JPH0631916A - Inkjet head - Google Patents

Abstract

PURPOSE:To obtain the stable discharging characteristic of ink in the compact structure and to prevent the interference to the other ink passages. CONSTITUTION:A ring-shaped ink reservoir 11 and a plurality of ink passages 12 are provided in the outer peripheral part of the upper surface of a flow substrate 1. The ink passages 12 communicate with the ink reservoir 11 and run centripetally substantially to the center of the substrate 1. A nozzle 13 is formed to pass through the substrate 1 from an end 12a of the ink passage 12 in the thicknesswise direction. A pressurizing chamber 12b is formed in the middle part of each ink passage 12, communicating with the ink reservoir 11 via a connecting part, 12c. The connecting part 12c extends while being inclined to a normal of the wall face of the ink reservoir 11. A vibrating plate is bonded to the substrate 1 formed as above, and a piezoelectric element is also attached to tone pressurizing chamber, thereby forming this inkjet head. An ink direction changing part, may be disposed opposite to the connecting part at the outer peripheral wall of the ink reservoir, instead of extending the connecting part with an inclination, so as to change the flowing direction of ink.

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 which prints by ejecting ink droplets from nozzles.

[0002]

2. Description of the Related Art Conventionally, as an on-demand type ink jet head, an ink flow path is provided so as to be substantially parallel to an end face of the head, and one end thereof is aligned with a central portion,
A nozzle that penetrates the flow path substrate is provided at the end of each ink flow path on the center side, and ejects ink droplets in a direction orthogonal to the ink flow path, for example, Japanese Patent Laid-Open No. 55-142.
There is a configuration disclosed in Japanese Patent No. 61.

In this conventional example, in order to supply the ink to the ink flow passages, the outer peripheral end portions of all the ink flow passages communicate with the ring-shaped ink storage chamber, and the ink storage chambers have a central portion. An ink flow path is centripetally formed to the side nozzle, and an ink pressurizing chamber is provided in the ink flow path.

[0004]

SUMMARY OF THE INVENTION In the above prior art,
When the pressure is generated from the pressure chamber and the ink is ejected, the ink that has flowed to the ink storage chamber side directly contacts the outer peripheral wall of the ink storage chamber, and the reflected ink is returned to the pressure chamber side. In addition, the ejection of ink becomes unstable, and it takes time to damp the vibration of ink after ejecting the ink once.
This hinders high-speed printing. There is also a problem of so-called crosstalk in which the reflected ink wave interferes with other ink flow paths. This problem can be solved to some extent by lengthening the ink flow path from the pressurizing chamber to the ink reservoir chamber,
The head becomes large and it becomes difficult to realize a small printer.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to obtain a small and stable ink ejection characteristic and prevent interference with other ink flow paths.

[0006]

In order to achieve the above object, the ink jet head of the present invention is provided with an ink storage chamber which is formed in a substantially ring shape, and which communicates with the ink storage chamber and is substantially connected to the ink storage chamber. It is centripetally provided toward the center and has a plurality of ink flow paths including a nozzle at the tip, a pressurizing chamber in the middle, and a connecting portion communicating from the pressurizing chamber to the ink reservoir chamber. It is characterized in that the connecting portion is pulled out at an angle with respect to the normal to the wall surface of the ink reservoir.

Further, the same effect can be obtained by providing the outer peripheral wall portion of the ink reservoir with a direction changing portion for changing the ink flow direction opposite to the connecting portion.

[0008]

The connecting portion is pulled out at an angle with respect to the normal to the wall surface of the ink reservoir, or the outer peripheral wall portion of the ink reservoir is provided with a protruding portion or a concave portion that projects into the ink reservoir opposite to the connecting portion. When provided, the instability of ink ejection due to the influence of the reflection of the ink flowing toward the ink reservoir chamber and the interference with other ink flow paths are prevented when the ink is ejected.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIGS. 1 and 2, a flow path substrate 1 is made of plastic, metal, glass or the like, and an ink reservoir 11 and a plurality of inks are formed on the upper surface of the flow path substrate 1 by plastic molding, metal or glass etching, etc. The flow paths 12 ... Are formed. The ink reservoir chamber 11 is formed in a substantially ring shape on the outer peripheral portion. The ink channel 12 is the ink reservoir chamber 1.
1 is provided centripetally so as to communicate with the inner peripheral portion of the ink cartridge 1 and substantially toward the center, and the front end portion (inner end portion) 12a of the ink flow path is formed.
From the nozzle 13 so as to penetrate the flow path substrate 1 in the plate thickness direction.
... is formed. The plurality of nozzles 13 are arranged in two rows in a zigzag pattern in the center of the flow path substrate 1, and are formed so as to be substantially orthogonal to the ink flow path 12. Each ink flow path 12
A pressurizing chamber 12b ... Is provided in the middle part of the. Pressure chamber 12
The ink storage chamber 11 is communicated from b with the connecting portions 12c. The connection portion 12c is made thin in order to keep the flow path resistance of the flow path from the pressure chamber 12b toward the nozzle 13 and the flow path toward the ink reservoir chamber 11 in balance.

FIG. 3 shows an enlarged view for explaining the structure of the connecting portion 12c for connecting the pressurizing chamber 12b and the ink reservoir chamber 11 in more detail. That is, the tip portion 12a and the pressurizing chamber 1
The direction in which 2b is aligned is the centripetal direction A from the ink reservoir chamber 11 toward the central portion, but the extending direction B of the connecting portion 12c.
Have an angle α with respect to the normal line C to the wall surface of the ring-shaped ink reservoir chamber 11, that is, the connecting portion 12c is drawn out with an inclination to the normal line C.

As shown in FIGS. 4 and 5, the vibration plate 2 is bonded to the surface of the thus formed flow path substrate 1 on the ink flow path 12 side. The vibration plate 2 is provided with an ink supply hole 2a for supplying ink to the ink reservoir chamber 11. Further, a piezoelectric element 3 as an ink ejecting means is attached to the outer surface at a position facing each pressurizing chamber 12b with a conductive adhesive or the like, and electrodes (not shown) are formed on both surfaces of the piezoelectric element 3. . In this embodiment, the diaphragm 2 is made of a conductive material such as phosphor bronze, and the electrode bonded to the diaphragm is a common electrode.

When a drive signal is supplied to the electrodes on both sides of the piezoelectric element 3 from a drive circuit (not shown) when ejecting ink, the piezoelectric element 3 bends to compress the volume of the pressurizing chamber 12b. For this reason, the ink is pressurized, and the ink is discharged from the nozzle 13
Side and the ink reservoir 11 side. The ink flowing toward the nozzle is ejected from the nozzle 13 to the outside, and printing is performed. On the other hand, the ink flowing to the ink reservoir side is connected to the connecting portion 12
Although it flows from c to the ink storage chamber 11, as shown in FIG. 3, the flowing direction B is inclined with respect to the normal line C, so this wave of ink is oblique to the outer peripheral wall of the ink storage chamber 11. It will collide with each other and will be reflected there at a reflection angle equal to the incident angle. Therefore, the influence of the reflected ink wave does not extend from the connection portion 12c to the pressurizing chamber 12b and does not adversely affect the ink ejection. Further, by appropriately setting the magnitude of the angle α, it is possible to prevent the reflected ink wave from interfering with another ink flow path, which is so-called crosstalk.

FIG. 6 shows another embodiment of the ink flow path. The tip portion 22a of the ink flow path 22, the pressurizing chamber 22b, the nozzle 23 and the ink reservoir chamber 21 are the same as those in the previous embodiment. However, the connection portions 22c and 22c are branched into two branches and communicate with the ink reservoir chamber 21. Also in this case, the extending directions B, B of the respective connecting portions are inclined with respect to the normal line C to form an angle β.

Even with this structure, the ink that has flowed rearward when ejecting ink is the same as in the above embodiment.
The outer peripheral wall of No. 1 hits in an oblique direction, and the influence of the wave of the ink reflected there does not reach the original connecting portions 22c and 22c. The normal line C described here is not determined by the wall surface shape of the small region where the connection portion and the ink storage chamber are in contact, but indicates the normal line to the peripheral wall of the ring formed by the entire ink storage chamber 11.

FIG. 7 shows still another embodiment of the ink flow path, which is the ink reservoir chamber 31 and the tip portion 3 of the ink flow path 32.
The configurations of 2a, the pressurizing chamber 32b, and the nozzle 33 are the same as those in the previous embodiment, but the connecting portion 32c is bent in an L-shape substantially at right angles to the centripetal direction A to form the ink reservoir chamber 31. They are parallel to each other and extend as they are to communicate with the ink storage chamber 31.

Also in the case of this construction, as in the above embodiment, the ink that has flowed backward at the time of ink ejection is substantially perpendicular to the substantial normal line C of the ink storage chamber formed in a substantially ring shape, That is, the flow is changed in a direction parallel to the ink reservoir chamber 31,
As it is, it flows into the ink reservoir chamber 31 from the connection portion 32c.
Therefore, since it does not collide with the outer peripheral wall and is not reflected, the influence of the reflected wave of the ink does not reach the connecting portion 32c.

FIG. 8 shows still another embodiment. The ink flow path 42 is formed along the centripetal direction A including the connecting portion 42c and communicates with the ink reservoir chamber 41 as it is. On the other hand, on the outer peripheral wall of the ink storage chamber 41, a projection 41a for changing the ink direction is projected toward the inside of the ink storage chamber 41 so as to face the connecting portion 42c. The protruding portion 41a has an isosceles triangular shape, and its apex faces the connecting portion 42c.

Also in the case of this configuration, as in the above embodiment,
The ink that has flowed backward at the time of ink ejection flows into the ink reservoir chamber 41 from the connection portion 42c along the centripetal direction A, but the wave of the ink is divided into both sides along the slope of the protruding portion 41a, and the surface of the outer peripheral wall portion. Since it flows along the outer peripheral wall portion, it is not reflected vertically by the outer peripheral wall portion, and the influence of the reflected wave of ink is exerted on the connection portion 42c.
It does not extend to

In FIG. 9, a protruding portion 51a is provided in place of the protruding portion 41a of FIG. 8, and the protruding portion 51a protrudes from the outer peripheral wall of the ink reservoir chamber 51 into the ink reservoir chamber. It faces the connecting portion 52c of the ink flow path 52. Other configurations are the same as in the case of FIG.

Also in the case of this configuration, as in the above embodiment,
The ink flowing backward at the time of ink ejection flows into the ink reservoir chamber 51 from the connection portion 52c along the centripetal direction A, but the wave of the ink hits the slope of the protrusion 51a and is reflected there, so that the influence of the ink wave is exerted. It does not extend to the original connection portion 52c.

As described above, the protrusions 41a and 51a are provided as the ink direction changing portions because the protrusions are provided in the ink storage chamber formed in a substantially ring shape.
This is because the inkjet head can be formed in a small size.
When the size restriction is loose, the ink direction changing portion may be a concave portion 61a provided on the outer peripheral portion of the ink reservoir chamber 61 and facing the connecting portion 62c of the ink flow passage 62, as shown in FIG. good.

[0022]

As described above, according to the present invention, the connection portion of the ink flow path with the ink storage chamber is drawn out at an inclination with respect to the normal line to the wall surface of the ink storage chamber, or with the connection portion. Since the ink direction changing portion is provided on the outer peripheral wall portion of the facing ink storage chamber, the wave of the ink flowing from the pressure chamber toward the ink storage chamber at the time of ink ejection is reflected and returns to the connection portion again. It is possible to obtain stable ink ejection characteristics and prevent interference with other ink flow paths without flowing into the connection part of the ink flow path. Moreover, miniaturization can be achieved.

[Brief description of drawings]

FIG. 1 is a plan view of a flow path substrate showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of FIG. 1 cut along a flow path.

FIG. 3 is an enlarged plan view showing a main part of FIG.

FIG. 4 is a plan view of the inkjet head of the present invention.

5 is a cross-sectional view of FIG.

FIG. 6 is an enlarged plan view of an essential part of the second embodiment.

FIG. 7 is an enlarged plan view of an essential part of the third embodiment.

FIG. 8 is an enlarged plan view of an essential part of the fourth embodiment.

FIG. 9 is an enlarged plan view of an essential part of the fifth embodiment.

FIG. 10 is an enlarged plan view of an essential part of a sixth embodiment.

[Explanation of symbols]

 11, 21, 31, 41, 51, 61 Ink reservoir chamber 12, 22, 32, 42, 52, 62 Ink flow passage 12a, 22a, 32a Tip portion 12b, 22b, 32b Pressurizing chamber 12c, 22c, 32c Connection portion 42c, 52c, 62c Connection part 13, 23, 33 Nozzle 41a, 51a Projection part 61a Recess C Normal line

Claims (2)

[Claims] 1. A substantially ring-shaped ink reservoir chamber, which is provided centripetally so as to communicate with the ink reservoir chamber and substantially toward the center portion, and which is intermediate with the nozzle at the tip portion. A plurality of ink flow paths including a pressure chamber of the ink storage chamber and a connection portion that communicates with the ink storage chamber from the pressure chamber, the connection portion being a normal to the wall surface of the ink storage chamber. An ink jet head characterized in that it is inclined and pulled out. 2. A substantially ring-shaped ink reservoir chamber, which is provided centripetally so as to communicate with the ink reservoir chamber and substantially toward the center portion, and which is intermediate with the nozzle at the tip portion. A plurality of ink flow paths including a pressure chamber and a connection portion communicating from the pressure chamber to the ink storage chamber, and the connection portion is provided on the outer peripheral wall of the ink storage chamber. An ink jet head, characterized in that an ink direction changing portion for changing the direction of ink flow is provided oppositely.