Actuator

Details Actuator Actuator

1999-11-01

2001-03-13

Budd, Mark O. (Department: 2834)

Electrical generator or motor structure

Non-dynamoelectric

Piezoelectric elements and devices

C310S323020

Reexamination Certificate

active

06201340

ABSTRACT:

This application is based on patent application Hei.10-312419 filed in Japan, the content of which are hereby incorporated by references.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a truss type actuator having a plurality of (for example, two) displacing devices such as piezoelectric devices crossing at right angle, and respectively driven by alternating driving .voltages having a phase difference between them for generating a driving force owing to an elliptical movement of a chip member provided at crossing point of the displacing devices.
2. Description of the Related Art
Conventionally, a truss type piezoelectric actuator is known from Publication Gazette of Unexamined Japanese Patent Application Hei 8-289573 (hereinafter abbreviated as first prior art) or U.S. Pat. No. 4613782 (hereinafter abbreviated as second prior art).
In the first prior art, contacting faces at base ends of two piezoelectric devices (first piezoelectric device and second piezoelectric device) are fixed on a base member, and contacting faces at top ends of the piezoelectric devices are also fixed to a chip member provided at a cross point of the piezoelectric devices. The first prior art, however, does not teach the method for fixing the piezoelectric devices and the base member, and so on. On the other hand, in the second prior art, each piezoelectric device and a driving element are fixed by a resultant motion mechanism having a rigidity in a direction parallel to a displacing direction of the piezoelectric device and a flexibility in a direction perpendicular to the displacing direction of the piezoelectric device.
In the first prior art, when the first piezoelectric device is driven for displacing, a bending force acts on the second piezoelectric device in a transverse direction thereof, and the first piezoelectric device receives a reaction force from the second piezoelectric device. In case of fixing the base member and the chip member on each piezoelectric device by a material having a high rigidity, the displacement of the first piezoelectric device is restricted by the reaction force from the second piezoelectric device, so that the output power of the actuator is reduced. To the contrary, in case of fixing the base member and the chip member on each piezoelectric device by a material having a low rigidity, when the piezoelectric devices are driven by driving voltages having a high frequency, the vibration is absorbed by the adhesive layer, so that the output power of the actuator is reduced.
In the second prior art, a resonance frequency of the piezoelectric device is reduced due to a weight of the resultant motion mechanism, so that the output power of the actuator is reduced. Furthermore, a plurality of resonance vibration modes occur due to the addition of the mechanical members, so that the control of the actuator becomes difficult.
SUMMARY OF THE INVENTION
An object of this invention is to provide an actuator having a plurality of displacing devices which can easily be controlled and can output a high power.
An actuator in accordance with an aspect of the present invention comprises a plurality of displacing devices provided for crossing at a predetermined angle and a driving member provided at a crossing point of the displacing devices. The displacing devices are respectively driven by a plurality of alternating driving signals having a predetermined phase difference between two of them for moving the driving member as a predetermined motion. Each displacing device and the driving member and a base member for holding the displacing device are fixed by a composition of a plurality of kinds of members having different rigidity.
Thus, when one of the displacing device is displaced, it hardly receives reaction force from another displacing device, so that the driving member can be driven for trailing substantially the same trail as a predetermined trail of standard design. As a result, the reduction of the output power of the actuator due to the energy loss becomes very few. Furthermore, the driving member trails substantially the same trail as the ideal trail of standard design, so that the noise and the vibration occurring when the driving member contacts a driven member such as a rotor can be reduced, and the output of the actuator becomes stable.


REFERENCES:
patent: 4613782 (1986-09-01), Mori et al.
patent: 4950135 (1990-08-01), Tojo et al.
patent: 5132582 (1992-07-01), Hayashi et al.
patent: 5917271 (1999-06-01), Yamamura
patent: 8-289573 (1996-11-01), None

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