Controller of reducing agent supply unit and method of controlling the same

Abstract

A reducing agent supply unit that prevents any heat damaging of reducing agent injection valve and also prevents any crystallization of urea solution by excessive cooling of liquid reducing agent; and a method of controlling the same. There is disclosed a reducing agent supply unit for use in an exhaust purification apparatus capable of feeding by injection a urea solution as a reducing agent on the along-exhaust upstream side of a reduction catalyst disposed along an exhaust path of internal combustion engine so as to attain reduction purification of any nitrogen oxides contained in exhaust gas by the reduction catalyst, which reducing agent supply unit has a reducing agent injection valve fixed to an exhaust pipe on the along-exhaust upstream side of the reduction catalyst. The reducing agent supply unit comprises a cooling water circulation path for circulating at least a portion of the cooling water of the internal combustion engine in order to cool the reducing agent injection valve; flow rate control means for regulating the flow rate of cooling water through the cooling water circulation path; temperature detection means for detecting the temperature of the reducing agent injection valve; and control means for controlling the flow rate control means on the basis of the temperature of the reducing agent injection valve.

Description

technical field [0001] The present invention relates to a reducing agent supply device and a control method used in an exhaust gas purification device. In particular, it relates to a reducing agent supply device and a control method of the reducing agent supply device configured to cool a reducing agent injection valve by using a urea solution as a reducing agent and circulating cooling water for cooling an internal combustion engine. Background technique [0002] Conventionally, in the exhaust gas discharged from internal combustion engines such as diesel engines, nitrogen oxides (hereinafter referred to as NO X ). as in order to put the NO X The exhaust purification device used for purification is known to spray and supply a liquid reducing agent such as urea solution into the exhaust gas on the upstream side of the reduction catalyst arranged in the exhaust passage, and to inject NO into the reduction catalyst. X Selective reduction purification exhaust gas purificatio...

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Problems solved by technology

[0004] In addition, the electromagnetically controlled valve used as the reducing agent injection valve is directly mounted on the exhaust pipe although its control part and resin part have poor heat resistance, so it is easy to be thermally damaged by the heat transferred from the exhaust pipe.

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