EXHAUST PURIFICATION DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

An exhaust gas purification device includes a diesel particulate filter (DPF) for capturing particulate matter (PM) in an exhaust gas, a selective catalytic reduction (SCR) device for reducing NOx in the exhaust gas, detecting units for detecting the DPF electrostatic capacity, an estimating unit for estimating the inside temperature of the DPF based on the electrostatic capacity, and a controlling unit for executing forced DPF regeneration. A lower limit temperature is defined as a temperature to trigger PM combustion, and an upper limit temperature is defined as a temperature to avoid filter erosion. The controlling unit executes the forced regeneration with an amount of fuel supplied for causing the inside temperature to reach the lower limit temperature, when the inside temperature is at or above the SCR activation temperature, and executes the forced regeneration with another amount of fuel supplied for causing the inside temperature to reach the upper limit temperature, when the inside temperature is below the SCR activation temperature.

主权项

1. An exhaust gas purification device of an internal combustion engine, comprising:
a filter that is provided in an exhaust passage of the internal combustion engine and configured to collect particulate matter in an exhaust gas; a urea water spraying unit that is provided in the exhaust passage downstream of the filter and configured to spray urea water into the exhaust gas; a selective reduction catalyst that is provided in the exhaust passage downstream of the urea water spraying unit and configured to reduce and purify a nitrogen compound in the exhaust gas by using ammonia produced from the urea water; an electrostatic capacity detecting unit configured to detect an electrostatic capacity of the filter; a filter temperature estimating unit configured to estimate inside temperature of the filter based on the detected electrostatic capacity; and a filter regenerating unit configured to carry out forced regeneration by supplying fuel to the filter and raising temperature of the filter to or over burning temperature of the particulate matter, the filter regenerating unit being configured to carry out the forced regeneration with an amount of fuel that is supplied to make the inside temperature equal to a predetermined target lower limit temperature, if the estimated inside temperature is equal to or higher than activation temperature of the selective reduction catalyst, the target lower limit temperature being temperature to start burning of the particulate matter, and the filter regenerating unit being configured to carry out the forced regeneration with another amount of fuel that is supplied to make the inside temperature equal to a predetermined target upper limit temperature, if the estimated inside temperature is lower than the activation temperature of the selective reduction catalyst, the target upper limit temperature being temperature to avoid erosion of the filter.