CA1083691A - Electronic closed loop air-fuel ratio control system - Google Patents
Electronic closed loop air-fuel ratio control systemInfo
- Publication number
- CA1083691A CA1083691A CA271,272A CA271272A CA1083691A CA 1083691 A CA1083691 A CA 1083691A CA 271272 A CA271272 A CA 271272A CA 1083691 A CA1083691 A CA 1083691A
- Authority
- CA
- Canada
- Prior art keywords
- signal
- integrator
- air
- fuel ratio
- receiving
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
- F02D41/1477—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the regulation circuit or part of it,(e.g. comparator, PI regulator, output)
- F02D41/1479—Using a comparator with variable reference
Abstract
Abstract of the Disclosure A reference voltage, which is compared with an output voltage of an exhaust gas sensor in a differential signal generator of an electronic closed loop air-fuel ratio control system, changes depending upon a mean value of an output of the exhaust gas sensor provided in an exhaust pipe extending from an internal combustion engine.
Furthermore, the magnitude of the reference voltage is limited in such a manner as to be within a predetermined range, or in other words, the magnitude of the reference voltage is limited at at least one of an upper and a lower values thereof.
Furthermore, the magnitude of the reference voltage is limited in such a manner as to be within a predetermined range, or in other words, the magnitude of the reference voltage is limited at at least one of an upper and a lower values thereof.
Description
g~ 3~
. .
The present invention relates generally to an electronic closed loop air-fuel ratio control system for use with an internal combustion engine, and par-ticularly to an improvement in such a system for op-timally controlling an air-fuel mixture fed to the engine by li.miting the magni-tude of a reference signal within a predetermined range, the reference signal being com-pared with an output voltage of an exhaust gas sensor in a differential signal generator.
Various systems have been proposed to supply an optimal air-fuel mixturc to an internal combustion engine in accordance with the mode of engi.ne operation, one of which is to utilize the concept of an electronic closed loop control system based on a sensed concen-tration of a component in exhaust gases of the enyine.
According to the conventional system, an exhaust gas sensor, such as an oxygen analyzer, is deposlted in an exhaust pipe for sensing a component of exhaust gases from an internal combustion engine, generating an electrical signal representative of the sensed component. ~ differential signal generator is con-nected to the sensor for generating an electrical :~ signal representative of a differential between the signal from the sensor and a refer.ence signal. The reference siyna] is previously determined in due .~, ~0831~;9~
` consideration of, for example, an optimum ratio of an air-fuel mixture to the engine for maximi~ing the efficiency of both the en~ine and an exhaust gas refin-ing means. A so~called proportional-integral (p-i) controller is connected to the differential signal generator, receiving the signal therefrom. A pulse generator is connected to the p-i controller, receiving a signal therefrom and generating, based on the received signal, a train of pulses which is fed to an air-fuel ratio regulating means, such as electromagnetic valves, for supplying an air-fuel mixture with an optimum air-fuel ratio to the engine.
In the previously described control system, a problem has been encountered that the exhaust gas sensor generates a signal whose magnitude changes undesirably with change of atmospheric temperature, and with decrease of its efficiency due to a lapse of time. This change of the magnitude makes difficult a precise control of the air-fuel mixture ratio. In orde.r to remove this defect, in accordance with the prior art, the magnitude of the reference signal has been changed depending upon change of a means value of the magnitude of the signal from the exhaust gas sensor.
However, in spite of this improvement, another problem has been encountered. That is, when for example, ~ - 3 -:, :
.~ .~ . . .. . .
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; the output of the exhaust gas sensor decreases or ~ncreases due to certain causes to a considerable extent~
the magnitude of the reference signal, resultantly, decreases or increases considerably. Therefore, the air-fuel mixture ratio cannot be precisely controlled for a certain period of time in that a transient time of a circuit determining the mean value cannot be neglected. These defects inherent in the prior art will -be discussed in detail in conjunction with an accompany-ing drawings of Fig. 2.
It is therefore an object of the present invention to provide an improved electronic closecl loop control system for removing the above descrlbed inherent defects of the prior art.
; 15 Another object of the present invention is to provide an improved electronic closed loop air-fuel ratio control system which includes a limiter for limit-ing the magnitude of a reference signal within a prede-termined range.
I'hese and o-ther objects, features and many of the attendant advantages of the invention will be appreciated ~' more readily as the invention becomes better understoocl by the following detailed description, wherein like parts in each of the several figures are identiEied by the same reference characters, and wherein:
~B3 :' Fig. 1 schematically illustrates a conventional electronic closed loop air fuel ratio control system for regulating the air-fuel ratio of the air-fuel mixture fed to an internal combustion engine;
Fig. 2 is a detailed block diagram of an element of the system of Fig. l;
Fig. 3 is a graph showing an output voltage of an exhaust gas sensor as a function of an air-fuel ratio;
Fig. 4 is a first preferred embodiment of the present invention;
Fig. 5 is a second preferred emhodiment of the present invention;
Flg. 6 is a third preferred embodiment of the present invention; and Fig. 7 is a fourth preferred embodiment of the present invention.
Reference is now made to drawings, first to Fig. 1, which schematically exemplifies in a block diagram a conventional electronic closed loop control system with which the present invention is concerned. The purpose of the system of Fig. 1 is to electrically con-trol the air-fuel ratio of an air-fuel mixture supplied to an internal combustion engine 6 through a carburetor (no numeral). An exhaust gas sensor 2, such as an Z5 oxygen, CO, HC, NOX, or CO2 analyzer, is disposed in .~
~a~8369~ ~:
an exhaust pipe ~ in order to sense the concentration of a component in exhaust gases. An electrical signal :~
from the exhaust gas sensor 2 is fed to a control uni-t 10, in which the signal is compared with a reference S .signal to generate a signal representing a differentia:L
therebetween. The magnitude of the reference signal is previously determined in due consideration of an cptimum air-fuel ratio of the air-fuel mixture supplied to the ~ ;
- engine 6 for maximiæing the efficiency of a catalytic .10 converter 8. The control unit 10, then, generates a command signal, or in other words, a train of command pulses based on the signal representative of the optimum air-fuel ratio. The command signal is employed to drive .
two electromagnetic valves 14 and 16. The control unit 10 will be described in more detail in conjunction with Fig. 2.
The electromagnetic valve 14 is provided in an air passage 18, which terminates at one end thereof at an air bleed chamber 22, to con-trol a ~ate of air flowing into the air bleed chamber 22 in response to the command pulses from the control unit 10. The air bleed chamber 22 is connected to a fuel passage 2G for mixing air with fuel delivered from a float bowl 3~, supplying the air-fuel mixture to a venturi 34 through a discharging (or main) nozzle 32. Whilst, the other electromagnetic ~
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valve 16 is providçd in another air passage 20, which terminates at one end thereof at another air bleed : chamber 2~, to control a rate of air flowing into the air bleed chamber 24 in response to the command pulses :.
from the control unit 10. The air bleed chamber 2~ is -connected to the fuel passage 26 through a fuel branch passage 27 for mixing air with fuel from the float bowl ~:
30, supplying the air-fuel mixture to an intake passage 33 through a slow nozzle 36 adjacent to a throttle 40.
As shown, the catalytic converter 8 is provided in the exhaust pipe 4 downstream of the exhaust gas sensor 2.
In the case wherel for example, the electronic closed loop control system is designed to set the air-fuel ratio of the air-fuel mixture to about stoichiometry.
This is because the three-way catalytic converter is able to simultaneously and most effectively reduce nitrogen oxides (NOX), carbon monoxide (CO), and hydrocarbons ~HC), only when the air-fuel mixture ratio is set at about stoichiometry. It is apparent, on the other hand, that, when other catalytic converter such as an oxidizing or deoxidizing type is employed, case ~: by case setting of an air-fuel mixture ratio, which is different from the above, will be required for effective reduction of noxious component(s).
Reference is now made to ~ig. 2, in which somewhat _ 7 _ 8369~
detailed arrangement of the control unit 10 is schemat-ically exemplified. The signal from -the exhaust gas sensor 2 is fed to a difference detectincl circuit 42 of the control unit 10, which circuit compares the incoming signal with a reference one to generate a signal representing a difference therebetween. The signal from the difference detecting circuit 42 is then fed to two circuits, viz., a proportional circuit 44 and an integration circuit 46. The purpose of the provision of the proportional and the integration circuits 44 and 46 i5, as is well known to those skilled in the art, to increase both a response characteristic and stabillty of the system. The signals from the ci~cuits 44 and 46 are then fed to an adder 48 in which the two ~-signals are added. The signal from the adder 48 is : then applied to a pulse generator 50 to which a dither signal is also fed from a dither signal generator 52. ~.
The pulse generator 50 compares the signals from the adder 48 and the generator 52 generating a command signal based on the signal from the adder 48. The com- :
mand signal, which is in the form of pulses, is fed to the valves 14 and 16, thereby to control the "on" and "off" operation thereof.
In Figs. 1 and 2, the electronic closed loop air-fuel ratio control system is illustrated together with _ ~ _ ~369~
a carburetor, however, it should be noted that the system is also applicable to a fuel injection device.
Reference is now made to Fiy. 3, whlch is a graph showing an output voltage of an 2 sensor as a function of an air-fuel ratio by way of example. In Fig. 3, an air-fuel ratio 14.8 on an abscissa means a stoichiometry, and a solid line a denotes an output characteristic when the 2 sensor functions properly, and, on the other hand, a broken line _ denotes an outpu-t characteristic when the function of the 2 sensor lowers with a lapse of time.
Therefore, it i5 understood that, in order to set an air-fuel ratio to 1~.8 while the 2 sensor functions properly, the aforesaid reference voltage should be set to 0.5 volt. Whilst, in the case where the function of the 2 sensor lowers, for example, with a lapse of time, if the reference voltaye remains 0.5 volt, the air-fuel ratio becomes less than the stoichiometry as shown by reference character "x", resultlng in the fact that an optimal air-fuel ratio control is no longer attained.
The above described defect, which results from the fixed reference voltage, also occurs upon cold engine start. This is because the internal impedance of the 2 sensor is considerably high at a low temper-ature so that the output voltage of the 2 sensor becomes ~0l~3~ii91 :
low resultantly.
In order to remove the inherent defect of theprior art, a method has been proposed which changes the magnitude of the reference voltage depending upon a change of a mean value of the sensor's output. In accordance with this method, when the function of the
. .
The present invention relates generally to an electronic closed loop air-fuel ratio control system for use with an internal combustion engine, and par-ticularly to an improvement in such a system for op-timally controlling an air-fuel mixture fed to the engine by li.miting the magni-tude of a reference signal within a predetermined range, the reference signal being com-pared with an output voltage of an exhaust gas sensor in a differential signal generator.
Various systems have been proposed to supply an optimal air-fuel mixturc to an internal combustion engine in accordance with the mode of engi.ne operation, one of which is to utilize the concept of an electronic closed loop control system based on a sensed concen-tration of a component in exhaust gases of the enyine.
According to the conventional system, an exhaust gas sensor, such as an oxygen analyzer, is deposlted in an exhaust pipe for sensing a component of exhaust gases from an internal combustion engine, generating an electrical signal representative of the sensed component. ~ differential signal generator is con-nected to the sensor for generating an electrical :~ signal representative of a differential between the signal from the sensor and a refer.ence signal. The reference siyna] is previously determined in due .~, ~0831~;9~
` consideration of, for example, an optimum ratio of an air-fuel mixture to the engine for maximi~ing the efficiency of both the en~ine and an exhaust gas refin-ing means. A so~called proportional-integral (p-i) controller is connected to the differential signal generator, receiving the signal therefrom. A pulse generator is connected to the p-i controller, receiving a signal therefrom and generating, based on the received signal, a train of pulses which is fed to an air-fuel ratio regulating means, such as electromagnetic valves, for supplying an air-fuel mixture with an optimum air-fuel ratio to the engine.
In the previously described control system, a problem has been encountered that the exhaust gas sensor generates a signal whose magnitude changes undesirably with change of atmospheric temperature, and with decrease of its efficiency due to a lapse of time. This change of the magnitude makes difficult a precise control of the air-fuel mixture ratio. In orde.r to remove this defect, in accordance with the prior art, the magnitude of the reference signal has been changed depending upon change of a means value of the magnitude of the signal from the exhaust gas sensor.
However, in spite of this improvement, another problem has been encountered. That is, when for example, ~ - 3 -:, :
.~ .~ . . .. . .
~il36~
; the output of the exhaust gas sensor decreases or ~ncreases due to certain causes to a considerable extent~
the magnitude of the reference signal, resultantly, decreases or increases considerably. Therefore, the air-fuel mixture ratio cannot be precisely controlled for a certain period of time in that a transient time of a circuit determining the mean value cannot be neglected. These defects inherent in the prior art will -be discussed in detail in conjunction with an accompany-ing drawings of Fig. 2.
It is therefore an object of the present invention to provide an improved electronic closecl loop control system for removing the above descrlbed inherent defects of the prior art.
; 15 Another object of the present invention is to provide an improved electronic closed loop air-fuel ratio control system which includes a limiter for limit-ing the magnitude of a reference signal within a prede-termined range.
I'hese and o-ther objects, features and many of the attendant advantages of the invention will be appreciated ~' more readily as the invention becomes better understoocl by the following detailed description, wherein like parts in each of the several figures are identiEied by the same reference characters, and wherein:
~B3 :' Fig. 1 schematically illustrates a conventional electronic closed loop air fuel ratio control system for regulating the air-fuel ratio of the air-fuel mixture fed to an internal combustion engine;
Fig. 2 is a detailed block diagram of an element of the system of Fig. l;
Fig. 3 is a graph showing an output voltage of an exhaust gas sensor as a function of an air-fuel ratio;
Fig. 4 is a first preferred embodiment of the present invention;
Fig. 5 is a second preferred emhodiment of the present invention;
Flg. 6 is a third preferred embodiment of the present invention; and Fig. 7 is a fourth preferred embodiment of the present invention.
Reference is now made to drawings, first to Fig. 1, which schematically exemplifies in a block diagram a conventional electronic closed loop control system with which the present invention is concerned. The purpose of the system of Fig. 1 is to electrically con-trol the air-fuel ratio of an air-fuel mixture supplied to an internal combustion engine 6 through a carburetor (no numeral). An exhaust gas sensor 2, such as an Z5 oxygen, CO, HC, NOX, or CO2 analyzer, is disposed in .~
~a~8369~ ~:
an exhaust pipe ~ in order to sense the concentration of a component in exhaust gases. An electrical signal :~
from the exhaust gas sensor 2 is fed to a control uni-t 10, in which the signal is compared with a reference S .signal to generate a signal representing a differentia:L
therebetween. The magnitude of the reference signal is previously determined in due consideration of an cptimum air-fuel ratio of the air-fuel mixture supplied to the ~ ;
- engine 6 for maximiæing the efficiency of a catalytic .10 converter 8. The control unit 10, then, generates a command signal, or in other words, a train of command pulses based on the signal representative of the optimum air-fuel ratio. The command signal is employed to drive .
two electromagnetic valves 14 and 16. The control unit 10 will be described in more detail in conjunction with Fig. 2.
The electromagnetic valve 14 is provided in an air passage 18, which terminates at one end thereof at an air bleed chamber 22, to con-trol a ~ate of air flowing into the air bleed chamber 22 in response to the command pulses from the control unit 10. The air bleed chamber 22 is connected to a fuel passage 2G for mixing air with fuel delivered from a float bowl 3~, supplying the air-fuel mixture to a venturi 34 through a discharging (or main) nozzle 32. Whilst, the other electromagnetic ~
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valve 16 is providçd in another air passage 20, which terminates at one end thereof at another air bleed : chamber 2~, to control a rate of air flowing into the air bleed chamber 24 in response to the command pulses :.
from the control unit 10. The air bleed chamber 2~ is -connected to the fuel passage 26 through a fuel branch passage 27 for mixing air with fuel from the float bowl ~:
30, supplying the air-fuel mixture to an intake passage 33 through a slow nozzle 36 adjacent to a throttle 40.
As shown, the catalytic converter 8 is provided in the exhaust pipe 4 downstream of the exhaust gas sensor 2.
In the case wherel for example, the electronic closed loop control system is designed to set the air-fuel ratio of the air-fuel mixture to about stoichiometry.
This is because the three-way catalytic converter is able to simultaneously and most effectively reduce nitrogen oxides (NOX), carbon monoxide (CO), and hydrocarbons ~HC), only when the air-fuel mixture ratio is set at about stoichiometry. It is apparent, on the other hand, that, when other catalytic converter such as an oxidizing or deoxidizing type is employed, case ~: by case setting of an air-fuel mixture ratio, which is different from the above, will be required for effective reduction of noxious component(s).
Reference is now made to ~ig. 2, in which somewhat _ 7 _ 8369~
detailed arrangement of the control unit 10 is schemat-ically exemplified. The signal from -the exhaust gas sensor 2 is fed to a difference detectincl circuit 42 of the control unit 10, which circuit compares the incoming signal with a reference one to generate a signal representing a difference therebetween. The signal from the difference detecting circuit 42 is then fed to two circuits, viz., a proportional circuit 44 and an integration circuit 46. The purpose of the provision of the proportional and the integration circuits 44 and 46 i5, as is well known to those skilled in the art, to increase both a response characteristic and stabillty of the system. The signals from the ci~cuits 44 and 46 are then fed to an adder 48 in which the two ~-signals are added. The signal from the adder 48 is : then applied to a pulse generator 50 to which a dither signal is also fed from a dither signal generator 52. ~.
The pulse generator 50 compares the signals from the adder 48 and the generator 52 generating a command signal based on the signal from the adder 48. The com- :
mand signal, which is in the form of pulses, is fed to the valves 14 and 16, thereby to control the "on" and "off" operation thereof.
In Figs. 1 and 2, the electronic closed loop air-fuel ratio control system is illustrated together with _ ~ _ ~369~
a carburetor, however, it should be noted that the system is also applicable to a fuel injection device.
Reference is now made to Fiy. 3, whlch is a graph showing an output voltage of an 2 sensor as a function of an air-fuel ratio by way of example. In Fig. 3, an air-fuel ratio 14.8 on an abscissa means a stoichiometry, and a solid line a denotes an output characteristic when the 2 sensor functions properly, and, on the other hand, a broken line _ denotes an outpu-t characteristic when the function of the 2 sensor lowers with a lapse of time.
Therefore, it i5 understood that, in order to set an air-fuel ratio to 1~.8 while the 2 sensor functions properly, the aforesaid reference voltage should be set to 0.5 volt. Whilst, in the case where the function of the 2 sensor lowers, for example, with a lapse of time, if the reference voltaye remains 0.5 volt, the air-fuel ratio becomes less than the stoichiometry as shown by reference character "x", resultlng in the fact that an optimal air-fuel ratio control is no longer attained.
The above described defect, which results from the fixed reference voltage, also occurs upon cold engine start. This is because the internal impedance of the 2 sensor is considerably high at a low temper-ature so that the output voltage of the 2 sensor becomes ~0l~3~ii91 :
low resultantly.
In order to remove the inherent defect of theprior art, a method has been proposed which changes the magnitude of the reference voltage depending upon a change of a mean value of the sensor's output. In accordance with this method, when the function of the
2 sensor becomes low as shown by the broken line, the reference voltage is lowered to, for example, "~", so ;~
that the air-~uel ratio is shifted more nearer to the stoichiometry as shown by "x'" compared with the first mentioned case.
~lowever, in spite of this improvement, there are "
encountered some defects therein. That is, if the OUtpllt of the sensor 3 falls or rises considerably due to a low temperature or other reasons, then, the refer-ence voltage resultantly falls or rises to a considerable extent. In the above, once the output of the sensor 3 falls or rises considerably, even if return~ng to a normal state thereafter, a rich or a lean air-Euel mixture ratio remains undesirably during a certain period of time. This is because a transient time of a circuit producing the mean value of the sensor 3 cannot be neglected.
The present invention, therefore, contemplates removing the above mentioned shortcomings inherent in , - ~8369~L
the prior art by limiting the reference voltage within a predetermined.range.
Reference is now made to Fig. 4, which illustrates a first embodiment of the present invention. The signal from the exhaust gas sensor 3 is applied to the differ-ential signal generator 42, more specifically, to a noninverting terminal 62 of an amplifier 66 through a terminal 60 and a resistor 64, being amplified therein by a preset gain. The output of the amplifier 66 is then fed to an integrator consisting of a resistor 68 and a capacitor 70. A junction 69 between the resistor 68 and a capacitor 70 is coupled to an inverting terminal 72 of a differential amplifier 74. A non-invertin~
termi~al 75 is directly coupled to the output terminal (no numeral) of the ampli.fier 66. The differential ; amplifier 74 produces an output indicative of a dif-ference between the magnitudes of two signals received.
It is understood that the reference voltage, which corresponds to a voltage appearing at the junction 69, changes depending upon the magnitude of the output of the exhaust gas sensor 3. Therefore, output change of the sensor 3, which results from the aforementioned reasons, can be compensated.
As shown, the junction 69 is coupled to the anode of a diode 76 and the cathode of a diode 78. The cathode 10~33~;9~ i . .
of the diode 76 is coupled to a junction 80 between resis-tors 82 and 84, receiving a constant voltage Vu which determines an upper critical value o~ the refer-ence voltage. On the other hand, the anode of the ; 5 diode 78 is coupled to a junction 86 between resistors 88 and 90, receiving a constant voltage VL which in turn determines a lower critical value of the reference voltage. Thus, the reference voltage appearing at the junction 69 is controlled within a predetermined range defined by the two constant voltages V~ and VL.
In Fig. 5, there is shown a second preferred embodiment of the present invention. The differential signal generator 42 has been described so that further illustration will be omitted for brevity. The junction 69 is coupled to a constant d.c. voltage ~VO) supply (not shown) through a resistor 92 and a terminal 94.
According to the second preferred em~odiment, the reference voltage at the junction 69 is limited within `~
a predetermined range as discussed below.
Assuming that the output voltage of the amplifier 66 is E, and that the voltage at the junction 69 is V69, then we obtain :~ ' ~ - 12 -: ' .
~08369'1 E V69 + _ 69 = j~C70V69 68 92 j (R68 R ) ( ) where R68: resistance of the resistor 68 R92: resistance of the resistor 92 C70: capacitance of the capacitor 70 In the above, if a frequency becomes zero, then j~ ~ O. Therefore, the equation (1) becomes V = 68 92 _ ~ _ + o ~ (2) 69 R68 + R92 ~R68 R92 / ~ :
In the equation (2), assuming E = 0 gives V69 = R + R92 VO
, Furthermore, in the equation (2), assuming E = 2Vo gives V69 = R ~ R92 VO
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As a result, assuming that the maximum value of E is EM and the minimum value of E is 0 and VO = 2- EM~ then, the following is obtained R68 R68+2R92 It is apparent from the above that the reference voltage, viz., V69 is limited within a predetermined range.
Reference is now made to Fig. 6, which illustrates a third preferred embodiment of the present invention.
As shown, a differential siynal generator 42' is the same as the ~enerator 42 except for a switch 100 provided between the amplifier 66 and tlle resistor 68. The out-put terminal tno numeral) of the amplifier 66 is coupled to an integrator whi.ch consists of a resistor 102 and a capacitor 104 and which is analoyous to the integrator of the generator 42'. A junction 103 between the resistor 102 and the capacitor 104 is coupled to an inverting terminal 106 of a comparator 108. A non-inverting terminal 110 of the comparator 108 is coupled to a junction 112 of a voltage divider consisting of resistors 130 and 132, receiving a constant voltage VL
which determines a lower critical level of the refer-ence voltage appearing at the junction 69. On the other hand, the junction 103 is coupled to a non-inverting 1083~;99L
terminal 114 oE another comparator 116. An inverting terminal 118 of the comparator 116 is coupled to a junction 120 of a voltage divider consisting of resistors 134 and 136, receiving a constant voltage Vu which de-termines an upper critical level of the reference voltageappearing at the junction 69. Both the comparators 108 and 116 are coupled to the base of a transistor 122 ; through suitable reslstors (no numeral), respectively.
The collector of the transistor 122 is coupled to a suitable d.c. voltage supply (not shown) through a resistor 124, whilst, the emitter thereof to ground.
It is apparent that the transistor 122, which is oE
NPN type, can be replaced by a transistor of PNP type.
The voltage change at the collector is used for opening or closing the switch 100 of the differential signal generator 42', which will be discussed in detail below.
In operation, when the voltage at the junction 103 falls below the lower critical level VL, the comparator 108 produces a signal indicating a logic "1". This logic "1" renders the transistor 122 conductive, thereby to lower the collector voltage. This voltage drop causes the switch 100 to open. This means that the integrator, which consists of the resistor 68 and the capacitor 70, receives no longer the output of the amplifier 66 so that the voltage at the junction 69 does not decrease once ~.3383~
the switch 100 opens. On the other hand, when the voltage at the junction 103 rises above the upper critical level Vu, the comparator 116 produces a signal indicating a logic "1". This logic "1" renders the transistor 122 conductive, thereby to lower the collector voltage. This voltage drop causes the switch 100 to open.
This means that the integrator, which consists of the resistor 68 and the capacitor 70, receives no longer the output of the amplifier 66 so that the voltage at the junction 69 does not increase once the switch 100 opens.
It is understood that the reference voltage appear-ing at the junction 69 is limited within a range from the voltage VL to Vu.
:;-eference is now made to Fig. 7, which illustrates ~.
schematically a fourth preferred embodiment of the present : invention. A difference between the differential signal generator 42 and the preferred embodiment in question is that the latter includes a capacitor 103 between the resistor 68 and the junction 69' so as to avoid an undesirable condition when an abnormally high voltage `: is produced from the exhaust gas sensor 3, or in other words, from the amplifier 66. More specifically, the . reference voltage, which corresponds to a voltage at the junction 69', is divided by the two capacitors 103 and 70, so that the reference voltage does not unde~irahly ..
~Q8369~
rise even if an abnormally high input is applied, during a relative]y long period of time, to the :integrator consisting o-E the resistor 68 and the capacitors 103 and 70, In the first, the second, and the third preferred embodiments, the reference voltage is limited or clipped at both upper and lower levels. ~Iowever, it should be noted that one of the limitings at the upper and the lower levels can be omitted.
It is understood from the foregoing that, in accordance with the present invention, the air-fuel mixture ratio can be optimally controlled by limiting the reference voltage within a predetermined range.
that the air-~uel ratio is shifted more nearer to the stoichiometry as shown by "x'" compared with the first mentioned case.
~lowever, in spite of this improvement, there are "
encountered some defects therein. That is, if the OUtpllt of the sensor 3 falls or rises considerably due to a low temperature or other reasons, then, the refer-ence voltage resultantly falls or rises to a considerable extent. In the above, once the output of the sensor 3 falls or rises considerably, even if return~ng to a normal state thereafter, a rich or a lean air-Euel mixture ratio remains undesirably during a certain period of time. This is because a transient time of a circuit producing the mean value of the sensor 3 cannot be neglected.
The present invention, therefore, contemplates removing the above mentioned shortcomings inherent in , - ~8369~L
the prior art by limiting the reference voltage within a predetermined.range.
Reference is now made to Fig. 4, which illustrates a first embodiment of the present invention. The signal from the exhaust gas sensor 3 is applied to the differ-ential signal generator 42, more specifically, to a noninverting terminal 62 of an amplifier 66 through a terminal 60 and a resistor 64, being amplified therein by a preset gain. The output of the amplifier 66 is then fed to an integrator consisting of a resistor 68 and a capacitor 70. A junction 69 between the resistor 68 and a capacitor 70 is coupled to an inverting terminal 72 of a differential amplifier 74. A non-invertin~
termi~al 75 is directly coupled to the output terminal (no numeral) of the ampli.fier 66. The differential ; amplifier 74 produces an output indicative of a dif-ference between the magnitudes of two signals received.
It is understood that the reference voltage, which corresponds to a voltage appearing at the junction 69, changes depending upon the magnitude of the output of the exhaust gas sensor 3. Therefore, output change of the sensor 3, which results from the aforementioned reasons, can be compensated.
As shown, the junction 69 is coupled to the anode of a diode 76 and the cathode of a diode 78. The cathode 10~33~;9~ i . .
of the diode 76 is coupled to a junction 80 between resis-tors 82 and 84, receiving a constant voltage Vu which determines an upper critical value o~ the refer-ence voltage. On the other hand, the anode of the ; 5 diode 78 is coupled to a junction 86 between resistors 88 and 90, receiving a constant voltage VL which in turn determines a lower critical value of the reference voltage. Thus, the reference voltage appearing at the junction 69 is controlled within a predetermined range defined by the two constant voltages V~ and VL.
In Fig. 5, there is shown a second preferred embodiment of the present invention. The differential signal generator 42 has been described so that further illustration will be omitted for brevity. The junction 69 is coupled to a constant d.c. voltage ~VO) supply (not shown) through a resistor 92 and a terminal 94.
According to the second preferred em~odiment, the reference voltage at the junction 69 is limited within `~
a predetermined range as discussed below.
Assuming that the output voltage of the amplifier 66 is E, and that the voltage at the junction 69 is V69, then we obtain :~ ' ~ - 12 -: ' .
~08369'1 E V69 + _ 69 = j~C70V69 68 92 j (R68 R ) ( ) where R68: resistance of the resistor 68 R92: resistance of the resistor 92 C70: capacitance of the capacitor 70 In the above, if a frequency becomes zero, then j~ ~ O. Therefore, the equation (1) becomes V = 68 92 _ ~ _ + o ~ (2) 69 R68 + R92 ~R68 R92 / ~ :
In the equation (2), assuming E = 0 gives V69 = R + R92 VO
, Furthermore, in the equation (2), assuming E = 2Vo gives V69 = R ~ R92 VO
369~1L
As a result, assuming that the maximum value of E is EM and the minimum value of E is 0 and VO = 2- EM~ then, the following is obtained R68 R68+2R92 It is apparent from the above that the reference voltage, viz., V69 is limited within a predetermined range.
Reference is now made to Fig. 6, which illustrates a third preferred embodiment of the present invention.
As shown, a differential siynal generator 42' is the same as the ~enerator 42 except for a switch 100 provided between the amplifier 66 and tlle resistor 68. The out-put terminal tno numeral) of the amplifier 66 is coupled to an integrator whi.ch consists of a resistor 102 and a capacitor 104 and which is analoyous to the integrator of the generator 42'. A junction 103 between the resistor 102 and the capacitor 104 is coupled to an inverting terminal 106 of a comparator 108. A non-inverting terminal 110 of the comparator 108 is coupled to a junction 112 of a voltage divider consisting of resistors 130 and 132, receiving a constant voltage VL
which determines a lower critical level of the refer-ence voltage appearing at the junction 69. On the other hand, the junction 103 is coupled to a non-inverting 1083~;99L
terminal 114 oE another comparator 116. An inverting terminal 118 of the comparator 116 is coupled to a junction 120 of a voltage divider consisting of resistors 134 and 136, receiving a constant voltage Vu which de-termines an upper critical level of the reference voltageappearing at the junction 69. Both the comparators 108 and 116 are coupled to the base of a transistor 122 ; through suitable reslstors (no numeral), respectively.
The collector of the transistor 122 is coupled to a suitable d.c. voltage supply (not shown) through a resistor 124, whilst, the emitter thereof to ground.
It is apparent that the transistor 122, which is oE
NPN type, can be replaced by a transistor of PNP type.
The voltage change at the collector is used for opening or closing the switch 100 of the differential signal generator 42', which will be discussed in detail below.
In operation, when the voltage at the junction 103 falls below the lower critical level VL, the comparator 108 produces a signal indicating a logic "1". This logic "1" renders the transistor 122 conductive, thereby to lower the collector voltage. This voltage drop causes the switch 100 to open. This means that the integrator, which consists of the resistor 68 and the capacitor 70, receives no longer the output of the amplifier 66 so that the voltage at the junction 69 does not decrease once ~.3383~
the switch 100 opens. On the other hand, when the voltage at the junction 103 rises above the upper critical level Vu, the comparator 116 produces a signal indicating a logic "1". This logic "1" renders the transistor 122 conductive, thereby to lower the collector voltage. This voltage drop causes the switch 100 to open.
This means that the integrator, which consists of the resistor 68 and the capacitor 70, receives no longer the output of the amplifier 66 so that the voltage at the junction 69 does not increase once the switch 100 opens.
It is understood that the reference voltage appear-ing at the junction 69 is limited within a range from the voltage VL to Vu.
:;-eference is now made to Fig. 7, which illustrates ~.
schematically a fourth preferred embodiment of the present : invention. A difference between the differential signal generator 42 and the preferred embodiment in question is that the latter includes a capacitor 103 between the resistor 68 and the junction 69' so as to avoid an undesirable condition when an abnormally high voltage `: is produced from the exhaust gas sensor 3, or in other words, from the amplifier 66. More specifically, the . reference voltage, which corresponds to a voltage at the junction 69', is divided by the two capacitors 103 and 70, so that the reference voltage does not unde~irahly ..
~Q8369~
rise even if an abnormally high input is applied, during a relative]y long period of time, to the :integrator consisting o-E the resistor 68 and the capacitors 103 and 70, In the first, the second, and the third preferred embodiments, the reference voltage is limited or clipped at both upper and lower levels. ~Iowever, it should be noted that one of the limitings at the upper and the lower levels can be omitted.
It is understood from the foregoing that, in accordance with the present invention, the air-fuel mixture ratio can be optimally controlled by limiting the reference voltage within a predetermined range.
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An electronic closed loop air-fuel ratio control system for supplying an optimum air-fuel mixture to an internal combustion engine, which system comprises in combination:
an air-fuel mixture supply assembly;
an exhaust pipe;
an exhaust gas sensor provided in the exhaust pipe for sensing a concentration of a component in ex-haust gases, generating a signal representative thereof;
a differential signal generator connected to the exhaust gas sensor, receiving the signal therefrom, generating a signal representative of a difference between magnitudes of the signal from the exhaust gas sensor and a reference signal, the reference signal changing in its magnitude in such a manner as to be substantially equal to a means value of the magnitude of the signal from the exhaust gas sensor;
a control signal generator connected to the differential signal generator, receiving the signal therefrom and generating a control signal based on the received signal;
an actuator provided in the air-fuel mixture supply assembly, connected to the control signal generator, receiving and responsive to the control signal to control the air-fuel ratio of an air-fuel mixture fed to the engine, and a limiter connected to the differential signal generator for limiting at least one of an upper and a lower values of the reference signal.
an air-fuel mixture supply assembly;
an exhaust pipe;
an exhaust gas sensor provided in the exhaust pipe for sensing a concentration of a component in ex-haust gases, generating a signal representative thereof;
a differential signal generator connected to the exhaust gas sensor, receiving the signal therefrom, generating a signal representative of a difference between magnitudes of the signal from the exhaust gas sensor and a reference signal, the reference signal changing in its magnitude in such a manner as to be substantially equal to a means value of the magnitude of the signal from the exhaust gas sensor;
a control signal generator connected to the differential signal generator, receiving the signal therefrom and generating a control signal based on the received signal;
an actuator provided in the air-fuel mixture supply assembly, connected to the control signal generator, receiving and responsive to the control signal to control the air-fuel ratio of an air-fuel mixture fed to the engine, and a limiter connected to the differential signal generator for limiting at least one of an upper and a lower values of the reference signal.
2. An electronic closed loop air-fuel ratio control system as claimed in Claim 1, wherein the differential signal generator comprises:
an amplifier provided with an input and an output terminals, being connected at the input terminal to the exhaust gas sensor;
an integrator connected to the output terminal of the amplifier, receiving a signal therefrom to integrate the same, the integrated signal being used as the reference signal, and integrator also connected to the limiter which limits at least one of the upper and the lower values of the reference signal; and a differential amplifier provided with an invert-ing and a non-inverting input terminals, being con-nected to the integrator at one of the input terminals thereof and also directly connected to the output terminal of the amplifier at the other input terminal thereof, generating the signal representative of the difference based on signals received at the inverting and the non-inverting input terminals.
an amplifier provided with an input and an output terminals, being connected at the input terminal to the exhaust gas sensor;
an integrator connected to the output terminal of the amplifier, receiving a signal therefrom to integrate the same, the integrated signal being used as the reference signal, and integrator also connected to the limiter which limits at least one of the upper and the lower values of the reference signal; and a differential amplifier provided with an invert-ing and a non-inverting input terminals, being con-nected to the integrator at one of the input terminals thereof and also directly connected to the output terminal of the amplifier at the other input terminal thereof, generating the signal representative of the difference based on signals received at the inverting and the non-inverting input terminals.
3, An electronic closed loop air-fuel ratio control system as claimed in Claim 2, wherein the integrator is a series circuit consisting of a resistor and a capacitor.
4. An electronic closed loop air-fuel ratio control system as claimed in Claim 3, wherein the limiter com-prises:
a first diode the anode of which is connected to the junction between the resistor and the capacitor of the integrator and the cathode thereof receiving a predetermined voltage corresponding to the upper value;
and a second diode the cathode of which is con-nected to the junction between the resistor and the capacitor of the integrator and the anode thereof re-ceiving another predetermined voltage corresponding to the lower value.
a first diode the anode of which is connected to the junction between the resistor and the capacitor of the integrator and the cathode thereof receiving a predetermined voltage corresponding to the upper value;
and a second diode the cathode of which is con-nected to the junction between the resistor and the capacitor of the integrator and the anode thereof re-ceiving another predetermined voltage corresponding to the lower value.
5. An electronic closed loop air-fuel ratio control system as claimed in Claim 3, wherein the limiter is a d.c. power source connected to the junction between the resistor and the capacitor of the integrator.
6. An electronic closed loop air-fuel ratio control system as claimed in Claim 3, wherein the differential signal generator further comprises a switching means interposed between the amplifier and the integrator, and wherein the limiter comprises:
an integrator provided with an input and an output terminals, being connected at its input terminal to the output terminal of the amplifier, receiving a signal therefrom to integrate the same;
comparator provided with an inverting and a non-inverting input terminals, being connected at its inverting input terminal to the integrator, receiving the integrated signal therefrom, also receiving through its non-inverting input terminal a predetermined voltage corresponding to the lower value, generating a signal indicative of a logic "1" when the integrated signal falls below the predetermined voltage;
another comparator provided with an inverting and a non-inverting input terminals, being connected at its non-inverting terminal to the integrator, receiving the integrated signal therefrom, also receiving through its inverting terminal another predetermined voltage corresponding to the upper value, generating a signal indicative of a logic "1" when the integrated signal rises above the another predetermined voltage; and a switching element connected to output terminals of the above mentioned two comparators, responsive to each of the signals therefrom indicating a logic "1"
to open the switching means.
an integrator provided with an input and an output terminals, being connected at its input terminal to the output terminal of the amplifier, receiving a signal therefrom to integrate the same;
comparator provided with an inverting and a non-inverting input terminals, being connected at its inverting input terminal to the integrator, receiving the integrated signal therefrom, also receiving through its non-inverting input terminal a predetermined voltage corresponding to the lower value, generating a signal indicative of a logic "1" when the integrated signal falls below the predetermined voltage;
another comparator provided with an inverting and a non-inverting input terminals, being connected at its non-inverting terminal to the integrator, receiving the integrated signal therefrom, also receiving through its inverting terminal another predetermined voltage corresponding to the upper value, generating a signal indicative of a logic "1" when the integrated signal rises above the another predetermined voltage; and a switching element connected to output terminals of the above mentioned two comparators, responsive to each of the signals therefrom indicating a logic "1"
to open the switching means.
7. An electronic closed loop air-fuel ratio control system as claimed in Claim 3, wherein the limiter is a capacitor interposed between the resistor and the capacitor of the integrator.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP51-12242 | 1976-02-09 | ||
| JP1224276A JPS5297025A (en) | 1976-02-09 | 1976-02-09 | Air fuel ration controller |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1083691A true CA1083691A (en) | 1980-08-12 |
Family
ID=11799887
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA271,272A Expired CA1083691A (en) | 1976-02-09 | 1977-02-08 | Electronic closed loop air-fuel ratio control system |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US4131089A (en) |
| JP (1) | JPS5297025A (en) |
| CA (1) | CA1083691A (en) |
| DE (1) | DE2705227A1 (en) |
Families Citing this family (22)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS589261B2 (en) * | 1976-09-24 | 1983-02-19 | 日産自動車株式会社 | Air fuel ratio control device |
| DE2702863C2 (en) * | 1977-01-25 | 1986-06-05 | Robert Bosch Gmbh, 7000 Stuttgart | Method and device for regulating the mixture ratio components of the operating mixture fed to an internal combustion engine |
| JPS6042196Y2 (en) * | 1977-05-27 | 1985-12-24 | 日産自動車株式会社 | Air fuel ratio control device |
| JPS6053770B2 (en) * | 1978-02-09 | 1985-11-27 | トヨタ自動車株式会社 | Air-fuel ratio control device for internal combustion engines |
| JPS54108125A (en) * | 1978-02-15 | 1979-08-24 | Toyota Motor Corp | Air fuel ratio controller for internal combustion engine |
| US4191151A (en) * | 1978-03-20 | 1980-03-04 | General Motors Corporation | Oxygen sensor signal processing circuit for a closed loop air/fuel mixture controller |
| GB1564671A (en) * | 1978-04-12 | 1980-04-10 | Hughes Microelectronics Ltd | Comparator |
| JPS54162021A (en) * | 1978-06-13 | 1979-12-22 | Nissan Motor Co Ltd | Air fuel ratio controller |
| JPS55107033A (en) * | 1979-02-09 | 1980-08-16 | Aisin Seiki Co Ltd | Engine revolution control system |
| FR2448638B1 (en) * | 1979-02-09 | 1985-09-27 | Sibe | IMPROVEMENTS ON CARBURETORS FOR INTERNAL COMBUSTION ENGINES |
| JPS5623532A (en) * | 1979-08-02 | 1981-03-05 | Fuji Heavy Ind Ltd | Air-fuel ratio controller |
| GB2056723B (en) * | 1979-08-02 | 1983-07-06 | Nissan Motor | Automatic control of air/fuel ratio in ic engines |
| JPS5623510A (en) * | 1979-08-06 | 1981-03-05 | Toyota Motor Corp | Exhaust gas cleaning method for internal combustion engine |
| JPS5748649A (en) * | 1980-09-08 | 1982-03-20 | Nissan Motor Co Ltd | Controller for air-to-fuel ratio of internal combustion engine |
| JPS5827857A (en) * | 1981-08-12 | 1983-02-18 | Mitsubishi Electric Corp | Air-fuel ratio controlling method |
| US4502444A (en) * | 1983-07-19 | 1985-03-05 | Engelhard Corporation | Air-fuel ratio controller |
| JPH0756229B2 (en) * | 1985-09-18 | 1995-06-14 | 富士重工業株式会社 | Air-fuel ratio controller |
| JP2601455B2 (en) * | 1986-04-24 | 1997-04-16 | 本田技研工業株式会社 | Air-fuel ratio control method for internal combustion engine |
| JPH0350253Y2 (en) * | 1986-05-27 | 1991-10-28 | ||
| JP2806501B2 (en) * | 1987-03-23 | 1998-09-30 | 富士重工業株式会社 | Engine air-fuel ratio control device |
| JP2754501B2 (en) * | 1990-11-29 | 1998-05-20 | 本田技研工業株式会社 | Air-fuel ratio control method for internal combustion engine and method for detecting deterioration of exhaust gas concentration sensor used for air-fuel ratio control |
| JP2583182B2 (en) * | 1993-02-25 | 1997-02-19 | 株式会社アペックス | Muffler for internal combustion engine |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4742407B1 (en) * | 1970-03-05 | 1972-10-26 | ||
| US3834361A (en) * | 1972-08-23 | 1974-09-10 | Bendix Corp | Back-up fuel control system |
| US3815561A (en) * | 1972-09-14 | 1974-06-11 | Bendix Corp | Closed loop engine control system |
| DE2333743C2 (en) * | 1973-07-03 | 1983-03-31 | Robert Bosch Gmbh, 7000 Stuttgart | Method and device for exhaust gas decontamination from internal combustion engines |
| DE2436421C3 (en) * | 1974-07-29 | 1979-04-26 | Robert Bosch Gmbh, 7000 Stuttgart | Device for the electronic adjustment of the ignition point of an ignition system for internal combustion engines |
| US3938479A (en) * | 1974-09-30 | 1976-02-17 | The Bendix Corporation | Exhaust gas sensor operating temperature detection system |
| JPS5228934B2 (en) * | 1974-11-01 | 1977-07-29 | ||
| DE2550623A1 (en) * | 1974-11-14 | 1976-05-26 | Nissan Motor | ARRANGEMENT FOR REDUCING NITROGEN OXIDES IN THE EXHAUST GASES OF A COMBUSTION ENGINE |
| US3939654A (en) * | 1975-02-11 | 1976-02-24 | General Motors Corporation | Engine with dual sensor closed loop fuel control |
| JPS51104131A (en) * | 1975-03-10 | 1976-09-14 | Hitachi Ltd | Enjinno kunenhiseigyosochi |
-
1976
- 1976-02-09 JP JP1224276A patent/JPS5297025A/en active Granted
-
1977
- 1977-02-08 CA CA271,272A patent/CA1083691A/en not_active Expired
- 1977-02-08 DE DE19772705227 patent/DE2705227A1/en not_active Withdrawn
- 1977-02-09 US US05/767,134 patent/US4131089A/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPS573816B2 (en) | 1982-01-22 |
| DE2705227A1 (en) | 1977-08-11 |
| JPS5297025A (en) | 1977-08-15 |
| US4131089A (en) | 1978-12-26 |
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