U.S. patent number 3,923,016 [Application Number 05/468,527] was granted by the patent office on 1975-12-02 for electronic fuel injection apparatus for a fuel injection.
This patent grant is currently assigned to Hitachi, Ltd.. Invention is credited to Yoshikazu Hoshi.
United States Patent |
3,923,016 |
Hoshi |
December 2, 1975 |
Electronic fuel injection apparatus for a fuel injection
Abstract
In a closed-loop fuel injection apparatus for an internal
combustion engine which comprises an air detector for measuring air
flow into the engine, an oxygen detector for measuring the oxygen
quantity in the exhaust gas from the engine, and a fuel control
means for determining the fuel amount in accordance with the
outputs of the air detector and the oxygen detector. The output of
the oxygen detector is integrated by a capacitor and the amount of
injection fuel is determined by the product of the charging
quantity of the capacitor and the output of the air detector.
Inventors: |
Hoshi; Yoshikazu (Hitachi,
JA) |
Assignee: |
Hitachi, Ltd.
(JA)
|
Family
ID: |
12866984 |
Appl.
No.: |
05/468,527 |
Filed: |
May 9, 1974 |
Foreign Application Priority Data
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|
|
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May 9, 1973 [JA] |
|
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48-50731 |
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Current U.S.
Class: |
123/694;
123/445 |
Current CPC
Class: |
F02D
41/182 (20130101); F02D 41/1482 (20130101); F02D
41/32 (20130101) |
Current International
Class: |
F02D
41/14 (20060101); F02D 41/32 (20060101); F02D
41/18 (20060101); F02D 005/02 () |
Field of
Search: |
;123/32EA |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Myhre; Charles J.
Assistant Examiner: Cangelosi; Joseph A.
Attorney, Agent or Firm: Craig & Antonelli
Claims
What I claim is:
1. An electronic control apparatus for a fuel injection system
comprising:
first means for generating a first signal representative of the
flow of air supplied to an engine cylinder;
second means for generating pulses in response to the engine
rotation;
third means for generating a second signal representative of the
level of the quantity of oxygen in the engine exhaust gas;
fourth means, responsive to said second signal, for generating a
third signal representative of the integration of said second
signal;
fifth means, coupled to said first means and said fourth means, for
generating a charging current in response to said first and third
signals;
sixth means, coupled to said second means and said fifth means, for
discharging said charging current in response to said pulses
generated by said second means;
seventh means, coupled to said sixth means, for generating a fuel
injection valve opening signal in accordance with the time required
for said charging current to discharge by said sixth means; and
eighth means, responsive to the pulses generated by said second
means, for generating a pulse having a predetermined duration, for
controlling the operation of said fourth means.
2. An electronic control apparatus according to claim 1, wherein
said fourth means includes
a comparing circuit which compares said second signal with a
predetermined value and generates one of a positive and negative
valued signal in dependence upon said second signal exceeding said
predetermined value, and
a charge-discharge circuit which integrates the output of said
comparing circuit in response to said predetermined duration pulse
generated by said eighth means.
3. An electronic control apparatus according to claim 2, wherein
said eighth means comprises a monostable multivibrator.
4. An electronic control apparatus according to claim 2, wherein
said fifth means includes a voltage divider network having at least
two variable resistance means and an output terminal connected in
series across a constant voltage source, the resistance value of
one of said variable resistance means being varied in accordance
with the voltage integrated by the charge-discharge circuit of said
fourth means, and the resistance value of the other of said
variable resistance means being varied in accordance with the value
of said first signal representative of air flow, the charging
current generated by said fifth means varying in response to the
voltage at said output terminal.
5. An electronic control apparatus for a fuel injection system
comprising:
first means for generating a first signal representative of the
flow of air supplied to an engine cylinder;
second means for generating pulses in response to engine
rotation;
third means for generating a second signal representative of the
quantity of oxygen in the engine enhaust gas;
fourth means for storing or discharging a charge in response to the
output of said third means;
fifth means for storing a charge in response to the output of said
first means;
sixth means for discharging the charge stored by said fifth means
through a resistance means, the value of which is dependent upon
the output of said fourth means;
seventh means for activating fuel injection valves in response to
the output of said sixth means; and
eighth means comprising a monostable multivibrator for operating
said fourth means in response to the pulses generated by said
second means.
6. An electronic control apparatus for a fuel injection system
comprising:
first means for generating a first signal representative of the
flow of air supplied to an engine;
second means for generating pulses in response to the engine
rotation;
third means for generating a second signal representative of the
level of the quantity of oxygen in the engine exhaust gas;
fourth means, responsive to said second signal, and coupled to said
second means, for generating a third signal representative of the
integration of said second signal;
fifth means, coupled to said first means, said second means and
said fourth means, for generating a fourth signal, a first
component of which is representative of the storing of a charge
over a first prescribed portion of said engine rotation, and a
second component of which is representative of the discharging of
said charge during a second prescribed portion of said engine
rotation subsequent to said first prescribed portion, in response
to said first and third signals; and
sixth means, coupled to said fifth means and said second means, for
generating a fuel injection valve opening signal in accordance with
the duration of the second component of said fourth signal.
7. An electronic control apparatus for a fuel injection system
according to claim 6, wherein said second signal generated by said
third means has a first component of a first polarity
representative of the density of oxygen in said engine exhaust gas
exceeding a prescribed level, and a second component of a second
polarity, opposite to said first polarity, representative of the
density of oxygen in said engine exhaust gas failing to exceed said
predetermined level.
8. An electronic control apparatus for a fuel injection system
according to claim 6, wherein the amplitude of the first component
of said fourth signal at the termination of said first prescribed
portion of said engine rotation is representative of the level of
the density of oxygen in said exhaust gas, while the duration of
said second component of said fourth signal is representative of
the length of time required for the value of charge corresponding
to said amplitude to discharge during said second prescribed
portion of said engine rotation at a predetermined rate of
discharge.
9. An electronic control apparatus for a fuel injection system
according to claim 7, wherein the amplitude of the first component
of said fourth signal at the termination of said prescribed portion
of said engine rotation is representative of the level of the
density of oxygen in said exhaust gas, while the duration of said
second component of said fourth signal is representative of the
length of time required for the value of charge corresponding to
said amplitude to discharge during said second prescribed portion
of said engine rotation at a predetermined rate of discharge.
10. An electronic control apparatus for a fuel injection system
according to claim 6, further including a monostable multivibrator,
coupled to the output of said second means, for controlling the
operation of said fourth means.
Description
Background of the Invention
This invention relates to a control apparatus for a fuel injection
system and, more particularly, to a closed-loop type fuel injection
control apparatus in which the quantity of injected fuel is
compensated in accordance with quantity of oxygen in the exhaust
gas.
Description of the Prior Art
There is a definite relation between the amount of fuel consumed
and the amount of air, since carbon and hydrogen, being elements of
fuel, combine with oxygen in accordance with a prescribed
relationship. In general, air is introduced into a cylinder by
engine suction and the amount of fuel needed is determined in
response to the amount of the introduced air or oxygen. However, it
is very difficult to measure the amount of air with high accuracy.
Therefore, the introduced air-fuel ratio can be determined by
detecting the characteristics of the exhaust gas and it is possible
to compensate the fuel quantity so as to obtain a suitable air-fuel
ratio. Still, a conventional injection control apparatus tends to
be very complicated.
SUMMARY OF THE INVENTION
Objects of the Invention
It is an object of the invention to provide a simple fuel control
apparatus of the closed-loop type.
It is a further object of the invention to provide a fuel control
apparatus of which the operation is very stable.
It is still another object of the invention to provide a fuel
control apparatus having a high response.
A fuel control apparatus of the present invention includes an
integrating circuit for integrating current in response to the
output from an oxygen detector. The output of the integrating
circuit compensates for the amount of injected fuel. If the
integrating circuit has a large time constant, the operation of the
apparatus is very stable, but the response is inferior; for a small
time constant, the response is good, but the operation itself is
unstable. The integrating operation of the integrating circuit is
controlled so as to operate during a predetermined duration
independent of engine speed. The time constant of the integrating
circuit is small, yet the operation of the injection control
apparatus is very stable.
Brief Description of the Drawings
FIG. 1 is a block diagram of an embodiment of the present
invention;
FIG. 2 is an explanatory drawing illustrating the operation state
of FIG. 1;
FIG. 3 is a wave form of a charged voltage produced by the charging
and discharging circuit of FIG. 1;
FIG. 4 is a modification of a pulse generator 5 and a flip-flop 29
of FIG. 1;
FIG. 5 is an explanatory drawing illustrating the operation state
in accordance with the modification of FIG. 4; and
FIG. 6 is a detailed circuit of the block diagram of FIG. 1.
Detailed Description
With reference to FIG. 1, an air flow detector 1 serves to detect
the average value of air flow from the air filter to an engine
cylinder. One of the most frequently used air flow detectors
comprises a movable air plate inserted into an air passage and a
variable resistor a slidable contact of which is moved by the
displacement of the air plate. Therefore, the resistance of the
variable resistor represents the average of the air flow and is
changed in response to the change of air flow.
A temperature sensor 3 detects the temperature of the engine, and
since the amount of fuel to be injected is affected by the
temperature of the engine, the sensor 3 is needed to compensate the
injected amount of fuel.
A pulse generator 5 generates timing pulses in response to the
rotation of the crankshaft. The timing pulse is applied to a
flip-flop 29 for generating a duration pulse proportional to the
engine operation.
An oxygen sensor 7 detects a characteristic of the exhaust gas,
especially the density of oxygen in the exhaust gas. In general, an
oxygen sensor consists of a zirconium dioxide and electrodes
provided on its surface. When the oxygen density on one side of the
zirconium dioxide is different from the density on the other side,
a voltage is generated between the two sides in response to the
difference of the oxygen density. When the one side is inserted
into the exhaust gas and the oxygen density on the other side is
kept constant, the change of the generated voltage corresponds to
the variation of the oxygen density in the exhaust gas.
The temperature sensor 9 is provided to detect the temperature of
the oxygen sensor 7. Since the output of the oxygen sensor 7 is
also affected by temperature, it is needed to compensate the output
voltage. The comparing circuit 11 receives the outputs of the
oxygen sensor 7 and the temperature sensor 9. When the oxygen
density in the exhaust gas exceeds a predetermined value, a
positive current is applied to an integrating circuit 19 through an
AND gate 15. When the oxygen density is below a predetermined
value, a negative current is applied to the integrating circuit 19
through an inverter 13 and an AND gate 17. When positive current is
applied, the output voltage of the integrating circuit 19 is
increased, and it is decreased by applying a negative current.
The operation of the gates 15 and 17 are controlled by a monostable
multivibrator 21. Since the effect of the oxygen sensor is
restricted by the monostable multivibrator 21, the integrating
circuit 19 has large time constant.
A current controller 23 serves to control the charging current of a
charging circuit 25 in such a way that the differential of the
charging current is determined by total differential of the outputs
of the air flow detector, the temperature sensor and the
integrating circuit. The output of the charging circuit 25 is
discharged by a discharging circuit 27, in order to change the
charged voltage to a function of time which represents the valve
opening duration of the fuel injection valve. It is necessary to
identify generating timing of the output of the discharging circuit
27 with fuel injection timing. Therefore, the operations of the
charging and discharging circuits are controlled by the flip-flop
29. A flip-flop 31 serves to distribute the output of the
discharging circuit 27 to valve controllers 41 and 43 through AND
gates 35 and 37. Fuel valves 45 and 47 are driven by the valve
controllers 41 and 43, respectively.
With reference now to FIG. 2, the operation of the circuit depicted
in FIG. 1 will be explained. For purposes of simplification, it
will assumed that the output of the temperature sensor 3 is
negligible.
The output of the air flow detector 1 corresponds to an average of
the air flow in an air passage (not shown) as explained previously.
Since the quantity of air introduced into one of the cylinders of
the engine is determined by the opening time of an air-intake valve
and the air flow quantity therethrough, it is possible to represent
the quantity of air in the cylinder by the electrical output of the
air flow detector 1 during the valve opening. Since the flip-flop
29 is operated by the output of the pulse generator 5, which is
connected to the toggle input of the flip-flop, the duration of the
pulse from the flip-flop 29 will be proportional to the valve
opening.
As is shown in FIG. 2, in each 180.degree. rotation of the
crankshaft, a pulse will be produced by the pulse generator 5, the
duration of the pulse being a portion of the 180.degree. rotation.
This is shown at curve (A) in FIG. 2.
The "set" output of flip-flop 29 is shown at (B) in FIG. 2, this
output appearing on line 61 shown in FIG. 1. Of course, the "reset"
output will appear on line 62 at periods alternating between the
"set" output of flip-flop 29.
Now, since the "set" output of the flip-flop 29 is connected to the
charging circuit 25, during the generation of the output on line
61, i.e., signal (B) of FIG. 2, the charging circuit 25 will store
a charge in accordance with the output of the air flow detector 21,
which is connected to the charging circuit by way of current
controller 23. This charged voltage represents the quantity of air
introduced into a cylinder.
Since the quantity of fuel injection is controlled by the opening
time of fuel valve 45 or 47, shown in FIG. 1, it is necessary to
produce a signal as a function of time, which becomes the basis of
the opening time of the fuel valve 45 or 47. Then, the charged
voltage is discharged with a predetermined current value by the
discharging circuit 27.
Namely, as is shown at (C) in FIG. 2, the charging circuit 25
produces a ramp output corresponding to the output of the air flow
detector 1 during the time that the "set" output of flip-flop 29 is
high. Then, by the way of the "reset" output of the flip-flop 29,
on line 62, discharging circuit 27 is activated and the charge
previously stored in charging circuit 25 is discharged during a
period of time t, i.e., during the period of time of the negatively
sloped ramp of signal (C) of FIG. 2.
The output of the discharging circuit 27 is coupled by way of AND
gates 35 and 36 to the respective valve controllers 41 and 43 for
the fuel valves 45 and 47, respectively. Connected to the other
respective inputs of the AND gates are the "set" and "reset"
outputs of the flip-flop 31, which is connected by way of lines 61
and 62 to the "set" and "reset" outputs of flip-flop 29.
As a result, during alternate periods of time that the discharging
circuit supplies the negatively-sloped ramp output, the fuel
injection valves 45 and 47 will be correspondingly alternately
opened, as shown at (D) and (E) of FIG. 2.
The current to be charged is also effected by the output of the
integrating circuit 19 which represents a characteristic of the
exhaust gas. As a result, the charging current is represented as a
function of the air flow in the air passage and the amount of
oxygen in the exhaust gas. The discharging time will be affected by
the output of the integrating circuit 19 and the quantity of
injected fuel is compensated by the density of oxygen in the
exhaust gas.
With reference to FIG. 3, which depicts the respective positive-
and negative-sloped wave form (C) of FIG. 2, the tangent of the
angle .alpha. is determined as a function of the outputs of the air
flow detector 1, the temperature sensor 3 and the integrating
circuit 19, all of which are supplied to the current controller 23.
The duration of the negatively-sloped ramp, i.e., time t, is
proportional to the opening time of the air-intake valve of the
engine. Thus, the tangent .beta. is constant and is determined by
the discharging current. While tan .alpha. is changed by the output
of the integrating circuit, it is possible to change tan .beta. in
response to the characteristics of the exhaust gas, in order to
compensate the quantity of injected fuel.
In some instances, one fuel valve may be employed to simultaneously
supply fuel to two cylinders. In this case, the quantity of
injected fuel must be doubled. This necessity is achieved by
doubling the charging time of the charging circuit 25.
More specifically, referring to FIG. 4, switches 51 and 52 are
provided to operate in synchronism with the rotation of the
crankshaft to produce pulses, the same as the output of the
flip-flop 29. The flip-flop 55 doubles the pulse duration of the
switches 51 and 55 and the output 57 and 58 of the flip-flop 55 are
supplied to lines 61 and 62 of FIG. 1. Since the duration of the
pulses supplied to the charging circuit 25 is doubled, the
operation time of the charging circuit is doubled as shown in FIG.
5.
In FIG. 5, the wave forms (A' ) -- (D' ) correspond to the wave
forms (A) -- (D) in FIG. 2, with the wave forms for each of the
lines of flip-flop 55 shown at (B' ) and (B').
Referring now to FIG. 6, a detailed circuit diagram of portions of
the circuit of FIG. 1 are shown. In the figure, portion 111,
corresponding to block 11 of FIG. 1, compares the output of an
oxygen sensor with a predetermined level. Circuit portion 119 is an
integrating circuit, corresponding to block 19 of FIG. 1, portion
123 is a current controller, corresponding to block 23 of FIG. 1,
portion 121 is a monostable multivibrator, corresponding to block
21 of FIG. 1, portion 129 is a pulse generator, corresponding to
pulse generator 5 of FIG. 1, and portion 127 is a charging and
discharging circuit, corresponding to blocks 25 and 27 of FIG.
1.
A voltage supply potential is connected to terminal 151 and the
output of the oxygen sensor (not shown) is applied to terminal 153
and amplified by field-effect transistor 155, the gate resistance
of which is very large. The output of the transistor 155 is applied
to operational amplifiers 163 and 165. When the output of the
transistor 155 exceeds a predetermined level established by the
variable resistor 159, the output of the operational amplifier 165
will turn transistor 169 "off." On the other hand, when the output
of the field-effect transistor 155 is below the predetermined level
set by resistor 157, the output of the operational amplifier 163
will turn transistor 167 "off."
Since the voltage generated by the oxygen sensor changes in
response to variations in temperature, a temperature sensor 161 is
provided in series with the variable resistors 157 and 159, in
order to stabilize the predetermined levels set by the variable
resistors 157 and 159.
Now, when transistor 169 is "off," the potential at the terminal
151 will be resistively coupled to the base of transistor 177
which, in conjunction with transistor 179, will turn transistor 181
"on," thereby discharging capacitor 175 therethrough.
When the transistor 167 is "off," as a result of the potential
applied to terminal 151 being resistively coupled to the base of
transistor 171, transistor 173, which is resistively connected to
the collector of transistor 171, will be turned "on," thereby
providing a charging path through the transistor 173 to the
capacitor 175 to charge the same. The voltage across transistor 175
is amplified by transistor 183 and supplied to the base of the
transistor 191.
A diode 187, variable resistor 189, transistor 191, resistor 193
and temperature detector 195, for detecting the temperature of the
engine, are connected in series between the voltage source terminal
151 and ground. The arm of the variable resistor 189 is displaced
by the air-plate which receives the air flow. The output line 197
will supply the voltage which changes as a function of the air
flow, the voltage across capacitor 175 and the temperature of the
engine, to the base of transistor 227, the operation of which will
be discussed hereinafter.
During the rotation of the crankshaft of the engine, switch
terminal contacts 201 and 202 will alternately open and close. When
the switch 201 is open, transistor 205 will be "on," and transistor
185 will be "on." When transistor 185 is turned "on", the voltage
at the collector thereof will become "high", thereby forcing the
voltage on line 197 to a "high" level, so that the operation of the
charging circuit within circuit portion 127 is interrupted.
In the monostable multivibrator 121, transistors 211 and 212 are
operated in response to the voltage on the collector of transistor
207 within pulse generator circuit 129. Transistors 215 and 216
provide the output of the transistors 167 and 169 to the
integrating circuit when the trigger from the switch 201 is applied
to the base of the transistor 212.
Within the charging and discharging circuit 127, transistors 221
and 223 operate as a monostable multi-vibrator. Transistor 227 and
capacitor 225 operate as the charging circuit portion, while
transistor 229 and capacitor 225 operate as discharging circuit.
The charging current of the capacitor 225 is determined by the
voltage supplied to the base of the transistor 227 by way of line
197, as discussed above. The discharging current is determined by
the voltage applied to the base of the transistor 229, which is
determined in accordance with the voltage across variable resistor
231, a slidable arm of which is supplied to the base of transistor
229.
A duration pulse corresponding to the charging time of the
capacitor 225 is produced at the collector of the transistor 223
and supplied by way of output terminal 235 to a valve controller
for controlling the operation of a fuel injection valve.
In the above circuit, the voltage of the capacitor 175 in the
integrating circuit 119, which represents the oxygen density in the
exhaust gas, compensates the charging current delivered to the
capacitor 225 within a charging and discharging circuit portion
127. However, it is possible to compensate the discharging current.
In this case, the diode 187, the variable resistor 189, the
resistor 193 and the temperature sensor 195 are connected in series
between the voltage source terminal 151 and ground. The drain
electrode of the field-effect transistor 183 is then connected to
the base of transistor 229. The charging current is determined by
the air flow average and temperature of the engine, and the
discharging current is determined by the voltage across capacitor
175.
While I have shown several embodiments in accordance with the
present invention, it is understood that the same is not limited
thereto but also contemplates numerous changes and modifications as
would be known to those skilled in the art given the present
disclosure of the invention, and I therefore do not wish to be
limited thereto but intend to cover all such changes and
modifications.
* * * * *