| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an NOx detecting device capable of relatively accurately detecting an NOx quantity passing through an exhaust gas passage per unit time even if the NOx concentration is relatively low. <P>SOLUTION: This NOx detecting device includes a holding part 42 for discharging and reducing holding NOx by a reducing substance when reducing the oxygen concentration in exhaust gas, a temperature sensor 41 for measuring the temperature of the holding part and an oxygen concentration reducing means 44 for reducing the oxygen concentration around the holding part, and starts reduction in the oxygen concentration around the holding part by the oxygen concentration reducing means after a first preset time from when holding no NOx in the holding part when the air-fuel ratio of the exhaust gas is leaner than the stoichiometric air-fuel ratio, and detects a temperature rise value of the holding part after a second preset time after starting the reduction in the oxygen concentration around the holding part by the oxygen concentration reducing means, and detects the NOx quantity in the exhaust gas passed through the exhaust gas passage for the first preset time based on the temperature rise value when the second preset time is a shorter time than the first preset time. <P>COPYRIGHT: (C)2011,JPO&INPIT |
