JPH04341851A - Piezoelectric ink jet printer head - Google Patents

Abstract

PURPOSE:To simplify a structure and improve a resolving power in printing by a method wherein a piezoelectric actuator is provided over a plurality of jetting devices, and either inner positive electrode layers or inner negative electrode layers are divided to have a ratio of 1:1 to the two or more jetting devices. CONSTITUTION:An array 30 used for a piezoelectric ink jet printer head comprises a channel body 34 for forming three ink channels 32a-32c; a laminate piezoelectric element 38 securely bonded to the channel body 34; an orifice plate 36 securely bonded to the channel body 34 on the side opposite to the piezoelectric element 38 and having orifices 37a-37c; and a deformation restraining member 33 made of an elastic material and securely bonded on the side opposite to the ink channels 32a-32c. The laminate piezoelectric element 38 is so constructed that piezoelectric ceramics layers 40, inner negative electrode layers 42, and divided inner positive electrode layers 44a-44c having a ratio of 1:1 to the channels 32a-32c are laminated by a plurality of layers, respectively. In this manner, a resolving power in printing is improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric inkjet 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, printer heads using piezoelectric inkjet have been proposed. This is a drop-on-demand system that changes the volume of the ink chamber by dimensional displacement of a piezoelectric actuator, ejects ink inside the ink chamber when the volume decreases, and introduces ink into the ink chamber when the volume increases. It is called a 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.

However, since such piezoelectric inkjet printer heads use one piezoelectric actuator for one ejecting device, a large number of ejecting devices must be arranged closely in order to print over a wide area with high resolution. However, the problem was that the structure was complicated, required many man-hours to manufacture, and was expensive. Furthermore, because the dimensions of the piezoelectric actuator cannot be made too small due to processing constraints, it is difficult to miniaturize each injection device, which also poses a problem in that resolution is restricted.

In order to solve these problems, the same applicant previously proposed the configuration described in the specification and drawings attached to the application of Japanese Patent Application No. 2-75858. This is made up of alternating layers of piezoelectric ceramic layers and internal electrode layers, and at least one of the internal positive electrode layer and the internal negative electrode layer constituting the internal electrode layer is connected to a plurality of injection devices. By installing a piezoelectric actuator divided to correspond to multiple injection devices across multiple injection devices, the structure is simple and manufacturing costs are low, and high resolution and low voltage drive are achieved. This piezoelectric inkjet printer head is
For example, it has a structure as shown in FIG.

The laminated piezoelectric element 38 has three piezoelectric active parts 46a, 46b, 46c and four piezoelectric inactive parts 48 due to the above-described structure. Ink channel body 3
4 is joined to the laminated piezoelectric element 38 at the piezoelectric inactive portion 48, and has an orifice 37a on the opposite side.
, 37b, 37c are joined together. Here, an external negative electrode 52 and an external positive electrode 54
When a driving voltage is applied between a and a, the piezoelectric active portion 46a extends in the thickness direction as shown in the figure to reduce the volume of the ink channel 32a and eject droplets 39 from the orifice 37a. Therefore, the laminated piezoelectric element 38 has a plurality of injection devices 70a, 70
It works as a piezoelectric actuator for parts b and 70c, and has a simple structure with few components. Furthermore, since a laminated piezoelectric element with divided internal electrodes is used as the actuator, high resolution and low voltage driving are achieved.

[0006]

However, in the piezoelectric ink jet printer head described above, as shown in FIG. 7, the displacement of the piezoelectric active portion 46a is not only in the direction of the ink channel 32a but also in the opposite direction. It turns out that there is only so much. That is, this piezoelectric inkjet printer head has a problem in that it can only eject droplets with half the energy efficiency.

The present invention has been made to solve the above-mentioned problems, and provides a piezoelectric inkjet printer head that has a simple structure, low manufacturing cost, high resolution, and is efficiently driven at low voltage. The purpose is to provide.

[0008]

[Means for Solving the Problems] In order to achieve this object, the piezoelectric inkjet printer head of the present invention has piezoelectric ceramic layers and internal electrode layers alternately laminated to change the volume of the ink chamber of the ejecting device. A piezoelectric actuator is made of It is provided across the ejecting device, and has means for restraining deformation of a portion of the piezoelectric actuator on the side opposite to the ink chamber.

[0009]

[Operation] According to the piezoelectric inkjet printer head of the present invention having the above configuration, a driving voltage is applied only between the internal electrode layers corresponding to a predetermined ejecting device of the piezoelectric actuator provided across a plurality of ejecting devices. Then, a portion of the piezoelectric ceramic layer located between the internal electrode layers is locally deformed, and ink is ejected from the corresponding ejector.

0010

[Example] An example embodying the present invention is shown in FIGS. 1 to 6.
This will be explained in detail with reference to . For convenience of explanation, parts that are the same or equivalent to those of the conventional example will be given the same reference numerals.

FIG. 6 is a diagram showing the main parts of an inkjet printer equipped with a piezoelectric inkjet printer head, which is an embodiment of the present invention, in which 11 is paper;
is the platen. This platen 10 is rotatably attached to a frame 13 by a shaft 12 and is driven by a motor 14. A piezoelectric inkjet printer head 15 is provided opposite the platen 10.

Piezoelectric inkjet printer head 15
is placed on the carriage 18 together with the ink supply device 16. The carriage 18 is slidably supported by two guide rods 20 arranged parallel to the axis of the platen 10, and is connected to a timing belt 24 wound around a pair of pulleys 22. One of the pulleys 22 is rotated by the motor 23, and the timing belt 24 is fed, thereby moving the carriage 18 along the platen 10.

FIG. 1 is a cross-sectional view of an array 30 used in the piezoelectric inkjet printer head 15. As shown in FIG. This array 30 consists of a channel body 3 in which three ink channels 32a, 32b, and 32c are formed, each having a width of 1.2 mm and a length (in the direction perpendicular to the plane of the paper) of 15 mm.
4, a laminated piezoelectric element 38 fixed to the channel body 34, an orifice plate 36 having an orifice 37 also fixed to the channel body 34 on the side opposite to the laminated piezoelectric element 38, and the laminated piezoelectric element 38. A deformation restraining member 33 made of metal or ceramic having a high modulus of elasticity is fixed to the side facing the ink channels 32a to 32c. The ink channels 32a to 32c constitute an ink chamber.

The laminated piezoelectric element 38 includes a piezoelectric ceramic layer 40 having a piezoelectric/electrostrictive effect, an internal negative electrode layer 42,
Internal positive electrode layers 44a, 44b, 4 are divided in one-to-one correspondence with the ink channels 32a to 32c and have a width of 1.0 mm in the array direction 31.
4c are laminated to have a thickness of approximately 0.5 mm. Then, the laminated piezoelectric element 38 has an internal negative electrode layer 42
and the internal positive electrode layers 44a to 44c, and has a width of 1.0 mm in the array direction.
46b, 46c and both internal electrode layers 42, 44a to 44c
It has a piezoelectric inactive portion 48 that is not sandwiched between the two. The piezoelectric ceramic layer 40 is made of a ferroelectric lead zirconate titanate (PZT) ceramic material with a thickness of 40 μm, and is polarized in the stacking direction. Each piezoelectric active part 4 of the piezoelectric ceramic layer 40 in the figure
Arrows shown in 6a to 46c indicate polarization directions. The internal negative electrode layer 42 and the internal positive electrode layer 44a~
44c is made of Ag-Pd metal material and has a thickness of about 2
It is μm.

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

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

As shown in FIG. 4, first, the ink channels 32a to 3 are formed on the upper surface of the piezoelectric ceramic layer 40.
internal positive electrode layers 44a to 44c divided into three in one-to-one correspondence to electrode 2c, and each electrode lead-out portion 45a,
45b and 45c are formed by screen printing to create a green sheet 50. Further, on the upper surface of the piezoelectric ceramic layer 40, an internal negative electrode layer 42 and its electrode extraction portion 43 are formed by screen printing to create a green sheet 51. And both green sheets 50
, 51 are laminated alternately, and a green sheet (not shown) without an internal electrode layer is placed on the upper surface of the piezoelectric ceramic layer 40, and the whole is heated and pressed, and subjected to degreasing, sintering, etc. A laminated piezoelectric element 38 is obtained by performing necessary measures. The thus obtained laminated piezoelectric element 38
External negative electrode 52, external positive electrodes 54a, 54b, 5
Install 4c. Then, this laminated piezoelectric element 38 is
The external negative electrode 5 is immersed in an oil bath (not shown) filled with insulating oil such as silicone oil at about 30°C.
2.5 kV/m between 2 and the external positive electrodes 54a to 54c.
An electric field of about m is applied to perform polarization treatment. The laminated piezoelectric element 38 can be obtained by the above method.

Laminated piezoelectric element 38 thus obtained
As shown in FIG. 5, a channel body 34 having three ink channels 32 each having a width of 1.2 mm and a length of 15 mm, an orifice plate 36 having three orifices 37, and a deformation restraining member 33 are constructed as shown in FIG. The array 30 is constructed by assembling.

Array 30 is provided with electrical circuitry as shown in FIG. In this electric circuit, the negative electrode side of the driving power source 60 and the external negative electrode 52 of the laminated piezoelectric element 38 are grounded, and the positive electrode side of the driving power source 60 is connected to the laminated piezoelectric element via on/off switches 62a, 62b, and 62c. 38 external positive electrodes 54a to 54c. When the switches 62a to 62c are closed by a controller (not shown), a driving voltage is applied from the driving power source 60 between the internal negative electrode layer 42 and the internal positive electrode layer 44 located in the predetermined piezoelectric active parts 46a to 46c. .

The operation of the piezoelectric inkjet printer head 15 configured as described above will be explained.

When the controller closes the switch 62a, for example, according to predetermined printing data, a voltage is applied between the internal negative electrode layer 42 and the internal positive electrode layer 44a of the piezoelectric active part 46a, and the position between them is 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 due to the piezoelectric/electrostrictive longitudinal effect, thereby reducing the volume of the ink channel 32a. Then, the ink in the ink channel 32a is ejected from the orifice 37a in the form of droplets 39. Further, when the switch 62a is opened to cut off the voltage application and the piezoelectric active part 46a is returned to its original position, the ink supply device 16 is supplied from the ink supply device 16 via another valve (not shown) as the volume of the ink channel 32a increases at that time. Ink is replenished. Note that, for example, when the other switch 62b is closed, the piezoelectric active portion 46b is displaced and ink is ejected from the ink channel 32b.

That is, the array 30 of this embodiment includes the three ejection devices 7 of the piezoelectric inkjet printer head 15.
0a, 70b, and 70c, and one laminated piezoelectric element 38 constitutes the three injection devices 70a to 70c.
It functions as a piezoelectric actuator installed across the

FIG. 3 shows data obtained by measuring the deformation distribution 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 part 46, the piezoelectric active part 46 is displaced by about 90 nm in the conventional state without the deformation restraining member 33, but as in this embodiment, the piezoelectric active part 46 is deformed. When the restraining member 33 was provided, a displacement of about 160 nm was obtained. Thus, it can be seen that the product of the present invention has improved efficiency by about 1.8 times compared to the conventional product. From this result, it was found that the piezoelectric inkjet printer head 15 of this example required only a low driving voltage of 17 V to eject the droplets 39.

As described above, in the piezoelectric inkjet printer 15 of this embodiment, one laminated piezoelectric element 38 functions as a piezoelectric actuator for the three injection devices 70a to 70c.
By assembling a large number of piezoelectric inkjet printer heads 15, the structure of the piezoelectric inkjet printer head 15 is simplified, the number of manufacturing steps is reduced, and manufacturing costs are reduced. In addition to the fact that the piezoelectric actuator is a laminated piezoelectric element 38, a deformation restraining member 33 is fixed to the laminated piezoelectric element 38 to reduce unnecessary deformation, resulting in efficient deformation and a significant reduction in driving voltage. did it. Further, the laminated piezoelectric element 38 is formed by screen printing to form internal electrode layers 42 and 44.
Therefore, it is easy to make the widths of the piezoelectric active parts 46a to 46c and the piezoelectric inactive part 48 extremely small.
Printing resolution can be improved by downsizing. This makes it possible to realize a printer head that can print in a wide range with high resolution.

Further, the internal negative electrode layer 42 and the internal positive electrode layer 44 of the laminated piezoelectric element 38 of this embodiment are connected to the electrode extraction portion 4.
Since they are not exposed to the outside except for No. 3 and No. 45, there is no deterioration in insulation properties due to silver migration, etc., and there is an advantage that excellent durability and moisture resistance can be obtained.

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, in the embodiment, there are three injection devices 7.
Although one laminated piezoelectric element 38 is used as a piezoelectric actuator provided across 0a to 70c, for example, by employing an internal positive electrode layer 44 divided into a larger number of parts, it can be used to span an even larger number of injection devices. A piezoelectric actuator may also be provided.

Further, in the above embodiment, the internal positive electrode layer 44 was divided into one-to-one correspondence with each of the ink channels 32a to 32c, but the internal negative electrode layer 42 was divided into one to each ink channel 32a to 32c. Alternatively, both the internal positive electrode layer 44 and the internal negative electrode layer 42 may be divided into pairs corresponding to each other, or both the internal positive electrode layer 44 and the internal negative electrode layer 42 may be divided into one pair for each ink channel 32a to 32c.
It may be divided so that there is a one-to-one correspondence. That is, it is sufficient that at least one of the positive and negative internal electrode layers is divided so as to correspond to each of the ink channels 32a to 32c on a one-to-one basis.

Furthermore, the deformation restraining member 33 need not be a single one, and a plurality of deformation restraining members 33 may be provided corresponding to the piezoelectric active portions 46.

Furthermore, even if the driving method is to apply a driving electric field to the piezoelectric active part 46 in the direction opposite to the polarization direction and drive the piezoelectric active part 46 in a direction in which the thickness of the piezoelectric active part 46 is generally reduced, the thickness of the piezoelectric active part 46 on the side opposite to the ink channel 32 may be reduced. If the displacement is restrained, the same effects as in the above embodiment can be obtained.

[0031]

[Effect of the invention] As is clear from the detailed description above,
According to the piezoelectric inkjet printer head of the present invention, the piezoelectric actuator is provided across the plurality of ejecting devices, and one of the internal positive electrode layer and the internal negative electrode layer is connected to the plurality of ejecting devices. Since the parts are divided one to one, the structure is simplified, the number of manufacturing steps is reduced, and the manufacturing cost is reduced. Furthermore, it is easy to form the pattern of the internal electrode layer by dividing it finely to reduce the area of the locally displaced portion of the laminated piezoelectric element, thereby making it possible to downsize the injection device and improve the resolution of printing. Further, since a means for restraining the deformation of the piezoelectric active portion on the side opposite to the ink chamber is provided, efficient deformation can be obtained and the driving voltage can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an array forming part of a piezoelectric inkjet printer head.

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

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

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

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

FIG. 6 is a perspective view showing the main parts of an inkjet printer equipped with a piezoelectric inkjet printer head.

FIG. 7 is a cross-sectional view of an array forming part of a conventional droplet ejecting device.

[Explanation of symbols]

15 Piezoelectric inkjet printer head 32
Ink channel (ink chamber) 33 Deformation restraint member 38 Laminated piezoelectric element (piezoelectric actuator) 40
Piezoelectric ceramic layer 42 Internal negative electrode layer 44 Internal positive electrode layer 70 Injection device

Claims (1)

[Claims] 1. A piezoelectric type comprising a plurality of ejecting devices that change the volume of an ink chamber by the action of a piezoelectric actuator formed by alternately laminating piezoelectric ceramic layers and internal electrode layers, and eject ink within the ink chamber. In the inkjet printer head, the piezoelectric actuator is provided across a plurality of ejection devices, and at least one of an internal positive electrode layer and an internal negative electrode layer that constitute the internal electrode layer is connected to the plurality of ejecting devices. A piezoelectric inkjet printer head, characterized in that the piezoelectric inkjet printer head is divided one-to-one with respect to the ejecting device, and has means for restraining deformation of a portion of the piezoelectric actuator on the side opposite to the ink chamber.