JP2850762B2 - 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 ink jet head for performing recording by applying ink droplets, and more particularly to a structure of a piezoelectric element as a pressure generating means of a high density multi-nozzle head.

[0002]

2. Description of the Related Art Conventionally, a piezoelectric element as a pressure generating means is displaced in a longitudinal direction to deform a wall corresponding to a pressure chamber of a vibration plate to pressurize ink in the pressure chamber and eject ink droplets from a nozzle. The ink jet head is disclosed in
It is disclosed in JP-A-8-119871.

FIG. 11 is a sectional view showing the structure of the ink jet head, and FIG. 12 is an enlarged sectional view of the nozzle portion.

In FIG. 11, an ink jet head includes a plurality of pressure chambers 300 having nozzles 302 and a nozzle plate 318 for emitting ink droplets according to the state of pressurization (applied voltage) of a piezoelectric element 304. Including. The piezoelectric element 304 having a rectangular cross section across the longitudinal axis is shown in FIG.
Expands and contracts along the longitudinal axis as represented by the arrow A shown in FIG. The movement of the piezoelectric element 304 along the longitudinal axis causes the leg 307, the viscoelastic material 308 juxtaposed to the leg 307, and the vibrating plate 310 to which the extra load is applied to the position shown in FIG. Coupling means 306 including
Is transmitted to the inside of the pressure chamber 300. Ink flows from the ink reservoir 312 into the pressure chamber 300 via a narrow inlet formed by the narrow opening 314 shown in FIG. The ink reservoir 312 is formed by a concave portion of the flow path plate 320. The ink supply tube 323 communicates with the ink reservoir 312 at one end as shown in FIG. Each piezoelectric element 304 is supported at its tip, and the plate member 326 as the piezoelectric element supporting means 328 is
A hole 324 for receiving a leg 307 attached to the tip of the piezoelectric element 304 is provided. Allow longitudinal movement of element 304.

[0005]

In the above-mentioned conventional ink jet head, in order to secure the displacement of the piezoelectric element 304 necessary for ejecting ink droplets, the length of the piezoelectric element 304 in the longitudinal direction must be secured accordingly. And the applied voltage had to be increased.

As means for solving this problem, Japanese Patent Application Laid-Open No.
Japanese Patent Application Laid-Open No. 90770/90
Japanese Patent Publication No. 115638 discloses a drop-on-demand ink jet recording head.

[0007] By using a laminated piezoelectric element as the piezoelectric element 304, the applied voltage is reduced, and the size of the head is reduced. However, in order to realize an ink jet head having a high-density nozzle arrangement of, for example, 300 dpi or more and 48 or more nozzles, the laminated piezoelectric elements are adhered to a vibration plate in a line at a high density and individually. Must be arranged, and the assembly process is not easy.

For this reason, in practice, a method of alternately arranging the ink flow paths including the nozzles and the pressure chambers, that is, by arranging the ink paths in a staggered manner, to loosen the arrangement pitch per row of the piezoelectric elements has to be adopted. I can't get it. However, assembling while arranging the divided piezoelectric elements corresponding to the positions of the staggered pressure chambers further complicates the assembling process, thereby increasing the cost of the ink jet head. There was a problem.

Therefore, an object of the present invention is to solve such a problem, and an object of the present invention is to provide an ink jet head which can be easily assembled and cost can be reduced.

[0010]

In order to achieve the above object, an ink jet head according to the present invention has an ink flow path having a plurality of nozzle holes for delivering ink and a plurality of pressure chambers for supplying ink to the nozzle holes. A vibration plate joined to a plate composed of an ink reservoir for holding ink to be supplied to the pressure chamber, and a wall of the pressure chamber which is instantaneously deformed at a position of the vibration plate facing the pressure chamber to apply pressure to the ink. An ink jet head for ejecting ink droplets onto a recording medium to form characters and figures by dots, wherein the pressure generating means includes at least one of the pressure generating means.
Forming a driving portion of the at least two rows provided center groove to central
Then, each drive unit is divided in the column direction, and the positions of the divided individual tips are arranged on the left and right sides of the nozzle.
So as to correspond to each of the plurality of pressure chambers, to center the groove
It is characterized in that a dividing groove is provided vertically .

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a top view of the flow path plate of the ink jet head according to the first embodiment of the present invention.

The flow path plate 100 is made of a photosensitive glass, a photosensitive resin, a resin mold, or the like.
The pressure chamber 3a and the pressure chamber 103b are both formed so as to be straight, and are arranged facing each other so as to communicate with the nozzle 101. For example, as shown in FIG. 1, if the total number of nozzles is 20, there are 10 ink flow paths 102,
102b are arranged in two rows and arranged so as to face each other.

Around the ink flow paths 102a and 102b, one U-shaped ink reservoir 105 is provided with pressure chambers 103a and 103 in each of the ink flow paths 102a and 102b.
3b is arranged so that the ink 113 can be supplied via the ink inlet.

FIG. 2 is a sectional view of the ink jet head according to the first embodiment of the present invention. FIG. 2 is a sectional view of the flow path plate 100 shown in FIG.

In this ink jet head, a nozzle plate 107 having a nozzle 101 having a diameter of about 50 μm is joined to the upper side of the flow path plate 100, and
The vibration plate 108 having a thickness of about 20 μm is joined. A plate in which the inflow plate 100, the nozzle plate 107, and the vibration plate 108 are stacked is supported by the housing 110. Alternatively, the nozzle plate 107 may be omitted, and the nozzle holes 101 may be formed in the flow path plate 100.

The ink reservoir 105 in the flow path plate 100
The ink 113 is supplied from an ink tank (not shown) provided outside through an ink supply pipe 106.

The pressure chamber 1 is provided on the lower surface of the vibrating plate 108.
A piezoelectric element 109 is joined to a position opposing to 03a and 103b via a projection 110a. The piezoelectric element 10
9, a center groove 111 is provided at the center thereof to form a U-shaped cross section, and the driving portions 112a and 112b formed by the center groove 111 have nozzles 101.
Perpendicular to the center groove 111 so as to correspond to each of the plurality of pressure chambers 103 arranged on the left and right of the
a, 119b (see FIG. 6). In addition, the piezoelectric element 109 has a driving portion 112a on the entire surface of the center groove 111.
And a common electrode 114 common to 112b.
Signal electrodes 115a and 115b are provided on the side surfaces of 12a and 112b opposite to the center groove 111, respectively.

The piezoelectric element 109 includes a projection 1 formed at the tip of each of the driving portions 112a and 112b of the piezoelectric element 109.
It is joined to the lower surface of the vibration plate 108 at a position facing the pressure chamber 103 via a spacer 10a or a spacer.

Here, the operation of the present invention having the above configuration will be described with reference to the drawings.

When a voltage is applied to the signal electrode 115a or 115b, the vibrating portions 112a, 112
b extends and deforms, and the protrusion 110a at the tip is
08 is suddenly pressed to give an impact to the ink 113 in the pressure chamber 103. A pressure wave is generated in the ink 113 in the pressure chamber 103 that has been subjected to the shock, and the pressure wave is generated by the nozzle 1.
It propagates to the ink in 01. The ink to which the pressure wave has been propagated is delivered by the nozzle 101, and the ink droplet 116
And fly.

The pressure chambers 103 are connected to one common ink reservoir 105 through the respective ink inlets. After ejecting ink droplets, the ink 113 is replaced by the amount of the lost ink. The pressure chambers 103a, which form a part of the ink flow paths 102a, 102b from the reservoir 105,
103b.

The consumed ink 1 in the ink reservoir 105
13 is an ink supply pipe 1 connected to the ink reservoir 105
At 06, ink is supplied from an ink tank (not shown) provided outside by capillary force.

Here, for example, as shown in FIG. 1, a manufacturing process for obtaining a piezoelectric element 109 used for an ink jet head having 20 nozzles 101 will be described with reference to FIGS.

As shown in FIG. 3, an intermediate electrode 117 is provided in a rectangular parallelepiped piezoelectric material 109 '. This piezoelectric material 109 ′ is formed by laminating an intermediate electrode made of a conductive material such as silver or palladium on a raw sheet having a thickness of 20 to 60 μm of a lead zirconate titanate-based piezoelectric material by a thick-film printing lamination method, and sintering. Is obtained. This intermediate electrode 117 is a first intermediate electrode 1 patterned at the center of the piezoelectric material.
17a and the patterned second intermediate electrodes 117b other than the central portion are alternately arranged.

Next, as a second step, as shown in FIG.
The center groove 1 extends from the center of the upper surface of the piezoelectric element 109 to a point beyond the first intermediate electrode 117a by slicing or the like.
11 is formed. Then, two driving units 112a and 112b having the same intermediate electrode pattern structure and a base 118 having no intermediate electrode are formed thereunder.

As shown in FIG. 7, if necessary, the protrusions 120a, 120b are formed on the upper surfaces of the drive units 112a, 112b.
Ob may be cut out from the upper surface of the piezoelectric material 109 'or may be formed by bonding a plate material.

Next, in a third step shown in FIG. 5, the entire surface of the center groove 111 formed in the second step and each of the driving portions 112a,
From the top of 112b, the second intermediate electrodes 117b-a, 117
The signal electrodes 115a and 115b are formed on the side surface bb. These electrodes are formed of a conductive material such as Au by plating, sputtering or vapor deposition.

In the fourth step of FIG. 6, the driving units 112a and 112b are divided into a plurality of divided grooves 119a so as to match the number and width of the pressure chambers 103 and the pitch between the pressure chambers shown in FIG.
Divide by 119f. Each of the dividing grooves 119a to 119
The depth of f, that is, the bottom position 115 ′,
5a and 115b from the center groove 111
Is provided in a range up to a position higher than the bottom of the. This causes the signal electrode 115 to be divided and the center groove 111 to be divided.
This is to prevent the common electrode 114 provided in the above from being divided.

Accordingly, the common electrode 114 is grounded by one conductive line, and the applied voltage signal is applied to each of the divided signal electrodes 115a to 115t via a signal line (not shown) such as an FPC cable connected thereto. By applying the voltage, each of the divided driving units 112 can be driven independently.

Here, in the above embodiment, the piezoelectric elements used in the ink jet head are integrally formed in two rows. However, in another embodiment, when the piezoelectric elements integrally formed in four rows are used. Will be described with reference to FIGS.

FIG. 8 is an external perspective view showing another example of a piezoelectric element used in the ink jet head according to the first embodiment of the present invention. FIG. 9 is a top view of four types of electrode patterns used in the piezoelectric element of FIG. FIG. 10 and FIG. 10 are sectional views of the piezoelectric element of FIG.

The piezoelectric element 223 shown in FIG. 8 has a first electrode layer 2 patterned at both ends and a central portion as shown in FIG.
10 (FIG. 9A) and the second electrode layer 202 (FIG. 9B) which is not patterned at both ends and the center portion, as shown in FIG. It is patterned so as to overlap, and a plurality of layers are alternately stacked with the piezoelectric material 203 interposed therebetween.

Furthermore, the third electrode layer 20 which is not patterned only in the central portion under the insulating material 205
4 (FIG. 9C) are laminated, and the third electrode layer 204
A fourth electrode layer 206 (FIG. 9D), which is patterned over the entire surface with an insulating material 207 interposed therebetween, is stacked under the insulating layer 207. Under the fourth electrode layer 206, an insulating material 208 is stacked as a base layer. Have been.

The third electrode layer 204 is formed in the first groove 20
9 and the second electrode layer 20 exposed in the second groove 210
2 to facilitate the wiring from the side of the piezoelectric element 223. Similarly, the fourth electrode layer 206
This is for making it possible to easily perform wiring to the first electrode layer 201 exposed in the third groove from the side of the piezoelectric element 223.

A manufacturing process for obtaining the piezoelectric element 223 will be described with reference to the drawings.

First, a part of the non-patterned portion of the first electrode layer 201 indicated by a broken line in FIG.
Of the patterning portion of the third electrode layer 204 and a part of the patterning portion of the third electrode layer 204, that is, FIGS.
As shown in FIG. 5, the first groove 209 and the second groove 210 formed so as to be deeper than the third electrode layer 204 and shallower than the fourth electrode layer 206, and to pattern the first electrode layer 201 in the central portion. Part, a part of the non-patterned part of the second electrode layer 202, a part of the non-patterned part of the third electrode layer 204, and a part of the patterned part of the fourth electrode layer 206. A third groove 211 formed so as to be deeper than the fourth electrode layer 206 is formed.

Then, two electrodes 212 connecting the first electrode layer 201 exposed to the outside of the rows at both ends and forming a pad, and the second electrode exposed to the first groove 209 and the second groove 210 A first groove 209 and a second groove 210 for connecting the layer 202 and the third electrode layer 204, respectively;
Two electrodes 213 formed on the entire surface, two electrodes 214 at both ends forming pads by connecting to the third electrode layer 204 exposed outside the rows at both ends, and a first electrode exposed at the third groove 211. An electrode 215 formed on the entire surface of the third groove 211 for connecting the electrode layer 201 and the fourth electrode layer 206, and an electrode 215 formed on the entire surface of the fourth electrode layer 206 exposed to the outside of both end rows to form a pad. The two electrodes 216 are formed by a method such as vapor deposition.

Finally, the fourth groove 217 is formed so as to cut the electrode at the bottom of the third groove 211, and is deeper than the external electrodes 216 connected to the fourth electrode layer 206 at both ends and in the row direction. And a fifth groove 218 is formed to correspond to each pressure chamber.

The piezoelectric element 223 is manufactured through such a process.

In the case where the number of piezoelectric elements is three, the structure may be such that there is no one of the left and right ends of the above structure.

[0041]

As described above, according to the present invention, the piezoelectric element to be attached to the ink jet head can be formed integrally, so that the positioning and attachment of the piezoelectric element to the ink jet head only need to be performed once, and Adhesion to the vibrating plate and assembly are extremely easy, and an inexpensive piezoelectric element can be obtained. Further, the positional accuracy between the nozzles and between the rows is only the processing accuracy, and the factor of the bonding accuracy is eliminated, so that the positional accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a top view of a flow path plate of an inkjet head according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the inkjet head according to the first embodiment of the present invention.

FIG. 3 is a perspective view showing a first step of manufacturing the piezoelectric element of the ink jet head of FIG.

FIG. 4 is a perspective view showing a second step of manufacturing the piezoelectric element of the ink jet head of FIG.

FIG. 5 is a perspective view showing a third step of manufacturing the piezoelectric element of the ink jet head of FIG. 1;

FIG. 6 is a perspective view illustrating a fourth step of manufacturing the piezoelectric element of the ink jet head of FIG. 1;

FIG. 7 is a perspective view showing another example of the piezoelectric element used in the ink jet head of the present invention.

FIG. 8 is an external perspective view showing another example of the piezoelectric element used in the ink jet head according to the first embodiment of the present invention.

FIG. 9 is a top view of four types of electrode patterns used in the piezoelectric element of FIG.

FIG. 10 is a cross-sectional view of the piezoelectric element of FIG.

FIG. 11 is an overall sectional view of a conventional ink jet head.

FIG. 12 is an enlarged cross-sectional view of the nozzle section of FIG.

[Explanation of symbols]

 109 Piezoelectric element 111 Center groove 112 Driver 114 Common electrode 115 Signal electrode 117 Intermediate electrode 118 Base 119 Dividing part

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B41J 2/045 B41J 2/055

Claims (3)

(57) [Claims] 1. An ink flow path having a plurality of nozzle holes for delivering ink, a plurality of pressure chambers for supplying ink to the nozzle holes, and an ink reservoir for holding ink to be supplied to the pressure chambers. A vibration plate joined to the plate, and pressure generating means for instantaneously deforming a wall of the pressure chamber at a position facing the pressure chamber of the vibration plate to generate pressure on the ink, and to form an ink droplet on the recording medium. In an ink jet head for jetting and forming characters and figures by dots, the pressure generating means forms a center groove at least at the center thereof.
Only to form the driving portion of the at least two rows, each of the drive unit is divided in the column direction, each of the divided plurality of pressure chambers position of each tip is located on the left and right of the nozzle <br / Separate grooves are provided perpendicular to the center groove to correspond to>
An ink jet head, characterized by being obtained. 2. The pressure generating means is provided with a center groove at the center thereof to have a U-shaped cross section, and two rows of drive units formed by the center grooves are provided with the plurality of driving units arranged on the left and right sides of a nozzle. In order to correspond to each of the pressure chambers, a dividing groove is provided perpendicularly to the center groove, and the electrodes common to the two rows of the driving unit and the opposite side surfaces of the center groove of the driving unit are provided on the entire surface of the center groove. 2. The ink jet head according to claim 1, further comprising signal electrodes. 3. The pressure generating means is provided with a third groove in the center thereof, and a first groove and a second groove on both sides of the third groove to form four rows of drive units. 2. The ink jet head according to claim 1, wherein a fourth groove for separating the driving unit into two rows is provided in the three grooves, and a fifth groove is provided perpendicular to the three grooves.