A gas sensor includes: a sensor element including a bottomed tubular solid electrolyte, a detection electrode, and a reference electrode; and a heater for heating the solid electrolyte. The reference electrode includes an inner detection section on an entire periphery in a circumferential direction at an endmost position on a tip side on the reference electrode, an inner connecting section on an entire periphery in the circumferential direction at an endmost position on a base end side on the reference electrode, and an inner lead section on a part in the circumferential direction at a position where the inner detection section is connected to the inner connecting section. A formation region in the circumferential direction of the inner lead section is reduced stepwise from the inner detection section toward the inner connecting section.

Provided are a novel exhaust pipe temperature estimation device and a sensor heater control apparatus for an exhaust gas sensor using the same that accurately estimates an estimation exhaust pipe temperature when an internal combustion engine is stopped and restarted in response to a change of an environmental condition of the internal combustion engine and controls an operation of a sensor heater based on the estimated estimation exhaust pipe temperature. Thus, at least first correction information Tz based on a change of an exhaust pipe temperature and an elapsed time at stop, second correction information Ty based on a change of an internal combustion engine temperature at the stop of the internal combustion engine, and third correction information Tz based on a change of a cooling degree due to outdoor air during stop from the stop to restart are obtained, an estimation exhaust pipe temperature at the stop is corrected using at least one or more pieces of the correction information at restart of the internal combustion engine to estimate an estimation exhaust pipe temperature at the restart, and an estimation exhaust pipe temperature during an operation of the internal combustion engine thereafter is obtained using the estimation exhaust pipe temperature as an initial value, and further, a heating operation of a sensor heater is started when the estimation exhaust pipe temperature becomes equal to or higher than a predetermined value.

Vehicle oxygen sensor heater diagnostic techniques comprise, upon detection of a set of cold start conditions of the vehicle, measuring an initial resistance of each of a set of two or more oxygen sensor heaters and determining whether any of the measured initial resistances is outside of a nominal resistance range. In response to an outlier oxygen sensor heater being outside of the nominal resistance range, each of the set oxygen sensor heaters is provided with an equal voltage for a period, the resistance of each of the set of oxygen sensor heaters is monitored during the period, and a malfunction of the outlier oxygen sensor heater is detected or matured when a difference between its resistance and the resistances of the other oxygen sensor heaters after the period is greater than a calibrated threshold.

An air-fuel ratio control system (1) including an air-fuel ratio control section (3) for controlling the air-fuel ratio λ of an air-fuel mixture, an exhaust gas purifier (4); an air-fuel ratio sensor (5) whose output changes sharply when λ in the exhaust gas changes between rich and lean sides about a stoichiometric air-fuel ratio; a heater (6); and a temperature control section (7). The air-fuel ratio control section (3) controls λ based on the output of the air-fuel ratio sensor (5) using, as a target air-fuel ratio, a predetermined air-fuel ratio such that 0.980≤λ<1.000 is satisfied, and when a change amount Δλ λ is 0.008, an output difference ΔV is 150 mV or smaller. The temperature control section (7) controls the temperature of the air-fuel ratio sensor (5) to a predetermined target temperature of 650° C. or higher.

Systems and methods for operating an internal combustion engine that includes an oxygen sensor are described. In one example, a voltage that is applied to a heating element of an oxygen sensor is integrated to determine a resistance of the heating element. The resistance of the heating element is the basis for adjusting voltage applied to the heating element during subsequent engine starts.

A driver circuit drives a heater associated with a sensor in an exhaust system of a vehicle at a duty cycle. A feedback circuit generates a feedback signal indicating a temperature of the sensor. A ramp circuit outputs a first ramping set point indicating a first rate at which the temperature of the sensor is to be changed over a first time period after an engine of the vehicle is turned on, and a second ramping set point indicating a second rate at which the temperature of the sensor is to be changed after the first time period until the temperature of the sensor reaches a predetermined temperature. An error circuit generates first and second error signals based on the feedback signal and the first and second ramping set points. A controller controls the duty cycle of the driver circuit to drive the heater based on one or more gains.

The purpose of the present invention is to reduce a load of preventing dew condensation, and to provide a highly reliable humidity detection device. In order to achieve the purpose, this humidity detection device is provided with: a humidity sensor having a humidity detection unit and a temperature detection unit; a heating resistor that heats the humidity sensor; and a heating control unit that controls a heating temperature of the heating resistor. The humidity detection device is characterized in having a target temperature storage unit that stores target temperatures of the heating resistor, said target temperatures having been determined corresponding to temperatures and humidities.

The invention relates to a method for starting an internal combustion engine, the exhaust gas system of which is equipped with an electrically heatable lambda sensor and a catalytic converter with an oxygen reservoir. The combination of method steps according to the invention allows the internal combustion engine to be started with an optimal raw emission reduction directly after a cold start and an optimal pollutant conversion in the warm-up phase. The invention likewise relates to a motor vehicle with an internal combustion engine comprising an exhaust gas system having an electrically heatable lambda sensor and a catalytic converter with an oxygen reservoir, and comprising a controller, wherein the controller is designed to carry out the method according to the invention.

An air-fuel ratio detection device 1, 1 comprises: a sensor element 2, 2 including a sensor cell 10; a voltage application circuit 40, 40 applying voltage to the sensor cell; a current detector 42, 42 detecting an output current of the sensor cell; an air-fuel ratio calculating part 61 configured to calculate an air-fuel ratio of an exhaust gas; and a parameter detecting part 62 configured to detect or calculate a temperature correlation parameter correlated with a temperature of the sensor element. The air-fuel ratio calculating part is configured to calculate the air-fuel ratio of the exhaust gas based on the temperature correlation parameter and the output current detected when a predetermined voltage is applied to the sensor cell.

The invention relates to a method for starting an internal combustion engine, the exhaust gas system of which is equipped with an electrically heatable lambda sensor and a catalytic converter with an oxygen reservoir. The combination of method steps according to the invention allows the internal combustion engine to be started with an optimal raw emission reduction directly after a cold start and an optimal pollutant conversion in the warm-up phase. The invention likewise relates to a motor vehicle with an internal combustion engine comprising an exhaust gas system having an electrically heatable lambda sensor and a catalytic converter with an oxygen reservoir, and comprising a controller, wherein the controller is designed to carry out the method according to the invention.