A lens barrel includes: an electromechanical conversion element; an elastic body having a joining surface, a drive surface, and grooves; a motion member rotating by vibration wave of the drive surface; a rotating ring having a recess part and rotating by rotation of the motion member; a moving ring engaged to the recess part and moving to an optical axis direction by rotation of the rotating ring; and a lens held in the moving ring; wherein the element is made of a material having sodium potassium niobate, potassium niobate, sodium niobate or barium titanate, wherein a value of T/(B+C) is within a range of from 1.3 to 2.8 when: length from the drive surface to a base unit of the groove is defined as T; length from the base unit of the groove to the joining surface is defined as B; and thickness of the element is defined as C.

A vibration actuator includes an elastic body on which at least one projection is formed and a vibrating body including an electromechanical conversion device, and drives a driven member that is in contact with a contact portion of the projection by causing an end portion of the projection to perform an ellipsoidal movement in response to a combination of two vibration modes generated in the vibrating body when an alternating driving voltage is applied. The elastic body is formed integrally with the projection and a bonding portion between the projection and the electromechanical conversion device. A space is provided between the contact portion and the electromechanical conversion device to which the projection is bonded. The spring portion is provided between the bonding portion and the contact portion and causes the projection to exhibit a spring characteristic when the contact portion is pressed by the driven member.

A vibration-type driving apparatus that is capable of detecting an undesired vibration in a vibrating body more accurately than conventional detection methods even if a frequency of the undesired vibration falls inside a range of driving frequencies or is an integer multiple of a driving frequency. The driven body which is brought into contact with the vibrating body is driven by generating a driving vibration in the vibrating body through application of driving voltage to the electro-mechanical energy conversion element. An electro-mechanical energy conversion element of the vibrating body has a first sensor phase and a second sensor phase placed at different locations in the vibrating body. A vibration of the vibrating body is detected by using a result of comparison between an output signal from the first sensor phase and an output signal from the second sensor phase.

A vibration-type actuator includes a vibrating body including an annular elastic member and an electric-mechanical energy conversion element, and an annular contact body configured to move relative to the vibrating body. The contact body includes a base portion, a support portion annularly extending from the base portion in a radial direction of the contact body, and a friction member provided at the support portion, formed separately from the support portion, and being in contact with the vibrating body. The friction member includes a first part extending in a direction along a central axis of the annular contact body, and a second part extending in the radial direction, the first part and the second part being connected to the support portion. The first part includes a portion that is connected by being either internally or externally fitted to the support portion in the radial direction.

A vibration wave motor comprises: an electromechanical conversion element; an elastic body which has a drive surface on which a vibration wave is generated due to vibration of the electromechanical conversion element; and a relative motion member which makes contact with the drive surface of the elastic body and is configured to rotationally drive by the vibration wave, the electromechanical conversion element having a density of from 4.2 to 6.0×10.sup.3 kg/m.sup.3, a plurality of grooves being provided on the drive surface side of the elastic body, and a value of T/(B+C) being within a range of from 1.3 to 2.8 when: depth of at least one groove of the plurality of grooves is defined as T; thickness from a base unit of the groove to a first surface is defined as B; and thickness of the electromechanical conversion element is defined as C.

A rotational force transmitting apparatus includes a cylindrical fixed member, a rotating member configured to rotate around the cylindrical fixed member, a first bearing member held by the cylindrical fixed member and configured to rotate around an axis parallel to a rotation axis of the rotating member, and a second bearing member held by the cylindrical fixed member and configured to rotate around a radial direction of the rotating member.

A vibration-type drive apparatus, which increases productivity and also prevents undesired vibration from occurring during operation, includes an elastic body, a vibrating body having an electro-mechanical energy conversion element mounted on the elastic body, a driven body that is brought into pressure contact with the vibrating body, and a pressurizing member that brings the driven body into pressure contact with the vibrating body. Relative positions of the vibrating body and the driven body change due to vibrations excited in the vibrating body. The pressurizing member has a positioning portion, and the driven body has a fitting-receiving portion that is to be fitted onto the positioning portion. During operation, the positioning portion and the fitting-receiving portion are not in contact with each other.

A vibration drive device that suppresses an increase in the number of component parts and can be easily downsized. Vibration is excited in a vibration element in pressure contact with a driven element to thereby rotationally move the driven element relative to the vibration element. A bearing rotatably supports the driven element. A first and a second bearing portions are joined to the driven element. The second and a third bearing portions are pressed against each other via rolling elements in a direction along the axis of the bearing. The rolling elements are brought into pressure contact with the first raceway surface of the first bearing portion, the second raceway surface of the second bearing portion, and the third raceway surface of the third bearing portion. One of the second and third bearing portions is integrally formed with the driven element from the same material.

A vibrator of a vibration-type driving device according to an aspect of the present invention includes a first vibrating member that includes first protrusions protruding in a first direction, a second vibrating member that includes second protrusions protruding in a direction that is opposite to the first direction, and an electric-mechanical energy conversion element that is fixed to the first vibrating member. The first protrusions and the second protrusions each have a hollow structure, and the first vibrating member and the second vibrating member are disposed in such a manner that a surface of the first vibrating member on which the first protrusions are not formed and a surface of the second vibrating member on which the second protrusions are not formed face each other.

A built-in piezoelectric type online dynamic balance actuator which includes two structurally identical left and right piezoelectric drive adjustment mechanisms at two sides of a housing. The piezoelectric drive adjustment mechanism includes a shaft having one end supported inside a housing chamber by bearing, a middle portion connected to an end cover by bearing, and the other end supported on bearing housing by bearing, a weight mass coupled to the shaft and positioned inside a tightening sleeve with one side connected to the bearing housing and another side connected to the end cover and the housing, and a stator fixedly connected to one side of the end cover, a mover pressed against a surface of the stator through a disk. Through a control center, the mass weights of the left and right piezoelectric drive adjustment mechanisms are fixed to a preset angle. As the main shaft rotates at a high speed, the two weight masses generate centrifugal force which combine to a balance vector to cancel the imbalance vector of the main shaft, improve the mass distribution of the main shaft and better fit the online dynamic balance requirements.