Importance

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Abstract

The purpose of the present invention is to provide an exhaust purification device that is capable of adding an appropriate amount of urea solution without the need to directly measure the NOx emissions amount using an NOx measuring means. The exhaust purification device uses urea solution as a reducing agent for reducing nitrogen oxides within exhaust, and is provided with a temperature sensor, a humidity sensor, and a control device. A map is stored in the control device, and in said map the real NOx emissions amount for each rotation speed and each load of an engine occurring at a predetermined air temperature and a predetermined absolute humidity are converted using a correction formula into a reference NOx emissions amount for each rotation speed and each load of the engine while in a standard state. Using the map, the control device calculates a reference NOx emissions amount that corresponds to the rotation speed detected by a rotation speed sensor and to the load detected by a load sensor, uses the correction formula to convert the reference NOx emissions amount into the real NOx emissions amount occurring at an air temperature and an absolute humidity, and calculates a urea solution addition amount.

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First Claim