Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-10-31
2002-06-11
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S323020, C310S316010
Reexamination Certificate
active
06404103
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ultrasonic motor and an electronic apparatus using the ultrasonic motor, particularly to an ultrasonic motor increasing an output per unit volume and an electronic apparatus using the ultrasonic motor.
2. Description of the Related Art
In recent times, in the field of micromechanics, attention has been directed to realizing an ultrasonic motor utilizing flexing oscillation generated in a piezoelectric member applied with drive voltage such as an alternating current voltage as a power source thereof.
As an example of a conventional ultrasonic motor, there is provided, for example, an ultrasonic motor
100
of a circular plate type shown in FIG.
20
through FIG.
23
B.
As shown by an outline sectional view of
FIG. 20
, the ultrasonic motor
100
is generally constituted by a piezoelectric element
101
in a circular plate shape, an oscillator
102
made of a metal as an elastic member adhered onto the piezoelectric element
101
, a plurality of projections
103
erected integrally at an upper face of the oscillator
102
as the elastic member, enlarging displacement of oscillation of the piezoelectric element
101
and taking out an output thereof, a rotor
104
which is brought into contact with the projections
103
from above and rotating by way of frictional force by movement of the projections
103
, a support shaft
105
penetrating centers of the piezoelectric element
101
and the oscillator
102
, holding the piezoelectric element
101
and the oscillator
102
above a base plate
110
and playing a role of guiding rotation of the rotor
104
and a spring
106
for depressing a rotational center of the rotor
104
downwardly to thereby ensure predetermined contact pressure between the rotor
104
and the projections
103
. In this case, the piezoelectric element
101
is applied with drive voltage via lead wires
107
a
and
107
b
crawling on the base plate
110
.
According to the piezoelectric element
101
, as shown by an outline upper view of
FIG. 21
, PZT which is a well-known piezoelectric material, is molded in a circular plate shape and is provided with a hole
101
c
for passing the rotating shaft
105
at its center and which is divided into six divisions in a circumferential direction and the divisions are polarized such that polarizing directions thereof are reverse to each other and each of the divisions is equally divided into two. As a result, there is constructed a constitution in which there are arranged a total of
12
pieces of polarized portions
101
a
polarized in positive polarity and polarized portions
101
b
polarized in polarity reverse thereto alternately at every two pieces thereof. Signs of plus (+) and minus (−) in the drawing represent polarities of polarization and in this case, polarizing treatment is carried out in the thickness direction of the piezoelectric element
101
, plus (+) indicates that the polarizing treatment is carried out in a direction from the piezoelectric element
101
toward the oscillator
102
and minus (−) indicates that the polarizing treatment is carried out conversely in a direction from the oscillator
102
toward the piezoelectric element
101
.
Here, as shown by schematic views of FIG.
21
and
FIG. 22
, the projections
103
are provided at every other boundaries of the polarized portions.
Further, the piezoelectric element
101
is provided with an electrode
108
a
connected to the lead wire
107
a
and an electrode
108
b
connected to the lead wire
107
b
as electrodes for inputting drive voltage. The electrode
108
a
covers every other polarized portions, mentioned above, further, the electrode
108
b
covers every other polarized portions reversely to the electrodes
108
a.
That is, when drive voltage is inputted to the electrode
108
a
, as shown by
FIG. 23A
, the piezoelectric element
101
is generated with a standing wave such that central portions of the respective polarized portions covered by the electrode
108
a
constitute antinodes. The projections
103
are disposed at every other intermediaries of the antinodes and nodes of the standing wave. Therefore, head portions of all of the projections
103
draw a locus in a circular arc shape and accordingly, in this case, as shown by an arrow mark in
FIG. 23A
, the rotor
104
is rotated in one direction. At this occasion, the projections
103
play a role of amplifying oscillation of the standing wave.
Further, when drive voltage is inputted to the electrode
108
b
, as shown by
FIG. 23B
, the piezoelectric element
101
is generated with a standing wave such that central portions of the respective polarized portions covered by the electrode
108
b
constitute antinodes and accordingly, the head portions of all of the projections
103
draw a locus in a circular arc shape in a reverse direction. Therefore, in this case, as shown by an arrow mark in
FIG. 23B
, the rotor
104
is rotated in a reverse direction.
However, according to the above-described ultrasonic motor
100
, in order to switch the rotational direction, the ultrasonic motor is driven by selecting an electrode for applying the drive voltage from the electrode
108
a
or the electrode
108
b
. Therefore, not all of the polarized portions provided in the piezoelectric element
101
but a half thereof are driven.
That is, all of the piezoelectric elements
101
are not utilized simultaneously and accordingly, an output of the ultrasonic motor
100
is small in consideration of the size.
In view of the above-described situation, it is an object of the present invention to provide an ultrasonic motor increasing an output per unit volume by driving the ultrasonic motor by using all of polarized portions provided to a piezoelectric element and enabling regular and reverse rotation thereof, and an electronic apparatus having an ultrasonic motor utilizing the ultrasonic motor.
SUMMARY OF THE INVENTION
In order to resolve the above-described problem, according to the invention, there is provided an ultrasonic motor characterized in that in an ultrasonic motor comprising a piezoelectric element for generating an oscillation wave and a moving member driven by the oscillation wave generated by the piezoelectric element, the ultrasonic motor including the piezoelectric element in a circular disk shape having polarized portions divided by a multiple of four in a circumferential direction, projections provided at upper portions of and spaced apart by odd numbers of the polarized portions of the piezoelectric element for taking out motor drive force from standing wave oscillation generated by the piezoelectric element, and a moving member driven by the projections brought into contact with upper ends of the projections, polarities of each two adjacent polarized portions are the same and polarities of adjacent pairs are reverse to each other, a first polarized portion group constituted by every other polarized portion and a second polarized portion group constituted by the polarized portions not belonging to the first polarized portion group, selecting whether phases of alternating voltage inputted to the first polarized portion group and the second polarized portion group are made to be the same phase or to constitute a phase difference of 180 degrees, a relative positional relationship between a standing wave oscillation generated in the piezoelectric element and the projections is changed to thereby switch a direction of driving the ultrasonic motor.
In this case, when positive voltage is applied to the polarized portion, the polarized portion subjected to the polarizing treatment in positive polarity is elongated and the polarized portion subjected to the polarizing treatment in negative polarity is contracted. Further, when negative voltage is applied, the elongation and contraction relationship is reversed. That is, according to the ultrasonic motor of the invention, motor drive is carried out by standing wave oscillation generated at the piezoelectric element by inputti
Iino Akihiro
Kasuga Masao
Kosaka Takayuki
Suzuki Kenji
Adams & Wilks
Dougherty Thomas M.
Seiko Instruments Inc.
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