JPH03254952

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DESCRIPTION JPH03254952
[0001]
[Industrial Application Field] The present invention relates to a printing element, in particular, a
printing element in which the dimensional distortion generated by the piezoelectric or
electrostrictive longitudinal effect of the piezoelectric ceramic material is enlarged and
transmitted to the printing wire for dot printing . [Prior Art] Conventionally, as such a printing
element, there is, for example, one as shown in FIG. In this printing element, the drive source 1
consisting of laminated longitudinal effect piezoelectric elements that expand and contract by the
application of voltage is attached to a frame (main frame 2) having a base 3 supporting one end
of the drive source 1 in the expansion and contraction direction There is. A mover 5 disposed at
the other end of the drive source 1 in the expansion / contraction direction is attached, and is
connected to the mover 5 to have a motion conversion mechanism for expanding the expansion /
contraction motion of the drive source 1. This motion conversion mechanism mainly includes a
pair of leaf springs 6.7 having one end fixed to the main frame 2 and the mover 5, and a tilting
body 8 connecting the other ends of the leaf springs 6.7. ing. The motion conversion mechanism
converts the expansion and contraction movement of the drive source 1 due to the application of
the voltage and the interruption of the voltage into the tilting movement of the tilting body 8
using the deflection of the plate spring 6.7. In accordance with this tilting movement, the wire 11
impacts in the two directions shown in FIG. In the printing element as described above, as
shown in FIG. 4, for example, the thickness of the − layer is 98 μm and the piezoelectric
constant aaS is 6, 35 × 10 −10 m / V as the driving source 1 The piezoelectric ceramic layer 42
having a constant M33 of 1,32 × 10 golo m / v 2 is stacked 180 layers via the electrode layer
41 having a thickness of 2 μm, and the total length is 18 mm. . Therefore, in order to obtain the
displacement of the drive source 1 necessary for printing, for example, 15 μm, a drive voltage of
107 V is required. In the drawing, the arrow 45 indicates the polarization direction of the
piezoelectric ceramic layer 41. In addition, the drive source 1 has a property that the strain
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accompanying polarization is released at the time of temperature rise, and therefore, unlike other
components, it has a negative linear expansion coefficient (for example, -3 s ppm / ° C) in the
stretching direction. Have. For this reason, the main frame 2 and the drive source 1 due to the / +
111 degrees one rise in operation. It is necessary to correct the difference in the amount of
expansion of Therefore, a low expansion coefficient component (for example, an invar alloy with
a linear expansion coefficient of +1.2 ppm / 'C) is used as the material of the main frame 2, and a
rigid body having a large positive linear expansion coefficient as the temperature compensation
material 12.13. (For example, aluminum having a linear expansion coefficient of +23.9 ppm / °
C. and a total length of 4 mm) was used.
[Problem to be solved by the invention] However, there is a problem that the device described in
1 requires a high drive voltage (107 V on the upper side). In order to reduce this drive voltage,
for example, it is easily considered to reduce the thickness of one layer of the piezoelectric
ceramic layer 42 and to increase the number of stacked layers. However, such a multilayer
device has a new problem that the reliability is lowered due to the temperature difference
between the layer in the vicinity of the surface and the layer in the central portion during
sintering, and the number of laminated layers can not be increased so much. In addition, since
the low expansion coefficient component in the above-described apparatus is very expensive,
there is a problem that the material cost is high. When the thermal conductivity of the drive
source 1 is not sufficiently large, a temperature difference occurs between the drive source 1 and
the temperature compensation member 12.13 during driving. For this reason, the dual
temperature compensation effect is not obtained sufficiently, and the thermal expansion of the
drive source 1 precedes, and the tip position of the wire 11 protrudes more than before the
temperature rise. Therefore, there is also a problem that the end of the wire 11 is likely to cause
a defect such as being caught by the ink ribbon. The present invention has been made to solve
the above-mentioned problems, and provides a driving source comprising a laminated
longitudinal effect piezoelectric element in which the thickness of one layer of the piezoelectric
ceramic layer is reduced without reducing the reliability. With the goal. Furthermore, it aims at
reducing the drive voltage of an element. Furthermore, the linear expansion coefficient of the
drive source is controlled by changing the ratio of the length of the temperature compensation
material to the laminated piezoelectric element, and the freedom of selection of the mainframe
material is increased, thereby reducing the cost of the mainframe material. The purpose is
Furthermore, it is an object of the present invention to reduce the temperature difference during
driving between the driving source and the temperature compensation member as compared
with the prior art, to improve the reliability of the temperature compensation effect, and to
provide a low cost and highly reliable printing element. . [Means for Solving the Problems] In
order to achieve the above object, the present invention provides a drive source that generates a
piezoelectric longitudinal effect or an electrostrictive longitudinal effect by the application of an
electric signal, and one end of the drive source in the stretching direction. A printing element
provided with a frame having a base for supporting the movement and a motion conversion
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mechanism for expanding the expansion and contraction movement of the drive source, wherein
the drive source comprises a plurality of laminated longitudinal effect electric machines
configured by laminating piezoelectric ceramic layers A conversion element and a plurality of
temperature compensation members for correcting the linear expansion coefficient of the
laminated longitudinal effect electromechanical conversion element to make the linear expansion
coefficient as the entire drive source identical to that of the frame are alternately arranged. It is
characterized by becoming. [Operation] According to the present invention having the abovedescribed configuration, by laminating the required number of laminated longitudinal effect
electro-mechanical transducers, − = 6̶a desired displacement amount can be obtained. The
number of laminated conversion elements may be small.
Therefore, temperature differences hardly occur at the center and the periphery during sintering.
Therefore, even if the thickness of the layer is, for example, about 40 μm, it can be obtained
while maintaining high reliability. In addition, since each stacked vertical effect
electromechanical transducer is formed by stacking thin piezoelectric elements or electrostrictive
elements, a large displacement can be obtained with a small voltage. Furthermore, since it is
possible to shorten the length of the laminated longitudinal effect electromechanical transducer
necessary to obtain an appropriate displacement, it is possible to lengthen the length of the
temperature compensation material occupied in the drive source accordingly. Therefore, it
becomes possible to use an inexpensive material for the frame. The linear expansion coefficient
of the drive source can be freely adjusted in accordance with the linear expansion coefficient of
the main frame material, and cost reduction of the main frame material can be realized. Further,
by alternately arranging a plurality of laminated piezoelectric elements and a plurality of
temperature compensation materials, heat generated by the elements is efficiently transmitted to
the temperature compensation material. Therefore, the temperature difference at the time of
driving between the laminated longitudinal effect electromechanical transducer and the
temperature compensation material can be made smaller than that in the prior art. Therefore, an
appropriate temperature compensation effect can be obtained. Embodiment An embodiment of
the present invention will be described with reference to FIGS. 1 and 2. FIG. For convenience, the
same parts as or parts equivalent to those of the conventional example are designated by the
same reference numerals and the detailed description thereof is omitted. As shown in FIG. 1, the
frame 80 supporting the driving source 1 is a substantially U-shaped sintered steel material
having a coefficient of linear expansion of +12.1 ppm / 'C. The frame 80 has a main frame
portion 2 extending parallel to the expansion and contraction direction of the drive source 1, and
a lower end portion of the main frame portion 2 supports one end (lower end) of the expansion
and contraction direction of the drive source 1 Three are protruding. A subframe portion 4 is
formed in parallel to the main frame portion 2 so as to be connected to the base portion 3. The
mover 5 is disposed at the other end (upper side in the first illustration) of the drive source 1 in
the expansion / contraction direction so as to face one end portion of the main frame portion 2.
A pair of plate springs 6.7 are fixed to the opposing surfaces of the main frame portion 2 and the
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mover 5 at their one end. The two leaf springs 6.7 are opposed to each other with a
predetermined gap, and the other end (extending end) is connected by the tilting body 8. A tilting
arm 10 having a printing wire 11 attached at its tip is fixed to the two surfaces of the tilting body
8. Note that, by displacing the other end of one plate spring 7 along the surface direction of the
plate spring 6 with the plate spring 6.7 and the tilting body 8, the tilting body 8 is made to move
to tilt.
The facing surfaces of the drive source 1 and the base 3 of the frame 80 and the facing surfaces
of the drive source 1 and the mover 5 are bonded by an adhesive. Further, between the upper
end portion of the sub-frame portion 4 and the mover 5, the mover 5 is moved in parallel with
the extension direction of the drive source 1 based on the extension of the drive source 1. 16 are
provided. In the printing element described above, when a voltage is applied to the drive source
1, the drive source 1 expands, and based on this, the mover 5 is displaced (raised). At this time,
the tilting arm 10 is tilted in the counterclockwise direction in FIG. 1 by the deflection of the leaf
spring 6 and the leaf spring 7 under the displacement force of the mover 5. The tilting of the
tilting arm 10 advances the printing wire 11 to the printing position. When the application of the
voltage to the drive source 1 is cut off, the drive source 1 is shortened to the original state. Based
on this, when the mover 5, the plate spring 6 and the plate spring 7 are returned to the original
state, the printing wire 11 is returned to the standby position. At this time, the tilting arm 10
abuts on the stopper 35 and is supported at the standby position. Further, the parallel link
mechanism 16 is elastically deformed based on the displacement of the movable element 5,
whereby the movable element 5 is displaced in parallel with the expansion and contraction
direction of the drive source 1. The drive source 1 is composed of a laminated piezoelectric
element 40 and a temperature compensation material 12 as shown in FIG. -The thickness of the
layer is 40 μm, and the piezoelectric constant (Iaa is 6. A piezoelectric ceramic layer 42 with 35
× 10 −10 m / V and an electrostriction constant Ma 3 of 1.32 × 10 9 − ′ ′ m / V 2 is
stacked in 45 sheets via an electrode layer 41 with a thickness of −2 μm. Then, the number of
laminated layers is simplified as three sheets) and integrally sintered with a length of 1.89 mm to
obtain the laminated piezoelectric element 40. The laminated piezoelectric element 40
configured as described above has a piezoelectric longitudinal effect. Further, as the temperature
compensation material 12, aluminum of 3 ° 15 mm in length is used. Then, the temperature
compensation members 12 are alternately stacked on five 1 stacked piezoelectric elements
40 and four − , and are bonded with a known adhesive to make the drive source 1 of this
embodiment. The drive source 1 has a length of 22 mm, and expands and contracts in the
longitudinal direction (the downward direction in FIG. 2) by the application of a voltage and the
interruption of the application. The linear expansion coefficient of the laminated piezoelectric
element 40 used for the driving source 1 is −3, 8 ppm 10 C due to the effect of release at the
time of temperature rise of strain accompanying the polarization of the element. However, the
temperature compensation material 12 made of aluminum has a large positive linear expansion
coefficient +23. Since it has 9 p pm / 'C, the linear expansion coefficient for the entire length of
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the drive source 1 is substantially +12. It is 1 p pm / 'C.
This value is the same as the linear expansion coefficient of the frame 80. In the above
embodiment, with the drive voltage of 76 V, the displacement of the drive source 1 of 15 μm
necessary for printing could be obtained. Therefore, the drive voltage is greatly reduced as
compared with the conventional device which required 107 V as the drive voltage. . In the
laminated piezoelectric element 40, although the thickness of one layer of the piezoelectric
ceramic layer 42 is extremely thin at 40 μm, the number of laminated layers is as small as 45
and the length is as small as 1.89 mm. Control of uniformity and densification, etc. is easy, and
there is no decrease in reliability with respect to piezoelectric characteristics, insulation
characteristics and the like. Therefore, stable performance can be maintained as compared with
the conventional device, and the yield of the drive source 1 is also improved. Further, as the
electromechanical transducer of the drive source 1 is used as described above, the low voltage
driven laminated type is used, therefore, sufficient displacement can be obtained even if the
length of the device with respect to the entire length is shortened. . Therefore, it is easy to
increase the ratio of the length occupied by the temperature compensation vJ12, and a high
linear expansion coefficient of the drive source 1 can be obtained. Therefore, for example, as
described above, the linear expansion coefficient is +12. By setting to 1 ppm / 'C, a relatively
inexpensive sintered steel material can be used as a frame. In addition, by changing the ratio of
the length of the temperature compensation member 12 to the total length, the linear expansion
coefficient of the entire drive source can be adjusted, and a frame made of another material can
be used. Further, in the present embodiment, the temperature difference between the driving
source 1 and the temperature compensating member 12 caused by the heat generation from the
driving source during the printing operation is significantly smaller than that in the conventional
example. For example, in the experimental example, the temperature difference between the
central portion of the drive source 1 and the temperature compensation material 12 is around 25
° C. In the case where the present embodiment is applied to this, the laminated piezoelectric
element 40 and the temperature compensation material 12 The temperature difference with is
about 2 ° C. As a result, the reliability of the effect of temperature compensation is enhanced,
and the occurrence of a defect such as the tip of the conventional wire 11 being caught on the
ink ribbon can be prevented. Furthermore, the present invention is not limited to the abovedescribed embodiment, and modifications can be made according to applications without
departing from the scope of the present invention. For example, when aiming to reduce the
driving voltage without considering the cost reduction of the main frame 2, the piezoelectric
ceramic layer 42 having a thickness of 40 μm is used as the driving source 1, and the thickness
of the layer is 2 μm. Integrally-sintered laminated piezoelectric element 40 (the same as in the
previous example) with the integral piezoelectric longitudinal effect laminated on 86 sheets via
the electrode layer 41 and having a length of 3.61 mm The driving voltage required for printing
can be reduced to 45 V by using the temperature compensating material 12 and four aluminum
pieces of 1 mm in length arranged and joined with an adhesive and having a length of 22 mm.
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Furthermore, as the driving source 1 for low voltage driving, a piezoelectric ceramic layer 42
having a thickness of -20 μm is stacked on 164 sheets of an electrode layer 41 having a
thickness of -2 μm, and the length is 3.61 mm. 5 stacked piezoelectric elements 40 (the
piezoelectric constant and the electrostriction constant are the same as in the previous
embodiment) of the piezoelectric longitudinal effect of integral sintering and 4 pieces of
aluminum having a length of 1 mm as the temperature compensation material 12 The drive
voltage required for printing can be reduced to 23 V by using an adhesive having a length of 22
mm. [Effects of the Invention] As is apparent from the detailed description in detail, according to
the printing element of the present invention, a laminated longitudinal effect piezoelectric
element in which the thickness of one layer of the piezoelectric ceramic layer is reduced without
reducing the reliability Can be obtained to reduce the driving voltage. In addition, by changing
the ratio of the length of the temperature compensation material to that of the laminated
piezoelectric element, the linear expansion coefficient of the drive source can be controlled, and
the freedom of selection of the mainframe material is increased. Also, the temperature difference
between the laminated longitudinal effect piezoelectric element and the temperature
compensation material during driving is smaller than that in the conventional case, and the
reliability of the temperature compensation effect can be improved.
[0002]
Brief description of the drawings
[0003]
1 and 2 show an embodiment embodying the present invention. FIG. 1 is a side view of a printing
element, and FIG. 2 is a schematic perspective view of a drive source.
3 and 4 show a conventional device, and FIG. 3 is a side view of the printing element, and FIG. 4
is a schematic perspective view of a drive source. In the figure, 1 is a drive source, 3 is a base, 5
is a mover, 12 is a temperature compensation material, 42 is a piezoelectric ceramic layer, and
80 is a frame.
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