Nippondenso Co., Ltd.

Masahiko Tajima

Toshio Kondo

Akio Kobayashi

Yasuo Sagisaka

Junya Morikawa

Hideaki Norimatsu

Katsuhiko Kodama

Tatsunori Kato

Tomomi Eino

Takehiro Kikuchi

Minoru Hotta

Yoshinori Maegawa

An open/close means M1 opens or closes an EGR passage. An engine load detecting means M2 detects an engine load, such as an intake air amount or an intake air pressure. Either an open. condition or a closed condition of the open/close means M1 is specified as a referential state, while the other is specified as a non-referential state. A memory means M3 memorizes engine loads at the referential state and the non-referential state. A constant acceleration judging means M4 makes a judgement as to whether or not the operational condition of the engine is in a constant accelerating condition. An open/close control means M5 switches the open/close means M1 from the referential state to the non-referential state in response to a constant accelerating condition detected by the constant acceleration judging means M4. An estimating means M8 calculates an estimated engine load to be measured if the open/close means M1 is maintained at the referential state under the continuous constant accelerating condition at the time an actual engine load is detected in the non-referential state, based on a plurality of detection values of the engine load values memorized in the referential state. An abnormality judging means M7 compares the estimated engine load calculated by the estimating means M6 with the actual engine load detected in the non-referential state, thereby making a judgement as to whether the exhaust gas recirculating operation is normal or abnormal.

Exhaust gas recirculation system

An air-fuel ratio control apparatus for an internal combustion engine for learning and controlling an air-fuel ratio accurately even during execution of purging of evaporated fuel. The evaporated fuel generated in a fuel tank is adsorbed to a canister, and the adsorbed fuel is evaporated and purged together with air to the intake side of the internal combustion engine through a purge valve. During normal purge rate control by the purge valve, air-fuel ratio feedback values detected by an oxygen sensor are averaged, and the concentration of the evaporated fuel taken into the internal combustion engine through the purge valve is detected by the deviation from a stoichiometric air-fuel ratio 1 of the averaged value and the purge rate. Further, after the lapse of a predetermined period of time after purging is started, air-fuel ratio learning values are renewed in accordance with the air-fuel ratio feedback value and stored in a RAM.

Air-fuel ratio control apparatus of internal combustion engine

The amount of fuel supplied to an internal combustion engine is determined by controlling the opening interval of each fuel injection valve by correcting a standard interval obtained from the amount of intake air and engine speed by first to third correction factors. The first correction factor is dependent on coolant and intake air temperatures, while the second correction factor is dependent on a gas sensor output indicative of the air/fuel ratio of the mixture supplied to the engine. A plurality of third correction factors is provided for different amounts of intake air. Some of the third correction factors corresponding to intake air amounts at which the engine has been operated, are corrected in accordance with the value of the second correction factor. The state of correction is detected and when third correction factor has been corrected in the same direction by a relatively large amount, all of the third correction factors, which have been stored in a memory, are uniformly modified to renew the stored data.

Method and apparatus for controlling air/fuel ratio in internal

The basic fuel injection amount determined in accordance with the rpm and the amount of air drawn into an engine is corrected by first, second and third compensation amounts determined in accordance with the engine operating conditions. The second compensation amount is varied by a predetermined value in response to the output of an O.sub.2 sensor at intervals of a predetermined time. The third compensation amount is read out from the location of a non-volatile memory addressed in accordance with the engine rpm and the intake air amount, varied by another predetermined value at intervals of another predetermined time in accordance with the value of the second compensation amount and stored again in the location from which it was read out. Before starting the compensation of the fuel injection amount, the particular bit pattern stored in the non-volatile memory is checked so as to self-check the third compensation amount data in the non-volatile memory.

Air-fuel ratio control apparatus

The air-fuel ratio of a mixture to be supplied to an engine is corrected by a microcomputer in accordance with integrated data produced by the process of integration performed in response to the output signal of an air-fuel ratio sensor for sensing the composition of exhaust gases from the engine and engine condition correction data corresponding to the then existing engine operating conditions. The necessary engine condition correction data are stored in the form of a map in a nonvolatile memory in accordance with the engine operating conditions as parameters. If, for example, any abnormal condition such as an abnormal rise in the temperature of a catalytic converter occurs, all the engine condition correction data in the nonvolatile memory are reset to a predetermined value.

Air-fuel ratio controlling method and apparatus therefor

An apparatus for controlling an air-fuel ratio of a combustion engine with a memory device for storing correct values for air-fuel control in accordance with an intake condition of said combustion engine and a rotation speed of the same. In the apparatus, an air-fuel ratio represented by the exhaust gas composition of the internal combustion engine is sensed and the sensed value is integrated. When the integrated value from the integrator fails within a predetermined range of values, one of the correction values for the air-fuel ratio control is corrected in accordance with a current condition of the internal combustion engine. When the integrated value falls outside the predetermined range, the correction values are replaced by a predetermined reference value and an air-fuel ratio of mixture supplied to the combustion engine is controlled in accordance with the correction values for the air-fuel ratio stored.

Air-fuel ratio control method and its apparatus

A method for preventing overheating of an exhaust purifying device by means of an air-flow sensor for sensing the amount of air drawn into an engine to generate an analog voltage corresponding to the amount of air drawn, an intake-air temperature sensor for sensing the temperature of the air drawn into the engine to generate an analog voltage corresponding to the temperature of the air drawn, a water temperature sensor for sensing the temperature of the engine cooling water temperature to generate an analog voltage corresponding to the cooling water temperature, a temperature sensor mounted on a converter, an RPM sensor for sensing the rotational speed of the engine to generating a pulse signal of a frequency corresponding to the engine speed, and a circuit responsive to the detection signals from the sensors for computing the desired amount of fuel injected. The computing circuit controls the ON and OFF periods of fuel injection valves to adjust the fuel injection quantity. When the exhaust temperature exceeds a predetermined value, the air-fuel ratio is compensated for the then current engine operating conditions and the compensation amount is then stored in a memory, whereby each time the same engine operating conditions are repeated, the air-fuel ratio is compensated in accordance with the stored compensation data to thereby prevent overheating of the exhaust purifying device.

Method for preventing overheating of an exhaust purifying device

An air-fuel ratio control system comprises a first oxygen concentration detector arranged upstream of a three-way catalyst for purifying the exhaust gas in the exhaust system of an internal combustion engine, a second oxygen concentration detector arranged downstream of the three-way catalyst, a discrimination circuit for detecting and discriminating a specific operating condition of the internal combustion engine in response to a signal representing operating factors of the internal combustion engine such as the amount of intake air and vehicle speed, and a change-over circuit impressed with the signals from the first and second oxygen concentration detectors. The change-over circuit produces selectively the detection signal of the second oxygen concentration detector in response to the output signal of the discrimination circuit only when the discrimination circuit detects a predetermined operating condition of the internal combustion engine, and the detection signal of the first oxygen concentration detector when the internal combustion engine is under the other operating conditions.

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Takahama, Japan

Masahiko Tajima