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DESCRIPTION JP2009207056

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DESCRIPTION JP2009207056
PROBLEM TO BE SOLVED: To reduce the length of the entire device in the direction of the output
surface of the output unit, and protect the piezoelectric element even if pressure due to a large
impact such as a drop impact is applied to the output unit, and the output is not easily reduced.
Providing a vibration generator. SOLUTION: A laminated piezoelectric element 2 and an
enlargement mechanism part for enlarging a displacement due to mechanical vibration generated
by the laminated piezoelectric element 2 and a vibration output part and a base part for
transmitting the enlarged mechanical vibration to the outside There is. The magnifying
mechanism portion is bent in a direction substantially orthogonal to the magnifying lever driving
portion 12 to which the mechanical vibration of the laminated piezoelectric element 2 is
transmitted, and the magnifying lever driving portion 12, and is formed integrally with the
magnifying lever driving portion 12 The lever is substantially L-shaped and includes an enlarged
lever output portion 11 for transmitting mechanical vibration, and the enlarged lever 10 has a
pin 13 on the base 5 of the base portion so that the enlarged lever 10 can be pivoted. It is
supported by [Selected figure] Figure 2
Vibration generator
[0001]
The present invention uses a piezoelectric element used in applications such as bone conduction
speakers that convert a sound electrical signal into acoustic vibration and transmit it to a part of
the human head and this sound is transmitted to an auditory organ to recognize a sound. In
particular, the present invention relates to a vibration generating device having a low profile and
protecting a piezoelectric element from a large impact force such as a drop impact.
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[0002]
As a voice or music interface such as a handset of a mobile phone or fixed telephone, and a
headphone, the voice electric signal is converted into an acoustic vibration and transmitted to a
part of the human head, and this vibration is transmitted to the auditory organ. A bone
conduction speaker is used to make the user recognize the sound.
[0003]
When a bone conduction speaker is used for a portable telephone, a portable terminal device or
the like, the acoustic signal generating device is required to be as compact as possible and to
have a high output.
For this reason, it is preferable that a larger output can be obtained with a simpler structure for
the applied signal.
Usually, as an acoustic signal generator using a piezoelectric element, a piezoelectric unimorph
element or a piezoelectric bimorph element is mainly used. In the case of these piezoelectric
elements, in order to obtain acoustic vibration of a required magnitude, it is necessary to
correspond to the amount of displacement of mechanical vibration, and for this purpose, it is
necessary to increase the shape of the piezoelectric elements to a certain extent or more. There is
a limit to the size reduction to maintain the required acoustic output.
[0004]
Therefore, as a device suitable for this purpose, Patent Document 1 discloses an acoustic signal
generator having a displacement magnifying mechanism with a substantially U-shaped structure.
It consists of a laminated piezoelectric element that mechanically vibrates due to expansion and
contraction displacement in response to an applied electrical signal, and an enlargement
mechanism section that enlarges the displacement of the lamination type piezoelectric element,
and the enlargement mechanism section is a substantially U-shaped enlargement A laminated
piezoelectric element is disposed between opposing upper and lower sides of a U shape having a
lever, and the end portions on the open end side of the U open each other by the expansion and
contraction displacement of the laminated piezoelectric element in the lamination direction Thus,
the relative displacement on the tip side is made larger than the displacement of the laminated
piezoelectric element.
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[0005]
However, in order to further miniaturize the acoustic signal generating apparatus, if the height is
to be made smaller, it is necessary to make the length of the laminated piezoelectric element
smaller, in which case the obtained displacement output is reduced Can not achieve the goal of
obtaining a larger output with a simpler structure for the signal being processed.
[0006]
Therefore, the inventors of the present invention invented the acoustic signal generator having a
displacement magnifying mechanism that does not reduce the output even if the length of the
device in the direction of the output surface, that is, the height of the entire device, is reduced.
The structure of the acoustic signal generator for which the prior patent application was filed is
shown in FIGS. 4 and 5. FIG.
FIG. 4 is a perspective view of the acoustic signal generator developed into parts, and FIG. 5 is a
cross-sectional view of the acoustic signal generator taken along the central portion thereof.
[0007]
In FIG. 5, the acoustic signal generating device includes a laminated piezoelectric element 2 for
converting a vibrational change of an electric signal into mechanical vibration, and an expanding
mechanism portion for enlarging displacement due to mechanical vibration generated by the
laminated piezoelectric element 2; And an output unit for outputting mechanical vibration due to
the displacement expanded by the enlargement mechanism unit. Further, the direction of the
output surface for transmitting the mechanical vibration in the output section to the outside is
substantially orthogonal to the expansion / contraction displacement direction of the multilayer
piezoelectric element 2.
[0008]
In addition, the enlargement mechanism portion is formed integrally with the enlargement lever
drive portion 22 and the enlargement lever drive portion 22 by bending in the direction
substantially orthogonal to the enlargement lever drive portion 22 respectively. An
approximately U-shaped enlarged lever 20 including an output portion 21 is configured, and
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mechanical vibration is transmitted from one end of the laminated piezoelectric element 2 to the
enlarged lever driving portion 22.
[0009]
In addition, it has a fixed portion formed by fixing a weight 16 having the other end of the
laminated piezoelectric element 2 fixed by the preload screw 24 to the enlarged lever base
portion 15 by the fixed screw 17, and the enlarged lever drive portion 22 and the enlarged lever
base portion The displacement is enlarged with the bending portion 18 between 15 and 15 as
the rotation center.
The output unit is comprised of an output pad 19 fixed to the enlarged lever output unit 21 for
transmitting mechanical vibration to the outside.
[0010]
JP 2007-74663 A
[0011]
In the acoustic signal generator having the displacement magnifying mechanism of the above
structure, the magnifying lever 20 shown in FIG. 4 is formed integrally with the magnifying lever
drive portion 22, the magnifying lever base portion 15 and the magnifying lever output portion
21, When a large impact force due to a drop or the like is applied to the expansion lever output
portion 21 as a pressure in a direction parallel to the output vibration direction (E shown in FIG.
4), a load is applied in the direction in which the expansion lever drive portion 22 compresses
the laminated piezoelectric element 2 It takes
Here, the laminated piezoelectric element 2 is compressed by an external force or generates an
counter electromotive force when an impact is applied, and the polarization performance is
degraded. Therefore, in this acoustic signal generator, the amplitude level of the vibration output
is increased by receiving an impact. There is a problem that it falls. The force in the direction
orthogonal to the output vibration direction (the G and H directions shown in FIG. 4) is dealt with
so as to ease it even if it receives an impact. For example, the gap between the output unit and
the exterior of the device may be increased so that an impact does not easily act on the output
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unit. As a result, even if it receives an impact, the reduction of the output level is within the
allowable range.
[0012]
However, in a device such as a bone conduction speaker in which the device is brought into
contact with an external transmission object and the vibration output is transmitted to the
outside, the vibration output part is transmitted to the human body as an essential form. It must
be exposed to the outside. Therefore, it is also inevitable to receive an impact of the pressure in
the vibration direction of the output part (direction E shown in FIG. 4) which is most likely to
cause an output reduction due to the impact. This is an important issue to be addressed in order
to improve the performance of a vibration generating device such as a bone conduction speaker.
[0013]
Therefore, the object of the present invention is to reduce the overall length of the device in the
direction of the output surface for transmitting the mechanical vibration of the output unit to the
outside, and to be parallel to the vibration direction of the output unit due to a large impact such
as a drop impact. It is an object of the present invention to provide a vibration generating device
having a structure which protects the piezoelectric element even if pressure in any direction is
applied to the output part and which is less likely to cause the output reduction.
[0014]
In order to achieve the above object, a vibration device according to the present invention
includes a piezoelectric element that converts a vibrational change of an electric signal into
mechanical vibration, an enlargement mechanism unit that enlarges displacement due to
mechanical vibration generated by the piezoelectric element, and the enlargement. The
mechanical unit includes a vibration output unit for transmitting mechanical vibration due to an
enlarged displacement to the outside, and a base unit that holds the piezoelectric element and the
magnifying mechanism unit, and the magnifying mechanism unit transmits the mechanical
vibration of the piezoelectric element And an enlarged lever output portion which is bent in a
direction substantially orthogonal to the enlarged lever drive portion and integrally formed with
the enlarged lever drive portion to transmit the mechanical vibration to the vibration output
portion. A vibration generating device comprising a substantially L-shaped magnifying lever as a
component, wherein the magnifying lever is supported by a pin on the base portion so that the
magnifying lever pivots, the magnifying lever The vibration direction of the force portion is
substantially orthogonal to the vibration direction of the piezoelectric element, and when
pressure parallel to the vibration direction is applied to the vibration output portion, the
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piezoelectric element and the magnifying lever drive portion are separated The expanding lever
may be arranged to pivot.
[0015]
Further, it is preferable that a means for applying an appropriate pressure between the
piezoelectric element and the magnifying lever driving unit is provided in order to appropriately
transmit the mechanical vibration of the piezoelectric element to the magnifying lever driving
unit.
For this reason, means for giving an elastic force in a direction to widen the gap may be inserted
between the base portion and the enlarged lever output portion, and the means for giving the
elastic force may be a plate spring.
[0016]
The acoustic signal generator shown in FIGS. 4 and 5 has a U-shaped magnifying lever in which
the magnifying lever drive portion 22, the magnifying lever base portion 15, and the magnifying
lever output portion 21 are integrally formed as a magnifying mechanism. However, in the
present invention, it has a substantially L-shaped magnifying lever integrally formed with the
magnifying lever drive portion and the magnifying lever output portion as the magnifying
mechanism portion, and the base portion supporting the magnifying lever as another component.
have.
Further, the expansion lever is structured so that the expansion lever is supported by a pin on the
base portion, and the vibration direction of the expansion lever output portion is disposed
substantially orthogonal to the vibration direction of the piezoelectric element. In the present
invention, with this structure, the height of the entire device can be reduced, and when pressure
in the same direction as the vibration direction is applied to the vibration output portion, the
magnifying lever pivots in the direction of separating the magnifying lever driving portion and
the piezoelectric element.
[0017]
From the above, according to the present invention, the overall length of the device in the
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direction of the output surface for transmitting the mechanical vibration of the output unit to the
outside is reduced, and parallel to the vibration direction of the output unit due to a large impact
such as a drop impact. Even when pressure in the direction is applied to the output portion, the
piezoelectric element is protected, and a vibration generating device having a structure in which
the output is not easily reduced can be obtained.
[0018]
Hereinafter, embodiments will be described based on examples of the present invention with
reference to the drawings.
[0019]
1 to 3 are views showing a vibration generating device for a bone conduction speaker which is
an embodiment of a vibration generating device according to the present invention.
FIG. 1 is an external view, FIG. 2 is a cross-sectional view taken along the line A-A of FIG. 1, and
FIG. 3 is an exploded perspective view of parts.
The present embodiment will be described using these figures.
[0020]
In FIG. 2 and FIG. 3, the vibration generating apparatus of this embodiment enlarges the
displacement due to the mechanical vibration generated by the laminated piezoelectric element 2
for converting the vibrational change of the electric signal to the mechanical vibration and the
laminated piezoelectric element 2 It comprises an enlargement mechanism portion, a vibration
output portion for transmitting mechanical vibration due to an enlarged displacement of the
enlargement mechanism portion to the outside as acoustic vibration, and a base portion for
supporting the laminated piezoelectric element 2 and the enlargement mechanism portion. The
magnifying mechanism portion is bent in a direction substantially orthogonal to the magnifying
lever driving portion 12 to which the mechanical vibration of the laminated piezoelectric element
2 is transmitted, and the magnifying lever driving portion 12, and is formed integrally with the
magnifying lever driving portion 12 And an enlarged lever output portion 11 for transmitting a
mechanical vibration to the substantially L-shaped enlarged lever 10. The base portion is a
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substantially U-shaped base 5, a weight 9, and an element receiving portion formed of a base side
portion 7 and a pin hole 5a which are integrally formed by bending the base portion 6 and the
base portion 6 substantially at right angles. It is comprised by board 4 grade. Further, the
magnifying lever 10 is supported by a pin 13 on the base 5 so that the magnifying lever 10
pivots.
[0021]
Further, the magnifying lever 10 is disposed such that the vibration direction of the magnifying
lever output portion 11 is substantially orthogonal to the vibration direction due to the
expansion and contraction displacement of the laminated piezoelectric element 2, and the
vibrating direction of the magnifying lever output portion 11 to the magnifying lever output
portion 11 When the parallel pressure is applied, the magnifying lever 10 is configured to pivot
in the direction in which the laminated piezoelectric element 2 and the magnifying lever drive
unit 12 are separated. The vibration output unit for transmitting the mechanical vibration due to
the displacement of the enlargement mechanism unit to the outside as the acoustic vibration is
fixed to the magnifying lever output unit 11 from the output pad 1 having the output surface for
transmitting the mechanical vibration to the outside It is configured.
[0022]
The multilayer piezoelectric element 2 is a piezoelectric element formed by alternately
laminating a sheet-like piezoelectric material and an electrode material having a thickness of
several tens to several hundreds of micrometers and connecting each of a plus electrode and a
minus electrode. A feature is that the expansion and contraction displacement in the stacking
direction is expanded and increased by the number of stacked layers.
[0023]
The base 5 is formed by pressing a metal plate, and has a substantially U-shape including a base
base 6 and base side portions 7 on both sides thereof.
The base side surface portion 7 is provided with a pin hole 5a for supporting the magnifying
lever 10 with a pin 13 and a notch 5c for fixing and positioning the weight 9. The base base 6 is
provided with a fixing hole 5b for fixing and positioning the element receiving plate 4.
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[0024]
The element receiving plate 4 is inserted into the fixing hole 5 b provided in the base 6 from the
lower side in the figure, and is fixed to the base 5 with an adhesive. The element receiving plate 4
is provided with a screw hole 4 b, and has a structure capable of applying an appropriate preload
to the laminated piezoelectric element 2 by the preload screw 14.
[0025]
Positioning plates 3 for preventing positional deviation are disposed at both ends of the
laminated piezoelectric element 2, and the positioning plate 3 and the laminated piezoelectric
element 2 are attached to a weight 9. The weight 9 has a shape that supports the positioning
plate 3 at both ends, and has a shape that covers the laminated piezoelectric element 2. The
weight 9 is fixed to the base 5 with an adhesive agent by fitting the projection 9 a into the
positioning notch 5 c provided on the base side surface 7 while supporting the positioning plate
3 and the laminated piezoelectric element 2.
[0026]
On the upper surface of the element receiving plate 4, a preload spring 8 in the form of a metal
plate is disposed. The preload spring 8 is subjected to bending and both ends thereof push the
enlarged lever output portion 11 from the back side to obtain a tension for applying an
appropriate preload to the laminated piezoelectric element 2. Further, the preload spring 8 has a
role of supporting the rotation of the magnifying lever 10. In the present embodiment, although
the material of the preload spring 8 is phosphor bronze and the thickness is 0.25 mm, it can be
appropriately set according to the necessary preload.
[0027]
The magnifying lever 10 is formed by pressing a metal plate material, and has a substantially Lshaped shape including a magnifying lever driving unit 12 and a magnifying lever output unit
11. The edge of the enlargement lever 10 is formed with a rib shape 10b by drawing to increase
rigidity. Further, the enlargement lever 10 is provided with a pin hole 10 a for supporting the
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enlargement lever 10 on the base 5.
[0028]
After assembling the element receiving plate 4, the positioning plate 3, the laminated
piezoelectric element 2, the weight 9 and the preloading spring 8 to the base 5, the magnifying
lever 10 is covered from above and the pin hole 10 a of the magnifying lever 10 and the base
side portion 7 The pin 13 is passed through the pin hole 5 a to obtain a structure in which the
magnifying lever 10 is supported by the base 5. The enlargement lever drive unit 12 is in contact
with one end surface of the laminated piezoelectric element 2 so as to transmit the mechanical
vibration generated by the laminated piezoelectric element 2.
[0029]
The laminated piezoelectric element 2 injects an adhesive from the screw hole 4b of the element
receiving plate 4 and then clamps the preload screw 14 to apply a predetermined preload, and
then fixes the adhesive by curing the adhesive by heat treatment or the like. Be done. As a result,
the element receiving plate 4, the laminated piezoelectric element 2, the positioning plate 3 and
the weight 9 are simultaneously fixed. In this embodiment, an epoxy-based one-component
adhesive which cures when heated at 70 ° C. for one hour is used. When the preload screw 14
is tightened and a predetermined preload is applied to the laminated piezoelectric element 2, it is
desirable to select the characteristics of the preload spring so that the magnifying lever 10 is
horizontal. As a result, the height of the entire device can be reduced, and a user-friendly device
can be obtained. The electric signal input line 2a of the laminated piezoelectric element 2 passes
through the notch 5d in the base base 6 and is connected to an external drive circuit.
[0030]
The inner surface of the magnifying lever drive unit 12 abuts on the end surface of the laminated
piezoelectric element 2 opposite to the side of the preload screw 14, and transmits mechanical
vibration generated by the laminated piezoelectric element 2. The inner surface of the
enlargement lever drive unit 12 and the end surface of the laminated piezoelectric element 2 are
not bonded, and are configured to be pressed by the applied preload.
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[0031]
In a vibration generator for a bone conduction speaker, the output pad 1 is in contact with the
skin of the head of the user at the time of use to transmit the vibration. Therefore, a material
having a low thermal conductivity, a low specific gravity, and a relatively high rigidity and having
a good touch is required. In the present embodiment, for example, it is formed of ABS resin or the
like. Further, the output pad 1 is fixed to the enlarged lever output portion 11 with an adhesive.
[0032]
In general, in an acoustic signal generator, it is desirable not to emit extra vibration (sound) in a
part other than the output part, and therefore the mass ratio of the fixed part that does not want
to generate the vibration to the movable part that generates and outputs the vibration is It will be
an important indicator. That is, it is desirable that the ratio of the mass of the fixed part to the
movable part is large in the movable part consisting of the enlargement lever 10 and the output
pad 1 and the fixed part consisting of the base 5, the element receiving plate 4, the weight 9 and
the preload screw 14. For this purpose, a weight 9 is provided. In this embodiment, the mass is
designed such that the fixed part is about 4.8 gf, the movable part is about 0.98 gf, and the ratio
of the fixed part to the movable part is about 5: 1.
[0033]
Next, the operation of the vibration generating apparatus of this embodiment will be described.
By applying an alternating voltage corresponding to the acoustic signal from the external electric
signal source to the laminated piezoelectric element 2 through the electric signal input line 2a,
the laminated piezoelectric element 2 is arranged in the laminating direction in response to the
applied signal. Stretch and displace. In the case of the present embodiment, the expansion /
contraction displacement direction is a longitudinal direction parallel to the output surface of the
output pad 1. According to the displacement of the laminated piezoelectric element 2, the
enlargement lever drive portion 12 of the enlargement lever 10 and the element receiving plate
4 are pushed. At this time, the element receiving plate 4 side is fixed to the base 5 and the weight
9, and the displacement of the laminated piezoelectric element 2 pushes the enlargement lever
drive unit 12 because the structure is much larger in rigidity than the enlargement lever 10 side.
The enlargement lever 10 pivots with a portion supported by the pin 13 as a fulcrum. This
displacement displaces the magnifying lever output portion 11 and the output pad 1 formed
thereon, and the user can hear the sound by bringing it into contact with the skin of the head.
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With the portion supported by the pin 13 as the center of rotation, the distance B between the
contact point of the expansion lever drive unit 12 with the laminated piezoelectric element 2 and
the pin 13 is shorter than the distance C between the output pad 1 and the pin 13 With this
structure, the displacement near the center of the output pad can be expanded three to five times
with respect to the amount of expansion and contraction of the multilayer piezoelectric element
2, and a displacement enlargement mechanism can be obtained to obtain a sufficient volume. In
the present embodiment, the distance B is about 2.5 mm, the distance C is about 10 mm, and the
enlargement ratio is four times.
[0034]
The vibration generating apparatus shown in FIGS. 4 and 5 has a structure in which the
laminated piezoelectric element 2 is compressed when an external force in the direction D shown
in FIG. 2, that is, pressure due to falling in a direction parallel to the output vibration direction is
applied. In the structure of this embodiment, when an external force is applied in the D direction,
the magnifying lever 10 is pivoted in the F direction with the fulcrum supported by the pin 13 as
the pivot center, and the magnifying lever driving portion 12 is of the laminated piezoelectric
element 2. Since the multilayer piezoelectric element 2 is not compressed because it is separated
from the end face, it is possible to prevent a decrease in output due to polarization deterioration.
However, the above operation is such that the external force has a magnitude to displace the
preload spring 8, and in the case of a small external force that does not displace the preload
spring 8, naturally, the magnifying lever drive unit 12 is from the laminated piezoelectric
element 2. It does not move away.
[0035]
After pressure parallel to the vibration direction is applied and the magnifying lever drive unit 12
moves away from the end face of the laminated piezoelectric element 2, the magnifying force of
the preload spring 8 causes the magnifying lever 10 to return to its original position. At this time,
the enlargement lever drive unit 12 collides with the laminated piezoelectric element 2, and the
direction is the direction in which the laminated piezoelectric element 2 is compressed. However,
since the pressure due to the restoration is only the pressure by the preload spring 8, the drop
resistance can be sufficiently improved as compared with the case where the external force by
the impact is directly applied in the compression direction.
[0036]
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The element receiving plate 4 is provided with a stopper portion 4a in order to reduce the
compression at the time of restoration, and the displacement of the enlargement lever output
portion 11 when an external force is applied in the D direction It is structured so as not to exceed
the distance between them. Further, since the structure of the present embodiment is a
mechanism for enlarging the displacement of the laminated piezoelectric element 2 and
transmitting it to the enlarged lever output portion 11, the enlargement when the enlarged lever
output portion 11 is displaced by the external force in the above direction The displacement
transmitted to the lever driving unit 12 decreases in inverse proportion to the above-mentioned
enlargement factor. This is also a structure that can improve the drop resistance performance.
[0037]
Incidentally, it goes without saying that the present invention is not limited to the above
embodiments, and design changes can be made arbitrarily, such as selection of the material and
shape of the members according to the purpose and application thereof and required
performance and form. It is. For example, it is possible to use another type of spring instead of a
leaf spring as a preload spring, and also the means for giving a preload and the installation
location of the means can be changed.
[0038]
Furthermore, the present invention is applicable not only to a vibration generating device for
bone conduction speakers but also to any vibration generating device that requires an increase in
the amount of vibration displacement and requires downsizing and impact resistance. The
material and shape of the member can be arbitrarily designed according to the application.
[0039]
BRIEF DESCRIPTION OF THE DRAWINGS The external view which shows the vibration
generating apparatus for bone conduction speakers which is one Example of the vibration
generating apparatus by this invention.
AA sectional drawing of the Example of FIG. FIG. 2 is an exploded perspective view of parts of the
embodiment of FIG. 1; The components expansion perspective view of the acoustic signal
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generation device which has a low displacement displacement magnification mechanism. FIG. 5 is
a cross-sectional view of the device for generating an acoustic signal of FIG. 4.
Explanation of sign
[0040]
Reference Signs List 1 output pad 2 laminated piezoelectric element 2a electric signal input line
3 positioning plate 4 element receiving plate 4a stopper portion 4b screw hole 5 base 5a pin
hole 5b fixing hole 5c, 5d notch portion 6 base base portion 7 base side surface portion 8
Preload spring 9 Weight 9a Protrusion 10, 20 Magnification lever 10a Pin hole 10b Rib shape
11, 21 Magnification lever output part 12, 22 Magnification lever drive part 13 Pin 14, 24
Preload screw 15 Magnification lever base part 16 Weight 17 Fixing screw 18 Bending Part 19
Output pad
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