Abstract: An air/fuel ratio control system controls the supply of fuel to an internal combustion engine to achieve a target air/fuel ratio, based on the output of an air/fuel ratio sensor. The system may determine whether there is an abnormality in the air/fuel ratio sensor based on a comparison between a change of an air/fuel ratio correction coefficient, used to drive the air/fuel ratio to the target value, and a change of the target air/fuel ratio if the target air/fuel ratio has sharply changed.

Abstract: An oxygen concentration detecting apparatus precisely and easily performs diagnosis of a limit current type oxygen sensor. The limit current type oxygen sensor has an oxygen concentration detecting element for outputting limit current proportional to the oxygen concentration and a heater for heating the detecting element. A CPU of a microcomputer controls energization of the heater to activate the oxygen sensor. The CPU calculates element resistance based on the voltage applied to the oxygen sensor and the current detected in the sensor. In a sensor diagnosis routine, the CPU determines whether preconditions for the diagnosis have been met. If all the preconditions have been met, the CPU executes the diagnosis. That is, the CPU determines whether the element resistance is within a predetermined range. If it is below the range, the CPU determines that the sensor has high element temperature abnormality.

Abstract: A sensing element of an oxygen sensor is controlled to keep a target impedance for maintaining activation temperature of the oxygen sensor. As the sensing element deteriorates, its internal impedance increases and power supply to a heater for heating the sensing element increases. The oxygen sensor temperature rises excessively above an activation temperature. To restrict excessive temperature rise, the target impedance is altered when the supply power to the heater exceeds a predetermined reference. The target impedance may be increased with increase in the power supply to the heater. Alternatively, the heater supply power is limited to a predetermined maximum for restricting excessive temperature rise.

Abstract: An air-fuel ratio control using an A/F sensor which outputs a current representing an air-fuel ratio in response to a voltage applied thereto. If the A/F sensor is still in a state prior to activation and the actual air-fuel ratio is different from an air-fuel ratio represented by a current of the sensor in the state prior to activation when the engine is started, that is, if the air-fuel ratio is put on the rich side by an increased amount of fuel injected at a start of an internal combustion engine at a low temperature or other causes, for example a CPU employed in an ECU, determines whether the difference between the .lambda.-conversion value of the current of the A/F sensor and a target air-fuel ratio is equal to or greater than a predetermined value. If the determination is YES, a feedback control of the air-fuel ratio is started.

Abstract: An air/fuel ratio control system controls the supply of fuel to an internal combustion engine to achieve a target air/fuel ratio, based on the output of an air/fuel ratio sensor. The system may determine whether there is an abnormality in the air/fuel ratio sensor based on a comparison between a change of an air/fuel ratio correction coefficient, used to drive the air/fuel ratio to the target value, and a change of the target air/fuel ratio if the target air/fuel ratio has sharply changed.

Abstract: A sensing element of an oxygen sensor is controlled to keep a target impedance for maintaining activation temperature of the oxygen sensor. As the sensing element deteriorates, its internal impedance increases and power supply to a heater for heating the sensing element increases. The oxygen sensor temperature rises excessively above an activation temperature. To restrict excessive temperature rise, the target impedance is altered when the supply power to the heater exceeds a predetermined reference. The target impedance may be increased with increase in the power supply to the heater. Alternatively, the heater supply power is limited to a predetermined maximum for restricting excessive temperature rise.

Abstract: In order to activate an exhaust catalyst of an engine as quickly as possible from the engine restart, an exhaust damper for opening and closing an exhaust pipe is disposed downstream of a catalyst. A pneumatic actuator drives to open and close the exhaust damper. A negative pressure is introduced into a pressure chamber of the pneumatic actuator to close the exhaust damper after the engine is stopped. The closed exhaust damper keeps the warmth of the catalyst to ensure high exhaust gas purification performed when the engine is restarted. Alternatively, activation of the exhaust catalyst is enhanced by retarding the engine ignition timing and raising the engine idling speed.

Abstract: An exhaust gas detoxifying system includes a catalytic converter in the exhaust system of an engine to detoxify exhaust gas. An air conditioner includes a compressor which is driven by the engine, and it performs air conditioning of the vehicle interior based on a refrigeration cycle. The operation of the air conditioner compressor is restricted depending on the degree of necessity of air conditioning, which is calculated from the difference between a vehicle interior temperature and a target temperature, if the catalytic converter exhaust gas detoxification performance is expected to deteriorate during accelerating or heavy-load operations of the engine.

Abstract: An air-to-fuel ratio control apparatus for an internal combustion engine includes an air-to-fuel ratio sensor of a current limiting type for detecting an air-to-fuel ratio of an air-fuel mixture from a condition of exhaust gas originating from the air-fuel mixture. An air-to-fuel ratio controlling device is operative for performing feedback control in response to an output signal of the air-to-fuel ratio sensor so that the detected air-to-fuel ratio will be substantially equal to a target air-to-fuel ratio. A gain setting device is operative for setting a feedback gain of the air-to-fuel ratio feedback control in response to an atmospheric pressure.

Abstract: The fuel ratio control system controls the supply of fuel to an internal combustion engine to achieve a target air-fuel ratio, based on the output of an air-fuel ratio sensor. The system may determine whether there is an abnormality in the air-fuel ratio sensor based on a comparison between a change of an air-fuel ratio correction coefficient, used to drive the air-fuel ratio to the target value, and a change of the target air-fuel ratio if the target air-fuel ratio has sharply changed.

Abstract: An exhaust pipe of an internal combustion engine is equipped with a three-way catalytic converter. Provided upstream and downstream the converter are an A/F sensor and a downstream O2 sensor, respectively. A CPU executes air-fuel feedback control according to the readings from the A/F sensor. When the period of air-fuel ratio inversion by the downstream O2 sensor has exceeded a predetermined time, the CPU determines that the three-way catalytic converter is activated. At that point, the CPU estimates the quantity of heat required from the start-up of the engine up to catalyst activation. The quantity of heat is obtained by accumulating the intake air quantity from the start of the engine up to catalyst activation (i.e., accumulated intake air quantity). Given the accumulated quantity of heat calculated, the CPU determines accordingly whether the three-way catalytic converter has deteriorated.

Abstract: In a heater control of an oxygen sensor, a heater control circuit is rendered fully conductive at 100% duty initially to supply full power to a heater until the resistance value of the heater reaches a predetermined initial value corresponding to a predetermined temperature. Then, the duty of the heater control circuit is feedback controlled so that the heater temperature becomes a target value until the internal resistance of the oxygen sensor reaches a target temperature, and further, after the internal resistance of the oxygen sensor S reaches the target temperature, the duty of the heater control circuit is feedback controlled so that the element temperature of the sensor becomes a target value.

Abstract: An oxygen concentration detecting apparatus precisely and easily performs diagnosis of a limit current type oxygen sensor. The limit current type oxygen sensor has an oxygen concentration detecting element for outputting limit current proportional to the oxygen concentration and a heater for heating the detecting element. A CPU of a microcomputer controls energization of the heater to activate the oxygen sensor. The CPU calculates element resistance based on the voltage applied to the oxygen sensor and the current detected in the sensor. In a sensor diagnosis routine, the CPU determines whether preconditions for the diagnosis have been met. If all the preconditions have been met, the CPU executes the diagnosis. That is, the CPU determines whether the element resistance is within a predetermined range. If it is below the range, the CPU determines that the sensor has high element temperature abnormality.

Abstract: A self-diagnostic apparatus of an air-fuel ratio control system of an internal combustion engine performs processes of starting the diagnostic process as the fuel-cut is started, reading and storing a sensor output at the start of the fuel-cut and counting an elapsed time after the start of the fuel-cut by actuating a timer, reading a time until when the sensor output rises from the start of the fuel-cut from the count value of the timer, calculating a rate of change of the sensor output and comparing the calculated rate of change with an abnormality determining value. When the rate of change is large, the response characteristic of the sensor is normal. When it is small, the response characteristic of the sensor is abnormal (degraded), so that the abnormality of the sensor is stored in a memory and an alarm lamp is lighted to inform a driver of the abnormality of the sensor.

Abstract: Glass fiber non-woven fabric for base material of a laminate comprising binder binding glass fibers to each other, said binder including a reactant product formed by reacting a solution of tri-functional epoxy resin, bi-functional epoxy resin and tri-ethylene tetramine and having an acetic solution and phenyl amino-silane coupling agent added thereto. The thus obtained glass fiber non-woven fabric is impregnated with an predetermined amount of epoxy resin and dried to produce prepregs, which are superposed one upon another and formed under heat and pressure of 20 kgf/cm.sup.2 to produce the laminate.

Abstract: In an apparatus for detecting a saturation gas amount absorbed by a catalytic converter disposed in an exhaust system of an engine, an air-to-fuel ratio detecting device is disposed in a region of the engine exhaust system downstream of the catalytic converter for monitoring exhaust gas, which has passed through the catalytic converter, to detect an air-to-fuel ratio of an air-fuel mixture causing the exhaust gas. An air-to-fuel ratio changing device serves to change an air-to-fuel ratio of an air-fuel mixture fed to the engine by a correction quantity in a given direction, and serves to maintain changing the air-to-fuel ratio during a correction time.

Abstract: An air-fuel ratio control apparatus for an engine for reliably converging an air-fuel ratio around a stoichiometric air-fuel ratio to prevent harmful exhaust components from being discharged into the air is described. The apparatus includes a CPU which determines an inversion direction of an output of an O.sub.2 sensor on the downstream side of a catalytic converter, corrects a target air-fuel ratio .lambda.TG in a step-like fashion in the opposite direction by a skip amount and calculates a fuel injection amount every injection timing on the basis of a difference between the corrected target air-fuel ratio .lambda.TG and an air-fuel ratio .lambda. detected by an O.sub.2 sensor on the upstream side of the exhaust flow. The target air-fuel ratio is reflected immediately in the fuel injection amount at an updating rate of every ilnjection timing, so that the fuel injection amount may be controlled with an excellent responsiveness to turbulence in the air-fuel ratio. Further, upper and lower limit guard values .

Abstract: An air-fuel ratio control system for an internal combustion engine includes a pair of cylinder banks, a pair of exhaust passages connected to the cylinder banks, respectively, a common exhaust pipe where the exhaust passages join each other at their downstream ends, a pair of catalytic converters provided in the exhaust passages, respectively, a pair of main air-fuel ratio sensors provided in the exhaust passages upstream of the catalytic converters, respectively, a pair of auxiliary air-fuel ratio sensors provided in the exhaust passages downstream of the catalytic converters, respectively, and a catalytic converter provided in the common exhaust pipe. The system derives an air-fuel ratio feedback control correction value for each of the cylinder banks based on outputs of the auxiliary air-fuel ratio sensors.

Abstract: To inhibit an air pulsating sound resulting from the opening and closing of the air control valve in a cold engine and to improve controllability of ISC functions in an assist air supply apparatus. When an engine is cold based on a cooling water temperature sensor, opening control is performed so as to control the amount of supplied assist air by controlling the opening degree of an air control valve. When the engine is warming-up, injection synchronization control is performed, in which opening and closing of the air control valve are controlled in synchronization with fuel injection from the fuel injection valves. Therefore, it is possible to suppress air pulsating noise resulting from the opening and closing the air control valve when the engine is warming up and to improve controllability of ISC functions in an assist air supply apparatus.

Abstract: In an air-fuel ratio control system for an internal combustion engine, a target air-fuel ratio is set on a side opposite to a direction of deviation of a monitored upstream side air-fuel ratio in such a manner as to counterbalance or offset the deviation of the upstream side air-fuel ratio. The deviation of the upstream side air-fuel ratio may be derived in the form of an mount of a particular component adsorbed in a catalytic converter. A learned value may be used to correct the monitored upstream side air-fuel ratio. Further, a monitored downstream side air-fuel ratio may be used to monitor the setting of the target air-fuel ratio.