| 摘要 |
PURPOSE:To improve responsiveness, by providing a 2nd magnetic circuit part which forms a magnetic circuit jointly with a 1st magnetic circuit part combined with a stage member and the 1st magnetic circuit part, and a magnetic dumper including the magnetic fluid arranged in a gap. CONSTITUTION:Magnetic fluids 7, 8 change a friction force for the relative speed between an annular york 5 and a magnet device 1. Namely the force generated in accordance with the relative speed becoming faster, becomes larger. In the case of a wafer chuck 10 starting motion, the braking force by the effect of a magnetic fluid is almost 0 even in case of its presence, but the speed is increased according to the wafer chuck 10 being driven, the braking force is generated according to the speed. The control of a generating speed is effectively executed due to the braking like this, and the hunting due to an overchute is reduced. The responsiveness is thus improved, and the time until controlling the stage member to a target position can be shortened. |
