Patent ID: 7651262

Claim:
An apparatus for discriminating liquid reducing agent, comprising: a concentration sensor that incorporates therein temperature sensors arranged at two positions close to each other in a storage tank storing a liquid reducing agent and a heater incorporated in one of the temperature sensors; and a control unit incorporating therein a computer, wherein the control unit: operates the heater of the concentration sensor at each predetermined time after a start of an engine operation to thereby indirectly measure a concentration of the liquid reducing agent based on a temperature detected by each of the temperature sensors; processes discrimination in a manner such that the storage tank is filled with a dissimilar aqueous solution that is dissimilar from the liquid reducing agent when the concentration is lower than a lower threshold, that the storage tank is normally filled with the liquid reducing agent when the concentration is equal to or higher than the lower threshold and also equal to or lower than an upper threshold, and that the storage tank is empty when the concentration is higher than the upper threshold; judges, upon discrimination of the storage tank being filled with the dissimilar aqueous solution, whether or not a dissimilar aqueous solution discrimination is adequate, based on the temperature detected by each of the temperature sensors and the concentration measured by the concentration sensor, and counts up, upon being judged that the dissimilar aqueous solution discrimination is adequate, a frequency of the dissimilar aqueous solution discrimination; judges, upon discrimination of the storage tank being empty, whether or not an empty discrimination is adequate, based on the temperature detected by each of the temperature sensors, and counts up, upon being judged that the empty discrimination is adequate, a frequency of the empty discrimination; resets, upon discrimination of the storage tank being normally filled, the frequency of the dissimilar aqueous solution discrimination and the frequency of the empty discrimination; and upholds the dissimilar aqueous solution discrimination and the empty discrimination when the frequency of the dissimilar aqueous solution discrimination and the frequency of the empty discrimination become equal to or larger than a first predetermined frequency.