Electricity: motive power systems – Nonmagnetic motor
Patent
1997-02-18
1999-03-23
Budd, Mark O.
Electricity: motive power systems
Nonmagnetic motor
310316, H01L 4108
Patent
active
058864830
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a supply circuit for a piezo-electric motor, for example, of the free progressive wave type schematically represented in FIG. 1 and comprising a rotor 1, driven by friction by a stator 2 which is energized by a piezo-electric element 3.
According to a well-known implementation shown in FIG. 2, the piezo-electric element 3 comprises two piezo-electric areas 5 and 6 disposed in series and alternately polarized. These two areas 5 and 6 are separated by two spaces, neither of which receive an active piezo-electric area: a first space 8 usually serving as sensor in the vibration control loop, and a second neutral space 10. The non-illustrated rear face of the piezo-electric element is connected to the ground 9. The area 5 is energized by a first electrode 11 supplied by a high frequency voltage V.sub.1 ', and the area 6 is energized by a second electrode 12 supplied by a high frequency voltage V.sub.2 ', said tensions V.sub.1 ' and V.sub.2 ' being phase shifted by substantially 90.degree., and supplied by two alternating supply sources independently created from a DC source. The voltages V.sub.1 ' and V.sub.2 ' applied to each of the electrodes cause vibrations in each of the areas 5 and 6, creating two stationary waves whose resultant leads to a free progressive wave resulting in elliptical movements of material points of the elastic element of the stator put in contact with the rotor, which engenders the rotational movement of the rotor with respect to the stator.
The alternating supply sources are thus created by independent supply devices. Such supply devices utilize either two independent magnetic circuits as is described in patents U.S. Pat. No. 5,130,619 and U.S. Pat. No. 5,021,700, or by several independent switches as is described in patent U.S. Pat. No. 5,179,311. These supply devices thus comprise a great number of elements which considerably increases the cost price of such devices, as well as their size.
SUMMARY OF THE INVENTION
The goal of the invention is to remedy the abovecited disadvantages by implementing a novel supply circuit which is reliable and economical.
According to the invention, the supply circuit of a piezo-electric motor comprises a single high frequency alternating supply source, as well as an adapting means connected, on the one hand, to the alternating supply source and, on the other hand, to two electrodes energizing the piezo-electric element and serving to generate the two voltages V.sub.1 ' and V.sub.2 '.
Thanks to the invention, the supply circuit of the piezo-electric motor is not oversized, and the novel structure of the supply circuit considerably simplifies the supply of the electrodes energizing the piezo-electric element of the motor while minimizing the cost and limiting the number of components.
BRIEF DESCRIPTION OF THE DRAWINGS
The characteristics and advantages of the invention will emerge from the description to follow which should be considered as a non-limiting example, by reference to the attached drawings in which:
FIG. 1 represents a sectional view of a schematic representation of a piezo-electric motor according to the prior art;
FIG. 2 represents the placement of the electrodes energizing the piezo-electric element of the motor of FIG. 1 according to a conventional implementation;
FIG. 3 represents an electrical schematic of a first embodiment of a supply circuit of a piezo-electric motor according to the invention;
FIG. 4 represents a frequency diagram of the supply circuit according to the invention;
FIG. 5 represents an electrical schematic diagram of a particular mode of the supply circuit according to the invention;
FIG. 6 represents a transformer well adapted to the supply circuit of FIG. 3 according to the invention;
FIG. 7 shows the waveforms obtained with the supply circuit depicted in FIG. 3;
FIG. 8 shows another embodiment of the supply circuit similar to that of FIG. 5, and equipped with a device to regulate the rotational speed of the piezo-electric motor;
FIG. 9 shows an embodiment
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Nogarede Bertrand
Piecourt Eric
Budd Mark O.
Moulinex (S.A.)
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