| 摘要 |
An exhaust gas purification apparatus includes an exhaust passage through which exhaust gas discharged from an engine flows, a selective s catalytic reduction catalyst provided in the exhaust passage, a urea water supply device for supplying urea water into the exhaust passage upstream of the selective catalytic reduction catalyst, a sensor responding to respective quantities of NOx and ammonia downstream of the selective catalytic reduction catalyst and detecting a value based on the response by the sensor, an 10 exhaust gas recirculation passage through which a part of exhaust gas is refluxed to an intake system of the engine, an exhaust gas recirculation control valve for controlling amount of exhaust gas that is refluxed through the exhaust gas recirculation passage and a control device for controlling quantity of urea water supplied from the urea water supply device to the exhaust passage and 15 also opening and closing of the exhaust gas recirculation control valve. The control device controls opening and closing of the exhaust gas recirculation control valve so as to increase or decrease the amount of exhaust gas refluxed through the exhaust gas recirculation passage for a predetermined period of time and also determines quantity of urea water based on change between the 20 values detected by the sensor before and after changing opening and closing of the exhaust gas recirculation control valve. 2451114_1 (GHMatters) 26/10/10 0 ----------- 13 23 /24 intake 26 exhaust 8 22 ----7--|2 313 16 / 8 1 ------ 33 3 |
