| 摘要 |
PURPOSE:To make is possible to prevent an engine from over-heating even during dust being blown off from a dust-free air sucking means, by locating an auxiliary dust-free air sucking section of the dust-free air sucking means at an external position where dust can hardly be sucked into. CONSTITUTION:A dust-free air sucking means 6 having a main dust-free air sucking section 8 and an auxiliary dust-free air sucking section 9 is disposed on the sucking side of a cooling fan 1 for cooling an engine E. In this arrangement, the auxiliary dust-free air sucking section 9 is located at a position which is outside of the main dust-free air sucking section 8 and at which dust can hardly be sucked, and a dust blowing-off means 11 is arranged being faced to the main dust-free air sucking section 8. In this arrangement, during blowing-off operation of an electrical motor 14, blowing- off air 13 is blown through the main dust-free air sucking section 8 from the inside to the outside thereof so as to blow off dust 7 sticking to the outside of the main dust-free air sucking section 8. During the blowing-off process of this dust 7, the cooling fan 1 continuously rotates in a normal direction so as to suck a large volume of the outside air through the auxiliary dust-free air sucking section 9 to which only a slight quantity of dust sticks, and accordingly the engine E is cooled continuously, thereby it is possible to prevent the engine E from overheating. |
