PURPOSE:To prevent the occurrence of cracking due to thermal stresses by providing an independent heater and an independent temperature sensor for the center section at the front surface of a particular trap and its periphery section respectively, and thereby controlling each heater to be energized in such a way that the difference in temperature between the center section and the periphery section is maintained to be within a specified range. CONSTITUTION:Heaters 2 and 3 are arranged at the center and periphery sections of a trap 1 respectively, which act as the after burning device of the parculate trap 1 arranged in the exhaust system of a diesel engine so that these are controlled in energizing by a controller 12. The controller 12 closes an inlet valve 11 when it is detected by the output signal from a pressure difference sensor P1 based on the difference in pressure at the front and rear position of the trap 1 that time reaches the timing for after-burning so as to open a bypass valve 10 for performing after-burning. Namely, the output signals of temperature sensors 6 and 7 which detect the temperature at the center section and its periphery section respectively, are read therein, each heater 2 and 3 is thereby controlled to be turned on/off for a specified period of time in such a way that the difference in temperature between both of the sections is maintained to be within a specified permissible range, so that gas is led in thereafter so as to start after-burning.
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