Actuator, piezoelectric actuator, electronic device, and method for attenuating vibration and converting vibration direction
A viscoelastic body is interposed between a vibrating membrane vibrating in association with a piezoelectric vibrator composed of a piezoelectric element and a base and a support member supporting the vibrating membrane. The viscoelastic body attenuates vibration transmitted from the support member to the vibrating membrane and converts vibration of the vibrating membrane in the surface direction parallel to its main surfaces to vibration of the vibrating membrane in the direction nearly perpendicular to the surface direction. The vibrating membrane is annular with an opening at the center, and the base is joined to the vibrating membrane coaxially with opening.
1. A piezoelectric actuator, comprising:
a piezoelectric vibrator composed of a piezoelectric element and a base vibrated by the piezoelectric element;
a vibrating membrane joined to the outer peripheral part of a main surface of the base and vibrating in association with vibration of the piezoelectric vibrator;
a support member supporting the vibrating membrane; and
a first vibration direction converter interposed between the vibrating membrane and support member and deforming to convert vibration of the vibrating membrane in the surface direction parallel to its main surfaces to vibration of the vibrating membrane in the direction nearly perpendicular to the surface direction,
a second vibration direction converter that is different in rigidity from the first vibration direction converter,
wherein one surface of the first vibration direction converter is joined to the supporting member, and another surface opposing to the one surface is joined to the main surface of the vibrating membrane, and
wherein the vibrating membrane is clamped by the first vibration direction converter and the second vibration direction converter.
2. The piezoelectric actuator according to claim 1 , wherein:
the piezoelectric element is composed of a planar piezoelectric body and a pair of conductors formed on either side of the piezoelectric body, and vibrates upon input of alternating-current signals to the pair of conductors.
3. The piezoelectric actuator according to claim 1 , wherein:
the piezoelectric element and base are circular in a plane view, the piezoelectric element is smaller in area than a region defined by the circumference of the base, and the piezoelectric element and base are coaxially stacked.
4. The piezoelectric actuator according to claim 1 , wherein:
the vibrating membrane is annular with an opening at the center; and
the outer peripheral part of a main surface of the base is joined coaxially with the peripheral edge region of the opening of the vibrating membrane.
5. The piezoelectric actuator according to claim 1 , wherein:
the vibrating membrane and base are integral-molded using an insert molding method.
6. The piezoelectric actuator according to claim 1 , wherein:
the vibrating membrane has rigidity higher than the first vibration direction converter and lower than the base.
7. The piezoelectric actuator according to claim 1 , wherein:
one of the first and second vibration direction converters is secured to the support member.
8. The piezoelectric actuator according to claim 1 , wherein:
the first vibration direction converter is made of a composite material from two or more materials that are different in rigidity.
9. The piezoelectric actuator according to claim 1 , wherein:
the first vibration direction converter is made of a viscoelastic body.
10. The piezoelectric actuator according to claim 1 , wherein:
the first vibration direction converter is made of silicon rubber.
11. The piezoelectric actuator according to claim 1 , wherein:
the first vibration direction converter has an O-shaped cross-section.
12. The piezoelectric actuator according to claim 1 , wherein:
the first vibration direction converter is joined to a main surface of the vibrating membrane or to the outer circumference surface of the vibrating membrane.
13. An actuator, comprising:
a vibration generator generating vibration upon input of drive signals;
a vibrating membrane joined to the vibration generator and vibrating in association with vibration of the vibration generator;
a support member supporting the vibrating membrane; and
a first vibration direction converter interposed between the vibrating membrane and support member and deforming to convert vibration of the vibrating membrane in the surface direction parallel to its main surfaces to vibration of the vibrating membrane in the direction nearly perpendicular to the surface direction,
a second vibration direction converter that is different in rigidity from the first direction converter,
wherein one surface of the first vibration direction converter is joined to the supporting member, and another surface opposing to the one surface is joined to the main surface of the vibrating membrane, and
wherein the vibrating membrane is clamped by the first vibration direction converter and the second vibration direction converter.
14. The actuator according to claim 13 , wherein:
the vibration generator is composed of an electrodynamic converter containing a permanent magnet and a coil.
15. An electronic device in which the piezoelectric actuator according to claim 1 or the actuator according to claim 13 is installed as a vibration device.
16. An electronic device in which the piezoelectric actuator according to claim 1 or the actuator according to claim 14 is installed as an acoustic device.
17. A vibration attenuation and vibration direction conversion method, wherein:
a first viscoelastic body is interposed between a vibrating membrane vibrating in association with vibration of a vibration generator and a support member supporting the vibrating membrane,
the vibrating membrane is clamped by the first viscoelastic body and a second viscoelastic body that s different in rigidity from the e first viscoelastic body; and
the first viscoelastic body is deformed by vibration of the vibrating membrane so as to attenuate vibration transmitted from the support member to the vibrating membrane and convert vibration of the vibrating membrane in the surface direction parallel to its main surfaces to vibration of the vibrating membrane in the direction nearly perpendicular to the surface direction,
wherein one surface of the first viscoelastic body is joined to the supporting member, and another surface opposing to the one surface is joined to the main surface of the vibrating membrane.