<p>An injector bracket (10) is provided in an air cleaner (5). The injector bracket (10) comprises a rectifier wall (10a) protruding into a main chamber (5b), and a streamlined guide wall (10b) facing a gas flow M which has passed through an element (8). The injector bracket (10) functions as a partition wall and forms in the air cleaner (5) a separate chamber (10e) isolated from the main chamber (5b). An upstream injector unit (7) is disposed in the separate chamber (10e). The rectifier wall (10a) has a symmetric wing shape.</p>
