Patent ID: 7930932

Claim:
A NOx sensor abnormality detection device of a NOx sensor that is provided downstream of a NOx purification device provided in an exhaust passage of an internal combustion engine and that has a NOx sensing section for sensing a NOx concentration in exhaust gas and an O2 sensing section for sensing an O2 concentration in the exhaust gas, the NOx sensor abnormality detection device comprising: an atmosphere determination means for determining whether a gas atmosphere in the exhaust passage is equivalent to an atmospheric air; a sensed inclination calculation means for calculating a sensed inclination of an output of the NOx sensing section based on a zero point of the NOx concentration sensed with the NOx sensing section when the atmosphere determination means determines that the gas atmosphere in the exhaust passage is equivalent to the atmospheric air and the NOx concentration sensed with the NOx sensing section in a steady operation state of the internal combustion engine; an O2 sensing section determination means for determining whether the O2 sensing section is normal; an estimated NOx concentration calculation means for calculating an estimate of the NOx concentration based on the O2 concentration sensed with the O2 sensing section when the NOx sensing section senses the NOx concentration in the steady operation state for the calculation of the sensed inclination in the case where the O2 sensing section determination means determines that the O2 sensing section is normal; an estimated inclination calculation means for calculating an estimated inclination of the output of the NOx sensing section in the case where the NOx sensing section is normal based on the estimate of the NOx concentration; and an abnormality determination means for determining an abnormality in the NOx sensor based on the sensed inclination and the estimated inclination.