U.S. patent number 3,893,432 [Application Number 05/213,905] was granted by the patent office on 1975-07-08 for electronic control system.
This patent grant is currently assigned to Fairchild Camera and Instrument Corporation. Invention is credited to Robert B. Hood, David M. Krupp.
United States Patent |
3,893,432 |
Krupp , et al. |
July 8, 1975 |
Electronic control system
Abstract
An electronic system for controlling the duration of operation
of a plurality of repetitively-activated structures produces a
control signal representing the duration of operation of the
structures from a plurality of input signals representing the
values of the parameters which control the duration of operation.
The structures are activated by start pulses. The duration of
operation of each structure is controlled by the time necessary to
drive a corresponding start pulse through a delay line. This time
in turn is controlled by the control signal. A plurality of start
pulses, each of which controls the operation of a different
structure, can be located at different places in the delay line at
the same time. The time necessary for each start pulse to travel
through the delay line can vary continuously in response to
variations in the parameters which control the desired duration of
operation. Various circuits are provided to prevent or ensure
activation of the structures under special circumstances.
Inventors: |
Krupp; David M. (Mountain View,
CA), Hood; Robert B. (Los Altos, CA) |
Assignee: |
Fairchild Camera and Instrument
Corporation (Mountain View, CA)
|
Family
ID: |
22796965 |
Appl.
No.: |
05/213,905 |
Filed: |
December 30, 1971 |
Current U.S.
Class: |
123/486; 700/70;
123/487; 701/123 |
Current CPC
Class: |
F02D
41/1481 (20130101); F02D 41/365 (20130101); F02D
41/24 (20130101); F02P 5/045 (20130101) |
Current International
Class: |
F02D
41/00 (20060101); F02P 5/04 (20060101); F02D
41/32 (20060101); F02D 41/36 (20060101); F02D
41/24 (20060101); F02D 41/14 (20060101); F02b
003/00 () |
Field of
Search: |
;123/32EA,139E,32AE
;235/150.21 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Myhre; Charles J.
Assistant Examiner: Cox; Ronald B.
Attorney, Agent or Firm: MacPherson; Alan H. Richbourg; J.
Ronald
Claims
What is claimed is:
1. An electronic control system for a fuel injection system for use
with an engine producing repetitive signals for synchronizing the
injection of fuel with the fuel requirements of said engine, which
control system comprises:
a. means for sensing the values of a plurality of parameters which
determine the amount of fuel to be injected into utilization means
of said engine, and for producing a plurality of first signals
representing these values;
b. means, responsive to said first signals, for producing a second
signal representing the injection time necessary to inject the
required amount of fuel into said utilization means;
c. means for generating timing signals from the repetitive
signals;
d. delay means for receiving said timing signals, said timing
signals being shifted through said delay means at a rate determined
by said second signal; and,
e. means, responsive to the time necessary for said timing signals
to be shifted through said delay means, for controlling the opening
and closing of fuel injection means disposed for injecting fuel
into said utilization means comprising:
1. means for detecting the presence of said timing signals in said
delay line and for producing a start signal in response to said
timing signals;
first means, responsive to a signal from said means for detecting,
for counting the number of timing signals placed in said delay line
and for controlling an injector decode selector matrix in response
to each timing signal placed in said delay means;
3. an injector decode selector matrix means, responsive to said
first means for counting, for selecting a particular fuel injector
means the opening and closing times of which are to be controlled
by a corresponding timing signal travelling through the delay line;
and,
4. second means for detecting and counting the timing signals
arriving at the end of said delay means and for producing a signal
in response to the arrival of each timing signal to control,
through said injector decode selector matrix means, the closing of
the fuel injector means opened by said timing signal.
2. A system as in claim 1 wherein said utilization means comprises
an engine containing P cylinders, where P is an integer
representing the number of cylinders in the engine.
3. Structure as in claim 1 wherein said means responsive to said
first signals, producing said second signal, comprise
a plurality of amplifier means the gains of which vary according to
the values of said parameters, the output signals from said
amplifier means comprising said plurality of first signals.
4. Structure as in claim 1 including
means for reopening in response to an acceleration signal, at least
one previously closed fuel injector means for the injection of
additional fuel into the cylinder adjacent said previously opened
fuel injector means.
5. Structure as in claim 1 including
means for generating a resynchronization signal to reset said first
means for counting and said second means for detecting and counting
to an initial state in synchronization with the operating
conditions of said engine.
6. Structure as in claim 5 wherein said resynchronization signal is
generated once every engine combustion cycle.
7. Structure as in claim 1 including:
means for producing a cut-off signal in response to a sudden
decrease in demand for fuel, said cut-off signal disabling said
injector decode selector matrix thereby to prevent additional fuel
from being injected into said engine for the duration of said
cut-off signal.
8. Structure as in claim 1 including:
means for detecting traces of undesired gases in the exhaust from
said engine and for controlling the amount of fuel injected into
said engine so as to reduce the amounts of said undesired gases.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electronic control system and in
particular to an electronic control system for use with an
injection system. The electronic control system described in this
specification is particularly suitable for use with fuel injectors
for automobile engines. However, the described system can also be
used to control any repetitively activated equipment where the time
of activation depends on measurable variables.
2. Prior Art
Numerous control systems have been proposed for fuel injectors. In
general, fuel injection control systems respond to selected input
parameters from an engine to determine the amount of fuel to be
injected into each cylinder. Typical prior art systems have several
disadvantages. Among these are the fact that these systems use a
large number of discrete electronic components and thus often are
bulkier than desirable. In addition, these systems usually
determine the amount of fuel required by each cylinder by
approximate techniques of insufficient accuracy to comply with
present and projected stringent air pollution standards. Often fuel
is not injected into each cylinder at the optimum time for
injection, but rather is injected simultaneously into the manifold
sections adjacent groups of cylinders. Other problems associated
with these systems include a lack of reliability and
responsiveness.
SUMMARY OF THE INVENTION
The fuel injection control system of this invention automatically
adjusts the fuel required for each cylinder according to the
manifold and atmospheric pressures, inlet air temperature, cylinder
head temperature, fuel temperature, engine speed, battery voltage,
throttle setting, and other selected inputs. Among these other
inputs are signals indicating a wide open throttle or a fully
closed throttle, and other factors affecting fuel consumption.
According to this invention, an electronic control for a fuel
injection system comprises means for sensing the values of a
plurality of parameters which determine the amount of fuel to be
placed in each cylinder and for producing a plurality of input
signals representing these values, means for operating on these
input signals to determine the injection time necessary to inject
the required amount of fuel into each cylinder, and means
responsive to the injection time for producing control signals for
controlling the opening and closing of a fuel injector associated
with each cylinder.
In one embodiment, the means for converting the values of the input
parameters into input signals representing the amount of fuel
required by each cylinder comprises a plurality of amplifier means
the gains of which are varied according to the values of the input
signals. The output signals from these amplifier means are used to
control the frequency of the output signal from an
oscillator--sometimes called a "computing oscillator". Pulses are
driven through a delay line at a shift frequency determined by the
frequency of the output signal from the oscillator. As the
frequency of the oscillator output signal increases, the shift
frequency of the pulses through the delay line increases and vice
versa. The time necessary for pulses to travel through the delay
line controls the open time of the fuel injectors.
The oscillator frequency can change continuously in response to
changes in the values of input signals. Thus the opening and
closing times of the injector associated with each cylinder
likewise can vary from cycle to cycle. In addition, the time that
each fuel injector remains open can vary from injector to injector
in response to changes in the oscillator frequency.
Means are provided for injecting additional fuel into selected
cylinders in response to sudden increases in demand and to cut off
all fuel to the cylinders in response to selected decreases in
demand.
While the electronic control system of this invention is designed
to operate with an engine wherein each cylinder has an adjacent
fuel injector means which is individually controlled according to
the fuel demands of that cylinder, this control system can also be
adapted to operate with an engine using batch injection.
In one embodiment, the invention uses operational amplifiers to
generate the signals which control the period of the output signal
from the computing oscillator. Usually a transducer is connected in
the input or feedback circuit of an operational amplifier. As the
value of the parameter sensed by the transducer changes, the
impedance introduced into the circuit changes, thereby changing the
gain of the amplifier. By interconnecting selectively-poled diodes
in parallel and series with a resistor, for example, between the
input lead and the output lead of an operational amplifier, the
output signal from the operational amplifier is made piecewise
linear. The input signal voltage at which the operational amplifier
begins to produce a linear output signal can be controlled by
varying the nominal voltage on one of the input leads to the
operational amplifier. By combining a plurality of piecewise linear
output signals from a corresponding plurality of operational
amplifiers, the system can be made to generate control signals
tailored to the actual operating characteristics of a selected
engine. Thus, for example, the fuel injection time duration can be
matched very accurately to the parameters upon which time duration
depends.
Input parameters such as temperatures can be converted into output
signals appropriate for use in this control system by placing
thermistors, temperature dependent resistive elements, or any other
element whose characteristics are appropriately temperature
dependent, in the input or feedback circuit of the operational
amplifier so that temperature changes vary the output voltage from
the operational amplifier.
DESCRIPTION OF THE FIGURES
FIG. 1 shows in schematic block diagram form, the general
arrangement of the functional components of the electronic control
system of this invention;
FIG. 2 shows in more detail the computing oscillator 30 shown in
FIG. 1;
FIG. 3 shows the circuit used to sense selected temperatures which
affect engine performance;
FIG. 4a through 4h show circuits used to detect manifold pressure
and other parameters which affect engine performance and graphs
useful in explaining the operation of these circuits;
FIGS. 5a, 5b and 5c illustrate in more detail the circuitry
comprising digital delay 20 (FIG. 1);
FIG. 6 shows the injection decoding and control circuitry shown in
blocks 60, 70, 80, 90, and 100 of FIG. 1;
FIG. 7 shows special circuitry designed to provide input signals to
the computing oscillator 30 (FIG. 1) reflecting changes in fuel
demand.
FIG. 8 shows the circuitry for producing a signal indicative of
throttle position; and
FIG. 9 shows the fuel pump control, turn on reset and exhaust gas
analysis circuitry.
DETAILED DESCRIPTION
The electronic control system of this invention will be described
in conjunction with a fuel injection system suitable for use with
an eight cylinder automobile engine. With appropriate changes, this
system can be used with engines containing other numbers of
cylinders. It should be recognized that this electronic control
system is appropriate for use with any repetitively-activated
equipment where the time of activation depends upon measurable
variables.
FIG. 1 shows a schematic block diagram of the system of this
invention. A transducer produces a signal every 90.degree. of
rotation of the engine's crank shaft. This signal, transmitted to
that input lead to processor 10 labeled "90.degree. pickup",
activates processor 10 to produce a pulse which is transmitted to
digital delay 20. This pulse is driven through delay 20 at a
frequency determined by the fundamental frequency of a clock signal
from computing oscillator 30.
The period of the pulses from oscillator 30 is determined by input
signals from a variety of sources. The primary inputs used to
control the frequency of the output signal from computing
oscillator 30 are signals representing the absolute manifold
pressure, engine temperature (which can be monitored at a variety
of places including the exhaust manifold, block head, crankcase,
cylinders or any other point which yields a temperature which is
representative of the engine temperature) air inlet temperature,
fuel temperature, speed of the engine and throttle position. In
addition, battery voltage and a measure of the torque being
delivered by the engine can also be used to influence the frequency
of the signal from computing oscillator 30.
The effect of each input parameter on fuel charge varies. Some
parameters have a major effect on the fuel charge, while other
parameters have a very small influence on the fuel charge. Under
normal operating conditions, the fuel charge injected by each
injector is controlled mainly by the manifold pressure and engine
speed. Air, fuel and water temperature also influence the fuel
required, in decreasing importance as listed under normal hot
running conditions only. During warm-up, water temperature is the
most important temperature parameter followed by the air and fuel
temperatures, respectively.
Transient processor 50 computes input signals for use in
controlling oscillator 30 from crankshaft and throttle positions.
Separate signals representing wide open throttle position (WOT),
fully closed throttle position (FCT), engine speed, power to the
crank motor and shut-off information are also processed by
processor 50. The computing oscillator responds to the signals from
processor 50 and to its other input signals and produces an output
signal with a frequency controlled by these and other input
signals.
The functional relationships between the required fuel charge and
the input parameters depend upon the particular engine
configuration. Much work has been done defining these
relationships. See for example a book entitled "Aircraft Powerplant
Handbook" published in January 1949 by the U.S. Department of
Commerce where many of these relationships are discussed.
The output pulses from oscillator 30 drive groups of pulses from
processor 10 through digital delay 20. The times for the pulse
groups to pass through digital delay 20 are inversely proportional
to the frequency of the output signal from oscillator 30.
Two pieces of information are derived by the passage of the pulse
groups through digital delay 20. Data decode 100 detects the
presence of each pulse group at the beginning of digital delay 20.
In response to this, data decode 100 generates a control signal
which is transmitted to "A" counter 90. This signal steps counter
90 one digit. Counter 90 is capable of counting up to N, where N is
an integer representing the maximum number of cylinders in an
engine (assumed to be eight of this explanation). The change in
count in counter 90 results in a signal being transmitted to
injector decode 80. This signal identifies the particular cylinder
into which fuel is to be injected. Injector decode 80 then
transmits a signal to open the correct injector. Fuel is then
injected into either the manifold or directly into a cylinder.
When the pulse group traveling through digital delay 20 reaches the
end of delay 20, a signal is transmitted to data decode 60. Data
decode 60 then generates a pulse which is transmitted to "B"
counter 70. Counter 70 likewise can contain N different numbers.
The change in count in counter 70 results in a signal being
transmitted to injector decode 80. This signal terminates the
injection of fuel.
A plurality of pulse groups are transmitted in sequence through
digital delay 20. Each pulse group activates in sequence, data
decode 100 and data decode 60 to start and stop the injection of
fuel into the appropriate cylinder. In this manner each injector is
controlled in sequence to provide the proper amount of fuel to its
corresponding cylinder.
It should be noted that the time required for pulse groups to
travel through delay 20 varies depending upon the frequency of the
output signal from oscillator 30. Thus, this control system
responds rapidly to changes in operating conditions of the engine
to correct the amount of fuel injected into each cylinder.
COMPUTING OSCILLATOR 30
FIG. 2 shows the circuit comprising oscillator 30 (FIG. 1). The
signals to this circuit include signals (+TEMP and -TEMP)
representing selected temperatures and a signal representing the
manifold pressure. In general, the fuel required by each cylinder
increases as air temperature, water temperature and fuel
temperature decrease and as manifold pressure increases. Thus the
period of the signal produced by oscillator 30 (FIG. 2) must
increase as these temperatures decrease. As the period of
oscillator 30 increases, the time necessary for pulses to travel
through delay 20, and thus the injection time, increases.
Composite signals representing the influence of selected
temperatures are input to oscillator 30 through resistors 301 and
302. A positive signal proportional to temperature (the +TEMP
signal) is transmitted through resistor 301. An inverted signal
(the -TEMP signal) is transmitted through resistor 302. These two
signals are generated in a manner to be described later in
conjunction with FIG. 3. MOS transistors 303, 304, 305 and 306 are
connected together to form a switching circuit. The sources of
transistors 303 and 304 are grounded. The gates of transistors 303
and 306 are connected together while the gates of transistors 304
and 305 are also connected together. The gates of transistors 304
and 305 are connected by lead 318a to the collector of transistor
318. The gates of MOS transistors 303 and 306 are connected by lead
317a to the collector of transistor 317.
The operation of the oscillator circuit will be explained assuming
that initially transistor 318 is shut off and transistor 317 is
conducting. Thus the collector voltage of transistor 318 is the
negative voltage of voltage source 312 while the collector voltage
of transistor 317 is the voltage of source 312 plus the voltage
drop across resistor 322 or about zero volts. Accordingly, a
negative voltage approximately equal to that of voltage source 312
is applied to the gates of transistors 304 and 305 turning them off
while a much higher voltage (about zero volts) sufficient to turn
on transistors 303 and 306 is applied to the gates of these last
two transistors. Accordingly, transistors 303 and 306 provide low
resistance paths for signals to travel from their drains to other
sources. Transistor 306 is connected to one input lead of
operational amplifier 307. The other input lead to amplifier 307 is
grounded through a filter comprising capacitor 307a and resistor
307b. Transistor 303 is connected to shunt to ground the unused
+TEMP signal source.
When transistor 318 is off, transistor 306 is on and the input
voltage generated by the -TEMP input transducer is applied to
integrating amplifier 307. The input current to amplifier 307 is
integrated by capacitor 307f. Resistors 307i, 307j and 307h provide
an additional means for controlling the time necessary for the
voltage across capacitor 307f to reach a desired value. Zener
diodes 307k and 307n limit the output voltage of amplifier 307 to
within the input voltage limits of comparators 308 and 309. In
normal operation diodes 307k and 307n are not needed.
Thus, initially the output voltage from amplifier 307 has a
linearly increasing positive shape. This output signal is passed to
the positive and negative input leads to comparators 308 and 309
respectively. Input leads 308c and 309h to comparators 308 and 309
receive voltages representing manifold absolute pressure (the
V.sub.amp input 308b) and acceleration (the .DELTA.TH, for change
in throttle linkage position, input 309g) respectively. These two
leads are also coupled by capacitors 308a and 309a to ground. In
addition, input lead 309h is coupled through variable resistor 309c
and resistor 309b to positive voltage source 310b and also through
resistors 309d, 309f and 309e to negative voltage source 312. The
sliding contact on resistor 309c sets the threshold voltage for
comparator 309.
Comparator 309 produces a low-level output signal in response to a
positive-going ramp signal on lead 309j going more positive than
the voltage at the wiper of potentiometer 309c. This low-level
output signal is applied to one input lead to NOR gate 315. For
reasons to be explained shortly, NOR gate 315 thus produces a
high-level signal.
NOR gates 314 and 315 are connected as an RS flip-flop. When the
output signal from amplifier 307 is below the level of the
reference signal on lead 309h, comparator 309 produces a high-level
output signal. It should be noted that the reference signal on lead
309h to comparator 309 always has a higher value than does the
reference signal from source 308b which is transmitted on lead 308c
to comparator 308. (i.e., V.sub.308c < V.sub.309h). Thus the
output signal from NOR gate 315 is low-level. This low-level signal
is transmitted through resistor 316 to the base of PNP transistor
317 thereby turning on transistor 317. As described above, the
collector voltage of transistor 317 maintains conducting the
channels associated with FET transistors 303 and 306. When,
however, as described above, the positive-going ramp signal from
amplifier 307 reaches a selected value (V.sub.309h), the output
signal from comparator 309 drops to low-level thereby switching the
output signal from NOR gate 315 from low-level to high-level. This
high-level output signal turns off transistor 317 and is fed back
to the other input of NOR gate 314. NOR gate 314 produces a
low-level signal which is applied to the base of transistor 318
through resistor 319. This low-level signal turns on transistor 318
thereby raising the voltage on the gates of the FET transistors 304
and 305 to zero. Consequently, these two transistors turn on while
transistor 317 shuts off dropping the gate voltages of, and thus
turning off, FET transistors 303 and 306. The +TEMP signal from the
temperature transducer is now applied through resistor 301 to the
input lead of operational amplifier 307. The charge previously
built up on capacitor 307f now is dissipated. Accordingly, the
level of the output signal from operational amplifier 307 drops.
When this output signal drops beneath the level of the signal
V.sub.amp from source 308b on lead 308c to comparator 308, the
output signal from comparator 308 drops to a low level. This turns
off transistor 318 and turns on again transistor 317.
Thus the output signal from amplifier 307 assumes a triangular
shape, as shown in FIG. 2. The period of the waveform varies with
the rate at which capacitor 307f charges and discharges. The higher
the charge rate or current, the shorter the period. The current, in
turn, is directly proportional to the voltage difference between
the +TEMP and -TEMP input leads. As the potential difference
between the signals on lead 308c to comparator 308 and lead 309h to
comparator 309 increases, the amplitude of the periodic triangular
shaped wave of amplifier 307 increases and thus the period of this
wave increases. This results in a longer injection time.
Conversely, as the potential difference between the signals on
these two leads decreases, the injection time decreases. The
potential on lead 308c is controlled mainly by manifold absolute
pressure. (See FIG. 4b, amplifier 430). In addition, engine speed
also influences the particular signal level on lead 308c.
The voltage .DELTA.TH from source 309g which controls the voltage
on lead 309h to comparator 309 is primarily controlled by the
output signal from the circuit shown in FIG. 8 which represents the
position of the throttle and the rate of change of position of the
throttle.
It should be noted that the triangular signal from operational
amplifier 307 makes it possible to easily service the system by
merely looking at the slope and amplitude of the output signal from
operational amplifier 307. The amplitude of this output signal is
primarily controlled by the manifold absolute pressure and
secondarily by engine crankshaft frequency. The slope of this
trangular waveform, on the other hand, is controlled primarily by
input temperatures and secondarily by transient operating
conditions such as wide-open throttle. Thus, errors in the
injection period can be attributed to either an incorrect amplitude
of the output signal from operational amplifier 307 or, an
incorrect slope on this output signal. This feature thus allows the
system to be analysed when the injection period is incorrect to
determine whether or not the error arises because the output signal
from amplifier 307 has an improper amplitude, in which case the
error is in the manifold absolute pressure section of the system,
or from an improper slope, in which case the error is in the
temperature sensing portion of the system.
Any particular component in the system can easily be replaced by a
component known to be functioning correctly and the influence of
this component on the output signal determined. If there is no
change in the shape of this signal, then the component replaced is
known to be functioning properly and the search for the improperly
functioning component continues until this component is found.
When the error is not in the external transducers, but rather in
the processing circuitry itself, analysis of the trianguluar output
signal from amplifier 307 for known values of all the input
parameters which affect this signal enables one to determine the
particular section of the processing circuitry which is
malfunctioning.
The RS flip-flop comprising gates 314 and 315 produces a square
wave from the output lead of NAND gate 314a as shown. If desired,
an output signal can also be taken from the output lead of NOR gate
315 or from numerous other places in the circuit. The output signal
from oscillator 30 is, as described above, used to drive pulse
groups through delay 20 (FIG. 1).
FIG. 3 shows the circuitry for detecting, and operating on, signals
from transducers connected to the throttle linkage, the engine
starter control circuit, the water temperature and the air
temperature. First, the operation of the circuitry connected to the
wide open throttle transducer will be described. The throttle is
fully depressed only when the driver accelerates at a maximum rate.
Maximum acceleration requires more fuel than does normal
acceleration. In this condition, a cam, electronic sensor, or other
means actuated by the throttle linkage grounds or brings to a
low-level the lead in FIG. 3 labeled WOT thereby shutting off
transistor 331. (Diodes 331a and 331b, connected to the base of
transistor 331, reduce the probability of noise affecting the state
of transistor 331. These diodes can be omitted, if desired.) The
collector voltage on transistor 331 is thus driven to the high
level represented by the positive voltage source V.sub.3. This
turns on transistor 332. The collector voltage on transistor 332
then drops to a low level, thus lowering the input voltage to
operational amplifier 338. This input voltage is applied to
operational amplifier 338 through a filter comprising resistor 338
a and capacitor 337. Capacitor 337 smooths the transition from
wide-open throttle to steady state operating conditions. As is well
known, the output voltage V.sub.o from an operational amplifier is
related to the input voltage V.sub.i by the approximate
equation
V.sub.o .congruent. -V.sub.i (R.sub.1 /R.sub.2) (1)
which can be rewritten with respect to amplifier 338 as
V.sub.340 .congruent. -v.sub.337a (R.sub.338b /R.sub.338a). (2)
In equation (1), R.sub.1 is the feedback resistor and R.sub.2 is
the input resistor through which the input signal passes to the
input lead. Usually an operational amplifier has high gain so the
nongrounded input lead of the operational amplifier can be treated
as a virtual ground.
The output signal from operational amplifier 338 is next
transmitted to a resistive network comprising resistors 340a, 342,
340b, 340d and 340c. Resistors 340b and 342 are negative
temperature coefficient thermistors, the resistances of which
decrease as the engine's water temperature increases. This network
essentially serves as the input resistor (R.sub.2 in equation (1))
between the input signal and the input lead to operational
amplifier 340. Feedback resistor 340f is equivalent to resistor
R.sub.1 in equation (1). The circles labelled 340i, 340j and 340k
denote connectors by which external transducers are connected to
the processing circuitry. This processing circuitry typically is an
integrated circuit. As the resistances of resistors 342 and 340b
decrease, the output voltage from operational amplifier 340
increases. As explained above in conjunction with equation (1),
this increases the difference between the voltage on the leads
labeled +TEMP and -TEMP (FIGS. 2 and 3) and decreases the period of
the output signal from oscillator 30 (FIGS. 1 and 2).
Operational amplifier 341, together with input resistors 341e,
341f, feedback diode 341c and capacitor 341b, output resistor 341g
and diode 341a is a feedback circuit which prevents the output
signal of operational amplifier 340 from becoming greater than that
at unity gain. This feedback circuit comes into operation when the
resistance of thermistors 340b and 342 drops below the value
associated with unity gain for operational amplifier 340. This
entire feedback circuit is in parallel with feedback resistor
340f.
Diodes 341a and 341c associated with operational amplifier 341 do
several things. Diode 341a insures that the output signal of
operational amplifier 341 as seen by the input of operational
amplifier 340 is of one polarity only. Diode 341c limits unwanted
excursions of operational amplifier 341. Capacitor 341b, connected
in parallel with diode 341c, insures gain and phase compensation of
operational amplifier 340 and 341 to prevent circuit
oscillation.
The next stage of the circuit comprises another operational
amplifier stage with feedback very similar to the just described
operational amplifier stage. Operational amplifier 344 has an input
resistive network comprising resistors 344a, 344b (both thermistors
which measure air temperature) and resistors 344c and 344d.
Capacitor 344g filters out unwanted noise. Resistors 344h and
variable resistor 344i are connected in the feedback path of
operational amplifier 344. Resistor 344i provides stage gain
adjustment. These resistors are equivalent to resistor R.sub.1 in
equation (1). Operational amplifier 345 and associated circuitry
provides a feedback path to control the output signal from
operational amplifier 344 in the same manner as described above in
conjunction with operational amplifiers 340 and 341. Amplifier 345
and its associated circuitry can be omitted, if desired, depending
upon the specified system response to input temperature and the
absolute values of the thermistors chosen for resistors 344a and
344b. For example, when the control system is used over a wide
temperature range, operational amplifier 345 might be omitted.
The output signal from operational amplifier 344 represents the
influence of air temperature on the period of oscillator 30 (FIGS.
1 and 2). It should be noted from equation (1) that the output
signal V.sub.o344 from amplifier 344 is related to the input signal
V.sub.i340 to amplifier 340 as follows (provided that the feedback
circuits which include amplifiers 341 and 345 are inactive):
##EQU1## Resistors R1 and R2 with the appropriate subscripts
represent the combined resistances connected in the feedback
circuits and inputs circuits of the correspondingly numbered
operational amplifiers, respectively. From equation (3) it is
apparent that the output signal V.sub.0344 represents the
multiplicative effect of temperature changes reflected in the
values of R.sub.2-340 and R.sub.2-344.
When starting a cold engine, more fuel is required than for normal
operating conditions at the same temperature. Thus, in FIG. 3, a
crank motor transducer produces a positive output signal on lead
355 upon the application of a voltage to the starter motor. This
signal turns on transistor 333. Transistor 333 thus lowers the
output voltage applied to one input lead of operational amplifier
338. Capacitor 337 stores a charge reflecting a new input voltage
to operational amplifier 338. (It should be mentioned that
capacitor 337 performs in the same way whether the voltage drop
across resistor 334 is generated by a wide open throttle signal or
a crank motor signal.) The time during which extra fuel is injected
into the engine after the removal of the crank signal is determined
by the values of resistors 334 and 338a and capacitor 337. The
charge stored on capacitor 337 depends on the voltage drop across
resistor 334. When voltage is no longer applied to the starter
motor, the charge on capacitor 337 prevents the circuit from
immediately shutting off extra gas applied to the engine. But, as
the charge on this capacitor returns to normal, the period of
oscillator 30 and thus the fuel supplied to the injectors gradually
returns to the normal value dictated by the other engine operating
conditions. The size of capacitor 337 is varied to reflect the
different engines or vehicles used with the electronic control
system of this invention. As the size of the engine increases, the
engine takes longer to respond to changes in demand and capacitor
337 is made larger. Also, as vehicle size increases, capacitor 337
is made larger because more fuel is required to accelerate the
vehicle.
If a driver accelerates using wide open throttle, but then suddenly
takes his foot off the accelerator, another circuit to be described
later shuts off all fuel to the engine. Meanwhile, the charge on
capacitor 337 returns to normal. The result is that minimal excess
hydrocarbons and carbon monoxide in the form of incompletely burned
fuel are expelled into the environment. For a large engine, the
time constant of the RC circuit of which capacitor 337 is a part is
approximately one to two seconds.
Operational amplifier 338 should have a low output impedance to
reduce the errors contributed by this impedance to the signal
produced by thermistor 340b. Likewise the output impedance of
operational amplifier 340 should be low to similarly minimize the
impact of this impedance on the following temperature sensing
thermistors. Output resistances of operational amplifiers are
typically less than 10 ohms. Thermistors, by comparison, have an
impedance from several hundred ohms to several thousand ohms.
Thermistors have been described in FIG. 3 for sensing water
temperature and air temperature. An additional operational
amplifier stage can be added, if desired, for fuel temperature.
Other operational amplifiers can be added with gain-controlling
thermistors to sense any other temperatures of importance in
controlling the fuel demanded by the engine. Among these
temperatures are exhaust gas temperature, oil temperature, block
temperature, and in more sophisticated systems, individual cylinder
temperatures.
PROCESSOR 10; CONTROL OF INJECTION TIMING AND SYNCHRONIZATION
Processor 10 processes the signals from the 90.degree. and
720.degree. transducers.
FIGS. 5a and 5b show in more detail the amplification circuits used
with the 90.degree. transducer and the 720.degree. transducer. The
operation of these transducers will be described in conjunction
with the 90.degree. pickup circuitry. The circuitry associated with
the 720.degree. pickup works in substantially the same manner, only
less frequently. A signal from the 90.degree. transducer, which can
be mounted on the distributor shaft, crankshaft, or camshaft, is
detected and transmitted directly on leads 501 and 502 to
difference amplifier 507. The output signal from amplifier 507 is
connected to one input lead of AND gate 511 and is filtered by
capacitor 509. The other input lead to this AND gate is connected
to a positive voltage source. The output signal on lead 513 from
AND gate 511 changes from a low level to a high level in response
to a pulse detected by the 90.degree. pickup transducer. The
differential mode connection from the 90.degree. transducer to
difference amplifier 507 prevents common mode signals and stray
signals from activating AND gate 511.
The 720.degree. signal is processed in a similar manner using the
circuit of FIG. 5a.
The output signal from the 90.degree. pickup circuitry on lead 513
is sent to transient processor 50 (FIG. 1), which will be described
later. Processor 50 provides special corrections for certain types
of operations. The output signal from the 720.degree. pickup
circuitry is sent to processor 10 only.
It should be noted that all degrees used in this specification are
degrees of rotation of the crankshaft. In a four-cycle,
eight-cylinder engine, a fuel-air mixture is inducted into a new
cylinder every 90.degree. rotation of the crankshaft. For all types
of four-cycle engines, an engine cycle is completed every
720.degree. rotation of the crankshaft.
FIG. 5c shows in more detail the logic circuitry of processor 10
and digital delay 20. The output signal from processor 10 (FIG. 1)
comprises two pulses when this output signal is generated by a
signal from a 90.degree. pickup transducer. However, when an input
signal is received from the 720.degree. pickup transducer,
processor 10 produces a four pulse output signal.
The two pulse output signal occupies two locations in digital delay
20 while the four pulse output signal from processor 10 occupies
four locations of digital delay 20. The 90.degree. pickup signal is
inverted in amplifier 523 (FIG. 5c) and then sent to 90.degree.
memory 525. Memories 525 and 526 may typically comprise JK (or D)
flip-flops Fairchild device type 9L24 as manufactured by the
assignee of the present application. There, the 90.degree. signal
is held for a period of time sufficient to place two pulses in
shift register 530-1, the first register in digital delay line 20.
The digital delay line 20 comprises shift registers 530-1, 530-2 .
. . 530-N, and 531; which shift registers may typically comprise
8-bit shift registers Fairchild device type 93L28 as manufactured
by the assignee of the present application. The presence of pulses
in the first two locations in shift register 530-1 is detected by
NAND gate 527. The signal on the input lead to NAND gate 527 from
720.degree. memory 526 is normally high level. The signals on the
two input leads to NAND gate 527 from shift register 530-1 are
normally low level. Thus NAND gate 527 produces a normally
high-level output signal. However, upon the transfer of the two
high-level pulses from memory 525 to the first two locations of
shift register 530-1, the signal levels on all three input leads to
NAND gate 527 will go high and the output signal from NAND gate 527
will go to a low level. This produces a high-level output signal
from NOR gate 528 which in turn is transmitted through inverter 529
to the reset terminal of 90.degree. memory 525 to clear this
memory. Thus, the output signal from 90.degree. memory 525 drops to
a low level again. Consequently, the remaining clock pulses from
oscillator 30 place low-level signals in the first location of
shift register 530-1 rather than a high-level signal. Meanwhile,
the high-level pulses formerly in this location are shifted through
delay line 20.
The signal on the output lead from 720.degree. memory 526 is
normally high level. When, however, the 720.degree. pickup signal
is received, the output signal from 720.degree. memory 526 drops to
a low level thereby disabling NAND gate 527. However, when shift
register 530-1 contains four pulses in its four locations, NAND
gate 534 is activated and produces a low-level output signal. This
low-level output signal is transmitted through NOR gate 528 and
inverter 529 and again changes the output signal from 90.degree.
memory 525 from high level to low level.
The 720.degree. memory 526 is deliberately activated slightly
earlier than the 90.degree. memory 525 and thus disables NAND gate
527 before memory 525 is activated. Thus, the 90.degree. memory
will have a high level output signal stored in it for four periods
of the signal from oscillator 30 during which time the output
signal from 720.degree. memory 526 is low level (activated). The
output pulse from inverter 529 also clears 720.degree. memory
526.
The presence of two pulses in shift register 530-1 denoting the
receipt of a signal from the 90.degree. transducer by processor 10
results in NAND gate 535 producing a low-level output pulse. NAND
gates 534 and 535 comprise data decode 100 (FIG. 1). The low-level
output pulse from gate 535 is sent to "A" counter 90 (FIG. 1).
Counter 90 controls, through injector decode 80, the particular
fuel injector through which fuel is to be injected and initiates
fuel injection by a change in its state in response to the signal
from data decode 100. Injector decode 80 selects in sequence the
injectors to be activated in accordance with the firing or
injection order of the engine. The first injector to be activated
is opened for a time determined by the time necessary for the two
pulses in digital delay 20 to pass from the first shift register
530-1 (FIG. 5c) in delay line 20 to the last shift register 531 in
this delay line. NAND gates 532 and 533 comprise data decode 60
(FIG. 1). When the two pulses from a 90.degree. pick-up transducer
reach shift register 531, a signal is sent from NAND gate 533,
which detects the presence of these two pulses in the first two
locations in shift register 531, on lead 539 to "B" counter 70
(FIG. 1). Counter 70 then sends a signal to injector decode 80 to
shut the injector valve. Each signal from "B" counter 70 to
injector decode 80 is routed to the correct injector valve, as is
each signal from "A" counter 90, by the logic matrix within
injector decode 80. It should be mentioned that injector decode 80
can be a standard demultiplexing circuit.
As explained above, the frequency of the output signal from
computing oscillator 30, and thus the period of this signal, vary
in response to the input signals to controlling oscillator 30.
Digital delay line 20 has a fixed number of stages M where M - X =
N. X is the number of extra stages in delay line 20 required to
detect the presence of pulse groups at the beginning and end of
delay line 20. In this case, X is four (4). The real time period
required for a signal to pass through delay 20, is that elapsed
time period needed for the computing oscillator to generator N
pulses. This elapsed time defines the period that a currently
active injector will be held open. Accordingly, the times for which
the injector valves are left open as the result of control signals
from injector decode matrix 80 vary smoothly with variations in the
frequency of the output signal from oscillator 20. The output
signal from the oscillator is updated N times while an injector
valve is open. Because the time that an injector is open is the
integral over time of the period of the output signal from
oscillator 30, noise tends to have little effect on the resultant
injection time. The frequency in cycles per second of the output
signal from oscillator 30 is typically greater than 2/5 times the
engine RPM.
It should be noted that the pulses present in 90.degree. memory 525
and 720.degree. memory 526 (FIG. 5c) are invariably removed or
erased prior to the removal of the 90.degree. or 720.degree.
pick-up signals on leads 521 and 522 respectively and certainly
long before the valve gear train rotates 90.degree..
Upon activation of the 720.degree. transducer, four pulses are
injected in sequence into delay line 20. The receipt of the second
of the four high level pulses in shift register 531 activates NAND
gate 533 which steps "B" counter 70 to denote the injector then
open. This activates injector decode 80 to close this injector.
The receipt of the fourth high level pulse in shift register 531
(FIG. 5c) activates NAND gate 532. NAND gate 532, which produces a
normally high level output signal, now sends a low level signal to
"B" counter 70 (FIG. 1) to clear this counter. The output signal
from NAND gate 534 (FIG. 5c) is similarly sent to "A" counter 90
(FIG. 1) to clear this counter once each engine cycle. Thus NAND
gates 534 and 532 synchronize the system once each engine
cycle.
Both the "A" counter 90 and the "B" counter 70 are essentially
binary registers which can store pulses representing P digital
numbers representing the numbers of the cylinders into which fuel
is to be injected. In an eight cylinder engine, counters 70 and 90
can store pulses representing digital numbers from 0 to 7. By the
use of feedback with a three bit counter, one can restrict the
maximum count stored in the counter to six and thus convert the
counter to use with six cylinder engines. The number stored in A
counter 90 represents the cylinder which is to receive the fuel
which is being, or has been injected. Setting the count in A
counter 90 to zero in response to a change in state of the
720.degree. pick-up signal means that the injector corresponding to
a zero in A counter 90 has been opened. Setting B counter 70 to
zero in response to the delayed 720.degree. pick-up signal reaching
shift register 531 means that the injector corresponding to zero
count will be closed.
COUNTERS 70 AND 90 AND INJECTOR DECODE 80
FIG. 6 shows the manner in which the signals from NAND gates 534
and 535 (FIG. 5c) are used to control the state of A counter 90
(FIG. 1). Counter 90, shown in FIG. 6, comprises one-shot 605 and
counter 608. Counter 608 may typically comprise a 4-bit binary
counter Fairchild device type 93L16 as manufactured by the assignee
of the present application. Signals denoting fully closed throttle
position (denoted FCT) and flooding of the engine are transmitted
through NOR gate 603 to one input lead of AND gate 604. Open clock
pulses from NAND gate 535 (part of Data Decode 100, FIGS. 1 and 5c)
are transmitted to the other input lead of AND gate 604. As will be
explained shortly, signals from one-shot 605 in response to the FCT
or flood conditions prevent additional fuel from being injected
into each cylinder. AND gate 604 activates one-shot 605. The period
of one-shot 605 is controlled by the values of resistor 605b and
capacitor 605a connected to one-shot 605 and the positive voltage
source as shown. The other input lead to AND gate 604 is connected
by lead 601 to the output lead from NAND gate 535 (FIG. 5c). NAND
gate 535 produces an output pulse every time the 90.degree. pickup
transducer produces a pulse. The pulse from gate 535 triggers
one-shot 605 and also is transmitted directly to counter 605 where
it changes the count by one unit. Periodically, an output pulse is
produced by NAND gate 534 indicating the receipt of a signal from
the 720.degree. transducer. This output pulse is transmitted on
lead 602 directly to counter 608 and there resets counter 608 to
zero. The count in counter 608 controls the states of the output
signals on lead 609a through 609n from opening decode 609. Opening
decoder 609 may typically comprise a one-of-ten decoder Fairchild
device type 93L01 as manufactured by the assignee of the present
application. In one embodiment counter 608 can store up to a three
(3) bit binary code word. Other embodiments of counter 608 can
store n-bit binary code words, where n is a selected integer. When
counter 608 thus receives a pulse, the signal on the output lead
from opening decode 609 corresponding to the new binary code word
stored in counter 608 goes to a low level. This low-level signal
has a duration controlled by the output pulse from one-shot 605.
One-shot 605 was triggered by the same pulse from NAND gate 535
that changed the state of counter 608.
When the system is in synchronization, the count in counter 608
will go to zero just prior to the receipt of the 720.degree. reset
pulse. From the description of the circuitry of FIG. 5c, it should
be remembered that the 720.degree. reset pulse comes from NAND gate
534 two clock periods later than does the 90.degree. pulse signal
from NAND gate 535. Thus, if the system is in synchronization, open
counter 608 will already have been set to zero and the reset pulse
from NAND gate 534 (which detects the 720.degree. transducer
signal) will arrive after the 90.degree. transducer pulse has
advanced the counter 608 to zero. Thus when counter 608 is
synchronized with the rest of the system, there is no change in the
state of this counter upon the receipt on lead 602 of the output
signal from NAND gate 534 (FIG. 5b).
If, however, counter 608 is out of synchronization, the reset pulse
from 720.degree. decoder NAND gate 534 would reset counter 608 to
zero. The error in injection time of the first cylinder in the
injection sequence resulting from this lack of synchronization is
the two clock-pulse delay necessary to generate the 720.degree.
signal. Because of valve inertia, the injector will not have opened
significantly in that time. By increasing the length of the delay
line, or the clock frequency, or both, this error can be reduced.
Lack of synchronization can possibly also cause excessive fuel in
some cylinders and not enough fuel in other cylinders.
FIG. 6 also shows closing decoder 611 which closes the injectors.
Closing decoder 611 may also typically comprise a one-of-ten
decoder Fairchild device type 93L01. The closing clock signal is
transmitted to close counter 610, part of B counter 70 (FIG. 1),
from one of two sources; NAND gate 533 produces an output pulse
when the 90.degree. pickup pulse group transmitted into delay line
20 reaches shift register 531. Close counter 610 may also typically
comprise a 4-bit binary counter Fairchild device type 93L16. This
pulse from NAND gate 533 is transmitted to close counter 610 to
change the count recorded in this counter. Upon the receipt of the
new count, the signals from close counter 610 representing this new
count are transmitted to closing decoder 611 which activates the
proper output leads 611a through 611n to close the injector
corresponding to the cylinder represented by the new number in
counter 610. Counter 610 is synchronized by a signal from NAND gate
532 (FIG. 5c).
The output signals from the opening decode circuit 609 are sent two
places. First, these signals are sent to the corresponding input
lead of circuits 614 and 615. Circuits 614 and 615 each contain
four flip-flops and thus control eight injectors. Circuits 614 and
615 may each for example, comprise a quad latch Fairchild device
type 93L14 as manufactured by the assignee of the present
application. A low level signal on output lead 609a is transmitted
to the input lead to flip-flop 1 of circuit 614, on the lead
labeled 609a. This signal changes the state of this flip-flop. The
signal on the output lead from flip-flop 1 in circuit 614 is
transmitted through half adder 616a and buffer-inverter 617a. The
current from inverter 617a comprises a low-level holding current
which holds open an injector until a signal from closing decoder
611 changes the state of the flip-flop. The output signal on lead
609a from opening decoder 609 simultaneously is sent to the
corresponding NOR gate 613a. This produces a high level signal on
the output lead from NOR gate 613a. This high level signal drives
the same injector valve hard open thereby increasing the speed with
which the injector valve opens and thus the amount of fuel placed
in the cylinder in a given time.
It should be noted that the time an injector is left open is
determined by the time it takes for the pulse groups to travel
through digital delay line 20 (FIGS. 1 and 5c). As engine speed
increases, a pulse group which opens a first injector can still be
traveling through delay line 20 when a second pulse group is
injected into delay line 20 by the next signal from the 90.degree.
transducer. In response to this second pulse group entering the
delay line, a second injector is opened while the first injector is
still open. As the engine speed increases, up to seven injectors
can be open at the same time using the system of this invention. In
theory, all eight injectors can be open at the same time. However,
close counter 610 produces a closing signal for 90.degree. of
crankshaft rotation. Thus any and each injector must be closed for
one-eighth of an engine cycle. Therefore, at any time during the
engine cycle, one injector must be closed. The system, however, can
be modified to avoid this limitation by having close counter 610
produce a "close" pulse of a more limited duration.
In one embodiment fuel injection preferably occurs a few degrees
before the intake valve to the cylinder opens. Typically, the
intake valve is open for about 200.degree. to 230.degree. rotation
of the crankshaft. On the other hand, the injectors are injecting
fuel over from 10.degree. to 20.degree. rotation of the crankshaft
at idle and up to 600.degree. at full power. If the driver decides
to accelerate before the fuel being pulled into a cylinder has been
ignited, the injector associated with that cylinder can be reopened
to inject more fuel into the manifold and thus into the cylinder in
response to the acceleration signal. This feature provides
additional flexibility for the operation of the system and is
described next.
DOUBLE INJECT DECODE 607, 612, 616 AND 618
FIG. 6 also shows double injector decoder 612. The decoder 612 may
also typically comprise a one-of-ten decoder Fairchild device type
93L01 as manufactured by the assignee of the present application.
This decoder is provided to open a previously opened and now closed
injector in response to a signal from transient processor 50 (FIG.
1) that the driver has pressed down on the accelerator.
Pressing down on the accelerator results in a high-level signal
being transmitted on lead 606 to one input lead of NAND gate 607
thereby enabling NAND gate 607. The generation of this pulse is to
be described in conjunction with FIG. 8. When the pulse from NAND
gate 535 (FIG. 5c) is transmitted on lead 601 to AND gate 604
thereby activating one-shot 605, the output signal from one-shot
605 goes to a high level. This output signal is applied to the
other input lead of NAND gate 607. NAND gate 607 thereby puts out a
low-level output signal which activates double injector decode 612.
Double injector decoder 612 works inthe same way as open decoder
609 but is programed to open the injector associated with a
cylinder for which fuel was previously injected so that an
additional amount of fuel can be injected for use by that
cylinder.
It should also be noted that the acceleration signal on lead 606 is
transmitted to the half-adders 616a through 616d and 618a through
618d. These gates are activated either by a single signal from the
corresponding connected flip-flop in register 614 or 615 or by the
simultaneous presence of an acceleration signal on lead 606
together with a signal on the next following flip-flop in the
registers 614 or 615. Thus the presence of a signal on acceleration
lead 606 results in a given flip-flop in registers 614 or 615
activing not only the half-adder 616 or 618 connected to that
flip-flop, but also the preceding half-adder connected to the
flip-flop.
MANIFOLD PRESSURE SIGNAL PROCESSOR
FIG. 4a through 4d show the electronic circuitry used to generate
signals representing manifold pressure. As manifold pressure
increases, the airflow through the manifold increases and thus the
fuel required to be injected into each cylinder increases. This
means that the injection time must also increase. An increased
injection time requires a decrease in the frequency of the output
signal from computing oscillator 30 (FIG. 1). Accordingly, the
output voltage V.sub.AMP from operational amplifier 430 (FIG. 4 b),
to comparator 308 (FIG. 2) must decrease algebraically. This output
voltage changes the reference level on one input lead to comparator
308, thus changing the time required for the output signal from
operational amplifier 307 to change the state on the flip-flop
comprised of elements 314 and 315.
The signal representing manifold pressure is sent through resistor
411a to input lead 411h of operational amplifier 411. The voltage
on input lead 411h of operational amplifier 411 is held at virtual
ground as in a standard operational amplifier with feedback. Diode
411d insures that when the input voltage V.sub.in drops beneath a
selected reference voltage established by voltage source 412 and
resistors 411a and 411b, the output voltage from the operational
amplifier 421 will be clamped above virtual ground by the voltage
drop of a forward-biased PN junction. On the other hand, as the
input voltage V.sub.in to operational amplifier 411 climbs above
the selected reference voltage, the output voltage from the
operational amplifier drops linearly at a rate controlled by the
ratio of resistor 411g to resistor 411a. Diode 411d acts as an open
circuit in this circumstance while diode 411e becomes forward
biased.
By varying the voltage represented by source 412 or either of
resistors 411a and 411b, the voltage V.sub.in at which the
characteristic curve of V.sub.out versus V.sub.in assumes a
negative slope is varied, as shown in FIG. 4d. FIG. 4d shows
several curves all with different values of V.sub.in at which the
breakpoint in the curve of V.sub.out versus V.sub.in occurs. The
curve which passes through the center of the graph has voltage
source 412 equal zero. When voltage source 412 is positive, the
breakpoint in the characteristic curve shifts to a negative value
of V.sub.in.
The slope of the non-horizontal portions of the curves in FIG. 4d
is given by V.sub.out /V.sub.in = -R.sub.1 /R.sub.2. Reversal of
the polarity of the diode as shown by the diode in dashed lines in
FIG. 4e results in a curve shown by the dashed lines in FIG. 4d.
Thus the output signal from operational amplifier 411 with diodes
connected as shown has a piece-wise linear characteristic.
Operational amplifier 421 operates in the same manner as does
operational amplifier 411.
The reference voltage 412 connected to input lead 411h is selected
to correspond to a selected low pressure, such as five inches of
mercury absolute which in turn corresponds to a very low air flow
rate to the engine. Thus, for manifold pressure beneath five inches
of mercury, the injection time is minimized to a selected value. In
this condition, the typical engine has a negative torque output. As
the manifold pressure increases, signifying a larger air flow to
the engine, operational amplifier 411 begins to produce an
increasingly negative output voltage. This output voltage then is
transmitted to multiplying circuit 414. Likewise, operational
amplifier 421 produces an increasingly negative output voltage as
the manifold pressure increases above the pressure associated with
its reference voltage as set by resistors 421a, 421e and 421f. The
output signal from operational amplifier 421 is likewise sent
through resistor 422 to multiplying circuit 424.
Circuits 414 and 424 are shown in more detail in FIG. 4f. The input
voltage to the circuit is controlled by the settings of
potentionmeter resistors 440c and 440d. The output voltages from
the operational amplifiers are brought into circuits 414 and 424 on
leads 9.
An additional signal is brought into each of multiplying circuits
414 and 424 on lead 4. These signals are derived from operational
amplifiers 407 and 408 (FIG. 4a) which in turn operate on signals
from operational amplifiers 403, 404 and 405 (FIG. 4a). These last
three amplifiers operate in the same manner as operational
amplifiers 411 and 421 except that the diodes in the feedback
circuits of amplifiers 403, 404 and 405 are reversed in polarity.
The polarities of the diodes associated with each operational
amplifier in FIG. 4a are determined by the shape of the transfer
function desired for the circuit. Thus the transfer characteristics
of these operational amplifiers correspond to the dash curve shown
in FIG. 4d with the break-point in the characteristic of each
amplifier being controlled as described above.
The input signal to operational amplifiers 403, 404 and 405 are
proportional to engine freuency. These signals can be generated
from a frequency signal obtained from the crank shaft or the
distributor or any other rotating part of the engine suitable for
such a measurement. FIG. 7 shows circuitry suitable for generating
these signals.
The output signals from operational amplifiers 403 and 404 are fed
to the input lead of operational amplifier 408. The output signal
from this operational amplifier is denoted S1 and is the input
signal on lead 414a of multiplier 414 (FIG. 4b). FIG. 4hshows a
typical transfer function of S1 versus engine frequency.
Likewise, the output signal from operational amplifier 405 is
passed through operational amplifier 407 and then is sent on the
lead denoted S2 to lead 424a of multiplier 424 as shown in FIG. 4b.
FIG. 4g shows a typical transfer function of S21 versus engine
frequency. Note that the transfer function of FIG. 4g has only one
breakpoint because only one active diode circuit (the circuit
associated with amplifier 405) is used to generate the curve of
FIG. 4g. The transfer function of FIG. 4f has two such breakpoints
because two such circuits (the circuits associated with ampliiers
403 and 404) are used to generate the curve of FIG. 4f.
Each multiplier comprises a well-known commercially available
circuit such as the .mu.A 795, made by Fairchild Camera and
Instrument Corporation. Each multiplier takes two input signals on
leads 4 and 9 and produces an output signal on lead 14 proportional
to the product of these two input signals. The way in which these
multipliers work is well known and thus these multipliers will not
be described in detail.
The output signals from multipliers 414 and 424 (FIG. 4b) are
transmitted through input resistors 414b, 414c and 424b, 424c to
the input leads of operational amplifiers 415 and 425 respectively.
The output signals from operational amplifiers 415 and 425 are then
transmitted to one input lead of operational amplifier 430 through
input scaling resistors 415c and 425c. The resulting voltage
V.sub.AMP from operational amplifier 430 is sent to input lead 308b
(FIG. 2).
FIG. 4c is a curve of injection time versus the ratio of manifold
absolute pressure to atmosphere pressure. As injection time
increases, the period of the signal from oscillator 30 (FIG. 1)
must increase and thus V.sub.AMP must decrease algebraically. Note
that the slope of the output signal from operational amplifier 307
is independent of V.sub.AMP. Thus the period of the output signal
from amplifier 307 is directly proportional to the amplitude of
V.sub.AMP.
It should be noted that the number of discontinuities in the curve
of FIG. 4c can be controlled by controlling the number of
operational amplifiers used to generate this curve.
TRANSIENT PROCESSOR 50
FIG. 7 shows the circuitry used to control the cutoff of fuel to
the engine. Pulses from the tachometer transducer (located on the
crankshaft, for example) are sent on lead 700a to one-shot 701.
One-shot 701 produces an output pulse of about 3 milliseconds
duration. Operational amplifier 703 has a feedback network
comprising a parallel-connected capacitor 703d and resistor 703c
and an input resistor 703a. This configuration results in
operational amplifier 703 producing an output voltage proportional
to the frequency of the pulses from one-shot 701. In one
embodiment, amplifier 703 was set to produce 1 volt per 1,000 rpm
of the engine.
The output signal from operational amplifier 703 is sent through
resistors 705a and 705f to the ungrounded input leads of
comparators 706 and 707 respectively. Output lead 700b connected at
node 700e to the output lead from amplifier 703 carries the signal
from amplifier 703 to input lead 403i to operational amplifier 403
(FIG. 4a). The output signal from amplifier 703 is always negative
in this embodiment.
An input voltage derived from a temperature transducer (which might
measure engine coolant temperature, for example) is transmitted to
amplifier 704 on lead 700c. The output signal from amplifier 704,
which provides a correction signal to compensate for deviations in
the engine temperature from its normal operating temperature, is
sent to the non-grounded input leads of comparators 706 and 707
through resistors 705c and 705d, respectively.
The system has structure for preventing the engine from dying after
the fully closed throttle position is sensed. The fully closed
throttle position is sensed by a transducer on the throttle
linkage. An output signal denoting fully closed throttle is sent on
lead 700d to JK flip-flop 708. The output signal from flip-flop 708
then stops the injection of fuel. When the engine slows to a
selected speed a given amount above the speed at which the engine
will die, fuel is resupplied to the engine. An enabling signal,
sent to flip-flop 708 from comparator 707, insures that fuel is not
shut off unless the engine speed is sufficiently above the cut-off
speed of the engine to insure that there is some hysteresis in the
engine's fuel control function.
The signal to disable one-shot 605 (FIG. 6) is transmitted from the
output lead on flip-flop 708 through NOR gate 709 to NOR gate 603
(FIG. 6). Normally, the output signal from NOR gate 709 is low
level. The low-level output signal from flip-flop 708 corresponding
to a sudden deceleration or removal of the foot from the
accelerator, results in a high-level output signal being produced
on the output lead, of NOR gate 709. This high-level signal
disables one-shot 605.
In addition, a high-level output signal can be produced on the
output lead of NOR gate 709 by turning on transistor 710. This
transistor is turned on in response to a high-level signal on its
base from the crank motor transducer indicating that power is being
applied to the crank motor simultaneously with a low-level signal
on its collector from the lead labeled WOT denoting that the driver
has fully depressed the throttle. This disables one-shot 605
thereby preventing additional fuel from being injected into the
already supposedly flooded engine. The starter motor thus can draw
from the engine the excess fuel deposited in the manifold and
engine cylinders.
A high-level output signal from comparator 707 enables JK flip-flop
708 to be clocked off by a fully closed throttle signal from the
throttle linkage transducer. Flip-flop 708 is reset when one of two
events occur. First, if the engine speed drops beneath the given
value, the output of comparator 706 goes to a low level thereby
resetting flip-flop 708. On the other hand, if the throttle is
opened from the closed position, a signal is sent through capacitor
708a on lead 700d to similarly reset flip-flop 708 allowing fuel
again to be injected into the engine. Thus the output signal from
flip-flop 708 will go high reenabling one-shot 605 (FIG. 6).
When the engine is cold, more fuel is required to keep it running
at a given speed due to increased friction and reduced fuel energy
conversion efficiency. Thus, to keep the engine running, the speed
at which cut-off occurs is necessarily higher. To do this, a signal
is transmitted on lead 700c into the input network associated with
comparator 706. The signal on lead 700c labeled V.sub.KOOL
represents a temperature sensed by a temperature transducer located
at some point in the engine. This signal is transmitted through
voltage follower 704 to the node between resistors 705c and 705d.
This signal then biases the input lead of comparator 706 to a
higher voltage than would otherwise be present on this input lead
when the engine is running at its operating temperature. This
insures that comparator 706 operates to prevent fuel cut-off at a
higher engine speed than normal.
It should be noted that feedback resistor 706a associated with
comparator 706 provides a positive feedback signal to one input
lead of comparator 706. The effect of resistor 706a taken together
with resistor 706f is to provide a slight hysteresis in the
operation of comparator 706. A similar result is obtained by use of
resistor 707a and 707b in conjunction with comparator 707.
THROTTLE POSITION SIGNAL PROCESSOR
FIG. 8 shows circuitry giving an output signal representing
differentiated throttle position. Amplifier 801 and its associated
circuitry comprise the acceleration enrichment and deceleration
leaning circuitry. If the driver wishes to accelerate, and presses
down on the throttle, a throttle position transducer produces an
increasingly positive signal on lead 800a. This signal is
differentiated by capacitor 801a and resistor 801b, and amplified
by voltage follower 801. The output signal from amplifier 801 will
then also be increasingly positive. This output signal is passed
through acceleration diode 801i and resistor 801k to lead 309g to
computing oscillator .DELTA.TH input 309g (FIG. 2). This positively
increasing signal will increase the amplitude of oscillation of the
periodic signal produced by operational amplifier 307 and hence
increase the injection time.
If the driver closes the throttle, a decreasing signal will be
differentiated by capacitor 801a and resistor 801b. The
differentiated signal will be limited by diodes 801c and 801e. This
negative signal will be followed by amplifier 801 and passed
through deceleration diode 801j and resistor 801l to lead 309g
(.DELTA.TH input) of oscillator 307 (FIG. 2). This negative signal
will slightly decrease the amplitude of the periodic waveform from
amplifier 307 and decrease the injection time. The voltages
required to offset the voltage drops of acceleration and
deceleration diodes 801i and 801j respectively are offset by diodes
801g and h in the feedback circuit of amplifier 801. The over-all
peak output voltage available for amplifier 801 is determined by
the feedback network comprising resistors 801d and 801f and diodes
801g and 801h. Therefore, the output signal of amplifier 801 will
have a fast slewing condition within one diode drop above or below
ground potential. This output signal is used to enable the double
inject circuitry to be described next.
The double inject circuitry comprises a trigger comparator 802,
double inject logic 803 and 804, a double inject timer comprising
components 805, 806 and 807 and a reference circuit compromising
components 808, 809 and 810.
Tribber comparator 802 produces a positive signal on line 802g when
the input signal to amplifier 801 exceeds a reference level as
selected by trigger level resistor 802b. This positive signal on
lead 802g will trigger D flip-flop 803 which thus records the fact
that a trigger signal has arrived. The output signal from flip-flop
803 enables flip-flop 804. Flip-flop 804 is then triggered by the
next succeeding 90.degree. signal from the 90.degree. crankshaft
position transducer thus starting the double-inject mode of
operation. The double-inject signal is sent from flip-flop 804 on
lead 606 to the double-inject circuitry of FIG. 6.
The double-inject timer comprises components 805, 806 and 807.
Timing capacitor 805f is charged in a positive direction by
voltage-to-current converter 805. The voltage reference for
converter 805 is, in fact, the -TEMP signal input to oscillator 307
as shown in FIG. 2. Thus the rise rate of the voltage on timing
capacitor 805f is proportional to the operating temperatures sensed
in the engine.
Comparator 807 compares the voltage on capacitor 805f to that on
reference storage capacitor 809a. When the voltage on capacitor
805f exceeds that on capacitor 809a, the output signal from
comparator 807 will go to a low level. This low-level signal
transmitted via resistor 807a and limited by diode 807b, resets D
flip-flop 803. When D flip-flop 803 is reset, its output signal
goes low-level, clearing flip-flop 804 and thus terminating double
injection.
When flip-flop 803 was initially set by a signal from trigger
comparator 802, the signal on the Q output lead of flip-flop 803
went to a high level. That high-level signal, passed through
resistor 810b to transistor switch 810, turned off transistor
switch 810, thus cutting off the current through collector resistor
810a. This caused the voltage at the gate of FET switch 309 to
fall, thus interrupting its source-to-drain current conduction.
Before the double inject was activated, operational amplifier 808
kept capacitor 809a charged to a potential representing the
difference between V.sub.AMP (the absolute manifold pressure) and
the maximum possible V.sub.AMP. This potential thus represented the
maximum differential injection time that could be expected upon
application of full throttle. At the beginning of the double inject
sequence, switch 809 is opened and thus this particular
differential injection time is stored as a voltage on capacitor
809a. At the same time, capacitor 805f begins charging in a
positive direction toward the potential on capacitor 809a. When
comparator 807 sees the potentials on these two capacitors as
equal, the double inject sequence is terminated by resetting
flip-flop 803. Resetting flip-flop 803 turns on transistor 810 via
resistor 810b thus turning on switch 809 and updating the charge on
capacitor 809a to reflect the difference between the new V.sub.AMP
and the maximum V.sub.AMP.
It should be noted that the overall double inject time can be
scaled by varying the transfer function of the voltage-to-current
converter 805 and/or the gain of amplifier circuitry 808.
It should also be noted that there are throttle position sensors
associated with the throttle linkage. The primary throttle position
sensor can be either an analog or digital sensor representing true
throttle position. The output lead from this sensor can be
connected to either a pair of analog or digital comparators,
respectively, to indicate the signal levels corresponding to fully
closed throttle and wide open throttle. There is also the option of
mounting one or more sensors directly on the throttle linkage to
measure the throttle position.
EXHAUST GAS ANALYSIS, FUEL PUMP AND TURN-ON RESET CIRCUITS
FIG. 9 shows the exhaust gas analysis circuitry, the circuitry
controlling the high pressure fuel pump and the turn-on reset
circuitry.
The turn-on reset circuitry synchronizes the system when the engine
is being started. When a positive supply voltage is applied to the
system, capacitor 911b charges toward this supply voltage through
resistor 911a.
Schmidt trigger 912 is activated through resistor 911d and diode
911c when the charge on capacitor 911b is sufficient to break down
zener diode 911c. Schmidt trigger 912 is of conventional design and
will not be discussed. Upon activation of Schmidt trigger 912, the
output signal from transistor 912e goes high, thus removing the
turn-on reset signal on line 621 as fed to RS flip-flops 614 and
615 (FIG. 6). This resets flip-flops 614 and 615.
The output signal of Schmidt trigger 912 is also fed through
resistor 910a to transistor 910. The sense of the signal on the
collector of transistor 910 is the same as that on line 621, for
example, low during turn-on reset. The length of the turn-on reset
period is selected to be in the range of one-quarter to four
seconds and is the period from system turn-on until the signal on
lead 621 goes to a high level.
Fuel pump control 110 comprises flip-flops 903, 904, gates 905,
906, 907, transistors 909, 910 and output driver circuitry 908. It
is desirable to limit the output of the fuel pump slightly more
than the fuel quantity demanded by the engine. This is accomplished
by varying the duty cycle of the power applied to the electric fuel
pump in response to the instantaneous fuel demand. This engine
demand is measured by combining a submultiple of the injection time
with the speed of the engine.
Signals from data decode 100 representing every 90.degree. pulse
from the crankshaft position transducer on lead 535a (FIG. 5c) are
fed to the "set direct" input of flip-flop 903 (labeled CK). These
signals drive the Q output of flip-flop 903 high thus toggling
flip-flop 904. Simultaneously, the signal level on the Q output of
flip-flop 903 goes low. The Q outputs of flip-flops 903 and 904
pass through NOR gate 905 and NAND gate 906. NAND gate 906 is
enabled by a minimum oil pressure signal arriving from an oil
pressure transducer on line 900c indicating satisfactory oil
pressure in the engine. The output of NAND gate 906 is then fed
through NAND gate 907 into output driver circuit 908 containing
turn-on transistor 908b and power transistor 908c. Current drawn by
transistor 908c turns on the fuel pump via line 900d. The Q output
of toggle flip-flop 904 is also fed into NOR gate 905. Every
90.degree. pulse from data decode 100 on line 535a (FIG. 5c) will
turn on the fuel pump provided there is minimum oil pressure.
Should the oil pressure fail for any reason such as the engine
stopping, then the fuel pump will be turned off. The duration of
the pulse from the flip-flop 903 will be determined by the time
that it takes the pulse group which activates NAND gate 505 of data
decode 100 to be shifted by computing oscillator 30 through shift
registers 530-1 and 530-2. When the first pulse in this group
arrives at line 530-2a it will clock a logical zero through
flip-flop 903. This will drive the signal on the Q output lead of
flip-flop 903 high, terminating the drive to the fuel pump. The
output pulse from flip-flop 903, as previously mentioned, toggle
flip-flop 904. Therefore, the Q output of flip-flop 904 will be low
during the interval between every other pulse being generated by
flip-flop 903. (The Q output signal from flip-flop 904 varies at
1/2 the frequency of the Q output signal from flip-flop 903.) This
low-level signal will then be sent through NOR gate 905, NAND gate
906 and NOR gate 907 to fuel pump drive circuit 908. The result
(assuming adequate oil pressure) is that the fuel pump will be on
at least 50% of the time and the width of the Q pulse from
flip-flop 903 will then add to this 50% bringing the on-time of the
fuel pump up to a maximum approaching the 100% at long injection
time and high engine speed. Other inputs to the fuel pump drive
circuit 908 are a crank signal on line 336 transmitted through
resistor 909a to transistor switch 909. The high-level crank signal
holds the fuel pump on continuously, overriding signals from
flip-flops 903 and 904. Also, upon initial application of power to
the system, when the TORS signal on line 621 is low-level,
transistor 910 will turn on thus turning on the fuel pump. This
will assure that during the time immediately after system turn on,
the fuel pump will also be held on to prime the fueling system.
Fuel pump drive circuit 908 is a Darlington pair. Resistor 908d and
diode 913a protect transistor 908c from transients generated by the
inductive properties of the fuel pump 913 during the turn-off of
pump drive 908.
Next to be described will be the exhaust gas analysis circuit.
Amplified signals from the various pollutant sensors 900 (FIG. 9)
enter the system on lines 901a through 901c. These signals are
scaled by resistors 902 selected to represent their relative
weighting factors. At the node connecting resistors 902a through
902c to the source terminal of FET transistor 903, a signal is
developed which represents the relative pollution level of the
engine exhaust, or whether the mixture being delivered is richer or
leaner than required. Transistor 903 is on only when the system is
running and is disabled by the turn-on reset signal. The weighted
signal representing the pollution output of the engine passes
through transistor switch 903 to integrating capacitor 904a.
Capacitor 904a in combination with resistors 902 form a long-term
integrator. The voltage developed across capacitor 904a is
amplified by amplifier 904 and fed through resistor 904d to line
347 (FIG. 3) labeled CEGA.
The CEGA signal has a direct effect upon the over-all mixture fed
to the engine by affecting the -TEMP signal (FIGS. 2 and 3). If the
pollution output is excessive as evidenced by oxides of nitrogen or
carbon monoxide in the exhaust, for instance, then the mixture is
changed to reduce these pollutants to an acceptable figure.
Corresponding corrections are made in response to HC and CO
polluting gasses. Typically, these corrections are made over a
period on the order of from 15 minutes to several hours. This is
done so that transient operations of the engine, which may create
slightly excess pollution, will have no overall effect on the
average mixture ratio. Other embodiments of the exhaust gas
analysis system include separate integrating circuits for each
pollutant and limiting circuitry such that if the exhaust gas
mixture, as sensed by any one of the pollutant detectors exceeds a
preset norm by a given amount, then a more rapid correction process
can be taken. If the pollutant output exceeds a second preset
level, a signal will indicate this and the system can be checked
for excessive pollutant output or system failure.
* * * * *