Exhaust treatment device for a diesel engine

An exhaust treatment device for a diesel engine, including a DPF 1, an exhaust gas temperature sensor 40 for detecting a temperature of an exhaust gas 12 on an upstream side of the DPF 1, an intake throttle valve 41, control means 14, and memory means 5, wherein a target temperature DT of the exhaust gas 12 on the upstream side of the DPF 1, a first valve opening degree O1 of the intake throttle valve 41, and set durations T1, T2, T3, and T4 for stage processings of exhaust gas temperature rise processing are stored in the memory means 5, and in regeneration of the DPF 1 by burning and removing PM, accumulated on the DPF 1, by using heat of the exhaust gas 11, the control means 14 performs a first stage processing P1 of the exhaust gas temperature rise processing, wherein in the first stage processing P1, a target rotation number of the engine is set to a predetermined first target rotation number R1 and an opening degree of the intake throttle valve 41 is set to the first valve opening degree O1, if the temperature of the exhaust gas 12 on the upstream side of the DPF 1 does not reach the target temperature DT and the set duration T1 of the first stage processing P1 has elapsed, the control means 14 performs a second stage processing P2 of the exhaust gas temperature rise processing, wherein in the second stage processing P2, the target rotation number of the engine is maintained at the first target rotation number R1 and the opening degree of the intake throttle valve 41 is more closed than the first valve opening degree O1, if the temperature of the exhaust gas 12 on the upstream side of the DPF 1 does not reach the target temperature DT and the set duration T2 of the second stage processing P2 has elapsed, the control means 14 performs stage processings P3 and P4 in and after the third step of the exhaust gas temperature rise processing, wherein in the stage processings P3 and P4 in and after the third step, the opening degree of the intake throttle valve 41 is maintained at a second valve opening degree O2 at the time when the set duration T2 of the second stage processing P2 has reached until the temperature of the exhaust gas 12 on the upstream side of the DPF 1 reaches the target temperature DT, and the temperature of the exhaust gas 12 on the upstream side of the DPF 1 is raised by updating the target rotation number of the engine into target rotation numbers R2 and R3, each higher than each of the target rotation numbers R1 and R2 of the stage processings P2 and P3 right before, based on an elapse of the set durations T3 and T4 of the stage processings P3 and P4.