EP0262956A1 - Steuerungssystem des Luft-Kraftstoffverhältnisses für Verbrennungsmotoren - Google Patents

Steuerungssystem des Luft-Kraftstoffverhältnisses für Verbrennungsmotoren Download PDF

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Publication number
EP0262956A1
EP0262956A1 EP87308674A EP87308674A EP0262956A1 EP 0262956 A1 EP0262956 A1 EP 0262956A1 EP 87308674 A EP87308674 A EP 87308674A EP 87308674 A EP87308674 A EP 87308674A EP 0262956 A1 EP0262956 A1 EP 0262956A1
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EP
European Patent Office
Prior art keywords
air
engine
fuel ratio
internal combustion
sensor
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.)
Granted
Application number
EP87308674A
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English (en)
French (fr)
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EP0262956B1 (de
Inventor
Shinji C/O Himeji Seisakusho Of Kojima
Seiji C/O Himeji Seisakusho Of Wataya
Ryoji C/O Ohyokiki Kenkyusho Of Nishiyama
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Electric Corp
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Mitsubishi Electric Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from JP61233583A external-priority patent/JPS6388244A/ja
Priority claimed from JP61233581A external-priority patent/JPH0617894B2/ja
Priority claimed from JP61233582A external-priority patent/JPS6388243A/ja
Application filed by Mitsubishi Electric Corp filed Critical Mitsubishi Electric Corp
Publication of EP0262956A1 publication Critical patent/EP0262956A1/de
Application granted granted Critical
Publication of EP0262956B1 publication Critical patent/EP0262956B1/de
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Expired - Lifetime legal-status Critical Current

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    • 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
    • F02D41/1493—Details
    • F02D41/1494—Control of sensor heater
    • 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
    • F02D41/04—Introducing corrections for particular operating conditions
    • F02D41/042—Introducing corrections for particular operating conditions for stopping the engine

Definitions

  • the present invention relates to an air-fuel ratio control system for internal combustion engines and, more particularly, to an air-fuel ratio control system in which the feed-back control of the air-fuel ratio of a mixture supplied to an internal combustion engine is conducted in accordance with a signal from an air-fuel ratio sensor with a heater. Still more particularly, the invention is concerned with an air-fuel ratio control system of the type mentioned above, which is improved to prevent destruction of the air-fuel ratio sensor when the ambient air temperature is low.
  • a feed-back type air-fuel control system which employs an air-fuel ratio sensor (oxygen sensor) in which the output is inverted when the air-fuel ratio changes across the stoichiometric point.
  • an air-fuel ratio sensor oxygen sensor
  • air-fuel control systems have been proposed and actually used in which the air-fuel ratio sensor incorporates an electric heater which heats and activates the sensor.
  • Air-fuel ratio sensors adapted to produce a digital output which changes linearly in response to a change in the air-fuel ratio have also been put into practical use.
  • Such sensor also incorporate electric heaters for the purpose of improving the sensing accuracy and sufficiently activating the sensors.
  • Air-fuel ratio control systems using air-fuel ratio sensors of the types mentioned above are broadly used in various internal combustion engines for the purpose of cleaning exhaust gases, regardless of whether the engines are carbureted or fuel injected.
  • a known air-fuel ratio control system combined with speed-density-type fuel injection and employing an air-fuel ratio sensor adapted to produce a linear output in relation to a change in the air-fuel ratio will be described hereunder by way of example.
  • an internal combustion engine A has an engine proper 1, an intake pipe 2 and a throttle valve 3 disposed in the intake pipe 2.
  • the pressure of the intake air in the intake pipe 2 is sensed by a pressure sensor 4 which delivers the sensing output to an A/D converter 91 of a later-mentioned control device 9.
  • the temperature of the engine proper may be detected by a cooling water temperature sensor (not shown), the output of which also is delivered to the A/D convector 91.
  • the engine speed is sensed by an rpm sensor 5 which produces pulses of a frequency proportional to the engine speed.
  • the output pulses of the rpm sensor are delivered to an input circuit 92 of the control device 9.
  • the control device 9 has an output circuit 96 which delivers a control output in accordance with which a fuel injector 6 operates to inject a fuel into the intake pipe 2.
  • An air-fuel ratio sensor 8 is disposed in an exhaust pipe 7 which is connected to the engine proper 1.
  • the air-fuel ratio sensor 8 is capable of sensing the air-fuel ratio of the mixture fed to the engine through measurement of components of the exhaust gas flowing in the exhaust gas pipe 7.
  • control device 9 receives various data concerning the state of e ngine operation, including the intake air pressure data derived from the pressure sensor 4, engine speed data from the rpm sensor 5 and the air-fuel ratio from the air-fuel ratio sensor 8. Upon receipt of these data, the control device 9 computes the optimum fuel injection rate and controls the duty ratio or the pulse width of the driving pulses for driving the fuel injector 6 in accordance with the thus computed optimum fuel injection rate.
  • the AD converter 91 of the control device 9 is adapted to convert the analog signals such as those derived from the air-fuel ratio sensor 8 and the pressure sensor 4 into digital signals which are delivered to a microprocessor 93.
  • the input circuit 92 of the control device 9 has a function to conduct a level-conversion of the pulse signal derived from the rpm sensor 5.
  • the signal from this circuit 92 also is delivered to the microprocessor 93.
  • the microprocessor 93 computes the amount of fuel to be supplied to the engine proper 1 in accordance with the digital and pulse signals from the AD converter 91 and the input circuit 92, to produce a signal for controlling the duty ratio or the pulse width of the driving pulses for driving the injector 6.
  • the processes to be executed by the microprocessor 93 and other related data are stored beforehand in a read-only memory (ROM) 94, while data obtained in the course of computation are temporarily stored in a random access memory (RAM) 95.
  • ROM read-only memory
  • RAM random access memory
  • the delivery of the output signal from the microprocessor 93 to the fuel injector 6 is conducted through the output circuit 96.
  • the air-fuel ratio sensor 8 has an oxygen pump cell 81, an oxygen battery cell 82, a pair of electrodes 83a, 83b made of a porous material, a diffusion chamber 84, a reference voltage 85, a comparison amplifier 86, a pump driving circuit 87, and a resistor 88 which is used for the purpose of detecting the electric current in the pump cell.
  • Reference numeral 103 denotes an electrical insulator on which is formed a resistor 100.
  • the resistor 100 serves as a heat-generating element.
  • An air gap 102 is formed between the portion of the electric insulator 103 having the resistor 100 and the oxygen battery cell 82.
  • This basic arrangement of the air-fuel ratio sensor 8 is already known from the disclosures of Japanese Patent Laid-Open Nos. 59-19046 and 60-128349.
  • the voltage generated in the oxygen battery cell 82 and the voltage of a reference voltage source 85 which is set, for example, at 0.4V are input to the comparison amplifier 86 so as to be compared with each other.
  • the pump driving circuit 87 is driven to supply an electric current to the oxygen pump cell 81 so as to reduce the offset of the voltage in the oxygen battery cell 82 from the reference voltage to zero, whereby a state of the exhaust gas corresponding to the stoichiometric ratio is obtained in the diffusion chamber 84.
  • the resistor 100 is supplied with an electric current through the output circuit 97 in the control device 9 so as to heat and activate the air-fuel ratio sensor 8.
  • Fig. 7 is a flow chart showing the process of the control performed by the control device 9 shown in Fig. 4.
  • Step S 1 The pulse signal from the rpm sensor 5, representing the rpm Ne of the engine, is read in Step S 1, and the signal from the pressure sensor 4 indicative of the absolute pressure Pb in the intake pipe is read in Step S 2.
  • Step S 3 the basic driving pulse width r0 of the pulses for driving the injector 6 is computed on the basis of the data read in Steps S 1 and S 2.
  • a temperature - compensation may be conducted on the driving pulse width in accordance with the temperature signal derived from the cooling water temperature sensor 10 such that the actual driving pulse width ⁇ o is increased as compared with the computed by the above mentioned formula when the cooling water temperature is low.
  • a target air-fuel ratio (A/F) S is set in Step S 4.
  • the target air-fuel ratio (A/F) S is determined beforehand in such a manner as to optimize the air-fuel ratio for attaining the maximum dynamic performance of the engine while minimizing the fuel consumption under varying engine rpms Ne and the intake pressure Pb, as will be seen from Fig. 8 in which a flow chart (a) shows operation cycle of the engine and in which a flow chart (b) shows the on-off cycle of the heater 100 in the air-fuel ratio sensor 8.
  • the target air-fuel ratio may be determined taking into account also other factors such as the engine temperature and the state of acceleration or deceleration of the engine.
  • Step S 5 The output signal (A/F) R from the air-fuel ratio sensor 8 is read in Step S 5 and, in Step S 6, the deviation of the air-fuel ratio from the target air-fuel ratio, i.e., (A/F)S -(A/F)R, is computed and integrated with a suitable gain.
  • Step S 10 the pulse width r of the injector driving pulses is determined by multiplying the basic pulse width r0 determined in Step S 3 with the correction value I1 determined in Step S 8 or S 9.
  • the described control operation essentially requires that the air-fuel ratio sensor 8 correctly detect momentary changes in the air-fuel ratio and, therefore, the air-fuel ratio sensor has to be sufficiently activated by being heated.
  • exhaust gas temperature is normally so low when the engine is operating under a light load that the air-fuel ratio sensor 8 cannot be sufficiently activated.
  • the known air-fuel ratio control system for internal combustion engines described hereinabove can operate satisfactorily under normal ambient air temperature.
  • a problem is encountered, however, particularly when the ambient air temperature is extremely low, e.g., between 0° and -30°C. Namely, under such low ambient air temperatures, if the engine is stopped before the engine and the exhaust system are completely heated, the moisture contained in the exhaust gas condenses within the exhaust pipe 7 to become water droplets which cling to the air-fuel ratio sensor.
  • the air el ratio sensor 8 has tiny apertures such as the air gap 102 and very small holes formed in the electrodes 83a, 83b. If the engine is left to stand without operating under such cold temperatures, the water droplets clinging to such tiny apertures freeze increasing their volumes to produce mechanical forces which break the cells in the air-fuel ratio sensor 8.
  • an object of the present invention to provide an air-fuel ratio control system for internal combustion engines, which is improved in such a way as to prevent destruction of the air-fuel ratio sensor attributable to freezing of water droplets, thereby overcoming the above-described problems of the prior art.
  • an air-fuel ratio control system for internal combustion engines comprising: an air-fuel ratio sensor mounted in an exhaust pipe of an internal combustion engine and adapted to produce an output indicative of the air-fuel ratio of a mixture supplied to the engine on the basis of the composition of exhaust gases in the exhaust pipe; heating means for heating the air-fuel ratio sensor; an engine operation sensor adapted to sense whether the engine has been stopped; and control means for controlling the heating means such that it is operated for a predetermined time after the engine operation sensor has sensed that the internal combustion engine has been stopped.
  • a temperature sensor for sensing the temperature of the ambient air and/or the internal combustion engine may be provided.
  • the control means is operative for allowing, when the engine has been stopped while the temperature sensed by the temperature sensor is below a predetermined level, the heating means to operate for a predetermined time after the engine operation sensor has sensed that the engine has been stopped.
  • the general arrangement of the air-fuel ratio control system of the present invention is basically the same as that of the known system explained before in connection with Fig. 4, but is distinguished from the described known art in that the arithmetic function of the microprocessor 93 in the control device 9 and the manner of setting of data are changed.
  • the air-fuel ratio control system in accordance with the present invention has additional functions as shown in the flow chart in Fig. 2.
  • the air-fuel ratio control system embodying the present invention has an air-fuel ratio sensor 8 mounted in an exhaust pipe of an internal combustion engine and adapted to produce an output indicative of the air-fuel ratio of a mixture supplied to the engine on the basis of the composition of exhaust gases in the exhaust pipe; heating means 100 such as an electric heater being operable to heat the air-fuel ratio sensor 8 during the operation of the engine; and engine operation sensor 211 adapted to sense whether the engine has been stopped; and control means 212 for controlling the heating means 100 such that it is operated for a predetermined time after the engine operation sensor 211 has sensed that the internal combustion engine has been stopped.
  • heating means 100 such as an electric heater being operable to heat the air-fuel ratio sensor 8 during the operation of the engine
  • engine operation sensor 211 adapted to sense whether the engine has been stopped
  • control means 212 for controlling the heating means 100 such that it is operated for a predetermined time after the engine operation sensor 211 has sensed that the internal combustion engine has been stopped.
  • the air fuel ratio sensor 8 is similar in construction and operation to the one shown in Fig. 5.
  • the control means 212 comprises a timing means which is adapted to allow the heater 100 to operate for a predetermined time after the engine operation sensor 211 has sensed that the engine has been stopped.
  • a timing means may be constructed as software like a control program built in the microprocessor 93 of the control device 9 or as hardware like a timer.
  • Step 200 the engine operation sensor 211 determines whether the engine has been stopped or not, through detection of the state of a key or ignition switch. If the engine has been stopped, the process proceeds to Step 201 in which the timing means 212 for controlling the power supply to the heater 100 is started to operate, as illustrated in the timing charts (a) and (b) of Fig. 3.
  • timing means 212 electric power is supplied from a power source 104 to the electric heater 100 of the air-fuel ratio sensor 8 through the output circuit 97 of the control device 9, as illustrated in the timing chart (c) of Fig. 3, so that the air-fuel ratio sensor 8 is heated.
  • the time set in the timing means 212 is determined beforehand and is long enough to ensure that any wetness on the air-fuel ratio sensor 8 is completely removed by evaporation. For instance, the timing means 212 is set to continue the electric power supply to the heater 100 for several minutes when the engine is stopped.
  • the air-fuel ratio control system of this embodiment has an air-fuel ratio sensor 8 mounted in an exhaust pipe of an internal combustion engine and adapted to produce an output indicative of the air-fuel ratio of a mixture supplied to the engine on the basis of the composition of exhaust gases in the exhaust pipe; heating means 100 such as an electric heater for heating the air-fuel ratio sensor; a temperature sensor 10 for sensing the temperature of the internal combustion engine; an engine operation sensor 211 adapted to sense whether the engine has been stopped; and control means 212 for allowing, when the engine operation sensor 211 has sensed that the internal combustion engine has been stopped while the engine temperature sensed by the temperature sensor 10 is below a predetermined level, the heating means to operate for a predetermined time after the engine operation sensor 211 has sensed that the internal combustion engine has been stopped.
  • heating means 100 such as an electric heater for heating the air-fuel ratio sensor
  • a temperature sensor 10 for sensing the temperature of the internal combustion engine
  • an engine operation sensor 211 adapted to sense whether the engine has been stopped
  • control means 212 for allowing, when
  • control means 212 includes temperature determining means 213 for determining whether the engine temperature sensed by the temperature sensor is below the predetermined level, and a timer 214 adapted to allow, when the engine operation sensor 211 has sensed that the internal combustion engine has been stopped while the engine temperature is judged by the temperature judging means 213 to be below the predetermined level, e.g., 70°C, the heating means to operate for a predetermined time after the engine operation sensor has sensed that the internal combustion engine has been stopped.
  • predetermined level e.g. 70°C
  • Step 200 the engine operation sensor 211 determines whether the engine has been stopped or not, through detection of the state of a key or ignition switch. If the engine has been stopped, the process proceeds to Step 201 in which the temperature determining means 213 determines whether the cooling water temperature is above a predetermined level which is, for example, set at 70°C, by means of the signal derived from the water temperature sensor 10. If the cooling water temperature is below the predetermined level, a timer 214 for controlling the power supply to the heater is started in Step 202.
  • a predetermined level which is, for example, set at 70°C
  • timer 214 electric power is supplied from the power supply 104 to the electric heater 100 in the form of a resistor of the air-fuel ratio sensor 8, through the output circuit 97 of the control device 9 so that the air-fuel ratio sensor 8 is heated.
  • the time set in the timer 214 is determined beforehand and is long enough to ensure that any wetness on the air-fuel ratio sensor is completely removed by evaporation. For instance, the timer 214 is set to continue the electric power supply to the heater for several minutes when the ambient air temperature is low.
  • the engine temperature is determined through detection of the cooling water temperature and, if the engine temperature is below a predetermined level, electric power is supplied to the heater 100 of the air-fuel ratio sensor 8 for a predetermined time after the stop of the engine, thereby to completely evaporate any water content attached to the air-fuel ratio sensor 8.
  • the supply of the electric power to the heater 100 is controlled in accordance with the engine temperature sensed by the cooling water temperature sensor 10, this is not exclusive and the air-fuel ratio control system of the invention may employ a temperature sensor for sensing the ambient air temperature in place of the cooling water temperature sensor 10.
  • the temperature determining means 213 determines is below a predetermined level, e.g., 0°C and, if so , a signal is generated to operate the timer 214 thereby allowing the electric power supply to the heater 100.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
EP19870308674 1986-09-30 1987-09-30 Steuerungssystem des Luft-Kraftstoffverhältnisses für Verbrennungsmotoren Expired - Lifetime EP0262956B1 (de)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
JP233583/86 1986-09-30
JP61233583A JPS6388244A (ja) 1986-09-30 1986-09-30 空燃比制御装置
JP61233581A JPH0617894B2 (ja) 1986-09-30 1986-09-30 空燃比制御装置
JP233581/86 1986-09-30
JP61233582A JPS6388243A (ja) 1986-09-30 1986-09-30 空燃比制御装置
JP233582/86 1986-09-30

Publications (2)

Publication Number Publication Date
EP0262956A1 true EP0262956A1 (de) 1988-04-06
EP0262956B1 EP0262956B1 (de) 1990-05-09

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EP19870308674 Expired - Lifetime EP0262956B1 (de) 1986-09-30 1987-09-30 Steuerungssystem des Luft-Kraftstoffverhältnisses für Verbrennungsmotoren

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EP (1) EP0262956B1 (de)
DE (1) DE3762648D1 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0779426A3 (de) * 1995-12-14 1999-05-19 Toyota Jidosha Kabushiki Kaisha Heizungsregler für einen Luft-Kraftstoffverhältnissensor
WO2005071247A1 (en) * 2004-01-23 2005-08-04 Toyota Jidosha Kabushiki Kaisha Control system for exhaust gas sensor

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4212273A (en) * 1976-10-08 1980-07-15 Hiroyuki Maruoka Air fuel supply system and oxygen sensor therefor
EP0127018A2 (de) * 1983-05-27 1984-12-05 Allied Corporation Aussenluftdruckmessung mit Hilfe eines Krümmerdruckfühlers in einer mikroprozessorgesteuerten Brennkraftmaschine

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4212273A (en) * 1976-10-08 1980-07-15 Hiroyuki Maruoka Air fuel supply system and oxygen sensor therefor
EP0127018A2 (de) * 1983-05-27 1984-12-05 Allied Corporation Aussenluftdruckmessung mit Hilfe eines Krümmerdruckfühlers in einer mikroprozessorgesteuerten Brennkraftmaschine

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, vol. 10, no. 40 (M-454)[2097], 18th February 1986; & JP-A-60 192871 (SUTEKIYO UOZUMI) 01-10-1985 *
PATENT ABSTRACTS OF JAPAN, vol. 7, no. 50 (M-197)[1195], 26th February 1983; & JP-A-57 200 645 (MITSUBISHI DENKI K.K.) 08-12-1982 *
PATENT ABSTRACTS OF JAPAN, vol. 8, no. 216 (M-329)[1653], 3rd October 1984; & JP-A-59 101 561 (MAZDA K.K.) 12-06-1984 *

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0779426A3 (de) * 1995-12-14 1999-05-19 Toyota Jidosha Kabushiki Kaisha Heizungsregler für einen Luft-Kraftstoffverhältnissensor
WO2005071247A1 (en) * 2004-01-23 2005-08-04 Toyota Jidosha Kabushiki Kaisha Control system for exhaust gas sensor
CN100451317C (zh) * 2004-01-23 2009-01-14 丰田自动车株式会社 废气传感器控制系统
US7568477B2 (en) 2004-01-23 2009-08-04 Toyota Jidosha Kabushiki Kaisha Control system for an exhaust gas sensor
US7591259B2 (en) 2004-01-23 2009-09-22 Toyota Jidosha Kabushiki Kaisha Control system for an exhaust gas sensor
US7600507B2 (en) 2004-01-23 2009-10-13 Toyota Jidosha Kabushiki Kaisha Control system for an exhaust gas sensor
US7600508B2 (en) 2004-01-23 2009-10-13 Toyota Jidosha Kabushiki Kaisha Control system for an exhaust gas sensor
US7677231B2 (en) 2004-01-23 2010-03-16 Toyota Jidosha Kabushiki Kaisha Control system for an exhaust gas sensor

Also Published As

Publication number Publication date
DE3762648D1 (de) 1990-06-13
EP0262956B1 (de) 1990-05-09

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