JP2001353874A - Piezoelectric ink jet printer head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric ink jet printer having a simple structure, a low manufacturing cost, a high resolution, excellent durability and moisture resistance and being driven with a low voltage without causing any deterioration of insulation. SOLUTION: A piezoelectric ceramics layer 40 having an inner positive electrode layer 44 and a piezoelectric ceramics layer 40 having an inner negative electrode layer 42 are laid alternately, and a piezoelectric ceramics layer 40 having no inner electrode layer is laid on the uppermost layer to form a piezoelectric actuator where the inner electrode layer is not exposed. One of the inner positive electrode layer or the inner negative electrode layer is divided to face an ink channel in one and one correspondence and the other is formed over the all ink channels. The inner positive electrode layer and the inner negative electrode layer are continuously provided with electrode take-out parts at different positions and an external electrode is provided at a position where the electrode take-out part is exposed from the piezoelectric actuator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric ink jet printer head, and more particularly to a printer head using a laminated piezoelectric element as a piezoelectric actuator.

[0002]

2. Description of the Related Art In recent years, a printer head using a piezoelectric ink jet has been proposed. This is because the volume of the ink chamber partitioned by a pair of valves is changed by the dimensional displacement of the piezoelectric actuator, so that the ink in the ink chamber is ejected through one valve when the volume decreases, and the ink from the other valve increases when the volume increases. Ink is introduced into a room, and is called a drop-on-demand method. Then, by arranging a large number of such ejecting devices close to each other and ejecting ink from the ejecting device at a predetermined position, desired characters and images are formed.

However, in the conventional piezoelectric inkjet printer head, since one piezoelectric actuator is used for one ejecting device, a large number of ejecting devices are densely arranged in order to perform printing with high resolution over a wide range. Then, there is a problem that the structure is complicated, the number of manufacturing steps is large, and the cost is high. To solve this problem, the same applicant has previously proposed the configuration described in the specification and drawings attached to the application for Japanese Patent Application No. 2-75858 (Japanese Patent Application Laid-Open No. 3-274159).
In this piezoelectric ink jet printer head, a piezoelectric ceramic layer and an internal electrode layer are alternately laminated in order to change the volume of the ink chamber of the ejecting device, and an internal positive electrode layer and an internal negative electrode layer constituting the internal electrode layer are formed. Of the electrode layers,
By providing a piezoelectric actuator in which at least one of the internal electrode layers is divided so as to correspond to the plurality of ejecting devices, over the plurality of ejecting devices, the structure is simple, the manufacturing cost is low, and high resolution and low resolution are achieved. Voltage drive is realized.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a piezoelectric ink jet having a simple structure, a low manufacturing cost, a high resolution, a low voltage drive, no insulation deterioration, and excellent durability and moisture resistance. It is an object to provide a printer head.

[0005]

In order to achieve this object, a piezoelectric ink jet printer head according to the first aspect of the present invention is provided by the action of a piezoelectric actuator in which piezoelectric ceramic layers and internal electrode layers are alternately laminated. In a piezoelectric inkjet printer head having a plurality of ejection devices arranged to eject ink in the ink chamber by changing the volume of an ink channel, the piezoelectric ceramic layer is provided continuously over the plurality of ejection devices. Dividing at least one of the internal positive electrode layer and the internal negative electrode layer constituting the internal electrode layer on the piezoelectric ceramic layer so as to be one-to-one with respect to the plurality of injection devices. The piezoelectric actuator is formed, a plurality of piezoelectric ceramic layers having the internal electrode layer formed on one surface thereof are stacked, A piezoelectric ceramic layer having no internal electrode layer is further laminated on the surface of the layered piezoelectric ceramic layer on which the internal electrode layer is formed, and the piezoelectric actuator is configured such that the internal positive electrode layer and the internal negative electrode An arrangement of the plurality of ejecting devices includes a piezoelectric active portion sandwiched between layers and corresponding to each ink channel of the plurality of ejecting devices, and a piezoelectric inactive portion not sandwiched between the internal positive electrode layer and the internal negative electrode layer. A plurality of piezoelectric actuators are integrally and continuously arranged alternately in the direction, and the piezoelectric actuator covers the ink channel and is fixed to a wall between the ink channels at the piezoelectric inactive portion.

Preferably, the piezoelectric actuator has an external electrode connected to each of the electrode lead-out portion connected to the one internal electrode layer and an electrode lead-out portion connected to the other internal electrode layer. They are provided at different positions on the outer surface.

Further, the upper and lower surfaces in the laminating direction are piezoelectric ceramic layers not exposing the internal electrode layers, and each of the electrode layers is
The external electrode is provided only at the electrode extraction portion from the piezoelectric actuator, and the external electrode is provided at each of the exposed portions.

Further, the other internal electrode layer is formed continuously over the plurality of injection devices. Further, a width of the ink channel is larger than a width of each of the divided one internal electrode layers in the arrangement direction of the plurality of ejection devices.

[0009]

According to the piezoelectric ink jet printer head of the present invention having the above-described structure, the driving voltage is applied to the external electrodes corresponding to the predetermined ejecting device at the external electrodes on the outer surface of the piezoelectric actuator provided across the plurality of ejecting devices. Is applied, the corresponding piezoelectric ceramic layer of the piezoelectric active portion is deformed, and ink is ejected from the corresponding ejection device.

[0010]

1 to 6 show an embodiment of the present invention.
This will be described in detail with reference to FIG.

FIG. 6 is a view showing a main part of an ink jet printer equipped with a piezoelectric ink jet printer head according to an embodiment of the present invention.
Is a platen. The platen 10 is rotatably attached to a frame 13 by a shaft 12 and is driven by a motor 14. A piezoelectric ink jet printer head 15 is provided facing the platen 10. The piezoelectric inkjet printer head 15 is mounted on a carriage 18 together with an ink supply device 16. The carriage 18 is slidably supported by two guide rods 20 arranged in parallel with the axis of the platen 10, and is coupled with a timing belt 24 wound around a pair of pulleys 22. Then, one pulley 22 is rotated by a motor 23 and the timing belt 24 is fed, so that the carriage 18 is moved along the platen 10.

FIG. 1 is a sectional view of an array 30 used in the piezoelectric ink jet printer head 15.
The array 30 has a width of 1.2 in the array direction 31.
mm, and three ink channels 3 whose length in the direction perpendicular to the array direction 31 (direction perpendicular to the paper surface in the figure) is 15 mm.
Channel body 34 formed with 2a, 32b, 32c
And the laminated piezoelectric element 3 fixed to the channel body 34
8 and an orifice plate 36 having an orifice 37 fixed to the channel body 34 on the side opposite to the laminated piezoelectric element 38. An ink chamber is constituted by the ink channels 32a to 32c.

The laminated piezoelectric element 38 includes a piezoelectric ceramic layer 40 having a piezoelectric / electrostrictive effect, an internal negative electrode layer 42,
The internal positive electrode layers 44a, 44b, and 4 are divided so as to correspond to the ink channels 32a to 32c one by one, and have a width of 1.0 mm in the array direction 31.
4c and a plurality of such layers are laminated to a thickness of about 0.5 mm. Then, the laminated piezoelectric element 38 includes an internal negative electrode layer 42.
And a piezoelectric active portion 46 sandwiched between the internal positive electrode layers 44a to 44c and having a width of 1.0 mm in the array direction 31.
a, 46b, 46c and both internal electrode layers 42, 44a-4
It has a piezoelectric inactive portion 48 not sandwiched between 4c.
The piezoelectric ceramic layer 40 is made of a lead zirconate titanate (PZT) -based ceramic material having ferroelectricity and has a thickness of 40 μm, and is polarized in the laminating direction. Arrows shown in each of the piezoelectric active portions 46a to 46c of the piezoelectric ceramic layer 40 in FIG. The internal negative electrode layer 42 and the internal positive electrode layer 44
Each of a to 44c is made of an Ag-Pd-based metal material and has a thickness of about 2 μm.

The laminated piezoelectric element 38 is fixed to the channel body 34 at the center of four piezoelectric inactive portions 48.

The laminated piezoelectric element 38 is manufactured by the following manufacturing method.

As shown in FIG. 4, first, the ink channels 32a to 32a are formed on the upper surface of the piezoelectric ceramic layer 40.
The internal positive electrode layers 44a to 44c divided into three so as to correspond one-to-one to 2c and the respective electrode extraction portions 45a,
The green sheets 50b are formed by forming 45b and 45c by screen printing.

On the upper surface of another piezoelectric ceramic layer 40, an internal negative electrode layer 42 and an electrode lead-out portion 43 are formed by screen printing to form a green sheet 51.
Create The position of the electrode lead-out part 43 is determined by the electrode lead-out parts 45a, 45b, 45c of the internal positive electrode layer.
The position is different in a plan view, as is clear in FIG. And both green sheets 50, 51
Are alternately laminated, and a green sheet (not shown) without an internal electrode layer is overlaid on the upper surface of the piezoelectric ceramic layer 40 on the upper part thereof, and the whole is heated and pressed to perform necessary degreasing, sintering, and the like. By applying the means, the laminated piezoelectric element 38 is obtained. The external negative electrode 52 and the external positive electrodes 54a, 54b, 54c are provided at the positions where the electrode take-out portions 43, 45a to 45c of the multilayer piezoelectric element 38 thus obtained are exposed.
Attach. Then, the laminated piezoelectric element 38 is
Immersed in an oil bath (not shown) filled with an insulating oil such as silicon oil at about ° C., and an electric field of about 2.5 kV / mm is applied between the external negative electrode 52 and the external positive electrodes 54a to 54c to cause polarization. Perform processing. The multilayer piezoelectric element 38 is obtained by the above method.

The multilayer piezoelectric element 38 thus obtained is
The array 30 is assembled by assembling a channel body 34 having three ink channels 32 having a width of 1.2 mm and a length of 15 mm and an orifice plate 36 having three orifices 37 as shown in FIG. Is configured.

Each of the arrays 30 is provided with an electric circuit shown in FIG. In this electric circuit, the negative side of the drive power supply 60 and the external negative electrode 52 of the multilayer piezoelectric element 38 are grounded, and the positive side of the drive power supply 60 is connected to the multilayer piezoelectric element via open / close switches 62a, 62b, 62c. 38 external positive electrodes 54a to 54c. When the switches 62a to 62c are closed by a controller (not shown), a drive voltage is applied from the drive power supply 60 between the internal negative electrode layer 42 and the internal positive electrode layer 44 located in the predetermined piezoelectric active portions 46a to 46c. .

The operation of the piezoelectric ink jet printer head 15 configured as described above will be described.

When the controller closes, for example, the switch 62a in accordance with predetermined print data, a voltage is applied between the internal negative electrode layer 42 and the internal positive electrode layer 44a of the piezoelectric active portion 46a, and a voltage is applied between them. A bias electric field is applied to the piezoelectric ceramic layer 40, and the piezoelectric active portion 46a expands in the vertical direction in FIG. 1 according to the dimensional distortion of the piezoelectric / electrostrictive longitudinal effect, thereby reducing the volume of the ink channel 32a. Then, the ink in the ink channel 32a is ejected as droplets 39 from the orifice 37a.
Further, when the switch 62a is opened and the application of the voltage is cut off and the piezoelectric active portion 46a is returned to the original position, the ink supply device 16 receives a signal from the ink supply device 16 through another valve (not shown) with the increase in the volume of the ink channel 32a at that time. The ink is replenished. When the other switch 62b is closed, for example, the piezoelectric active portion 46b is displaced and ink is ejected from the ink channel 32b.

That is, the array 30 of the present embodiment is composed of three ejection devices 7 of the piezoelectric ink jet printer head 15.
0a, 70b, and 70c, and one laminated piezoelectric element 38 has three injection devices 70a to 70c.
Function as a piezoelectric actuator provided across the.

FIG. 3 shows data obtained by measuring the distribution of deformation of the laminated piezoelectric element 38 in the array direction 31 when a voltage is applied. When a voltage of 25 V is applied to the piezoelectric active portion 46, the portion of the piezoelectric active portion 46 is displaced by 90 nm or more, and is displaced from the piezoelectric active portion 46 (piezoelectric inactive portion 48).
It can be seen that there is almost no displacement. From this result, it can be seen that the width of the ink channel 32 in the array direction 31 needs to be larger than the width of the piezoelectric active portion 46 in order to efficiently deform the laminated piezoelectric element 38 into the ink channel 32. . In this embodiment, the width of the ink channel 32 in the array direction 31 is set to 1.2.
mm, which is larger than the width of the piezoelectric active portion 46 of the laminated piezoelectric element 38, so that only 3 mm
It was found that a low driving voltage of 0 V was sufficient.

As described above, in the piezoelectric ink jet printer 15 of the present embodiment, since one laminated piezoelectric element 38 functions as the piezoelectric actuator of the three ejection devices 70a to 70c, the array 30, and the array 30
The structure of the piezoelectric ink jet printer head 15 is simplified by assembling a large number of them, the number of manufacturing steps is reduced, and the manufacturing cost is reduced. In addition to the fact that the piezoelectric actuator is the laminated piezoelectric element 38, the width of the ink channel 32 in the array direction 31 is larger than that of the piezoelectric active portion 46, so that efficient deformation can be obtained, so that the drive voltage can be greatly reduced. Was. Since the laminated piezoelectric element 38 has the internal electrode layers 42 and 44 formed by screen printing, the piezoelectric active portions 46a are formed.
46c and the width of the piezoelectric inactive portion 48 can be made extremely small. For example, by reducing the size of the array 30 including the three ejection devices 70a to 70c, the printing resolution can be improved. As a result, a printer head capable of printing over a wide range with high resolution is realized.

Further, the internal negative electrode layer 42 and the internal positive electrode layer 44 of the multilayer piezoelectric element 38 of this embodiment
Since it is not exposed to the outside except for 3, 45, there is an advantage that insulation deterioration due to migration of silver or the like does not occur, and excellent durability and moisture resistance can be obtained.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in the above embodiment, three injection devices 7
Although one laminated piezoelectric element 38 is used as a piezoelectric actuator provided over 0a to 70c, for example, by adopting a further divided internal positive electrode layer 44, it is possible to extend over a larger number of ejection devices. Alternatively, a piezoelectric actuator may be provided.

In the above embodiment, the internal positive electrode layer 44 is divided so as to correspond to each of the ink channels 32a to 32c on a one-to-one basis. However, the internal negative electrode layer 42 is divided into one for each of the ink channels 32a to 32c. Each of the ink channels 32a to 32c may be divided into one to correspond to one of the ink channels 32a to 32c.
It may be divided so as to correspond one-to-one. That is, at least one of the positive and negative internal electrode layers may be divided so as to correspond to each of the ink channels 32a to 32c on a one-to-one basis.

[0029]

As is clear from the above description,
According to the piezoelectric ink jet printer head of the present invention, the piezoelectric actuator is provided across the plurality of ejection devices, and one of the internal positive electrode layer and the internal negative electrode layer has one internal electrode layer corresponding to the plurality of ejection devices. Since the piezoelectric actuators are divided so as to be one-to-one, and the piezoelectric actuators are fixed to the walls between the ink channels so as to cover the piezoelectric actuators, the structure is simplified and many machining operations are performed. Therefore, the number of manufacturing steps is reduced and the inkjet head can be easily manufactured. Further, the pattern of the internal electrode layer is finely divided and formed, so that the area of the locally displaced portion of the laminated piezoelectric element can be easily reduced, thereby making it possible to reduce the size of the ejection device and improve the printing resolution.

Also, the piezoelectric actuator is formed by laminating a plurality of piezoelectric ceramic layers having the internal electrode layer formed on one surface, and superposing the piezoelectric ceramic layer of the laminated body on the surface on which the internal electrode layer is formed to form an internal electrode. Since the piezoelectric ceramic layer having no layer is further laminated, the upper and lower surfaces in the laminating direction do not expose the internal electrode layer, so there is no deterioration in insulation, and excellent durability and moisture resistance can be obtained. There are advantages.

Preferably, external electrodes are provided at different positions on the outer surface of the piezoelectric actuator for each of the electrode lead-out portion connected to one internal electrode layer and the electrode lead-out portion connected to the other internal electrode layer. Being done,
The internal electrode layer is easily connected to the control circuit, and there is no need to extend a part of the piezoelectric actuator for the connection, so that the entire device can be made compact.

[Brief description of the drawings]

FIG. 1 is a sectional view of an array constituting a part of a piezoelectric ink jet printer head.

FIG. 2 is an explanatory diagram showing a state in which an electric circuit is provided in an array.

FIG. 3 is a diagram showing a measurement result of a displacement distribution of a laminated piezoelectric element.

FIG. 4 is a perspective view of a green sheet.

FIG. 5 is a perspective view showing an assembly process of the array.

FIG. 6 is a perspective view showing a main part of an ink jet printer equipped with a piezoelectric ink jet printer head.

[Explanation of symbols]

 Reference Signs List 15 piezoelectric ink jet printer head 31 array direction 32 ink channel (ink chamber) 38 laminated piezoelectric element (piezoelectric actuator) 40 piezoelectric ceramic layer 42 internal negative electrode layer 44 internal positive electrode layer 70 ejection device

Claims (5)

[Claims] 1. A plurality of ejecting devices for ejecting ink in an ink chamber by changing the volume of an ink channel by the action of a piezoelectric actuator in which piezoelectric ceramic layers and internal electrode layers are alternately stacked are provided. In the piezoelectric ink jet printer head, the piezoelectric ceramic layer is provided continuously over a plurality of ejection devices, and at least one of the internal positive electrode layer and the internal negative electrode layer constituting the internal electrode layer Are formed on the piezoelectric ceramic layer so as to be one-to-one with respect to the plurality of injection devices, and the piezoelectric actuator includes a plurality of piezoelectric ceramic layers each having the internal electrode layer formed on one surface. The piezoelectric ceramic layer without the internal electrode layer is laminated on the surface on which the internal electrode layer of the piezoelectric ceramic layer of the laminate is formed. Wherein the piezoelectric actuator is sandwiched between the internal positive electrode layer and the internal negative electrode layer, and a piezoelectric active portion corresponding to each ink channel of the plurality of ejection devices; and the internal positive electrode layer And a plurality of piezoelectric inactive portions that are not sandwiched between the internal negative electrode layers are alternately and continuously integrated in the arrangement direction of the plurality of ejection devices, and the piezoelectric actuator covers the ink channel, A piezoelectric ink jet printer head fixed to a wall between the ink channels at an inactive portion. 2. An external electrode is provided at a different position on the outer surface of the piezoelectric actuator for each of the electrode extraction portion connected to the one internal electrode layer and the electrode extraction portion connected to the other internal electrode layer. The piezoelectric ink jet printer head according to claim 1, wherein: 3. The piezoelectric actuator according to claim 1, wherein upper and lower surfaces of the piezoelectric actuator are formed of a piezoelectric ceramic layer that does not expose an internal electrode layer, and each of the electrode layers is exposed from the piezoelectric actuator only at the electrode lead-out portion. 3. The piezoelectric ink jet printer head according to claim 2, wherein the external electrodes are provided at respective locations. 4. The piezoelectric ink jet printer head according to claim 1, wherein the other internal electrode layer is formed continuously over the plurality of ejection devices. 5. The piezoelectric device according to claim 1, wherein the width of the ink channel is larger than the width of each of the divided one internal electrode layers in the arrangement direction of the plurality of ejection devices. Type inkjet printer head.