JPS6475989A - Timepiece using ultrasonic motor - Google Patents

Abstract

PURPOSE:To obtain a timepiece whose thickness is small with an excellent fashion property, by a method wherein an ultrasonic motor rotating a time indicating hand is controlled by an output signal of a time counting element, so that the indicating hand be advanced to a prescribed position. CONSTITUTION:A drive power source 22 of an ultrasonic motor 12 is a source of a two-phase AC voltage of motor drive frequencies, and it outputs voltages V1 and V2 of two phases which are sine, rectangular or triangular waves and different in a phase of 90 deg. from each other. Either one of these voltages V1 and V2 is connected directly to a terminal of the motor 12 to excite two poles out of four, and the other is distributed to fifty-nine contacts of sixty in a group on a watch face through a distributor 23, the remaining one being earthed. This earthed contact shifts along a string of the sixty contacts clockwise in a sequential manner in synchronism with a clock pulse of 'minute' of a digital watch 21. When the time of the watch 21 shifts from 59min to 0, the earthed contact shifts on the watch face in synchronism with the hour hand of the watch 21. When the central hole of a minute hand plate is set on the outer periphery of the motor 12, the minute hand plate stops at a position indicating the present time. Thereafter the minute hand shifts in synchronism with the clock pulse.