EXHAUST GAS CLEANER FOR ENGINE AND EXHAUST GAS CLEANING METHOD

摘要

[PROBLEMS] A vehicle-mounted SCR device in which the concentration of a reducing agent, a reducing agent contained in its precursor, or a precursor is detected accurately. [MEANS FOR SOLVING PROBLEMS] When the concentration is detected, it is judged whether urine water stored in a storage tank is in stationary state or not, and the concentration is detected only when it is in stationary state. Preferably, the judgment whether urine water is in stationary state or not is made by judging that a vehicle stops (S207) and the time TIM after the stoppage has reached a specified rest time TIM1 (S211). The deceleration DCL of the vehicle before the stoppage is detected and the rest time TIM1 is altered depending on the deceleration DCL (S206).