Abstract: An ultrasonic motor includes a stator having a piezoelectric element and a rotor facing the stator. The piezoelectric element is annular and is polarized into segments in the circumferential direction. A flexible plate is fixed to the piezoelectric element with an electrode plate in between. The flexible plate includes a flexible substrate, a conductor, and a reinforcement. The conductor is located on a part of the flexible substrate to be electrically connected to the electrode plate. The reinforcement is located on the flexible substrate at a position that is off the conductor. The reinforcement suppresses vibration generated at a part of the piezoelectric element that is off the conductor, thereby stabilizing vibration of the piezoelectric element in the circumferential direction.

Abstract: An ultrasonic motor includes a stator having a piezoelectric element and a rotor facing the stator. The piezoelectric element vibrates the stator to rotate the rotor. A lining member is located between the rotor and the stator. A spring is installed in the motor. The spring is deformed by a predetermined amount to press the rotor against the stator. The force of the spring pressing the rotor changes in accordance with the deformation of the spring. The spring is installed such that its deformation is in a predetermined range, so that, within the range, the urging force of the spring changes by a relatively small amount for a given change of deformation. Therefore, when deformation of the spring changes due to wearing of the lining member, the urging force of the disk spring scarcely changes. Accordingly, the rotation characteristics of the motor scarcely change over time.

Abstract: An ultrasonic motor includes a stator having a piezoelectric element and a rotor facing the stator. The piezoelectric element vibrates the stator to rotate the rotor. A lining member is located between the rotor and the stator. A spring is installed in the motor. The spring is deformed by a predetermined amount to press the rotor against the stator. The force of the spring pressing the rotor changes in accordance with the deformation of the spring. The spring is installed such that its deformation is in a predetermined range, so that, within the range, the urging force of the spring changes by a relatively small amount for a given change of deformation. Therefore, when deformation of the spring changes due to wearing of the lining member, the urging force of the disk spring scarcely changes. Accordingly, the rotation characteristics of the motor scarcely change over time.