To firstly suppress deformation of a part where a bearing of a bearing housing formed by press drawing of a metal thin sheet is arranged and vibration of the bearing and to secondly suppress sliding of the bearing while the bearing housing is kept removable when it is repaired.

At first, a metal ring 44 is fitted on a part where the bearing 41 of the bearing housing 36 is arranged and rigidity of the part is made larger than those of the other parts. Secondly, the bearing 42 is made to be a ball bearing and the inner ring is brought into press contact with the outer periphery of a dehydrating shaft 43 and a gap is formed between the outer ring and the inner periphery of the bearing housing 36 and an annular elastic body 55 with an outer diameter projected larger than the dimension of the gap from the outer periphery of the outer ring is mounted on the outer periphery part of the outer ring and the outer ring is inserted into the inner periphery of the bearing housing 36 through this elastic body 55.