Gas sensor

A gas sensor comprising:

• a sensor element including
• an element body which includes an oxygen-ion-conductive solid electrolyte layer, and is internally provided with a measurement-object gas flow portion that introduces a measurement-object gas and flows the measurement-object gas,
• a measurement pump cell having an outer measurement electrode provided outside the element body to be in contact with the measurement-object gas, and an inner measurement electrode disposed in a measurement chamber of the measurement-object gas flow portion, the measurement pump cell being configured to pump out oxygen from a surroundings of the inner measurement electrode to a surroundings of the outer measurement electrode,
• a reference electrode disposed inside the element body to come into contact with a reference gas which serves as a reference for detection of a specific gas concentration in the measurement-object gas,
• a measurement voltage detection sensor cell that detects a measurement voltage between the reference electrode and the inner measurement electrode,
• a main pump cell that adjusts an oxygen concentration in a first internal cavity provided on an upstream side of the measurement chamber of the measurement-object gas flow portion,
• an auxiliary pump cell that has an inner auxiliary pump electrode disposed in a second internal cavity, and adjusts an oxygen concentration in the second internal cavity, the second internal cavity being provided on a downstream side of the first internal cavity and on an upstream side of the measurement chamber of the measurement-object gas flow portion,
• an auxiliary pump voltage detection sensor cell that detects an auxiliary pump voltage between the reference electrode and the inner auxiliary pump electrode, and
• a heater that heats the element body;
• a heater controller that executes a heater control process of energizing the heater to cause the heater to generate heat;
• a pump cell controller that executes a normal time control process after the heater control process is started, the normal time control process including a main pump control process of controlling the main pump cell, an auxiliary pump control process of controlling the auxiliary pump cell so that the auxiliary pump voltage reaches a target value, and a normal time measurement pump control process of pumping out oxygen in the measurement chamber by controlling the measurement pump cell so that the measurement voltage reaches a normal time target value;
• and
• a specific gas concentration detection section that detects a specific gas concentration in the measurement-object gas based on a measurement pump current which flows through the measurement pump cell by the normal time measurement pump control process,
• wherein in an early stage of the normal time control process, the pump cell controller executes a correction process of correcting the target value of the auxiliary pump voltage to a value higher than a target value in a period after the early stage, and
• wherein the pump cell controller corrects the target value of the auxiliary pump voltage in the correction process based on a correction pattern which is defined in advance so that a correction amount tends to decrease as time passes.