Hitachi, Ltd.

Ichiro Hashimoto

Katsutoshi Nii

Takeshi Nakajima

Sueo Akashi

Giichi Ishida

Kunio Miyashita

Hiroshi Hayashida

Koujirou Yamashita

Kosho Ishizaki

Satosi Uno

Tomoyuki Saitou

Nobukatu Sone

Fusanori Ohira

A motor has a rotor mounted on a stator to rotate about a rotation axis. The rotor is driven due to the interaction of a drive coil on the stator and a permanent magnet on the rotor. A magnetic thrust bearing, having permanent magnets on the stator and rotor, applies a radial thrust force. The radially outer surface of the permanent magnet on the rotor abuts a part of the rotor, so as to resist forces on the permanent magnet at high speed rotation or due to thermal deformation. The permanent magnets on the stator and the rotor may be axially offset by an offset of not more than 1/4 the axial length of the permanent magnets, or the axial length of the longer of the permanent magnets if they have different axial lengths. This generates an axial thrust at the thrust bearing, which counteracts the attractive force between the permanent magnet and the drive coil, and also the weight of the rotor.

Motor, a printer having such a motor and a disk drive system having such

A rotary body bearing apparatus has a bearing supporting member, a radial bearing member, a bearing chamber formed in the bearing supporting member for holding the radial bearing member, a rotative shaft supported rotatively by the radial bearing member, and lubricating oil filling a bearing clearance between the rotative shaft and the radial bearing member. An air bubble restraint means restrains the occurrence of air bubbles generated in the lubricating oil by the rotation of the rotative shaft. Even when the rotative shaft rotates at the high speed of rotation, by the provision of the air bubble occurrence restraint means, the occurrence of air bubbles generated in the lubricating oil can be restrained, high accuracy rotation can be maintained and a rotation number fluctuation of the rotary body can be reduced.

Rotary body bearing apparatus, motor and polygon mirror motor

A motor has a stator with a base part and a hollow projection as well as a rotor with a shaft which extends into the hollow projection. A radial bearing is mounted between the shaft and the hollow projection. There may be a further radial bearing in the base part of the stator. The radial bearing, lubricated by magnetic fluid, is sealed between the shaft and the projection by a magnetic seal at the end of the hollow projection remote from the base part. The rotor has an annular part extending around the hollow projection, which supports permanent magnets forming an armature. Those permanent magnets interact with drive coils on the stator to cause rotation of the rotor about the axis of the shaft. There is also a magnetic thrust bearing between the annular part of the rotor and the projection of the stator. This magnetic thrust bearing is axially displaced relative to the magnetic seal towards the base part of the stator, to counteract the effect of the magnetic thrust bearing on the magnetic seal.

Motor with a bearing lubricated by magnetic fluid

A step motor which comprises a stator having a winding wound therearound, a rotor rotatably provided with respect to the stator, a multiplicity of pole teeth formed on mutually opposing faces of the stator and rotor, a position detector for detecting a position of the rotor, and switching means for changing over a phase current flowing through the winding wound around the stator on the basis of a position signal indicative of the position of the rotor, wherein the pole teeth and a position detectable portion are integrally formed on a rotary yoke of the rotor and the position detectable portion is detected by the position detector. A method for recording a position signal of the rotor in the step motor, wherein, when the position detectable portion is made in the form of a magnetic recording medium, the pole teeth are formed on a predetermined surface of a rotary yoke of the rotor, a magnetic recording medium is provided on a surface of the rotary yoke which is not provided with the pole teeth, and a position detecting signal is magnetically recorded on the magnetic recording medium with respect to a reference position of the pole teeth.

Step motor and method for recording position signal of motor rotor

A cylindrical field system of a low speed high torque motor is divided in an axial direction into first and second field system portions, these two field system portions are connected by a connecting member and a field magnet is disposed between the field system portions so that particularly machine work can be made before fitting of the field magnet. Accordingly, chips can be removed easily by use of a simple device. A cylindrical field system is divided in an axial direction into first and second field system portions, these field system portions are connected by a connecting member and cylindrical magnets fixed to a flexible belt-like fixture are wound on the field system portions between them so as to produce a rotor. Accordingly, the assembling property of the motor can be improved remarkably.

Low speed high torque motor with production method

A large number of teeth are formed on the outer circumference of a rotor. A stator is disposed around the rotor. The stator has multiple magnetic poles whose number is n times the number of phases. Each pole has formed on its surface a plurality of teeth at a pitch equal to the rotor tooth pitch. The teeth mounted on the adjacent magnetic poles are selected to deviate in pitch one-half or thereabout from the rotor teeth and the adjacent poles are to be opposite phases from each other.

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Hitachi, Japan

Ichiro Hashimoto