Exhaust emission control device of diesel engine

An exhaust emission control device of a diesel engine comprising a diesel oxidation catalyst (DOC) and a diesel particulate filter (DPF) which collects particulate matter (PM) in an exhaust passage and performing regeneration on the PM collected in the DPF,

• the exhaust emission control device comprising:
• a regeneration control unit which increases, when an accumulation quantity of the PM exceeds a predetermined value, a temperature of the DPF to a temperature in a vicinity of a predetermined target set temperature to burn and remove the accumulated PM by controlling a temperature increase unit,
• the regeneration control unit comprising a late post fuel injection control unit which injects fuel into a combustion chamber at a timing when no contribution is made to combustion, the late post fuel injection control unit comprising a DPF target temperature setting unit which sets a target value of a DPF temperature including an inlet temperature, an exit temperature, or an internal temperature of the DPF, and a calculation portion which calculates a late post injection quantity command value based on a deviation between the target value of the DPF temperature set by the DPF target temperature setting unit and an actual DPF temperature,
• the DPF target temperature setting unit comprising a temperature increase rate setting portion which sets a temperature increase change rate such that, until the target set temperature at which the PM is burnt is reached after start of late post injection, the temperature increase change rate is reduced in accordance with an increase in temperature or a period of time elapsed since the start of the late post injection, and
• a target temperature of the DPF temperature being calculated based on the temperature increase rate from the temperature increase rate setting portion.