Impedance detector for oxygen concentration sensor element

An impedance detector for detecting an impedance of an element of an oxygen concentration sensor, the impedance detector comprising:

• a current application portion applying a first current and a second current, directions of which are opposite to each other, to the element of the oxygen concentration sensor in order;
• a detection portion detecting a difference between a current application prior voltage and a current application subsequent voltage, the current application prior voltage being a voltage between both of ends of the element before being applied with the first current, the current application subsequent voltage being a voltage between both of the ends of the element when being applied with the first current;
• and
• an impedance calculation portion calculating an impedance of the element based on the difference detected by the detection portion and a value of the first current, wherein:
• the current application portion is configured to change a current application time, which is a period of time to apply the first current and the second current, according to a command provided to the current application portion,
• the oxygen concentration sensor is a one cell type air fuel ratio sensor having one cell through which a sensor current according to an air fuel ratio flows in a state of being applied with a voltage,
• the element is the one cell,
• the impedance detector further comprises:
• an air fuel ratio calculation portion calculating an air fuel ratio based on the sensor current;
• a voltage control portion changing the voltage applied to the one cell according to the sensor current;
• and
• a voltage control prohibition portion prohibiting the voltage control portion from changing the voltage applied to the one cell in a period of time from a time the current application portion initiates application of the first current to a time a predetermined prohibition duration time has elapsed after the current application portion ended application of the second current, and
• the voltage control prohibition portion is configured to change the prohibition duration time according to a command provided to the voltage control prohibition portion.

An impedance detector for detecting an impedance of an element of an oxygen concentration sensor, the impedance detector comprising:

• a current application portion applying a first current and a second current, directions of which are opposite to each other, to the element of the oxygen concentration sensor in order;
• a detection portion detecting a difference between a current application prior voltage and a current application subsequent voltage, the current application prior voltage being a voltage between both of ends of the element before being applied with the first current, the current application subsequent voltage being a voltage between both of the ends of the element when being applied with the first current;
• and
• an impedance calculation portion calculating an impedance of the element based on the difference detected by the detection portion and a value of the first current, wherein:
• the current application portion is configured to change a current application time, which is a period of time to apply the first current and the second current, according to a command provided to the current application portion,
• the oxygen concentration sensor is an O2 sensor,
• the element is included in the O2 sensor,
• the impedance detector further comprises:
• a determination portion receiving an output voltage of the O2 sensor and determining whether an air fuel ratio is lean or rich based on the output voltage of the O2 sensor;
• and
• a renewing prohibition portion prohibiting the output voltage received by the determination portion from being renewed in a period of time from a time the current application portion initiates application of the first current to a time a predetermined prohibition duration time has elapsed after the current application portion ended application of the second current, and
• the renewing prohibition portion is configured to change the prohibition duration time according to a command provided to the renewing prohibition portion.