Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-06-01
2002-08-06
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
Reexamination Certificate
active
06429572
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an actuation device comprising at least one piezoelectric motor and a part able to move under the action of the said piezoelectric motor.
2. Description of the Related Art
The document EP-A-0 633 616 describes such a device in which the motor comprises a piezoelectric element which has several electrodes on its surface.
On one side of this piezoelectric element there is disposed a movement transmission part in contact with the movable part, and on the other side a spring.
By supplying the piezoelectric element suitably with power, the combination of the flexion of the piezoelectric element and the return force of the spring causes an elliptical rotation of the piezoelectric element, whose driving force is transmitted by friction to the movable part by means of the transmission part.
The problem with this type of motor is its complexity of use, notably with regard to the adjustment between the electrical power supply and the mechanical force applied by the spring.
This is because the formation of the elliptical rotation of the transmission part depends on this combination. The said part having to come into contact with the movable part only over the part of the cycle corresponding to the required direction of movement.
In addition, the transmission of the driving force by friction between the transmission part and the movable part causes a significant loss of energy.
This device also has a relatively large size having regard to its application, notably for electrical relays.
SUMMARY OF THE INVENTION
The invention therefore aims to remedy these drawbacks by providing an actuation device by means of a movable part moved by a piezoelectric motor which is of smaller size and simpler in its use than that of the prior art. In particular, the invention aims to provide such an actuation device whose functioning does not require the use of an external mechanical force, such as the one supplied by a spring, to cause the movement of the movable part.
To this end, the invention provides for an actuation device comprising at least one piezoelectric motor and a movable part, in which the said piezoelectric motor is formed by at least one piezoelectric element associated with means of supplying electric current for causing oscillatory deformations of the said piezoelectric element, and in which the movable part comprises at least one micro-rack intended to allow the transmission to the movable part of the driving force generated by the oscillatory deformations of the piezoelectric element.
The micro-rack has a surface on which, in part of the deformation cycle, the piezoelectric element exerts a force allowing the movement of the movable part and a second surface along which, over a second part of the deformation cycle, the piezoelectric element exerts substantially no force on the movable part.
For example, the micro-rack is formed by a succession of dihedrons, the height of which is of the same order of magnitude as the magnitude of the oscillatory deformations of the piezoelectric element.
A rod transmitting the deformations is associated with the piezoelectric element in order to be engaged and disengaged in the micro-rack when the piezoelectric element deforms in an oscillatory fashion.
In a first embodiment of the piezoelectric element, it deforms essentially by elongation.
A spring can then be associated with the transmission rod in order to facilitate the passage of the transmission rod from one dihedron to the adjacent dihedron during the movement of the movable part.
In a second embodiment of the piezoelectric element, it deforms essentially by elongation and flexion.
In a first embodiment, the device comprises a micro-rack and a piezoelectric motor, a return spring being associated with the movable element.
In a second embodiment, the device comprises two micro-racks and two piezoelectric motors.
In a variant of these two embodiments, the device also comprises means of locking the movable part in position.
REFERENCES:
patent: 5049775 (1991-09-01), Smits
patent: 5682076 (1997-10-01), Zumeris
patent: 5777423 (1998-07-01), Zumeris
patent: 6064140 (2000-05-01), Zumeris
patent: 0633616 (1994-05-01), None
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patent: 04 140074 (1992-05-01), None
patent: 04161077 (1992-06-01), None
patent: 40161077 (1992-06-01), None
Addison Karen
Nguyen Tran
Norbert Beyrard France
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