Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1999-08-05
2001-04-17
Enad, Elvin (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S323020, C310S323160
Reexamination Certificate
active
06218769
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to ultrasonic motors used in a timepiece, a camera, a printer, a storage apparatus and so on, and more particularly to an ultrasonic motor with a magnified drive force.
2. Description of the Related Art
In recent times, in the field of micromechanics attention is attracted to a ultrasonic motor utilizing as power, an elliptical motion as synthesized vibration of elongation and contraction vibration and bending vibration produced in a piezoelectric element applied with a drive signal of alternating current voltage or the like.
Here, an explanation will be given of an ultrasonic motor
4
and an ultrasonic motor
5
as conventional ultrasonic motors in reference to
FIGS. 13
a
and
13
b.
As shown by
FIG. 13
a,
the ultrasonic motor
4
is provided with the structure installed with a projection
41
for taking out an output for moving a moving body (illustration is omitted) by being brought into press contact with the moving body at one end face of a piezoelectric element
40
in a shape of a rectangular parallelepiped.
In this case, the piezoelectric element
40
is provided with four of a polarized region
40
a,
a polarized region
40
b,
a polarized region
40
c
and a polarized region
40
d
which are polarized in the same polarities in the thickness direction and arranged in two rows each comprising two pieces thereof. Further, the polarized regions
40
a,
40
b,
40
c
and
40
d
are respectively provided with electrodes. Further, the electrode on the polarized region
40
a
and the electrode on the polarized region
40
d
which are diagonally opposedly positioned, are shortcircuited by using a lead wire. Similarly, the electrode on the polarized region
40
b
and the electrode on the polarized region
40
c
are shortcircuited by using a lead wire.
The ultrasonic motor
4
moves the moving body in a positive direction by inputting drive signals to the polarized regions
40
a
and
40
d
and moves the moving body in a reverse direction by inputting drive signals to the polarized regions
40
b
and
40
c.
The ultrasonic motor
5
is provided with a piezoelectric element
50
shown by
FIG. 13
b
as a power source. The piezoelectric element
50
is provided with four of a polarized region
50
a,
a polarized region
50
b,
a polarized region
50
c
and a polarized region
50
d
which are polarized in the same polarities in the thickness direction and arranged in two rows each constituting two pieces thereof similar to the piezoelectric element
40
. The polarized regions
50
a,
50
b,
50
c
and
50
d
are respectively provided with electrodes insulated from each other.
The ultrasonic motor
5
moves a moving body, not illustrated, in the positive direction by inputting drive signals X having the same phase to the polarized regions
50
a
and
50
d
and inputting drive signals having a phase advanced from that of the drive signal X by 90 degree to the polarized regions
50
b
and
50
c.
Further, the ultrasonic motor
5
moves the moving body, not illustrated, in the reverse direction by inputting drive signals having a phase retarded from that of the drive signal X by 90 degree to the polarized regions
50
b
and
50
c.
However, the ultrasonic motor
4
utilizes only a half of the polarized regions of the piezoelectric element
40
as the power source and therefore, large output is not provided.
Further, although the ultrasonic motor
5
utilizes all of the polarized regions of the piezoelectric element
50
as a power source, there is needed a circuit for shifting the phase of the input signal by 90 degree. Particularly, when there is carried out self-excited oscillation for driving the ultrasonic motor by utilizing the self-excited oscillation, two input signals having different phases are used and therefore, the constitution of a self-excited oscillation drive circuit becomes complicated and is difficult to realize.
Further, the ultrasonic motor
4
utilizes the piezoelectric element
40
and the ultrasonic motor
5
utilizes the piezoelectric element
50
as both a source of elongation and contraction vibration and a source of bending vibration and accordingly, large elongation and contraction vibration or bending vibration cannot be provided. That is, sufficient output cannot be provided by the conventional ultrasonic motors
4
and
5
. Therefore, in order to provide large output by using the ultrasonic motor
4
or
5
, as shown by
FIG. 14
, for example, a plurality of the ultrasonic motors
4
must be arranged in parallel by using an exclusive jig, which hampers downsizing thereof. Also in this case, vibration escapes from the exclusive jig and, therefore, the output of the ultrasonic motor is reduced.
Further, the elongation and contraction vibration and the bending vibration cannot be controlled independently from each other and accordingly, a moving speed and a drive force of the moving body cannot be controlled widely.
SUMMARY OF THE INVENTION
Hence, it is an object of the present invention to provide an ultrasonic motor in which all of polarized regions of piezoelectric elements are simultaneously utilized and are driven by only input signals having the same phase or an inverted phase and both of large elongation and contraction vibration and bending vibration can separately be controlled and which is provided with large output at low voltage and can be downsized.
In order to resolve the above-described problem, according to an aspect of the invention, there is provided an ultrasonic motor comprising first piezoelectric oscillators totally having a plurality of polarized regions alternately arranged with first polarized regions polarized in same polarities and second polarized regions polarized reversely to the first polarized regions and producing a bending vibration by inputting drive signals having a same phase to the first polarized regions and the second polarized regions to thereby excite the first polarized regions. Second the polarized regions and second piezoelectric oscillators laminated integrally to the first piezoelectric oscillators and produce an elongation and contraction vibration by exciting polarized regions polarized in same polarities. A drive force is provided by an elliptic vibration synthesized with the bending vibration produced in the first piezoelectric oscillators and the elongation and contraction vibration produced in the second piezoelectric oscillators.
In this case, for example, barium titanate, lead titanate, lithium niobate, lithium tantalate or the like is used for the piezoelectric oscillator. Further, as the signal having the same phase, for example, a sine wave is used.
According to the invention, the first piezoelectric oscillators are totally and alternately provided with the first polarized regions polarized in the same polarities and the second polarized regions polarized reverse to the first polarized regions and the drive signals having the same phase are inputted to the plurality of polarized regions and accordingly, large bending vibration is produced. Further, the second piezoelectric oscillators constituting the elongation and contraction vibration source which are installed separately from the first piezoelectric oscillators, produce large elongation and contraction vibration. Further, the first piezoelectric oscillators and the second piezoelectric oscillators are integrally formed and accordingly, the bending vibration and the elongation and contraction vibration are synthesized without leakage. Accordingly, the ultrasonic motor having large output can be fabricated.
Therefore, in the case of providing an output the same as that of the conventional motor, the ultrasonic motor can be downsized.
Further, by separately controlling the first piezoelectric oscillators and the second piezoelectric oscillators, the elongation and contraction vibration and the bending vibration can separately be controlled.
Further, according to another aspect of the invention, there is provided the ultrasonic motor wherein the plurality of polar
Iino Akihiro
Kasuga Masao
Watanabe Satoshi
Adams & Wilks
Enad Elvin
Medley Peter
Seiko Instruments Inc.
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