JPH09262980A - Ink-jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably perform the supply of ink into a liquid chamber without being dispersed at every channel by preventing bubbles from being generated in the flow path of ink. SOLUTION: This ink-jet head is equipped with the upper plate 10 in which liquid chambers, manifolds 24 and ink supply ports 15 are formed, a vibration plate for pressing the liquid chamber, piezoelectric elements 5 for pressing the vibration plate, a pedestal 3 fixing the piezoelectric elements 5 and a nozzle plate 1 for discharging ink droplets by receiving ink pressure of the liquid chamber. In this case, the manifold 24 is divided into at least 2 to prevent bubbles from being generated in the manifold 24 and to stably supply ink between the liquid chambers. Ink supply ports 15 are provided in each manifold 24. Further, the manifolds 24 are formed into a streamlined shape and a plurality of ribs 14 are provided. Slits 12 are provided on the manifolds 24 side of the liquid chamber.

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 selectively depositing ink droplets on an image recording medium.

[0002]

2. Description of the Related Art As an ink jet head, a piezoelectric element provided on the side surface of a liquid chamber is expanded and contracted, and ink pressure is applied to eject ink droplets from nozzle holes for recording.

[0003]

In the ink jet head, it is desirable to be able to control the ink pressure during driving and non-driving, and at all times and places such as in the liquid chamber and in the manifold. However, if the liquid chambers communicate with each other via the manifold, when ink is drawn from the ink supply port into the liquid chambers via the manifold, if the flow channel resistance of the ink varies depending on the channel, the ink will flow to the place where the flow channel resistance is large. It is difficult to pull in, and it is easy to pull in small areas. Therefore, there is a problem in that there is a difference in the ink supply capability to the liquid chamber, and there are variations in the speed and diameter of the droplets when the head is driven to eject the ink. Also, if there are bubbles in the liquid chamber or manifold, when a drive signal is applied to the piezoelectric element to bend the diaphragm and generate pressure in the liquid chamber, the bubbles absorb and disperse the pressure, which is necessary for printing. Since it is not possible to obtain a high ink droplet flight speed, it is desirable that the liquid chamber and the manifold are always filled with ink. However, when an arbitrary channel is driven, ink is drawn from the non-driving channel adjacent to the channel to the driving channel via the manifold, and the negative pressure of the adjacent non-driving channel increases. If this negative pressure becomes higher than the meniscus proof stress of the nozzle openings supported by the surface tension of the ink, there is a problem that the meniscus retracts and entrains bubbles. Further, when the ink is injected into the manifold, the ink penetrates into the wall surface due to the surface tension, so that the air in the manifold is surrounded and air bubbles remain. Therefore, an object of the present invention is to provide an inkjet head having stable characteristics while suppressing the above problems.

[0004]

In order to solve the above problems, a manifold is divided into two or more parts, an ink supply port is provided in each manifold, and the ink supply port to the liquid chamber is provided for each manifold. The ink jet head has a streamlined structure, a slit is provided in the liquid chamber on the manifold side, and the manifold has a plurality of ribs.

[0005]

1 is a perspective view of an ink jet head of an embodiment according to the present invention. The nozzle plate 1 is provided with a plurality of nozzle openings 2 penetratingly opened by a press or the like at equal intervals in the longitudinal direction of the nozzle plate. One surface of the nozzle plate 1 having the nozzle openings is subjected to a water repellent treatment, and the surface facing the surface subjected to the water repellent treatment and the inner surface of the nozzle opening are subjected to a hydrophilic treatment. The base 3 is formed of a concave rigid member, and the common electrode film 4 is formed in the recessed portion.
Are formed. The piezoelectric element 5 is formed with electrode films 6 and 7 that are arranged so as to face each other, and one electrode film 6 and the common electrode film 4 of the base are electrically joined by a conductive adhesive or the like to form a nozzle opening. They are arranged on a pitch. In this piezoelectric element 5, a piezoelectric element plate having two electrode films arranged opposite to each other is electrically bonded and fixed to a base with a conductive adhesive or the like, and then separated at a nozzle opening pitch by a wire saw or the like. It is composed of.

A plurality of electrode patterns 9 are formed on the diaphragm 8 so as to correspond to the piezoelectric elements 5. This electrode pattern 9 and the other electrode film 7 of the piezoelectric element are electrically joined with a conductive adhesive or the like, and the edge portion of the base 3 and the end of the diaphragm where the electrode pattern 9 is not formed. The edges are fixed with an adhesive or the like. On one surface of the upper plate 10, a plurality of grooves 11 corresponding to the piezoelectric elements and a common groove 13 communicating with one end of each groove are used as ink flow paths, and from the cartridge provided on the one surface of the common groove. And an ink supply port 15 for supplying the ink. The diaphragm 8 is fixed to the upper plate with an adhesive or the like on the surface facing the surface fixed to the base so as to cover the groove. A plurality of grooves 11 and a common groove 13 provided on the upper plate 10.
The liquid chamber 23 and the manifold 24 are covered with the vibration plate 8 and are hermetically sealed. This manifold 24
The liquid chamber 23 is filled with ink to form an ink flow path.
Further, in this manifold, when ink is supplied to the liquid chamber, the distance from the ink supply port 15 to the liquid chamber becomes the flow path resistance of the ink. Therefore, in this embodiment, since the manifold 24 is divided into two and the ink supply ports 15 are provided respectively, the difference in the distance from the ink supply port to the liquid chamber is reduced for each liquid chamber. Further, as described above, since this manifold serves as an ink flow path, it must be filled with ink. However, as shown in FIGS. 2a, 2b, and 2c, the ink 19 that is in contact with the manifold surface due to surface tension during ink injection.
Flows in faster than the ink 20 that is not in contact with the manifold surface, and the ink 19 flows into the liquid chamber first. Therefore, the air 25 that is sandwiched between the ink 20 that comes later and the ink 19 that first flowed into the liquid chamber remains. To prevent this, in the embodiment, a plurality of ribs 19 are provided in the manifold as shown in FIGS. 3A, 3B and 3C. Since the surface area of the manifold is increased by the ribs, the amount of ink 19 in contact with the surface of the manifold is increased and the amount of ink 20 not in contact with the surface of the manifold is decreased, so that residual bubbles are suppressed.

Further, when the ink is injected from the ink supply port 15 into the manifold 13, if the manifold shape has corners, the flow of the ink is disturbed smoothly and the air bubbles are entrained. Therefore, in order to prevent this, in the embodiment, FIGS.
As shown in FIG. 7, the streamline 26 is formed in the manifold shape from the ink supply port to the liquid chamber, so that the ink flow is made smooth and the generation of bubbles is suppressed. The manifold 13 communicates with the plurality of liquid chambers 11 as described above. Therefore, when driving a channel,
Ink is not supplied to the liquid chamber only from the manifold as shown in b, c, and d, but is also supplied from the ink in the liquid chamber adjacent to the manifold via the manifold. As the number of drive channels increases, the amount of ink drawn from the non-drive channels also increases. And as the amount of drawing increases, the negative pressure in the liquid chamber of the non-driving channel increases,
As described above, when it becomes higher than the meniscus proof strength, the meniscus retreats and entrains air bubbles from the nozzle opening. Therefore, as shown in FIG. 5, the slit 12 is provided on the manifold side of the liquid chamber 23 to prevent the ink from being drawn into the adjacent channels. Returning to FIG. 1 again, such an upper plate, a base, a piezoelectric element, and a vibrating plate are laminated and integrated, and the nozzle plate is positioned so that the nozzle opening corresponds to the liquid chamber on the hydrophilic surface. Then, the inkjet head is configured by being fixed with an adhesive or the like. In such an inkjet head, the piezoelectric element 5 electrically connected to the electrode pattern 9 and the common electrode 4 bends the vibration plate when a drive signal in a direction to extend the piezoelectric element 5 is applied to the piezoelectric element 5.
It is possible to pressurize the ink in the nozzle 3 and eject the ink from the nozzle opening 2.

[0008]

According to the present invention, the manifold is divided into two or more parts and the ink supply ports are provided in the respective manifolds, so that the flow path length from the ink supply port to the liquid chamber for each channel can be reduced. Variations can be reduced. By arranging a slit in the liquid chamber on the manifold side, when an arbitrary channel is driven, the amount of ink drawn from the non-driving channel adjacent to that channel through the manifold is reduced, and the effect of reducing the retreat of the meniscus is reduced. is there. In addition, by forming a streamlined shape from the ink supply port to the liquid chamber and arranging a plurality of ribs for each manifold, the ink is supplied smoothly and in a well-balanced manner, which is effective in preventing the generation of bubbles. Therefore, it is possible to reduce the flow path resistance and the influence of bubbles on the ink ejection, and the efficiency of ink pressure management by the piezoelectric element is improved.

[Brief description of drawings]

FIG. 1 is a perspective view of an inkjet head according to the present invention.

FIG. 2 is a diagram showing an embodiment according to the present invention.

FIG. 3 is a diagram showing an embodiment according to the present invention.

FIG. 4 is a diagram showing an embodiment according to the present invention.

FIG. 5 is a diagram showing an embodiment according to the present invention.

[Explanation of symbols]

 1 Nozzle Plate 2 Nozzle Opening 3 Base 4 Common Electrode Film 5 Piezoelectric Element 6 Electrode Film 7 Electrode Film 8 Vibration Plate 9 Electrode Pattern 10 Upper Plate 11 Groove 12 Slit 13 Common Groove 14 Rib 15 Ink Supply Port 16 Meniscus 17 Ink Drop 18 Streamline part of the manifold 19 Ink that contacts the manifold surface 20 Ink that does not contact the manifold surface 21 Residual bubbles on the nozzle side 22 Residual bubbles in the manifold 23 Liquid chamber 24 Manifold

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Seiichi Osawa 840 Takeno, Shimotomi, Tokorozawa-shi, Saitama Citizen Watch Co., Ltd.

Claims (4)

[Claims] 1. An ink jet printer in which a plurality of liquid chambers are formed on the same surface, a nozzle opening is provided at one end of the liquid chamber, and ink droplets are ejected from the nozzle opening through the liquid chamber from a manifold arranged opposite to the nozzle opening. An ink jet head characterized in that a manifold is divided into two or more parts, and an ink supply port is provided in each. 2. The ink jet head according to claim 1, wherein the ink supply port and the liquid chamber are streamlined. 3. The ink jet head according to claim 1, wherein a slit is provided at an end of the liquid chamber on the manifold side. 4. The ink jet head according to claim 1, wherein the manifold is provided with a plurality of ribs.