Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic driv-
ing device comprising a stator consisting of a cylindrical.
piezoelectric vibrator having divided electrodes.
In a known ultrasonic motor using a piezoelectric
vibrator, two groups of elec-trodes are attached to one end of
a ring type piezoelectric ceramic, the two group of electrodes
are so positioned that standing waves respectively generated
by the two groups of electrodes are lifted every r~/2 in each
position. The parts of the ring type piezoelectric vibrator
corresponding to the electrode are alternately polarized in
reverse. Also, the two groups of the electrodes are respect-
ively connected to two oscillators for respectively generating
alternating current voltages having a ~/2 phase shift from
each other. When the alternating current voltages from the
two oscillators are respectively applied to the two groups of
electrodes, the two standing waves having a ~/2 phase shift
from each other generated on the surfaces of the ring type
piezoelectric vibrator and then progressive waves owing to a
compound of the two standing waves generated on the surfaces
of the ring type piezoelectric vibrator. Therefore, when a
rotary member is put on the ring type piezoelectric vibrator
and the rotary member is strongly pressed to the ring type
piezoelectric vibrator, the rotary member is rotated by the
progressive waves.
In the prior ultrasonic motor, since the ring type
piezoelectric vibrator must be polarized in many portions
thereof and the two oscillators must be connected to the
electrodes, the composition of the ring type piezoelectric
vibrator is complex and the cost of ultrasonic motor becomes
expensive.
SUMMARY OF THE INVENTION:
It is, therefore, the primary object of the present
invention to provide and ultrasonic driving device having a
simple composition.
It is another object of the present invention to
provide an ultrasonic driving device having a stator
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consisting of a cylindrical piezoelectric vibrator provided
with divided electrodes in inside and outside portions there-
of.
It is another object of the present invention to
provide an ultrasonic driving device in which gaps between
divided electrodes in the inside and outside portions are
shifted from ~ach other.
In order to accomplish the above and other objects,
the present invention comprises a stator having a cylindrical
piezoelectric vibrator and divided electrodes in its inside
and outside portions, and a rotary member composed on one end
or a side portion of the stator, alternating current voltage
being respectively applied-to one or more electrodes in the
inside and outside portions of the cylindrical piezoelectric
vibrator.
BRIEF DESCRIPTION OF THE DRAWI~GS:
Fig. 1 shows a sectional view of an ultrasonic motor
in the prior art.
Fig. 2 shows a plane view of a form of a piezo-
electric vibrator and a composition of electrodes of the
piezoelectric vibrator in the ultrasonic motor in Fig. 1.
Fig. 3 shows a perspective view of a stator of an
ultrasonic driving device in an embodiment according ko the
present invention.
Fig. 4 shows a plane view of a stator in Fig. 3.
Fig. 5 shows a view for explaining the principle of
motion of a stator according to the present invention in Fig.
3.
Fig. 6 shows a simple view of an ultrasonic driving
device according to the present invention.
Fig.7 shows a side view of an ultrasonic driving
device in the embodiment according to the present invention.
Fig. 8 shows a section view of an ultrasonic driving
device in another embodiment according to the present inven-
tion.
Fig. 9 shows a side sectional view of a frame of a
camera using an ultrasonic driving device according to the
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present inventi.on.
Fig. 10 shows a sectional view taken about line A-A
in the frame of the camera in Fig. 9.
Fig. 11 shows a perspective view of a stator of an
ultrasonic driving device in another embodiment according to
the present invention.
DESCRIPTION OF THE PREFERRED EMBODI~ENTS:
Referring to the prior art in Fig. 1, a ring type
piezoelectric vibrator B is attached to a ring type resilient
member A and the piezoelectric vibrator B vlbrates with -the
resilient member. The piezoelectric vibrator B is divided in
17 parts by the ration of e.g. 22.5 or 11.25. The respect-
ive neighbouri.ng portions in the 17 parts of the piezo-
electric vibrator B are polarized by a reverse polarity with
respect to each other as shown in Fig. 2. The two portions C
and D in one side of the piezoelectric vibrator B are respect-
ively attached as an electrode by conductive paint as shown in
Fig. 2. The portion G in Fig. 2 shows an earth electrode.
The member F to be driven to which slider E is attached is
mounted on the resilient member A.
In the ultrasonic motor in the prior art, the alter-
nating current voltage of Vosinwt is applied to the one
electrode C and the alternating current voltage Vocoswt is
applied to the other electrode D, where Vo is the instant-
aneous value, w is the radian frequency and t is time. The
phases of these voltages shift by n/2 from each other. There-
by, the divided portions of the piezoelectric vibrator B
alternately expand and contract and thus, the resilient member
A has a bending vibration. Therefore, a standing wave is
generated in the resilient member A and a progressive wave is
generated on the resilient member A. Thus, the driven member
F having the slider E is rotated on the resilient member A.
~ owever, in the prior ultrasonic motor, because the
divided portion of the ring type piezoelec-tric vibrator B must
be alternately polarized and the divided electrodes must be
formed on the divided portion of the piezoelectric vibrator B,
the composition of the prior ultrasonic motor is complet~.
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Re~erring to Figs. 3 and ~, in a stator 4 consisting
of a cylindrical piezoelectric vibrator in the embodiment ac-
cording to the present invention, divided electrodes 2a and 2b
are provided on the outside portion of a piezoelectric vibra-
tor 1 and divided electrodes 3a and 3b are provided on the
inside portion of the piezoelectric vibrator 1. Gaps 2c and
2d between the divided electrodes 2a and 2b and gaps 3c and 3d
between the divided electrodes 3a, 3b are shif-ted frorn each
other (about 45 in this embodiment). The shifted angle
hetween gaps 2c and 3c or 2d and 3d may be 90~.
In a stator 4 of this embodiment, when alternating
current voltages is applied to the electrodes 2a and 3a, a
progressive wave (ellipse vibration) is generated as shown by
arrow A in Fig. 5(a). Also, when alternating current voltage
is applied to the electrodes 2a and 3b, a progressive wave
(ellipse vibration) is reversely generated as shown by arrow B
in Fig.5(a).
Explaining this principle, one half of the cylin-
drical piezoelectric vibrator is spread as shown in Fig. 5(b)
and when the current voltage is applied to the outside elec-
trode 2a and the inside electrode 3a, the piezoelectric vibra-
tor extends toward an arrow DE and shortens toward an arrow
FG. Thereby, the diametrical vibration in the cylindrical
piezoelectric vibrator generates as shown in arrows H in Fig.
5(c). Therefore, since the portion o~ the piezoelectric
vibrator 1, to which the alternating current voltage is ap-
plied, is vibrated by the diametrical vibration and the longi-
tudinal vibration, bu-t the por-tion of the piezoelectric vibra-
cor to which the voltage is not applied is not vibrated, a
twist vibration is generated is generated by the shift of the
electrodes 2a and 3a as shown by dotted line C in Fig. 5(a)
and progressive wave (ellipse vibration) generates on the end
portion and a side portion of the piezoelectric vibrator 1.
Also, when the alternating current voltage is ap-
plied to the electrodes 2a and 3b, the progressive wave (el-
lipse vibration) generates toward the arrow B in Fig. 5(a).
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As shown in Fig 6, when a rotary mernber S is pres-
sed on the end of the stator ~, the rotary member 5 is smooth-
ly rotated by the progressive wave.
In this embodiment, since the rotary member is con-
tacted with an end portion of the solid ceramics of the piezo-
electric vibrator and the electrodes 2a, 2b, 3a and 3b are
attached on the outside and inside portions, the electrodes
need not be protected from wear and tear.
When the rotary member 5 is pressed on the side por-
tion of the stator 4, also the rotary member 5 is smoothly
rotated by the progressive wave.
When the gaps 2c and 2d between the outside elec-
trodes 2a and 2b correspond with the gaps 3c and 3d between
the inside electrodes 3a and 3b, the progressive wave (ellipse
vibration) generates in one directi.on, but the direction of
this progressive vibration is unstable.
As a concre-te embodimen-t, referring to Fig. 7, a
rotary shaft 5a of the rotary member 5 is rotatably supported
with a bearing 7 mounted on the end wall of the case 6 and a
thrust bearing 8 between the end wall of the case 6 and the
rotary member 5. The stator 4 is strongly contacted with the
rotary member S by fixing a bottom plate 10 on the end of the
case 6 through a spring 9.
In this embodiment, when the alternating current
voltage is applied to the electrodes 2a and 3a or 3b, the pro-
gressive wave (ellipse vibration) is reversibly generated on
the stator 4 and thereby the rotary member 5 is rotated.
Referring to Fig.8, a plurality of balls are rotat-
ably attached with the rotary member 5, the rotary shaft 5a is
rotatably supported by the bearing 7 mounted on the end wall
of the case 6. Then the balls are put between a plate 12 on
the stator 5 and a pressure plate 13 in the case 6. I'he plate
12 of the stator 4 is strongly contacted with the balls of the
rotary member 5 by fixing a bot-tom plate 10 on the end of the
case 6 through a spring 9.
In this embodiment, when the alternating current
voltage is applied to the electrodes 2a and 3a or 3b, the
progressive wave (ellipse vibra-tion) is reversibly generated
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on the stator 4 through the plate 12. When the balls 11 are
rotated by the progressive wave on -the plate 12, the balls 11
are rolled and moved on the pressure plate 13 and thereby the
rotary member 5 is rotated.
Referring to Fig. 9 and Fig. 10, a frame 16 in which
lenses 15 are mounted is inserted into a hole of a case 14,
two projections 17a and 17b are engaged with two grooves 16a
and 16b and a spiral groove 18 i.s formed on the outside of the
frame 16. The ring type stator 4 is supported by projections
19 in the inside of the case 14 and a ring type rotary rnember
20 is contacted with the stator 4. A screw of a ring type
flange member 22 is engaged with a screw of the case 14 and
presses the rotary member 20 through a spring washer 21. A
projection 23 in the inside of the rotary member 20 is engaged
with the spiral groove 18.
In the above camera having the stator 4 according to
the present invention, when the alternating current voltage is
applied to the stator 4 as stated above, the rotary rnember 20
is rotated by the progressive wave generated on the end of the
stator 4. Since the rotary torque of the rotary member 20 is
large, the frame 16 is moved toward the right or left in Fig.
9 by making moved the projection of the rotary member in the
spiral groove 18. Also, since the rotary member 20 is pressed
on the stator 4 with the spring washer 21, when the power is
taken off, the rotary member 20 is pressed on the stator 4
with the spring washer 21, when the power is taken off, the
rotary member 20 is stopped in this position. Therefore,
there is no necessity for providing any mechanic member for
stopping the rotary member 20.
Referring to Fig. 11, the gaps 2c and 2d between the
electrodes 3a and 3b make obli~ue to the side face of the
cylindrical piezoelectric vibrator 1.
In this embodiment, when the alternating current
voltage is applied to the electrodes 2a and 3a or 3b, the pro-
gressive wave reversibly generates on the end and side por-
tions of the stator 4.
