Exhaust gas purification device of internal combustion engine

Abstract

The invention provides an exhaust gas purification device of an internal combustion engine. The exhaust gas purification device of an internal combustion engine comprises a urea water supply mechanism that adds urea water to exhaust gas, a SCR catalyst that adsorbs ammonia and removes NOx in the exhaust gas by using the adsorbed ammonia, and a control device that controls a urea water addition amount based on a target adsorption amount for the ammonia adsorbed onto the SCR catalyst. The control device executes an integration processing that acquires a temperature of the SCR catalyst at a predetermined cycle and integrates the acquired temperature of the SCR catalyst when equal to or higher than a threshold, and an initialization processing that decreases the amount of the ammonia adsorbed on the SCR catalyst on a condition that an integrated value of the temperature of the SCR catalyst calculated in the integration processing has become equal to or higher than a predetermined value.

Description

technical field [0001] The present invention relates to an exhaust purification device for an internal combustion engine. Background technique [0002] There is known an internal combustion engine provided with a catalyst for purifying nitrogen oxides (NOx) in exhaust gas (for example, Patent Document 1, etc.). An addition mechanism for adding urea water to exhaust gas is provided in the exhaust passage of such an internal combustion engine, and ammonia generated from the urea water is adsorbed on a NOx purification catalyst. Then, NOx is reduced and purified by ammonia adsorbed on the catalyst. [0003] If the amount of ammonia adsorbed by the catalyst is insufficient, proper purification of NOx will not be performed. Conversely, if the amount of ammonia adsorbed is too large, ammonia slip will easily occur. Therefore, it is preferable to set a target adsorption amount of ammonia adsorbed on the catalyst, and to execute ammonia adsorption amount control for controlling th...

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Problems solved by technology

[0007] However, in the device described in Document 1, if there is an error in the estimated value of the amount of ammonia adsorption itself, there is a possibility that the above-mentioned deviation cannot be accurately calculated.

In this case, if the deviation is calculated incorrectly and the deviation does not reach a predetermined value or more, the state of not performing the above initialization process continues, so there is a concern that the above error will increase.

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