| 摘要 |
Provided is an SCR system that can rapidly cancel engine start prohibition after filling a urea aqueous solution as well as preventing improper indication of deficiency of the urea aqueous solution by variation in a solution level in a urea aqueous solution tank and unwanted engine start prohibition. The SCR system includes a urea aqueous solution tank 105 configured to retain a urea aqueous solution to be injected into an exhaust pipe 102 of an engine E, a level sensor 120 configured to detect a solution level height in the urea aqueous solution tank 105, a lowpass filter 1 having a signal response characteristic in which a time constant is small when an engine rpm is low and the time constant is larger when the engine rpm is high, with respect to an output signal of the level sensor 120, a remaining amount indicator 2 configured to indicate a remaining amount of the urea aqueous solution based on an output signal of the level sensor 120 processed by the lowpass filter 1, and a start prohibiting unit 3 in deficiency of the urea aqueous solution configured to prohibit the engine from being started when the remaining amount of the urea aqueous solution is less than a lowerlimit value. |
