JPS5765811A - Exhaust gas purifier for diesel engine - Google Patents

Abstract

PURPOSE:To make it possible to reform a filter for trapping carbon particles even in engine operation by shutting-off a valve positioned downstream of the filter, in a predetermined period, for raising a temperature in the inside of the filter when the engine operated under the intermediate load. CONSTITUTION:Exhaust gas discharged from an engine 1 and containing carbon particles is purified through a filter 4 made of ceramic or the like, and is discharged to the atmosphere. When the filter 4 is blocked, backpressure is increased, which is detected by a pressure sensor 12 disposed upstream of the filter 4. Therefore, the sensor 12 produces a signal S2. Further, when a detector 13 detects the condition that the engine is operated under the intermediate load, it produces a signal S3. Therefore, if both signals S2, S3 are applied to a controller 11 which, therefore, generates a signal S1 during the period that is set by a timer 14 within a range 1-10sec, a passage communicating to an operating chamber 7b in a diaphragm unit 7 actuating a shut-off valve 5 which is disposed in an exhaust pipe downstream of the filter 7, is diverted to communicate with a negative pressure source 10 by a 3-way valve 5 which switches the passage opened to the atmosphere, by receiving the S1, so as to be in communication with the negative pressure source. Thereby the valve 5 is closed to raise a temperature in the inside of the filter, resulting in that carbon particles are burnt, thereby to reform the filter.