Abstract: An A/F signal proportional to an oxygen concentration in the exhaust gas from an internal combustion engine is output upon application of a voltage based on an instruction from a microcomputer. At the time an element resistance is detected, a bias instruction signal Vr from the microcomputer is converted by a D/A converter 21 to an analog signal Vb. An output voltage Vc obtained by removing high frequency components from the analog signal Vb through an LPF 22 is input to a bias control circuit 40. During this time period in which the element resistance is detected, an accurate A/F signal is not output. Therefore, the A/F signal that has theretofore prevailed is held by a Sample/Hold circuit 70 to thereby prevent the use of an erroneous A/F signal. Namely, at the time of detecting the element resistance, the detected value of the oxygen concentration is prevented from becoming abnormal. As a result, an accurate A/F control can be executed using the detected element resistance.

Abstract: A gas concentration measuring apparatus which has a gas sensor designed to measure, for example, the concentrations of O2 and HOx contained in exhaust emissions of an automotive engine is provided. The apparatus includes a signal processing circuit which converts a current signal outputted from the gas sensor as a function of the concentration of either of O2 and NOx into a voltage signal. The gas sensor and the signal processing circuit are connected electrically through a conductor. The conductor has a length which is determined as a function of a level of the current signal outputted from the gas sensor. The weaker the level of the current signal is, the shorter the length of the conductor. This minimizes addition of electrical noises to the current signal outputted from the gas sensor.

Abstract: A gas concentration measuring apparatus which has a gas sensor designed to measure, for example, the concentrations of O2 and HOx contained in exhaust emissions of an automotive engine is provided. The apparatus includes a signal processing circuit which converts a current signal outputted from the gas sensor as a function of the concentration of either of O2 and HOx into a voltage signal. The gas sensor and the signal processing circuit are connected electrically through a conductor. The conductor has a length which is determined as a function of a level of the current signal outputted from the gas sensor. The weaker the level of the current signal is, the shorter the length of the conductor. This minimizes addition of electrical noises to the current signal outputted from the gas sensor.

Abstract: A gas concentration measuring apparatus which has a gas sensor designed to measure, for example, the concentrations of O2 and HOx contained in exhaust emissions of an automotive engine is provided. The apparatus includes a signal processing circuit which converts a current signal outputted from the gas sensor as a function of the concentration of either of O2 and HOx into a voltage signal. The gas sensor and the signal processing circuit are connected electrically through a conductor. The conductor has a length which is determined as a function of a level of the current signal outputted from the gas sensor. The weaker the level of the current signal is, the shorter the length of the conductor. This minimizes addition of electrical noises to the current signal outputted from the gas sensor.

Abstract: An A/F signal proportional to an oxygen concentration in the exhaust gas from an internal combustion engine is output upon application of a voltage based on an instruction from a microcomputer. At the time an element resistance is detected, a bias instruction signal Vr from the microcomputer is converted by a D/A converter 21 to an analog signal Vb. An output voltage Vc obtained by removing high frequency components from the analog signal Vb through an LPF 22 is input to a bias control circuit 40. During this time period in which the element resistance is detected, an accurate A/F signal is not output. Therefore, the A/F signal that has theretofore prevailed is held by a Sample/Hold circuit 70 to thereby prevent the use of an erroneous A/F signal. Namely, at the time of detecting the element resistance, the detected value of the oxygen concentration is prevented from becoming abnormal. As a result, an accurate A/F control can be executed using the detected element resistance.

Abstract: An A/F signal proportional to an oxygen concentration in the exhaust gas from an internal combustion engine is output upon application of a voltage based on an instruction from a microcomputer. At the time an element resistance is detected, a bias instruction signal Vr from the microcomputer is converted by a D/A converter 21 to an analog signal Vb. An output voltage Vc obtained by removing high frequency components from the analog signal Vb through an LPF 22 is input to a bias control circuit 40. During this time period in which the element resistance is detected, an accurate A/F signal is not output. Therefore, the A/F signal that has theretofore prevailed is held by a Sample/Hold circuit 70 to thereby prevent the use of an erroneous A/F signal. Namely, at the time of detecting the element resistance, the detected value of the oxygen concentration is prevented from becoming abnormal. As a result, an accurate A/F control can be executed using the detected element resistance.

Abstract: A heater control system is provided for controlling the temperature of a heater used to heat a solid electrolyte-made sensing element of a gas concentration sensor up to a given temperature at which the sensing element is activated to provide a desired gas concentration output for controlling a preselected variable used in a given feedback control system. The heater control system controls an electric power supplied to the heater to bring the temperature of the sensing element into agreement with a target temperature value and determines the target temperature value as a function of the preselected variable used in the feedback control system so that only desired quantity of power may be supplied to the heater, thereby minimizing a consumption of the power.

Abstract: An A/F sensor generates a current signal corresponding to an air-fuel ratio in response to a voltage applied by a bias control circuit. After a sensor current is received as a voltage signal via a voltage follower, it is outputted to an A/D converter having a predetermined input voltage range, 0 to 5V. A sensor current detection circuit has a plurality of current detection resistors. In order to variably set the resistance value by the sensor current detection circuit, a switch circuit is switched in accordance with the sensor current depending on whether the A/F value to be detected is in the zone near the stoichiometric ratio or in other air-fuel ratio zones.

Abstract: A gas concentration sensor voltage and current (in both heater on and heater off states) are detected and compared with predetermined thresholds, respectively, by a microcomputer. Based on a combination of the comparison results, the presence or absence of trouble in the system is detected and trouble location in the system is specified. In addition or alternatively, the sensor voltage is compared with thresholds to determine whether it is outside of a normal zone. The voltage may be actually detected or calculated. If the voltage is outside the normal zone, sensor voltage is reduced to zero or restricted to a predetermined limit.

Abstract: An air-fuel ratio sensor generates linear air-fuel ratio detection signals proportional to concentration of oxygen in exhaust gas from an engine in response to a command voltage from a microprocessor. A bias command signal generated by the microprocessor is provided to a D/A converter which converts it to an analog signal. Thereafter, the signal is provided to an LPF for removing the high frequency components of the analog signal. Output voltage of the LPF is provided to a bias control circuit. A single AC signal which has a predetermined frequency and which is provided with a predetermined time constant (about 159 .mu.s) by the LPF is applied to the air-fuel ratio sensor. Element resistance of the air-fuel ratio sensor is detected based on the voltage of the AC signal and the change in the current level of the air-fuel ratio sensor caused by the application of the AC signal.

Abstract: A method that detects an air-fuel ratio in each cylinder of an internal combustion engine by properly setting a cycle of detecting an element resistance of an A/F oxygen concentration sensor. Although an actual A/F signal is at the stoichiometric ratio in each cylinder at exhaust timing cycle in a practical engine rotational speed range, the ratio is largely deviated to the rich side in the #1 cylinder. The first element resistance detection timing cycle coincides with generation timing of the actual A/F signal, so that the A/F signal cannot be detected. When the element resistance detection timing cycle is preset so as to be longer than the exhaust timing cycle, the second actual A/F signal detection timing for the #1 cylinder does not coincide with the element resistance detection timing. Consequently, the actual A/F signal of the #1 cylinder can be detected as an A/F signal by the A/F sensor.

Abstract: An A/F sensor outputs a linear air-fuel ratio detection signal proportional to the oxygen concentration in an exhaust gas from an engine upon application of a voltage. A computer controls the applied-voltage in a stoichiometric control region, a lean burn control region, an atmosphere detection region and a rich control region to have a fixed value such that the change rate of the applied-voltage is reduced to be less than that in other regions. In addition, when changing the voltage applied to the A/F sensor, the computer variably sets the voltage change speed sequentially. Thus, the influence of the capacitive characteristic of the A/F sensor is eliminated.

Abstract: An A/F sensor generates a current signal corresponding to an air-fuel ratio in response to a voltage applied by a bias control circuit. After a sensor current is received as a voltage signal via a voltage follower, it is outputted to an A/D converter having a predetermined input voltage range, 0 to 5V. A sensor current detection circuit has a plurality of current detection resistors. In order to variably set the resistance value by the sensor current detection circuit, a switch circuit is switched in accordance with the sensor current depending on whether the A/F value to be detected is in the zone near the stoichiometric ratio or in other air-fuel ratio zones.

Abstract: An A/F sensor is driven by a voltage applied thereto at a command issued by a microprocessor, outputting an A/F detection signal which is linearly proportional to the concentration of oxygen. The microprocessor controls the voltage applied to the A/F sensor to bring a current flowing through the A/F sensor to a predetermined value in a zone outside a predetermined air-fuel ratio detection zone. In this outside zone, the applied voltage is controlled in accordance with a characteristic different from a positive characteristic in a normal positive characteristic in a voltage-current relation. That is, in a rich zone outside the air-fuel ratio detection zone, the applied voltage is controlled so as to make the applied voltage approach a maximum value of the electromotive force of the A/F sensor. In a lean zone outside the air-fuel ratio detection zone, on the other hand, the applied voltage is controlled so as to make the applied voltage approach a minimum value of the electromotive force of the A/F sensor.

Abstract: To achieve change-over from detection of an internal resistance of an oxygen sensor S to detection of a threshold current effectively in a short time, a positive desired voltage for measuring a threshold current is applied to an oxygen sensor S to detect the threshold current and then a negative voltage for measuring a temperature is applied to the oxygen sensor S for a short time to detect an internal resistance of the oxygen sensor. After that, when the voltage applied to the oxygen sensor S is restored to a positive desired voltage for measuring the threshold current, by applying a voltage higher than this positive desired voltage temporarily to the oxygen sensor S, discharge or recharge of electric charges due to electrostatic capacitance components of the oxygen sensor S is completed quickly to reduce the time required for convergence to the threshold current when the voltage is changed. As a result, it is possible to reduce the time during which the threshold current cannot be detected.

Abstract: A steering angle detecting apparatus for accurately and surely detecting a steering angle of a motor vehicle. The apparatus is equipped with a turning angle detector for detecting a turning angle of a steering wheel of the motor vehicle. In addition, the apparatus estimates a turning angle of the steering wheel on the basis of the difference in speed between left and right wheels of the motor vehicle so as to calculate the difference in phase between the detection turning angle and the estimation turning angle. For detecting the accurate vehicle steering angle, the detection turning angle is corrected on the basis of the calculated phase difference therebetween.

Abstract: A signal processing circuit for removing a noise component from a detection signal of a yaw-rate sensor for detecting a yaw rate generated in a motor vehicle. The processing circuit detects the magnitude of variation of the detection signal of the yaw-rate sensor so as to compare the magnitude of the detection signal with a predetermined reference value. In accordance with the comparison result, the processing circuit outputs a limitation detection signal to limit the variation to below the predetermined reference value. Further, when the magnitude of variation of the detection signal exceeds the predetermined reference value, the processing circuit outputs as the limitation detection signal the yaw rate detection signal immediately before the exceeding, and the predetermined reference value is corrected on the basis of the steering angular velocity of the steering wheel of the motor vehicle. This arrangement allows effectively eliminating a spear-like noise from the detection signal of the yaw-rate sensor.

Abstract: An auxiliary steering control system in connection with an anti-skid control system for use in a motor vehicle with two parts of left and right wheels, the anti-skid control system being adapted to independently control braking pressures for at least one pair of left and right wheels and including a braking actuator for adjusting braking pressures to be applied to the pair of left and right wheels. The braking actuator is controlled so that the braking pressures therefor approach the target braking forces determined on the basis of the rotational speeds of the wheels. The steering control device includes a steering actuator for adjusting steering angles of the pair of left and right wheels in response to steering control signals from a steering angle control unit.

Abstract: A steering apparatus for use in a motor vehicle whereby the actual steering angle of a vehicle wheel is controlled to be equal to a target steering angle. The steering apparatus includes a steering mechanism for regulating a steering angle of the vehicle wheel in accordance with an input signal thereto, a device for determining a target steering angle of the wheel in accordance with the vehicle travelling state, a device for obtaining the difference (X1) between the determined target steering angle and the actual steering angle of the wheel, and a device for calculating a steering angular velocity (X2) on the basis of the actual steering angle. A control device calculates at least two switching functions (L1), (L2) on the basis of the obtained difference (X1) and the calculated steering angular velocity (X2) for obtaining a switching line on the basis of the calculated switching functions (L1), (L2).

Abstract: A fuel injection arrangement for a diesel engine. An overflow passage for high pressure fuel is provided in the engine's fuel injection pump. A solenoid valve is disposed in the overflow passage for controlling the fuel injection amount through its on-off operation. The time when the fuel injection pump starts injecting fuel is detected by an injection start detector. To this injection starting time point is added a target injection period to determine an injection end time. At this injection end time the solenoid valve is opened to discontinue the fuel injection. The target injection period is determined according to operating conditions of the engine. Since this apparatus detects the actual injection start point and controls the injection period on the basis of the result of the detection, the fuel injection amount can be controlled extremely accurately.