Control apparatus

1. A control apparatus for an exhaust gas sensor, comprising:

a temperature rise determination unit configured to:

acquire at least one of:

a first parameter indicating a temperature of a first cell for removing oxygen from an exhaust gas discharged from an internal combustion engine; and

a second parameter indicating a temperature of a second cell for detecting a measurement target component contained in a measurement target gas generated by removing the oxygen from the exhaust gas by an operation of the first cell; and

determine whether a temperature rise condition of at least one of the first cell and the second cell is satisfied in accordance with whether the at least one of the first parameter and the second parameter has exceeded a corresponding at least one temperature threshold; and

an activation determination unit configured to:

determine, based on whether a time condition corresponding to the temperature threshold is satisfied, whether the exhaust gas sensor is in an active state in which the exhaust gas sensor is capable of performing a measurement operation with at least a predetermined accuracy; and

determine that the exhaust gas sensor is in the active state upon, after the temperature rise condition is determined to be satisfied, the time condition corresponding to the temperature threshold being satisfied.

2. The control device according to claim 1 , wherein

the at least one temperature threshold comprises a first temperature threshold for the first parameter, and a second temperature threshold for the second parameter; and

the temperature rise determination unit is configured to:

acquire the first parameter and the second parameter;

determine whether the temperature rise condition of the first cell is satisfied in accordance with whether the first parameter has exceeded the first temperature threshold; and

determine whether the temperature rise condition of the second cell is satisfied in accordance with whether the second parameter has exceeded the second temperature threshold.

3. The control device according to claim 1 , wherein:

at least one of the first parameter and the second parameter is an admittance or an impedance of the corresponding at least one of the first cell and the second cell during an application of an alternating voltage to the corresponding at least one of the first cell and the second cell.

4. The control device according to claim 1 , further comprising:

a period setting unit configured to set a predetermined period for determining whether the time condition is satisfied, in accordance with a time interval from a start of energization of the first and second cells to a time at which the temperature rise condition is satisfied.

5. The control device according to claim 1 , further comprising:

a period setting unit configured to set a predetermined period for determining whether the time condition is satisfied, in accordance with at least one of:

an environment condition in which the exhaust gas sensor is provided; and

an operating condition of the internal combustion engine.

6. The control device according to claim 1 , further comprising:

an early activation unit configured to:

execute early activation control to temporarily increase a voltage to be applied to the first cell at start-up of the internal combustion engine;

determine an early-activation completion condition on which the early activation control is completed; and

determine that the exhaust gas sensor is in the active state upon determining that:

all the temperature rise condition, the time condition, and the early-activation completion condition are satisfied; and

an activation-control time condition for eliminating influence of hydrogen resulting from the early activation control is satisfied.

7. The control device according to claim 6 , wherein:

the exhaust gas sensor has, as the second cell, a monitor cell for detecting concentration of oxygen contained in the measurement target gas generated by removing the oxygen from the exhaust gas by the operation of the first cell; and

the activation determination unit is configured to determine that the exhaust gas sensor is in the active state upon determining that, after the temperature rise condition is satisfied, an output of the monitor cell indicates that the influence of hydrogen is eliminated, instead of satisfaction of the activity control time condition.

8. The control device according to claim 1 , wherein:

the time condition is preset to ensure a time for eliminating the influence of water vapor and/or rich gas on the second cell after satisfaction of the temperature rise condition.

9. The control device according to claim 1 , wherein:

the activation determination unit is configured to determine that an abnormality has occurred in the exhaust gas sensor upon determining that the temperature rise condition is not satisfied even after a lapse of a predetermined period.