Hitachi, Ltd.

Hitachi Powdered Metals Co., Ltd.

Michihiro Aizawa

Katsutoshi Nii

Hideo Shikata

Motohiro Miyasaka

Hidekazu Tokushima

An oil impregnated porous bearing unit includes an arrangement wherein an oil impregnated porous bearing containing ferro-fluid is fixed in a non-magnetizable housing, a ring shaped permanent magnet is disposed so that the ferro-fluid will exist in a gap between a rotary shaft, whereon the ring shaped permanent magnet is fixed, and the oil impregnated porous bearing, and the ferro-fluid circulates between a slide plane of the bearing and a body of the oil impregnated porous bearing with rotation of the rotary shaft by utilizing the magnetic attractive force of the permanent magnet and a capillary phenomenon in the oil impregnated porous bearing. In addition, a spiral groove may be provided in an exterior circumferential surface of the permanent magnet fixed to the rotary shaft or in an interior circumferential surface of the housing facing the above exterior circumferential surface of the permanent magnet in order to generate dynamic pressure at the spiral groove portion with rotation of the rotary shaft so as to supply ferro-fluid to the oil impregnated porous bearing.

Oil impregnated porous bearing units and motors provided with same

A magnetic fluid bearing unit has a bearing housing, a bearing member having magnetic fluid as a lubricating agent, a rotary body rotatively supported by the bearing member, an upper permanent magnet arranged inside the bearing housing, and a lower permanent magnet arranged inside the bearing housing, the bearing member being sandwiched by the upper permanent magnet and the lower permanent magnet. The bearing member is a radial porous oil-containing bearing member in which the magnetic fluid is impregnated. The upper permanent magnet is set to have one direction of magnetic pole orientation, and the lower permanent magnet is set to have the same direction of magnetic pole orientation as the upper permanent magnet. The bearing member is sandwiched by the upper permanent magnet and the lower permanent magnet to confine the magnetic fluid. Over a wide range of rotation speeds, the leakage and the scattering of the magnetic fluid from the bearing unit can be prevented. The bearing unit for a compact size motor having a high rotation accuracy can be obtained.

Magnetic fluid bearing unit structure and motor having the same

A bearing unit in which two oil sintered slide bearings are fitted in a bearing space of non-magnetic bearing housings to be spaced away from each other and a magnetic fluid is interposed between a rotary shaft and the oil sintered slide bearings to rotatably support the rotary shaft. The rotary shaft is made from a material having permeability, and a ring-shaped permanent magnet is fixedly provided between the two oil sintered slide bearings to be spaced therefrom. The magnetic fluid is held between the two oil sintered slide bearings to be circulated.

Growing community of inventors

Matsudo, Japan

Michihiro Aizawa