JPH04369544A - Ink jet head - Google Patents

Abstract

PURPOSE:To provide a highly accurate ink jet head corresponding to a multinozzle system and the enhancement of density and simple to assemble. CONSTITUTION:A plurality of nozzles 14,14 emitting ink are provided while the common pressure generating member 16 to a plurality of the nozzles 14,14 and the ink heating bodies 15 to the individual nozzles 14 are mounted. The heating bodies 15 are not driven with respect to the nozzles emitting ink and the heating bodies 15 are driven with respect to the nozzles emitting ink to generate air bubbles. By this constitution, the ink can be selectively emitted even when the common pressure generating member 16 is used.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention allows ink droplets to fly,
The present invention relates to an inkjet head used in an inkjet recording device such as a printer that forms an ink image on a recording medium such as recording paper.

0002

BACKGROUND ART A nozzle forming substrate having a plurality of nozzles, a pressure generating member comprising a piezoelectric transducer arranged opposite to the nozzles, a gap between the piezoelectric transducing element and the nozzle forming substrate, and the piezoelectric transducer. Japanese Patent Publication No. 60-8953 discloses an on-demand inkjet head that includes ink that fills the periphery of the element, and in which the piezoelectric transducer is displaced by an applied voltage to eject ink from a nozzle.

[0003] Furthermore, a heating element is disposed in the flow path connecting the ink tank and the ejection port, and by generating bubbles, the ink in the flow path is pressurized, and a portion of the ink is ejected from the ejection port as ink droplets. An on-demand type inkjet head for this purpose is disclosed in Japanese Patent Publication No. 2-46389.

0004

[Problems to be Solved by the Invention] However, in the above-mentioned prior art, one ink cavity is provided corresponding to each nozzle, and a pressure generating member is also required for each ink cavity. . The number of nozzles or the nozzle density is largely influenced by the size and spacing of the pressure generating member and the cavity. Reducing the size of the pressure generating member to increase the nozzle density did not provide the necessary displacement volume or pressure. Furthermore, when there is a plurality of pressure generating members as described above, variations in properties are likely to occur, such as changes in bonding strength and precision with the cavity, and changes in characteristics due to internal distortion due to processing of the pressure generating members. Due to these variations, there is a problem in that the pressure applied to the ink near the nozzle varies, resulting in variations in the ink ejection characteristics of the inkjet head, and thus the print quality.

Furthermore, due to the large number and small size of the pressure generating members, there is a problem of poor productivity and workability.

Furthermore, when ejecting ink droplets by generating bubbles, a large amount of heat is required to obtain the pressure to eject the ink, so the durability of the heating element is poor.
This affected the size of the heating element, the distance between adjacent nozzles had to be set to prevent temperature transfer, and the time it took to absorb heat generation limited the time until the next ink was ejected, which greatly affected printing speed. In addition, since pressure is generated for each nozzle, there is a problem in that variations in the characteristics of the heating element cause variations in the ink ejection characteristics and, therefore, the print quality. Therefore,
The present invention solves these problems, and its purpose is to provide an inkjet head that supports multiple nozzles, high density, high print quality, and high print speed, and that can be assembled easily with high precision. There is a particular thing.

[0007]

Means for Solving the Problems The present invention is characterized by having a plurality of nozzles that eject ink, a common ink ejection means for the plurality of nozzles, and a means for controlling ink ejection for each nozzle, The ink ejection means common to the plurality of nozzles applies pressure to the ink within the nozzles, and the ink ejection control means is bubbles generated by a heating element.

[0008]

[Operation] First, since the ink ejecting means extends over a plurality of nozzles, ink can be ejected from each nozzle with a uniform amount and speed of ink droplets.

[0009] Furthermore, due to the heat generated by the heating element provided in each nozzle, air bubbles are generated within the nozzle and the ejection of ink droplets is stopped. The bubbles at this time are smaller than the bubbles required to eject the ink droplets. By doing the above, ink droplets are selectively guided to the recording paper.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a sectional view of the main part of an inkjet head showing an embodiment of the present invention. In the system surrounded by the container 10 and the nozzle forming substrate 11, there is a pressure generating member 16 and a fixing plate 30 for fixing it, and furthermore, the ink 1
9 is connected to an ink tank (not shown) through an ink supply port 31 in order to keep it always filled with ink. The free end 18 of the pressure generating member 16 is arranged so as to apply pressure to the ink in the plurality of nozzles 14 arranged in a row on the nozzle forming substrate 11, and one end is fixed by adhering to the fixing plate 30. be. Further, the opening on the recording medium side of the nozzle is 12, and the opening on the ink side is 13, and heating elements 15, 15, etc. formed by a method such as vapor deposition are provided in each nozzle 14, 14, etc. There is. FIG. 2 is a cross-sectional view of a nozzle that discharges ink. In FIG. 2(a), when the pressure generating member 16 is driven by applying an appropriate pulse, it deforms in the direction of arrow A as shown in FIG. 2(b). The pressure generated by this deformation is
The ink 19 in the ink-side opening 13 of the nozzle is concentrated, and an ink droplet 20 is ejected from the recording medium-side opening 12 as shown in FIG. 2(c), returning to the original state in FIG. 2(d). . During this series of operations, no voltage is applied to the heating element 15.

FIG. 3 is a sectional view of a nozzle that does not eject ink. A voltage is applied to the heating element 15 of the nozzle that does not eject ink. Then, bubbles are generated in the ink 19 in the nozzle, and the meniscus 21 of the ink 19 is drawn up to the opening 13 on the ink side of the nozzle, as shown in FIG. 3(b). Even if the pressure generating member 16 deforms in the direction A in this state and applies pressure to the ink 19, the meniscus 21 of the ink 19 is slightly smaller than the opening 12 of the nozzle on the recording medium side, as shown in FIG. 3(c). Since the ink only comes out, it does not result in ink droplet ejection.

As described above, it is possible to select the nozzles that eject ink and the nozzles that do not eject ink, and guide the ink to the recording medium.

Although the nozzle can have any shape, if the opening 13 on the ink side is made larger than the opening 12 on the recording medium side, the pressure of the bubbles will be reduced by the opening 13 on the ink side. The amount of heat generated can be reduced, and it is also easy to eliminate ink ejection due to bubble generation.

[0015]

[Effects of the Invention] According to the present invention, it is possible to use one ink ejection means across multiple nozzles, thereby eliminating manufacturing variations corresponding to each nozzle and applying uniform pressure to the ink near each nozzle. It is possible to eject ink droplets with less variation, and the print quality is improved. Nozzles can be arranged at high density without being restricted by the spacing between ink ejecting means. It is possible to have multiple nozzles without being too constrained by the number of ink ejection means. Since it is possible to form the discharge means using a large member, it is easy to obtain adhesive strength and position accuracy, which increases reliability.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the main part of an inkjet head showing an embodiment according to the present invention.

FIG. 2 is a cross-sectional view of a nozzle that discharges ink.

FIG. 3 is a cross-sectional view of a nozzle that does not eject ink.

[Explanation of symbols]

10 Container 11 Nozzle forming substrate 12 Opening on the printing paper side of the nozzle 13 Opening on the ink side of the nozzle 14 Nozzle 15 Heating element 16 Pressure generating member 19 Ink 20 Ink drop 21 Meniscus 30 Fixed plate 31 Ink supply port

Claims (2)

[Claims] 1. An ink jet head comprising a plurality of nozzles that eject ink, a common ink ejection means for the plurality of nozzles, and a means for controlling ink ejection for each nozzle. 2. The common ink ejection means for the plurality of nozzles is to apply pressure to the ink within the nozzles,
2. The inkjet head according to claim 1, wherein the ink ejection control means for each nozzle is a bubble generated by a heating element.