U.S. patent application number 12/047687 was filed with the patent office on 2008-11-20 for vibration actuator, lens barrel, camera, manufacturing method for vibration body and manufacturing method for vibration actuator.
This patent application is currently assigned to Nikon Corporation. Invention is credited to Takahiro SATO.
Application Number | 20080284285 12/047687 |
Document ID | / |
Family ID | 39982422 |
Filed Date | 2008-11-20 |
United States Patent
Application |
20080284285 |
Kind Code |
A1 |
SATO; Takahiro |
November 20, 2008 |
VIBRATION ACTUATOR, LENS BARREL, CAMERA, MANUFACTURING METHOD FOR
VIBRATION BODY AND MANUFACTURING METHOD FOR VIBRATION ACTUATOR
Abstract
To provide a vibration actuator, a lens barrel, a camera, a
manufacturing method for a vibration body and a manufacturing
method for a vibration actuator, which have a high driving
efficiency and can lead to easy manufacture. A vibration actuator
of the present invention is provided with an elastic body and an
electromechanical transducer element sintered onto the elastic body
in the state that the element is divided into a plurality of areas
by a groove-shaped border portion.
Inventors: |
SATO; Takahiro;
(Yokohama-shi, JP) |
Correspondence
Address: |
DITTHAVONG MORI & STEINER, P.C.
918 Prince St.
Alexandria
VA
22314
US
|
Assignee: |
Nikon Corporation
Tokyo
JP
|
Family ID: |
39982422 |
Appl. No.: |
12/047687 |
Filed: |
March 13, 2008 |
Current U.S.
Class: |
310/323.16 ;
29/25.35 |
Current CPC
Class: |
Y10T 29/4908 20150115;
Y10T 29/49155 20150115; H02N 2/163 20130101; Y10T 29/42 20150115;
G02B 7/102 20130101; Y10T 29/49128 20150115; G02B 7/08 20130101;
Y10T 29/49005 20150115; H01L 41/43 20130101; H01L 41/333
20130101 |
Class at
Publication: |
310/323.16 ;
29/25.35 |
International
Class: |
H01L 41/04 20060101
H01L041/04; H01L 41/22 20060101 H01L041/22 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 14, 2007 |
JP |
2007-065126 |
Mar 11, 2008 |
JP |
2008-060499 |
Claims
1. A vibration actuator comprising: an elastic body provided on a
vibration body; and an electromechanical transducer element
sintered onto the elastic body in a state that the element is
divided into a plurality of areas by a groove-shaped border
portion.
2. The vibration actuator according to claim 1, wherein the
electromechanical transducer element is separated into a plurality
of independent areas by the border portion.
3. The vibration actuator according to claim 1, wherein electrodes
are formed on a surface of the plurality of areas of the
electromechanical transducer.
4. The vibration actuator according to claim 3, wherein no
electrode is formed on a surface of an end portion other than an
end portion touching the border portion of the plurality of
areas.
5. The vibration actuator according to claim 1, wherein the
electromechanical transducer element is manufactured by injection
molding.
6. The vibration actuator according to claim 1, wherein an interval
on a surface of the electromechanical transducer element between
adjacent areas of the plurality of areas is 0.1 mm or less.
7. The vibration actuator according to claim 1, further comprising
a movable body in pressure-contact with a face on an opposite side
of a face where the electromechanical transducer element of the
elastic body is provided.
8. The vibration actuator according to claim 7, further comprising
a pressurizing section generating a pressurizing force to
pressure-contact the elastic body and the movable body, and
provided on a face side on which the electromechanical transducer
element of the elastic body is provided.
9. A lens barrel provided with the vibration actuator according to
claim 1.
10. A camera provided with the vibration actuator according to
claim 1.
11. A manufacturing method for a vibration body, comprising: a
first step of providing an electromechanical transducer element on
an elastic body in a state that the element is divided into a
plurality of areas by a groove-shaped border portion; and a second
step of sintering the elastic body and the electromechanical
transducer element.
12. The manufacturing method for a vibration body according to
claim 11, wherein the first step further comprises providing the
electromechanical transducer element divided into a plurality of
independent areas by the groove-shaped border portion.
13. The manufacturing method for a vibration body according to
claim 11, further comprising, after the second step, a third step
of forming electrodes on a surface of the plurality of areas of the
electromechanical transducer element.
14. The manufacturing method for a vibration body according to
claim 13, further comprising, after the third step, a fourth step
of polarizing the electromechanical transducer element for each of
the plurality of areas.
15. The manufacturing method for a vibration body according to
claim 11, wherein the first step provides the electromechanical
transducer element by injection molding.
16. The manufacturing method for a vibration body according to
claim 11, wherein in the first step, the electromechanical
transducer element is provided such that an interval between
adjacent areas of the plurality of areas on a surface of the
electromechanical transducer element is 0.1 mm or less.
17. The manufacturing method for a vibration actuator, according to
claim 11, wherein a movable body is provided in pressure-contact
with a face on an opposite side of a face where the
electromechanical transducer element of the elastic body is
provided.
18. The manufacturing method for a vibration actuator according to
claim 17, wherein a pressurizing section generating a pressurizing
force to pressure-contact the elastic body and the movable body is
provided on a face side on which the electromechanical transducer
element of the elastic body is provided.
Description
[0001] The disclosure of the following priority application is
herein incorporated by reference: Japanese Patent Application No.
2007-065126 filed on Mar. 14, 2007 and No. 2008-060499 filed on
Mar. 11, 2008.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a vibration actuator, a
lens barrel, a camera, a manufacturing method for a vibration body
and a manufacturing method for a vibration actuator.
[0004] 2. Description of the Related Art
[0005] A vibration actuator causes an electromechanical transducer
element to expand and contract based on a driving signal, and using
this expansion and contraction, generates a progressive vibrational
wave (hereinafter, referred to as a progressive wave) into a
driving surface of an elastic body. Then, the vibration actuator
generates elliptic motion in the driving surface based on this
progressive wave, and gives rise to a driving force by driving a
relative displacement member that has been brought into
pressure-contact with a crest of a wave of the elliptic motion.
[0006] In such vibration actuators, various improvements with
respect to enhancement of the driving efficiency and other aspects
have been achieved. The prior art (for example, see Japanese
Unexamined Patent Application No. S63-220782) discloses an example
of providing a partitioning border portion in a piezoelectric
element main body, wherein the border portion comprises a notch
taking the form of a groove in at least a part of the piezoelectric
element in a thickness direction to partition the piezoelectric
element for each electrode area.
[0007] However, the method disclosed in this prior art has the
problem of a large number of manufacturing steps of the
piezoelectric element leading to increases in production costs.
SUMMARY OF THE INVENTION
[0008] An object of the present invention is to provide a vibration
actuator, a lens barrel, a camera, a manufacturing method for a
vibration body and a manufacturing method for a vibration actuator,
which have an enhanced driving efficiency and can be easily
manufactured.
[0009] The present invention achieves said object by virtue of the
means described below.
[0010] According to a first aspect of the present invention, there
is provided a vibration actuator comprising: an elastic body
provided on a vibration body; and an electromechanical transducer
element sintered onto the elastic body in a state that the element
is divided into a plurality of areas by a groove-shaped border
portion.
[0011] The electromechanical transducer element may be separated
into a plurality of independent areas by the border portion.
[0012] In the first aspect of the present invention, electrodes may
be formed on a surface of the plurality of areas of the
electromechanical transducer.
[0013] No electrode may be formed on a surface of an end portion
other than an end portion touching the border portion of the
plurality of areas.
[0014] The electromechanical transducer element may be manufactured
by injection molding.
[0015] An interval on a surface of the electromechanical transducer
element between adjacent areas of the plurality of areas may be 0.1
mm or less.
[0016] A movable body in pressure-contact with a face on an
opposite side of a face where the electromechanical transducer
element of the elastic body may be provided.
[0017] A pressurizing section generating a pressurizing force to
pressure-contact the elastic body and the movable body, and
provided on a face side on which the electromechanical transducer
element of the elastic body may be provided.
[0018] According to a second aspect of the present invention, there
is provided a lens barrel provided with the vibration actuator
according to the first aspect of the present invention.
[0019] According to a third aspect of the present invention, there
is provided a camera provided with the vibration actuator according
to the first aspect of the present invention.
[0020] According to a fourth aspect of the present invention, there
is provided a manufacturing method for a vibration body,
comprising: a first step of providing an electromechanical
transducer element on an elastic body in a state that the element
is divided into a plurality of areas by a groove-shaped border
portion; and a second step of sintering the elastic body and the
electromechanical transducer element.
[0021] The first step may further comprise providing the
electromechanical transducer element divided into a plurality of
independent areas by the groove-shaped border portion.
[0022] After the second step, a third step of forming electrodes on
a surface of the plurality of areas of the electromechanical
transducer element may be comprised.
[0023] After the third step, a fourth step of polarizing the
electromechanical transducer element for each of the plurality of
areas may be comprised.
[0024] The first step may provide the electromechanical transducer
element by injection molding.
[0025] In the first step, the electromechanical transducer element
may be provided such that an interval between adjacent areas of the
plurality of areas on a surface of the electromechanical transducer
element is 0.1 mm or less.
[0026] A movable body may be provided in pressure-contact with a
face on an opposite side of a face where the electromechanical
transducer element of the elastic body is provided.
[0027] A pressurizing section generating a pressurizing force to
pressure-contact the elastic body and the movable body may be
provided on a face side on which the electromechanical transducer
element of the elastic body is provided.
[0028] According to the present invention, it is possible to
provide a vibration actuator, a lens barrel, a camera, a
manufacturing method for a vibration body and a manufacturing
method for a vibration actuator, which have an enhanced driving
efficiency and can be easily manufactured.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] In the drawings attached:
[0030] FIG. 1 is an illustration showing a camera using an
ultrasound motor of the present embodiment;
[0031] FIG. 2 is a cross-sectional view of an ultrasound motor of
the present embodiment;
[0032] FIG. 3A is a view showing a vibration body of the present
embodiment when the vibration body is viewed from the side of the
pressurizing section;
[0033] FIG. 3B is a perspective view showing a vibration body of
the present embodiment, showing a piezoelectric body and an elastic
body in a separated state;
[0034] FIG. 4 is a process chart showing a manufacturing method for
a vibration body of the present embodiment; and
[0035] FIG. 5 is a schematic diagram for explaining an injection
molding process in detail.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0036] Hereinafter, a more detailed description will be given with
reference to the drawings and so on by way of an embodiment of the
present invention. It should be noted that the following embodiment
is described with an example of the use of an ultrasound motor
utilizing a vibration area of an ultrasound wave as a vibration
actuator.
[0037] FIG. 1 is an illustration showing a camera 1 using an
ultrasound motor 10 of the present embodiment.
[0038] The camera 1 of the present embodiment is provided with a
camera body 2 having an image pickup device 6, and a lens barrel 3.
The lens barrel 3 is an interchangeable lens that is attachable to
and detachable from the camera body 2. It should be noted that the
camera 1 of the present embodiment forms an example for which the
lens barrel 3 is an interchangeable lens, but the invention is not
limited to this, and the lens barrel 3 may be, for example, a lens
barrel formed in an integrated fashion with the camera body.
[0039] The lens barrel 3 is provided with a lens 4, a cam tube 5,
an ultrasound motor 10 and so on. In the present embodiment, the
ultrasound motor 10 is used as a driving source for driving the
lens 4 during a focusing operation of the camera 1, and the driving
force gained from the ultrasound motor 10 is transferred to the cam
tube 5. The lens 4 is in cam-engagement with the cam tube 5, and if
the cam tube 5 rotates by the driving force of the ultrasound motor
10, then the lens 4 moves based on the cam-engagement with the cam
tube 5 so as to perform focusing.
[0040] FIG. 2 is a cross-sectional view of an ultrasound motor 10
of the present embodiment.
[0041] The ultrasound motor 10 of the present embodiment is
provided with a vibration body 11, a movable body 14, a shock
absorber member 15, a supporting body 16, a shock absorber member
17, a pressurizing section 18, a securing member 19 and so on.
[0042] The vibration body 11 is provided with an elastic body 12, a
piezoelectric body 13 and so on.
[0043] The elastic body 12 is a substantially circular ring shaped
member formed using a metallic material capable of being
elastically deformed such as an iron alloy, e.g. a stainless steel
material or an Invar material, brass or the like, one face of which
is provided with a piezoelectric body 13 and another face of which
is provided with a comb tooth section 12b formed by slotting it to
form a plurality of grooves 12a. The apical surface of this comb
tooth section 12b is a driving surface in which a progressive wave
emerges due to excitation of the piezoelectric body 13 to drive the
movable body 14.
[0044] The piezoelectric body 13 has a function of converting
electric energy into mechanical energy, and in the present
embodiment, is formed using PZT (piezoelectric zirconate titanate
or lead (Pb) zirconate titanate). This piezoelectric body 13 is
formed as a plurality of bodies for each area of an electrode 131
(see FIG. 3A) to which a driving signal is input, and the bodies 13
are sintered onto the elastic body 12. The electrode 131 is
electrically connected to a flexible printed board, not shown, and
a driving signal supplied from this flexible printed board excites
the piezoelectric body 13. The detailed shape of the piezoelectric
body 13 of the present embodiment will be described later.
[0045] The movable body 14 is a member taking the form of a
substantially circular ring, and is brought into pressure-contact
with the driving surface of the elastic body 12 by a pressurization
force of the pressurizing section 18 described later and is
frictionally driven by a progressive wave of the elastic body
12.
[0046] The shock absorber member 15 is a substantially circular
ring shaped member formed using rubber or the like. This shock
absorber member 15 is a member for preventing vibrations of the
movable body 14 from being transferred to the side of the
supporting body 16, and is provided between the movable body 14 and
the supporting body 16.
[0047] The supporting body 16 is a member for supporting the
movable body 14, and is a member that rotates integrally with the
movable body 14 to transfer the rotary movement of the movable body
14 to a driven member (not shown) and regulates the position of the
movable body 14 in the direction of a rotational center axis.
[0048] The pressurizing section 18 is a part for generating a
pressurization force causing the vibration body 11 and the movable
body 14 to be brought into pressure-contact with each other, and is
provided with a pressurization plate 18a and a disc spring 18b. The
pressurization plate 18a is a plate taking the form of a
substantially circular ring, which receives the pressurization
force generated by the disc spring 18b.
[0049] The shock absorber member 17 is a member taking the form of
a substantially circular ring, which is formed using a nonwoven
fabric, felt or the like. This shock absorber member 17 is a member
for preventing the vibrations of the vibration body 11 from being
transferred to the side of the pressurizing section 18, and is
provided between the piezoelectric body 13 and the pressurization
plate 18a.
[0050] The securing member 19 is a member for securing the
ultrasound motor 10 of the present embodiment to the lens barrel
3.
[0051] Herein, the shape of the piezoelectric body 13 is described
in more detail.
[0052] FIG. 3 is a set of illustrations showing the vibration body
11 of the present embodiment. FIG. 3A is an illustration of the
vibration body 11 when viewed from the side of the pressurizing
section 18, which shows that electrodes 131 are formed in the
portions shown by oblique lines. FIG. 3B is a perspective view
showing the piezoelectric body 13 and the elastic body 12
separately for the purpose of facilitating understanding.
[0053] As shown in FIG. 3, a plurality of the piezoelectric bodies
13 of the present embodiment are independently formed on the
surface on the side opposite to the driving surface of the elastic
body 12. The manufacturing method for this piezoelectric body 13
and the vibration body 11 will be described later.
[0054] As shown in FIG. 3A, the electrodes 131 are formed on the
piezoelectric bodies 13. These electrodes 131 are not formed on
both ends (the inner peripheral end and outer peripheral end) of
the piezoelectric bodies 13 in the radial direction of the elastic
body 12, for the purpose of preventing discharge in the
polarization process, and the base material portions of the
piezoelectric bodies 13 are exposed to the exterior with a
predetermined width at both ends of the piezoelectric bodies 13 in
the radial direction of the elastic body 12. On the other hand, the
electrode 131 is formed on both ends of the piezoelectric body 13
in the circumferential direction of the elastic body 12.
[0055] In addition, the piezoelectric body 13 is not formed between
the adjacent electrodes 131 in the circumferential direction of the
elastic body 12, and when the vibration body 11 is viewed from the
side of the pressurizing section 18, it leads to a configuration in
which the elastic body 12 is visible. It should be noted that the
outside diameter of the elastic body and the piezoelectric body is
about 12 mm, and the inside diameter of the same is about 8 mm, in
the present embodiment. In this case, the formation is preferably
made so that the gap W between the adjacent electrodes 131
(piezoelectric bodies 13) is about 0.1 mm or less from the
viewpoint of improvement of the driving efficiency. In the present
embodiment, W=0.05 mm.
[0056] These piezoelectric bodies 13 are separated to form parts
receiving signals of two phases (A phase and B phase), and in the
part corresponding to each respective phase, elements of different
polarities (A1, A2, A3, A4, B1, B2, B3, B4) are lined up in such a
manner that polarization directions are arranged alternately for
each half-wavelength. Additionally, a portion having an interval of
1/4 wavelength between the A phase and the B phase corresponds to
the ground (G).
[0057] A manufacturing method for the vibration body 11 of the
present embodiment will now be described.
[0058] FIG. 4 is a process chart showing the method of
manufacturing the vibration body 11 of the present embodiment.
[0059] The manufacturing process of the vibration body 11 is
provided with a piezoelectric body preparation step S100, an
elastic body preparation step S200, an injection molding step S300,
a sintering step S400 and an electrode forming step S500 and a
polarizing step S600.
[0060] As shown in FIG. 4, the piezoelectric body preparation step
S100 is provided with a material ascertaining step S101, a material
weighing step S102, a material mixing step S103, a preliminary
sintering step S104, a crushing step S105, a granulating step S106,
a binder mixing step S107 and a pelletizing step S108.
[0061] The material ascertaining step S101 is a step of
ascertaining the properties of the material of the PZT, in which
for example an X-ray fluorescence apparatus is used to check
whether or not the purity of the PZT is equal to or more than
99.90%.
[0062] The material weighting step S102 is a step of measuring the
weight of the raw material of the PZT, in which for example a
precision balance is used to check whether or not the weight of a
raw material of the PZT corresponds to a predetermined target value
within a margin of error of 0.1 g or less.
[0063] The material mixing step S103 is a step of mixing the raw
material of the PZT and a predetermined material necessary for
sintering, in which for example a ball mill is used to carry out
the mixing for a predetermined amount of time (in the present
embodiment, two hours). Then, a particle size distribution analyzer
is used to check whether or not the particle diameter of the
mixture ranges from 1 to 2 .mu.m.
[0064] The preliminary sintering step S104 is a step of
preliminarily sintering the mixture, in which the preliminary
sintering is performed while for example a temperature recorder
and/or a temperature history sensor is used to check whether or not
the profile (setting) of the temperature is within a range of
.+-.5.degree. C. from 850.degree. C.
[0065] The crushing step S105 is a step of crushing the
preliminarily sintered object, in which for example a ball mill is
used to carry out the crushing for a predetermined amount of time.
Then it is ascertained whether or not the particle diameter of the
crushed object is between 1 to 2 .mu.m, using a particle size
distribution analyzer. In addition, an X-ray diffraction device is
used to check the ratio of the PZT included in the crushed object
from a crystalline phase of the PZT, and a specific surface area
measuring instrument is used to check whether or not the specific
surface area of the crushed object has a predetermined value (in
the present embodiment, 3 cm.sup.2/g).
[0066] The granulating step S106 is a step of solidifying the
powder of the crushed object to granulate it. Herein, for example a
spray dryer is used to dry the crushed object at a predetermined
temperature (in the present embodiment, 200.degree. C.), and
subsequently a predetermined amount of PVA (polyvinyl alcohol) is
added thereto to carry out the granulation. At this time, an SEM
(scanning electron microscope) is used to check whether or not the
diameter of the resultant granular particles has a predetermined
value (in the present embodiment, between 30 and 100 .mu.m) and
whether or not the PVA shows a predetermined ratio.
[0067] The binder mixing step S107 is a step of mixing the
granulated object with a predetermined amount of predetermined
binder, in which, for example a precision balance is used to check
whether or not the total weight of the mixture has an error of 1 g
or less from a predetermined target value. In the present
embodiment, PVB (polyvinyl butyral) is used as the binder.
[0068] The pelletizing step 108 is a step of pelletizing
(solidifying to make granular) the mixture, in which for example, a
pellet producing machine is used.
[0069] The elastic body preparation step S200 is provided with an
elastic body manufacturing step S201 for manufacturing the elastic
body 12. In the present embodiment, the elastic body 12 is made by
a cutting work process.
[0070] The injection molding step S300 is a step of melting the
pelletized mixture to curry out injection molding. FIG. 5 is a
schematic diagram for explaining this injection molding step S300
in more detail. In the injection molding step S300, the elastic
body 12 manufactured in the elastic body preparation step S200 is
placed in an elastic body forming mold 12A, as shown in the figure
(S301).
[0071] Subsequently, a piezoelectric element forming mold 13A is
placed in opposition to the elastic body forming mold 12A (S302).
This piezoelectric element forming mold 13A is provided with
partitions 13B for separating a cavity into which the pelletized
mixture is injected into a plurality of regions.
[0072] The partitions 13B are in contact with a surface of the
elastic body 12 in the state, shown in S302 in FIG. 5, that the
piezoelectric element forming mold 13A is placed in opposition to
the elastic body forming mold 12A. The pelletized mixture is
injected and molded into each region delimited by the partitions
13B (S303). It should be noted that this injection molding is
performed while an injection molding machine is used to check, for
example, whether the temperature of the mixture is between 160 and
170.degree. C., whether the pressure-maintaining pressure has a
predetermined value, and/or whether a pressure holding time has a
predetermined value, and the like.
[0073] Then, extra pressure is applied between the elastic body
forming mold 12A and the piezoelectric element forming mold 13A so
as to pressurize the elastic body 12 and the piezoelectric element
13 (S304). The pressurization value is preferably on the order of
0.5 t/cm.sup.2. It should be noted that this step may be omitted if
the elastic body 12 and the piezoelectric element 13 are
sufficiently pressurized during the injection (if the
pressurization value is on the order of 0.5 t/cm.sup.2).
[0074] The elastic body 12 and the piezoelectric element 13 are
removed from the elastic body forming mold 12A and the
piezoelectric element forming mold 13A (S305). It should be noted
that after the injection molding step S300, there is a resin
removal step for removing the resin binder that has become
unnecessary, for example wherein the resin removal is performed by
a pyrolytic method or the like.
[0075] Returning to FIG. 4, the sintering step S400 is a step of
heating the elastic body 12 and piezoelectric body 13 integrally
formed in the injection molding step S300 so as to sinter the
piezoelectric body 13, in which the sintering temperature of the
sintering step is preferably between 1000 and 1200.degree. C. The
sintering step S400 is performed while for example a temperature
recorder and/or a temperature history sensor is used to check
whether or not the profile of the temperature is within a range of
.+-.10.degree. C. from 1100.degree. C. In addition, after
completion of the sintering, a precision balance is used to check
whether or not the sintered density has a predetermined value, and
an SEM is used to check whether or not the diameter of a
crystalline particle has a predetermined value (in the present
embodiment, on the order of 2 .mu.m). By this sintering step S400,
the mixture for the piezoelectric body becomes the sintered body of
the piezoelectric body 13, and is bonded completely to the elastic
body 12.
[0076] The electrode forming step S500 is a step of forming an
electrode on the piezoelectric body 13, in which for example a
screen printing machine is used to form the electrodes 131 based on
a printing process. In addition, an SEM is used to check whether or
not the film thickness of the printed electrodes 131 is between 2
and 5 .mu.m.
[0077] The polarizing step S600 is a step of polarizing the
piezoelectric body 13, in which for example a predetermined power
supply is used to apply a voltage of 25 kV/cm.sup.2 to the body 13.
Additionally, a thermometer is used to adjust the temperature of
the piezoelectric body 13 at the time of polarization to
100.degree. C., and a timer is used to apply the voltage to the
body 13 for 30 minutes. It should be noted that the polarization
needs to be performed with the piezoelectric body 13 being
sandwiched between a positive electrode and a negative electrode,
but in the present embodiment, the electrode 131 formed by the
printing process is used as one of the electrodes and the elastic
body 12 is used as the other.
[0078] After the polarizing step S600, polishing processing and the
like are carried out for maintaining the planarity of the driving
surface of the elastic body 12 if necessary, and then the vibration
body 11 of the present embodiment is completed. After that, the
ultrasound motor 10 of the present embodiment is completed through
an assembly step of assembling the ultrasound motor 10 and/or any
other step.
[0079] The method of forming the electrodes on the substantially
circular ring shaped piezoelectric body as in the prior art has to
provide a predetermined interval between the electrodes in order to
prevent discharge at the time of polarization processing of the
piezoelectric body. Accordingly, between the electrodes of the
piezoelectric body, there is a base material portion of the
piezoelectric body, in which no electrode is formed. This base
material portion of the piezoelectric body has no electrode formed,
and thereby remains unpolarized even if the polarization processing
is carried out.
[0080] For this reason, there has been the problem that when
providing a driving signal for driving an ultrasound motor to each
electrode, the piezoelectric body in the area in which the
electrode is formed expands and contracts in dependence upon the
driving signal but the base material portion of the piezoelectric
body does not expand and contract and accordingly there is no
contribution to the excitation of the elastic body, and there is a
base material portion of the piezoelectric body between the
electrodes, so that the expansion and contraction of the
piezoelectric body in the area in which the electrode is formed are
inhibited, interfering with excitation of the elastic body, thereby
introducing a cause of a reduction in driving efficiency of the
ultrasound motor.
[0081] In contrast to this, according to the present embodiment, a
plurality of the piezoelectric bodies 13 are formed for areas
corresponding to the electrodes 131 on an area-by-area basis, so
that there is no area of the piezoelectric body which remains
unpolarized between the electrodes 131, and this avoids the
inhibition of the expansion and contraction of the piezoelectric
body 13 in an area in which the electrode 131 is formed, thereby
making it possible to expect an improvement of the driving
efficiency of the ultrasound motor 10.
[0082] Furthermore, in the method of forming the electrodes on a
substantially circular ring shaped piezoelectric body as in the
prior art, if the polarization processing is performed one-by-one
for each of the electrodes in order to prevent discharge at the
time of the polarization process, then a piezoelectric body in one
of the areas in which the electrode is formed expands and the
piezoelectric body in the other area contracts, and the base
material portion of the piezoelectric body between the electrodes
in which the electrode is not formed is not deformed, so that the
piezoelectric body which has been subjected to the polarization
process is deformed and takes an awkward shape.
[0083] For this reason, it has been necessary to carry out the
polarization simultaneously for a plurality of electrodes formed on
the piezoelectric body, and for the simultaneous polarization for
the plurality of electrodes, it has been necessary to provide a
predetermined interval between the adjacent electrodes in order to
prevent discharge. The interval (corresponding to W in FIG. 3A)
between the adjacent electrodes provided for this prevention of
discharge was between 0.4 and 0.5 mm.
[0084] According to the present embodiment, however, the
piezoelectric body 13 is independently formed for each electrode
131, so that it cannot be deformed even if the polarization process
is carried out for each electrode 131. Therefore, according to the
present embodiment, it is not required to polarize all the
electrodes simultaneously, thereby making it possible to reduce the
interval between the adjacent electrodes.
[0085] According to the present embodiment, since the interval
between the adjacent electrodes 131 (piezoelectric bodies 13) is
set to W=0.05 mm, the total area of the electrodes 131 accordingly
increases by about 6% and the area of the piezoelectric bodies 13
contributing to the excitation of the elastic body 12
increases.
[0086] As a result, the effect of exciting the elastic body 12 is
enhanced, and an improvement of the driving efficiency of the
ultrasound motor can be expected.
[0087] It should be noted that, from the standpoint that discharge
is to be prevented during the polarization, the present embodiment
is intended to perform the polarization processing in such a manner
that the piezoelectric bodies 13 that are adjacent to each other
and polarize for different polarities (polarization directions) are
polarized separately for each polarity.
[0088] Moreover, in the manufacturing method of bonding the
piezoelectric body and the elastic body using an adhesive as in the
prior art, the piezoelectric body 13 requires the steps of washing
and drying of components, applying an adhesive, securing by a
securing jig, thermally curing, removing the securing jig and so
on, as well as several controls during the steps, including the
amount of adhesive applied, the temperature of the adhesive, the
amount of pressurization, the pressurization time, the curing
temperature, the curing time and so on.
[0089] According to the present embodiment, however, the
piezoelectric body 13 is made integrally with the elastic body 12
by the injection molding step S300 that is one of the manufacturing
steps for the piezoelectric body 13, and their complete bonding can
be accomplished by the sintering step without using an adhesive or
the like, so that the number of process steps is reduced and
various kinds of controls as described above can be eliminated,
thereby making it possible to easily perform the manufacture of the
vibration body 11 and consequently the manufacture of the
ultrasound motor 10.
[0090] In addition, a vibration body in which the piezoelectric
body and the elastic body are bonded with an adhesive as in the
prior art has led to problems in that the vibrations are attenuated
by the presence of the layer of adhesive between the piezoelectric
body and the elastic body, and in that to ensure sufficient
adhesive strength, the material of the adhesive must be selected, a
process must be carried out to roughen a surface of the elastic
body to which the piezoelectric body is bonded, and/or other
requirements had to be met.
[0091] However, according to the present embodiment, the
piezoelectric body 13 and the elastic body 12 are directly bonded
and thus there is nothing interfering with the transfer of
vibrations between the piezoelectric body 13 and the elastic body
12, so that the elastic body 12 can be excited efficiently.
Besides, according to the present embodiment, the piezoelectric
body 13 is bonded to the elastic body 12 by sintering, so that the
piezoelectric body 13 and the elastic body 12 can be easily bonded
in an integrated fashion with sufficient bonding strength.
[0092] Furthermore, if the piezoelectric body 13 as in the present
embodiment is to be formed by means of cutting a substantially
circular ring shaped piezoelectric body in a predetermined shape or
by other means, such processing as cutting or the like is difficult
because the piezoelectric body 13 has a brittle nature.
[0093] On the contrary, according to the present embodiment, it is
possible to manufacture the piezoelectric body 13 easily.
(Modification)
[0094] (1) The piezoelectric body forming mold 13A in the present
embodiment has cavity sections completely separated in a plurality
of areas, based on a situation where the partitions 13B are in
contact with the elastic body 12 when the mold 13A is placed
opposite to the elastic body 12. The foregoing has been given by
way of an example for which a plurality of separate piezoelectric
bodies 13 are independently formed on the respective separate
areas, by injecting and molding a material of the piezoelectric
body into the separate areas, respectively.
[0095] However, the piezoelectric body may be formed in the
following manner. For example, the height of the partition may be
decreased to form a clearance between the surface of the elastic
body and the partition when the piezoelectric body forming mold is
brought into contact with the elastic body. In the piezoelectric
body formed in this manner, the adjacent piezoelectric bodies are
not completely separated, but they are continuous on the elastic
body side and become one piezoelectric body essentially separated
into a plurality of regions by a groove. In this way, the mixture
can flow into the other regions from the clearance when injecting
the mixture. Therefore, it is possible to inject the mixture into
the whole cavity portion, for example even if the injection outlet
is at a single location, and thus the injection can be carried out
easily and uniformly.
[0096] (2) Moreover, it is possible that no partition to the
piezoelectric body forming mold is provided. In this case, the
piezoelectric body forming mold is formed to have a cavity section
taking the shape of a circular ring without any partition. The
piezoelectric body is divided into a plurality of regions by
injecting the mixture into the cavity section and radially trimming
parts of the circular ring shaped piezoelectric body formed on the
elastic body.
[0097] (3) In the present embodiment, the piezoelectric body 13 was
molded by placing the piezoelectric body forming mold 13A on the
elastic body forming mold 12A in opposition to the mold 12A and by
injecting the mixture therein. However, the piezoelectric body may
be manufactured differently from the elastic body, and may adhere
to the elastic body. In this case, the piezoelectric body may be
manufactured solely by injection molding, or may be manufactured by
stamping it out with a die from a sheet-formed material.
Furthermore, the piezoelectric body may be manufactured by slicing
a cylindrical body.
[0098] Alternatively, the piezoelectric body manufactured in these
ways may be in a circular ring shape, and may have a shape obtained
by dividing the circular ring into a plurality of segments.
[0099] In the case of the circular ring shaped piezoelectric body,
the piezoelectric body may adhere to the elastic body and then the
piezoelectric body may be divided into a plurality of areas by
trimming parts of the piezoelectric body in a radial line
formation. In this case, positioning for bonding the piezoelectric
body on the elastic body is easy.
[0100] Alternatively in the case of a piezoelectric body in which
the circular ring is divided into a plurality of segments, the
piezoelectric body is made to adhere to the elastic body in such a
manner that the piezoelectric body becomes a substantially circular
ring shaped as a whole. In this case, it is possible to omit
efforts to trim the piezoelectric body to divide it.
[0101] (4) Although the description in the present embodiment has
been made by way of an example in which the electrode 131 is not
formed on both ends of the piezoelectric body 13 in the radial
direction of the elastic body 12, the present invention is not
limited to this, and for instance the electrode 131 may be formed
over the whole area of the piezoelectric body 13. In this case, it
is preferable to provide a solution for preventing discharge during
the polarization process.
[0102] (5) The description in the present embodiment has been given
by way of an example in which a rotational type ultrasound motor 10
whose movable body 14 is rotationally driven is used as a vibration
actuator, but the invention is not limited to this and the actuator
may be a linear type ultrasound motor. Alternatively, the actuator
may be an actuator of a rod type, pencil type, disc type or the
like.
[0103] (6) In the present embodiment, the description has been
given by way of an example in which the ultrasound motor 10 is used
as a vibration actuator, but the invention is not limited to this,
and for example the actuator may be a vibration actuator utilizing
any vibration other than that in an ultrasonic range.
[0104] (7) In the present embodiment, the description has been
given by way of an example of use of the ultrasound motor 10 as a
driving source for the auto focusing of the camera 1, but the
invention is not limited to this, and for example the motor 10 can
be applied to a driving source for the zoom operation of a camera,
a driving source for a blur-correcting mechanism for correcting
blurring caused by the hand of the photographer by driving a part
of an image pickup system of a camera, a driving section for a copy
machine, a steering wheel tilting apparatus for an automobile, a
driving device for a clock/watch and so on.
[0105] It should be noted that the present embodiment and the
modifications can be used in various combinations as appropriate,
but the details of such combinations are omitted from the
description.
* * * * *