Exhaust gas purifying device for engine

Abstract

An exhaust gas purifying device for an engine according to the present invention includes a NOx absorbing catalytic converter provided in an exhaust path of the engine, an exhaust light oil adding injector which supplies a reducing agent component into the exhaust path, a control unit which executes the rich spike operation that controls an air-fuel ratio to the rich side per predetermined time, which adds the HC component to the NOx absorbing catalytic converter, and which heats to an S purge temperature or higher so as to eliminate a sulfur component absorbed by the NOx absorbing catalytic converter, and a catalyst temperature measuring sensor which measures the temperature of the NOx absorbing catalytic converter, wherein the control unit controls an operation cycle of the rich spike operation based on the deviation of the S purge temperature with respect to the temperature measured by the catalyst temperature measuring sensor.

Description

technical field [0001] The invention relates to a device for purifying exhaust gas of an engine. The device has the function of purifying exhaust gas and can purify harmful components contained in the exhaust gas of an internal combustion engine. The invention particularly relates to the control of catalyst temperature rise during sulfur purification driving. Background technique [0002] Conventionally, there is known an exhaust gas purification device provided with a catalytic converter that absorbs NOx in an engine exhaust pipe. For an exhaust gas purification device using such a NOx catalyst, in order to discharge and reduce absorbed NOx, it is necessary to periodically (for example, once a minute) perform a rich combustible component intensive operation by reducing the NOx in the exhaust gas of the catalytic converter A reducing agent such as light oil is supplied at the exhaust upstream side to reduce the air-fuel ratio (hereinafter referred to as "lambda before cataly...

AI Technical Summary

Problems solved by technology

Since combustible-rich enhanced operation and sulfur purification drive are both implemented by adding exhaust gas light oil or performing post-injection to supply HC, the operation of supplying HC to the catalyst may be overly dependent on timing pulses, which may cause excessive temperature rise of the catalyst

[0007] Therefore, although preventive measures to prevent excessive supply of HC by reducing the supply of CO, HC while driving sulfur purification can be conceived, on the contrary, the problem is that the time to reach the sulfur purification temperature is delayed or the sulfur purification temperature cannot be reached at all

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