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DESCRIPTION JPH09327655

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DESCRIPTION JPH09327655
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
vibrator using a piezoelectric element.
[0002]
2. Description of the Related Art For example, as a built-in vibrator for calling a portable
telephone or pager, a structure in which an eccentric load is provided on the rotation shaft of a
small motor has been used conventionally, and vibration is caused by rotating this motor. You
are getting However, when an electromagnetic motor is used, it is difficult to miniaturize due to
its complicated structure, and there is a limit to the reduction of power consumption.
[0003]
Then, although the thing using a piezoelectric material is devised for the purpose of size
reduction and power consumption reduction, it is still developing. The following actuators are
proposed as an actuator using a piezoelectric material.
[0004]
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Japanese Patent Application Laid-Open No. 62-204885 discloses a vibration-type actuator in
which a piezoelectric bimorph is applied to a polishing mechanism (FIG. 8). The piezoelectric
vibrator 81 is formed by bonding two piezoelectric films 82, 82 having different displacement
directions when a voltage is applied, and forming electrode films 83, 84, 84 on the bonding
surface and both outer surfaces. It is a laminated type. One end side of the piezoelectric vibrator
81 is supported by the support portion 85, and the other end side is provided with an actuator
attachment portion 87 for detachably attaching the actuator 86. A lead wire 88 is connected to
the electrode film 83, and a lead wire 89 is connected to the electrode films 84 and 84.
[0005]
When an AC voltage is applied between the two electrode films 83 and 84 through the lead wires
88 and 89, the piezoelectric vibrator 81 vibrates due to the bending displacement of the
piezoelectric films 82 and 82, whereby the actuator 86 is swung.
[0006]
Further, Japanese Patent Laid-Open No. 3-9581 discloses an actuator having a function of setting
the initial position of the displacement element to a fixed level.
As shown in FIG. 9, the displacement element 21 of this actuator is overlapped with the metal
elastic plate 23 sandwiched between two piezoelectric ceramics 22, 22, and further, the metal
elasticity is applied to both outer side surfaces of the piezoelectric ceramics 22, 22. It comprises
the boards 24, 24. One end of the displacement element 21 is fixed by a fixing member 25 and
the other end is a free end, and a weight 26 which is a static load is attached. The metal elastic
plates 23, 24, 24 are connected to the power supply at the fixed end.
[0007]
When a predetermined voltage is applied to the displacement element 21, the free end is
displaced in the direction indicated by the white arrow. Thereafter, when the applied voltage is
set to 0 V, the free end of the displacement element 21 is returned to the initial position by its
displacement return force and the load of the weight 26. Therefore, with this actuator, a highly
accurate displacement can be obtained. Here, the weight, size and shape of the weight 26 are set
in consideration of the displacement force and bending strength of the displacement element 21
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or the positional relationship between the displacement element 21 and the base material.
[0008]
Thus, it is known that a bimorph actuator has a weak force but a simple structure and a large
displacement can be obtained. When a DC electric field is applied, a displacement in one
direction is obtained, and when an AC electric field is applied, it is known The force generated by
the displacement of is transmitted to the fixed end as a reaction force to obtain vibration.
Although the bimorph actuator uses two piezoelectric plates, the vibration effect can be obtained
even with a unimorph actuator using one piezoelectric plate.
[0009]
When a bimorph actuator is applied to a vibrator, a force generated by vibration is used, which is
represented by the product of the bimorph mass and the acceleration of the vibration, and the tip
of the free end Is the largest at However, there is a problem that the force that can be generated
by the conventional bimorph actuator is insufficient as a vibrator. In addition, when the vibrator
is used in a portable device, sufficient resistance to impact such as falling is required.
[0010]
The present invention has been made in view of such circumstances, and by providing a cover
that covers the moving area at the time of driving of the weight attached to the free end of the
piezoelectric element, resistance to impact such as falling can be achieved. An object of the
present invention is to provide a vibrator that can obtain an excellent and sufficient generation
force.
[0011]
[Means for Solving the Problems] In order to exhibit the function as a practical vibrator in
general, a configuration in which a load is applied to the tip is considered, and a load that is up to
several tens times the mass of the bimorph itself is applied. There is a need.
However, when a load is applied to the front end, the weight attached to the free end of the
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piezoelectric element largely swings when an impact such as a drop is applied, so that the
piezoelectric element may be largely displaced and broken.
[0012]
Therefore, in the vibrator according to the first aspect of the present invention, an alternating
electric field is applied to the piezoelectric element held at one end by the holding member to
vibrate, the weight added to the free end of the piezoelectric element and the weight at the time
of driving And a covering fixed to the holding member covering an existing area.
[0013]
For example, when a large impact such as a drop is applied, the piezoelectric element is displaced
more than in normal vibration, and this displacement amount is larger by applying a load to the
tip, but by providing a covering The amount of displacement at this time can be limited.
As a result, damage to the piezoelectric element or deterioration in durability can be avoided.
[0014]
The invention according to claim 2 is characterized in that, in claim 1, a buffer layer is formed on
the inner surface of the cover.
[0015]
When a large impact is applied and the piezoelectric element is displaced more than in normal
vibration, depending on the size of the cover, the weight may collide with the cover and an
impact may be applied to the piezoelectric element.
However, since the buffer layer absorbs the impact at this time, the impact received by the
piezoelectric element can be alleviated, and the impact resistance is improved.
[0016]
The invention according to claim 3 is characterized in that, in claim 1 or 2, the covering has a
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size capable of covering an area larger than the moving area of the weight at the time of driving.
[0017]
It is possible to prevent the piezoelectric element from being broken or the weight from falling
off due to an impact caused by the weight coming into contact with the cover during normal
vibration.
[0018]
DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically
described below based on the drawings showing the embodiments thereof.
FIG. 1 is a longitudinal sectional view showing a vibrator according to the present invention.
Two rectangular displacement elements 1 and 1 are attached to each other, and one end side in
the longitudinal direction is held by the holding member 4. A substantially rectangular
parallelepiped weight 2 is bonded to both surfaces of the other end of the displacement element
1 at the other end. The weight 2 has a step in the central portion in the length direction on the
surface facing the displacement element 1 and has a thickness of two steps. Thus, a gap 3 is
provided between the half of the weight 2 on the holding member 4 side and the displacement
element 1. The displacement element 1, the weight 2 and the holding member 4 are covered and
protected by a rectangular cylindrical covering 6. Furthermore, the displacement elements 1, 1
are connected to the AC power supply 5 at the end on the holding member 4 side. FIG. 2 is a
perspective view showing a state in which the covering 6 is removed.
[0019]
FIG. 3 is an enlarged sectional view showing the bonded portion A of the displacement element 1.
The displacement element 1 has electrodes 12 and 12 formed on both sides of a piezoelectric
ceramic 11, and two displacement elements 1 and 1 are attached to each other with a metal plate
13 interposed therebetween.
[0020]
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The vibrator according to the present invention can be produced as follows. [Example 1] A
piezoelectric material containing lead zirconate titanate as a main component is sintered,
processed into a thin plate (piezoelectric ceramic 11) with a width of 10 mm, a length of 20 mm,
and a thickness of 200 μm, and gold plated on both sides to make an electrode 10 μm thick 12,
12 are formed and two polarized displacement elements 1 are produced. These two displacement
elements 1 are pasted on both sides of a brass metal plate 13 with a width of 10 mm, a length of
25 mm and a thickness of 50 μm using an adhesive so that the polarization directions become
the same. Match. Then, the exposed electrodes 12 of the piezoelectric ceramic 11 are electrically
connected to the alternating current power supply 5 respectively, and driving power can be
supplied between the exposed electrodes 12 and the metal plate 13 made of brass to produce a
bimorph. The exposed end of the metal plate 13 is held by the holding member 4 from both
sides.
[0021]
On the other hand, in order to make the weight 2, prepare two lead rectangular parallelepipeds
of width 10 mm, length 10 mm, thickness 1.5 mm, and make each half of the length direction on
one side have a thickness of 1.0 mm. Cutting into Then, an adhesive is applied to the one side of
the half portion having a thickness of 1.5 mm, and adhesive fixing is performed so that the thin
portion is on the holding member 4 side on the free end side of the bimorph which is not held by
the holding member 4 Do.
[0022]
Next, a stainless steel covering 6 in the form of a square tube having a width of 12 mm, a length
of 30 mm and a height of 6 mm is formed, and an adhesive is used inside one opening to bond
the bimorph holding member 4 Fix it. In addition, although a piezoelectric material such as lead
zirconate titanate is generally used for the bimorph, it is not limited thereto. Further, for the
weight 2, a material having a large specific gravity is appropriate in order to reduce the volume.
Further, the fixation between the bimorph and the weight 2 may be performed by screwing, but it
is preferable to use adhesion which does not require machining.
[0023]
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Embodiment 2 FIG. 4 is a longitudinal sectional view showing a vibrator of Embodiment 2. FIG.
The vibrator of Example 2 is manufactured as follows. That is, the weight 2 is attached to the
same bimorph as in the first embodiment and held by the holding member 4. On the other hand,
a polyurethane resin having a thickness of 0.5 mm is coated on the inner surface of the cover 6
at a position corresponding to the periphery of the weight 2 to form the buffer layer 7. The
member 4 is adhesively fixed. The material of the buffer layer 6 is not limited to polyurethane
resin.
[0024]
A drop test and a continuous drive test were conducted to evaluate the impact resistance and
durability of the vibrator in Examples 1 and 2, and the results were compared with the results in
Comparative Examples 1 and 2. Three vibrators of Examples 1 and 2 and Comparative Examples
1 and 2 were prepared for two types of drop test and continuous drive test.
[0025]
The drop test measures the generated force again after dropping the vibrator after measuring the
generated force in the longitudinal direction, the width direction and the thickness direction
twice from the height of 2M and 4M to the concrete floor surface did. And it decomposed |
disassembled and investigated the presence or absence of the crack of the displacement element
1 (piezoelectric ceramic 11) which consists of ceramics. In the continuous drive test, an
alternating current electric field of 100 V was applied in a 20 ° C. atmosphere to the vibrator
after measuring the generated force in advance, and it was continuously driven for 10 hours, and
then the generated force was measured again to investigate the output change. . Moreover, the
presence or absence of the crack of the displacement element 1 (piezoelectric ceramic 11) which
was decomposed | disassembled and consists of ceramics was investigated. The power
generation was determined as follows. That is, a measuring weight of 100 g and a bimorph are
placed on a spring balance to form a resonant system, an alternating electric field of up to 100 V
is applied to the bimorph to resonate, and the maximum acceleration is measured by an
accelerometer installed on the balance. And it calculated | required from the product of this
measurement result and the load for measurement.
[0026]
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The vibrator of Comparative Example 1 uses the same bimorph as in Examples 1 and 2 as shown
in FIG. 5 and does not have the cover 6 attached. Then, at the time of measurement, it was placed
by floating 3 mm on the balance by placing the metal holding member only on the fixed end
portion. In the vibrator of Comparative Example 2, as shown in FIG. 6, the same bimorph as in
Examples 1 and 2 is adhered and fixed to the inside of a stainless steel covering 8 having a width
of 12 mm, a length of 30 mm and a height of 4 mm. is there. The buffer layer 7 is formed on the
inner surface of the cover 8 as in the second embodiment.
[0027]
In the first and second embodiments, the tip of the weight 2 was not in contact with the cover 6
and the buffer layer 7 during driving, but in the second comparative example, the buffer layer 7
had the tip of the weight 2 formed on the inner surface of the cover 8. It was in contact with FIG.
7 is a longitudinal sectional view showing a state in which the weight 2 is in contact with the
cover.
[0028]
Table 1 shows the results of the 2M drop test in the above Examples 1 and 2 and Comparative
Examples 1 and 2. As is apparent from Table 1, although the breakage due to the 2M drop test
was not confirmed in Examples 1 and 2 and Comparative Example 2, in Comparative Example 1,
a transverse crack was confirmed at the fixed end because it was not protected by the cover. The
It is considered that this is because the load was concentrated near the fixed end when it was
dropped. The generated force after the test was almost the same as before the test in Examples 1
and 2 and Comparative Example 2, but in Comparative Example 1, it was significantly reduced
due to breakage. Further, in Comparative Example 2, the output is large before and after the test,
which is considered to be because the weight 2 collides with the cover 8 at the time of driving.
[0029]
Table 2 shows the results of the 4M drop test. As is clear from Table 2, as a result of the 4M drop
test, in Example 1 and Comparative Example 1, a transverse crack was confirmed at the fixed
end, and in Comparative Example 2, a transverse crack was confirmed at the central portion. Was
not confirmed. It is considered that this is because the impact at the time of the fall was mitigated
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by the buffer layer 7. The generation after the test was significantly reduced in Examples 1 and
Comparative Examples 1 and 2 in which breakage was observed, but was hardly changed in
Example 2 in which no breakage was observed.
[0030]
Table 3 shows the results of the continuous drive test. As a result of the continuous driving test,
no breakage was confirmed in Examples 1 and 2 and Comparative Example 1, but in Comparative
Example 2, a transverse crack occurred at the fixed end. It is considered that the impact when the
weight 2 comes in contact with the cover 8 is also propagated to the displacement element 1
(piezoelectric ceramic 11) made of ceramics, and this repetition leads to breakage. Therefore, in
Comparative Example 2, the output after continuous driving was significantly reduced.
[0031]
When the vibrator according to the present invention is applied to a pager or other portable
device, it can be practically used with a structure that can withstand the 2M drop test in
consideration of human extension.
[0032]
The present invention is not limited to a bimorph using two piezoelectric ceramics, and for
example, a unimorph may be used.
However, it goes without saying that greater generation power can be obtained when using a
bimorph.
[0033]
As described above, the vibrator according to the present invention has a covering around the
weight attached to the free end of the piezoelectric element, so that the vibrator has good
resistance to impact such as falling. In the case where a buffer layer is formed on the inner
surface of the cover, for example, the impact resistance to the piezoelectric element applied at
the time of dropping is alleviated, so that the impact resistance is further improved. In the case
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where the covering has such a size as to cover an area larger than the moving area of the weight
at the time of driving, the present invention has excellent effects such as a decrease in durability
can be avoided.
[0034]
Brief description of the drawings
[0035]
1 is a longitudinal sectional view showing a vibrator according to the present invention.
[0036]
2 is a perspective view showing the vibrator with the cover removed.
[0037]
3 is an enlarged sectional view showing the bonded portion of the two displacement elements of
FIG.
[0038]
4 is a longitudinal sectional view showing another vibrator according to the present invention.
[0039]
5 is a longitudinal sectional view showing a vibrator of Comparative Example 1.
[0040]
6 is a longitudinal sectional view showing a vibrator of Comparative Example 2.
[0041]
7 is a longitudinal sectional view showing a state where the weight is in contact with the cover.
[0042]
8 is a cross-sectional view showing a conventional example (actuator for polishing machine)
using the bimorph.
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[0043]
9 is a side view showing another conventional example (actuator) using the bimorph.
[0044]
Explanation of sign
[0045]
Reference Signs List 1 displacement element 2 weight 4 holding member 5 AC power supply 6
cover 7 buffer layer 11 piezoelectric ceramic
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