North American Philips Corporation

U.S. Philips Corporation

Ping-Shih Wang

Bernd Ackermann

Elmer W Madsen

Ekkehard Bolte

Leo Honds

Jelm Franse

Anton Hammers

Klaus Stips

An improved spindle motor, particularly for a hard-disc drive, having a stator in the form of a cylindrical coil carried by a mounting plate and a permanent magnet rotor carried on a rotatable hub. At its outer circumference the rotor generates a field perpendicular to the axis of rotation. A bell-shaped portion of the hub surrounds the coil. The hub is supported on the motor shaft by axial and radial hydrodynamic bearings. A soft-iron sleeve-shaped yoke externally surrounds the coil configuration. This permits the coil to be free of soft-magnetic parts, thereby reducing its inductance and improving the dynamic drive characteristics of the motor. The coil is preferably formed by curved foil windings, so there are no winding slots. This avoids the production of detent torques.

Electric motor having a stator and a rotor

The invention relates to an electric motor with permanent-magnet excitation, particularly inside-rotor and outside-rotor motors, comprising motor sections (10, 20) which are movable relative to one another, of which the first motor section (10) forms a multi-pole excitation field in an air gap (1) by means of permanent magnets (11) and of which the second motor section (20) is a soft-iron yoke (21) having pole teeth (22) which project towards the air gap (1) and which carry excitation coils (23). The motor combines the following characteristic features:

Electric motor with permanent-magnet excitation

A stepper motor, having a permanent magnet rotor rotatably mounted within the annulus of a stator winding, also has a rotatable spring magnet and a stationary bias magnet. The spring magnet is attached to the rotor and is disposed adjacent the stationary bias magnet. When the stator winding is not energized, the rotor assumes a home position established by the spring and bias magnets. When the stator winding is energized, the rotor is rotated away from the home position by an angular displacement determined by the winding current.

Variable angle stepper motor with spring magnet

A stepper motor having a permanent magnet rotor rotatably mounted within the annuli of a stator winding and a bias magnet. When the stator winding is not energized, the rotor assumes a home position established by the bias magnet. When the stator winding is energized, the rotor is rotated away from the home position by an angular displacement determined by the winding current.

Variable angle stepper motor

A hybrid stepper motor having two alternately excited magnetic systems, one providing positions of 0.degree. and 180.degree., and the other positions of 90.degree. and 270.degree.. To minimize position offset due to unequal flux through the two air gaps of the unexcited system, a nonmagnetic space is provided to reduce the relative difference in reluctance between the magnetic paths which include the two air gaps of the unexcited magnetic system.

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Cheshire, CT, United States of America

Ping-Shih Wang