Abstract: A motor rotor 10 is formed as follows: First, in a first forging step, a hum manufacturing primary block 6A is formed. Next, a second forging step B is effected to form the primary blank 6A into a secondary blank 6B. In this step, a forging die is used to secure an annular yoke 34 to the inner cylindrical surface 61a of a hub cylindrical portion 61 by punching, in such a manner that both whole edges of the annular yoke are sealingly closed thereby. In the second forging step B, by drawing the inner cylindrical surface 34a of the annular yoke, its circularity is improved. The annular yoke can be secured to the hub cylindrical portion with use of an adhesive agent. Moreover, the annular yoke can be fixed in such a manner that it is accurately coaxial with the hub cylindrical portion. In addition, the gap between the annular yoke and the hub cylindrical portion can be eliminated.

Abstract: A disc drive motor comprises a fixed a fixed shaft, a ball bearing fitted on the fixed shaft, a cylindrical hub rotatably supported by the ball bearing, a clamper for fixing a disc to the hub and a cap secured to the hub so as to cover one open end of an opening portion of the hub. The cap includes an engaging element formed as part of the cap for engaging with a rotation stopper jig in order to stop rotation of the hub when clamping the discs. The engaging element includes a protruding or recessed portion of the cap. The engaging may be in the form of a polygon or, in particular, a regular polygon.

Abstract: A current feed means is connected to an armature coil of a motor. Current is fed from the current feed means to the armature coil while the frequency of the current is gradually varied from a preset frequency to another preset frequency, thereby to vibrate the motor. The amplitudes of the frequencies are measured by a frequency analyzer means, which is brought into contact with the motor. The frequency at which the amplitude of the vibration of the motor is peaked indicates the natural frequency of the motor.

Abstract: A magnetic disc drive device includes a labyrinth structure proximate to the ball bearings to effectively prevent scattering of particles. The labyrinth structures are formed by various arrangements where complicated passages are defined by elements arranged proximate to the inner ring and the outer ring of a ball bearing. One of the elements forming the passages being either the hub or the frame of the magnetic disc drive device.

Abstract: A disk drive motor having a center shaft, a pair of ball bearings inner rings thereof being fixedly fitted with the center shaft while interposing a predetermined distance therebetween, a hub being supported so as to be rotatable about the center shaft while having outer rings of the ball bearings fixed to an inner hole thereof, a drive magnet integrally rotating the hub, a stator core being arranged so as to confront the drive magnet, and a first seal means and a second seal means being respectively arranged along ways to a space outside the motor to constitute seal mechanisms while communicating the respective ball bearings with the space outside the motor, wherein an annular spacer is fixedly fitted with the center shaft between the inner rings of the pair of ball bearings and an outer circumferential surface of the spacer confronts an inner circumferential surface of the inner hole of the hub while interposing a small gap therebetween, so that a labyrinth seal mechanism is formed.

Abstract: A magnetic disk drive device has a hub for driving a magnetic disk when the magnetic disk is placed on the hub. A drive magnet is fastened to the inner surface of the hub. A stator core, with a coil wound thereabout, is located in opposition to the drive magnet. A frame is provided for fixedly supporting the stator core. A cutout portion is formed in the bottom of the frame, and a flexible printed circuit is disposed within the cutout portion. The coil terminal wires of the stator core and flexible lead wires are connected to the flexible printed circuit. A plural number of protrusions integral with the frame are disposed within the cutout portion. An arc-shaped lead wire holder, which is arc-shaped along the circumference of the frame, is fitted to the plural number of protrusions.