Abstract: The invention relates to a control systems for feedback control of the air/fuel ratio in an internal combustion engine, e.g., an automotive engine, which uses a three-way catalyst to purify the exhaust gas, by using an exhaust sensor to detect actual values of air/fuel ratio in the engine. The control system has the function of varying the target value of air/fuel ratio according to operating conditions of the engine. The target value becomes super-stoichiometric during steady-state operation of the engine and changes to a lower value optimum for the activities of the three-way catalyst, such as the stoichiometric value, under predetermined transient conditions of the engine. At the start of such a change in the target value, the control system functions so as to intentionally deviate the air/fuel ratio from the value optimum for the three-way catalyst in a direction away from the target value immediately before the change.

Abstract: The throttle valve position is sensed and the effective cross sectional area of the induction passage determined via table look up. The value thus derived is divided by the engine speed. A basic air induction quantity is then determined via table look up and subsequently modified using a correction coefficient to allow for the effect of engine speed on the amount of air inducted into each cylinder. The effect of injector position (viz., MPI/SPI) is taken into consideration and values suited for both generated in given embodiments. In the event that the maximum induction vacuum is limited by a BCD valve or the like, an embodiment anticipates the change in induction characteristics based on the engine speed.

Abstract: The throttle valve position of an engine is sensed and the effective cross sectional area of the induction passage is determined via table look-up. The table is recorded in terms of three parameters. The value thus derived is divided by the engine speed of alternatively a product of the engine speed and the engine displacement. A basic air induction quantity is then determined via table look-up and is subsequently modified using a correction coefficient to allow for the effect of engine speed on the same. The effect of injector position (viz., multi-point injection/single point injection) and/or the provision of a swirl control valve can be additionally taken into consideration via the use of suitable algorithms or additional two and three parameter system tables. If an idle control by-pass passage is provided, the effect of the opening degree is considered when determining the effective cross-section of the induction passage.

Abstract: The amount of air being inducted into the cylinders of an internal combustion engine is detected and a signal indicative thereof is sampled at a predetermined intervals. The difference between two sampled values is used with the time required for a single induction phase to be carried out, to predict the total amount of air which will be inducted into each cylinder. Utilizing this approximation the amount of fuel which should be injected or otherwise supplied to the engine can be accurately determined and thus enable accurate real-time cycle to cycle A/F control.

Abstract: A back-up system for an engine coolant temperature sensor detects deviation of the output of the temperature sensor from its designed output range to produce a fault signal. In response to the fault signal, an engine control system derives the engine coolant temperature indirectly from other engine conditions. This derivation is based on two facts: (1) the amount of fuel required to start the engine is related to engine temperature, and (2) since the calorific value of a given engine is essentially constant, the rate of increase of engine temperature is related to the integrated number of engine revolutions. Thus, when the engine is to be started, engine temperature can be derived by gradually increasing the fuel supply quantity from a minimal initial value until the engine is able to start to determine the required fuel supply quantity. Thereafter, the derived temperature value can be updated as a function of total engine revolutions.

Abstract: In a closed loop air-fuel mixture control system for carburetor-equipped internal combustion engines, an exhaust gas sensor provides a feedback signal to a control unit where the signal is modified to meet the control characteristics of the closed loop. The modified feedback signal is converted into digital pulses whose width varies with the amplitude of the feedback signal. Additional air is supplied to the engine through an air bleed in accordance with the magnitude of the analog feedback signal to provide a coarse control of air-fuel ratio and in response to the digital pulses to provide a fine control of the ratio. The mixture is controlled in a wide range of ratios to eliminate the need for calibration which would be required for fitting the closed loop system to the time-varying characteristics of individual carburetors.

Abstract: With respect to an internal combustion engine equipped with a carburetor and a catalytic converter which requires to feed the engine with a stoichiometric air/fuel mixture, the control system is for regulating the air/fuel ratio produced in the carburetor and comprises an auxiliary air admitting passage connected to the fuel discharge passage of the carburetor in addition to a usual air bleed passage for the fuel discharge passage, an electromagnetic valve for controlling the admission of air into the auxiliary passage, an oxygen sensor disposed in the exhaust system upstream of the catalytic converter, and a control circuit for producing continual pulses at a frequency between 5 and 100 Hz. The widths of the individual pulses are increased gradually while the output of the oxygen sensor indicates the air/fuel ratio being below the stoichiometric ratio, and vice versa.