JPH04290750A - Piezoelectric liquid droplet jet apparatus - Google Patents

Abstract

PURPOSE:To enhance the degree of integration of ink flow passages and to achieve the miniaturization of a jet apparatus and the enhancement of printing resolving power by injecting the ink in the ink flow passages by the deformation of the piezoelectric material provided around the ink flow passages corresponding to a predetermined jet apparatus due to piezoelectric thickness slide effect. CONSTITUTION:Ink flow passages 4 are divided into groups A, B, C not adjacent to each other and the groups A, B, C are driven by the continuous clock pulses supplied from a clock line. Further, it is determined which ink flow passages 4 of each of the groups must be operated and the voltage V of a voltage line is applied to the electrodes 6 of the selected group. By applying an electric field in the direction vertical to the polarizing direction of both piezoelectric ceramics plates 2,3 across the respective electrodes of six ink flow passages 4 adjacent to the selected ink flow passages 4, the walls of the ink flow passages of both piezoelectric ceramics plates 2, 3 are deformed by piezoelectric thickness slide effect to change the volumes of the selected ink flow passages 4. Therefore, all of the ink flow passages 4 of each group become operable.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric droplet ejecting device, and more particularly to a piezoelectric droplet ejecting device that utilizes deformation of a piezoelectric transducer.

0002

2. Description of the Related Art Conventionally, printer heads using piezoelectric inkjet have been proposed in recent years. this is,
By changing the volume of the ink flow path by dimensional displacement of the piezoelectric actuator, ink in the ink flow path is ejected from the orifice when the volume decreases, and ink is introduced into the ink flow path from the other valve when the volume increases. This is called the drop-on-demand method. By arranging a large number of such ejecting devices close to each other and ejecting ink from the ejecting devices at predetermined positions, desired characters and images are formed.

0003

[Problems to be Solved by the Invention] However, in conventional piezoelectric droplet ejecting devices, one piezoelectric actuator is used in one ejecting device. If devices are arranged closely together, there are problems in that the structure is complicated, requires a large number of manufacturing steps, and is expensive.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a piezoelectric droplet ejecting device that has a simple structure, low manufacturing cost, and can provide high resolution. do.

[0005]

[Means for Solving the Problems] In order to achieve this object, the piezoelectric droplet ejecting device of the present invention uses a piezoelectric transducer to eject ink in an ink flow path by changing the volume of the ink flow path. Equipped with many devices,
The piezoelectric transducer is made of a piezoelectric material having a plurality of ink channels passing through it in a direction parallel to the polarization direction, and is configured such that the driving electric field direction is perpendicular to the polarization direction.

[0006]

[Operation] According to the piezoelectric droplet ejecting device of the present invention having the above configuration, the piezoelectric material around the ink flow path corresponding to a predetermined ejection device is deformed by the piezoelectric thickness shear effect, and the inside of the flow path is deformed. of ink is ejected from the ejector.

[0007]

[Example] Hereinafter, an example embodying the present invention is shown in Fig. 1.
This will be explained in detail with reference to FIGS. FIG. 10 is a diagram showing the main parts of an inkjet printer equipped with a piezoelectric droplet ejecting device according to an embodiment of the present invention. It is mounted and driven by a motor 42. A piezoelectric droplet ejecting device 4 is mounted opposite the platen 36.
4 are provided. A piezoelectric droplet ejecting device 44 is mounted on a carriage 48 together with an ink supply device 46 . The carriage 48 is slidably supported by two guide rods 50 arranged parallel to the axis of the platen 36, and is coupled to a timing belt 56 wound around a pair of pulleys 52. Then, one pulley 52 is rotated by the motor 54, and the timing belt 56 is fed, thereby moving the carriage 48 along the platen 36.

FIG. 1 is a cross-sectional view of the array 1 used in the piezoelectric droplet ejecting device 44. As shown in FIG. Moreover, FIG. 2 is a longitudinal cross-sectional view of the array 1 (a vertical cross-sectional view taken along the line xx' in FIG. 1). Array 1 is polarized in the direction of arrow 26,
And through holes with a diameter of 0.5 mm and a center distance of 0.75 m.
m, an upper piezoelectric ceramic plate 2 with a thickness of 1.25 mm arranged in a geometric shape having a six-fold symmetry axis as shown in FIG. 2, a lower piezoelectric ceramic plate 3 with a thickness of 1.25 mm has through-holes with a diameter of 0.5 mm arranged at a center-to-center distance of 0.75 mm in a geometric shape with a six-fold symmetry axis as shown in FIG. are bonded together via an adhesive layer 14. Here, the ink flow path 4 formed by the through hole
is a circular cross section with a diameter of 0.5 mm, and the flow path length is 2.5 mm.
mm, and the width of the walls of both piezoelectric ceramics 2 and 3 that separate the flow path is 0.25 mm at the minimum. Electrodes 6 are formed on the inner wall surfaces of all the ink channels 4, and the surfaces of the electrodes 6 are subjected to insulation treatment to insulate them from the ink. Further, each ink flow path 4 is provided on the upper surface of the upper piezoelectric ceramic plate 2.
A bottom plate 12 having an ink supply path 13 connected to the above-mentioned ink supply device 46 corresponding to each ink flow path 4 is joined to the lower surface of the orifice plate 8 having orifices 10 corresponding to the orifices 10 and the lower piezoelectric ceramic plate 4. It has been done. The injector 34 has an orifice 10 that injects droplets.
, an ink flow path 4, an ink supply path 13, and piezoelectric ceramics 2 and 3 for changing the internal volume of the flow path and applying pressure to the ink, and the array 1 has nine ejecting devices 34. A droplet ejecting device 44 is configured.

The array 1 is manufactured by the following manufacturing method.

As shown in FIG. 5, first, a piezoelectric ceramic plate 2 having through-holes forming the ink flow path 4 as described above is made of a lead zirconate titanate (PZT) ceramic material having ferroelectric properties. , 3 are produced using injection molding. Thereafter, a degreasing process, a sintering process, polarization treatment in the thickness direction of the plate, electrode formation by electroless copper (or nickel) plating treatment, and electrode insulation treatment are performed. Then, as shown in the figure, the piezoelectric ceramic plates 2 and 3 are cut through a cutting process along the wavy line passing through the center of the through hole, and processed to remove excess electrodes attached to the top and bottom surfaces of the plates and process the top and bottom ends to improve flatness. get. At this time, an extrusion molding method may be used as the molding method, or holes may be made by machining in a piezoelectric ceramic plate that has been sintered in advance.

Similar piezoelectric ceramics can also be produced by using copper or nickel sputtering as an electrode forming method (it is preferable to tilt the axis of the hole and the parallel beam of metal atoms in order to form an electrode on the inner surface of the hole). Plates 2 and 3 are obtained. The upper piezoelectric ceramic plate 2 and the lower piezoelectric ceramic plate 3 thus obtained, the orifice plate 8 in which the orifice 10 corresponding to each ink flow path 4 was formed, and the ink supply path 13 corresponding to each ink flow path 4 were assembled. The piezoelectric ceramics 2 and 3 are connected to a bottom plate 12 on the lower surface of which is provided with wiring for electrically connecting the electrodes in the flow path and the driving LSI chip 16. They are joined as shown in FIG. 6 at a temperature sufficiently lower than the Curie temperature of the ceramic plates 2 and 3. Then, the driving LSI chip 16 is mounted to obtain the array 1.

Each array 1 is provided with an electrical circuit as shown in FIG. In this electric circuit, all electrodes 6d on the inner surface of the end through-hole 5 where the ink flow path 4 cannot be formed due to cutting are grounded. The electrodes 6a to 6c are each separately connected to the driving LSI chip 16, and the clock line 18, data line 20, voltage line 22, and ground line 24 are also connected to the driving LSI chip 16.

The ink flow path 4 is divided into non-adjacent groups A, B, and C as shown in FIG. Drive the group in succession. Data in a multi-bit word format appearing on the data line 20 determines which ink channel 4 in each group should be activated, and the electrodes of the channel in the group selected by the circuit of the driving LSI chip 16 The voltage V of the voltage line 22 is applied to the voltage line 6. At this time, the electrodes 4 of the ink channels 4 of the same group that are not activated and the electrodes 8 of all the ink channels 4 belonging to other groups are grounded. As a result, an electric field is applied between the electrodes of the selected ink flow path 4 and each of the six adjacent ink flow paths 4 in a direction perpendicular to the polarization direction of both piezoelectric ceramic plates 2 and 3. The channel walls of both piezoelectric ceramic plates 2 and 3 are deformed by the piezoelectric thickness shear effect, changing the volume of the selected ink channel 4. Therefore, all ink flow paths 4 in each group become operable.

3 and 4, according to predetermined print data,
The case where the injection device 34b is selected is shown, and FIG. 4 is a longitudinal sectional view taken along the line xx' in FIG. 3. The voltage V of the voltage line 22 is applied to the electrode 6b in the ink flow path 4b, and all the electrodes 6 in the flow path adjacent to the ink flow path 4b, including the other electrodes 6a and 6c, are grounded, and the piezoelectric ceramics 2b, 3b
, 2c, 3c and other piezoelectric ceramics 2 and 3 surrounding the ink flow path 4b, a driving electric field is applied in the direction of the arrow 32.

Since the driving electric field and the polarization direction are perpendicular to each other, the piezoelectric ceramic 2b is deformed due to the piezoelectric thickness shear effect.
, 3b, 2c, and 3c, all the walls of the piezoelectric ceramics 2 and 3 surrounding the ink flow path 4b deform into a dogleg shape toward the inside of the ink flow path 4b. Therefore, the volume of the ink flow path 4b decreases, and the ink 30 flows into the orifice 1.
It is injected from 0b. Further, when the voltage application is cut off and all the walls of the piezoelectric ceramics 2 and 3 surrounding the ink flow path 4b including the piezoelectric ceramics 2b, 3b, 2c, and 3c are returned to their original positions, the ink flow path at that time is As the volume of ink 4b increases, ink is replenished from the ink supply device 46 via the ink supply path 13b.

Note that, for example, if another injection device 34c is selected, the piezoelectric ceramics 2c, 3c, 2d, 3d
The walls of all the piezoelectric ceramics 2 and 3 surrounding the ink flow path 4c including the ink flow path 4c are deformed into a dogleg shape toward the inside of the ink flow path 4c, and the ink within the ink flow path 4c is jetted.

As described above, in the piezoelectric droplet ejecting device of this embodiment, the piezoelectric transducers for driving the nine ejecting devices 34 are connected to the two piezoelectric ceramic plates 2 and 3.
Since the structure of the array 1 is simplified, by assembling the array 1 or a large number of arrays 1, the number of manufacturing steps of the piezoelectric droplet ejecting device is reduced, and the manufacturing cost is also reduced. In addition, the number of ejecting devices 34 can be increased by crowding a large number of ink channels 4 made up of through holes in the piezoelectric ceramics 2 and 3;
can be made smaller and the resolution of printing can be increased. For example, when 96 ink channels 4 having the same dimensions as in this embodiment are arranged at the same center distance (8 vertically x 12 horizontally), the outer dimensions of the array 1 may be 10 mm x 6 mm x 5 mm or less.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be modified in many ways without departing from the spirit thereof. For example, the arrangement of the ink channels 4 does not need to be a geometric shape with a six-fold axis of symmetry;
It may be a 3rd or 4th order axis of symmetry. In the case of a geometric shape having a four-fold symmetry axis as shown in FIG. 7, the ink flow path 4 only needs to be divided into two groups, A and B, and the design of the drive circuit becomes simple. Further, the through hole forming the ink flow path does not need to have a constant inner diameter; for example, as shown in FIG.
3 and use the thick part as the ink flow path 4, the number of parts can be further reduced. At this time, if the electrodes 6 are also formed on the ceiling and bottom of the ink flow path 4 of the piezoelectric ceramics 2 and 3 as shown in the figure, the piezoelectric vertical effect of the ceiling and bottom will also be deformed during driving, so it will be reduced. It can be driven by voltage. Furthermore, the cross section of the ink flow path 4 does not have to be circular and may be oval or polygonal. For example, if it is hexagonal as shown in FIG. 9, the thickness of the walls of the piezoelectric ceramics 2 and 3 that separate the ink flow path 4 will be constant. Since an ideal electric field distribution is obtained, the driving voltage is reduced.

[0019]

As is clear from the above explanation, the piezoelectric droplet ejecting device of the present invention has a simpler structure and requires fewer manufacturing steps than the conventional device, so that manufacturing costs are reduced. Furthermore, it is easy to increase the degree of integration of the ink channels, making it possible to downsize the ejecting device and improve the resolution of printing.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an array forming part of a piezoelectric droplet ejection device.

FIG. 2 is a longitudinal cross-sectional view along line x-x' of the array of FIG. 1;

FIG. 3 is a diagram showing a state in which the array is provided with an electric circuit.

FIG. 4 is a longitudinal cross-sectional view along line x-x' of the array of FIG. 3;

FIG. 5 is a front view of a piezoelectric ceramic plate.

FIG. 6 is a perspective view showing the assembly process of the array.

FIG. 7 is a cross-sectional view of an array forming part of a piezoelectric droplet ejecting device in another embodiment.

FIG. 8 is a longitudinal cross-sectional view of an array forming part of a piezoelectric droplet ejecting device in another embodiment.

FIG. 9 is a cross-sectional view of an array forming part of a piezoelectric droplet ejecting device in another embodiment.

FIG. 10 is a perspective view showing the main parts of an inkjet printer equipped with a piezoelectric droplet ejecting device.

[Explanation of symbols]

2 Piezoelectric ceramics (upper piezoelectric ceramics plate) 3
Piezoelectric ceramics (lower piezoelectric ceramics plate) 4
Ink flow path 26 Polarization direction 28 Polarization direction 34 Injection device

Claims (1)

[Claims] 1. A piezoelectric droplet ejecting device comprising a number of ejecting devices that eject ink in an ink flow path by changing the volume of the ink flow path using a piezoelectric transducer, wherein the piezoelectric transducer comprises: A piezoelectric droplet ejecting device characterized in that the device is made of a piezoelectric material having a plurality of ink channels penetrating in a direction parallel to a polarization direction, and a driving electric field direction is perpendicular to the polarization direction.