Abstract: An ultrasonic motor having a stator in which at least a longitudinal vibration is generated and a rotor rotatably mounted on the stator. Slanted slits are formed on the cylindrical surface of the rotor, which convert a part of the longitudinal vibration in the stator into a twisting vibration that gives the rotor a rotational force. The slits are slanted to the rotational direction of the rotor. The rotor is rotated at a higher speed because of the slits. The form of the slits may be selectively varied according to desired characteristics of the ultrasonic motor.

Abstract: A drive circuit is used in a Langevin type ultrasonic bolt-tightening motor in which a motor drive voltage having a given frequency is applied to a piezo-electric element in a stator section, the resulting longitudinal and torsional vibrations being effective to rotate a motor section. The drive circuit has a longitudinal vibration sensor for detecting the longitudinal vibration in the stator section, a torsional vibration sensor for detecting vibration in the stator section and a frequency controller for controlling the frequency of the motor drive voltage such that the phase difference between the detection signals of the longitudinal and torsional vibration sensors becomes 90 degrees so as to provide maximum efficiency. Thus, the frequency of the motor drive voltage can be feedback controlled to maintain an optimum drive frequency despite the varying of the optimum drive frequency due to changes in various factors.

Abstract: A driving circuit for an ultrasonic motor is disclosed which utilizes a single transformer. A phase shifter frequency-divides the signal from an oscillator by N and generates a plurality of frequency divide signals having different phases. These divided signals are then used to control the driving of the piezoelectric element used to power the ultrasonic motor.