Abstract: An air-fuel ratio control system for an internal combustion engine mounted on a vehicle with a transmission, including an oxygen concentration sensor producing an output signal whose level is substantially proportional to an oxygen concentration of the exhaust gas, effects a feedback control of the air-fuel ratio of mixture to be supplied to the engine toward a target value determined on the basis of various parameters of the engine operation and corrected in response to a magnitude of atmospheric pressure, so that the higher a shift position of the transmission gear is, the leaner the target air-fuel ratio becomes. Thus, the fuel consumption in a light load operating condition of the engine is decreased and the driveability of the vehicle is improved.

Abstract: A method of indicating when a shift operation of a manual gearbox is to be preformed includes a step for comparing a detected vehicle speed with a reference vehicle speed which is determined and changed on the basis of a detected engine operational parameter and a step for indicating that the shift operation should be performed on the basis of a result of the comparison. The reference vehicle speed is corrected to a lower speed in response to an increase of a total running time of the vehicle, thereby to maintain the driveability of the vehicle when the running time of the vehicle is short.

Abstract: A device for detecting the air-fuel ratio of an engine by measuring an oxygen concentration of the exhaust gas by means of an oxygen sensor including an oxygen pump and a cell element for measuring the oxygen concentration ratio, comprising an air-fuel ratio detecting circuit which reads the output signal of the oxygen sensor and effects the detection of the air-fuel ratio when TDC signal has been produced, depending upon the operation of the engine, and a time previously set by a timer has passed.

Abstract: A method of controlling an oxygen concentration sensor of the type having oxygen pump and sensor cell elements spaced from each other to form a gap or a restricted region both of which are to be placed in some gases containing an oxygen component, and a heater element for heating said oxygen pump and sensor cell elements under energization of a heater current supplied thereto.A pump current is supplied to the oxygen pump element as long as the heater current is supplied to the heater element. However, the initiation of the supply of the pump current is somewhat delayed at the initial stage of the supply of the heater current in order to avoid incorrect operation due to the unstable cool state of the sensor, and to present possible flow of excessive pump current through the pump element which would cause deterioration of the oxygen pump element.

Abstract: A device for detecting the air-fuel ratio of an engine by measuring the oxygen concentration of the exhaust gas by means of an oxygen sensor including an oxygen pump and a cell element for measuring the oxygen concentration ratio, comprising a filter circuit for smoothing the output signal of the oxygen sensor, said filter circuit having a time constant which is variably set so that it is in proportional relation to the number of revolutions per units of time of the engine.

Abstract: An oxygen concentration sensing apparatus includes an oxygen pump element and a sensor cell element with a pair of electrodes respectively, being disposed to face each other, to form a restricted region between them, and a current source for supplying a pump current across the electrodes the oxygen pump element. A limit voltage is adjustably set in response to a voltage across the electrodes of the oxygen pump element, and the pump current supplied to the oxygen pump element is reduced when a voltage generated across the electrodes of the sensor cell element has exceeded the limit voltage.

Abstract: An air intake side secondary air supply system for an internal combustion engine having an air intake side secondary air supply system includes an oxygen concentration sensor, and controls a duty ratio of opening and closing of an open/close valve disposed in the air intake side secondary air supply passage by determining a valve open period within each duty cycle of control operation in accordance with a result of comparison between the level of the output signal of the oxygen concentration sensor and a level corresponding to a target air-fuel ratio. The duty ratio of opening and closing of the open/close valve is maintained within a predetermined duty ratio range so as to improve effectiveness of the control of the secondary air supply as well as to avoid the generation of over lean or over rich mixture.

Abstract: A method for directing an up shift operation for a vehicle having an engine and a manual transmission generates a direction of an up-shift operation when the vehicle speed exceeds a reference speed determined for each gear position. The reference speed of a medium speed gear is varied according to the degree of acceleration at the time of the previous up-shift operation. If the up-shift operation from a low speed gear to the medium speed gear is effected while the vehicle is not accelerating rapidly, the reference speed for an up shift operation from the medium speed gear is lowered. Further, if a cruising state of the vehicle with the medium speed gear after the acceleration is continued for more than a predetermined time period, the reference speed for an up-shift operation from the medium speed gear is also lowered.

Abstract: Method for controlling an oxygen concentration sensor for sensing an oxygen concentration in an exhaust gas of an internal combustion engine, which sensor includes an oxygen pump element and a heater element, comprises steps for controlling a pump current and a heat current control in response to a result of a detection of engine load. When the engine is operating in a predetermined high load range, the supply of the pump current to the oxygen pump element is stopped, and the heat current to the heater element is reduced when the engine operation in the high load range has continued for more than a predetermined time period. The heater current to the heater element is stopped when the engine load is in a first predetermined load range, and when the engine operation in a second load range which is lighter than the first load range has continued for a predetermined time period.

Abstract: An air intake side secondary air supply system for an internal combustion engine having an air intake system using a carburetor and an air intake side secondary air supply passage leading to the downstream of the carburetor, includes an oxygen concentration sensor producing an output signal whose level is substantially proportional to an oxygen concentration of the exhaust gas. A control means for controlling a duty ratio of opening and closing of an open/close valve disposed in the air intake side secondary air supply passage in accordance with a result of comparison between the level of the output signal of the oxygen concentration sensor and a level corresponding to a target air-fuel ratio. The target air-fuel ratio is up-dated in response to at least two parameters indicative of the engine operation.

Abstract: An air intake side secondary air supply system for an internal combustion engine including an open/close valve disposed in an air intake side secondary air supply passage and an oxygen concentration sensor producing an output signal whose level is substantially proportional to an oxygen concentration of the exhaust gas, executes a duty ratio control of the open/close valve for a feedback control of the air fuel ratio of mixture to be supplied to the engine. When the air/fuel ratio has changed from rich to lean with respect to a target air/fuel ratio, a correction value for reducing the valve open period during the air/fuel ratio is detected to be lean, is increased. On the other hand, when the air/fuel ratio has changed from lean to rich with respect to the target air/fuel ratio, a correction value for increasing the valve open period during the air/fuel ratio is detected to be rich, is increased.

Abstract: An oxygen concentration sensing device for use in an air-fuel ratio control system of an internal combustion engine includes a pair of solid electrolyte members having oxygen ion permeability which are disposed in the exhaust gas of the engine and arranged to face each other forming a predetermined gap portion between them. Each of the solid electrolyte members is provided with a pair of electrodes. One of the solid electrolyte members is operative as an oxygen pump element when a predetermined constant electric current is supplied across the electrodes thereof. An electric potential developed across the electrodes of the other one of the solid electrolyte members operative as a cell element is supplied to a comparing means in which the input signal from the solid electrolyte member is compared with a predetermined reference potential and a result of comparison is provided as an oxygen concentration detection signal.

Abstract: An air intake side secondary air supply system for an internal combustion engine has an air intake system using a carburetor and an air intake side secondary air supply passage leading downstream of the carburetor. The passage includes an oxygen concentration sensor producing an output signal whose level is substantially proportional to an oxygen concentration of the exhaust gas. A control means for controlling a flow control valve is disposed in the air intake side secondary air supply passage and operates in accordance to the output signal of the oxygen concentration sensor. In a variation of the invention, the feedback control of air-fuel ratio using the output signal of the oxygen concentration sensor is effected only when the engine operational state is in a predetermined operational region.

Abstract: An air-fuel ratio control system for an internal combustion engine, including an oxygen concentration sensor producing an output signal whose level is substantially proportional to an oxygen concentration of the exhaust gas, effects a feedback control of the air-fuel ratio of mixture to be supplied to the engine toward a target value determined on the basis of various parameters of the engine operation and corrected in response to a magnitude of atmospheric pressure, so that the target air-fuel ratio is made lean as the magnitude of the atmospheric pressure decreases. Thus, the reduction of the engine output power and the increase of the fuel comsumption which have been encountered in conventional systems are prevented.

Abstract: An air/fuel ratio control system for an internal combustion engine provides a mixture leaner than a predetermined reference value when a detected engine load is in a light load range. In order to produce a required engine power during a transitional period, the system detects the speed of variation of an operating parameter used for the calculation of air/fuel ratio and controls the air/fuel ratio toward the reference level even though the magnitude of the detected engine load is in the light load range. Preferably, an EGR rate is also made smaller upon occurrence of a rapid change of the operating parameter so as to prevent the power down of the engine during the transitional period.

Abstract: An oxygen concentration sensing device and an air/fuel ratio control system for an internal combustion engine which include a pair of solid electrolyte members having oxygen ion permeability which are arranged to face each other to form a restricted region between them. One of the solid electrolyte members is operative as an oxygen pump element when a pump current is supplied across the electrodes thereof. The sensing device is provided with a current supply part including a limit command circuit which generates a current stop command signal when the magnitude of the pump current exceeds a reference limit level. With the current stop command signal, the supply of the pump current is stopped so as to prevent an overcurrent to the oxygen pump element. The air/fuel ratio control system includes an air/fuel ratio detection part and an air/fuel ratio control part operated by an air/fuel ratio detection signal.