Patent ID: 9551261
Date: 2017-01-24
CPC Classifications: F01N,Y02T

Claim:
1. In an exhaust emission control device that is provided in an exhaust passage of an internal combustion engine and has a first NOx catalyst and a second NOx catalyst configured to reduce NOx by using ammonia as a reducing agent, a urea water supply system that supplies urea water to the exhaust passage, the urea water supply system comprising: a first supply valve that is located upstream of the first NOx catalyst and is configured to supply urea water to an exhaust emission flowing into the first NOx catalyst; a second supply valve that is located upstream of the second NOx catalyst and is configured to supply the urea water to the exhaust emission flowing into the second NOx catalyst; a urea water tank that is configured to store the urea water; a urea water supply path that is arranged to connect the urea water tank with each of the first supply valve and the second supply valve and includes a first supply path which only the urea water to be supplied to the first supply valve flows through and a second supply path which only the urea water to be supplied to the second supply valve flows through, wherein the second supply path has a larger capacity than capacity of the first supply path by a predetermined volume; a pump that is configured to pressure-feed the urea water in the urea water supply path; an acquirer that is configured to obtain a pressure value or variation per unit time in the urea water supply path or in the pump; and a controller that is configured to perform filling control of the urea water into the first and second supply valves and into the urea water supply path by operating the pump in a specified operating state and performing open-close control of the first supply valve and the second supply valve, wherein in the filling control, the controller pressure-feeds the urea water to the first supply valve and the first supply path by the pump operated in the specified operating state in a state that at least the first supply valve out of the first and second supply valves is opened, and closes the first supply valve based on the obtained pressure value or variation per unit time.