U.S. patent number 3,871,338 [Application Number 05/390,013] was granted by the patent office on 1975-03-18 for method and apparatus to reduce noxious components in the exhaust emissions of internal combustion engines.
This patent grant is currently assigned to Robert Bosch GmbH. Invention is credited to Gerhard Hartmann, Harald Kizler, Peter Schmidt.
United States Patent |
3,871,338 |
Schmidt , et al. |
March 18, 1975 |
METHOD AND APPARATUS TO REDUCE NOXIOUS COMPONENTS IN THE EXHAUST
EMISSIONS OF INTERNAL COMBUSTION ENGINES
Abstract
To provide for rapid and effective control upon persistent
deviation of control signals, derived upon integration of sensed
output signals representative of exhaust emission, beyond a
predetermined time, the base setting of a fuel injection system, or
a carburetor system, is changed in a direction to counteract the
deviation, for example by extending (or reducing) fuel injection
time beyond the range of change within the fuel injection circuit,
for example by additionally modifying the charge level of a storage
capacitor; or, in a carburetor system, by controlling bypass of
air, or the setting of a fixed jet.
Inventors: |
Schmidt; Peter
(Schwieberdingen, DT), Kizler; Harald
(Schwieberdingen, DT), Hartmann; Gerhard (Hofingen,
DT) |
Assignee: |
Robert Bosch GmbH (Stuttgart,
DT)
|
Family
ID: |
5857658 |
Appl.
No.: |
05/390,013 |
Filed: |
August 20, 1973 |
Foreign Application Priority Data
|
|
|
|
|
Sep 28, 1972 [DT] |
|
|
2247656 |
|
Current U.S.
Class: |
123/696; 60/276;
60/285 |
Current CPC
Class: |
F02D
41/148 (20130101); F02D 41/1456 (20130101) |
Current International
Class: |
F02D
41/14 (20060101); F02b 003/00 () |
Field of
Search: |
;123/32EA
;60/276,285,274,39.28 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Myhre; Charles J.
Assistant Examiner: Cox; Ronald B.
Attorney, Agent or Firm: Flynn & Frishauf
Claims
We claim:
1. Method to reduce the noxious components in the exhaust emission
of internal combustion engines having an air-fuel proportion
adjustment means, and including an integrating controller carrying
out the step of regulating the mass-ratio of air and fuel being
applied to the internal combustion engine, utilizing the steps
of
sensing the composition of exhaust emission and derviving a sensing
signal;
integrating the sensing signal and derving a fuel-air ratio control
signal;
sensing an operating parameter, or condition of the engine;
and wherein the improvement comprises the steps of
changing the control range of the control of air-fuel proportion as
a function of change of the sensed operating parameter beyond a
predetermined limit.
2. Method according to claim 1 wherein the apparatus includes a
fuel-air mass control means;
wherein the step of changing the control range of the air-fuel
proportion comprises the step of changing the base setting of said
control means.
3. Method according to claim 2 wherein said control means comprises
a fuel injection apparatus;
and said step of changing the control range comprises changing the
base setting affecting the operating time of the injection system,
during which fuel is injected.
4. Method according to claim 2 wherein the control means comprises
a carburetor system supplying a predetermined amount of fuel for a
predetermined amount of air flow to the induction duct of the
internal combustion engine, wherein said step of changing the
control range of the air-fuel proportion comprises changing the
base setting of at least one of: air flow; fuel flow;
of the carburetor system.
5. Method according to claim 1 wherein the step of sensing an
operating parameter of the engine comprises sensing a threshold
level corresponding to said limit of the integrated fuel-air ratio
control signal;
and the step of changing the control range of the proportion of air
and fuel comprises the step of abruptly changing the operating
range in a positive, or negative direction if an upper, or lower
sensed threshold level is exceeded.
6. Apparatus to reduce the noxious components in the exhaust
emission of internal combustion engines comprising
means controlling the mass ratio of air and fuel being supplied to
the internal combustion engine;
means including an exhaust gas sensor (22)B sensing operating
parameters of the engine, including the compositon of exhaust gases
therefrom;
and means (24) including an integrator (47,50) connected to and
controlled by said exhaust gas sensor and providing an integrated
output signal representative of deviation of the signal from the
exhaust gas sensor from a predetermined value, said output signal
being applied to said mass ratio control means to affect the
proportion of air and fuel being applied to the internal combustion
engine to re-establish exhaust gas emission from the engine
resulting in a predetermined output signal;
the improvement wherein the engine operating parameter or condition
sensing means includes limit sensing means (105,205) connected to
said means controlling the mass ratio of air-fuel supplied to the
internal combustion engine to change the base setting thereof and
thus change the control range in which said integrated output
signal becomes effective when the integrated signal reaches a
predetermined limit as sensed by said limited sensing means.
7. Apparatus according to claim 6 wherein said limit sensing means
comprises a threshold switch (105,205), having upper and lower
threshold sensing levels and providing an output signal to change
the base setting of said mass ratio control means, in either
direction, if the upper, or lower threshold is exceeded.
8. Apparatus according to claim 7 wherein the means controlling the
mass ratio of air and fuel supplied to the engine comprises a fuel
injection system;
and said threshold switch changes a circuit parameter within the
fuel injection system in the circuit thereof affecting the duration
of injection time of fuel, in a direction to lengthen, or to
shorten said injection time to extend the control range of said
fuel injection system.
9. Apparatus according to claim 7 wherein said means controlling
the mass ratio of air and fuel being supplied to the engine
comprises a carburetor system;
electrical-mechanical transducer means are provided, said
transducer means having an output controlling the base setting of
at least one of: air flow; fuel flow
of the carburetor system, said threshold switch energizing said
transducer, to increase, or decrease the base setting of a base
quantity of air, or fuel, respectively, upon response of the
threshold switch, indicative that the normal control range of the
carburetor system should be changed.
10. Apparatus according to claim 6 wherein said means sensing an
operating parameter of the engine comprises means responsive to
changes in the exhaust gas composition, from a predetermined value,
over a time.
Description
CROSS REFERENCE TO RELATED PATENT AND APPLICATIONS
U.S. Pat. No. 3,483,851, Reichardt, Dec. 16, 1969.
The present invention relates to method and apparatus to reduce the
noxious components in the exhaust emmission of internal combustion
engines, and more particularly of automotive internal combustion
engines, in which a controller is provided which has integrating
characteristics, to control the proportion of air and fuel being
supplied to the internal combustion engine.
It has previously been proposed to reduce the noxious components in
the exhaust emmission of internal combustion engines by sensing the
composition of the exhaust gas by means of a sensor, located to be
exposed to the exhaust gases, and then to control the proportion of
air and fuel in such a manner that the proportion is just below the
stoichiometric value. This proportion of fuel to air is also
referred to as the air number .lambda. . When .lambda. = 1.0, the
mixture of air and fuel is exactly at the stoichiometric value
(approximately 14.4:1). Controlling the air number .lambda. to a
slightly lower value, for example .lambda. = 0.98 results in
emission of exhaust gases in which the carbon monoxide and
hydrocarbon components have a low value. It is necessary, however,
that the value of .lambda. be controlled to have only very small
tolerance, so that the exhaust emission does not exceed permissible
limits. Controlling the tolerance of .lambda. , in the previously
proposed apparatus, and in accordance with previously proposed
methods is done by controlling the voltages at the output of a
control amplifier by means of a proportionality element, such as a
potentiometer, or the like. So controlling the tolerance results in
a limitation of the entire range of control by the supply or
control signals for the device.
From time to time, and under certain operating condiions of the
internal combustion engines, it is necessary to expand the range of
control. For example, if the internal combustion engine is started
while hot, or to protect a catalytic reactor in the exhaust system
if ignition partly fails in the engine, it is necessary to have a
wider range of limits between which the controller may operate.
It is an object of the present invention to provide apparatus and a
method to reduce noxious components in the exhaust emission of
internal combustion engines, and in which the control limits, or
the control range of the controller is expanded in a simple, and
effective manner, to better control the air number .lambda. . The
apparatus to carry out the method should, further, be sturdy and
suitable for the rough and widely varying conditions which arise in
automotive applications, and the apparatus should utilize as much
as possible of already available and existing devices and apparatus
in usual automotive engines, or automotive vehicles.
SUBJECT MATTER OF THE PRESENT INVENTION
Briefly, the control range of the control apparatus is changed in
dependence on at least one operating parameter of the internal
combustion engine, and the base setting of the air-fuel supply
device is accordingly changed in one direction, or the other. The
air-fuel supply device may, for example, be a fuel injection system
and changing the operating range thereof includes changing fuel
injection time; or, for instance, it may be a carburetor, and
changing the air-fuel mixture may involve adding additional air, or
additional fuel through a separate jet, or by changing the setting
of a jet, or opening or closing an air bypass, more or less.
In accordance with a feature of the invention, a threshold switch
is provided which responds when a certain operating parameter is
exceeded, the threshold switch upon response, changing the base
setting of the air-fuel supply device to the internal combustion
engine.
The invention will be described by way of example with reference to
the accompanying drawings, wherein:
FIG. 1 is a highly schematic diagram illustrating the system with
which the invention is used;
FIG. 2 is a diagram illustrating the relationship of output voltage
with respect to air number .lambda. of an exhaust gas sensor;
FIG. 3 is a schematic abbreviated circuit diagram of a control
amplifier;
FIG. 4 is a fragmentary, abbreviated circuit diagram of a
transistor fuel injection circuit;
FIG. 5 is a circuit diagram of apparatus to change the control
range of a fuel injection control device;
FIG. 6 is a series of graphs illustrating the operation of the
circuit of FIGs. 3, 4, and 5; and
FIG. 7 is a highly schematic representation of the fuel and air
supply to an internal combustion engine, utilizing a carburetion
system, and adjustment of the system in accordance with the
invention.
For purposes of illustration, the invention will be described in
connection with a four-cylinder engine 11 (FIG. 1) to which air is
supplied over an inlet air filter 12 through an induction duct 13.
Throttle 15 is located in duct 13, the throttle position being
controllable by the accelerator pedal. An air mass flow meter 14 is
located in duct 13 between filter 12 and throttle 15, which has an
electrical output line B. The mass air flow meter may be a
spring-biased disk. One, or more fuel injection valves 16 are
associated with the internal combustion engine 11; preferably, a
fuel injection valve 16 is provided for each of the cylinders,
immediately adjacent the inlet valves thereof, and injecting fuel
into the inlet manifold adjacent the inlet valves. Only one of the
injection valves 16 is shown for simplicity. A fuel supply line 17
provides fuel to the injection valves.
An exhaust manifold 18 is connected to the exhaust side of the
engine, which terminates in a thermo reactor 19, the output of
which is connected to a catalytic reactor 20. The exhaust system
itself is connected to the output of catalytic reactor 20, forming
an exhaust pipe 21 which is connected to the usual muffler, and the
remaining portions of the exhaust system, which can be standard
(not shown). The thermo reactor 19 and the catalytic reactor 20
provide for after-treatment of the exhaust gases.
An exhaust gas sensor 22 is connected in the wall of the connection
pipe from the thermo reactor 19 to the catalytic reactor 20. A
tachometer generator 23 is connected to the crankshaft of the
engine 11 to provide control pulses in synchronism with rotation of
the engine for a transistorized fuel injection controller 25. The
transistorized circuit 25 provides pulses which have pulse
durations determining the opening time of the injection valve 16.
The pulse duration is influenced by the electrical data derived
from the air mass flow meter 14 and the control amplifier 24. The
outputs of control amplifier 24 and of the mass air flow meter 14
are connected to the inputs A, B of a transistor circuit 25, which
form command input terminals. Injection valve 16 is operated by
means of a solenoid, connected in the output of the circuit 25.
The diagram of FIG. 2 shows the output voltage from sensor 22 with
respect to air number .lambda. . As can be clearly seen, the value
of the output signal changes abruptly between two terminal, or
saturation values at about a value of .lambda. = 1.0. When the
mixture is lean, .lambda.>1.0; a rich mixture has a
.lambda.<1.0.
The output signal from sensor 22 is applied to the control
amplifier 24, shown in detail in FIG. 3, to control the relative
quantity of air and fuel being supplied to the engine. Control
amplifier 24 (FIG. 3) includes a first operational amplifier 40
which provides proportional amplification of the output signal of
sensor 22, and a second operational amplifier 47, connected as an
integral controller. The oxygen sensor 22 is connected over input
resistor 41 to the inverting input of operational amplifier 40,
and, with its other terminal, to ground or chassis. The
non-inverting input of operational amplifier 40 is connected over
input resistor 42 to the tap point of a voltage divider formed of
resistors 38, 39. A feedback resistor 44 is connected between the
output of the operational amplifier and the inverting input, the
value of the feedback resistor determining the amplification
factor. The output of the operational amplifier 40 is further
connected to a resistor 43 and to a positive supply bus 52.
The output of the operational amplifier 40 is connected over input
resistor 48 to the inverting input of operational amplifier 47. The
non-inverting input of operational amplifier 47 is connected over
resistor 49 to the tap of the voltage divider formed of two
resistors 45, 46. The tap point is additionally connected over a
controllable resistor with an input terminal 54. Operational
amplifier 47 has a feedback circuit which includes capacitor 50
acting as integrating capacitor. The output of operational
amplifier 47 is connected over resistor 121 to output terminal A,
and further to an output terminal C. A supply resistor 51 connects
to positive bus 52.
The fuel injection circuit, in its simplest form, essentially
includes a switching stage 55 (FIG. 4) which may, for example, be a
monostable multivibrator, controlled by pulses from tachometer
generator 23, which preferably is a switch operated by a cam
rotating in synchronism with the cam shaft, or crankshaft of the
engine. Switch 23 is controlled to close, synchronously with
crankshaft rotation, with such frequency that each injection valve
16 has applied thereto an injection pulse upon each other full
rotation of the crankshaft. Correction input B is provided which
controls the pulse duration of the monostable multivibrator (MMV)
55 in dependence on the mass air flow, as measured by air flow
meter 14 (FIG. 1), so that when the air quantity is large, more
fuel will be injected, and to maintain the air number .lambda. at a
constant value. The output of MMV 55 is connected to a pulse
extender stage which includes a storage capacitor 60. Storage
capacitor 60 has one of its terminals connected to the collector of
a transistor 58, the emitter of which is connected over resistor 59
to positive bus 52. Its base is connected to the output of the MMV
55. The base of transistor 58 is further connected to the input
terminal A and to chassis or ground bus 152 over resistor 57. Input
terminal A of FIG. 4 and output terminal A of FIG. 3 are
interconnected.
The second terminal of storage capacitor 60 is connected to the
collector of a discharge transistor 61, which has its base
connected to a tap point of a voltage divider formed by resistor
62, 63. Resistor 63 is a variable resistor. The emitter of the
discharge transistor 61 is connected over a resistor 64 with
positive bus 52. The collector of discharge transistor 61 is
connected over a diode 65 to the base of an inverter transistor 67.
Diode 65 is so poled that the collector current of the discharge
transistor 61 is passed thereby. The base of the inverter
transistor 67 is connected to chassis over resistor 66. The
collector of inverter transistor 67 is connected to the positive
bus 52 over collector resistor 68.
The output of MMV 55 and of the collector of inverter transistor 67
is connected, respectively, with two inputs of an OR gate 56 which
is connected ahead of a switching transistor 69. Switching
transistor 69 controls solenoid 70, which operates the injection
valve 16.
Operation: the basic operation of the fuel injection system of FIG.
4 is well known, see the cross reference U.S. Pat. No. 3,483,851
Reichardt. Only so much of the operation will be described as is
necessary for an understanding of the present invention and is not
already obvious from prior publications.
The duration of the output pulses from MMV 55 depends on the mass
air flow through the induction duct 13. The output pulse of MMV 55
is applied directly to OR gate 56 and then to the switching
amplifier 69. The switching amplifier will be energized, in turn
energizing solenoid 70 and opening the fuel injection valve to
inject fuel. The pulse applied to the OR gate 56 is extended by the
extension pulse derived from the extension stage formed of
transistors 58, 61, and the inverting transistor 67. The duration
of the extension pulse is proportional to the duration of the
initial pulse, that is, the duration of the output pulse of MMV 55.
Additionally, the duration of the extension pulse is modified by
other parameters, for example by the variable resistor 63 which,
for example, is a negative temperature coefficient resistor,
located in temperature-sensing relationship to the engine and
measuring engine temperature. Additionally, the duration of the
extension pulse can be modified by other parameters, for example by
parameters applied in the form of control voltages connected to
terminal A. The voltage applied to terminal A influences the
charging current to the capacitor 60, over transistor 58, while the
MMV 55 provides its output pulse. Thus, the level of voltage rise,
or the level of voltage change which is transferred at the end of
the output pulse of the MMV 55 over capacitor 60 is influenced
thereby. The resistor 63, however, influences the discharge current
of capacitor 60, and thus the time after inverter transistor 67
again becomes conductive, having previously been blocked.
The base electrodes of the two transistors 58, 61 can have other
correction potentials applied thereto, for example to obtain
enrichment of the fuel-air mixture during warm-up of the engine,
upon starting, or the like. The inverter transistor 67 is
conductive in quiescent state. Transistor 67 can be blocked if a
negative pulse is applied from capacitor 60. The utilization signal
on the collector of transistor 67, therefore, just like the output
signal of the MMV 55 is a 1-signal, that is, it has the value of
the voltage at positive bus 52. OR gate 56 thus provides a 1-signal
at its output when one of its inputs has a 1-signal. The output
pulse of the pulse extension stage thus follows the output pulse of
the MMV 55 so that the output from OR gate 56 will be one
continuous pulse, the duration of which is determined by the pulse
duration from MMV 55, and the pulse duration of the extension
pulse.
Let it be assumed that the duration of the output pulse of the
circuit 25 (FIG. 1; FIG. 4) is somewhat too long. Thus, the amount
of fuel injected is excessive, and the mixture applied to the
engine becomes too rich. Air number .lambda. will be less than 1,
and the output voltage of sensor 22 will be high.
The output voltage of sensor 22 is amplified in operation amplifier
40 (FIG. 3) which, being connected as an inverter amplifier,
provides a negative value of output voltage which is connected over
input resistor 48 to the inverting input of operational amplifier
47. This operational amplifier is connected as an integrating
amplifier, and thus integrates (at negative input voltage to its
inverting input) in positive direction The voltage at terminal A
slowly changes in positive direction. As the voltage at terminal A
changes towards a positive point, the charging current for the
capacitor 60 (FIG. 4) flowing through transistor 58 becomes
smaller. This decreases the pulse duration of the extension pulse
from the pulse extension stage, so that the overall pulse available
at the output of the OR gate 56 becomes shorter, since a shorter
extension pulse is added to the base pulse from MMV 55. Solenoid 70
is thus energized for a shorter period of time and less fuel is
injected. The mixture becomes leaner until an air number .lambda. =
1.0 is obtained. At that point, the sensor 22 switches abruptly, to
a low output voltage; operational amplifier 47 will now integrate
in reverse direction, and the above described cycle will repeat, in
reverse direction, so that the duration of the output pulses from
the pulse extension stage will increase.
The output voltage of sensor 22 thus corrects deviations of the air
number .lambda. from the value .lambda. = 1.0.
Under certain operating conditions, for example upon starting the
engine when it is warm, or, for example to protect the catalyst if
the ignition partly fails, then it has been found that the control
range of the apparatus as described is not sufficient to
effectively control the air number .lambda. completely.
Referring next to FIG. 6: the normal operating range of the
controller described so far is within the limits indicated by the
heavy lines 80, 81. The output voltage of the controller is
indicated by line 82. As can be seen from FIG. 6, the output
voltage of the control amplifier changes in dependence on the
output voltage of the sensor 22, that is, it rises or drops. The
portion of the curve indicated at 83 shows rapid rise of the output
voltage of the controller. The rise in voltage is, however, limited
by the operating voltage of the control amplifier. Under such
operating conditions it has been found desirable to change the
entire operating range, so that the operating range will shift to
that indicated between lines 80 and 84. This shift in the control
range can be obtained only when the input terminal A of the
switching circuit of FIG. 4 has an electrical signal applied
thereto in such a manner that the base voltae of the transistor 58
is shifted in a direction to extend the opening times of the fuel
injection valves, as commanded by the transistor circuit of FIG.
4.
The control amplifier can operate normally in the control range
determined by the limits of lines 80 and 84, as can be seen in
curve portion 86. A shift in the control range in the other
direction is also possible. Thus, the pulse duration can be
shortened, basically, by an electrical signal at input terminal A
of FIG. 4 in a direction to change the control range, with equal
output voltage of the amplifier itself, by a predetermined value,
so that the injection periods will be, inherently, shortened. Thus,
for example, the control range can be shifted to fall between lines
81 and 84' .
FIG. 5 is a circuit diagram of the circuit to change the correction
signal applied to the base of transistor 58 of the circuit of FIG.
4, if operating parameters or conditions of the engine indicate
that it is desirable to shift the operating range. The circuit of
FIG. 5 includes a first operational amplifier 105, connected as a
threshold switch. The output of operational amplifier 105 is
connected, over resistor 107, to a positive bus 120. Further, a
feedback resistor 106 connects to the non-inverting input of the
operational amplifier 105 which, further, is connected to a control
terminal C of controller 24 (FIG. 3) that is, directly to the
output of operational amplifier 47 (FIG. 3). The inverting input of
operational amplifier 105 is connected, over an input resistor 103,
to the tap point of a voltage divider formed of resistors 101, 102,
connected between positive bus 120 and chassis or ground connection
152. The output of operational amplifier 105 is connected over
resistor 108 to the base of a first transistor 111, the emitter of
which is connected to negative bus 152. A resistor 109 is connected
across the base-emitter junction of transistor 111. The collector
of transistor 111 is connected over collector resistor 110 to
positive bus 120, and further, over a coupling resistor 112 to the
base of a transistor 114, the emitter of which is connected to
positive bus 120, in parallel to a base-emitter resistor 113. The
collector of transistor 114 is connected over coupling resistor 115
and diode 122 to terminal A (FIG. 4), that is, to the base of
transistor 58 of the transistor circuit 25 (FIG. 4).
A second threshold switch is connected similarly to the just
described threshold switch, and in parallel thereto, the input of
which is likewise connected to output terminal C of the control
amplifier (FIG. 3). Similar elements have been given similar
reference numerals, incremented by 100. The major difference
between the circuits is that the final transistor 214 of the
parallel circuit is of the reverse conductivity type (npn) to that
of transistor 114, and that, therefore, the base-emitter resistor
is connected to chassis bus 152, rather than to positive bus 120.
The output from the collector resistor 215 connects over diode 123,
which is reversely poled with respect to diode 122 to terminal
A.
Operation of circuit of FIG. 5, with reference also to FIG. 6: the
control voltage derived from control amplifier 24 (FIG. 3) normally
has the voltage range falling between lines 80, 81 (FIG. 6), for
example having the wave shape indicated by the curve 82. Under
certain operating conditions, however, this control range is not
sufficient. When the output voltage of control amplifier 24 exceeds
a switching threshold indicated by line 88, then a signal is
applied over one of the threshold switches 105, 205, to the base of
the transistor 58 (FIG. 4) which changes the base voltage thereof,
and thus changes the operating range, or control range. When the
voltage drops below a certain threshold, for example indicated by
broken line 85 (FIG. 6) one of the threshold switches 105, 205 will
change back to its initial state, and the base potential of the
transistor 58 will again fall within the original value which
determines the normal control range. The relationships are similar
when the output voltage of control amplifier 24 falls below a
threshold, as indicated for example by broken line 87. The other
one of the threshold switches 105, 205, respectively, will then
change over in order to change the fixed base potential on
transistor 58 (FIG. 4) in opposite direction, in order to change
the control range downwardly. Thus, the base, or level of extension
of the pulse from MMV 58 is changed by changing the charge time
taken to charge capacitor 60, and thereby changing the duration of
opening time of the fuel injection valve to shorten this injection
time. When the voltage reaches the value indicated by chain dotted
line 89, one of the two threshold switches 105, 205 will change
back to its output state, and the normal base voltage of transistor
58 will again revert to its normal value, and the fuel injection
system will operate in its normal range.
As can be seen from FIG. 6, the range of control is substantially
extended. Curve 82 shows operation within a normal range, but curve
section 83 shows that the mixture is much too lean and requires
rapid enrichment. Since this requirement of rapid enrichment
exceeds the threshold level 88, the circuit of FIG. 5 will become
effective and the control range will be shifted upwardly and the
resultant control curve is seen at 86. The rapid enrichment caused
an overshoot, however, and rapid dropping is commanded, and the
threshold level indicated by broken line 85 will be quickly
reached, the circuit switching then to normal level, the control
being indicated by curve 82' , within its normal range. If too much
fuel is still supplied, and the time should be shortened so that
the curve 82' drops below the threshold limit given by chain dotten
curve 87, the level will shift and the control will then be
effected as seen by curve 86' , which will persist until the upper
threshold level is reached at chain dotted line 89, to re-establish
operation within the normal control range, as seen by curve 84"
.
The extent of shift of the control ranges is indicated by broken
line 88' and chain dotted line 87' , that is, from threshold limit
88 to limit 84; from lower threshold limit 85 to 88' (which is a
similar jump); and from lower limit 87 to 84' and from the higher
limit in the lower range, 89 to 87' .
Various changes and modifications may be made within the scope of
the inventive concept.
FIG. 7 illustrates the system as applied to a carburetor fuel
system, in which the auxiliary control of air is given by a bypass.
Fuel induction tube 713 corresponds to air inlet pipe 13, and
applies air to the intake manifold of an internal combustion
engine. Fuel is supplied over line 717 to a carburetor 716. A
bypass 720 bypasses air around the Venturi of the carburator
system, which is indicated only schematically. The bypass 720
includes a bypass throttle or flap valve 721 which, for normal
setting of the carburetor, is, for example, half open. It is
maintained in this position by a set spring, not shown. Fuel flap
valve 721 is mechanically connected, as schematically indicated by
chain dotted line 722 to a setting disk 723, which can be deflected
from its center position, in either direction, backwards or
forwards, by means of a solenoid operated link. The solenoid 724 is
energized, in polarized direction, to move the link 725 to the
right, or to the left, depending on the polarity of the output
signal available from terminal A. Suitable amplification, power,
and matching circuits (not shown) may be interposed between
terminal A and solenoid 24. Of course, other systems may be used,
such as a bi-directional motor, driven directly or indirectly from
the output terminal A, or the like. Similarly, rather than
controlling the air flow in order to control the proportion of air
to fuel, the rotating disk 723 can be connected to a setting or
adjustment screw within the carburetor 716 to control the fuel flow
through the carburetor to the induction duct 713, independently of
other carburetor settings, for example by additionally modifying
the setting of the idle jet thereof, when the normal control range
of the system is being exceeded.
* * * * *