MICRO-MINIATURE STEPPING MOTOR

摘要

A micro-miniature stepping motor suitable for driving the gear works of an electronic watch wherein lowfrequency timing impulses derived from a high-frequency time base are applied to the stator coil of the motor to cause the rotor thereof to index ninety degrees in response to each impulse. The rotor includes a square rotor plate and a stator plate parallel thereto, a shaft secured to the center of the rotor plate extending through a central opening in the stator plate. Mounted on the underside of the rotor plate at the corners thereof are four permanent magnet blocks with their poles in mutual opposition to form a magnetic circuit between the rotor stator plates whose lines of flux bridge the air gap there-between. The stator plate has a generally square formation whereby the magnet blocks on the rotor, in the absence of a torqueproducing force, seek to orient themselves to a stable position of minimum reluctance. In this position, each block is proximate to a respective corner of the stator plate, there being a series of four such stable positions which are ninety degrees apart. The stator coil has a pancake formation and is interposed in the air gap, whereby when an impulse is applied to the coil, the resultant torque displaces the rotor to cause it to index to the next stable position.