| 摘要 |
<P>PROBLEM TO BE SOLVED: To determine that an aqueous solution such as a reducing agent is frozen including the discrimination of a phase state in which the freezing point is in a temperature zone in a vicinity of the melting point. <P>SOLUTION: An exhaust emission controller of an engine has a storage tank for storing a reducing agent of NOx or its precursor in a state of an aqueous solution. The temperature T of the aqueous solution such as the reducing agent stored in the storage tank and the concentration D of the reducing agent or the like contained in the aqueous solution are detected, and whether or not the stored aqueous solution is frozen is determined based on the detected temperature T and concentration D. The concentration is detected by the concentration sensor. The concentration sensor comprises a temperature-sensing body having the electric characteristic value being changed according to the temperature, and a heater which is thermally connected to the heat-sensing body. The heat-sensing body is provided in a direct or indirect contact state with the stored aqueous solution. The concentration sensor drives the heater, and outputs the electric characteristic value R of the heat-sensing body heated by the heater as the concentration D of the reducing agent or the like. <P>COPYRIGHT: (C)2009,JPO&INPIT |
