Addition-amount controller for exhaust gas purifying agent and exhaust emission control system

Abstract

In an addition-amount controller for an exhaust gas purifying agent to be used for an exhaust emission control system of an engine, one mode is executed based on satisfaction of an execution condition for each mode, from among a plurality of control modes. The control modes includes a purification control mode in which an addition amount of NH₃ or an additive serving as a generating source of the NH₃ is determined according to a predetermined parameter associated with an amount of NO_x in the exhaust gas, and a storage control mode in which the addition amount is set to be larger than that in the purification control mode. When a rotation speed of an output shaft of the engine is determined to be decelerated from a higher speed state than an allowable level, the execution condition of the storage control mode is satisfied after a predetermined dissatisfaction time period from start of the deceleration.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application is based on Japanese Patent Application No. 2007-168405 filed on Jun. 27, 2007, the contents of which are incorporated herein by reference in its entirety.FIELD OF THE INVENTION[0002]The present invention relates to an addition-amount controller for an exhaust gas purifying agent, for controlling an amount of addition of NH3 for purifying exhaust gas by reaction with NOx in the exhaust gas. The invention also relates to an exhaust emission control system e.g., a urea-SCR system, for purifying exhaust gas by an exhaust gas purifying reaction based on NH3 on a catalyst.BACKGROUND OF THE INVENTION[0003]In recent years, urea-SCR (selective reduction) systems have been developed in electric power plants, various factories, vehicles, and the like. Particularly, in the field of vehicles (especially, a diesel engine vehicle), post treatment techniques of exhaust gas for purifying and reducing NOx (nitrogen oxides) in the exhaust g...

AI Technical Summary

Benefits of technology

[0006]The inventors of the present application take into consideration the facts that the general catalyst for purifying the exhaust gas used in a vehicle-mounted internal combustion engine or the like can store NH3 and that the larger the amount of the stored NH3, the lower the activation temperature (critical reaction temperature) of the catalyst. Thus, the inventors now conduct various studies on and have developed an addition-amount controller for an exhaust gas purifying agent so as to improve an exhaust gas purification capacity using a decrease in activation temperature (critical reaction temperature) due to the storage of NH3.

Problems solved by technology

Thus, even if storing of the NH3 is started at the same time as start of deceleration, the storing of the NH3 may be not effective, and the remaining NH3 not stored may lead to deterioration of emission characteristics.

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