| 摘要 |
PURPOSE:To obtain a high efficiency and a high torque by driving the title motor so that a longitudinal resonance frequency coincides perfectly with the torsional resonance frequency upon high field driving. CONSTITUTION:The stator of an ultrasonic motor is constituted of a composite longitudinal and torsional oscillator, in which respective members arranged in the sequence of a head mass 12a, a longitudinal oscillation driving piezoelectric element 10, first and second ring members, a torsional oscillation driving piezo-electric element 11 and a rear mass 13 are clamped by a nut 14 and a bolt 15. The first ring member on the side of the longitudinal oscillation driving piezo-electric element 10 is designated so that the product of the density thereof by the speed of sound is higher than 27.28kg/ m<2>.sec and lower than 50.66kg/m<2>.sec while the second ring member on the side of the torsional oscillation driving piezo-electric element 11 is designated so that the product of the density thereof by the speed of sound is higher than 18.71kg/m<2>.sec and lower than 34.75kg/m<2>.sec. The rear mass 13 is designed so that the product of the density thereof and the speed of sound is higher than 18.71kg/m<2>.sec and lower than 34.75kg/m<2>.sec. The node of the longitudinal and torsional oscillation can be positioned at the center of the longitudinal oscillation driving piezo-electric element whereby the resonance frequency of respective members can be designed so as to coincide. |
