| 摘要 |
PURPOSE:To prevent the generation of a drift current in the axial direction of a fan and to prevent the occurrence of surging phenomenon, by a method wherein ribs having a uniform height, width, and mounting pitch are formed on the whole area on the discharge side of the rear plate of a casing, and a part of the ribs has the mounting pitch lower than that of the rest. CONSTITUTION:A rib 4 is sized to have a height h1 from the inner surface of a rear plate 3 of a casing, width (t) and a length (l), and the ribs are integrally molded at equal intervals of a pitch distance p1. In a region Y, the width and length of the rib are the same as those in a region X, and the ribs are integrally molded at a pitch distance p2 and with a rib height, h2, (p1>P2, h1<h2). As noted above, since in a section (two end parts) having low air resistance, ribs 4' having the height higher than that of the rib in a region X are formed a region Y being a position on the downstream thereof and a mounting pitch distance is decreased, the draft area of an air discharge passage 9 is decreased and throttled. A drift current W flowing from a place having high intake air resistance to a place having low intake air resistance can be prevented from generation, resulting in the possibility to prevent the occurrence of surging phenomenon. |
