Rotary Power Unit

1. Field of the Invention

The present invention relates to an apparatus for translating a reciprocal motion to a rotary motion, and more particularly to an electro-mechanical transducing rotary power unit for generating a rotary motion by vibration of two or more vibration members having a phase difference therebetween.

2. Related Background Art

A vibration motor has been widely used as a rotary power unit. Because it performs electro-mechanical transducing, it produces an electromagnetic noise. Moreover, the manufacture of a coil in such motors is troublesome.

It is an object of the present invention to provide an electro-mechanical transducing rotary power unit which comprises a first vibration member, a second vibration member having a different phase than that of the first vibration member, a ring member rotatably supported by the first vibration member and the second vibration member and adapted to be eccentrically rotated by the vibrations of the first vibration member and the second vibration member, and an output member having a larger outer diameter than an inner diameter of the ring member and adapted to be rotated in partial and internal contact with the ring member by the eccentric rotation of the ring member. Thus, rotary power is efficiently produced with a simple construction without electro-magnetic transducing.

It is another object of the present invention to provide a rotary power unit which comprises first vibration means for vibrating at a predetermined vibration frequency, second vibration means for vibrating at the predetermined vibration frequency with a different phase than that of the first vibration means, ring-shaped drive means supported by the first and second vibration means and adapted to be eccentrically rotated by the vibrations of the first vibration means and the second vibration means, and output means in internal contact with the ring-shaped drive means and adapted to be rotated by the eccentric rotation of the drive means.

FIG. 1 shows an embodiment of a rotary power unit of the present invention.

FIG. 1 shows a construction of a rotary power unit of the present invention applied to a single-lens reflex type camera. Numerals 1 and 2 denote Bimorphes which are vibration members of piezoelectric elements. One end 1a or 2a of each Bimorph is fixed. A drive ring 3 which is a ring member is rotatably pivoted to the other end of the Bimorph 1, a pivot plate 4 is rotatably pivoted to the other end of the Bimorph 2, and the drive ring 3 is rotatably pivoted to the other end of the pivot plate 4. Numeral 5 denotes a rotary disk which is an output member having a center thereof rotatably supported by a base plate (not shown).

In the above arrangement, an A.C., signal of a predetermined frequency is generated by a drive circuit 7 as shown in USP 4,510,411 and applied to the Bimorph 1, which is repeatedly flexed in proportion to the applied voltage. As a result, the bimolf 1 generates a vibration in a direction of an arrow. In the present embodiment, the pivot point of the Bimorph 1 and the drive ring 3, and the pivot point of the Bimorph 2 and the pivot plate 4 form an angle of 90.degree. with respect to the center of the rotary disk 5. An A.C. voltage having the same frequency as that applied to the Bimorph 1 and a phase having a phase difference of 90.degree. from that applied to the Bimorph 1 is applied to the Bimorph 2 by the drive circuit 7. An inner diameter of the drive ring 3 is slightly larger than an outer diameter d of the rotary disk 5. The applied voltages are selected such that the Bimorph 1 and 2 vibrate at an amplitude .delta., where .delta. is a difference between the outer diameter of the rotary disk 5 and the inner diameter of the drive ring 3. Thus, the drive ring 3 makes an eccentric motion while it always partially contacts to the rotary disk 5. That is, the contact point of the drive ring 3 with the rotary disk 5 rotates. As the drive ring 3 makes one revolution of eccentric motion in one period of the A.C. voltage applied to the Bimorph, the rotary disk 5 is rotated by an angle corresponding to the difference between the inner diameter of the drive ring 3 and the outer diameter of the rotary disk 5. Since the outer diameter of the rotary disk 5 is equal to d, it is rotated by an angle of (.delta./d).times.360.degree.. If the phase of the A.C. voltage applied to the Bimorph 2 is in advance of 90.degree. to the phase of the A.C. voltage applied to the Bimorph 1, the drive ring 3 makes a clockwise circular motion and the rotary disk 5 rotates counterclockwise. If the phase of the A.C. voltage applied to the Bimorph 2 is in retard of 90.degree. to the phase of the A.C. voltage applied to the Bimorph 1, the drive ring 3 and the rotary disk 5 rotate in the opposite directions, respectively.

In this manner, the electrical energies imparted to the Bimorph 1 and 2 are converted to mechanical energies and a rotary power is generated by the rotary disk 5.

In the present embodiment, Bimorphes are used as the piezoelectric elements, although other piezoelectric elements such as laminated piezoelectric elements comprising a stack of elements whose thicknesses change upon application of voltages may be used. In this case, however, the force generated is larger but the displacement is smaller than those obtained by the Bimorphes and the use of a displacement magnification mechanism by a lever is preferable.

In the present embodiment, two piezoelectric elements are used for the purpose of simplicity, although three or more elements may be used. In this case, the arrangement of the action points of the piezoelectric elements to the drive ring is correlated to the phases of the A.C. voltages. As the number of piezoelectric elements increases, the output torque will increase accordingly.

In accordance with the present invention, there is provided an electro-mechanical transducing apparatus, which comprises a first vibration member, a second vibration member having a different phase than that of the first vibration member, a ring member rotatably supported by the first vibration member and the second vibration member and adapted to be eccentrically rotated by the vibration of the second vibration member, and an output member having a smaller outer diameter than an inner diameter of the ring member and adapted to make a rotary motion in partial and internal contact with the ring member by the eccentric rotation of the ring member. Thus, the electrically generated vibrations are transduced to the continuous rotary motion with simple construction and high efficiency.