JPS6027572B2 - ink droplet ejector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ink droplet ejecting device used in a so-called inkjet printer that performs recording by ejecting droplets of ink, etc. In particular, the present invention relates to an ink droplet ejecting device used in a so-called inkjet printer device that performs recording by ejecting droplets of ink or the like. In multi-nozzles arranged in one row, droplet diameter and jetting timing can be made uniform to enable jetting.

A secondary method of printing by arranging a large number of nozzles in at least one line and feeding recording paper at right angles to this is shown in Japanese Patent Publication No. 41-16973, Jiko Sho 49-284 & Samurai Kaisho 48-19622, etc. There is.

In such multi-nozzle printing, there is no mechanical movement of the print head and a large number of droplets are ejected per unit time, so high-speed printing is possible.

In either method, in order to obtain good print quality, the diameter of the ink droplets and the timing of ejection must be uniform across all nozzles. However, in the method of ejecting with high water pressure, mechanical vibrations are applied to the nozzle by an ultrasonic vibrator, and the timing is determined as a compressional wave within the ink. The drawback is that it is difficult to achieve uniform diameter and injection timing. In addition, the pressure pulse type system has the disadvantage that it is difficult to manufacture because the injection port of each nozzle and the pressure generating means are connected by complicated piping. An object of the present invention is to improve the uniformity of ink droplet diameter and jetting timing in an ink droplet ejection device mainly used in multi-nozzle inkjet printers, and to provide an easy-to-manufacture device.

The present invention is characterized in that a piezoelectric element divided into small pieces is adhered to a single elastic plate such as metal to form a laminate, and a voltage is applied to the piezoelectric element to deform the laminate, and this is used as a pressure increase device. It has characteristics.

The present invention can be applied to a so-called pressure pulse type inkjet device as disclosed in Tokkoku Sho 48-9622.

First, the structure of the conventional pressure pulse type inkjet device is
This will be briefly explained with reference to FIG. The liquid chamber has two parts,
namely, an outer chamber 2 adjoining the nozzle 1 and directly connected to an inlet passage 5 connected to an ink tank (not shown), and an inner chamber 3 adjoining a device 6 for producing a pressure increase. It is divided into. These two chambers 2, 3 are connected to each other via a connecting channel 4 which is in line with the nozzle. An embodiment of the present invention will be explained with reference to FIG.

The outer chamber 21 is connected to the inner chamber 22 via a connecting channel 23 . The pressure generating device 24 consists of a single elastic plate 25 made of stainless steel or the like that covers the inner chamber 22, and piezoelectric elements 26a, b, c, . . . that are separately bonded thereon. Details of the pressure generator 24 will be explained with reference to FIG. FIG. 3a is a plan view of the pressure generating device 24, and FIG. 3b is a sectional view taken along the line B--B. Each piezoelectric element 26a, b, c... is a large number of small pieces divided in the longitudinal direction of a rectangular elastic plate, and the farthest side L of each element is at least three times the short side A and the thickness T. It is necessary. The dimension of the long side L is determined depending on the volume of the inner liquid chamber necessary for ink jetting and the number of jet nozzles. The area around the pressure generating device 24, which is made up of piezoelectric elements 26a, b, c... and an elastic plate 25 to which these are bonded, is as follows:
It is bonded to a substrate 28 that forms a liquid chamber. Piezoelectric element 2
When a voltage is applied to 6a, b, c..., each piezoelectric element contracts in the direction of the long side L, and since both ends are fixed, the elastic plate 25 is moved into the liquid chamber as shown in Fig. 4. Make it stick out towards the target. If we look at each of the Shoden elements individually, the Shoden elements 26a, 26
b etc. contract in the L direction, while also slightly deforming in the short side A direction. However, now it is set large for A,
In addition, since the elastic plate 25 is not fixed in the A direction except for both ends of the liquid chamber, the entire laminate is slightly wavy in the short side A direction and curved in the long side L direction. Become. Since the length from the pressure generator 24 to the coupling passage 23 is shorter than the wavelength of the ultrasonic waves mentioned above, the undulating deformation described above causes uneven pressure on the ink liquid. Must not be. In any case, the undulation in the A direction is slight and is not an important factor when designing the liquid chamber. Returning to FIG. 2, the inner chamber 22 is elongated in accordance with the number of coupling passages 23 provided opposite the nozzles 27.

What is important about the outer chamber 21 with the nozzle 27 is that
When no pressure is applied to the ink in the inner chamber 22 by the pressure generator 24 and a full ink is not ejected, negative hydrostatic pressure is applied at the nozzle outlet, and the liquid level (meniscus) of the ink becomes a concave surface. That is what we are doing. Therefore, one possible method is to arrange the ink tank below the nozzle 27. If the meniscus were concave - ie, subject to positive hydrostatic pressure, then the meniscus would be convex, causing ink to gradually ooze out when ink is not being ejected. If left unattended, the oozing ink will dry and solidify, clogging the nozzles and seriously affecting the reliability of the inkjet device. As described above, in the present invention, the chambers 21, 2
Since a uniform pressure can be applied to the ink in the nozzle 2, ink droplets of the same diameter can be ejected at uniform timing from all the nozzles 27 connected thereto.

The present invention can also be applied to a device that uses high water pressure to continuously eject ink to improve the accuracy of the timing at which ink is separated from a liquid column into a liquid bottle during ejection.

FIG. 5 shows an example thereof. Ink enters the outer chamber 45 from the Sekiguchi 41 side, and enters the nozzle 42 provided on the opposite side.
erupts from. A pressure generating device 43 and a connecting passage (or inner chamber) 44 are provided at right angles to the chamber 45 . The pressure generator pupil 43 has the same structure and function as described in the previous embodiment, and applies periodic pressure to the ink within the outer chamber 45.
Since this pressure is applied uniformly over all the passages leading to the large number of nozzles 42, the amount of ink ejected from each nozzle can be uniformly separated, making the shape of the droplets uniform, and separating the ink into droplets. The timing accuracy can be improved. As described above, in the present invention, pressure can be applied directly to the nozzle or to a part of the outer chamber (ink passage) connected to the nozzle, so that the ink ejected from the many nozzles arranged in a row can be filled with ink. Uniform size and timing. Furthermore, even if the lengths of the nozzles and ink passages are changed, the ink drop ejecting device can be easily manufactured without impairing the uniformity of pressure generation. Note that in the present invention, it is clear that an element that expands and contracts by the application of an electric signal, such as an electrostrictive or magnetostrictive element, can be used instead of the compression box element, and the term piezoelectric element in this specification refers to all of these elements. shall be construed as including.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a secondary ink droplet ejecting device, FIG. 2 is a perspective view of an embodiment of the present invention, FIG. 3 is a plan view and a sectional view of a pressure generating means according to the present invention, and FIG. 4 5 is a side view showing a curved state of the pressure increase device, and FIG. 5 is a perspective view of another embodiment of the present invention. 21... Outer chamber, 22... Inner chamber, 23... Connection passage, 24... Pressure increase device, 25... Elastic plate, 2
6... Piezoelectric element, 27... Nozzle. Figure 1 Tsutomu Figure 2 Figure 3 and Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. A plurality of nozzles arranged in at least one row, an outer chamber that includes one chamber common to each of the nozzles and communicates with an ink tank, and communicates with the outer chamber. An ink droplet ejecting device comprising: an inner chamber in which the inner chamber is heated, and a pressure generating device that continuously applies a pressure change to the ink in the inner chamber, thereby ejecting ink droplets from each nozzle simultaneously;
a rectangular elastic plate in which the pressure generating device constitutes a part of the inner chamber and has long sides aligned in the direction in which the nozzles are arranged, and a side of the rectangular elastic plate opposite to the inner chamber; An ink droplet ejecting device comprising a plurality of piezoelectric elements adhered to a surface of the rectangular elastic plate and divided into small pieces in the longitudinal direction of the rectangular elastic plate. 2. The ink droplet ejecting device according to claim 1, wherein the inner chamber includes one chamber common to each nozzle.