve opening
.alpha..
[0072] This makes it possible to predict the flow rate of air
passing through the throttle valve at the time of a change in the
throttle valve opening .alpha. and to cause the throttle valve
position to follow up a command for the flow rate of air passing
through the throttle valve with accuracy and at a high speed.
[0073] According to the above-described method of control, while
the air flow meter 7, electronically controlled throttle 8 and
calculating device 14 my be separately provided as shown in FIG. 1
above, they may be integrated. Especially, when the air flow meter
7 and the throttle valve are close to each other, the air flow
meter 7 can detect the flow rate of air passing through the
throttle valve without delay to improve the present method of
control further. Further, by integrating also the calculating
device, the connection between the calculating device 14, air flow
meter 7 and electronically controlled throttle 8 is simplified.
[0074] FIG. 7 shows an apparatus in which an air flow meter, an
electronically controlled throttle and a calculating device are
integrated (hereinafter "integrated apparatus"). The integrated
apparatus 610 is constituted by a calculating device 601, an air
flow rate meter 602 connected thereto, a throttle valve 603, an
electric motor 604 for driving the throttle valve, a driving
portion 605 incorporating a train of gears and a spring mechanism
for transferring the driving force of the motor 604 and a throttle
position sensor 606 for detecting the opening of the throttle
valve, and the throttle position sensor 606 and the electric motor
604 are connected to the calculating device 601 through a cable 607
and a cable 608, respectively. The cable 607 sends a signal from
the sensor 606 to the calculating device 601. A signal for driving
the electric motor 604 is sent from the calculating device 601.
Further, a connector 609 is provided to allow the calculating
device 601 to communicate with the outside.
[0075] FIG. 8 shows a state in which the apparatus of the invention
is mounted on an engine. The integrated apparatus 610 is mounted on
a suction pipe of an engine 802 and is connected to a controller
801 which controls the vehicle as a whole including the engine by a
signal line. Position information 801a of an acceleration pedal
which is stepped on by a driver and other information 801b on the
vehicle is input to the controller 801 which outputs a signal 801c
for various actuators, a signal 801d to a fuel injection injector
and an ignition signal 801e. In the controller 801, torque (FIG. 1,
block 1) and the amount of fuel injection required for the engine
are calculated (FIG. 1, block 2), and an engine intake air flow
rate command is calculated (FIG. 1, block 3).
[0076] Engine speed information and the engine intake air flow rate
command are sent from the controller 801 through the connector 609
of the integrated apparatus 610 by a bus 701. The calculating
device 601 of the integrated apparatus performs delay compensation
(FIG. 1, block 4), throttle valve control (FIG. 1, block 5) and the
calculation of the current engine intake air flow rate (FIG. 1,
block 6) such that the actual engine intake air flow rate follows
up the engine intake air flow rate command.
[0077] By separating the calculating device 601 and the controller
801 in such a manner, it is possible to reduce the calculation load
on the controller 801 that controls the engine as a whole. Further,
even when there is a modification of the engine accompanied by
modifications of the electronically controlled throttle and air
flow rate meter, since only the engine intake air flow rate is
specified, the controller 801 can be shared between different
engines to provide the effect of cost reduction. Further, since the
integrated apparatus 610 only causes the throttle valve based on a
command on the engine intake air flow rate, it can be also shared
because modifications on the intake system and engine only result
in a need for changes in internal coefficients. In the case of
separate bodies, each of experimental constants and maps must be
changed each time in consideration to the characteristics of the
air flow rate meter and electronically controlled throttle, which
has resulted in a high cost.
[0078] As another embodiment (second embodiment), a description
will now be made on a method of control in which desirable amounts
of air and exhaust gas are introduced into an engine having an
exhaust gas recirculation valve (EGR valve) to perform exhaust gas
recirculation (EGR: Exhaust Gas Recirculation). FIG. 9 shows the
method of control. Exhaust gas is introduced from an exhaust pipe
15 through an EGR pipe 16 and an EGR valve 17 into a suction pipe.
The amount of the introduced exhaust gas is controlled by the EGR
valve 17.
[0079] A block 1 calculates toque required for the engine by an
operation of a driver on an acceleration pedal or the like. A block
2 determines the amount of fuel injection. A block 3 calculates the
engine intake air flow rate and a block 36 calculates an engine
intake EGR flow rate to output an engine intake air flow rate
command and an engine intake EGR flow rate command, respectively. A
block 4 calculates the engine speed of the engine 11 obtained by a
crank angle sensor 12 and determines a time constant for delay of
the engine intake air flow rate relative to the flow rate of air
passing through the throttle valve based on the engine speed. Once
the time constant of delay is determined, it is possible to
compensate for a delay using an inverse function of a transfer
function representing a change in the intake air flow rate of the
engine from a change in the throttle valve opening. That is, a flow
rate of air passing through the throttle valve required to reach
the engine intake air flow rate command is calculated.
[0080] A block 5 calculates a throttle valve opening to achieve the
flow rate of air passing through the throttle valve calculated in
the block 4 using a signal output by an air flow meter 7, a
throttle valve opening signal 10 and the opening of the EGR valve
obtained in the block 5. Further, the opening of the electronically
controlled throttle is controlled such that the calculated throttle
valve opening is achieved.
[0081] A block 6 succeeds the information input to the block 5 and
calculates the actual flow rate of the air taken into the engine
and sends it to a block 2. The block 2 corrects the amount of fuel
injection with the information in the block 5.
[0082] A block 37 determines a time constant of delay of the engine
intake EGR flow rate relative to the flow rate of exhaust gas
passing through the EGR valve based on the time constant of delay
in the block 4. Once the time constant of delay is determined, it
is possible to compensate for a delay using an inverse transfer
function of a transfer function representing a change in the intake
EGR flow rate of the engine from a change in the EGR valve opening.
That is, an EGR flow rate passing through the EGR valve required to
reach the engine intake EGR flow rate command is calculated.
[0083] A block 39 adjusts the opening of the EGR valve such that
the EGR flow rate passing through the EGR valve is achieved.
[0084] A description will now be made using FIG. 10 and FIG. 11 on
a delay of an engine intake air flow rate flowing into the
cylinders of an engine in relation to the first embodiment and
second embodiment. A case is shown here in which the engine speed
is constant. In FIG. 10, FIG. 10(a) shows the opening of a throttle
valve provided upstream of the intake side of the engine. The
opening of the throttle valve is stepwise operated at a point in
time t0. FIG. 10(b) shows a flow rate detected by an air flow rate
meter provided upstream of the throttle valve at the same point in
time. It is observed from a comparison between FIGS. 10(a), (b)
that a delay occurs in (b) in which slight over-shoot is also seen.
FIG. 10(c) shows the engine intake air flow rate taken into the
cylinders of the engine. The solid line indicates an actual engine
intake air flow rate, and the broken line indicates a flow rate in
accordance with the opening of the throttle valve as a
reference.
[0085] In FIG. 10(c), the engine intake air flow rate slowly
increases. This is attributable to the volume of the intake pipe
between the throttle valve and the engine. Since it takes time for
the volume to be filled, an abrupt change in the throttle valve
causes no abrupt change in the engine intake air flow rate. That
is, the greater the capacity, the greater the delay. Further, the
engine intake air flow rate is also delayed from the output of the
air flow rate meter in FIG. 10(b). The engine intake air flow rate
is delayed from the operation of the throttle valve.
[0086] Under such circumstances, according to conventional
techniques, the delay of the engine intake air flow rate in
response to an abrupt change in the throttle valve opening has been
calculated to adjust the amount of fuel injection. The present
invention provides an apparatus and method for correcting the delay
of the engine intake air flow rate itself.
[0087] The operation will be described with reference to a case as
an example in which the torque of an engine is increased stepwise
as a result of abrupt stepping of the driver on the acceleration
pedal or because of the running state of the vehicle. The required
torque for the engine is first determined, and an amount of fuel
injection is determined based on the same. After a target engine
intake air flow rate to maintain an optimum air fuel ratio is
determined, a calculation is then carried out to obtain a time
constant for the delay of the engine intake air flow rate relative
to the movement of the throttle valve from the engine speed. The
throttle valve operates to compensate for the delay based on the
calculated delay time constant. In other words, a target flow rate
of air passing through the throttle valve is obtained from the
engine intake air flow rate using a transfer function (transfer
function to compensate for a delay) having characteristics that are
the inverse of those of a transfer function whose input is the flow
rate of air passing through the throttle valve and whose output is
the engine intake air flow rate (transfer function to give a
delay). The throttle valve is operated using an electronically
controlled throttle such that a command and an actual flow rate
agree with each other by using the target flow rate of air passing
through the throttle valve as the command value and by comparing it
with the actual throttle valve flow rate calculated based on an air
flow rate detected by the air flow meter. Further, the engine
intake air flow rate is estimated using the flow rate of air
passing through the throttle valve and the time constant of delay,
and the result is returned to a calculating portion for determining
the amount of fuel injection to correct the amount of fuel
injection if necessary.
[0088] The operation of the throttle valve will now be described
using FIG. 11. The broken line in FIG. 11(c) is the target engine
intake air flow rate. It is varied stepwise at a point in time t0.
The calculating device obtains the time constant of delay from the
engine speed and causes the throttle valve taking the factor of the
time constant of delay into account such that the engine intake air
flow rate varies stepwise. As shown in FIG. 11(a), the throttle
valve operates with an over-shoot from the ultimate opening. The
over-shooting amount and over-shooting time are determined by the
time constant of delay. Such an operation of the throttle valve can
cause stepwise changes in the engine intake air flow rate that
follow up the target as indicated by the solid line in FIG. 11(c).
The actual engine intake air flow rate can be controlled at a high
speed without the step operation by operating the throttle valve 13
in advance based on the time constant of delay if the target engine
intake air flow rate is supplied.
[0089] FIG. 13 shows a state in which an apparatus that implements
the above-described control method is mounted on an engine. An
integrated apparatus 810 is mounted on a suction pipe of an engine
11.
[0090] An integrated apparatus 610 is connected by a controller 801
that outputs a fuel injection signal 801d and an ignition signal
801e. The integrated apparatus 610 receives the engine speed, an
engine intake air flow rate command 103 and an engine intake EGR
flow rate command through a bus 810. The integrated apparatus 610
is connected not only to a throttle valve integral therewith but
also to an EGR valve 17 which is a separate body to control the
opening of the EGR valve.
[0091] FIG. 12 shows a case wherein the engine intake air flow rate
and EGR flow rate were adjusted in the above-described
configuration. As indicated by the broken line in FIG. 12c, an
example is shown in which an engine intake air flow rate was given
as a target value at a point in time t0 and in which an engine
intake EGR flow rate was then given stepwise at a point in time t1
such that the total flow rate flowing into the engine (EGR flow
rate+air flow rate) would not change. As indicated by the solid
line in FIG. 12(c), the engine intake air flow rate and EGR flow
rate changed in accordance with the target values. At this time,
the throttle valve opening changes as shown in FIG. 12(a). It
temporarily opens wide between the points in time t0 and t1 to
correct a delay of response attributable to the manifold. It
temporarily operates toward closing side at the point in time t1 to
reduce the engine intake air flow rate abruptly. Thereafter, the
throttle valve is positioned toward the opening side compared to a
case wherein no EGR is provided because of an increase in the
pressure inside the manifold as a result of the introduction of an
EGR. On the other hand, the flow rate detected by the air flow
meter exhibits substantially the same flow rate pattern whether
there is an EGR or not. This is because the present method of
control causes the throttle valve to operate based on the flow rate
of air taken into the engine as a reference instead of simply
driving the signal of the air flow rate meter to a target value.
FIG. 12(d) shows the opening of the EGR valve. At the point in time
t1 and afterward, the EGR valve starts an opening operation and
operates to cause a temporary large opening to compensate for a
delay in the filling of the manifold. This is because the present
method of control causes the EGR valve to operate based on the EGR
flow rate taken into the engine as a reference.
[0092] While the above embodiments have been described primarily
with reference to DI engines, they may be applied to cases wherein
a conventional MPI engine is used on a fuel-first basis or to
dilute mixture combustion engines (lean burn engines) and the
like.
[0093] Further, since the engine intake air flow rate is always
calculated, it may be easily used for detecting failures of an air
flow meter and an air fuel ratio sensor by comparing it with the
detection values of the air fuel ratio sensor measuring an air fuel
ratio from components in exhaust gas and the air flow meter.
* * * * *