Patent ID: 8959891
Filing Date: 2015-02-24
Classification: F01N,G01F,Y02T

Abstract:
1. An SCR system including: a selective catalytic reduction device provided in an exhaust pipe for an engine; a urea tank that stores urea; a float-type urea level sensor provided in the urea tank, the float-type urea level sensor including a float following a liquid surface of the urea in the urea tank, and detection means for detecting a position of the float to detect a liquid level of the urea stored in the urea tank; and a urea injection control unit that controls an injected quantity of urea according to a quantity of NO wherein the SCR system comprises: a urea injection quantity integrating unit that integrates the injected quantity of urea to calculate a urea injection quantity integrated value; an integrated value resetting unit that if a detected value from the detection means changes, resets the urea injection quantity integrated value; and an abnormality determination unit that if the urea injection quantity integrated value exceeds a predetermined threshold value for determination, determines the urea level sensor as having an abnormality.