GB1108309A - Improvements in and relating to magnetic flux detecting devices - Google Patents

Abstract

1,108,309. Electric motors. HITACHI SEISAKUSHO KABUSHIKI KAISHA. 8 April, 1965 [8 April, 1964], No. 14916/65. Heading H2A. [Also in Division G1] A D.C. stepping motor comprises a yoke Y (Fig. 11a) with coil windings Wg 1 , Wg 2 , a permanent magnet rotor Mr, a stationary toroidal core C coaxial with the rotor and carrying a D.C. energized bias winding L3 and coils L1, L2. The coils L1, L2 are located mutually opposite one another and are included, together with capacitors C 1 , C 2 in the feedback circuit of an oscillator comprising a transistor T r-0 , the state of oscillation of which is dependent upon the relative values of L1, L2. In operation the winding L3 is energized by a direct current sufficient to produce a saturating magnetic field in the core C. The rotor magnetic field opposes the bias field in one half of the core and assists it in the other half, so that as the rotor rotates it causes a saturated region to rotate around the core C linking coils L1, L2 sequentially, thereby varying their inductance, and changing the state of oscillation of T r-0 . The emitter current of T r-0 is fed to the base of a switching transistor T r-1 the collector of which is connected to the base of a second switching transistor T r-2 . The stator coils Wg 1 , Wg 2 , in series, are connected between the collectors of T r-1 , T r-2 . When T r-0 is oscillating T r-1 is in the " off " state and T r-2 is " on " so that stator coil Wg 2 is energized and torque. is applied to the rotor Mr. When the rotor has rotated half a revolution, oscillation stops, T r-1 is switched " on " and T r-2 " off ", so that coil Wg 2 is de-energized and coil Wg 1 is energized and thus rotation of the rotor continues. In an alterntive embodiment (Fig. 11b) a toroidal or rectangular core is installed near the peripheral rotational path of the rotor instead of being coaxial therewith.