Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND O~ THE INVENTION:
The present invention relates to an ultrasonic
driving device using a ring type piezoelectric vibrator.
In a known ultrasonic motor using a piezoelectric
vibrator, two groups of electrodes are attached to one side
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 shifted every
~/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 respectively generating alternating
current voltages having a ~/2 phase shift with respect to
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 ~/2 phase shift
with respect to each other are generated on the surfaces of
the ring type piezoelectric vibrator and then progressive
waves owing to a compound of the two standing waves are
generated on the surfaces of the ring type piezoelectric
vibrator. Therefore, when a rotary member is put on the ring
type plezoelectric 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
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vibrator is complex and the cost of the ultrasonic motor
becomes expensive.
There is a known ultrasonic motor comprising a
Langevin type vibrator having two ring type piezoelectric
vibrators put between two metal blocks. In this ultrasonic
motor, a twisting joint body is connected to the end of one
metal block by a bolt for fixing the metal blocks and the
piezoelectric vibrator and a rotary member is pressed on the
twisting joint body by a spring.
However, the composition of the ultrasonic motor is
complex and its cost becomes expensive.
SUMMARY OF THE INVENTION:
It is, therefore, the primary object of the present
invention to provide an ultrasonic driving device having a
simple composition.
It is another object of the present invention to
provide an ultrasonic driving device having a stator of an
unsymmetrical Langevin type vlbrator comprising one metal
block longer than the other metal block.
It is another object of the present invention to
provide an ultrasonic driving device for driving a driven
member by elliptic vi.bration comprising a compound vibration
superposed by torsional vibration to a longitudinal
vibration, progressive wave and so on, the elliptic vibration
being on the end surface and the side surface of a stator due
to a screw of the bolt fixed to two metal blocks and a
piezoelectric vibrator.
In order to accompiish the above and other objects,
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the present invention provides a stator comprising a long
metal block and a short metal block, a piezoelectric vibrator
or piezoelectric vibrators put between the long metal block
and the short metal block and a bolt for fixing the metal
blocks and the piezoelectric vibrator or piezoelectric
vibrators by means of screw threads on both sides thereof, an
alternating current power supply for generating high
frequency electric signals, and a driven member engaged with
the end surface or side surface of the stator, whereby
elliptic vibrations superposed by torsional vibration due to
the screw threads of the bolt to longitudinal vibration due
to the expansion and contraction of the piezoelectric
vibrator is generated on the end surface or side surface of
the stator and the driven member is driven by the elliptic
vibration.
BRIEF DESCRIPTION OF THE DRAWINGS:
Fig. 1 shows a sectional view of an ultrasonic
motor in the prior art.
Fig. 2 shows a plan view of a form of a
piezoelectric vibrator and a composition of electrodes of the
piezoelectric vibrator.
Fig. 3 shows a separated perspective view of the
stator of an ultrasonic motor in the prior art.
Fig. 4 shows a side view having a partial sectional
view of an ultrasonic motor in the prior art.
Fig. 5 shows a side view of a stator of an
ultrasonic driving device for explaining the principle of the
~resent invention.
O.
Fig. 6 shows a sectional view of a stator of an
ultrasonic driving device in the present invention.
5Fig. 7 shows a side view of an ultrasonic motor in
the present invention.
Fig. 8 shows a plan view of a supporting plate for
fixing a stator of the present invention.
Fig. 9 shows a front view of an ultrasonic driving
device of the present invention.
Fig. 10 shows a front view of another ultrasonic
driving device of the present invention.
Fig. 11 shows a front view of another ultrasonic
driving device of the present invention.
15Fig. 12 shows a side view having a sectional view
in one part of an ultrasonic motor of the present invention.
Fig. 13 shows a front view of an ultrasonic driving
device of the present invention.
Fig. 14 a front view of an ultrasonic driving
device of the present invention.
Figs. 15-20 show side views of stators of the
present invention.
Fig. 21 shows a side view of an ultrasonic driving
device of another embodiment of the present invention.
25Fig. 22 shows vibration waves generated in each
portion of the stator in Fig. 21.
Fig. 23 shows a side view of an ultrasonic motor of
another.embodiment of the present invention.
Fig. 24 shows a longitudinal wave and torsional
wave generated in a stator consisting of an unsymmetrical
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Langevin type vibrator in Fig. 23.
Fig. 25 shows a perspective view of a stator of
another embodiment of the present invention.
Fig. 26 shows a sectional side view of the stator
in Fig. 25.
Fig. 27 (a) shows a vibration wave to a radial
direction of the stator in Fig. 25.
Fig. 27 (b) and (c) shows a elliptic vibration
generated in the stator in Fig. 25.
Fig. 27 (d) shows a direction generating elliptic
vibration and torsional vibration.
F'ig. 28 (a) and (b) shows a perspective view and a
side view of an end face of the stator in Fig. 25.
Fig. 29 shows a sectional view of another
embodiment of the present invention.
DESCRIPTION QF THE PREFERRED EMBODIMENTS:
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 vibrates the
resilient member A in unison. The piezoelectric vibrator B
is divided into 17 parts by the ratio of e.g. 22.5~ or
11.25. The neighbouring portions in the 17 parts of the
piezoelectric vibrator B are polarized by a reverse polarity
to each other as shown in Fig. 2. The two portions C and D
in the one side of the piezoelectric vibrator B are
respectively 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 a slider E is
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attached is mounted on the resilient member A.
In the ultrasonic motor in the prior art, the
alternating current voltage of VOsin~t is applied to the one
electrode C and the alternating current voltage Vocos~t is
applied to the other electrode D, where V0 is the
instantaneous value, w is radian frequency and t is time.
The phases of these voltages shift by ~, a with respect to
each other. Thereby, the divided portions of the
piezo~lectric vibrator B alternately produce expansion and
contraction and thus, the piezoelectric vibrator B produces a
bending vibration. Therefore, a standing wave is generated
in the piezoelectric vibrator B and a progressive wave is
generated on the piezoelectric vibrator B. Thus, the driven
member F having the slider E is rotated on the resilient
member A.
However, in the prior art ultrasonic motor, because
the divided portion of the ring type piezoelectric 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
complex.
Referring to the prior art in Fig. 3, a
piezoelectric vibrator 3, a terminal plate 4, a piezoelectric
vibrator 5, a terminal plate 6 and an aluminum disk 7 are put
on a washer 1 and bolt 2 is inserted into the center holes of
these members. The screw 2a of the bolt 2 is engaged with
the screw hole 8a of a twisting joint body 8. A drain 8b is
formed on the under surface of the twisting joint body 8,
arcuate projections 8c are formed in both sides of drain 8b,
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and a beam 8d is so formed in the upper portion of the
twisting joint body 8 that an angle between the beam 8d and
drain 8b becomes a predetermined value.
In this prior ultrasonic driving device, when
alternating current voltage is applied through the terminal
plates 4 and 6 to the piezoelectric vibrators 3 and 5 and the
piezoelectric vibrators 3 and 5 are vibrated in the direction
of their thickness, the arcuate projections 8c of the
twisting joint body 8 are pushed and twisted by the vibration
of the piezoelectric vibrators 3 and 5. Therefore, the
twisting joint body 8 is vibrated to be twisted. When the
excitation frequency of the alternating current voltage
approaches a resonance frequency, elliptic vibration arises
on the beam 8d of the twisting joint body 8.
Therefore, as shown in Fig. 4, a rotary member 9 is
put on the twisting joint body 8, a center bolt 10 passed
through a bearing 11 of the rotary member 9 and is fixed to
the twisting joint body 8, and a spring 12 is attached
between the upper end of the bolt 10 and the bearing 11,
whereby the rotary member 9 is strongly touched on the beam
8d of the twisting joint body 8 and is rotated by the
elliptic vibration on the beam 8d.
However, in the prior ultrasonic motor, the
composition of the twisting joint body 8 is complex and
strong torque cannot be obtained by the composition of the
ultrasonic motor.
Referring to fig. 5, a stator 20 in the ultrasonic
driving device of the present invention consists of a short
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metal block 13, a long metal block 14, ring type
piezoelectric vibrators 15 and 16 of piezoelectric ceramics
and so on and electrodes 17 and 18. The piezoelectric
vibrators 15 and 16 and the electrodes 17 and 18 are inserted
between the short metal block 13 and long metal block 14, and
the short metal block 13 and long metal block 14 are fixed in
unison by respectively engaging the screw holes of these
blocks 13 and 14 with the screws l9a and l9b of a bolt 19 as
shown in Fig. 6.
When alternating current voltage is applied from an
alternating current power supply 21 through the electrodes 17
and 18 to the piezoelectric vibrators 15 and 16 of the stator
20, it is confirmed that elliptic vibration generates on the
side of the stator 20 to the direction of the arrows as shown
in Fig. 5.
Explaining the principle for generating the
elliptic vibration in the stator 20, when the alternating
current voltage is applied to the terminals 17a and 18a of
the electrodes 17 and 18, the piezoelectric vibrators 15 and
16 vibrate in expansion and contraction. When the
piezoelectric vibrators 15 and 16 expand longitudinally, the
metal blocks 13 and 14 are longitudinally compressed and then
these side surfaces of the metal blocks 13 and 14 expand.
Also, because the screw holes of the metal blocks 13 and 14
and the screws l9a and l9b of the bolt 19 are obliquely
formed, twist arises in the metal blocks 13 and 14 by the
expansion of the piezoelectric vibrators 15 and 16 and each
oblique thread of the s'crews l9a and l9b of the bolt 19 and
elliptic vibrations A and B arise on the side surfaces
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of the metal blocks 13 and 14 as shown by the arrows of Fig.
5. By the reaction of these elliptic vibrations A and B, the
reverse elliptic vibrations as shown by arrows C and D re-
spectively arise apart from dead zones 22a and 22b. The
elliptic vibration B arising in the long metal block 14 is
stronger than the elliptic vibration A in the short metal
block 13. The directions of these elliptic vibrations A-D
are decided by the right-hand screw or left-hand screw of the
screw holes of the metal blocks 13 and 14 and by the oblique
direction of the pitch of the thread of the screws l9a and
l9b of the bolt 19.
Referring to Fig. 7, an ultrasonic motor of the
present invention using the stator 20 is shown. A cap member
24 is fixed in the end 23a of a case 23 by means of its screw
and the rotary shaft 27 of the rotary member 26 is supported
to rotate by a bearing 25 attached to the cap member 24. The
portion 27' of the rotary shaft 27, which is near to the ro-
tary member 26, is biggér than the other portion and even if
the rotary member 26 is pressed vertically, the rotary member
20 26 is untouched to the cap member 24. The stator 20 is sup-
ported in its dead zone by two ring supporters 28 which are
fixed by screws 29 as shown in Fig. 8. Opposed projections
28a and 28b of the ring supporters 28 are respectively in-
serted in drains 30 and thus the ring supporters 28 are sup-
ported in the case 23 to be longitudinally moved, but not to
be rotated by the ring supporters 28. A bottom member 31 is
engaged in the other end 23b of the case 23 by means of its
screw. The stator 20 is pressed by a spring 32 put in the
-~r bottom member 31 and strongly touches the rotary member 26.
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The pressure of the spring 32 is suitably changed by means of
rotation of the bottom member 31.
In the ultrasonic motor of the embodiment in the
present invention, when alternating current voltage is
applied from an alternating current power supply through the
terminals 17a and 18a to the piezoelectric vibrators 15 and
16, the elliptic vibration arises on the end surface 20a of
the stator 20 as explained in the above. Therefore, the
rotary member 26 touched on the surface 20a of the stator 20
can be smoothly rotated with a large torque.
When the rotary member 26 or stator 20 is easily
abraded, an abrasion resistance member is put between the
rotary member 26 and the stator 20 to prevent abrasion.
Referring to Fig. 9, another ultrasonic driving
device in the present invention is shown. Rotary disks 33
and 34 are fixed on the rotary shaft 35 which is supported to
rotate by bearings 36 and 37. Springs 38 and 39 are
supported to press the rotary disks 33 and 34 to the side
surface of the stator 20. A drain 40 is formed in the dead
zone of the stator 20.
In this ultrasonic driving device, when the rotary
disk 33 is touched on the side surface of the stator 20 and
the rotary disk 34 is put on the drain 40 by shifting the
rotary disk 33 or the stator 20, the rotary disk 33 is
rotated toward the arrow B. Also, when the rotary member 34
is touched on the side surface of the stator 20 and the
rotary disk 34 is put on the drain 40 by shifting the rotary
disk 33 or the stator 20, the rotary disk 34 is reversely
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rotated as shown in the arrow D. When an obliquity is formed
on the edges of the drain 40, the shift of the rotary disks
33 and 34 or the stator 20 becomes easy.
Referring to Fig. 10, a further ultrasonic driving
device in the present invention is shown. Belts 41 and 42
are hung between the side of the stator 20 in which the
elliptic vibration arises and pulleys 45 and 46 are fixed on
rotary shafts 43 and 44 which are supported by a bearing 47.
In this ultrasonic driving device, the rotary
shafts 43 and 44 are reversely rotated with respect to each
other.
Referring to Fig. 11, a further ultrasonic driving
device of the present invention is shown. A shaft 50 is
supported by bearing 48 and 49 to be moved linearly and is
pressed on the side of the stator 20 at which the elliptic
vibration arises by springs 51 and 52.
This ultrasonic driving device can be used as a
linear motor.
In the above embodiments, the long metal block 14
of the stator 20 is cylindrical, but the elliptic vibration
can arise in a stator formed by a frustconical metal block.
Referring to Fig. 12, 23 designates a case, 24; a
cap member, 25; a bearing, 26; a rotary member, 27; a rotary
shaft, 28; two ring supporters, 30; drains, 31; a bottom
member. These elements are the same as those in Fig. 7,
but, in the embodiment, the long metal block 14 of the stator
20 is frustconical and a spring 53 consists of an arcuate
-p leaf spring.
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Even if the long metal block 14 is frustconical,
elliptic vibration arises on the side surface and the end
surface of the stator 20 as explained above and the rotary
member 26 can be driven, when alternating current voltage is
applied to the piezoelectric vibrator of the stator 20.
Referring to Fig. 13, a shaft 55 for fixing a
rotary member 54 is supported by bearings (not shown) and the
oblique surface 54' of the rotary member 54 is touched on the
oblique side surface of the frustconical metal block 14 of
the stator 20 by springs (not shown).
In the ultrasonic driving device of the present
invention, the rotary member 54 is rotated by the elliptic
vibration arising on the side surface of the stator 20. The
rotary member 55 is engaged with other rotary members through
gears or pulleys.
Referring to Fig. 14, a shaft 53 is supported to
longitudinally slide by bearings 56 and 57 and is pressed on
the oblique side surface of the stator 20 by springs 59 and
60.
This ultrasonic driving device can be used as a
linear motor.
Referring to Fig. 15, a long metal block 14 in a
stator 20 consists of a cylindrical portion 61a and a
frustconical portion 61b.
Referring to Fig. 16, a long metal block 14
consists of a long cylindrical portion 62a and a short
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frustconical portion 62b.
Referring to Fig. 17, a long metal block 14 is
frustconical and a small diameter portion 63a of the long
metal block 14 is attached to the piezoelectric vibrator of
the stator 20 and a large diameter portion 63b is formed in
the end of the stator 20.
Referring to Fig. 18, a long metal block 14
consists of a cylindrical portion 64a and a frustconical
portion 64b. The small diameter portion of the frustconical
portion 64b is attached to the cylindrical portion.
Referring to Fig. 19, a projection 65 is formed on
the portion near the end of the long metal block 14 in which
the elliptic vibration arises.
Referring to Fig. 20, a projection 66 is formed on
the portion near the center of the long metal block 14 in
which the elliptic vibration arises.
Referring to Fig. 21, an ultrasonic driving device
of another embodiment of the present invention is shown. In
a stator 20, a screw l9b of a bolt 19 is engaged with a screw
hole of a long metal block 14 by means of a screw and the
other screw l9a of the bolt 19 is passed through a short
metal block 13 and is engaged with a nut 67.
As shown in Fig. 22 (a), the whole length of the
stator 20 consisting of the metal blocks 13 and 14, the
25 piezoelectric vibrators 15 and 16 and the nut 67 are matched
by a resonance wave {1.5 wave in Fig. 22 (a)} of torsional
vibration, the whole length of the stator 20 is matched by a
resonance wave {one wave in Fig. 22 (b)} of longitudinal
~3a~;~;30
vibration, and the length of bolt 19 is matched by a
resonance wave {one wave in Fig. 22} of torsional vibration.
When alternating current voltage is applied from an
alternating current power supply 21 to the piezoelectric
vibrators 15 and 16, the stator 20 resonates with the
longitudinal vibration of the piezoelectric vibrators 15 and
16. Therefore, the stator 20 resonates with the torsional
resonance and also the bolt 19 resonates with the torsional
resonance. Therefore, strong elliptic vibrations arise on
the nut 67 fixed in the end of the bolt.
Thus, when a rotary member 68 is strongly touched
to the nut 67, the rotary member 68 is rotated with a strong
torque. In this ultrasonic motor, the rotary member 68 can
be rotated by a rotating force stronger than that of the
prior art ultrasonic driving devices.
Referring to Fig. 23, an ul~rasonic motor of
another embodiment of the present invention is shown. In a
stator 20, piezoelectric vibrators 15 and 16 are put between
a long metal block 14 and a short metal block 13 which are
fixed by screws l9a and l9b of a bolt 19.
Because it is difficult that this stator 20 is
matched by resonance of longitudinal vibration and torsional
vibration respectively, a drain 69 is so formed on the side
surface of the long metal block 14 that elliptic vibration
arises on the side of the drain 69. That is, the drain 69 is
formed in a side surface of the long metal block 14 in which
the antinode of the resonance of torsional vibration shown in
Fig. 24 (a) exists with the antinode of the resonance of
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longitudinal vibration shown in Fig. 24 (b).
In the stator 20, balls 71 supported in a rotary
member 70 are touched on the side wall 69a and a press plate
72 and springs 73 are put between the opposite side wall 69b
of the drain 69 and the balls 71. When alternating current
voltage is applied to the piezoelectric vibrators 15 and 16,
the antinode of the resonance of the longitudinal vibration
exists with the antinode of the resonance of the torsional
vibration, and thus, elliptic vibrations arise on the side
wall 69a, and the balls 71 are rotated by the elliptic
vibration and the rotary member 70 is rotated by the balls
71. The rotary shaft 74 of the rotary member 70 is supported
by a bearing 75 attached on the end surface of the long metal
block 14.
Referring to Figs. 25 and 26, a stator 20 of
another embodiment of the present invention is shown. In
this stator, piezoelectric vibrators 15 and 16 are put
between a long metal block 14 and a short metal block 13
which is engaged with a screw l9a of the bolt 19. The bolt
19 is passed through each hole of the piezoelectric vibrators
15 and 16 and the long metal block 14 and the screw l9b of
the bolt 19 is engaged with a nut 76.
When alternating current voltage is applied to the
piezoelectric vibrators 15 and 16 of the stator 20, the long
metal block 14 produces a radial vibration in a reference
fre(auency as shown in dotted lines B and C of Fig. 27 (a)
toward the inside and outside of a solid line A and the
radial vibration of the long metal block 14 produces elliptic
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vibrations as shown in dot~ed lines D and E by a second
harmonic component. In Fig. 27 (d), assuming that the
direction of the elliptic vibrations D and E is designated F,
torsional vibration G of the bolt 19 produced by the second
harmonic component of the longitudinal vibration is shifted
90. Therefore, as shown in dotted line H or H' of figs. 28
(a) and (b), rotary vibration is produced by compounding the
plane elliptic vibration with the torsional vibration in the
end of the long metal block 14.
Therefore, when a rotary member is engaged with the
end of the metal block, the rotary member is rotated with a
strong tor~ue and because the plane elliptic vibration is
applied to the short metal block 13 b~ the second harmonic
component, the whole length of the metal blocks 13 and 14 and
the piezoelectric vibrators 15 and 16 becomes short.
Referring to -Fig. 29, another ultrasonic driving
device of the present invention is shown. In a stator 20
having metal blocks 13 and 14 and piezoelectric vibrators 15
and 16, a hole l9c is longitudinally opened in the center of
a bolt 19 and a bolt 77 i5 passed through the hole l9c.
Also, balls 79 supported by a rotary member 78 are put
between a supporter 80 and the end of the stator 20 and the
screw of the bolt 77 is engaged with a nut 82 to press the
balls 79 to the stator 20. Therefore, rotation power is take
out of a rotary shaft 78b of the rotary member 78 through
arms 78a.
In the ultrasonic driving device, the balls 79 are
moved by the elliptic vibration arising on the end of the
long metal block 14 of tne stator 20 and thus, the balls 79
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are moved to rotate on the surface of the supporter 80.
Therefore, the rotary member 78 is driven and a rotary forc~
is taken out of the rotary shaft through the arms 78a.
As stated above, the ultrasonic driving device of
the present invention can generate a torque stronger than
that of the prior ultrasonic motor and the stator 20, the
balls 79 and the rotary member 78 are prevented from abrasion
by supplying lubricant of grease and so on.
In the above embodiment of the present invention,
though the elliptic vibration is generated on the short metal
block 13 by the second harmonic component of the longitudinal
vibration, higher harmonic components of the longitudinal
vibration may be used.
