JPS60145857A - Discharging apparatus for droplet - Google Patents

Abstract

PURPOSE:To effectively discharge droplets with a simple low cost constitution, by forming a discharge energy generation element and a nozzle member in a unitary body. CONSTITUTION:Ink is supplied from an ink feed pipe 19 and discharge pulse is applied from a drive apparatus via lead electrodes 13, 14. The layer of conversion substance is deformed and the ink in the discharge energy generation element 3 is discharged from an orifice 6. Because the mechanical energy generated from the layer of conversion material is directly delivered to the ink in the pipe only via the very thin layer of electrode, the delivery speed of energy is rapid, further the loss of energy being small and the droplet discharge is effective.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a droplet ejection device, and particularly to a droplet ejection device that ejects liquid supplied into a nozzle member by an ejection energy generating element such as a piezoelectric element.

[Prior Art] Inkjet printers and printers that eject ink from fine orifices and deposit it on a recording medium to record images or characters in the form of dots are known.

Such inkjet printers use a so-called charge deflection method, in which ink is constantly ejected, and in areas where dots are not needed, an electric field is applied to the ink flying region to deflect the ink and record the desired dots. There are two well-known on-demand methods that eject ink only to the necessary areas.

An on-demand type ink droplet discharge tube is described, for example, in specifications such as U.S. Pat. Ink is ejected from the orifice at the tip at a desired timing. Although this method does not require ink deflection that requires a high voltage or an unnecessary ink recovery mechanism as in the charge deflection method, the following problems may occur.

The ejection pressure of ejection energy generating elements such as on-demand piezoelectric elements is generally relatively low, and ejection conditions may vary due to external vibrations to the print head, resonance of the ejection energy generating elements, or dust or air bubbles entering the ink path. Subtle changes in the ink may make it difficult to continuously perform stable ink ejection.

Furthermore, conventional inkjet printers have a problem in that the drive voltage tolerance range (voltage allowance) of the ejection energy generating element for stable ejection becomes narrow in a high recording frequency region. For this reason, in the high frequency region of the recording frequency, the operation of the injection tube becomes unable to follow, and the probability of occurrence of ejection failure increases. This phenomenon already occurs at a frequency of several KHz, and is one of the reasons for preventing an increase in the recording speed.

Here, FIG. 1 shows a conventional on-demand type droplet ejection device for an inkjet printer.

The droplet ejecting device l shown in FIG. 1 has a hydrodynamically substantially smooth inner wall surface and is made of a relatively hard material, such as glass, quartz glass, metal such as stainless steel, or ceramics. , a nozzle member 2 whose inner wall surface can be deformed by external mechanical force, and an energy generating element 3 that discharges a cylindrical electro-mechanical transducer consisting of a piezoelectric element etc. fixed to the outer periphery of this nozzle member 2. It is equipped as

The end of the rear part 5 of the nozzle member 2 serves as an inlet 4,
Usually, ink is supplied by connecting to this inlet 4 a supply pipe that communicates with a liquid ink supply tank (not shown) provided at a location other than the droplet ejecting device 1 . Also,
A leading end 7 of the nozzle member 2 is formed into a tapered shape, and an orifice 6 is formed at the leading end. Furthermore, nozzle member 2
A central portion thereof is a pressure generating portion 8 that can be deformed by the acting force of the ejection energy generating element 3.

The circular cross-sectional area of the pressure generating section 8 is substantially constant over the entire length of the pressure generating section 8, and the circular cross-sectional area of the leading portion 7 gradually decreases from the pressure generating portion, forming an orifice 6 at the end thereof. Further, the circular cross-sectional area of the rear portion 5 is formed to be equal or approximately equal to the circular cross-sectional area of the pressure generating portion 8 over its entire length.

The ejection energy generating element 3 surrounds a pressure generating part 8 region and a part of the leading part 7, which are not shown in the drawings as a whole.
The adhesive layer 9 is provided without gaps so as to efficiently transmit pulsed pressure waves to the liquid ink inside the pressure generating portion 8 region, that is, to minimize mechanical energy loss at the joint. It is firmly fixed to the outer periphery of the nozzle member 2.

The ejection energy generating element 3 ejects and flies ink droplets from the orifice 6 by changing the volume of the pressure generating part 8 in a pulsed manner. Electrode layers 1 are formed on the inner and outer walls of the converter layer 10 made of a mechanical converter material.
1.12. A lead electrode 13 for connecting to an external electrical system is attached to the electrode layer 11, and an electrode 14 for the same purpose is attached to the electrode layer 12 using a conductive adhesive or the like. As shown in the figure, the inner electrode layer 11 is folded back at the front end 7 side of the nozzle member 2 and pulled out to the outside, and is electrically insulated from the electrode layer 12 by an insulating section (interval g1) 15.

In the above configuration, the electric pulse is applied to the lead electrode 13.1.
4, the discharge energy generating element 3 converts the electrical energy into mechanical energy (also understood as acoustic energy) based on its electromechanical coupling coefficient,
Self-transform. This mechanical energy is transmitted from the ejection energy generating element 3 to the internal liquid ink via the intervening adhesive layer 9 and the nozzle member 2, and the internal ink is ejected as droplets from the orifice.

During this operation, energy is transmitted through the adhesive layer 9 and the nozzle member 2, so it is mechanically relaxed and some of the energy is consumed as thermal energy.

As mentioned above, in conventional devices, there is a certain decrease in energy transfer efficiency or transfer speed from the piezoelectric element as an energy generating element to the ink, so if ejection pulses are continuously applied and the frequency is increased, the printing results will be affected. Satellites may be generated, or the ink may fly in a plurality of directions, making it difficult to form a uniform dot, resulting in a decrease in recording quality. Conversely, this low energy transfer efficiency means that a large energy generating element is required to obtain the desired ejection pressure. This means that it is difficult to convert.

The above-mentioned problems are common to droplet ejection devices that use energy generating elements similar to those described above.

In order to solve such problems, it has been proposed to integrally configure the nozzle member and the ejection energy generator. However, even in conventionally known integrated droplet ejection devices, a step is formed at the joint between the ejection energy generator and the supply pipe on the liquid flow path side (inner surface side).

This difference in level may cause the flow of the liquid to not be uniform when the liquid is supplied, resulting in turbulence in the flow, or air bubbles present in the liquid may adhere to the difference in level. Furthermore, it is difficult to easily remove air bubbles that adhere to the stepped portion.

As a result, the energy generated to eject the droplets may not be effectively transmitted to the liquid, or unnecessary energy may be added, which can lead to serious problems in achieving higher quality or higher speed recording. Something happened. In particular, even if a recovery operation is performed, the discharge may not always be restored reliably, which is a big problem in terms of the reliability of the device.

[Objective] The present invention has been made in view of the above points, and it is an object of the present invention to provide a simple, inexpensive, and compact droplet ejection device that is energy efficient and capable of reliably ejecting droplets under desired conditions. purpose.

[Example] Fig. 2 shows an example of the droplet ejection device of the present invention.The following explanation will be given as an example of the droplet ejection device of an in-jet printer, and the same or equivalent members as those of the conventional example will be used. The detailed explanation will be omitted.

In the present invention, a structure is used in which the nozzle member shown in the conventional example and the discharge energy generator are integrally constituted by the discharge energy generator.

That is, as shown in FIG. 2, the converter layer 10 of the ejection energy generating element 3 is formed into a hollow cylindrical shape with the leading end 7 narrowed into a conical shape, and the leading end serves as an orifice 6 with a predetermined diameter. ing. A step is provided inside the rear end of the ejection energy generating element 3, into which the ink supply pipe 19 is fitted and fixed with an adhesive 20. This access to the ink supply pipe 19 may be carried out by any other normally conceivable method; It is necessary to take into account that there are no steps.

In order to apply electrical energy to the ejection energy generating element 3, electrode layers 11 and 12 are provided on the inside and outside of the converter layer, respectively. In this embodiment, the inner electrode layer 11 is a converter layer. At the rear end of the body layer 10, the body layer 10 is folded back outward as shown in the figure, and a lead electrode 14 is attached to this portion by a conventional method. The electrode layer 11 and the electrode layer 12 are insulated from each other by an insulating portion 15, and a lead electrode 13 is attached to the electrode layer 12 near the insulating portion 15 in the same manner as described above. Since the above electrode layer comes into contact with ink, it is preferable to form it from metals with high ink resistance, such as Au (gold) and Pt (platinum).
jl, Ta.

Ti, Zr, Hf, V, Nb, Mg, Si.

Conductors such as Mo, W, Y, and La may also be used.

In the above configuration, when ink is supplied from the ink supply pipe 19 and ejection pulses are applied from the drive device (not shown) via the lead electrodes 13.14, the converter is The layer 10 is deformed and the ink within the ejection energy generating element 3 is ejected from the orifice 6.

At this time, the mechanical energy generated by the converter layer 10 is not transmitted through the adhesive layer or the nozzle member 2 as in the conventional example, but is directly transmitted to the ink in the tube through only a very thin electrode layer. Since the energy is transmitted, the energy transmission speed is high and energy loss is small, making it efficient. Therefore, the problem of allowance or high-speed recording as described in the conventional example section can be solved, and ink can be ejected using smaller input pulses, making it easier to downsize the entire apparatus.

Moreover, since there are no steps in the liquid flow path that would obstruct the flow of liquid, air bubbles attached to the inner wall of the liquid flow path can be easily removed by performing a recovery operation, ensuring stable discharge at all times. becomes possible.

Moreover, according to the above configuration, the droplet ejecting device can be constructed easily and inexpensively with fewer parts than the conventional example, and the manufacturing process can be simplified, so that it is suitable for reducing the cost of the entire device 4.

Of course, the above configuration is not limited to the recording head of an inkjet printer, and can be applied to other types of droplet ejection.

[Effect] As is clear from the above description, according to the present invention, in a droplet ejection device that ejects liquid supplied into a nozzle member by an ejection energy generation element, the ejection energy generation element and the nozzle member are connected to each other. To provide an excellent droplet ejecting device that can perform efficient droplet ejection under desired conditions with a simple and inexpensive structure because it adopts an integrally formed structure, and can downsize the entire device adopted. be able to.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a droplet ejection device used in a conventional inkjet printer, and FIG. 2 is a sectional view illustrating an embodiment of the droplet ejection device of the present invention. 1... Droplet discharge device 2... Nozzle member 3... Discharge energy generating element 6... Orifice IO... Converter layer 11.12.
...Electrode layer 13.14...Lead electrode 19...Ink supply tube 20...Adhesive Fig. 1

Claims (1)

[Claims] In a droplet ejection device that ejects liquid supplied into a nozzle member as flying droplets from an oriice by driving an ejection energy generator, the ejection energy generator and the nozzle member are an integrated structure, , and a supply pipe for supplying liquid is connected to the liquid supply side of the structure, and the inner wall surface of the supply pipe is substantially connected to the inner wall surface of the structure and the sliding can. A droplet ejection device characterized by: