JPH03254952A - Printing element - Google Patents

Abstract

PURPOSE:To obtain a highly reliable printing element at a low cost by a method wherein a driving power source is formed by alternately disposing multilaminated electro-mechanical coversion elements having a longitudinal effect, which are constituted of the lamination of piezoelectric ceramic layers, and multiple temperature-compensating members for the purpose of making the linear expansion coefficient of the whole driving power source equal to that of a frame. CONSTITUTION:For example, forty-five piezoelectric ceramic layers 42 are laminated via electrode layers 41 and unitarily sintered to form a laminated piezoelectric element 40. The laminated piezoelectric element 40 thus formed has a piezoelectric longitudinal effect. Further, aluminum is used as a temperature compensating member 12. Five laminated piezoelectric elements 40 and four temperature compensating members 12 are alternately laminated and allowed to adhere to one another with an adhesive to be converted into a driving power source 1. Furthermore, the linear expansion coefficient of the entire length of the driving power source 1 is made equal to the linear expansion coefficient of a frame 80.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is a printing element, in particular, a method for enlarging the dimensional distortion generated by the piezoelectric or electrostrictive longitudinal effect of a piezoelectric ceramic material and transmitting it to a printing wire to print dots. It relates to printing elements that

[Prior Art] Conventionally, as this type of printing element, there is one shown in FIG. 3, for example. In this printing element, a drive source 1 made of a laminated longitudinal effect piezoelectric element that expands and contracts when a voltage is applied is attached to a frame (main frame 2) having a base 3 that supports one end of the drive source 1 in the expansion and contraction direction. There is. A movable element 5 is attached to the other end of the drive source 1 in the direction of expansion and contraction, and a motion conversion mechanism connected to the movable element 5 to magnify the expansion and contraction movement of the drive source 1 is provided. This motion conversion mechanism is mainly composed of a pair of leaf springs 6.7 having one end fixed to the main frame 2 and the movable element 5, and a tilting body 8 connecting the other end of the leaf spring 6.7. ing. This motion conversion mechanism is
The expansion and contraction movement of the drive source 1 due to the application of voltage and the interruption of the voltage is converted into the tilting movement of the tilting body 8 by using the deflection of the leaf spring 6.7. In response to this tilting movement, the wire 11 impacts in two directions shown in the figure to perform dot printing.

In the printing element as described above, as shown in FIG.
So, the piezoelectric constant aaS is 6,35X10-10 m/
V, and the electrostriction constant M33 is 1.32X10 m/v
2, the piezoelectric ceramic layer 42 has a layer thickness of 2 μm.
180 electrode layers 41 are stacked, and the total length is 1.
A laminated longitudinal effect piezoelectric element with a thickness of 8 mm is used. 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. Note that in the figure, an arrow 45 indicates the polarization direction of the piezoelectric ceramic layer 41.

In addition, the driving source 1 has a property that the strain caused by polarization is released when the temperature rises, and therefore, unlike other constituent materials, it has a negative coefficient of linear expansion in the direction of expansion and contraction (for example, -3° sppm/°C). . Therefore, during operation, the main frame 2 and drive source 1. It is necessary to correct the difference in the amount of expansion. Therefore, as a material for the main frame 2, a material with a low expansion coefficient (for example, a linear expansion coefficient of +1.2 ppm/'
A rigid body having a large positive linear expansion coefficient (for example, aluminum having a linear expansion coefficient of +23.9 ppm/° C. and a total length of 4 mm) was used as the temperature compensating material 12.13.

[Problems to be Solved by the Invention] However, the device described in item 1 has a problem in that it requires a high driving voltage (107 V on the upper side). In order to reduce this driving voltage, it is easy to consider, for example, reducing the thickness of one layer of the piezoelectric ceramic layer 42 and increasing the number of layers laminated. However, such a multilayer element has a new problem in that reliability is lowered due to the temperature difference between the layer near the surface and the layer in the center during sintering, and the number of layers cannot be increased very much.

Furthermore, since the constituent materials having a low coefficient of expansion in the above-mentioned device are very expensive, there is also the problem that the material cost is high.

Furthermore, if the thermal conductivity of the driving source 1 is not sufficiently large, a temperature difference will occur between the driving source 1 and the temperature compensating material 12, 13 during driving. Therefore, the temperature compensation effect of the two series cannot be sufficiently obtained, 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 a problem that problems such as the tip of the wire 11 being caught on the ink ribbon are likely to occur.

The present invention has been made in order to solve the above-mentioned problems, and provides a drive source made of a laminated longitudinal effect piezoelectric element in which the thickness of each piezoelectric ceramic layer is reduced without reducing reliability. With the goal.

Furthermore, it is an object of the present invention to reduce the driving voltage of the element.

Furthermore, by changing the length ratio of the temperature compensating material to the laminated piezoelectric element, the linear expansion coefficient of the driving source can be controlled, increasing the degree of freedom in selecting the main frame material, and thereby reducing the cost of the main frame material. The purpose is to

Furthermore, the purpose is to reduce the temperature difference during driving between the drive source and the temperature compensating material compared to conventional methods, improve the reliability of the temperature compensation effect, and provide a low-cost and highly reliable printing element. .

[Means for Solving the Problems] In order to achieve the object stated in item 1, the present invention provides a drive source that produces a piezoelectric longitudinal effect or an electrostrictive longitudinal effect by applying an electric signal, and one end of the drive source in the direction of expansion and contraction. In the printing element, the printing element includes a frame having a base for supporting the drive source, and a motion converting mechanism for magnifying the expansion/contraction movement of the drive source, wherein the drive source includes a plurality of laminated longitudinal effect electric machines configured by laminating piezoelectric ceramic layers. A conversion element and a large number of temperature compensating members for correcting the linear expansion coefficient of the laminated longitudinal effect electromechanical conversion element to make the linear expansion coefficient of the drive source as a whole the same as that of the frame are arranged alternately. It is characterized by:

[Function] According to the present invention having the configuration described in item 1, by laminating the required number of laminated longitudinal effect electromechanical transducers, a desired amount of displacement is obtained. The number of laminated conversion elements may be small. Therefore, there is little difference in temperature between the center and the periphery during sintering. Therefore, it is possible to obtain a laminated longitudinal effect electromechanical transducer with a layer thickness of, for example, about 40 μm while maintaining high reliability.

Furthermore, since each laminated longitudinal effect electromechanical transducer is formed by laminating thin piezoelectric elements or electrostrictive elements, a large amount of displacement can be obtained with a small voltage. Furthermore, since the length of the laminated longitudinal effect electromechanical transducer required to obtain an appropriate displacement can be shortened, the length of the temperature compensation material occupied in the drive source can be increased accordingly. Therefore, it is possible to use inexpensive materials for the frame. The linear expansion coefficient of the drive source can be freely adjusted according to the linear expansion coefficient of the main frame material, and the cost of the main frame material can be reduced.

In addition, by arranging a plurality of laminated piezoelectric elements and a plurality of temperature compensating members alternately, heat generated by the elements is efficiently transmitted to the temperature compensating member. Therefore, the temperature difference between the laminated longitudinal effect electromechanical transducer and the temperature compensation material during driving can be made smaller than in the past. Therefore, an appropriate temperature compensation effect can be obtained.

[Example] An example embodying the present invention will be described with reference to FIGS. 1 and 2. For convenience, parts that are the same or equivalent to those of the conventional example are given the same reference numerals, and detailed explanation thereof will be omitted.

The frame 80 supporting the drive source 1 has a linear expansion coefficient of +12
．． As shown in FIG. 1, a sintered steel material of 1 p p m/'C is formed into a substantially U-shape.

This frame 80 has a main frame portion 2 extending parallel to the direction of expansion and contraction of the drive source 1, and a base portion at the lower end of the main frame portion 2 that supports one end (lower end) of the drive source 1 in the direction of expansion and contraction. 3 stands out.

A sub-frame part 4 is formed which is connected to the base part 3 and is parallel to the main frame part 2.

At the other end of the drive source 1 in the expansion and contraction direction (upper side in the first diagram),
A mover 5 is disposed facing one end of the main frame section 2. A pair of leaf springs 6.7 is fixed at one end of the opposing surfaces of the main frame portion 2 and the movable element 5, respectively. Double leaf spring 6.7
are opposed to each other with a predetermined gap in between, and the other ends (extending ends) are connected by a tilting body 8. of tilting body 8.
A tilting arm 10 having a printing wire 11 attached to its tip is fixed to the two sides. Note that, by displacing the other end of one of the leaf springs 7 along the surface direction of the leaf spring 6, the tilting member 8 is tilted.

The facing surfaces of the driving source 1 and the base 3 of the frame 80 and the facing surfaces of the driving source element 1 and the movable element 5 are bonded with an adhesive.

Further, between the upper end of the sub-frame section 4 and the movable element 5, there is provided a four-bar parallel link mechanism made of a spring plate in order to move the movable element 5 in parallel to the expansion and contraction direction of the drive source 1 based on the expansion and contraction of the drive source 1. 16 are arranged.

In the printing element described above, when a voltage is applied to the drive source 1, the drive source 1 expands, and the movable element 5 is displaced (raised) based on this. At this time, the leaf springs 6 and 7 are bent in response to the displacement force of the movable element 5, so that the tilting arm 10 is tilted counterclockwise in FIG. By tilting the tilting arm 10, the printing wire 1
1 is advanced to the printing position.

Further, when the application of voltage to the drive source 1 is cut off,
The driving source 1 is shortened to its original state. Based on this, the movable element 5, the leaf springs 6, and the leaf springs 7 return to their original states, thereby returning the printing wire 11 to the standby position.

At this time, the tilting arm 10 contacts the stopper 35 and is supported at the standby position.

Also, based on the displacement of the movable element 5, the parallel link mechanism 16
By elastically deforming, the movable element 5 is displaced in parallel to the direction of expansion and contraction of the drive source 1.

The drive source 1 includes a laminated piezoelectric element 40 as shown in FIG.
and a temperature compensating material 12. -layer thickness 40μ
m, the piezoelectric constant (Iaa is 6.35X10-10m/
45 piezoelectric ceramic layers 42 having an electrostriction constant Ma3 of 1.32×109−10−” m/V2 are laminated via electrode layers 41 each having a thickness of 2 μm.
In the figure, the number of laminated layers is simplified as 3), and the length is 1.
．． The laminated piezoelectric element 40 is integrally sintered to have a thickness of 89 mm.
shall be. The laminated piezoelectric element 40 configured as described in item 1 has a piezoelectric longitudinal effect. Further, as the temperature compensating material 12, aluminum having a length of 3° and 15 mm is used. Then, the five laminated piezoelectric elements 40 and the four temperature compensating members 12 are alternately laminated and bonded using a known adhesive to form the drive source 1 of this embodiment. This driving source 1 has a length of 2
2 mm, and expands and contracts in the longitudinal direction (downward direction 1 in FIG. 2) by applying voltage and cutting off the application.

The coefficient of linear expansion of the laminated piezoelectric element 40 used in this drive source 1 is -3.8 ppm10C due to the effect of releasing strain caused by polarization of the element when the temperature rises.

However, the temperature compensation material 12 made of aluminum has a large positive coefficient of linear expansion +23. 9 p pm/'C, the linear expansion coefficient for the entire length of the driving source 1 is substantially +1
2. 1 pp pm/'C. This value is the same as the linear expansion coefficient of the frame 80.

In the above example, a displacement of 15 μm of the drive source 1 necessary for printing could be obtained with a drive voltage of 76V.

Therefore, the driving voltage has been significantly reduced compared to the conventional device which required a driving voltage of 107V. . In addition, although the laminated piezoelectric element 40 has an extremely thin thickness of 40 μm for each layer of the piezoelectric ceramic layer 42, the number of laminated layers is small at 45 and the length is small at 1.89 mm.
It is easy to control the uniformity of crystal grain size, densification, etc., and there is no decrease in reliability of piezoelectric properties, insulation properties, etc.

Therefore, it is possible to maintain stable performance compared to conventional devices, and the yield of the drive source 1 is also improved.

Furthermore, since the electromechanical transducer of the drive source 1 is a multilayer type driven by a low voltage as described above, sufficient displacement can be obtained even if the length of the element is shortened relative to the overall length. . Therefore, it becomes easy to increase the ratio of the length occupied by the temperature compensation vJ12, and a high coefficient of linear expansion of the drive source 1 can be obtained. Therefore, for example, as mentioned above, the linear expansion coefficient is +12. By setting it to 1 ppm/'C, a relatively inexpensive sintered steel material can be used as the frame. In addition, the temperature compensating material 12 for the entire length
By changing the ratio of the lengths of the frame, the linear expansion coefficient of the drive source as a whole can be adjusted, and other materials can be used for the frame.

Furthermore, in this embodiment, the temperature difference between the drive source 1 and the temperature compensating material 12 caused by heat generated from the drive source during printing operation is
It is significantly smaller than the conventional example. For example, in the experimental example, the temperature difference between the center of the drive source 1 and the temperature compensating material 12 is around 25°C. The temperature difference is around 2°C.

As a result, the reliability of the temperature compensation effect is increased, and it is possible to prevent the occurrence of problems such as the tip of the wire 11 getting caught on the ink ribbon as in the conventional case.

Furthermore, the present invention is not limited to the above embodiments,
Changes can be made according to the purpose without departing from the gist of the invention.

For example, if you are aiming only to reduce the drive voltage without considering the cost reduction of the main frame 2, as the drive source 1, -
A piezoelectric ceramic layer 42 having a layer thickness of 40 μm,
- A monolithically sintered piezoelectric longitudinal effect laminated piezoelectric element 40 in which 86 pieces are laminated via electrode layers 41 with a layer thickness of 2 μm and a length of 3.61 mm (piezoelectric constants and electrostrictive constants are the same as those in the example described above). ) and four pieces of aluminum with a length of 1 mm as the temperature compensating material 12 are arranged and bonded with adhesive to make the length 22 mm, the driving voltage required for printing is It can be reduced to 45V. Furthermore, as a drive source 1 for low voltage drive, 164 piezoelectric ceramic layers 42 each having a thickness of 20 μm are laminated via electrode layers 41 each having a thickness of 2 μm, and the length is 3.61 mm. Five integrally sintered piezoelectric longitudinal effect laminated piezoelectric elements 40 (the piezoelectric constant and electrostrictive constant are the same as in the previous example) and four aluminum pieces each having a length of 1 mm as the temperature compensating material 12 were arranged. If the length is 22 mm and the length is 22 mm, the driving voltage required for printing can be reduced to 23 V.

[Effects of the Invention] As is clear from the detailed description below, according to the printing element of the present invention, a laminated longitudinal effect piezoelectric element in which the thickness of each layer of the piezoelectric ceramic layer is reduced without reducing the reliability. A driving source consisting of the following can be obtained, and the driving voltage can be reduced. In addition, by changing the ratio of the length of the temperature compensating material to the laminated piezoelectric element, the linear expansion coefficient of the drive source can be controlled, increasing the degree of freedom in selecting the main frame material and reducing the cost of the main frame material. Furthermore, the temperature difference between the laminated longitudinal effect piezoelectric element and the temperature compensating material during operation is smaller than that in the past, and the reliability of the temperature compensating effect can be improved.

[Brief explanation of drawings]

1 and 2 show embodiments 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. Furthermore, Figures 3 and 4 show conventional devices;
The figure is a side view of the printing element, and FIG. 4 is a schematic perspective view of the drive source. In the figure, 1 is a drive source, 3 is a base, 5 is a mover, 12 is a temperature compensator, 42 is a piezoelectric ceramic layer, and 80 is a frame.

Claims (1)

[Claims] 1. A drive source that produces a piezoelectric longitudinal effect or an electrostrictive longitudinal effect by application of an electric signal; a frame having a base that supports one end of the drive source in an expansion/contraction direction; and an expansion/contraction of the drive source. A printing element equipped with a motion converting mechanism for amplifying motion, wherein the drive source includes a large number of laminated longitudinal effect electromechanical transducers formed by laminating piezoelectric ceramic layers, and a line of the laminated longitudinal effect electromechanical transducer elements. A printing element characterized in that a plurality of temperature compensating members are arranged alternately to correct the coefficient of expansion so that the coefficient of linear expansion of the drive source as a whole is the same as that of the frame.