U.S. patent number 3,782,347 [Application Number 05/259,254] was granted by the patent office on 1974-01-01 for method and apparatus to reduce noxious components in the exhaust gases of internal combustion engines.
This patent grant is currently assigned to Robert Bosch GmbH. Invention is credited to Harald Kizler, Peter Jurgen Schmidt.
United States Patent |
3,782,347 |
Schmidt , et al. |
January 1, 1974 |
METHOD AND APPARATUS TO REDUCE NOXIOUS COMPONENTS IN THE EXHAUST
GASES OF INTERNAL COMBUSTION ENGINES
Abstract
The composition of exhaust gases from internal combustion engine
is sensed, particularly the oxygen component thereof, and a sensed
signal is derived, which is applied to a threshold detector, which
triggers whenever the sensed signal passes a certain threshold
value. The trigger signal controls and integrating controller to
commence integrating, the integrating controller providing an
output signal which is applied to set the air-fuel ratio such that
the air number lambda is constantly controlled to be about 1. If
integration by the integrating controller persists for a period of
time in excess of a predetermined lapsed time, as determined by a
pulse source controlled by speed of the engine, the integrating
rate of the integrating controller is changed to provide for more
rapid response when large changes have to be compensated.
Inventors: |
Schmidt; Peter Jurgen
(Schwieberdingen, DT), Kizler; Harald
(Schwieberdingen, DT) |
Assignee: |
Robert Bosch GmbH
(Gerlingen-Schillerhohe, DT)
|
Family
ID: |
5835604 |
Appl.
No.: |
05/259,254 |
Filed: |
June 2, 1972 |
Foreign Application Priority Data
|
|
|
|
|
Feb 10, 1972 [DT] |
|
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P 22 06 276.6 |
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Current U.S.
Class: |
123/687; 60/276;
123/696; 60/285 |
Current CPC
Class: |
F02D
41/1482 (20130101); F02D 41/1474 (20130101); F02D
9/00 (20130101); F02D 2700/09 (20130101); F02D
2700/0241 (20130101) |
Current International
Class: |
F02D
41/14 (20060101); F02D 9/00 (20060101); F02d
005/02 () |
Field of
Search: |
;123/14MC,119R
;60/39.28T,276 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Goodridge; Laurence M.
Attorney, Agent or Firm: Flynn & Frishauf
Parent Case Text
CROSS REFERENCE TO RELATED PATENTS AND APPLICATIONS:
U.s. pat. No. 3,483,851, Reichardt, Dec. 16, 1969;
U.s. ser. No. 259,157, filed June 2, 1972, Schmidt et al.;
U.s. ser. No. 259,134, filed June 2, 1972, Topp et al.;
U.s. ser. No. 265,547, filed June 23, 1972, Wahl et al.;
U.s. ser. No. 298,108, filed Oct. 16, 1972, Wahl et al. --
All assigned to the assignee of the present application.
Claims
We claim:
1. Method to reduce noxious components in the exhaust gases of
internal combustion engine comprising
sensing the composition of the exhaust gases from the internal
combustion engine and deriving an exhaust composition
representative sensed signal;
analyzing the sensed exhaust composition signal to determine
whether a characteristic thereof falls above or below a
predetermined limit value;
integrating a representation of the sensed exhaust composition
signal in a direction determined by whether the analyzed signal is
above or below said limit value;
measuring the time during which the integrating step proceeds in a
given direction;
changing the integration rate if the integration step has extended
beyond a predetermined time period;
and controlling the composition of the air-fuel mixture being
applied to the internal combustion engine in accordance with said
integrated sensed signal.
2. Method according to claim 1, wherein the time measuring step
comprises
setting a time element at a datum level;
determining elapsed time by deviation of said element from the
datum level and deriving a control signal after lapse of said
predetermined period of time upon said deviation;
and utilizing said control signal to control the change of
integration rate during said integration step.
3. Apparatus to reduce noxious components in the exhaust gases of
internal combustion engines comprising
means (13) sensing the composition of the exhaust gases from the
internal combustion engine and deriving an exhaust composition
representative sensed signal;
a first threshold detector (11) responding to said sensed signal
and providing an output trigger signal when the sensed signal
changes between levels above and below a predetermined threshold
level; and
an integrating controller (10) connected to control the relative
proportion of air and fuel being applied to the internal combustion
engine, the threshold detector having its output trigger signal
connected to the integrating controller to change the direction of
integration of the integrating controller,
a timing element (14, 18) triggered by the output trigger signal
from the threshold detector and providing a timing output signal
indicative of a predetermined time lapse, said timing signal being
connected to the integrating controller to change the control
characteristics of said controller after said predetermined time
has elapsed;
said integrating controller providing an integrated output signal
for control of said relative proportion of air and fuel in the
mixture which is applied to the internal combustion engine.
4. Apparatus according to claim 3, wherein the integrating
controller has a variable integration rate;
and the integration rate of the integrating controller is increased
after the timing output signal has been applied thereto.
5. Apparatus according to claim 3, wherein the timing circuit (14)
comprises a pulse source (17) providing cyclically recurring output
pulses;
a second integrator (15) connected to integrate the timing
pulses;
and a second threshold detector (16) supplying a trigger signal and
forming said timing output signal when the second integrator has
reached a predetermined level.
6. Apparatus according to claim 5, wherein the pulse source (17)
provides output pulses recurring at a rate proportional to speed of
the internal combustion engine.
7. Apparatus according to claim 3, wherein the timing circuit (18)
comprises
a pulse source (17) providing cyclically recurring output pulses
and a pulse counter means (19, 20) counting the pulses to a
predetermined count and delivering said timing output signal at
said predetermined count of the counter.
8. Apparatus according to claim 7, wherein the pulse source (17)
provides output pulses recurring at a rate proportional to speed of
the internal combustion engine.
9. Apparatus according to claim 4, wherein the integrating
controller (10) comprises
an operational amplifier (39) having a controllable input impedance
(38, 46, 45), the value of the input impedance determining the
integration rate.
10. Apparatus according to claim 9, wherein the input impedance of
the operational amplifier (39) of the integrating controller
comprises
resistance means (38, 46) having two resistance values;
and controllable switching means (45) selectively placing the
resistance means of one or the other value in circuit with the
operational amplifier, the switching state of said controllable
switching means being controlled by said timing signal.
11. Apparatus according to claim 5, wherein the threshold detector
(16) comprises
an operational amplifier (52);
an integrating capacitor (54) connected to the input of the
operational amplifier (52);
a semiconductor switching element (61) controlling the charging of
said capacitor (54) and a second semiconductor switching element
(67) controlling the discharge of said capacitor (54), the state of
said second semiconductor switching element being controlled by the
output signal of said first threshold detector (11).
12. Apparatus according to claim 11, further comprising a current
drain circuit (58) connected in parallel to said capacitor to
permit flow of a controlled discharge leakage current.
13. Apparatus according to claim 3, further comprising a timing
circuit connected to said integrating controller and sensing
elapsed integrating time of said integrating controller;
said timing circuit providing a control signal to said integrating
controller after a predetermined integrating interval has elapsed
to change the integration rate of the controller to a higher
integration rate.
Description
The present invention relates to an apparatus and to a method to
reduce noxious components in the exhaust gases of internal
combustion engines and more particularly to control the ratio of
the mass of the air-fuel mixture applied to the internal combustion
engine, that is, to control the air number lambda (.lambda.), by
sensing the components of the exhaust gases and then controlling an
integrating controller from the sensed signal.
Reference in the specification will be made to the air number,
denoted lambda (.lambda.). This air number .lambda. is a measure of
the composition of the air-fuel mixture. The number .lambda. is
proportional to the mass of air and fuel, and the value of this
number .lambda. is one (.lambda. = 1.0) if a stoichiometric mixture
is present. Under stoichiometric conditions, the mixture has such a
composition that, in view of the chemical reactions, all
hydrocarbons in the fuel can theoretically combine with the oxygen
in the air to provide complete combustion to carbon dioxide and
water. In actual practice, even with a stoichiometric mixture,
unburned non-combusted hydrocarbons and carbon monoxide are
contained in the exhaust gases.
It is an object of the present invention to provide a method and an
apparatus in which the inertia or lag of response of the equipment
to carry out the control function is substantially eliminated.
Subject matter of the present invention: Briefly, the output signal
from the sensing element is applied to a threshold detector. When
the output signal passes a predetermined threshold level, a trigger
signal is provided, the trigger signal being applied to an
integrating controller to change the integrating direction of the
control amplifier connected to control the fuel or air being
applied to the engine and thus to change the composition of the
fuel-air mixture.
The apparatus in accordance with the present invention is simple
and inexpensive, and is reliable under the rough and varied
operating conditions to which it can be subjected in motor vehicle
use. The various electronic components of the control apparatus
respond rapidly and with low dead intervals, and with low inertia,
while still remaining stable.
The invention will be described by way of example with reference to
the accompanying drawings, wherein:
FIG. 1 is a timing diagram illustrating sensed signal voltage over
a time t (line a) and the corresponding output (line b) of an
integrating controller;
FIG. 2 is a general block diagram of one embodiment of the
invention;
FIG. 3 is a general block diagram of another embodiment of the
present invention;
FIG. 4 is a more detailed schematic diagram of apparatus in
accordance with FIG. 2 to control .lambda..
Curve a in FIG. 1 shows the sensed signal voltage from a sensor,
such as an oxygen sensor 13 (FIG. 2) exposed to the exhaust gases
of an internal combustion engine. For a detailed description of the
engine, and the sensing apparatus, reference is made to the cross
referenced applications. Curve a clearly illustrates that upon
change of the air number .lambda. about the value .lambda. = 1, the
output signal of the sensor 13 rapidly changes between limiting
values. If the air number .lambda. changes by a relatively large
amount, which may, for example, occur during acceleration of the
internal combustion engine, then the output signal of the sensor
will remain at one of its limits for a comparatively long period of
time.
The resulting control voltage, for example the voltage derived from
a control amplifier, is illustrated by curve b, in which the output
voltage of a controller with integrating characteristic is shown.
Each time that the sensor voltage goes through a zero value, the
integration direction of the integrating controller changes. This
causes the air number .lambda. to be always controlled in the
direction of .lambda. = 1. If, for example, the sensor voltage
remains for a longer period of time at one limited value, as
indicated by section a.sub.1, then it would take a comparatively
long period of time until the air number .lambda. is controlled
back to have the value of .lambda. = 1. The output signal of the
controller is indicated by the section a' of line b.
If it is determined that the output signal of the sensor has
remained at a substantially constant value for a predetermined
period of time then, in accordance with a feature of the invention,
the integrating rate of the integrating controller is changed. If,
for example, the sensor has remained at one limited value for the
time duration t.sub.o, then the integrating rate is changed to that
illustrated in the broken curve b'. This causes a greater change in
the controlling effect, so that the sensor will more rapidly sense
a change at air number .lambda. = 1, namely at t.sub.1. Thus, the
sensor voltage will reach already at the time period t.sub.1 a
change to the other limiting value, as indicated in the broken line
c of line a indicative of sensor voltage. Thus, by changing the
time constant of the control amplifier, that is, by changing the
integration rate in dependence on the number of changes of the
output voltage of the sensor 13 through a certain threshold level,
and controlling the timing constant, or integration rate of an
integrating controller, the relative proportion of air and fuel
applied to an internal combustion engine can be made much faster,
so that the air number .lambda. is likewise controlled to have a
value .lambda. = 1 at a faster rate.
FIG. 2 illustrates an apparatus to carry out the present invention.
Sensor 13, exposed to exhaust gases and sensing, for example,
oxygen therein, is connected to an amplifier 12 which is in turn
connected to a threshold detector or threshold switch 11. Threshold
switch 11 has its output connected to an integrating
controller-amplifier 10. The output of threshold detector 11 is
additionally connected to a timing circuit 14, the output from
which is connected to the integrating controller 10 in order to
adjust or set the integrating rate thereof. The internal combustion
engine is only shown schematically at E, and the output shaft
thereof is connected to a pulse generator 17 which provides pulses
to an integrator 15, in turn connected to a threshold detector 16,
elements 15 and 16 forming part of the timing circuit 14. Pulse
generator 17 provides pulses of constant pulse duration but of a
pulse repetition rate depending on engine speed. The output from
the integrating controller 10 is available at an output control bus
10'.
Operation: The exhaust gas sensor 13 provides an output signal,
depending on the composition of the exhaust gases, which varies
between well defined limits, as explained in detail in the cross
referenced applications and more particularly in U.S. Ser. No.
259,157, the disclosure of which is herein incorporated by
reference. The output signal is applied to amplifier 12 and then to
threshold switch 11. Each time when the output signal from sensor
13 passes the threshold of the threshold switch, threshold switch
11 will provide an output trigger signal to change the direction of
integration of the integrating controller 10. The characteristics
of the integrating controller 10 are schematically illustrated
within the block 10 of FIG. 2 in full line. Simultaneously with
each change of the integration direction, integrator 15 is re-set
to zero. In a simple form, integrator 15 can merely be a capacitor
which is discharged, to re-charge again with pulses derived from
pulse generator 17. After re-set, integrator 15 integrates the
pulses, of constant pulse duration, derived from pulse generator
17. This integration continues to the next trigger signal from
threshold switch 11. Upon such a trigger signal, integrator 15
again is re-set to zero to commence integration over again, that
is, the capacitor therein is discharged.
If the trigger signal from threshold switch 11 is not received
within a reasonable time, that is, if the sensor 13 remains for a
predetermined period of time at one limiting position as indicated,
for example, by time period t.sub.o in FIG. 1, then the output
signal of integrator 15 will reach a limit or threshold value of
the second threshold switch 16. When threshold switch 16 is
triggered, it provides a control signal, for example in form of a
pulse to integrating controller 10 to change the time constant of
the integrating controller 10 to a much faster integration rate as
indicated in the broken line within block 10. The changed
integration rate provides faster action of the controller, in
accordance with broken line b' (FIG. 1), and, due to the faster
integration rate, the relationship of the masses of fuel and air of
the fuel-air mixture can be regulated to a value of .lambda. = 1,
or approximately 1, more rapidly.
FIG. 3 illustrates another embodiment of the system of the present
invention to control the air number .lambda.. Similar elements have
been given the same reference numerals and will not be described
again. As before, sensor 13 applies its output signal over
amplifier 12 to threshold switch 11 which triggers integrating
controller 10. The timing circuit 18, in this embodiment, includes
a pulse generator 17 which is connected to a counter 19, having
parallel outputs connected to a decode and trigger circuit 20. The
threshold switch 11 is connected to counter 19; the output of
decode and trigger circuit 20 is connected to the integrating
controller 10 to change its integrating rate, when a trigger signal
is derived from circuit 20. The output from integrating controller
10, over line 10' is applied to an air-fuel mixture controller C
which controls the relative proportion of air and fuel over lines
A, F, being applied to internal combustion engine E. The details of
the control are set forth in the cross referenced applications. The
engine itself is connected to the pulse generator 17 so that the
pulses from pulse generator 17 will have a pulse repetition rate
representative of engine speed.
Operation: Basically, the operation is the same as the embodiment
of FIG. 2. When a trigger signal is derived from switch 11, the
counter 19 is re-set to zero and starts to count at a counting rate
determined by the pulses from pulse generator 17. When the counter
reaches a predetermined counting state, as determined by decoding
circuit 20, then decoding circuit 20 provides a trigger signal
integrating controller 10 to change the time integration rate of
the controller 10 so that the air number .lambda. will be
controlled to a value of approximately 1 more rapidly.
FIG. 4 is a detailed block diagram of the circuit of the present
invention to control the air number .lambda.. Amplifier 12,
connected to sensor 13, includes an operational amplifier 21.
Resistor 23 is connected between the output of operational
amplifier 21 and the inverting input 22 thereof; the sensor 13 is
connected over a coupling resistor 24 to the inverting input. The
sensor 13 provides an output voltage characteristic of the
composition of the air-fuel mixture, as sensed by analysis of the
exhaust gases by sensor 13. The second input 25 of operational
amplifier 21 is connected over a resistance 26 to the tap point of
a voltage divider formed of resistors 27, 28 and connected between
a common positive bus 29 and a common negative or chassis bus 30.
The output of operational amplifier 21 has an output resistor 31,
connected to positive bus 29 with its other terminal. The output is
further coupled by means of coupling resistor 32 to the inverting
input of an operational amplifier 33 which is part of the threshold
switch 11. The second input of operational amplifier 33 is
connected over coupling resistor 34 to a voltage divider formed of
resistors 35, 36, connected between the positive and negative buses
29, 30. The output of operational amplifier 33 is connected over
load resistor 37 to the positive bus 29 and, further, over coupling
resistor 38 to the inverting input of operational amplifier 39
forming part of the integrating controller 10. The output of
operational amplifier 39 is connected to the inverting input by
means of a capacitor 40, which provides for the integrating
characteristics of control amplifier 10. The non-inverting input of
the operational amplifier is connected by coupling resistor 41 to
the tap point of a voltage divider formed of resistors 42, 43,
connected between the supply buses 29, 30. The output of
operational amplifier 39 is coupled to positive bus 29 by resistor
44, and is further connected to output terminal 10', for connection
to a controller to control the mass relationship of the air-fuel
mixture for the internal combustion engine.
The input resistor 38 to operational amplifier 39 has a parallel,
shunt connection formed of the emitter-collector path of a
transistor 45 and a resistor 46. The control electrode of the
resistor 45, which is a npn switching transistor, is connected over
a coupling resistor 47 with the output electrode of a switching
transistor 48, forming part of the timing circuit 14 (FIG. 2).
Switching transistor 48 is connected to positive bus 29 over a
coupling resistor 49, and has its emitter connected to common
negative or chassis bus 30.
Transistor 48 is controlled over its base, by being connected to
the end point of a voltage divider formed of resistors 50, 51, the
tap point of which is formed by the output of an operational
amplifier 52 forming part of the second threshold switch 16. The
inverting input of operational amplifier 52 is connected over a
coupling resistor 53 to a capacitor 54. The positive input of the
operational amplifier 52 is connected to the tap point of a voltage
divider formed of resistors 56, 57 which are connected across the
positive and negative buses 29, 30. Capacitor 54 has a controllable
variable resistor 58 in parallel thereto, and is connected over
diode 59 and a resistor 60 to the output electrode of a switching
transistor 61, which is further coupled to the positive bus 29 over
a collector resistor 62. The emitter of transistor 61 is connected
to negative bus 30; the control electrode, i.e. the base of
transistor 61 is connected to a control circuit formed of resistor
63 connected to negative bus 30, a diode 64 and resistor 66,
connecting to the positive bus 29. At the junction between the
diode 64 and resistor 66, a coupling condenser 65 connects to a
terminal which, in turn, is connected to pulse generator 17, not
shown in FIG. 4. Capacitor 54 is connected parallel to the
switching circuit of transistor 67, that is, in the
emitter-collector path, which also includes a resistor 68. The base
of transistor 67 is connected over a resistor 81 to the output
electrode of a switching transistor 69, the collector of which is
further connected over collector resistor 70 to positive bus 29.
The emitter of transistor 69 is connected to the common chassis bus
30. Control electrode of switching transistor 69 is connected over
resistor 71 to common positive bus 29 and further to two diodes 72,
73. Diode 73 connects to the junction point of a resistor 80
connected to common negative bus 30, and a capacitor 74 which is
connected to the output of operational amplifier 33 of the first
threshold switch 11. Diode 72 is connected to the junction point of
a resistor 75, likewise connected to the common chassis bus 30, and
a capacitor 76, which is connected to the collector of a transistor
77, the emitter-collector path of which is connected in series with
a resistor 78 between positive and negative buses 29, 30. The
control electrode of transistor 77 is connected over a resistor 79
to the output of operational amplifier 33.
Operation of the circuit in accordance with FIG. 4: The output
signal of sensor 13 is amplified by amplifier 12 and applied to
threshold detector 11. The integrating direction of integrating
amplifier controller 10 is changed in dependence on the output
signal of operational amplifier 33 of threshold switch 11, by
changing of the voltage applied to operational amplifier 39 over
resistor 38. The time constant of the integrating process of the
operational amplifier 39 is determined by the value of the input
resistance, in the present case the value of resistor 38. If the
time constant is to be changed, then resistor 46 is placed in
parallel to resistor 38 by rendering transistor 45 conductive. The
conduction state of switching transistor 45 is controlled by the
second threshold detector switch 16. This control depends on the
charge state of capacitor 54. Capacitor 54 is charged over
resistors 62, 60 and diode 59 when transistor 61 is blocked. The
charge is interrupted when transistor 61 becomes conductive.
Conduction of transistor 61 is controlled by pulses applied to the
base of transistor 61 from the pulse source 17 over capacitor 65
and diode 64. These pulses have constant pulse duration, the pulse
repetition rate, however, being proportional to engine speed. The
output electrode of transistor 61 will have a negative voltage when
transistor 61 becomes conductive, thus interrupting charging of
capacitor 54. Resistor 58 connected in parallel to capacitor 54
discharges the capacitor 54 during the interval between pulses, the
discharge current being determined by the resistance value of
resistor 58. Since the pulse interval between pulses is greater at
low speed than at high speed, capacitor 54 is discharged to a
greater extent at low engine speed. At low speed, therefore, more
charge pulses are ncessary to charge capacitor 54 to a
predetermined level than at high speed. Thus, compensation of the
speed-dependent processes in the exhaust system of the internal
combustion engine is obtained automatically.
After a certain predetermined period of time, that is, after a
certain number of charge pulses, in view of the discharge rate
through resistor 58, the capacitor 54 will have a given charge
thereon which corresponds to the switching limit of the second
threshold switch 16. As soon as the threshold of operational
amplifier 52 is reached, the amplifier 52 will provide a negative
output signal which blocks the normally conductive transistor 48.
When transistor 48 blocks, the base of transistor 45 has a positive
voltage applied thereto, controlling transistor 45 to conduct, and
effectively placing resistor 46 in parallel to resistor 38, and
thus changing the integration rate of operational amplifier 39.
Charge on the condenser is interrupted at each switch-over of the
threshold switch 11, and capacitor 54 is again discharged. The
discharge is effected over resistor 68 and the emitter-collector
path of transistor 67. Transistor 67 is controlled to conduct when
its base has a positive voltage applied thereto, which is provided
by blocking of transistor 69. The conduction-blocking switch-over
characteristics of transistor 69 is determined by a negative signal
applied to its base, which is transferred either by diode 72 or by
diode 73. When the output signal of operational amplifier 33
becomes positive, transistor 77 will become conductive and a
negative signal is transferred over capacitor 76 and diode 72 to
the base of transistor 69. If a negative signal is derived from
operational amplifier 33, it is directly transferred over capacitor
74 and diode 73. Thus, the condenser 54 is discharged at each
change of integration direction of the integrating control
amplifier 10. When, however, a switch-over of the threshold switch
11 is delayed over a longer period of time, then threshold switch
16 will respond and the time constant of the integrating control
amplifier 10 is changed. As above described, the time which the
controller requires to change the relative proportion of air and
fuel to control the air number .lambda. to a value of .lambda. =
approximately 1, is substantially reduced.
Various changes and modifications may be made within the inventive
concept.
* * * * *