Bearing device with a primary and secondary magnetic fluid sealing mechanism

DETAILED DESCRIPTION It is therefore an object of the invention to provide a bearing device which can prevent magnetic fluid from leaking, reduce contamination outside of the bearing device caused by dust and gases, and prevent a shortage of magnetic fluid from occurring within the bearing device.
In accordance with one aspect of the invention, a bearing device used in a motor is described, where the motor includes a shaft made of a magnetic material and a frame made of a magnetic material.
This bearing device includes: a bearing connected to one of the shaft and the frame; a magnetic fluid filled in a space between the shaft and the frame; a primary magnetic fluid sealing means for sealing said magnetic fluid, where the primary magnetic fluid sealing means produces an axial magnetic flux density gradient in the space which increases unidirectionally in a direction away from an open end of the frame, and the primary magnetic fluid sealing means is located closer to the open end of the frame than the bearing; and, a secondary magnetic fluid sealing means for sealing the magnetic fluid, where the secondary magnetic fluid sealing means is located closer to the open end of the frame than the primary magnetic fluid sealing means.
In accordance with another aspect of the invention, a bearing device is described which includes: a radial bearing fixed to one of a fixed member and a revolving member, where the radial bearing is adapted to rotatably support the revolving member; a magnetic fluid filled in a region between the radial bearing and the revolving member; a magnet mounted to one of the fixed member and the revolving member, where the magnet is located closer to an open end of the frame than the radial bearing; a magnetic body mounted to one of the fixed member and the revolving member, where the magnetic body is oriented to radially face the magnet; and, a magnetic fluid sealing plate which is located closer to the open end of the frame than the magnet, where the magnetic fluid sealing plate is made of a nonmagnetic material with a surface that allows the magnetic fluid coming into contact with the surface to form into one of a bead or a droplet