| 摘要 |
<p>An internal combustion engine exhaust gas purification apparatus purifies exhaust gas using a NOx storage-reduction catalyst unit (22) and a NOx selective reduction catalyst unit (23). The NOx selective reduction catalyst unit (23) is provided downstream of the NOx storage-reduction catalyst unit (22) in an exhaust gas passage (18). This apparatus further has urea injecting means (24) and urea injection controlling means (50). The urea injecting means (24) is, for example, an injection valve for injecting urea into the exhaust gas passage (18). The urea injection controlling means (50) prohibits urea injection from the urea injecting means (24) if at least one of the temperatures of the NOx storage-reduction catalyst unit (22) and the NOx selective reduction catalyst unit (23) is equal to or lower than a reference temperature. As such, the production of cyanic acid is minimized, and therefore leaks of cyanic acid from the NOx storage-reduction catalyst unit (22) and/or the NOx selective reduction catalyst unit (23) can be suppressed.</p> |
