Abstract: A gas sensor apparatus 3 in an air-fuel ratio detection system 1 includes a gas sensor element 4 which outputs a detection signal corresponding to air-fuel ratio, and a gas sensor control circuit 2 which includes a detection section 20 for outputting a first output signal VIP1, a second output signal VIP2, and a third output signal VIP3 in accordance with the detection signal. This detection section 20 outputs the first output signal VIP1 which changes in accordance with the air-fuel ratio at least within a wide first air-fuel ratio zone, the second output signal VIP2 which changes in accordance with the air-fuel ratio within a narrow zone in the vicinity of the stoichiometric ratio, and the third output signal VIP3 which changes in accordance with the air-fuel ratio within a narrow zone in the lean region.

Abstract: A gas sensor diagnostic method includes the steps of counting the reversal number of times that a target air-fuel ratio for an air-fuel mixture to be supplied to an internal combustion engine reverses from a rich side to a lean side or from the lean side to the rich side through a specific air-fuel ratio defined as a boundary of the rich and lean sides; obtaining a detection signal of gas sensor at constant time intervals during a diagnosis period between a timing when the count for the reversal number is started and a timing when the reversal number reaches a predetermined number; calculating a first moderated signal by applying a first moderation calculation to the detection signal, and a second moderated signal by applying a second moderation calculation to the detection signal; calculating a deviation between the first and second moderated signals; and determining whether the gas sensor is in the abnormal state on the basis of the deviation obtained during the diagnosis period.

Abstract: An oxygen concentration detection system including an oxygen sensor which outputs a plurality of types of measurement signals and anomaly detection means and modification means. The anomaly detection means detects a sensor anomaly by determining whether the respective levels of the plurality of types of measurement signals fall within predetermined ranges. When a sensor anomaly is not detected, the modification means outputs the plurality of types of measurement signals as is. When a sensor anomaly is detected, the modification means outputs at least one of the plurality of types of measurement signals at a level outside the corresponding range within which the level of the measurement signal varies in a normal state.

Abstract: A gas sensor diagnostic method (or apparatus) is arranged to periodically obtain sensor output values of a gas sensor such as an oxygen sensor for an internal combustion engine, and to determine local extreme values from the sensor output values obtained during a period of interruption of fuel supply to the engine. Moreover, the local extreme values are compared with a first predetermined threshold level. When the number of the local extreme values reaches a predetermined first number, a diagnosis is performed to determine whether the gas sensor is in an improper condition or not, in accordance with results of the comparison of the local extreme values with the first threshold level.

Abstract: A gas sensor diagnostic method includes the steps of counting the reversal number of times that a target air-fuel ratio for an air-fuel mixture to be supplied to an internal combustion engine reverses from a rich side to a lean side or from the lean side to the rich side through a specific air-fuel ratio defined as a boundary of the rich and lean sides; obtaining a detection signal of a gas sensor at constant time intervals during a diagnosis period between a timing when the count for the reversal number is started and a timing when the reversal number reaches a predetermined number; calculating a moderated signal by applying a moderation calculation using a predetermined moderation coefficient to the obtained detection signal; calculating a deviation between the obtained detection signal and the calculated moderated signal; and determining whether the gas sensor is in an abnormal state or not on the basis of the deviation.

Abstract: A gas sensor diagnostic method includes: a fuel supply detecting step of detecting an interruption of a fuel supply to the internal combustion engine, and a restart of the fuel supply after the interruption of the fuel supply; a response time period accumulating step of determining a response time period by accumulating a first time period that the sensor output value reaches from a first threshold value to a second threshold value after the detection of the interruption of the fuel supply, and a second time period that the sensor output value reaches from a third threshold value to a fourth threshold value after the detection of the restart of the fuel supply after the interruption of the fuel supply; and an abnormal state diagnosing section of determining an abnormal state of the gas sensor when the response time period is greater than a predetermined time period.

Abstract: A control device for a gas sensor is configured to: receive a mode command to specify one of a plurality of sensor energization modes including at least a gas concentration detection mode, a protection mode and a pre-energization mode; switch a sensor element of the gas sensor into the one of the plurality of sensor energization modes according to the mode command; judge satisfaction of a certain condition where the mode command is to specify the gas concentration detection mode and the sensor element is in any of the plurality of sensor energization modes other than the pre-energization mode at the time of receipt of the mode command; and prohibit the sensor element from switching over to the gas concentration detection mode when the certain condition is satisfied.

Abstract: To provide a malfunction diagnosing method and apparatus capable of reliably determining a malfunction even where the malfunction occurs in a common wire connecting a gas sensor and a control circuit for driving it. In a gas concentration measurement unit 1 having a sensor control circuit 50 which is connected to a sensor element 10 including an oxygen pump cell 14 and an oxygen concentration detection cell 24 and controls and drives this sensor element 10, a variation state of a terminal voltage at one connecting point (specifically, a Vs+ terminal) other than connecting points between electrodes facing a measurement chamber of each cell 14 and 24 and a common wire 24 is detected by a malfunction detection circuit 53 and an arithmetic processor 54. Based on this variation state of the terminal voltage, diagnosis of malfunction in the common wire 42 is executed. When the common wire 42 is broken, the terminal voltage at the Vs+ terminal varies with oscillations.

Abstract: An interface device for a gas sensor includes a detection resistor having first and second ends to generate voltages by a current output of the gas sensor, a differential amplifier having first and second input terminals to receive the voltages of the first and second resistor ends and an output terminal to output a voltage according to a difference between the voltages of the first and second resistor ends, a first switching element to transmit the voltage of the first resistor end to the first input terminal of the differential amplifier in a transmission state and interrupt transmission of the voltage of the first resistor end to the first input terminal of the differential amplifier in an interruption state and a second switching element turned on to establish continuity between the first and second input terminals of the differential amplifier when the first switching element is in the interruption state.

Abstract: An abnormality diagnosis method for a gas concentration measuring device, includes electrically shutting off measurement means from an oxygen concentration detecting cell and an oxygen pump cell of a gas sensor when a voltage at one of electrical connection points through which the measurement means is electrically connected to the oxygen concentration detecting cell and the oxygen pump cell becomes equal to a predetermined abnormal voltage value, and thereafter, electrically connecting the measurement means to the oxygen concentration detecting cell and the oxygen pump cell of the gas sensor to perform an abnormality diagnosis of the gas sensor. An abnormality diagnosis apparatus for a gas concentration measuring device is also provided.

Abstract: A gas detection apparatus including a gas sensor element and a gas-sensor control circuit. The gas sensor element includes at least one sensor cell including a solid electrolyte member and a pair of electrodes, and external connection terminals electrically connected to the electrodes. The gas-sensor control circuit includes control terminals electrically connected to respective external connection terminals of the gas sensor element, an inspection current supply circuit for supplying an inspection current to an inspected terminal, which is a control terminal to be inspected for presence or absence of a short circuit to a predetermined potential, an inspection potential measurement circuit for measuring the potential of the inspected terminal, and an uninspected terminal impedance increasing circuit for increasing the impedance of the gas-sensor control circuit as viewed from an uninspected terminal, which is a control terminal other than the inspected terminal.

Abstract: In an activation state of a sensor device, when voltage on the connection points between the sensor device and the sensor control circuit becomes a preset abnormal value, electric cut off is made between the sensor control circuit and the connection point. Then, the delivery of power to the heater is ceased to lower the temperature of the cells to a below of an activation temperature, thereby increasing the internal resistance of the cell. Thereafter, the sensor control circuit supplies to the sensor device a current in a degree not to damage the sensor device, to detect voltages on the connection points at that time. By comparing between the voltages on the respective connection points detected, a content and location of abnormality occurred is identified for the sensor device.

Abstract: An abnormality diagnosis method for a gas concentration measuring device, includes electrically shutting off measurement means from an oxygen concentration detecting cell and an oxygen pump cell of a gas sensor when a voltage at one of electrical connection points through which the measurement means is electrically connected to the oxygen concentration detecting cell and the oxygen pump cell becomes equal to a predetermined abnormal voltage value, and thereafter, electrically connecting the measurement means to the oxygen concentration detecting cell and the oxygen pump cell of the gas sensor to perform an abnormality diagnosis of the gas sensor. An abnormality diagnosis apparatus for a gas concentration measuring device is also provided.

Abstract: A gas detecting system comprises: a sensor element including: an oxygen pump cell comprising a first oxygen ion conducting solid electrolyte layer between a first pair of electrodes; an oxygen concentration measuring cell comprising a second oxygen ion conducting solid electrolyte layer between a second pair of electrodes; and a measurement chamber between the oxygen pump cell and the oxygen concentration measurement cell; a plurality of lead wires connected with the first and second pairs of electrodes; and a control unit electrically connected with the electrodes through the lead wires, wherein the lead wires includes a common lead wire connected with electrodes confronting the measurement chamber of the first and second pairs of electrodes, and wherein the common lead wire has a portion to contact in an electrically insulated state with at least one of the lead wires other than the common lead wire.

Abstract: Apparatus for measuring NOx concentration comprises a NOx sensor element having an oxygen partial-pressure detection cell 3 which detects oxygen concentration of an analyte gas in first measurement chamber 5, first oxygen pump cell 1 across which a current corresponding to oxygen concentration of analyte gas (“a first oxygen pump current”) flows by pumping oxygen from inside to outside of first measurement chamber 1, second measurement chamber 6 into which gas is introduced from first measurement chamber 5 via second diffusion resistance 8, and second oxygen pump cell 2 across which a current corresponding to NOx concentration (“a second oxygen pump current”) flows by transferring oxygen dissociated by decomposition of nitrogen oxide in second measurement chamber 6; and first diagnostic means 30a for diagnosing the apparatus as normally functioning if the second oxygen pump current Ip2 or a predetermined voltage Vp2 applied to second oxygen pump cell 2 is within a predetermined range,

Abstract: An oxygen concentration detection system including an oxygen sensor which outputs a plurality of types of measurement signals and anomaly detection means and modification means. The anomaly detection means detects a sensor anomaly by determining whether the respective levels of the plurality of types of measurement signals fall within predetermined ranges. When a sensor anomaly is not detected, the modification means outputs the plurality of types of measurement signals as is. When a sensor anomaly is detected, the modification means outputs at least one of the plurality of types of measurement signals at a level outside the corresponding range within which the level of the measurement signal varies in a normal state.