JP2964672B2 - Piezoelectric droplet ejector - Google Patents

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 apparatus, and more particularly, to a piezoelectric droplet ejecting apparatus utilizing deformation of a piezoelectric transducer.

[0002]

2. Description of the Related Art Conventionally, a printer head using a piezoelectric ink jet has been proposed in recent years. this is,
By changing the volume of the ink flow path by the dimensional displacement of the piezoelectric actuator, the ink in the ink flow path is ejected from the orifice when the volume is reduced, and the ink is introduced into the ink flow path from the other valve when the volume is increased. This is called the 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.

[0003]

However, in the conventional piezoelectric liquid droplet ejecting apparatus, since one ejecting apparatus uses one piezoelectric actuator, a large number of ejecting liquids are required to perform printing with high resolution over a wide range. If the devices are arranged densely, there is a problem that the structure is complicated, the number of manufacturing steps is large, and the cost is high.

SUMMARY OF THE INVENTION 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 apparatus which has a simple structure, is inexpensive to manufacture, and has a high resolution. I do.

[0005]

In order to achieve this object, a piezoelectric droplet ejecting apparatus according to the present invention uses a piezoelectric transducer to change the volume of an ink passage to eject ink in the ink passage. Equipped with many devices,
The piezoelectric transducer is a piezoelectric material having a plurality of ink flow paths penetrating and extending in a direction parallel to the polarization direction, and the driving electric field direction is configured to be perpendicular to the polarization direction. Preferably, the piezoelectric transducer
Are plate-shaped, polarized in the thickness direction, and
The plurality of ink flow paths are configured to penetrate in the direction
You. Further, the piezoelectric transducer has a polarization direction
The two opposite piezoelectric materials are joined together.
The plurality of ink flow paths penetrate the piezoelectric materials.
It is configured to extend. Further, the ink flow path is
With multiple axes of symmetry along the plane of the
To be arranged in a geometrical figure.

[0006]

According to the piezoelectric droplet ejecting apparatus of the present invention having the above structure, the piezoelectric material around the ink flow path corresponding to the predetermined ejecting apparatus deforms the piezoelectric thickness-shear effect, and Is ejected from the ejection device.

[0007]

FIG. 1 shows an embodiment of the present invention.
This will be described in detail with reference to FIGS. FIG. 10 is a diagram showing a main part of an ink jet printer equipped with a piezoelectric liquid drop ejecting apparatus according to one embodiment of the present invention. A platen 36 supporting a paper 58 is rotatable on a frame 40 by a shaft 38. It is mounted and driven by a motor 42. Piezoelectric droplet ejecting device 4 facing platen 36
4 are provided. The piezoelectric droplet ejecting device 44 is mounted on a carriage 48 together with the ink supply device 46. The carriage 48 is slidably supported by two guide rods 50 arranged in parallel with the axis of the platen 36, and is coupled with a timing belt 56 wound around a pair of pulleys 52. Then, one pulley 52 is rotated by a motor 54, and the carriage 48 is moved along the platen 36 by sending the timing belt 56.

FIG. 1 is a cross-sectional view of an array 1 used in the piezoelectric droplet ejecting apparatus 44. FIG. 2 is a longitudinal sectional view of the array 1 (XX ′ longitudinal sectional view in FIG. 1). Array 1 performs polarization processing in the direction of arrow 26,
And a center hole distance of 0.75m with a 0.5mm diameter through hole
1.25 mm thick upper piezoelectric ceramic plate 2 arranged in a geometrical figure having a six-fold symmetry axis as shown in FIG.
1, a polarization process is performed in the direction of arrow 28, and a through-hole having a diameter of 0.5 mm is provided with a six-fold symmetry axis as shown in FIG. The lower piezoelectric ceramic plate 3 having a thickness of 1.25 mm arranged in a geometrical shape is joined via an adhesive layer 14. Here, the ink flow path 4 formed by the through hole has a circular cross section with a diameter of 0.5 mm, and the flow path length is 2.
The width of the walls of the piezoelectric ceramics 2 and 3 which divide the flow path is 5 mm and the minimum width is 0.25 mm. All ink channels 4
An electrode 6 is formed on the inner wall surface of the substrate, and the surface of the electrode 6 is further subjected to insulation treatment for insulation from ink. Also,
An orifice plate 8 having an orifice 10 corresponding to each ink flow path 4 on an upper surface of the upper piezoelectric ceramic plate 2, and an ink supply device corresponding to each ink flow path 4 on a lower surface of the lower piezoelectric ceramic plate 4. The bottom plate 12 having an ink supply passage 13 connected to 46 is joined. The ejection device 34 is an orifice 1 for ejecting a droplet.
0, 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. The droplet ejection device 44 is configured.

The array 1 is manufactured by the following manufacturing method.

As shown in FIG. 5, a piezoelectric ceramic plate 2 having a through-hole for forming the ink flow path 4 as described above is first made of a lead zirconate titanate (PZT) -based ceramic material having ferroelectricity. (3) is produced by injection molding. Thereafter, a degreasing step, a sintering step, a polarization treatment in the thickness direction of the plate, an electrode formation by electroless copper (or nickel) plating treatment, and an electrode insulation treatment are performed. Then, as shown in the figure, the piezoelectric ceramic plates 2 and 3 are subjected to a cutting process along a wavy line passing through the center of the through hole and upper and lower end surface processing for removing extra electrodes attached to the upper and lower surfaces of the plate and improving flatness. Get. At this time, an extrusion molding method may be used as a molding method, or a hole may be formed by machining a piezoelectric ceramics plate which has been sintered in advance.

Similar piezoelectric ceramics can be obtained by using a sputtering method of copper or nickel (preferably inclining an axis of a hole and a parallel beam of metal atoms to form an electrode on the inner surface of the hole) as an electrode forming method. 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 orifices 10 corresponding to each ink flow path 4 are formed, and the ink supply path 13 corresponding to each ink flow path 4 are formed. The bottom plate 12 formed and provided on the lower surface with wiring for electrically connecting the electrodes in the flow path and the driving LSI chip 16 is connected to the piezoelectric ceramics 2 and 3 so that the polarization of the piezoelectric ceramics 2 and 3 does not decrease. The joining is performed at a temperature sufficiently lower than the Curie temperature of the ceramic plates 2 and 3 as shown in FIG. Then, the array 1 is obtained by mounting the driving LSI chip 16.

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

The ink flow path 4 is divided into groups A, B and C which are not adjacent to each other as shown in FIG. 1, and a continuous clock pulse supplied from the clock line 18 is used for the A, B and C. Drive the group continuously. The data in the multi-bit word format appearing on the data line 20 determines which of the ink channels 4 of each group should be activated, and the electrodes of the channels of the group selected by the circuit of the driving LSI chip 16. 6, the voltage V of the voltage line 22 is applied. At this time, the electrodes 4 of the ink channels 4 of the same group that are not operated and the electrodes 8 of all the ink channels 4 belonging to other groups are grounded. As a result, an electric field was applied between the electrodes of the six ink flow paths 4 adjacent to the selected ink flow path 4 in a direction perpendicular to the polarization directions of the two piezoelectric ceramic plates 2 and 3, and the electric field was applied. The flow path walls of the two piezoelectric ceramic plates 2 and 3 are deformed by the piezoelectric thickness-shear effect, and change the volume of the selected ink flow path 4. Accordingly, all the ink flow paths 4 can be operated in each group.

FIG. 3 and FIG. 4 show the relationship between predetermined print data and
FIG. 4 is a vertical sectional view taken along the line xx ′ of FIG. 3 showing a case where the injection device 34b is selected. 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, 3
A driving electric field is applied in the direction of arrow 32 to the walls of all the piezoelectric ceramics 2 and 3 surrounding the ink flow path 4b including b, 2c and 3c.

Since the driving electric field and the polarization direction are orthogonal to each other, the piezoelectric ceramics 2
The walls of all the piezoelectric ceramics 2 and 3 surrounding the ink flow path 4b, including the ink flow paths b, 3b, 2c and 3c, are deformed into a V shape from the inside of the ink flow path 4b. Therefore, the volume of the ink flow path 4b is reduced, and the ink 30 is ejected from the orifice 10b. When the application of the voltage is interrupted and the walls of all 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 returned. 4b
The ink is replenished from the ink supply device 46 via the ink supply path 13b as the volume of the ink increases.

Incidentally, for example, when another injection device 34c is selected, the piezoelectric ceramics 2c, 3c, 2d, 3d
The walls of all of the piezoelectric ceramics 2 and 3 surrounding the ink flow path 4c are deformed into the ink flow path 4c in a V shape, and the ink in the ink flow path 4c is ejected.

As described above, in the piezoelectric droplet ejecting apparatus of the present embodiment, the piezoelectric transducers for driving the nine ejecting apparatuses 34 are two piezoelectric ceramic plates 2 and 3.
Since the structure of the array 1 is simplified, by assembling the array 1 and a large number of the arrays 1, the number of manufacturing steps of the piezoelectric droplet ejecting apparatus is reduced, and the manufacturing cost is also reduced. In addition, the number of ejecting devices 34 is increased by densely arranging a large number of ink flow paths 4 each having a through hole in the piezoelectric ceramics 2 and 3.
Can be reduced in size and the printing resolution can be increased. For example, the outer dimensions of the array 1 when the ink channels 4 having the same dimensions as those of the present embodiment are arranged at 96 (8 × 12) at the same center distance may be 10 mm × 6 mm × 5 mm or less.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the arrangement of the ink flow paths 4 does not need to be a geometrical figure having a six-fold symmetry axis.
A symmetric axis such as three or four may be used. In the case of a geometrical figure having a four-fold symmetry axis as shown in FIG. 7, the ink flow paths 4 need only be divided into two groups A and B, and the design of the drive circuit is simplified. 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 if the thick portion is the ink flow path 4, the number of components can be further reduced. At this time, if the electrodes 6 are also formed on the ceiling and the bottom of the ink flow path 4 of the piezoelectric ceramics 2 and 3 as shown in FIG. It can be driven by voltage. The cross section of the ink flow path 4 does not need to be circular but may be elliptical or polygonal. For example, when the ink flow path 4 is formed in a hexagonal shape as shown in FIG. Thus, an ideal electric field distribution is obtained, so that the driving voltage is reduced.

[0019]

As is apparent from the above description, the piezoelectric droplet ejecting apparatus of the present invention can be manufactured by injection molding or piezoelectric material.
Can be manufactured by drilling holes in the
As a result, the manufacturing cost is reduced because the structure is simple and the number of manufacturing steps is small as compared with the related art. Also, on the plane of the piezoelectric material
Along with this, it is possible to form a large number of ink channels
Therefore, it is easy to increase the degree of integration of the ink flow path, and it is possible to reduce the size of the ejection device and improve the printing resolution.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an array constituting a part of a piezoelectric droplet ejecting apparatus.

FIG. 2 is an x-x 'longitudinal sectional view of the array of FIG.

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

FIG. 4 is an x-x ′ longitudinal sectional view of the array of FIG. 3;

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

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

FIG. 7 is a cross-sectional view of an array constituting a part of a piezoelectric droplet ejecting apparatus according to another embodiment.

FIG. 8 is a vertical cross-sectional view of an array constituting a part of a piezoelectric droplet ejection apparatus according to another embodiment.

FIG. 9 is a cross-sectional view of an array constituting a part of a piezoelectric droplet ejecting apparatus according to another embodiment.

FIG. 10 is a perspective view showing a main part of an ink jet printer equipped with a piezoelectric droplet ejecting apparatus.

[Explanation of symbols]

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

Continuation of the front page (56) References JP-A-2-263650 (JP, A) JP-A-2-150355 (JP, A) JP-A-63-252750 (JP, A) JP-A-63-247051 (JP) (A) JP-A-3-256746 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41J 2/045 B41J 2/055 B41J 2/16

Claims (4)

(57) [Claims] 1. A piezoelectric liquid drop ejecting apparatus including a plurality of ejecting apparatuses for ejecting ink in an ink flow path by changing a volume of an ink flow path using a piezoelectric transducer, wherein the piezoelectric transducer comprises: A piezoelectric liquid droplet ejecting apparatus, comprising: a piezoelectric material having a plurality of ink flow paths extending therethrough in a direction parallel to a polarization direction, wherein a driving electric field direction is perpendicular to the polarization direction. 2. The piezoelectric transducer has a plate shape.
And polarized in the thickness direction, and
A plurality of ink passages are penetrated.
Item 2. The piezoelectric droplet ejecting apparatus according to Item 1. 3. The method according to claim 2, wherein the piezoelectric transducer has a polarization direction.
Is obtained by joining two opposite piezoelectric materials.
The plurality of ink flow paths penetrate the piezoelectric materials.
3. The piezoelectric liquid according to claim 2, wherein the piezoelectric liquid extends.
Drop ejection device. 4. The piezoelectric transducer according to claim 1, wherein
Geometry with multiple axes of symmetry along the plane of the
2. The pressure as claimed in claim 1, wherein
Electric droplet ejector.