JP3094672B2 - 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 a so-called on-demand type ink jet head for printing by discharging ink droplets from nozzles.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. 60-12926
In Japanese Patent Application Publication No. 3 (1993) -313, a common ink chamber is provided on the upper surface of one flow path substrate, and the common ink chamber communicates with each pressurizing chamber via a plurality of ink supply paths. The nozzles are communicated with each other via a common ink chamber and the communication path is formed in the same plane, and each nozzle is provided at the tip of each communication path in a direction perpendicular to the communication path. An ink discharge unit such as a piezoelectric element is provided on the vibration plate bonded to the flow path substrate so as to face the pressure chamber. When the ink discharge means operates,
The ink in the pressurized chamber is extruded into the communication path, and the direction of the ink is changed vertically at the end of the communication path, and is discharged outward from the nozzle.

[0003]

However, when the ink changes its course vertically from the communication path toward the nozzle, the ink collides with the side wall at the end of the communication path and generates a reflected wave.
Unnecessary flow such as an attempt to flow backward occurs, and loss occurs in the discharge efficiency from the nozzle.

Accordingly, it is an object of the present invention to make the flow of ink from the communication passage to the nozzle smooth, and to improve the efficiency of ejection from the nozzle.

[0005]

In order to achieve the above object, an ink jet head according to the present invention comprises a nozzle plate provided with nozzles formed in a thickness direction and a substrate laminated on the nozzle plate. A pressurizing chamber to which pressurizing means for pressurizing the ink is joined, and a communication passage communicating the pressurizing chamber and the nozzle are formed on the joint surface of the nozzle, and the communication passage defines a center line of the nozzle. It is characterized in that a protruding portion having a center is formed.

The protruding portion is a conical protrusion centered on the center line of the nozzle or a protrusion including an inclined surface inclined with respect to the nozzle.

[0007]

The protrusion provided in the communication path smoothly guides the ink inside by changing the direction of the flow toward the nozzle in the vertical direction.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An overall configuration of an embodiment of the present invention will be described with reference to FIGS. The nozzle plate 1 is made of a material such as polysulfone which is strong against ink and is suitable for bonding, and has a plurality of nozzles 1a penetrating therethrough in the thickness direction. As shown in the figure, the central portion of the nozzle plate 1 is formed as a thick portion 1b protruding from the front surface.
are penetrated through the thick portion 1b. On the back surface of the nozzle plate 1, a substrate 2 is laminated and joined. The substrate 2 is provided with a plurality of ink supply holes 2a. Nozzle plate 1 and substrate 2
A plurality of pressurizing chambers 3 are provided on the joint surface with the nozzles 1a and the ink supply holes 2a so as to be substantially perpendicular to the nozzles 1a and the ink supply holes 2a. The communication passages 4... 5 communicating with the holes 2 a are formed in sections. The nozzle 1a opens to the communication path 4, and the ink supply hole 2a opens to the communication path 5. A protruding portion 4a, which will be described later, is formed in the communication passage 4 so as to face the nozzle 1a.

The nozzle 1a and the ink supply hole 2a are formed narrower than the pressurizing chamber 3 and the communication passages 4 and 5, so that the flow resistance of the nozzle 1a and the ink supply hole 2a is reduced. And it is larger than the flow path resistance of the communication paths 4 and 5. It is desirable that the flow path resistance of the nozzle 1a is formed to be smaller than or substantially equal to that of the ink supply hole 2a.

The pressure chamber 3 is located on the front surface of the nozzle plate 1.
A pressurizing means is provided at a position opposed to. That is, the pressurizing means is formed by laminating a plurality of vibrating plates 6 made of a metal such as phosphor bronze or brass and a plurality of piezoelectric elements 7 on the nozzle plate 1 with an adhesive such as epoxy. They are joined. Each piezoelectric element 7 is joined to a predetermined electrode of a flexible cable 8 on which a pattern electrode electrically connected to an external driver IC (not shown) for driving a piezoelectric element is formed by a conductive paste or the like. A common electrode 9 is formed of a conductive paste on the front surface of the nozzle plate 1. The common electrode 9 is electrically connected to the respective vibration plates 6 to which the respective piezoelectric elements 7 are joined, and is connected to a predetermined pattern electrode of the flexible cable 8. Conduction is achieved by the conductive paste.

An ink cartridge case 10 is bonded to the back surface of the substrate 2 with an adhesive such as epoxy. A common ink chamber 11 is formed on a joint surface between the substrate 2 and the cartridge case 10 so as to be orthogonal to the ink supply holes 2a and communicate with the ink supply holes 2a. Common ink chamber 1
1 is provided with an opening 10a through which ink is supplied from the inside of the cartridge case 10.
The filter 12 is joined by heat fusion. This prevents dust and the like in the ink stored in the cartridge case 10 from entering the common ink chamber 11.

The ink contained in the cartridge case 10 is contained in a state of being impregnated in a porous material 13 such as polyurethane, and is sealed with a lid 14 having an air hole 14a.

As shown in an enlarged manner in FIG. 1, at a position facing the nozzle 1a in the communication path 4, the ink inside the communication path 4 is changed in a vertical direction from the communication path 4 toward the nozzle 1a. A guiding protrusion 4a is formed. This protrusion 4a
Has a shape in which the cross-sectional area decreases in the nozzle direction with respect to the center line of the nozzle 1a.
It may be a trapezoidal projection or a projection having a concave peripheral surface.

FIG. 2 shows a projection 4b as another embodiment.
The projection 4b includes an inclined surface inclined with respect to the nozzle 1a. That is, assuming that the ink is sent from the right to the left in FIG. 2 through the communication path 4, the left side of the position facing the nozzle 1a is projected, and the right side is the nozzle 1a.
Is formed as an inclined surface 4c that is inclined with respect to. That is, the surface of the substrate 2 constituting the communication path 4 gradually rises toward the left to reach the top of the protruding portion 4b, and the inclined surface 4c may be a curved surface, a flat surface, or a polyhedron as shown in the drawing. Shape may be sufficient.

When ink is ejected, when a drive signal from a driver IC is supplied to the piezoelectric element 7 through the flexible cable 8, the piezoelectric element 7 is deformed together with the vibration plate 6 and bent into the pressure chamber 3. Thereby, the ink in the pressurized chamber is pressurized and passes from the pressurized chamber 3 through the communication path 4 to the nozzle 1a.
Ejects ink from the. When the ink passes through the communication path 4, in the example of FIG. 1, the protrusion 4a forms a vortex toward the nozzle 1a, and ejects a highly linear ink droplet from the nozzle. Also in the example of FIG. 2, the direction of the flow of the ink is smoothly changed by the inclined surface 4c of the protruding portion 4b, and the ink is directed to the nozzle 1a. As in the case of FIG.

When the ink is ejected from the nozzle 1a, the ink flows from the common ink chamber 11 toward the pressurizing chamber 3 via the ink supply hole 2a.
When the flow resistance of the nozzle 1a is set smaller than that of the ink supply hole 2a as described above, the ink is stably ejected from the nozzle 1a. After the ink is ejected, the voltage application to the piezoelectric element 7 is stopped, and the piezoelectric element 7 is bent outward by the
The pressure inside becomes negative. Due to this negative pressure, the porous material 1
The ink held in the filter chamber 3 passes through the filter 12, passes through the common ink chamber 11, and flows from the ink supply hole 2a to the pressurizing chamber 3.
And are supplied into the communication passages 4 and 5.

According to the illustrated example, the common ink chamber is provided on the side of the substrate opposite to the nozzle plate, but is not limited to this. It may be a communication formed.

[0018]

As described above, in the ink jet head of the present invention, the nozzle plate in which the nozzles are formed in the thickness direction and the substrate are laminated, and the joining surface between the nozzle plate and the substrate is provided. A pressurizing chamber to which pressurizing means for pressurizing the ink is joined, and a communication passage communicating the pressurizing chamber and the nozzle are formed, and the communication passage has a protruding portion centered on the center line of the nozzle. Is formed, even if the communication path and the nozzle are orthogonal to each other, when the ink passes through the communication path, a vortex is generated by the protrusion at the position corresponding to the nozzle in the communication path, , It is possible to eject ink droplets having high linearity. Therefore, there is an effect that an ink jet head having excellent responsiveness can be provided because ink landing accuracy is high and ejection efficiency from nozzles is high.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part showing another embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating the entire inkjet head of the present invention.

FIG. 4 is a partially cutaway front view of the same.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle plate 1a Nozzle 2 Substrate 3 Pressurization chamber 4 Communication path 4a Projection (conical projection) 4b Projection 4c Inclined surface 6,7 Pressurizing means (vibrating plate, piezoelectric element)

Claims (1)

(57) [Claims] 1. A nozzle plate having a nozzle formed in a thickness direction and a substrate are laminated, and a pressure unit for pressing ink is bonded to a bonding surface between the nozzle plate and the substrate. A pressurizing chamber and a communication passage communicating the pressurizing chamber and the nozzle are defined, and the communication passage is formed with a protruding portion centered on a center line of the nozzle. Inkjet head.