JP3201109B2 - Inkjet head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-demand type ink jet head which flies ink droplets in response to input of print data and forms dots on recording paper using the ink droplets.

[0002]

2. Description of the Related Art An on-demand type ink jet head which ejects ink droplets from a plurality of nozzles in accordance with input information and outputs characters and figures has a low noise, a low running cost and a high print quality recording on plain paper or recycled paper. It is superior to other methods in that it can write.

In particular, devices using a piezoelectric element as a driving source for ink ejection have excellent durability and responsiveness, and are widely used as output devices for personal computers and the like.

In a conventional ink jet head described in Japanese Patent Publication No. 2-51734, a very thin vibration plate is bonded to an ink chamber forming substrate having a plurality of flow grooves formed therein to seal the grooves. Then, a chip of a piezoelectric element is mounted on the outer surface of the vibration plate corresponding to the ink chamber, and a unimorph actuator is constituted by the vibration plate and the piezoelectric element.

In the ink jet head described in Japanese Patent Application Laid-Open No. 5-97437, as a technique for forming an array of piezoelectric elements at a higher density, a piezoelectric element and a diaphragm are fired by using a ceramic material. A method of integrally joining has been proposed.

The present inventors have further improved and developed a method of integrally joining a piezoelectric element, a vibrating plate, and an ink chamber forming plate having a partition partitioning the ink chamber by firing using a ceramic material. ing. In such an integrated firing type ink jet recording head, there is no need to process and form the piezoelectric elements to a predetermined size and paste each of them with an adhesive. Simplifies the assembly process.

Further, since the ink chamber forming substrate having a very fine structure and the thin vibration plate are firmly joined by firing, an actuator having excellent ink sealing properties and ink corrosion resistance can be formed.

[0008]

However, in the above-described integral firing type ink jet recording head, since the piezoelectric element contracts when the piezoelectric element is fired, warping and residual stress are generated in the diaphragm, and voltage is applied to the piezoelectric element. In this case, there is a problem that the displacement amount of the unimorph actuator when the voltage is applied is reduced, and a problem that the diaphragm is broken by a stress generated by driving the piezoelectric element.

Further, since the ink chambers are arranged at a high density, the partition walls of the ink chambers are deformed by the ink pressure generated in the adjacent ink chambers, and the adjacent ink chambers adversely affect each other, so that ink droplets are formed. There is also a problem that the discharge state changes.

In order to solve these problems, a groove penetrating the diaphragm and reaching the partition wall was formed to take measures to relieve stress and reduce coupling between adjacent members. When repeated, the grooves propagated as cracks, causing a problem that the partition walls were broken.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problem, and an object of the present invention is to provide an ink jet device which discharges a sufficient amount of ink droplets at a low voltage, has a constant discharge of ink droplets, and has excellent durability. The purpose is to provide a head.

[0012]

According to the present invention, there is provided an ink jet head comprising: an ink chamber forming substrate on which a partition for partitioning a plurality of ink chambers is formed; and one surface of the ink chamber forming substrate is sealed. A diaphragm in which a piezoelectric element is formed corresponding to the ink chamber, and a sealing substrate for sealing the other surface of the ink chamber forming substrate, wherein the piezoelectric element is deformed to deform the diaphragm, An ink jet head for ejecting ink droplets from a nozzle communicating with the ink chamber by increasing ink pressure in the ink chamber corresponding to a piezoelectric element, wherein the piezoelectric element, the vibration plate, the ink chamber forming substrate, The sealing substrate is integrally formed by firing ceramics, and is characterized in that a groove is provided at a depth penetrating the diaphragm and the partition wall and reaching the sealing substrate. To.

[0013]

According to the above structure of the present invention, since the groove is formed to have a depth penetrating the diaphragm and the partition wall and reaching the sealing substrate, the interaction between adjacent ink chambers can be made as small as possible.
Also, no crack develops from the tip of the groove with repeated driving.

Further, since the diaphragm, the partition and the sealing substrate are integrally formed by firing the ceramics, it is possible to form a groove crossing the substrate.

Further, by forming the grooves, the residual stress generated by the firing is reduced, and the displacement of the diaphragm and the durability of the diaphragm can be improved.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a view showing a main part of an ink jet head according to the present invention, and is a cross-sectional view taken along a plane perpendicular to the ink flow direction of an ink chamber 4. 3 shows a shape of a groove 10 that reaches a sealing substrate 5 through a partition 30 that partitions the chamber 4. The groove 10 is formed by laser processing. FIG. 2 is an external perspective view showing the entire ink jet head of the present invention, which is an ink jet head 100 using three actuator units 50 each having 16 nozzles arranged in two vertical columns and a flow path unit 60. The number, the number of columns, and the configuration of the unit are not limited to any combination.

FIG. 3 is an exploded perspective view of the entire ink jet head according to the present invention.
0, a plurality of ink chambers 4 corresponding to the vibration plate 2 and the piezoelectric element 1
Actuator unit 50 constituted by the ink chamber forming substrate 3 having the above and the sealing substrate 5, the ink supply section forming member 6 having a plurality of ink supply ports 6a, and the ink reservoir chamber forming member 7 having the ink reservoir chamber 7a , A nozzle unit 8 having a plurality of nozzles 8a, and a channel unit 60, and both units are joined by an adhesive.

FIG. 8 is an enlarged view of a portion where the groove 10 is formed. The vibration plate 2 is joined on the ink chamber forming substrate 3 so as to seal the ink chamber 4 partitioned by the partition wall 30,
The lower electrode 20, the piezoelectric element 1, and the upper electrode 21 are stacked on the upper surface of the vibration plate 2. The piezoelectric element 1 has an upper electrode 21
The piezoelectric element 1 is individually driven by applying a drive voltage to each of the lower electrodes 20, with the upper electrode 21 serving as an electrode common to each of the piezoelectric elements 1. Ejects ink droplets. The insulating member 40 is filled between the adjacent piezoelectric elements 1, and the upper electrode 21 is continuously formed on the adjacent piezoelectric elements 1 on the upper surface thereof. Also, the diaphragm 2,
A groove having a depth reaching the sealing substrate 5 through the partition 30 is formed.

The actuator unit 50 is integrally formed by firing, and the steps will be described below. FIG. 7 shows the process. First, the vibrating plate 2, the ink chamber forming substrate 3, and the sealing substrate 5 are pressed in the state of a green sheet made of a ceramic material.
Sintering at a temperature of 1000 ° C. to 1000 ° C. (FIG. 7)
(A)). At this time, the ceramic material contains zirconium oxide as a main component. Next, the material of the lower electrode 20 is formed in a portion corresponding to the ink chamber 4 by printing, and baked (FIG. 7B). Finally, the material of the piezoelectric element 1 is similarly formed by printing and baked to finish (FIG. 7C).

In the actuator thus formed by integral firing, the ink chamber forming substrate 3 having a very fine structure and the thin vibration plate 2 are firmly joined by firing, so that the ink sealing property and the ink resistance are improved. In addition to being excellent in corrosiveness, there is an advantage that the manufacturing process is extremely simple since it is only necessary to apply and bake a paste-like electrode or piezoelectric element by a printing technique. However, on the other hand, there are some problems. First, since the method of forming the actuator is firing, the piezoelectric element 1
During firing, residual stress is generated due to the difference between the contraction rate of the piezoelectric element 1 and the contraction rate of the vibration plate 2 that is in close contact with the piezoelectric element, and the displacement as a unimorph actuator when a voltage is applied to the piezoelectric element 1 The point is that the amount decreases. Further, when the piezoelectric element 1 is driven, the generated stress due to the driving is added to the residual stress described above, and a considerable load is imposed on the diaphragm, and as a result, the problem that the diaphragm is destroyed is also caused. appear. Further, as a second problem, since the ink chambers 4 are arranged at a high density, it has been confirmed that crosstalk occurs via the partition walls.

In order to solve these problems, as shown in FIG. 4, a groove penetrating through the diaphragm 2 and reaching the partition wall 30 is provided to take measures to alleviate stress and reduce coupling between adjacent members. Was.

However, as described above, if the depth of the groove 10 is halfway through the partition 30, the piezoelectric element 1 is repeatedly driven to cause a crack from the tip of the groove 10 and a new problem that the partition 30 is broken. A point has occurred.

The breakage of the partition wall 30 caused by the cracks in the groove 10 causes a problem that stable discharge cannot be supplied. Therefore, the present invention solves the problem by the following method. That is, as shown in FIG.
0 is formed to a depth that reaches the sealing substrate 5 through the diaphragm 2 and the partition 30. As a result, since the tip of the groove 10 is in the sealing substrate which is not affected by the driving of the piezoelectric element 1, even if the piezoelectric element 1 is repeatedly driven, the groove 10 does not crack from the tip, and the partition wall 30 is broken. Will be spared. At this time, the groove 10 can be formed across the substrate because the diaphragm 2, the partition 30, and the sealing substrate 5 are integrally formed by firing the ceramic. Even when the diaphragm 2, the partition 30, and the sealing substrate 5 are formed by integrally firing ceramics having a different composition other than zirconium oxide, the groove can be processed, and the effects of the invention can be obtained. The same composition is preferable for joining.

On the other hand, when the vibration plate 2, the partition 30 and the sealing substrate 5 are bonded not by integral firing but by an adhesive, the adhesive force between the members becomes very weak. Processing of the groove becomes difficult. Further, in the bonding method using an adhesive, when the vibration plate 2, the partition wall 3, and the sealing substrate 5 are different members, it is difficult to further process the grooves.

In the ink jet head having such a configuration, the ink guided from an ink cartridge (not shown) passes through the ink introduction section 6b and the ink reservoir chamber 7a in FIG. 3, and reaches the ink chamber 4 from the ink supply port 6a. Then, the piezoelectric element 1 to which the voltage is applied is displaced,
By flexing the deformable diaphragm 2, the ink chamber 4
In response to this, the ink is supplied to the ink passage port 5a in the sealing substrate, the ink passage port 6c in the ink supply section forming member, and the ink passage port 7b in the ink reservoir chamber forming member.
And is ejected from the nozzle 8a to perform printing.

Next, an integral firing type ink jet head having a groove halfway through the partition will be described.

First, FIG. 4 is a diagram showing a cross section perpendicular to the ink flow direction of the ink chamber of the integrally fired ink jet head having a groove halfway along the side wall. FIG. 5 is a modified view when the piezoelectric element is driven in the structure of FIG. 4 (the modified state is indicated by a dotted line in the drawing). As can be seen from the drawing, when the piezoelectric element 1 is driven, not only the vibration plate 2 bends toward the ink chamber 4 but also the partition wall 30 is deformed so as to fall down toward the ink chamber 4 side. The falling of the partition wall 30 exerts a load on the groove 10, and a considerable pressure is applied to the tip of the narrow groove 10, and a crack is generated. (Grooves formed by laser processing have narrower tips.) Furthermore, the higher the rigidity of the substrate forming the partition wall 30, the more easily cracks are formed in the grooves. If the partition wall 30 is destroyed, it is foolish to be unable to supply a stable ink droplet ejection, which also reduces the durability of the head.

On the other hand, in the ink jet head of the present invention, as shown in FIG. 1 showing a cross section perpendicular to the ink flow direction of the ink chamber 4, the groove 10 is formed in the sealing substrate 5 which is not affected by the driving of the piezoelectric element 1. , The generation of a crack from the tip of the groove 10 due to the driving of the piezoelectric element 1 can be prevented.

Since the depth of the groove 10 reaches the sealing substrate 5, the adjacent ink chambers 4 are completely separated from each other, so that the occurrence of crosstalk via the partition 30 can be suppressed. It has become possible. FIG. 6 is a modified view when all the piezoelectric elements are driven in the structure of the ink jet head of the present invention. As can be seen from FIG. Is no longer directly received by the ink pressure that occurs, and the occurrence of crosstalk can be prevented.

Further, the residual stress generated at the time of firing the piezoelectric element 1, which could not be sufficiently relaxed until the depth of the groove 10 reaches the middle of the partition 30, can be sufficiently relaxed when the groove 10 reaches the sealing substrate 5. In addition, the displacement of the diaphragm 2 is improved. This makes it possible to discharge sufficient ink droplets even at a low voltage.

[0032]

According to the present invention, in a head in which a piezoelectric element, a vibrating plate, an ink chamber forming substrate, and a sealing substrate are formed by integrally firing ceramics, the head penetrates the vibrating plate and the partition to form a sealing substrate. By providing a groove having a depth that can be reached, an actuator having excellent durability can be formed. In addition, stable output independent of the ink ejection pattern is possible, and at the same time, the ink ejection efficiency is improved,
An inkjet head drivable at low voltage can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view taken along a plane perpendicular to an ink flow direction of an ink chamber according to an embodiment of the present invention.

FIG. 2 is a perspective view showing the appearance of the present invention.

FIG. 3 is an exploded perspective view showing the configuration of the present invention.

FIG. 4 is a cross-sectional view taken along a plane perpendicular to the ink flow direction of an ink chamber of an integrally fired inkjet head in which a groove is provided halfway of a partition.

FIG. 5 is a modified view when a piezoelectric element is driven in an integrally fired ink jet head in which a groove is provided halfway of a partition.

FIG. 6 is a modified view when the piezoelectric element is modified in the structure of the embodiment of the present invention.

FIG. 7 is a diagram showing a manufacturing process of the present invention.

FIG. 8 is a perspective view illustrating a groove forming portion according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2 Vibration plate 3 Ink chamber forming substrate 4 Ink chamber 5 Sealing substrate 5a Ink passage in sealing substrate 6 Ink supply part forming member 6a Ink supply opening 6b Ink introduction part 6c Ink passage in ink supply part forming member REFERENCE SIGNS LIST 7 Incremental chamber forming member 7a Incremental chamber 7b Ink passage port in incremental chamber forming member 8 Nozzle forming member 8a Nozzle 10 Groove 20 Lower electrode 21 Upper electrode 30 Partition wall 40 Insulating member 50 Actuator unit 60 Flow path unit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-329145 (JP, A) JP-A-4-345856 (JP, A) JP-A-61-266254 (JP, A) JP-A-62-162 111758 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B41J 2/045 B41J 2/055

Claims (3)

(57) [Claims] An ink chamber forming substrate on which a partition for partitioning a plurality of ink chambers is formed; and one surface of the ink chamber forming substrate is sealed, and a piezoelectric element is formed corresponding to each of the ink chambers. A vibrating plate, and a sealing substrate for sealing the other surface of the ink chamber forming substrate, and deforming the vibrating plate by deforming the piezoelectric element, the ink pressure in the ink chamber corresponding to the piezoelectric element. An ink jet head for ejecting ink droplets from nozzles communicating with the ink chamber, wherein the piezoelectric element, the vibration plate, the ink chamber forming substrate, and the sealing substrate are integrally formed by firing ceramics. An ink jet head, wherein a groove having a depth penetrating the diaphragm and the partition wall and reaching the sealing substrate is provided. 2. The ink jet head according to claim 1, wherein the sealing substrate is provided with an ink passage opening communicating with a nozzle for discharging ink droplets formed in the flow path unit. 3. The ink jet printer according to claim 1, wherein the flow path unit includes a nozzle forming member having a plurality of nozzles for ejecting ink droplets, an ink reservoir chamber forming member forming an ink reservoir chamber, and ink formed on the sealing substrate. 3. The ink supply unit according to claim 2, further comprising an ink supply port formed with an ink passage opening communicating with the passage opening and an ink supply opening communicating the ink reservoir chamber and the ink chamber. Ink jet head.