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Magnetic bearing apparatus
| Details |
Inventors: Ueyama, Hirochika; Taniguchi, Manabu;
Assignee: Koyo Seiko Co., Ltd. (Osaka, JP)
Primary Examiner: Dougherty; Thomas M.
Assistant Examiner: Jones; Judson H.
Attorney, Agent or Firm: Rabin, Champagne, & Lynt, P.C.
A magnetic bearing apparatus comprises a pair of radial magnetic bearings arranged on both sides in the axial direction of an axial magnetic bearing. A pair of first touchdown bearings are arranged at both ends of a spindle. Annular slide bearings are mounted as second touchdown bearings for receiving the spindle on inner peripheral parts of electromagnets in the axial magnetic bearing. The radial internal clearance between the slide bearing and the spindle is larger than the radial internal clearance between the first touchdown bearings and the spindle and is smaller than the radial internal clearance between the radial magnetic bearings and the spindle. Even if a central part of the spindle is deflected at the time of emergency stop, both the first touchdown bearings and the slide bearings receive the spindle, so that the load on the first touchdown bearings can be reduced. |
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DETAILED DESCRIPTION An object of the present invention is to provide a magnetic bearing apparatus capable of preventing touchdown bearings from being damaged at the time of emergency stop of a spindle.
In order to attain the above-mentioned object, in a preferred mode of the present invention, a magnetic bearing apparatus comprises a spindle passed through a housing, a rotor disc fixed to an approximately central part in the axial direction of the spindle, an axial magnetic bearing supported by the housing and including a pair of electromagnets with the rotor disc interposed therebetween for axially supporting the spindle with a clearance therebetween, a pair of radial magnetic bearings supported by the housing in positions on both sides in the axial direction of the axial magnetic bearing for radially supporting the spindle with a clearance therebetween, a pair of first touchdown bearings supported by the housing and opposite to both ends in the axial direction of the spindle, and a pair of second touchdown bearings supported by the housing and opposite to the approximately central part in the axial direction of the spindle.
The radial internal clearance between the second touchdown bearings and the spindle is made larger than the radial internal clearance between the first touchdown bearings and the spindle and smaller than the radial internal clearance between the radial magnetic bearings and the spindle.
According to the present embodiment, even if an excessive force is applied to the spindle or the central part of the spindle is deflected at the time of emergency stop, the second touchdown bearings in the approximately central part of the spindle, together with the first touchdown bearings, receive the spindle.
Consequently, the load on the first touchdown bearings can be reduced.
As a result, it is possible to prevent the first touchdown bearings from being damaged.
Even if the first touchdown bearings are damaged, the spindle can be supported by the second touchdown bearings until the spindle is stopped
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