초록 ▼

An oxidation promoting catalyst (42) which converts nitrogen monoxide in exhaust gas to nitrogen dioxide, and a diesel particulate filter (41) which traps soot in the exhaust gas, are installed in an exhaust gas passage of a diesel engine (1). A control unit (21) determines whether or not it is nece

An oxidation promoting catalyst (42) which converts nitrogen monoxide in exhaust gas to nitrogen dioxide, and a diesel particulate filter (41) which traps soot in the exhaust gas, are installed in an exhaust gas passage of a diesel engine (1). A control unit (21) determines whether or not it is necessary to regenerate the filter based on the exhaust gas pressure detected by an exhaust gas pressure sensor (24), and when it is necessary to regenerate the filter, it increases the nitrogen monoxide in the exhaust gas by performing an advance correction of the fuel injection timing of a fuel injector (14) so as to promote generation of nitrogen dioxide by the oxidation promoting catalyst. The nitrogen dioxide decreases the combustion temperature of the soot trapped by the diesel particulate filter (41), and efficiently regenerates the filter.

대표청구항 ▼

1. An exhaust gas purification device for a diesel engine, the diesel engine comprising a fuel injector, comprising:a diesel particulate filter which traps soot in an exhaust gas of the diesel engine; an oxidation promoting catalyst which oxidizes nitrogen oxide in the exhaust gas to nitrogen dioxid

1. An exhaust gas purification device for a diesel engine, the diesel engine comprising a fuel injector, comprising:a diesel particulate filter which traps soot in an exhaust gas of the diesel engine; an oxidation promoting catalyst which oxidizes nitrogen oxide in the exhaust gas to nitrogen dioxide, the nitrogen dioxide promoting the combustion of the soot trapped by the diesel particulate filter; a sensor which detects a state of the diesel particulate filter, and a programmable controller programmed to: determine whether or not the diesel particulate filter is required to be regenerated from the state of the diesel particulate filter, and advance a fuel injection timing of the fuel injector when the diesel particulate filter is required to be regenerated. 2. The exhaust gas purification device as defined in claim 1, wherein the controller is further programmed to increase the advance amount of the fuel injection timing according to the duration of the state where the diesel particulate filter is required to be regenerated, continues.3. An exhaust gas purification device for a diesel engine, the diesel engine comprising a fuel injector, comprising:a diesel particulate filter which traps soot in an exhaust gas of the diesel engine; an oxidation promoting catalyst which oxidizes nitrogen oxide in the exhaust gas to nitrogen dioxide, the nitrogen dioxide promoting the combustion of the soot trapped by the diesel particulate filter; means for detecting a state of the diesel particulate filter; means for determining whether or not the diesel particulate filter is required to be regenerated from the state of the diesel particulate filter; and means for advancing a fuel injection timing of the fuel injector when the diesel particulate filter is required to be regenerated. 4. A method for regenerating a diesel particulate filter which traps soot in an exhaust gas of a diesel engine, the diesel engine comprising a fuel injector and an oxidation promoting catalyst which oxidizes nitrogen oxide in the exhaust gas to nitrogen dioxide, the nitrogen dioxide promoting the combustion of the soot trapped by the diesel particulate filter, the method comprising:detecting a state of the diesel particulate filter; determining whether or not the diesel particulate filter is required to be regenerated from the state of the diesel particulate filter; and advancing a fuel injection timing of the fuel injector when the diesel particulate filter is required to be regenerated. 5. An exhaust gas purification device for a diesel engine, the diesel engine comprising a fuel injector, an exhaust gas turbine driven by an energy of the exhaust gas prior to flowing into the diesel particulate filter, the exhaust gas turbine driving a compressor for supercharging intake air of the engine, and a mechanism which can decrease the energy of the exhaust gas consumed by the exhaust gas turbine by decreasing a supercharging pressure of the compressor, the device comprising:a diesel particulate filter which traps soot in an exhaust gas of the diesel engine; an oxidation promoting catalyst which oxidizes nitrogen oxide in the exhaust gas to nitrogen dioxide, the nitrogen dioxide promoting the combustion of the soot trapped by the diesel particulate filter; a sensor which detects a state of the diesel particulate filter; and a programmable controller programmed to: determine whether or not the diesel particulate filter is required to be regenerated from the state of the diesel particulate filter; advance a fuel injection timing of the fuel injector, when the diesel particulate filter is required to be regenerated, by controlling the mechanism to decrease the supercharging pressure of the compressor; and increase the advance amount of the fuel injection timing, the longer the state where the diesel particulate filter is required to be regenerated, continues. 6. The exhaust gas purification device as defined in claim 5, wherein the exhaust gas purification device further comprises a temperature sensor which detects a temperature of the exhaust gas, and the controller is further programmed to compare the temperature of the exhaust gas with a predetermined temperature, and prevent the mechanism from decreasing the energy of the exhaust gas consumed by the exhaust gas turbine when the temperature of the exhaust gas is not less than the predetermined temperature.7. The exhaust gas purification device as defined in claim 6, wherein the predetermined temperature is set based on an exhaust gas temperature which maximizes an efficiency of oxidizing nitrogen monoxide to nitrogen dioxide in the oxidation promoting catalyst.8. The exhaust gas purification device as defined in claim 6, wherein the controller is further programmed to control the mechanism to stop decreasing the energy of the exhaust gas consumed by the exhaust gas turbine when the temperature of the exhaust gas reaches the predetermined temperature in a state where the mechanism is decreasing the energy of the exhaust gas consumed by the exhaust gas turbine.9. The exhaust gas purification device as defined in claim 5, wherein the sensor which detects the state of the diesel particulate filter comprises a pressure sensor which detects the exhaust gas pressure of the diesel engine, and the control unit is further programmed to determine whether or not it is necessary to regenerate the diesel particulate filter based on the exhaust gas pressure.10. The exhaust gas purification device as defined in claim 5, wherein the diesel particulate filter and oxidation promoting catalyst are formed as one integrated unit.11. The exhaust gas purification device as defined in claim 5, wherein the oxidation promoting catalyst is disposed upstream of the diesel particulate filter with respect to the flow of exhaust gas from the diesel engine.