Control unit and control method for reductant supply device

Abstract

A reductant supply device having a reductant injection valve with an injection tip that is fixed to an exhaust pipe on the exhaust gas upstream side of a reduction catalyst, the device directly injecting and supplying an urea aqueous solution which is pressure-fed to the reductant injection valve in a state of a liquid fluid, by controlling opening and closing of the reductant injection valve. The device includes a cooling water circulation passage; a flow rate control valve; a temperature sensor for detecting a temperature at the tip of the reductant injection valve; and a controller for controlling the flow rate control valve based on the temperature at the tip such that the temperature at the tip of the reductant injection valve is maintained at a temperature between equal to or higher than a boiling point of the urea aqueous solution and equal to or lower than 130° C.

Description

PRIORITY[0001]This application is a continuation in part of U.S. patent application Ser. No. 12,738,414 entitled “Control Unit and Control Method for Reductant Supply Device”, and filed on Apr. 16, 2010. The aforementioned application is incorporated herein by reference for all purposes.TECHNICAL FIELD[0002]The present invention relates to a reductant supply device and a control method used in an exhaust gas purification device. Particularly, the present invention relates to a reductant supply device that uses a urea aqueous solution as a reductant and that cools a reductant injection valve by circulating cooling water for cooling an internal combustion engine, and a control method for the reductant supply device.BACKGROUND OF THE INVENTION[0003]Generally, exhaust gas discharged from an internal combustion engine, such as a diesel engine, contains nitrogen oxides (hereinafter referred to as NOX) that may have an impact on the environment. As an exhaust gas purification device used t...

AI Technical Summary

Benefits of technology

The present invention is related to a reductant supply device for an internal combustion engine. The device uses the cooling water of the engine to effectively cool the reductant injection valve and prevent excessive cooling or heating of the valve. This prevents metal corrosion and heat damage, and also prevents crystallization of urea near the valve. As a result, stable atomization of the reductant is realized. The device includes a controller that adjusts the flow rate control valve to regulate the temperature of the reductant injection valve between 100°C and 120°C, which prevents metal corrosion and heat damage and also prevents crystallization of urea near the valve. Additionally, the device uses the temperature sensor to estimate the temperature at the tip of the reductant injection valve, without the need for an additional sensor. Overall, this reductant supply device prevents issues related to excessive cooling or heating of the reductant injection valve, which ensures stable atomization of the reductant.

Problems solved by technology

In this type of exhaust gas purification device, if a urea aqueous solution is used as a liquid reductant and the temperature of the urea aqueous solution becomes excessively high, urea is hydrolyzed and crystallized before the urea aqueous solution is injected from the reductant injection valve.

As a result, there is a possibility that a supply system of the liquid reductant will be partially or completely clogged.

As a result, the electromagnetically controlled valve is likely to suffer from heat damage caused by heat being transferred from the exhaust pipe.

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