Abstract: An engine control system having an oxygen density sensor arranged in an intake system at a position downstream of a throttle valve for detecting the amount of air newly introduced into the engine. The sensor is a limit electric current detection type capable of detecting a continuously changing density of the oxygen. An amount of fuel to be injected is calculated in accordance with the output level of the sensor by using mapped data of the output level of the sensor signal. A precise detection of new air is made possible while maintaining the advantages of the known D-J system. An ignition timing also may be calculated by the signal from the oxygen sensor.

Abstract: A fuel injection system for an internal combustion engine wherein an oxygen sensor for detecting a limit electric current is employed for providing a signal indicating an oxygen partial pressure in the gas introduced into the engine. The sensor detects an amount of air newly introduced into the engine. In addition to a map for calculating a basic fuel injection amount from the oxygen partial pressure, a second map is provided for calculating the basic fuel amount from a parameter such as a degree of opening of the throttle valve. A degree of activation of the oxygen sensor is determined by detecting the impedance of the sensor. When it is determined that the oxygen sensor is not activated, the second map is employed in place of the first map to calculate the basic fuel amount based on the degree of opening of the throttle valve.

Abstract: A control device for an internal combustion engine having an oxygen sensor, and calculation means for calculating a weight of oxygen fed to the internal combustion engine. The oxygen sensor outputs a signal corresponding only to a density of oxygen contained in intake gas fed to the engine. The oxygen sensor has a diffusion layer having pores through which oxygen molecules pass, the pores having a diameter less than or equal to the mean free path of the oxygen molecules contained in the intake gas.

Abstract: An engine control system having an oxygen density sensor arranged in an intake system at a position downstream of a throttle valve for detecting the amount of air newly introduced into the engine. The sensor is a limit electric current detection type capable of detecting a continuously changing density of oxygen. An amount of fuel to be injected is calculated in accordance with the output level of the sensor by using mapped data of the output level of the sensor signal. The sensitivity of the sensor is detected and multiplied by the output value of the sensor for obtaining a precise oxygen partial pressure. Instead of calculating the basic fuel amount from the output level of the oxygen density sensor, a normal intake pressure sensor with an intake pressure-engine speed map can be employed. In the latter case, the oxygen partial pressure from the oxygen density sensor is used for correcting the calculated basic fuel amount. The sensitivity of the sensor is also corrected.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side air-fuel ratio sensor and the downstream-side air-fuel ratio sensor. The adjustment of the air-fuel ratio by the downstream-side air-fuel ratio sensor is stopped when the engine is in a predetermined state.

Abstract: In a double air-fuel ratio sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust passage, the actual air-fuel ratio is adjusted in accordance with an air-fuel ratio correction amount calculated by using the output of the upstream-side air-fuel ratio sensor and an air-fuel ratio feedback control parameter such as delay time periods, skip amounts, or integration amounts calculated by using the output of the downstream-side air-fuel ratio sensor, and the calculation of the air-fuel ratio feedback control parameter is prohibited when the downstream-side air-fuel ratio sensor is in an abnormal state.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, a delay operation is performed upon the output of the downstream-side air-fuel ratio sensor, so that the actual air-fuel ratio is adjusted in accordance with the output of the upstream-side air-fuel ratio sensor and the delayed output of the downstream-side air-fuel ratio sensor.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an air-fuel ratio correction amount is gradually changed in accordance with the output of the upstream-side air-fuel ratio sensor, and the actual air-fuel ratio is adjusted in accordance with the air-fuel ratio correction amount. The gradual-change speed of the air-fuel ratio correction amount is changed in accordance with the output of the downstream-side air-fuel ratio sensor.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an air-fuel ratio correction amount is remarkably changed when the output of the upstream-side air-fuel ratio sensor is switched from the lean side to the rich side or vice versa, and the actual air-fuel ratio is adjusted in accordance with the air-fuel ratio correction amount. The remarkable-change speed of the air-fuel ratio correction amount is changed in accordance with the output of the downstream-side air-fuel ratio sensor.

Abstract: Pulse current having a certain cycle is supplied to an electric heater in an oxygen sensor for exhaust gas. Duty ratio of this pulse current is controlled in relation to the amplitude of voltage and current applied to the heater to thereby maintain power consumption of the heater per unit time at a constant one. Also this duty may be corrected on the basis of parameters for running an internal combustion engine.

Abstract: In a method of and system for lean-controlling an air-fuel ratio in an electronically controlled engine, wherein the air-fuel ratio is feedback-controlled to the lean side from the stoichiometric air-fuel ratio in accordance with an output from a lean sensor generating an output signal substantially proportional to the concentration of oxygen in the exhaust gas, when it is necessary to vary a target air-fuel ratio, a target control value of an output from the lean sensor is corrected in accordance with the required variation value and the air-fuel ratio is feedback-controlled whereby the output from the lean sensor can become the corrected target control value, so that satisfactory feedback control of the air-fuel ratio can be effected even when the target air-fuel ratio is varied to a value other than the normal value.

Abstract: An output voltage from an O.sub.2 sensor is intermittently sampled and the sampled voltage is converted into a binary signal. The binary signal is applied to an electrical digital computer, and therein the following operations are carried out. First, the maximum value and minimum value of the applied binary signal are detected, then the difference between the maximum and minimum values and the sum of the maximum and minimum values are calculated. A reference value is calculated using the calculated difference and sum and the minimum value from a predetermined algebraic function. Thereafter, the applied binary signal is compared with the calculated reference value to generate a binary signal indicative of the comparison result. Then, the air-fuel ratio of the engine is adjusted in response to this binary signal calculated by the digital computer.

Abstract: An output voltage from an O.sub.2 sensor is intermittently sampled and the sampled voltage is converted into a binary signal. The binary signal is applied to an electrical digital computer, and therein the following operations are carried out. First, the maximum value or the maximum and minimum values of the applied binary signal are detected, then a reference value is calculated using the maximum value or the maximum and minimum values from a predetermined algebraic function. Thereafter, the applied binary signal is compared with the calculated reference value to generate a binary signal indicative of the comparison result. Then, the air-fuel ratio of the engine is adjusted in response to this binary signal calculated by the digital computer.

Abstract: An output voltage from an O.sub.2 sensor is intermittently sampled and the sampled voltage is converted into a binary signal. The binary signal is applied to an electrical digital computer, and therein the following operations are carried out. First, the maximum and minimum values of the applied binary signal are detected, then the difference between the detected values is calculated. Thereafter, the calculated difference is compared with a predetermined value to generate a binary signal indicative of the comparison result. The air-fuel ratio feedback control responsive to the applied binary signal is executed when the binary comparison result signal indicates that the calculated difference is larger than or equal to a predetermined value.