Abstract: A reference signal with which the output of a gas sensor is compared is produced by detecting the maximum and minimum values of the output of the gas sensor and adding via a voltage divider these values to each other. The variation of the reference signal may be limited with predicted maximum and minimum values of the output of the gas sensor. The reference signal produced in such a manner may be utilized for disabling and reactivating the feedback control.

Abstract: Emission control apparatus for internal combustion engine includes an exhaust composition sensor to sense the mixture ratio, a circuit for clamping the mixture ratio to a predetermined constant value to prevent the mixture from becoming too rich or too lean when a failure should occur in the control loop, for example, in the exhaust composition sensor fail and a circuit for interrupting the clamping circuit when the engine operating condition is such that the sensor is caused to produce low voltage signals although the sensor is functioning properly.

Abstract: The variation range defined between the maximum and the minimum output voltages of a gas sensor in the exhaust passage is detected and compared with a reference signal which can have hysterisis characteristics. Engine operational parameters are utilized to disable and/or reactivate the system as well as the sensed sensor response, while the air-fuel ratio can be arbitrarily varied to test if the sensor is below an effective working temperature and reactivate the system.

Abstract: In a mixture control system having an exhaust gas sensor located in an exhaust system of an internal combustion engine for controlling the air-fuel ratio of the mixture supplied to the engine, a detection system for detecting when the temperature of the exhaust gas sensor is within its normal operating range. A deviation signal is derived from the exhaust gas sensor to represent the deviation of the air-fuel ratio within the exhaust system from a desired air-fuel ratio. The peak value of the deviation signal is detected and stored in a storage circuit and compared with a threshold which represents the normal operating temperature of the exhaust gas sensor to provide a disabling signal for the mixture control system to suspend feedback control operation when the temperature of the sensor falls below its normal operating temperature.

Abstract: A control means is provided in an electronic closed loop air-fuel ratio control system for use with an internal combustion engine, which means controls a time constant of an integrator or a proportional constant of a proportional element of the system so as to optimally control the air-fuel ratio.

Abstract: Emission control apparatus for internal combustion engines is provided with a sensor for detecting the concentration of a particular exhaust composition in the emissions from the engine. A signal indicating the deviation of the mixture ratio from a controlled point is generated by comparing the output from the sensor with a reference level, the signal being modified in amplitude according to a predetermined control characteristic and used to regulate the air-fuel mixture ratio at the desired control point. The varying magnitude of the sensed concentration is smoothed into a signal of slowly varying magnitude which is used to control the reference level so that error introduced into the deviation indicating signal due to the change with time in the output performance of the exhaust composition sensor is self-compensated. A level sensor is provided to detect when the reference level reaches an end of the control range to change the operating mode of the engine from closed-loop to open-loop mode.

Abstract: An exhaust gas sensor is provided to generate a signal representing the air-fuel ratio within the exhaust system. The deviation of the air-fuel ratio from the average value of the sensor output is detected by a comparator. The time integral value is momentarily offset when the sensor reaches its operating temperature range so that the output from the comparator takes a definite value for quickly starting closed control operation.

Abstract: A closed-loop emission control apparatus for internal combustion engines includes exhaust composition sensor for feedback control of the air-fuel mixture. When the temperature in the exhaust passage is lower than the operating temperature of the sensor, control is switched to an open-loop mode. The feedback control signal is fluctuated above and below a predetermined DC bias at periodic intervals during the open-loop mode to switch the control to the closed-loop mode in a minimum transition time as soon as the sensor's temperature condition warrants feedback control.

Abstract: In a closed-loop mixture control system for internal combustion engines, the concentration of an exhaust composition contained in the emissions from the engine is compared with a predetermined value in a comparator to determine whether the fuel quantity is to be corrected in a direction to increase it or decrease it. The rate of change of the correction is controlled in response to a sensed acceleration or deceleration of the engine for a small duration of time to compensate for the error arising from the transport delay time of the engine at the instant of the acceleration or deceleration.

Abstract: 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.

Abstract: In a feedback control system for maintaining the air fuel ratio of a combustible mixture fed to an internal combustion engine at a preset ratio based on a feedback signal representing the concentration of a certain component of the exhaust gas, a control signal producing circuit is provided with a sub-system for holding the control signal constantly at a preset level for a predetermined amount of time immediately after the start of the fuel feed to the engine in order to prevent an unintentional lowering of the air-fuel ratio due to a delay in the development of the feedback signal from the start of the fuel feed.

Abstract: In an electronic closed loop control system for controlling the air-fuel ratio of an air-fuel mixture fed to an internal combustion engine to an optimum, the frequency of a dither signal is discretely or continuously changed to change a repetition rate of a pulsating signal in order to prevent engine vibration discomfortable to a driver, the pulsating signal being applied to at least one electromagnetic valve provided for regulating the air-fuel ratio of the air-fuel mixture.

Abstract: A closed-loop mixture control system for an internal combustion engine includes an exhaust composition detector to provide information on the air-fuel ratio of the mixture to be controlled and a circuit arrangement which clamps the system to a rich mixture ratio when the operating characteristic of the composition detector becomes abnormal due to either an open or short circuit condition.

Abstract: In a closed loop air fuel ratio control system, a throttle position detector senses full throttle operation. Means are provided to disable or clamp the closed loop to a minimum control level to permit reduction in the air fuel ratio below the stoichiometric value. The engine is allowed to operate with increased fuel to give more output power than is provided by the stoichiometric air fuel ratio.

Abstract: A closed-loop mixture control system for an internal combustion engine comprises an electronic control section and an electromechanical section comprised of the engine, an air-fuel metering system and an exhaust composition sensor. The system further comprises a first diagnosis circuit for testing the electromechanical section by application of a recurrent series of binary signals to the metering system, and second and third diagnosis for circuits for testing the function of the electronic control section by application of staircase waveform signal or a train of variable width pulses selectively to the input of the control section. The applied test signals are received by the respective diagnosis circuits to check the performance of the control loop.

Abstract: A control point of a closed loop mixture control system for an internal combustion engine is varied by extending the duration of a signal representative of the deviation of air-fuel ratio from a preset value, or by alternately supplying an engine speed representative pulse sequence in opposite polarities to a first and a second output terminal. An integrator is connected to respond to the duration-extended deviation signal or connected to the first and second output terminals to effect integration of the alternatively supplied, opposite-polarity pulses to generate a stepwise voltage waveform. The integrator output is used as a feedback control signal which fluctuates about a level differing from the present value to shift the control point of the closed loop corresponding to said difference.

Abstract: A closed-loop mixture control system for an internal combustion engine comprises an exhaust composition sensor, a comparator for comparing the signal derived from the sensor with a reference point to determine whether the air-fuel ratio of the mixture is above or below a desired value, and a sample-and-hold circuit for sampling the comparator output at intervals equal to or longer than the transport delay time of the engine and holding the sampled signals until the next sampling occurs. The output from the sample-and-hold circuit is connected to a controller for proportional amplification to vary the fuel quantity proportionally to the input signal applied thereto. Preferably, the system includes an analog shift register into which is serially clocked the output from the sample-and-hold circuit synchronously with the sampling frequency and then clocked out in parallel form to a weighting network before amplification by the controller.

Abstract: A differential signal generator receives an exhaust gas sensor signal and a reference signal, one of which is discretely or continuously modified by an engine temperature sensor signal, to generate a differential signal. This signal is applied to an air to fuel ratio control means to expedite a cold engine start.

Abstract: A closed-loop mixture control system for an internal combustion engine of a roadway vehicle includes a vehicle start sensor and a voltage sensor to determine whether the fuel quantity at the instant the vehicle is started from at rest is below a predetermined value. When the signals from both sensors occur simultaneously the control voltages instantly varied to increase the fuel quantity.

Abstract: Apparatus for controlling air-fuel mixture applied to internal combustion engines comprises an exhaust composition sensor providing an electrical signal representative of the concentration of a composition of the exhaust gases, an integral controller receptive of the electrical signal to generate a correction signal for the air-fuel mixing and proportioning device to control the air-fuel ratio at a desired value. An engine condition sensor is provided to detect transient engine operating conditions to generate a control signal which is used to maintain the output voltage of the integral controller at a predetermined constant value so that the voltage swing during vehicle acceleration or deceleration is held within a minimum range.