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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an internal combustion engine controlling
apparatus for improving the accuracy and the reliability of controlling an
internal combustion engine of a type that exhaust gas is circulated.
2. Discussion of Background
Generally, in the internal combustion engine of automobiles, controlling
characteristics vary depending on operational conditions in the engine.
Namely, there is change in controlled quantity such as an air-fuel ratio,
ignition timing and so on when the revolution number N of the engine or a
load L (such as air suction) is used as a parameter. Accordingly, it is
necessary to control the controlled quantity such as ignition timing with
high accuracy depending on operational conditions in the engine in order
to efficiently run the engine. For this, when a micro-computer or a
similar device is used, data on the controlled quantity (such as ignition
lead-angle values) corresponding to the number of revolution N or load
data L are stored in an ROM (read-only memory). As an example of the
above-mentioned, Japanese Unexamined Patent Publication 68931/1973
discloses that the number of revolution N and load data L are memorized in
the ROM as a table of a quadratic coordinate so that ignition timing for
the engine is controlled on the basis of the data obtained by the table
memory depending on the operational conditions of the engine.
In controlling an internal combustion engine provided with an exhaust gas
recirculation device, the operational conditions of the engine change
depending on an amount of exhaust gas to be recirculated. Accordingly, it
is necessary to determine a controlled quantity such as ignition timing by
adding data on the exhaust gas recirculation quantity. In this case, as
data on the exhaust gas recirculation quantity, an amount of lifting the
valve body of a control valve is used to control an amount of
recirculation of the exhaust gas (hereinbelow, referred to as EGR). Or, a
negative pressure of air to be supplied to a driving means is used when a
negative pressure type actuator is used as a driving means for driving the
control valve. Or a signal such as a driving current is used when an
electric type actuator is used.
In order to obtain data on a controlled quantity such as ignition timing,
the data of number of revolution N, a load L and the above-mentioned EGR
are added as parameters, and the data stored in given locations in the
memory are sequentially read in response to the operational conditions of
the engine, whereby the controlled quantity such as the ignition timing is
determined on the basis of the read data.
Generally, although detected values such as the number of revolution N and
the load L (for instance, a negative pressure in an intake air system) do
not substantially change with the lapse of time in the lifetime of engine,
there is found a substantial change in detected values on the data E of
the EGR when the value at the initial stage of use is compared with the
value measured after a long time use because carbon in the exhaust gas
deposits on an EGR control valve and on the wall of the duct when the
engine is used for a long period. Accordingly, it is difficult to
accurately control the engine because the detected values do not
correspond to the actual operational conditions of the engine and because
the initial value of the controlled quantity of the engine moves.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an internal combustion
engine for improving accuracy and reliability in controlling operations of
the engine and for increasing efficiency in fuel consumption and
purification of exhaust gas even though the engine is used for a long
time.
In accordance with the present invention, there is provided an internal
combustion engine controlling apparatus which comprises a returning means
for adjustably returning a part of exhaust gas from an internal combustion
engine to an air intake system to mix it with intake air, a detecting
means for detecting at least one operation parameter indicating
operational conditions in the engine, an oxygen sensor for detecting the
concentration of oxygen in the intake air after recirculating the exhaust
gas to said air intake system, and a control means which includes a memory
means to store data for determining a control parameter for the engine in
response to a plurality of operational conditions in the engine, the
operational conditions being defined by a calculated value obtained by the
operation parameter and the oxygen concentration in said intake air and
which outputs a signal for correcting the operation parameter on the basis
of the data stored in the memory.
Further, in accordance with the present invention, there is provided an
internal combustion engine controlling apparatus which comprises a
recirculating means for adjustably recirculating a part of exhaust gas
from an internal combustion engine to an air intake system to mix it with
intake air, a calculating means for effecting digital calculation of a
controlled quantity for the engine in response to operational conditions
in the engine in accordance with a program, an oxygen sensor for detecting
the concentration of oxygen in the intake air after recirculating the
exhaust gas to the air intake system, and a calculation-correcting means
which calculates a value related to the output of the oxygen sensor and
which determines a controlled quantity for the engine on the basis of data
which are obtained by correcting a value obtained by the calculating means
by using the value related to the output of the oxygen sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the invention and many of the attendant
advantages thereof will be readily obtained as the same becomes better
understood by reference to the following detailed description when
considered in connection with the accompanying drawings, wherein:
FIG. 1 is a block diagram showing an embodiment of the internal combustion
engine controlling apparatus according to the present invention;
FIG. 2 is a block diagram showing the inner structure of an EGR controlling
circuit used for the apparatus as shown in FIG. 1;
FIG. 3 is a diagram showing a relation of an output Ip generated from an
oxygen sensor to a detected concentration of oxygen Co2 to illustrate the
operation of the above-mentioned embodiment;
FIG. 4 is a diagram showing a relation of an EGR rate K to the
concentration of oxygen Co2 of the above-mentioned embodiment;
FIG. 5 is a diagram showing the inner structure of of a computer used for
the above-mentioned embodiment; and
FIG. 6 is a block diagram showing the inner structure of a computer used
for another embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the
drawings, wherein the same reference numerals designate the same or
corresponding parts, and particularly to FIG. 1, there is shown an
embodiment of the internal combustion engine controlling apparatus. A
reference numeral 1 designates the main body of an internal combustion
engine. An air duct 6 is connected to the engine main body 1 through an
intake air manifold 2. An air cleaner 7 is disposed at the free end of the
air duct 6. A throttle valve 5 is disposed in a predetermined position in
the air duct 6.
A fuel supplying device 4 is attached to the connecting portion of the
intake air manifold 2 and the engine main body 1. An exhaust manifold 3 is
connected to the engine main body 1. Ignition plugs 18 are attached to the
engine main body 1.
The exhaust manifold 3 is communicated with the intake air manifold 2
through an EGR passage 11 in which a control valve 12 for controlling an
amount of the exhaust gas (hereinbelow, referred to as an EGR valve) is
provided. In this embodiment, a pressure-operated diaphragm valve, which
is actuated by a negative pressure introduced from the intake manifold is
used as a driving source for the EGR valve 12.
The negative air pressure is introduced from the intake air manifold 2
through a negative pressure introducing conduit 9. An air pressure in the
intake air manifold 2 is detected by a negative pressure detector 10
through the negative pressure introducing conduit 9.
The reciprocating movements of a piston 1a in the engine main body 1 is
converted in a rotary motion by a crank mechanism. The revolution of the
crank mechanism, i.e. the revolution of the engine is detected by an
engine speed detector 8. Further, a crank angle position of the engine is
detected by a crank angle sensor 20.
The output of the engine speed detector 8, i.e. a revolution speed signal N
of the engine is outputted to an EGR controlling circuit 14 and a computer
22. On the other hand, the output of the crank angle sensor 20, i.e. a
crank angle signal CA is outputted to a computer 22.
An oxygen sensor 21 is provided in the intake air manifold 2 to detect the
concentration of oxygen, and an output from the oxygen sensor 21, i.e. an
oxygen concentration signal O2 is supplied to the computer 22.
The sensor element of the oxygen sensor 21 is provided at the downstream
side (at the side of the engine main body 1) of the intake air manifold 2
with respect to the opening part of the EGR passage 11. The oxygen sensor
21 may be a solid-electrolyte oxygen pump type sensor in which a current
output (mA) is produced in proportion to the concentration of oxygen, as
proposed, for instance, in Japanese Unexamined Patent Publication
153155/1983. The output of the negative pressure detector 10 which detects
the pressure of air in the intake air manifold 2, i.e. an intake air
pressure signal PB is supplied to the computer 22 and the EGR control
circuit 14. The EGR control circuit 14 is so adapted to adjust the EGR
valve 12 so that the EGR rate is changed to a predetermined value in
response to the negative air pressure and the engine speed.
The computer 22 is composed mainly of a microcomputer which receives the
input signals, as described above such as the engine speed signal N, the
crank angle signal CA, the oxygen concentration signal O2, the intake air
pressure signal PB detected at the downstream of the throttle valve 5.
The computer 22 produces an electric signal to an ignition plug actuating
device 19, namely, an electric pulse corresponding to a current conduction
time to ignition coils.
The ignition plug actuating device 19 for generating electric sparks to the
ignition plugs 18 is constituted by pe g .00the known ignition coils and
power transistors for switching on/off energizing the ignition coil.
The ignition coil 18 generates ignition sparks to a gas mixture in a
cylinder in the engine main body 1.
The construction of the EGR control circuit will be described in detail
with reference to FIG. 2. The intake air pressure signal PB is inputted
from the negative pressure detector 10 to an A/D(analog/digital)
transducer 101. The engine speed signal N is inputted from the engine
speed detector 8 to an f/D(frequency/digital) transducer 102.
The outputs of the A/D transducer 101 and the f/D transducer 102 are
respectively supplied to a digital operation circuit 103 in which the
outputs are transformed into digital values, which are outputted to a
memory circuit 104 as reading instruction signals [PB], [N].
The output of the memory circuit 104 is supplied to the pulse operation
circuit 105, and the output of the pulse operation circuit 105 is
outputted to the EGR control valve 12.
FIG. 5 shows the inner structure of the computer 22. In FIG. 5, the A/D
transducer 201 is adapted to receive the intake air pressure signal PB,
and the f/D transducer 202 is adapted to receive the engine speed signal N
from the engine speed detector 8.
The A/D transducer 201 and the f/D transducer 202 are respectively so
adapted to receive input signals to convert them in digital signals, which
are supplied to a digital operation circuit 203, whereby the reading
instruction signals [PB], [N] are respectively outputted to a memory
circuit.
On the other hand, a data converting circuit 210, which may be formed of a
digital circuit or an analog circuit, is so adapted to receive an output
IP from the oxygen sensor 21 to calculate an EGR rate K to thereby supply
it to a digital operation circuit 213.
The digital operation circuit 213 receives the EGR rate K to output a
reading instruction signal [E] to the memory circuit 204.
Explanation of the data stored in the memory circuit 204 will be made
hereinafter with reference to the operation of it. The output of the
memory circuit 204 is supplied to a pulse operation circuit 205 which is,
in turn, so adapted that it receives the output CA of the crank angle
sensor 20 to thereby output a pulse signal as a reference angle signal 5
which determines a current conduction time for an ignition coil to the
ignition coil actuating device 19.
The operation of the internal combustion engine controlling apparatus of
the present invention will be described.
First of all, explanation on controlling the EGR rate is made with
reference to FIG. 2. The intake air pressure signal PB outputted from the
negative pressure detector 10 is inputted into the A/D transducer 101 to
be transformed in a digital quantity in accordance with a predetermined
treatment.
The engine speed signal N from the engine speed detector 8 is inputted into
the f/D transducer 102 to be transformed into a digital signal.
The digital operation circuit 103 receives the outputs of the A/D
transducer 101 and the f/D transducer 102 to perform digitally filtering
treatment of the digital data to thereby output the reading instruction
signals [N] and [PB] to the memory circuit 104.
The memory circuit 104 stores data by which a signal to be outputted to the
EGR control valve 12 in engine conditions which are defined in the two
dimensional space of the engine speed N and the intake air pressure PB, is
determined. Namely, the data correspond to a time ratio in opening and
closing the EGR control valve 12, when the EGR control valve 12 is of a
type operable by a negative pressure diaphragm, and a negative pressure
applied to the diaphragm is controlled by the time ratio in opening and
closing a solenoid valve.
When the reading instruction signals [PB], [N]corresponding to the engine
speed signal N and the intake air pressure signal PB are inputted into the
memory circuit 104, the above-mentioned data is read to be supplied to the
pulse operation circuit 105. The pulse operation circuit 105 generates a
pulse signal having a time ratio corresponding to the data stored in the
memory circuit, and the pulse signal is inputted in the EGR control valve
12, whereby control of the EGR rate is conducted in response to the
operational conditions of the engine.
The operation of the major components constituting the internal combustion
engine controlling apparatus according to this invention will be described
with reference to FIGS. 3-5.
FIG. 3 is a characteristic diagram showing a relation of the concentration
of oxygen Co2 to the output Ip of the oxygen sensor 21. The output IP of
the oxygen sensor 21 is inputted in the computer 22 in which the
concentration of oxygen is calculated.
FIG. 4 is a characteristic diagram showing a relation of the concentration
of oxygen Co2 to the EGR rate (a raio of an amount of EGR to an amount of
air to be supplied to the engine). Calculation of the concentration of
oxygen Co2 is carried out in accordance with the characteristic diagram of
FIG. 3, and then, the EGR rate K is calculated in the computer 22 in
accordance with the characteristic diagram of FIG. 4.
In FIG. 5, processing of the intake air pressure signal PB and the engine
speed signal N is conducted in the computer 22 in the same manner as
described with reference to, the EGR control circuit 14. In FIG. 5, the
data converting circuit 210 calculates the EGR rate K from the output Ip
of the oxygen sensor 21, and the value obtained by the calculation is
supplied to the digital operation circuit 213.
On receiving the signal of EGR rate K, the digital operation circuit 213
outputs the reading instruction signal [E] to the memory circuit 204.
The memory circuit 204 stores data by which determination is made as to
ignition timing in the engine conditions quadratically defines by the EGR
rate K in addition to the engine speed N and the intake air pressure PB.
When the reading instruction signals [PB], [N], [E] concerning the engine
revolution speed N, the intake air pressure signal PB and the EGR rate K
are inputted in the memory circuit 204, data stored in the memory circuit
204 at the positions corresponding to these reading instruction signals
are read out so that they are supplied to the pulse operation circuit 205.
The pulse operation circuit 205 generates a pulse signal to the ignition
coil actuating device 19 by using an output signal CA from the crank angle
sensor 20 as a reference angle signal so that ignition sparks are produced
in the ignition plugs 18 at a predetermined ignition timing.
As described above, in accordance with the present invention, accurate
control of parameters for controlling the internal combustion engine
equipped with EGR is obtainable without causing substantial change in the
control characteristic even though the engine is used for a long time.
Further, purification of exhaust gas and saving fuel are also attainable.
The second embodiment of the internal combustion engine controlling
apparatus according to the present invention will be described.
The construction of the second embodiment is the same as the first
embodiment shown in FIGS. 1-5 except for the inner construction of a
computer as shown in FIG. 6. Namely, description concerning the
construction as shown in FIG. 1, the circuit the EGR control circuit as
shown in FIG. 2 and the calculation of the EGR rate K with reference to
FIGS. 3 and 4 can apply the second embodiment, and therefore, description
of these portions will be omitted.
The unique construction of the second embodiment will be explained with
reference to FIG. 6.
In FIG. 6, the processing operations for the intake air pressure signal PB
and the engine revolution speed signal N as parameters indicating the
operational conditions of the engine, and the memory circuit for storing
the values obtained by the processing operations are the same as those
described with reference to FIG. 5.
The output IP of the oxygen sensor 21 is inputted to the data converting
circuit 210. The operation converting circuit 210 calculates the EGR rate
K from the output IP, and thus obtained EGR rate K is supplied to a
corrected lead-angle calculation circuit 211 which may be formed of a
digital circuit or an analog circuit.
The corrected lead-angle calculation circuit 211 calculates a corrected
lead-angle data SA1 on the basis of EGR rate K, and thus obtained data are
outputted to the pulse operation circuit 205.
The pulse operation circuit 205 receives the output data SA of the memory
circuit 204, the output SA1 of the corrected lead-angle calculation
circuit 211 and the output CA of the crank angle sensor 20. The output CA
is supplied to the ignition actuating device 19 as a reference angle
signal.
The operation of the second embodiment of the present invention will be
described.
In FIG. 6, the data converting circuit 210 calculates the EGR rate K on the
basis of the output IP of the oxygen sensor 21 in the same manner as the
description with reference to FIGS. 3 and 4.
The memory circuit 204 stores data which determines ignition timing under,
the operational conditions of the engine defined in the two dimensional
space of the engine revolution speed signal N and the intake air pressure
signal PB in the same manner as the memory circuit 104 in FIG. 2.
On starting the engine, the signal PB of the negative pressure detecting
device 10 and the signal N of the engine revolution speed detecting device
8 are respectively inputted to the A/D transducer 201 and the f/D
transducer 202. The signals are operated in the digital operation circuit
203 whereby the reading instruction signals, are respectively outputted.
The reading instruction signals [PB], [N] are supplied to the memory
circuit 204, a data signal SA (SA: spark angle) for determining ignition
timing is supplied from the memory circuit 204 for a predetermined time.
On the other hand, an output signal IP is supplied to the data converting
circuit 210 in response to change in the concentration of oxygen in the
intake air which changes depending on the actual EGR rate during the data
of the engine. The operation converting circuit 210 performs conversion of
the input signal IP into the concentration of oxygen Co2, and further to
the EGR rate K, and then, a signal indicating the EGR rate K is supplied
to the corrected lead-angle calculation circuit 211 in which a corrected
quantity for the ignition timing is calculated.
The corrected lead-angle calculation circuit 211 operates the EGR rate K in
accordance with a previously stored calculating formula to obtain a
corrected lead-angle data SA1. Alternatively, the corrected lead-angle
calculation circuit may be formed of a digital circuit which is so adapted
that some corrected lead-angle data corresponding to some of the EGR rate
K are previously stored in a memory circuit, and when a signal indicating
an EGR rate K is inputted, a value stored in the memory circuit at the
position corresponding, to the inputted, signal is read to thereby obtain
a corrected lead-angle data SA1.
The pulse operation circuit 205 determines ignition timing on the basis of
the data signal SA from the memory circuit 204 and the data signal SA1
from the corrected lead-angle calculation circuit 211. In accordance with
the ignition timing thus determined, a pulse signal which uses the output
signal CA from the crank angle sensor 20 as a reference angle signal is
outputted to the ignition actuating device 19, so that the ignition plugs
18 produce ignition sparks.
In accordance with the second embodiment of the present invention, a
controlled quantity for the internal combustion engine in which a part of
the exhaust gas in the engine is adjustably returned to the intake air
system is corrected on the basis of a signal from the oxygen sensor
disposed in the intake air system. Accordingly, accurate, control of the
engine equipped with EGR system is obtainable without causing substantial
change in the control characteristic.
In the above-mentioned embodiments, the ignition timing is used as the
parameter for controlling the engine. However, a parameter of an air-fuel
ratio may be used for controlling. In this case, same effect can be
obtained.
Obviously, numerous modifications and variations of the present invention
are possible in the light of the above teachings. It is therefore to be
understood that within the scope of the appended claims, the invention may
be practiced otherwise than as specifically described herein.
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