Nidec Servo Corporation

Yoji Unoki

Shigeaki Terashita

Masafumi Sakamoto

Toru Kobayashi

A rotary electric machine includes a stator in which windings are arranged around a plurality of main poles of a stator core, and a hybrid type rotor arranged with an air gap between the stator and the rotor has a step angle for the rotor of about 4.09&#xb0; and uses metal bearings for supporting a rotor shaft of the rotor. Setting of the step angle for the rotor to be about 4.09&#xb0; can make a rotation angle of the rotor caused by excitation of the windings by an input pulse signal larger as compared with a typical motor having a step angle of about 1.8&#xb0;. With this unique arrangement, the rotor can be rotated at higher speeds, increasing the motor efficiency. Therefore, the motor output at approximately the same level as that of a conventional motor can be obtained without keeping the air gap high precision. Due to this, even if inexpensive slide bearings, i.e., metal bearings to support the rotor, are used, the performance equal to or higher than that of the conventional motor can be ensured, resulting in a large cost reduction.

Rotary electric machine

Brushless motor

A permanent-magnet rotary electric machine preferably includes a stator and a rotor opposed thereto via an air gap. The stator includes a stator core having 4m (m is an integer equal to or larger than 2) main poles each having inductor teeth at a tip thereof. The rotor includes two rotor units adjacent to each other in the axial direction. Each rotor unit includes a pair of rotor magnetic poles and a permanent magnet arranged therebetween. The permanent magnets in the rotor are axially magnetized in opposite directions to each other. Each rotor magnetic pole has magnetic teeth on its outer periphery at a regular pitch. The rotor magnetic poles in each rotor unit are arranged such that the magnetic teeth of one rotor magnetic plate are offset by half a pitch from those of the other rotor magnetic pole, and the magnetic teeth of adjacent rotor magnetic poles are aligned with each other in the axial direction. The tooth pitch of the inductor teeth of each stator main pole is different from that of the magnetic teeth of the rotor magnetic pole to generate a fourth harmonic component of a permeance between the stator and the rotor zero.

Permanent-magnet rotary electric machine

A hybrid type stepper motor preferably includes a two-phase eight-main-pole stator and a rotor defined by two rotor units each having a pair of rotor magnetic poles with a permanent magnet interposed therebetween. Each rotor magnetic pole has fine teeth at a regular pitch. The permanent magnets are magnetized in opposite directions to each other. The adjacent rotor magnetic poles of the rotor units are arranged with their fine teeth aligned with each other in the axial direction. Each main pole has six inductor teeth including: a pair of innermost inductor teeth arranged at the first pitch in the central portion of the main pole; a pair of intermediate teeth on the outside of the innermost inductor teeth at the second pitch therefrom; and a pair of outermost inductor teeth on the outside of the intermediate inductor teeth at the third pitch therefrom. The first, second, and third pitches are all different from the pitch of the fine teeth of the rotor magnetic pole. At least one of the first, second, and third pitches is different from the others.

Growing community of inventors

Gumma, Japan

Yoji Unoki