SOx concentration detection device

An SOx concentration detection device comprising:

• an electronic control unit electrically connected, on an input side, to a plurality of engine control sensors and electrically connected, on an output side, to a plurality of actuators, the electronic control unit for executing predetermined programs based on input information from the plurality of engine control sensors;
• and
• a limiting current-type sensor including a solid electrolyte and a pair of electrodes, the solid electrolyte having oxide ion conductivity, and the pair of electrodes being provided on opposite sides of the solid electrolyte,
• the limiting current-type sensor configured to generate a limiting current corresponding to a concentration of a specific component in exhaust gas from an internal combustion engine when a predetermined voltage is applied between the pair of electrodes;
• the electronic control unit programmed to:
• apply a reference voltage and an SOx detecting voltage between the pair of electrode when an exhaust gas air-fuel ratio of the internal combustion engine is on rich side of stoichiometry, the reference voltage being a voltage in a limiting current region that includes the predetermined voltage, and the SOx detecting voltage being a voltage in a voltage region higher than the limiting current region,
• acquire an SOx detecting output that is output from the limiting current-type sensor when the SOx detecting voltage is applied, and acquire a reference output that is output from the limiting current-type sensor when the reference voltage is applied, and
• detect a SOx concentration in the exhaust gas from the internal combustion engine using histories of the SOx detecting output and the reference output that are generated before an output difference between the SOx detecting output and the reference output falls to or below a set value.