Abstract: Forced regeneration start timing of a diesel particulate filter for purifying particulate matter in exhaust gas is judged based on a comparison of a differential pressure across the diesel particulate filter with a predetermined differential pressure threshold across the filter. The predetermined differential pressure threshold is set by multiplying a reference differential pressure threshold by a coefficient which varies stepwise or continuously depending on a mileage of a vehicle after previous forced regeneration. Consequently, particulate matter can be removed by burning while the amount of particulate matter accumulated unevenly in the filter is still small, and excessive temperature rise in the filter resulting from excessive accumulation of particulate matter during forced regeneration and melting-loss of the filter due to excessive temperature rise can be prevented.

Abstract: An exhaust emission purification system having a controller performing exhaust temperature rise control including multistage delay injection control for raising the exhaust temperature, if the exhaust gas temperature is lower than a predetermined judgment temperature, and performing particulate matter combustion removal control including post injection control, if the exhaust gas temperature becomes equal to or higher than the predetermined judgment temperature, when forced regeneration of a diesel particulate filter is carried out. The multistage delay injection control is forbidden when an idle operation state of an internal combustion engine occurs for a predetermined judgment time and a power take-off device is operating.

Abstract: When switching an exhaust throttle valve from full opening to a closed position to warm up an engine, an intake throttle valve is fixed to full opening, an EGR valve is fixed to full closing, and a variable turbo-vane is fixed to a predetermined opening degree to accelerate a gas flow rate from an intake passage to an exhaust passage, a fully opened flow rate is detected and stored by gas flow rate detector, with the exhaust throttle valve being full opening. Then, an instruction is issued to the exhaust throttle valve to switch from the full opening to a closed position, after which a rotation number of the engine is detected, a threshold value is determined based thereon, a closed position flow rate is detected, a flow rate difference relative to the stored fully opened flow rate is determined, and failure of the exhaust throttle valve is judged based on whether the flow rate difference is less than the determined threshold value.

Abstract: A fuel pressure sensor diagnosing device for diagnosing a fuel pressure sensor for detecting pressure in a common rail in which a high-pressure fuel to be supplied to an engine is accumulated, the device comprising: fuel temperature detection for detecting fuel temperature; and failure determination, provided with the fuel temperature detection for detecting fuel temperature via subsequent to stopping of the engine, for obtaining a resting and stabilization time between when the pressure in the common rail drops and when the pressure stabilizes on the basis of this detected fuel temperature, detecting a stabilized fuel pressure via the fuel pressure sensor subsequent to lapse of the resting and stabilization time, and determining a failure of the fuel pressure sensor when the detected stabilized fuel pressure exceeds a predetermined upper limit threshold value or is less than a predetermined lower limit threshold value.

Abstract: An exhaust emission purification system including a controller performing exhaust temperature rise control executing multistage delay injection control for raising the exhaust temperature, if the exhaust gas temperature is lower than a predetermined judgment temperature, and performing particulate matter combustion removal control executing post injection control, if the exhaust gas temperature becomes equal to or higher than the predetermined judgment temperature, when forced regeneration of a diesel particulate filter is carried out. Multistage delay injection control is forbidden when an idle operation state of an internal combustion engine is sustained for a predetermined judgment time and a power take-off is in operating state. The diesel particulate filter is thereby kept in a good state in a vehicle equipped for purifying particulate matter in exhaust gas by executing forced regeneration while avoiding variation in engine speed.

Abstract: In an exhaust emission purification method and an exhaust emission purification system where forced regeneration start timing of a DPF for purifying the PM (particulate matters) in exhaust gas is judged based on the comparison of a differential pressure across the DPF with a predetermined differential pressure threshold across the DPF, a differential pressure threshold (?Ps) across the DPF is set by multiplying a reference differential pressure threshold (?Ps0) across the DPF by a coefficient (?(?M)) which varies stepwise or continuously depending on the mileage (?M) of a vehicle after previous forced regeneration. Consequently, the PM can be removed by burning while the amount of PM accumulated unevenly in the DPF is still small, and excessive temperature rise in the DPF resulting from excessive accumulation of PM during forced regeneration and melting-loss of DPF due to excessive temperature rise can be prevented.

Abstract: A fuel pressure sensor diagnosing device for diagnosing a fuel pressure sensor for detecting pressure in a common rail in which a high-pressure fuel to be supplied to an engine is accumulated, the device comprising: fuel temperature detection means for detecting fuel temperature; and failure determination means, provided with the fuel temperature detection means for detecting fuel temperature via subsequent to stopping of the engine, for obtaining a resting and stabilization time between when the pressure in the common rail drops and when the pressure stabilizes on the basis of this detected fuel temperature, detecting a stabilized fuel pressure via the fuel pressure sensor subsequent to lapse of the resting and stabilization time, and determining a failure of the fuel pressure sensor when the detected stabilized fuel pressure exceeds a predetermined upper limit threshold value or is less than a predetermined lower limit threshold value.

Abstract: When switching an exhaust throttle valve from full opening to a closed position to warm up an engine, an intake throttle valve is fixed to full opening, an EGR valve is fixed to full closing, and a variable turbo-vane is fixed to a predetermined opening degree to accelerate a gas flow rate from an intake passage to an exhaust passage, a fully opened flow rate is detected and stored by gas flow rate detection means, with the exhaust throttle valve being full opening, after which an instruction is issued to the exhaust throttle valve to switch from the full opening to a closed position for detecting a closed position flow rate, a flow rate difference is determined by deducting the detected closed position flow rate from the stored fully opened flow rate, and failure of the exhaust throttle valve is judged when the flow rate difference is less than a predetermined threshold value.