JPS587363A - Ink jet head - Google Patents

Abstract

PURPOSE:To obtain liquid drops having substantially the same grain diameters and the same speeds from respective nozzle by a method wherein the acoustic resistances and inertances for respective nozzles are set substantially the same and the acoustic resistances and the inertances for ink supply paths are set also substantially the same. CONSTITUTION:The acoustic resistances rN and the inertances mN for the nozzles are set substantially the same in respective ink flow path series while the acoustic resistances rs and the inertances ms for the ink supply paths are set substantially the same, in order to obtain substantially the same volumetric speed UN in respective nozzles. If the volumetric speed UN of the nozzles are the same, the liquid drops having substantially the same grain diameters and the same speeds may be obtained from respective nozzles with respect to constant inputs phi impressed to respective pressure generating mechanisms.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of an inkjet head having multiple nozzles.

In an inkjet head with multiple nozzles, applying a constant input to each pressure generating mechanism to obtain droplets of approximately the same size and speed from each nozzle is essential for improving and stabilizing print quality. There is no condition. To this end, by making all the ink flow paths exactly the same, it is possible to obtain droplets with approximately the same particle size and the same velocity with respect to a certain compensation input applied to each pressure generating mechanism. However, it is difficult to make the shape of the ink flow path the same throughout the head due to the shape and size of the head, and the spacing between each nozzle which is limited by the dot spacing for maintaining print quality.

In the present invention, by setting an appropriate cross-sectional shape of the ink flow paths in each of the ink flow paths having unequal lengths, it is possible to produce approximately the same amount of particles from each nozzle in response to a constant input applied to each pressure generation mechanism. The aim is to obtain droplets with the same diameter and velocity.

The present invention will be explained based on the drawings.

Figure 1 shows the mechanism of one ink flow path system, with the ink tank 5
A pressure chamber 2 and a nozzle 1 are filled with ink through an ink supply path 4, and the ink in the pressure chamber 2 is pressurized at a desired timing by a diaphragm 3 and a pressurizing means (not shown). Ink droplets are ejected from nozzle 1. Ink channel 6
is formed by a system from the ink tank 5 to the nozzle 1.

FIG. 2 is an equivalent acoustic circuit of the ink flow path shown in FIG. (For the equivalent acoustic circuit, refer to Chapter 5 of "Introduction to Electroacoustic Engineering"author's material aS, publisher Shokodo Co., Ltd.) Figure 3 shows the acoustic capacity at (m'/N) of the ink tank, the nozzle acoustic capacitance ON, and acoustic capacitance a- of the ink supply path
is a simplified equivalent sound I that is considered to be sufficiently large that it can be ignored.
There are 11 circuits. As shown in the third WJ, the pressure generated in the pressure chamber by the input ψ applied to the pressure generation mechanism is
The ink is propagated through the nozzle at a volume velocity gw [-1/s] and through the ink supply path at a volume velocity UI.

In order to obtain droplets with approximately the same diameter and the same velocity from each nozzle for a constant input applied to each pressure generation mechanism, it is sufficient that the volume velocity U)l of the nozzles is the same. The ink that propagates through the nozzle at a speed of υ ejects from the nozzle and forms droplets.

According to the equivalent acoustic circuit shown in FIG.
s/m') Nozzle inertance m w (IF 7m
It is clear that it is sufficient to set the acoustic resistance (r) of the ink supply path and the inertance (8) of the ink supply path to be approximately the same.

Assuming that the ink flow path is a tube with a rectangular cross section, the acoustic resistance r is approximately A (-) in the vertical direction and 1 [in the horizontal direction] of the rectangular cross section.
It is given by equation (1) with -1 pipe length as L(-1).

r=11・L(A4-B)”/(A”-B”)・
--- (1) However, R8 is a constant.

Also, inertance is approximately given by formula (2) considering the same way.

Otori-R,・L/(Mu・B)・・・・−・・・
...(2) However, R3 is a constant.

In this way, the acoustic resistance r and the inertance are values determined by the length and width of the rectangular cross section and the pipe length.

Figure 4 shows the arrangement of ink channels with four nozzles as an example of a multi-nozzle inkjet head, but due to the arrangement, it is difficult to make the ink channels the same length.
In order to obtain droplets with the same particle size and the same speed, (1)
From formula (2), by changing the vertical width and width B of the cross section of the ink flow path, set the nozzle acoustic resistance rW and nozzle inertance so that they are almost the same across the four nozzles,
Similarly, the acoustic resistance r- and the inertance m- of the ink supply path can be made almost the same over all the ink supply paths.

In other words, taking a nozzle as an example, if the length of the nozzle is short, and if the nozzle depth is the same, narrowing the width will result in approximately the same acoustic resistance rl and inertance w.
On the other hand, if the length of the nozzle is long, by increasing the width, it is possible to obtain approximately the same acoustic resistance (r) and inertance (m).

With this setting, if a constant input is applied to each pressure generation mechanism in each ink flow path, ink will propagate to each nozzle at a volume velocity Ul, and the particles will have approximately the same particle size and the same velocity. Droplets are obtained and become available. In addition, since the acoustic resistance and inertance of each ink flow path are set to be almost the same,
Regardless of the constant coefficients appearing in equations (1) and (2), (1
) and (2) hold true.

Generally, this constant R8 depends on the viscosity of the ink, so it will change as the temperature changes, but because it is set this way, even if the viscosity changes due to temperature changes or ink evaporation, There is no variation in the ink droplets obtained from each nozzle, and stable ink droplets can be obtained. Moreover, even if the ink is changed, a stable product can be obtained without any effect.

As explained above, the ink flow path is analyzed based on the equivalent acoustic circuit, and the acoustic resistance rl and inertance ff1ll are set to be almost the same for each nozzle, and the ink supply path is also set to have the same acoustic resistance rs and inertance. By making 11111 approximately the same, droplets of approximately the same size and speed can be obtained from each nozzle in response to a certain input, improving print quality and increasing the stability of the inkjet head. effective.

[Brief explanation of drawings]

FIG. 1 is a sectional view of one ink flow path system, FIGS. 2 and 5 are equivalent acoustic circuit diagrams of the ink flow path system in FIG.
The figure is a layout diagram of ink supply channels of a multi-nozzle inkjet head showing an embodiment of the present invention. 1... Nozzle 2... Pressure chamber 3... Vibration plate 4... Ink supply path 5... Ink tank 6...・・・
Ink flow 1IO0... Acoustic capacity in the diaphragm! lI. ...Inertance r0 in the diaphragm
...Acoustic resistance in the diaphragm is 0te...
Acoustic capacity of the tank ψ・・・・・・External input or more Applicant Shinshu Seiki Co., Ltd. Zensha Co., Ltd. Kinsha Suwa Seikosha Figure 2 Figure 4 Procedural amendment (voluntary) 561127 July 1939 Commissioner of the Japan Patent Office 1, Indication of the case, Patent Application No. 1080I of 1982, 2 Name of the invention, Interjet Head 3, Person making the amendment 4, Agent I! L7 Specification subject to amendment q Contents of amendment Attachment copy p + Written by Masaru Yorune (spontaneous) L11 Details - S line from the top - ``Eldest son's cross section O length and width'' is replaced with ``shape of # side'' Nail 〇λ Similarly, in the S line from you, the phrase ``Then, narrow the width'' is corrected to ``Then, cho (also narrows a part of the width.'')〇5 Meat 5j1 Bottom line ``Long ones There is a meeting that says, ``Expand your horizons.''
At least 4-4-5o wide” and corrected 〇 or more

Claims (1)

[Claims] In a multi-nozzle type inkjet head, which is composed of a nozzle, a pressure chamber, an ink supply path, a diaphragm, and a pressurizing means, and has at least two or more different lengths of ink flow paths, each Nozzle acoustic m resistance r1.
The cross-sectional shape of each nozzle and the cross-sectional shape of the ink supply path are set so that the inertance is the same, and the acoustic resistance rs and inertance l111 of each ink supply path are the same. inkjet head.