Abstract: A spindle motor which is designed to rotate with minimal vibrations and hence is suitable for a hard disk driver. The spindle motor employs hydrodynamic bearings as radial and thrust bearings. A support shaft is formed in a cylindrical configuration with a center hole, and a rotor has a columnar portion which is inserted into the center hole in the support shaft. A thrust bearing collar is attached to the lower end of the rotor, and a thrust bearing member is secured to a base in opposing relation to the thrust bearing collar. A group of stator coils and a radial bearing member are disposed on either the inner peripheral surface of the center hole in the support shaft or the outer peripheral surface of the support shaft, and a group of rotor magnets and a radial bearing sleeve are disposed on either the outer peripheral surface of the columnar portion or the inner peripheral surface of the rotor in opposing relation to the stator coil group and the radial bearing member.

Abstract: A DC electric motor, which is much quieter than previous DC motors, is disclosed. The inventive motor includes a rotor and a stator, and either the rotor or the stator includes tynes bearing windings. Significantly, the tynes are interconnected, which reduces vibration and noise.

Abstract: A ball-splined shaft assembly suitable for use in a robot arm or the like is provided. The assembly includes a shaft formed with a plurality of circumferential grooves spaced apart from one another at a predetermined pitch and a pair of longitudinal grooves which are located opposite sides and extend in parallel with the center line of the shaft. An outer sleeve unit fitted onto the shaft includes a pair of endless circulating paths each provided with a plurality of balls. Each of the endless circulating paths includes a load path section where the balls are partly exposed and thus received in the corresponding one of the longitudinal grooves. The outer sleeve unit is mounted on a housing through a pair of ball bearings. Thus, the shaft may rotate together with the outer sleeve unit relative to the housing and the shaft may move in its longitudinal direction relative to the outer sleeve unit and thus the housing. A stepping motor is mounted on the housing and operatively coupled to the outer sleeve unit.

Abstract: A motor includes a field magnet system comprised of plural permanent magnetic poles arranged in a circle and an armature with plural poles each facing the magnetic poles of the field magnetic system. The widthwise length of a magnetic flux generating area of the permanent magnetic poles varies with the rotational angle to eliminate a cogging torque caused by higher harmonic wave components of the magnetic flux.

Abstract: A stepping motor includes a stator having a plurality of magnetic poles wound with windings of three phases or four phases, and a rotor formed by a pair of rotary plates each having a multiplicity of gear-like salient poles and an axially magnetized permanent magnet sandwiched between the rotary plates. Where the number of magnetic poles of the stator is represented by m, the number of gear-like salient poles of the rotary plate is Z, and n is an integer equal to or larger than 1, in order to obtain a minute step angle, m, n and Z are selected to satisfy the following relationship: when m=9, and a 3-phase winding stator, Z=9n.+-.3.