Aisin Seiki Kabushiki Kaisha

Takao Saeki

Yasuo Kuwabara

Naofumi Fujie

Shoji Okada

Mutsuro Aoyama

An ultrasonic motor is provided in which a detector will detect the amplitude of a traveling wave generated on the stator. An oscillator approximates frequency of the travelling wave with respect to the resonance frequency of the stator while the amplitude of the traveling wave is decreased. If the oscillator approaches the frequency of the traveling wave to the resonance frequency of the stator, the amplitude of the traveling wave can be maintained against increasing pressure of the increased torque load of the ultrasonic motor.

Ultrasonic motor

A vibratory motor includes a rotor member having a portion of increased stiffness. A spring member presses the portion of increased stiffness of the rotor member in order to maintain a stable contact between the rotor member and the stator member. The stiffness portion distributes the pressure from the spring member uniformly along a circumference of the rotor member.

Vibratory motor

A vibratory motor is provided with a detecting member for detecting rotational speed of a rotor member and a control circuit for stopping oscillation of a stator member of the motor when the rotational speed of the rotor member becomes less than a predetermined speed. When the rotational speed of the rotor member is less than the predetermined speed, the control circuit stops oscillation of the stator member. When the stator member stops oscillating, slippage is not generated between the rotor member and the stator member and deterioration of the motor due to friction is successfully decreased.

An ultrasonic motor is provided with a moving member and a vibrating member which is in contact with the moving member so as to provide the drive input for the moving member. A piezoelectric vibrator is attached to one side of the vibrating member and the opposite side of the vibrating member has a plurality of circumferentially arranged projections. A top section of each projection contacts the moving member. The piezoelectric vibrator will generate a travelling wave on the vibrating member when a proper alternating current electrical power source is applied to the vibrating member. The vibrating member would then be oscillated in a tangential direction, a normal direction, and a radial direction. The oscillations along the tangential direction and the normal direction generate the travelling wave and only the oscillation along the tangential direction is related to the rotational speed of the moving member. The moving member will then rotate faster and provide a greater amount of output energy if the amplitude of the oscillation along the tangential direction is increased. A ratio is established between the width of the contact portion and the width of the vibrating member. When the ratio of the widths is established in a predetermined range, the efficiency of the ultrasonic motor is improved.

An ultrasonic motor comprises a stator, a rotor, a disc spring for generating a pressure between the stator and the rotor, and a stabilizer disc having a ring-shaped projection for distributing the pressure uniformly to the rotor along the circumference of the ring-shaped projection. Because of such uniform pressure distribution, greater output can be obtained.

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Farmington Hills, MI, United States of America

Takao Saeki